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Mast TD, Johnstone DA, Dumoulin CL, Lamba MA, Patch SK. Reconstruction of thermoacoustic emission sources induced by proton irradiation using numerical time reversal. Phys Med Biol 2023; 68:10.1088/1361-6560/acabfc. [PMID: 36595327 PMCID: PMC9976196 DOI: 10.1088/1361-6560/acabfc] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2022] [Accepted: 12/15/2022] [Indexed: 12/23/2022]
Abstract
Objective.Mapping of dose delivery in proton beam therapy can potentially be performed by analyzing thermoacoustic emissions measured by ultrasound arrays. Here, a method is derived and demonstrated for spatial mapping of thermoacoustic sources using numerical time reversal, simulating re-transmission of measured emissions into the medium.Approach.Spatial distributions of thermoacoustic emission sources are shown to be approximated by the analytic-signal form of the time-reversed acoustic field, evaluated at the time of the initial proton pulse. Given calibration of the array sensitivity and knowledge of tissue properties, this approach approximately reconstructs the acoustic source amplitude, equal to the product of the time derivative of the radiation dose rate, mass density, and Grüneisen parameter. This approach was implemented using two models for acoustic fields of the array elements, one modeling elements as line sources and the other as rectangular radiators. Thermoacoustic source reconstructions employed previously reported measurements of emissions from proton energy deposition in tissue-mimicking phantoms. For a phantom incorporating a bone layer, reconstructions accounted for the higher sound speed in bone. Dependence of reconstruction quality on array aperture size and signal-to-noise ratio was consistent with previous acoustic simulation studies.Main results.Thermoacoustic source distributions were successfully reconstructed from acoustic emissions measured by a linear ultrasound array. Spatial resolution of reconstructions was significantly improved in the azimuthal (array) direction by incorporation of array element diffraction. Source localization agreed well with Monte Carlo simulations of energy deposition, and was improved by incorporating effects of inhomogeneous sound speed.Significance.The presented numerical time reversal approach reconstructs thermoacoustic sources from proton beam radiation, based on straightforward processing of acoustic emissions measured by ultrasound arrays. This approach may be useful for ranging and dosimetry of clinical proton beams, if acoustic emissions of sufficient amplitude and bandwidth can be generated by therapeutic proton sources.
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Affiliation(s)
- T Douglas Mast
- Biomedical Engineering, University of Cincinnati, United States of America
| | - David A Johnstone
- Radiation Oncology, University of Cincinnati, United States of America
| | - Charles L Dumoulin
- Radiology, Cincinnati Children's Hospital Medical Center, United States of America
| | - Michael A Lamba
- Radiation Oncology, University of Cincinnati, United States of America
| | - Sarah K Patch
- Acoustic Range Estimates, Chicago, Illinois, United States of America
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Pratt RG, Lee G, McAllister AS, Smith DR, Myer GD, Ireland CM, Loew WM, Lanier M, Wang H, Diekfuss JA, Yuan W, Dumoulin CL. A Weighted Head Accelerator Mechanism (WHAM) for visualizing brain rheology using magnetic resonance imaging. J Neurosci Methods 2022; 382:109728. [PMID: 36244524 DOI: 10.1016/j.jneumeth.2022.109728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 09/16/2022] [Accepted: 10/10/2022] [Indexed: 01/05/2023]
Abstract
BACKGROUND A device for moving the head during MR imaging, called a Weighted Head Accelerator Mechanism (WHAM), rotates the head of a supine subject within programmable rotation limits and acceleration profiles. The WHAM can be used with custom MRI sequences to visualize the deformation and recoil of in vivo brain parenchyma with high temporal resolution, allowing element-wise calculation of strain and shear forces in the brain. Unlike previous devices, the WHAM can be configured to provide a wide range of motion and acceleration profiles. NEW METHOD The WHAM was calibrated using a high-speed camera on a laboratory bench and in 1.5 Tesla and 3.0 Tesla MRI scanners using gel phantoms and human subjects. The MR imaging studies employed a spatial spin-saturation tagging sub-sequence, followed by serial image acquisition. In these studies, 256 images were acquired with a temporal resolution of 2.56 ms. Deformation of the brain was quantified by following the spatial tags in the images. RESULTS MR imaging showed that the WHAM drove quantifiable brain motions using g forces less than those typically observed in day-to-day activities, with peak accelerations of ∼250 rad/sec2. COMPARISON WITH EXISTING METHODS The peak pre-contact accelerations and velocities achieved by the WHAM device in this study are both higher than devices used in previous studies, while also allowing for modification of these factors. CONCLUSIONS MR imaging performed with the WHAM provides a direct method to visualize and quantify "brain slosh" in response to rotational acceleration. Consequently, this approach might find utility in evaluating strategies to protect the brain from mild traumatic brain injury (mTBI).
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Affiliation(s)
- Ronald G Pratt
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | | | - Aaron S McAllister
- Department of Radiology, Nationwide Children's Hospital, Columbus, OH, USA
| | - Daniel R Smith
- Emory Sports Performance And Research Center (SPARC), Flowery Branch, GA, USA; Emory Sports Medicine Center, Atlanta, GA, USA; Department of Orthopaedics, Emory University School of Medicine, Atlanta, GA, USA
| | - Gregory D Myer
- Emory Sports Performance And Research Center (SPARC), Flowery Branch, GA, USA; Emory Sports Medicine Center, Atlanta, GA, USA; Department of Orthopaedics, Emory University School of Medicine, Atlanta, GA, USA; The Micheli Center for Sports Injury Prevention, Waltham, MA, USA.
| | - Christopher M Ireland
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Biomedical Engineering, University of Cincinnati, Cincinnati, OH, USA
| | - Wolfgang M Loew
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, University of Cincinnati, College of Medicine, Cincinnati, OH, USA
| | - Matt Lanier
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Hui Wang
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Philips Healthcare, Cincinnati, OH, USA
| | - Jed A Diekfuss
- Emory Sports Performance And Research Center (SPARC), Flowery Branch, GA, USA; Emory Sports Medicine Center, Atlanta, GA, USA; Department of Orthopaedics, Emory University School of Medicine, Atlanta, GA, USA
| | - Weihong Yuan
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, University of Cincinnati, College of Medicine, Cincinnati, OH, USA
| | - Charles L Dumoulin
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, University of Cincinnati, College of Medicine, Cincinnati, OH, USA
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Schmidt EJ, Olson G, Tokuda J, Alipour A, Watkins RD, Meyer EM, Elahi H, Stevenson WG, Schweitzer J, Dumoulin CL, Johnson T, Kolandaivelu A, Loew W, Halperin HR. Intracardiac MR imaging (ICMRI) guiding-sheath with amplified expandable-tip imaging and MR-tracking for navigation and arrythmia ablation monitoring: Swine testing at 1.5 and 3T. Magn Reson Med 2022; 87:2885-2900. [PMID: 35142398 PMCID: PMC8957513 DOI: 10.1002/mrm.29168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 11/30/2021] [Accepted: 01/05/2022] [Indexed: 12/15/2022]
Abstract
PURPOSE Develop a deflectable intracardiac MR imaging (ICMRI) guiding-sheath to accelerate imaging during MR-guided electrophysiological (EP) interventions for radiofrequency (500 kHz) ablation (RFA) of arrythmia. Requirements include imaging at three to five times surface-coil SNR in cardiac chambers, vascular insertion, steerable-active-navigation into cardiac chambers, operation with ablation catheters, and safe levels of MR-induced heating. METHODS ICMRI's 6 mm outer-diameter (OD) metallic-braided shaft had a 2.6 mm OD internal lumen for ablation-catheter insertion. Miniature-Baluns (MBaluns) on ICMRI's 1 m shaft reduced body-coil-induced heating. Distal section was a folded "star"-shaped imaging-coil mounted on an expandable frame, with an integrated miniature low-noise-amplifier overcoming cable losses. A handle-activated movable-shaft expanded imaging-coil to 35 mm OD for imaging within cardiac-chambers. Four MR-tracking micro-coils enabled navigation and motion-compensation, assuming a tetrahedron-shape when expanded. A second handle-lever enabled distal-tip deflection. ICMRI with a protruding deflectable EP catheter were used for MR-tracked navigation and RFA using a dedicated 3D-slicer user-interface. ICMRI was tested at 3T and 1.5T in swine to evaluate (a) heating, (b) cardiac-chamber access, (c) imaging field-of-view and SNR, and (d) intraprocedural RFA lesion monitoring. RESULTS The 3T and 1.5T imaging SNR demonstrated >400% SNR boost over a 4 × 4 × 4 cm3 FOV in the heart, relative to body and spine arrays. ICMRI with MBaluns met ASTM/IEC heating limits during navigation. Tip-deflection allowed navigating ICMRI and EP catheter into atria and ventricles. Acute-lesion long-inversion-time-T1-weighted 3D-imaging (TWILITE) ablation-monitoring using ICMRI required 5:30 min, half the time needed with surface arrays alone. CONCLUSION ICMRI assisted EP-catheter navigation to difficult targets and accelerated RFA monitoring.
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Affiliation(s)
- Ehud J. Schmidt
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | - Gregory Olson
- Cardiac Arrhythmia and Heart Failure DivisionAbbott LaboratoriesMinnetonkaMinnesotaUSA
| | - Junichi Tokuda
- RadiologyBrigham and Women’s HospitalBostonMassachusettsUSA
| | - Akbar Alipour
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | | | - Eric M. Meyer
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | - Hassan Elahi
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | | | - Jeffrey Schweitzer
- Cardiac Arrhythmia and Heart Failure DivisionAbbott LaboratoriesMinnetonkaMinnesotaUSA
| | | | | | | | - Wolfgang Loew
- RadiologyCincinnati Children’s Hospital Medical CenterCincinnatiOhioUSA
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Xiao Q, Stewart NJ, Willmering MM, Gunatilaka CC, Thomen RP, Schuh A, Krishnamoorthy G, Wang H, Amin RS, Dumoulin CL, Woods JC, Bates AJ. Human upper-airway respiratory airflow: In vivo comparison of computational fluid dynamics simulations and hyperpolarized 129Xe phase contrast MRI velocimetry. PLoS One 2021; 16:e0256460. [PMID: 34411195 PMCID: PMC8376109 DOI: 10.1371/journal.pone.0256460] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 08/08/2021] [Indexed: 11/18/2022] Open
Abstract
Computational fluid dynamics (CFD) simulations of respiratory airflow have the potential to change the clinical assessment of regional airway function in health and disease, in pulmonary medicine and otolaryngology. For example, in diseases where multiple sites of airway obstruction occur, such as obstructive sleep apnea (OSA), CFD simulations can identify which sites of obstruction contribute most to airway resistance and may therefore be candidate sites for airway surgery. The main barrier to clinical uptake of respiratory CFD to date has been the difficulty in validating CFD results against a clinical gold standard. Invasive instrumentation of the upper airway to measure respiratory airflow velocity or pressure can disrupt the airflow and alter the subject's natural breathing patterns. Therefore, in this study, we instead propose phase contrast (PC) velocimetry magnetic resonance imaging (MRI) of inhaled hyperpolarized 129Xe gas as a non-invasive reference to which airflow velocities calculated via CFD can be compared. To that end, we performed subject-specific CFD simulations in airway models derived from 1H MRI, and using respiratory flowrate measurements acquired synchronously with MRI. Airflow velocity vectors calculated by CFD simulations were then qualitatively and quantitatively compared to velocity maps derived from PC velocimetry MRI of inhaled hyperpolarized 129Xe gas. The results show both techniques produce similar spatial distributions of high velocity regions in the anterior-posterior and foot-head directions, indicating good qualitative agreement. Statistically significant correlations and low Bland-Altman bias between the local velocity values produced by the two techniques indicates quantitative agreement. This preliminary in vivo comparison of respiratory airway CFD and PC MRI of hyperpolarized 129Xe gas demonstrates the feasibility of PC MRI as a technique to validate respiratory CFD and forms the basis for further comprehensive validation studies. This study is therefore a first step in the pathway towards clinical adoption of respiratory CFD.
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Affiliation(s)
- Qiwei Xiao
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
| | - Neil J. Stewart
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Infection, Immunity & Cardiovascular Disease, POLARIS Group, Imaging Sciences, University of Sheffield, Sheffield, United Kingdom
| | - Matthew M. Willmering
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
| | - Chamindu C. Gunatilaka
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
| | - Robert P. Thomen
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Pulmonary Imaging Research Laboratory, University of Missouri School of Medicine, Columbia, Missouri, United States of America
| | - Andreas Schuh
- Department of Computing, Imperial College London, London, United Kingdom
| | | | - Hui Wang
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- MR Clinical Science, Philips, Cincinnati, OH, United States of America
| | - Raouf S. Amin
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, OH, United States of America
| | - Charles L. Dumoulin
- Department of Radiology, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Jason C. Woods
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, OH, United States of America
- Department of Radiology, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Alister J. Bates
- Division of Pulmonary Medicine, Center for Pulmonary Imaging Research, Cincinnati Children’s Hospital, Cincinnati, OH, United States of America
- Department of Pediatrics, University of Cincinnati School of Medicine, Cincinnati, OH, United States of America
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Primrose CW, Hecht EM, Roditi G, François CJ, Maki JH, Dumoulin CL, DeMarco JK, Douglas P. MR Angiography Series: Fundamentals of Contrast-enhanced MR Angiography. Radiographics 2021; 41:E138-E139. [PMID: 34197248 DOI: 10.1148/rg.2021200215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The Society for Magnetic Resonance Angiography (SMRA) is a group of researchers and clinicians who are passionate about the benefits of MR angiography (MRA) but understand its challenges. Their mission is to study MRA, continually improve and innovate for the benefit of patients, and most important, educate the medical community so they can take full advantage of the benefits of MRA and overcome its challenges. In support of that mission, the authors have created a series of self-learning modules on behalf of the SMRA to demystify MRA protocols and help the reader perform patient-friendly high-quality MRA on a routine basis in clinical practice. The full digital presentation is available online. ©RSNA, 2021.
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Affiliation(s)
- Colin W Primrose
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Elizabeth M Hecht
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Giles Roditi
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Christopher J François
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Jeffrey H Maki
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Charles L Dumoulin
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - J Kevin DeMarco
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
| | - Peter Douglas
- From the Department of Radiology, NHS Greater Glasgow and Clyde, Queen Elizabeth University Hospital, First Floor, 1345 Govan Rd, Glasgow, G51 4TF, Scotland (C.W.P., G.R., P.D.); Department of Radiology, Weill Cornell Medicine, New York, NY (E.M.H.); Institute of Cardiovascular and Medical Sciences (G.R.) and School of Medicine, Dentistry and Nursing (P.D.), University of Glasgow, Glasgow, Scotland; Department of Radiology and School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wis (C.J.F.); Department of Radiology, University of Colorado Anschutz Medical Campus, Denver, Colo (J.H.M.); Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio (C.L.D.); and Walter Reed National Military Medical Center and Uniformed Services University of the Health Sciences, Bethesda, Md (J.K.D.)
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Wang H, Pednekar A, Tkach JA, Bridgewater KR, Trout AT, Dillman JR, Dumoulin CL. Fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths MR elastography. Magn Reson Med 2020; 85:1552-1560. [PMID: 32936497 DOI: 10.1002/mrm.28488] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 07/21/2020] [Accepted: 08/03/2020] [Indexed: 12/15/2022]
Abstract
PURPOSE To design a new 2D gradient recalled echo MR elastography (MRE) pulse sequence with inflow saturation for measuring liver stiffness in half the breath-hold time compared to standard of care (SC) 2D GRE MRE sequences. METHODS FASTWALTZ (fusing acceleration and saturation techniques with wave amplitude labeling of time-shifted zeniths) MRE employs an interleaved dual TR strategy with wave amplitude labeling and compressed SENSE undersampling to reduce breath-hold time while incorporating inflow saturation to suppress flow artifacts. The sequence was implemented and compared with SC MRE both in phantoms and in vivo in 5 asymptomatic volunteers. Stiffness values, region of interest size, and breath-hold times were compared between sequences. RESULTS Stiffness values were comparable between FASTWALTZ and SC MRE for both phantoms and in-vivo data. In volunteers, the group mean stiffness values at 60 Hz and region of interest size were 1.96 ± 0.30 kilopascals and 2279 ± 516 mm2 for SC MRE, and 1.95 ± 0.29 kilopascals and 2061 ± 464 mm2 for FASTWALTZ. Breath-hold duration for FASTWALTZ was 6.3 s compared to 13.3 s for SC MRE. CONCLUSION FASTWALTZ provides comparable stiffness values in half the breath-hold time compared to SC MRE and may have clinical benefits in patients with limited breath-holding capacity.
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Affiliation(s)
- Hui Wang
- MR Clinical Science, Philips, Cincinnati, Ohio, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Amol Pednekar
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Jean A Tkach
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Kaley R Bridgewater
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Andrew T Trout
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Jonathan R Dillman
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
| | - Charles L Dumoulin
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA.,Department of Radiology, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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7
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Alipour A, Meyer ES, Dumoulin CL, Watkins RD, Elahi H, Loew W, Schweitzer J, Olson G, Chen Y, Tao S, Guttman M, Kolandaivelu A, Halperin HR, Schmidt EJ. MRI Conditional Actively Tracked Metallic Electrophysiology Catheters and Guidewires With Miniature Tethered Radio-Frequency Traps: Theory, Design, and Validation. IEEE Trans Biomed Eng 2019; 67:1616-1627. [PMID: 31535979 DOI: 10.1109/tbme.2019.2941460] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Cardiovascular interventional devices typically have long metallic braids or backbones to aid in steerability and pushability. However, electromagnetic coupling of metallic-based cardiovascular interventional devices with the radiofrequency (RF) fields present during Magnetic Resonance Imaging (MRI) can make a device unsafe for use in an MRI scanner. We aimed to develop MRI conditional actively-tracked cardiovascular interventional devices by sufficiently attenuating induced currents on the metallic braid/tube and internal-cabling using miniaturized resonant floating RF traps (MBaluns). METHOD MBaluns were designed for placement at multiple locations along a conducting cardiovascular device to prevent the establishment of standing waves and to dissipate RF-induced energy. The MBaluns were constructed with loosely-wound solenoids to be sensitive to transverse magnetic fields created by both surface currents on the device's metallic backbone and common-mode currents on internal cables. Electromagnetic simulations were used to optimize MBalun parameters. Following optimization, two different MBalun designs were applied to MR-actively-tracked metallic guidewires and metallic-braided electrophysiology ablation catheters. Control-devices were constructed without MBaluns. MBalun performance was validated using network-analyzer quantification of current attenuation, electromagnetic Specific-Absorption-Rate (SAR) analysis, thermal tests during high SAR pulse sequences, and MRI-guided cardiovascular navigation in swine. RESULTS Electromagnetic SAR simulations resulted in ≈20 dB attenuation at the tip of the wire using six successive MBaluns. Network-analyzer tests confirmed ∼17 dB/MBalun surface-current attenuation. Thermal tests indicated temperature decreases of 5.9 °C in the MBalun-equipped guidewire tip. Both devices allowed rapid vascular navigation resulting from good torquability and MR-Tracking visibility. CONCLUSION MBaluns increased device diameter by 20%, relative to conventional devices, providing a spatially-efficient means to prevent heating during MRI. SIGNIFICANCE MBaluns allow use of long metallic components, which improves mechanical performance in active MR-guided interventional devices.
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Bates AJ, Schuh A, Amine-Eddine G, McConnell K, Loew W, Fleck RJ, Woods JC, Dumoulin CL, Amin RS. Assessing the relationship between movement and airflow in the upper airway using computational fluid dynamics with motion determined from magnetic resonance imaging. Clin Biomech (Bristol, Avon) 2019; 66:88-96. [PMID: 29079097 DOI: 10.1016/j.clinbiomech.2017.10.011] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/05/2017] [Accepted: 10/10/2017] [Indexed: 02/07/2023]
Abstract
BACKGROUND Computational fluid dynamics simulations of respiratory airflow in the upper airway reveal clinically relevant information, including sites of local resistance, inhaled particle deposition, and the effect of pathological constrictions. Unlike previous simulations, which have been performed on rigid anatomical models from static medical imaging, this work utilises ciné imaging during respiration to create dynamic models and more closely represent airway physiology. METHODS Airway movement maps were obtained from non-rigid image registration of fast-cine MRI and applied to high-spatial-resolution airway surface models. Breathing flowrates were recorded simultaneously with imaging. These data formed the boundary conditions for large eddy simulation computations of the airflow from exterior mask to bronchi. Simulations with rigid geometries were performed to demonstrate the resulting airflow differences between airflow simulations in rigid and dynamic airways. FINDINGS In the analysed rapid breathing manoeuvre, incorporating airway movement significantly changed the findings of the CFD simulations. Peak resistance increased by 19.8% and occurred earlier in the breath. Overall pressure loss decreased by 19.2%, and the proportion of flow in the mouth increased by 13.0%. Airway wall motion was out-of-phase with the air pressure force, demonstrating the presence of neuromuscular motion. In total, the anatomy did 25.2% more work on the air than vice versa. INTERPRETATIONS Realistic movement of the airway is incorporated into CFD simulations of airflow in the upper airway for the first time. This motion is vital to producing clinically relevant computational models of respiratory airflow and will allow novel analysis of dynamic conditions, such as sleep apnoea.
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Affiliation(s)
- Alister J Bates
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Bioengineering, Imperial College London, UK.
| | - Andreas Schuh
- Department of Computing, Imperial College London, UK
| | | | - Keith McConnell
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Wolfgang Loew
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Robert J Fleck
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Jason C Woods
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Charles L Dumoulin
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA; Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Raouf S Amin
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
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9
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Niedbalski PJ, Willmering MM, Robertson SH, Freeman MS, Loew W, Giaquinto RO, Ireland C, Pratt RG, Dumoulin CL, Woods JC, Cleveland ZI. Mapping and correcting hyperpolarized magnetization decay with radial keyhole imaging. Magn Reson Med 2019; 82:367-376. [PMID: 30847967 DOI: 10.1002/mrm.27721] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 01/17/2019] [Accepted: 02/11/2019] [Indexed: 12/11/2022]
Abstract
PURPOSE Hyperpolarized (HP) media enable biomedical imaging applications that cannot be achieved with conventional MRI contrast agents. Unfortunately, quantifying HP images is challenging, because relaxation and radio-frequency pulsing generate spatially varying signal decay during acquisition. We demonstrate that, by combining center-out k-space sampling with postacquisition keyhole reconstruction, voxel-by-voxel maps of regional HP magnetization decay can be generated with no additional data collection. THEORY AND METHODS Digital phantom, HP 129 Xe phantom, and in vivo 129 Xe human (N = 4 healthy; N = 2 with cystic fibrosis) imaging was performed using radial sampling. Datasets were reconstructed using a postacquisition keyhole approach in which 2 temporally resolved images were created and used to generate maps of regional magnetization decay following a simple analytical model. RESULTS Mean, keyhole-derived decay terms showed excellent agreement with the decay used in simulations (R2 = 0.996) and with global attenuation terms in HP 129 Xe phantom imaging (R2 > 0.97). Mean regional decay from in vivo imaging agreed well with global decay values and displayed spatial heterogeneity that matched expected variations in flip angle and oxygen partial pressure. Moreover, these maps could be used to correct variable signal decay across the image volume. CONCLUSIONS We have demonstrated that center-out trajectories combined with keyhole reconstruction can be used to map regional HP signal decay and to quantitatively correct images. This approach may be used to improve the accuracy of quantitative measures obtained from hyperpolarized media. Although validated with gaseous HP 129 Xe in this work, this technique can be generalized to any hyperpolarized agent.
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Affiliation(s)
- Peter J Niedbalski
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Matthew M Willmering
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Scott H Robertson
- Clinical Imaging Physics Group, Department of Radiology, Duke University Medical Center, Durham, North Carolina
| | - Matthew S Freeman
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Wolfgang Loew
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Randy O Giaquinto
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Christopher Ireland
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio
| | - Ronald G Pratt
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Charles L Dumoulin
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Jason C Woods
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio
| | - Zackary I Cleveland
- Center for Pulmonary Imaging Research, Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.,Department of Biomedical Engineering, University of Cincinnati, Cincinnati, Ohio.,Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio
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10
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Wang H, Tkach JA, Trout AT, Dumoulin CL, Dillman JR. Respiratory-triggered spin-echo echo-planar imaging-based mr elastography for evaluating liver stiffness. J Magn Reson Imaging 2018; 50:391-396. [DOI: 10.1002/jmri.26610] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 11/22/2018] [Indexed: 01/22/2023] Open
Affiliation(s)
- Hui Wang
- MR Clinical Science; Philips; Cincinnati Ohio USA
- Department of Radiology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio USA
- Department of Radiology; University of Cincinnati College of Medicine; Cincinnati Ohio USA
| | - Jean A. Tkach
- Department of Radiology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio USA
- Department of Radiology; University of Cincinnati College of Medicine; Cincinnati Ohio USA
| | - Andrew T. Trout
- Department of Radiology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio USA
- Department of Radiology; University of Cincinnati College of Medicine; Cincinnati Ohio USA
| | - Charles L. Dumoulin
- Department of Radiology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio USA
- Department of Radiology; University of Cincinnati College of Medicine; Cincinnati Ohio USA
| | - Jonathan R. Dillman
- Department of Radiology; Cincinnati Children's Hospital Medical Center; Cincinnati Ohio USA
- Department of Radiology; University of Cincinnati College of Medicine; Cincinnati Ohio USA
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11
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Bates AJ, Schuh A, McConnell K, Williams BM, Lanier JM, Willmering MM, Woods JC, Fleck RJ, Dumoulin CL, Amin RS. A novel method to generate dynamic boundary conditions for airway CFD by mapping upper airway movement with non-rigid registration of dynamic and static MRI. Int J Numer Method Biomed Eng 2018; 34:e3144. [PMID: 30133165 DOI: 10.1002/cnm.3144] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2018] [Revised: 06/21/2018] [Accepted: 08/12/2018] [Indexed: 06/08/2023]
Abstract
Computational fluid dynamics (CFD) simulations of airflow in the human airways have the potential to provide a great deal of information that can aid clinicians in case management and surgical decision making, such as airway resistance, energy expenditure, airflow distribution, heat and moisture transfer, and particle deposition, as well as the change in each of these due to surgical interventions. However, the clinical relevance of CFD simulations has been limited to date, as previous models either did not incorporate neuromuscular motion or any motion at all. Many common airway pathologies, such as obstructive sleep apnea (OSA) and tracheomalacia, involve large movements of the structures surrounding the airway, such as the tongue and soft palate. Airway wall motion may be due to many factors including neuromuscular motion, internal aerodynamic forces, and external forces such as gravity. Therefore, to realistically model these airway diseases, a method is required to derive the airway wall motion, whatever the cause, and apply it as a boundary condition to CFD simulations. This paper presents and validates a novel method of capturing in vivo motion of airway walls from magnetic resonance images with high spatiotemporal resolution, through a novel combination of non-rigid image, surface, and surface-normal-vector registration. Coupled with image-synchronous pneumotachography, this technique provides the necessary boundary conditions for dynamic CFD simulations of breathing, allowing the effect of the airway's complex motion to be calculated for the first time, in both normal subjects and those with conditions such as OSA.
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Affiliation(s)
- Alister J Bates
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Bioengineering, Imperial College London, UK
| | - Andreas Schuh
- Department of Computing, Imperial College London, UK
| | - Keith McConnell
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Brynne M Williams
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - J Matthew Lanier
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Matthew M Willmering
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Jason C Woods
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, USA
- Departments of Radiology and Physics, University of Cincinnati, Cincinnati, OH, USA
| | - Robert J Fleck
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Radiology, University of Cincinnati, Cincinnati, OH, USA
| | - Charles L Dumoulin
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, USA
| | - Raouf S Amin
- Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
- Department of Pediatrics, University of Cincinnati, Cincinnati, OH, USA
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12
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de Arcos J, Schmidt EJ, Wang W, Tokuda J, Vij K, Seethamraju RT, Damato AL, Dumoulin CL, Cormack RA, Viswanathan AN. Prospective Clinical Implementation of a Novel Magnetic Resonance Tracking Device for Real-Time Brachytherapy Catheter Positioning. Int J Radiat Oncol Biol Phys 2017; 99:618-626. [PMID: 28843373 DOI: 10.1016/j.ijrobp.2017.05.054] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 05/05/2017] [Accepted: 05/31/2017] [Indexed: 10/19/2022]
Abstract
PURPOSE We designed and built dedicated active magnetic resonance (MR)-tracked (MRTR) stylets. We explored the role of MRTR in a prospective clinical trial. METHODS AND MATERIALS Eleven gynecologic cancer patients underwent MRTR to rapidly optimize interstitial catheter placement. MRTR catheter tip location and orientation were computed and overlaid on images displayed on in-room monitors at rates of 6 to 16 frames per second. Three modes of actively tracked navigation were analyzed: coarse navigation to the approximate region around the tumor; fine-tuning, bringing the stylets to the desired location; and pullback, with MRTR stylets rapidly withdrawn from within the catheters, providing catheter trajectories for radiation treatment planning (RTP). Catheters with conventional stylets were inserted, forming baseline locations. MRTR stylets were substituted, and catheter navigation was performed by a clinician working inside the MRI bore, using monitor feedback. RESULTS Coarse navigation allowed repositioning of the MRTR catheters tips by 16 mm (mean), relative to baseline, in 14 ± 5 s/catheter (mean ± standard deviation [SD]). The fine-tuning mode repositioned the catheter tips by a further 12 mm, in 24 ± 17 s/catheter. Pullback mode provided catheter trajectories with RTP point resolution of ∼1.5 mm, in 1 to 9 s/catheter. CONCLUSIONS MRTR-based navigation resulted in rapid and optimal placement of interstitial brachytherapy catheters. Catheters were repositioned compared with the initial insertion without tracking. In pullback mode, catheter trajectories matched computed tomographic precision, enabling their use for RTP.
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Affiliation(s)
- Jose de Arcos
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts.
| | - Ehud J Schmidt
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts; Department of Medicine, Johns Hopkins Medicine, Baltimore, Maryland
| | - Wei Wang
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts
| | - Junichi Tokuda
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts
| | - Kamal Vij
- Department of Radiation Oncology, Brigham and Women's Hospital, Boston, Massachusetts
| | | | - Antonio L Damato
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | | | - Robert A Cormack
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio
| | - Akila N Viswanathan
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio; Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins Sidney Kimmel Cancer Center, Baltimore, Maryland.
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13
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Merhar SL, Tkach JA, Woods JC, South AP, Wiland EL, Rattan MS, Dumoulin CL, Kline-Fath BM. Neonatal imaging using an on-site small footprint MR scanner. Pediatr Radiol 2017; 47:1001-1011. [PMID: 28470389 DOI: 10.1007/s00247-017-3855-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 02/09/2017] [Accepted: 03/30/2017] [Indexed: 01/06/2023]
Abstract
With its soft-tissue definition, multiplanar capabilities and advanced imaging techniques, magnetic resonance imaging (MRI) for neonatal care can provide better understanding of pathology, allowing for improved care and counseling to families. However, MR imaging in neonates is often difficult due to patient instability and the complex support necessary for survival. In our institution, we have installed a small footprint magnet in the neonatal intensive care unit (NICU) to minimize patient risks and provide the ability to perform MR imaging safely in this population. With this system, we have been able to provide more information with regard to central nervous system disorders, abdominal pathology, and pulmonary and airway abnormalities, and have performed postmortem imaging as an alternative or supplement to pathological autopsy. In our experience, an MR scanner situated within the NICU has allowed for safer and more expedited imaging of this vulnerable population.
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Affiliation(s)
- Stephanie L Merhar
- Division of Neonatology, Cincinnati Children's Hospital Medical Center, Perinatal Institute, Cincinnati, OH, USA
| | - Jean A Tkach
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA
| | - Jason C Woods
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA.,Division of Pulmonary Medicine, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - Andrew P South
- Division of Neonatology, Children's Hospital Medical Center of Akron, Akron, OH, USA
| | - Emily L Wiland
- Division of Neonatology, Children's Hospital Medical Center of Akron, Akron, OH, USA
| | - Mantosh S Rattan
- Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA
| | - Charles L Dumoulin
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA.,Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA
| | - Beth M Kline-Fath
- Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH, 45229, USA.
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14
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Wang W, Viswanathan AN, Damato AL, Chen Y, Tse Z, Pan L, Tokuda J, Seethamraju RT, Dumoulin CL, Schmidt EJ, Cormack RA. Evaluation of an active magnetic resonance tracking system for interstitial brachytherapy. Med Phys 2016; 42:7114-21. [PMID: 26632065 DOI: 10.1118/1.4935535] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE In gynecologic cancers, magnetic resonance (MR) imaging is the modality of choice for visualizing tumors and their surroundings because of superior soft-tissue contrast. Real-time MR guidance of catheter placement in interstitial brachytherapy facilitates target coverage, and would be further improved by providing intraprocedural estimates of dosimetric coverage. A major obstacle to intraprocedural dosimetry is the time needed for catheter trajectory reconstruction. Herein the authors evaluate an active MR tracking (MRTR) system which provides rapid catheter tip localization and trajectory reconstruction. The authors assess the reliability and spatial accuracy of the MRTR system in comparison to standard catheter digitization using magnetic resonance imaging (MRI) and CT. METHODS The MRTR system includes a stylet with microcoils mounted on its shaft, which can be inserted into brachytherapy catheters and tracked by a dedicated MRTR sequence. Catheter tip localization errors of the MRTR system and their dependence on catheter locations and orientation inside the MR scanner were quantified with a water phantom. The distances between the tracked tip positions of the MRTR stylet and the predefined ground-truth tip positions were calculated for measurements performed at seven locations and with nine orientations. To evaluate catheter trajectory reconstruction, fifteen brachytherapy catheters were placed into a gel phantom with an embedded catheter fixation framework, with parallel or crossed paths. The MRTR stylet was then inserted sequentially into each catheter. During the removal of the MRTR stylet from within each catheter, a MRTR measurement was performed at 40 Hz to acquire the instantaneous stylet tip position, resulting in a series of three-dimensional (3D) positions along the catheter's trajectory. A 3D polynomial curve was fit to the tracked positions for each catheter, and equally spaced dwell points were then generated along the curve. High-resolution 3D MRI of the phantom was performed followed by catheter digitization based on the catheter's imaging artifacts. The catheter trajectory error was characterized in terms of the mean distance between corresponding dwell points in MRTR-generated catheter trajectory and MRI-based catheter digitization. The MRTR-based catheter trajectory reconstruction process was also performed on three gynecologic cancer patients, and then compared with catheter digitization based on MRI and CT. RESULTS The catheter tip localization error increased as the MRTR stylet moved further off-center and as the stylet's orientation deviated from the main magnetic field direction. Fifteen catheters' trajectories were reconstructed by MRTR. Compared with MRI-based digitization, the mean 3D error of MRTR-generated trajectories was 1.5 ± 0.5 mm with an in-plane error of 0.7 ± 0.2 mm and a tip error of 1.7 ± 0.5 mm. MRTR resolved ambiguity in catheter assignment due to crossed catheter paths, which is a common problem in image-based catheter digitization. In the patient studies, the MRTR-generated catheter trajectory was consistent with digitization based on both MRI and CT. CONCLUSIONS The MRTR system provides accurate catheter tip localization and trajectory reconstruction in the MR environment. Relative to the image-based methods, it improves the speed, safety, and reliability of the catheter trajectory reconstruction in interstitial brachytherapy. MRTR may enable in-procedural dosimetric evaluation of implant target coverage.
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Affiliation(s)
- Wei Wang
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02115 and Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Akila N Viswanathan
- Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Antonio L Damato
- Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Yue Chen
- Department of Engineering, The University of Georgia, Athens, Georgia 30602
| | - Zion Tse
- Department of Engineering, The University of Georgia, Athens, Georgia 30602
| | - Li Pan
- Siemens Healthcare USA, Baltimore, Maryland 21287
| | - Junichi Tokuda
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | | | - Charles L Dumoulin
- Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229
| | - Ehud J Schmidt
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts 02115
| | - Robert A Cormack
- Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, Massachusetts 02115
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15
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Tse ZTH, Dumoulin CL, Clifford GD, Schweitzer J, Qin L, Oster J, Jerosch-Herold M, Kwong RY, Michaud G, Stevenson WG, Schmidt EJ. A 1.5T MRI-conditional 12-lead electrocardiogram for MRI and intra-MR intervention. Magn Reson Med 2015; 71:1336-47. [PMID: 23580148 DOI: 10.1002/mrm.24744] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
PURPOSE High-fidelity 12-lead electrocardiogram (ECG) is important for physiological monitoring of patients during MR-guided intervention and cardiac MRI. Issues in obtaining noncorrupted ECGs inside MRI include a superimposed magneto-hydro-dynamic voltage, gradient switching-induced voltages, and radiofrequency heating. These problems increase with magnetic field. The aim of this study is to develop and clinically validate a 1.5T MRI-conditional 12-lead ECG system. METHODS The system was constructed with transmission lines to reduce radiofrequency induction and switching circuits to remove induced voltages. Adaptive filters, trained by 12-lead measurements outside MRI and in two orientations inside MRI, were used to remove the magneto-hydro-dynamic voltage. The system was tested on 10 (one exercising) volunteers and four arrhythmia patients. RESULTS Switching circuits removed most imaging-induced voltages (residual noise <3% of the R-wave). Magneto-hydro-dynamic voltage removal provided intra-MRI ECGs that varied by <3.8% from those outside the MRI, preserving the true S-wave to T-wave segment. In premature ventricular contraction (PVC) patients, clean ECGs separated premature ventricular contraction and sinus rhythm beats. Measured heating was <1.5°C. The system reliably acquired multiphase (steady-state free precession) wall-motion-cine and phase-contrast-cine scans, including subjects in whom 4-lead gating failed. The system required a minimum repetition time of 4 ms to allow robust ECG processing. CONCLUSION High-fidelity intra-MRI 12-lead ECG is possible.
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Affiliation(s)
- Zion Tsz Ho Tse
- The University of Georgia, College of Engineering, Driftmier Engineering Center, 597 D. W. Brook Drive, Athens, GA 30602, USA
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16
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Schmidt EJ, Tse ZTH, Reichlin TR, Michaud GF, Watkins RD, Butts-Pauly K, Kwong RY, Stevenson W, Schweitzer J, Byrd I, Dumoulin CL. Voltage-based device tracking in a 1.5 Tesla MRI during imaging: initial validation in swine models. Magn Reson Med 2015; 71:1197-209. [PMID: 23580479 DOI: 10.1002/mrm.24742] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
PURPOSE Voltage-based device-tracking (VDT) systems are commonly used for tracking invasive devices in electrophysiological cardiac-arrhythmia therapy. During electrophysiological procedures, electro-anatomic mapping workstations provide guidance by integrating VDT location and intracardiac electrocardiogram information with X-ray, computerized tomography, ultrasound, and MR images. MR assists navigation, mapping, and radiofrequency ablation. Multimodality interventions require multiple patient transfers between an MRI and the X-ray/ultrasound electrophysiological suite, increasing the likelihood of patient-motion and image misregistration. An MRI-compatible VDT system may increase efficiency, as there is currently no single method to track devices both inside and outside the MRI scanner. METHODS An MRI-compatible VDT system was constructed by modifying a commercial system. Hardware was added to reduce MRI gradient-ramp and radiofrequency unblanking pulse interference. VDT patches and cables were modified to reduce heating. Five swine cardiac VDT electro-anatomic mapping interventions were performed, navigating inside and thereafter outside the MRI. RESULTS Three-catheter VDT interventions were performed at >12 frames per second both inside and outside the MRI scanner with <3 mm error. Catheters were followed on VDT- and MRI-derived maps. Simultaneous VDT and imaging was possible in repetition time >32 ms sequences with <0.5 mm errors, and <5% MRI signal-to-noise ratio (SNR) loss. At shorter repetition times, only intracardiac electrocardiogram was reliable. Radiofrequency heating was <1.5°C. CONCLUSION An MRI-compatible VDT system is feasible.
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Affiliation(s)
- Ehud J Schmidt
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
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17
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Ireland CM, Giaquinto RO, Loew W, Tkach JA, Pratt RG, Kline-Fath BM, Merhar SL, Dumoulin CL. A novel acoustically quiet coil for neonatal MRI system. Concepts Magn Reson Part B Magn Reson Eng 2015; 45:107-114. [PMID: 26457072 PMCID: PMC4594852 DOI: 10.1002/cmr.b.21287] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
MRI acoustic exposure has the potential to elicit physiological distress and impact development in preterm and term infants. To mitigate this risk, a novel acoustically quiet coil was developed to reduce the sound pressure level experienced by neonates during MR procedures. The new coil has a conventional high-pass birdcage RF design, but is built on a framework of sound abating material. We evaluated the acoustic and MR imaging performance of the quiet coil and a conventional body coil on two small footprint NICU MRI systems. Sound pressure level and frequency response measurements were made for six standard clinical MR imaging protocols. The average sound pressure level, reported for all six imaging pulse sequences, was 82.2 dBA for the acoustically quiet coil, and 91.1 dBA for the conventional body coil. The sound pressure level values measured for the acoustically quiet coil were consistently lower, 9 dBA (range 6-10 dBA) quieter on average. The acoustic frequency response of the two coils showed a similar harmonic profile for all imaging sequences. However, the amplitude was lower for the quiet coil, by as much as 20 dBA.
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Affiliation(s)
- Christopher M Ireland
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA ; Department of Biomedical, Chemical, and Environmental Engineering, 601 Engineering Research Center, University of Cincinnati, 2901 Woodside Drive, Cincinnati, OH 45220, USA
| | - Randy O Giaquinto
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Wolfgang Loew
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Jean A Tkach
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Ronald G Pratt
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Beth M Kline-Fath
- Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Stephanie L Merhar
- Division of Neonatology and Pulmonary Biology, Perinatal Institute, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
| | - Charles L Dumoulin
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., Cincinnati, OH 45229, USA
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Zhang SH, Tse ZTH, Dumoulin CL, Kwong RY, Stevenson WG, Watkins R, Ward J, Wang W, Schmidt EJ. Gradient-induced voltages on 12-lead ECGs during high duty-cycle MRI sequences and a method for their removal considering linear and concomitant gradient terms. Magn Reson Med 2015; 75:2204-16. [PMID: 26101951 DOI: 10.1002/mrm.25810] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 05/18/2015] [Accepted: 05/23/2015] [Indexed: 11/08/2022]
Abstract
PURPOSE To restore 12-lead electrocardiographic (ECG) signal fidelity inside MRI by removing magnetic field gradient-induced voltages during high gradient duty cycle sequences. THEORY AND METHODS A theoretical equation was derived to provide first- and second-order electrical fields induced at individual ECG electrodes as a function of gradient fields. Experiments were performed at 3T on healthy volunteers using a customized acquisition system that captured the full amplitude and frequency response of ECGs, or a commercial recording system. The 19 equation coefficients were derived via linear regression of data from accelerated sequences and were used to compute induced voltages in real-time during full resolution sequences to remove ECG artifacts. Restored traces were evaluated relative to ones acquired without imaging. RESULTS Measured induced voltages were 0.7 V peak-to-peak during balanced steady state free precession (bSSFP) with the heart at the isocenter. Applying the equation during gradient echo sequencing, three-dimensional fast spin echo, and multislice bSSFP imaging restored nonsaturated traces and second-order concomitant terms showed larger contributions in electrodes further from the magnet isocenter. Equation coefficients are evaluated with high repeatability (ρ = 0.996) and are dependent on subject, sequence, and slice orientation. CONCLUSION Close agreement between theoretical and measured gradient-induced voltages allowed for real-time removal. Prospective estimation of sequence periods in which large induced voltages occur may allow hardware removal of these signals.
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Affiliation(s)
- Shelley HuaLei Zhang
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Zion Tsz Ho Tse
- Department of Engineering, University of Georgia, Athens, Georgia, USA
| | - Charles L Dumoulin
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, USA
| | - Raymond Y Kwong
- Department of Cardiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - William G Stevenson
- Department of Cardiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Ronald Watkins
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Jay Ward
- E-TROLZ Inc, North Andover, Massachusetts, USA
| | - Wei Wang
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | - Ehud J Schmidt
- Department of Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA
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Zhang SH, Tse ZT, Dumoulin CL, Watkins RD, Wang W, Ward J, Kwong RY, Stevenson WG, Schmidt EJ. Gradient-induced voltages on 12-lead ECGs during high-duty-cycle MRI sequences and a theoretically-based method to remove them. J Cardiovasc Magn Reson 2015. [PMCID: PMC4328402 DOI: 10.1186/1532-429x-17-s1-p243] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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20
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Tkach JA, Li Y, Pratt RG, Baroch KA, Loew W, Daniels BR, Giaquinto RO, Merhar SL, Kline-Fath BM, Dumoulin CL. Characterization of acoustic noise in a neonatal intensive care unit MRI system. Pediatr Radiol 2014; 44:1011-9. [PMID: 24595878 PMCID: PMC4241776 DOI: 10.1007/s00247-014-2909-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2013] [Revised: 12/13/2013] [Accepted: 01/29/2014] [Indexed: 11/26/2022]
Abstract
BACKGROUND To eliminate the medical risks and logistical challenges of transporting infants from the neonatal intensive care unit (NICU) to the radiology department for magnetic resonance imaging, a small-footprint 1.5-T MRI scanner has been developed for neonatal imaging within the NICU. MRI is known to be noisy, and exposure to excessive acoustic noise has the potential to elicit physiological distress and impact development in the term and preterm infant. OBJECTIVE To measure and compare the acoustic noise properties of the NICU MRI system against those of a conventional 1.5-T MRI system. MATERIALS AND METHODS We performed sound pressure level measurements in the NICU MRI scanner and in a conventional adult-size whole-body 1.5-T MRI system. Sound pressure level measurements were made for six standard clinical MR imaging protocols. RESULTS The average sound pressure level value, reported in unweighted (dB) and A-weighted (dBA) decibels for all six imaging pulse sequences, was 73.8 dB and 88 dBA for the NICU scanner, and 87 dB and 98.4 dBA for the conventional MRI scanner. The sound pressure level values measured on the NICU scanner for each of the six MR imaging pulse sequences were consistently and significantly (P = 0.03) lower, with an average difference of 14.2 dB (range 10-21 dB) and 11 dBA (range 5-18 dBA). The sound pressure level frequency response of the two MR systems showed a similar harmonic structure above 200 Hz for all imaging sequences. The amplitude, however, was appreciably lower for the NICU scanner, by as much as 30 dB, for frequencies below 200 Hz. CONCLUSION The NICU MRI system is quieter than conventional MRI scanners, improving safety for the neonate and facilitating siting of the unit within the NICU.
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Affiliation(s)
- Jean A Tkach
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 240 Albert Sabin Way, MLC 5033, Cincinnati, OH, 45229, USA,
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Wang W, Dumoulin CL, Viswanathan AN, Tse ZTH, Mehrtash A, Loew W, Norton I, Tokuda J, Seethamraju RT, Kapur T, Damato AL, Cormack RA, Schmidt EJ. Real-time active MR-tracking of metallic stylets in MR-guided radiation therapy. Magn Reson Med 2014; 73:1803-11. [PMID: 24903165 DOI: 10.1002/mrm.25300] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Revised: 05/01/2014] [Accepted: 05/02/2014] [Indexed: 11/10/2022]
Abstract
PURPOSE To develop an active MR-tracking system to guide placement of metallic devices for radiation therapy. METHODS An actively tracked metallic stylet for brachytherapy was constructed by adding printed-circuit micro-coils to a commercial stylet. The coil design was optimized by electromagnetic simulation, and has a radio-frequency lobe pattern extending ∼5 mm beyond the strong B0 inhomogeneity region near the metal surface. An MR-tracking sequence with phase-field dithering was used to overcome residual effects of B0 and B1 inhomogeneities caused by the metal, as well as from inductive coupling to surrounding metallic stylets. The tracking system was integrated with a graphical workstation for real-time visualization. The 3 Tesla MRI catheter-insertion procedures were tested in phantoms and ex vivo animal tissue, and then performed in three patients during interstitial brachytherapy. RESULTS The tracking system provided high-resolution (0.6 × 0.6 × 0.6 mm(3) ) and rapid (16 to 40 frames per second, with three to one phase-field dithering directions) catheter localization in phantoms, animals, and three gynecologic cancer patients. CONCLUSION This is the first demonstration of active tracking of the shaft of metallic stylet in MR-guided brachytherapy. It holds the promise of assisting physicians to achieve better targeting and improving outcomes in interstitial brachytherapy.
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Affiliation(s)
- Wei Wang
- Radiology, Brigham and Women's Hospital, Boston, Massachusetts, USA; Radiation Oncology, Brigham and Women's Hospital, Boston, Massachusetts, USA
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Zhang SH, Tse ZT, Dumoulin CL, Bryd I, Schweitzer J, Watkins RG, Butts-Pauly K, Kwong RY, Barbhaiya CR, Stevenson WG, Jolesz F, Schmidt EJ. MRI-compatible voltage-based electroanatomic mapping system for 3T MR-guided cardiac electrophysiology: swine validations. J Cardiovasc Magn Reson 2014. [PMCID: PMC4043355 DOI: 10.1186/1532-429x-16-s1-p140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023] Open
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Qin L, Schmidt EJ, Tse ZTH, Santos J, Hoge WS, Tempany-Afdhal C, Butts-Pauly K, Dumoulin CL. Prospective motion correction using tracking coils. Magn Reson Med 2013; 69:749-59. [PMID: 22565377 PMCID: PMC3416927 DOI: 10.1002/mrm.24310] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 03/31/2012] [Accepted: 04/04/2012] [Indexed: 11/10/2022]
Abstract
Intracavity imaging coils provide higher signal-to-noise than surface coils and have the potential to provide higher spatial resolution in shorter acquisition times. However, images from these coils suffer from physiologically induced motion artifacts, as both the anatomy and the coils move during image acquisition. We developed prospective motion-correction techniques for intracavity imaging using an array of tracking coils. The system had <50 ms latency between tracking and imaging, so that the images from the intracavity coil were acquired in a frame of reference defined by the tracking array rather than by the system's gradient coils. Two-dimensional gradient-recalled and three-dimensional electrocardiogram-gated inversion-recovery-fast-gradient-echo sequences were tested with prospective motion correction using ex vivo hearts placed on a moving platform simulating both respiratory and cardiac motion. Human abdominal tests were subsequently conducted. The tracking array provided a positional accuracy of 0.7 ± 0.5 mm, 0.6 ± 0.4 mm, and 0.1 ± 0.1 mm along the X, Y, and Z directions at a rate of 20 frames-per-second. The ex vivo and human experiments showed significant image quality improvements for both in-plane and through-plane motion correction, which although not performed in intracavity imaging, demonstrates the feasibility of implementing such a motion-correction system in a future design of combined tracking and intracavity coil.
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Affiliation(s)
- Lei Qin
- Department of Radiology, Dana-Farber Cancer Institute, Boston, Massachusetts 02215, USA.
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Tkach JA, Hillman NH, Jobe AH, Loew W, Pratt RG, Daniels BR, Kallapur SG, Kline-Fath BM, Merhar SL, Giaquinto RO, Winter PM, Li Y, Ikegami M, Whitsett JA, Dumoulin CL. An MRI system for imaging neonates in the NICU: initial feasibility study. Pediatr Radiol 2012; 42:1347-56. [PMID: 22735927 DOI: 10.1007/s00247-012-2444-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2012] [Revised: 05/09/2012] [Accepted: 05/17/2012] [Indexed: 11/26/2022]
Abstract
BACKGROUND Transporting premature infants from a neonatal intensive care unit (NICU) to a radiology department for MRI has medical risks and logistical challenges. OBJECTIVE To develop a small 1.5-T MRI system for neonatal imaging that can be easily installed in the NICU and to evaluate its performance using a sheep model of human prematurity. MATERIALS AND METHODS A 1.5-T MRI system designed for orthopedic use was adapted for neonatal imaging. The system was used for MRI examinations of the brain, chest and abdomen in 12 premature lambs during the first hours of life. Spin-echo, fast spin-echo and gradient-echo MR images were evaluated by two pediatric radiologists. RESULTS All animals remained physiologically stable throughout the imaging sessions. Animals were imaged at two or three time points. Seven brain MRI examinations were performed in seven different animals, 23 chest examinations in 12 animals and 19 abdominal examinations in 11 animals. At each anatomical location, high-quality images demonstrating good spatial resolution, signal-to-noise ratio and tissue contrast were routinely obtained within 30 min using standard clinical protocols. CONCLUSION Our preliminary experience demonstrates the feasibility and potential of the neonatal MRI system to provide state-of-the-art MRI capabilities within the NICU. Advantages include overall reduced cost and site demands, lower acoustic noise, improved ease of access and reduced medical risk to the neonate.
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Affiliation(s)
- Jean A Tkach
- Imaging Research Center, Department of Radiology, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave., MLC 5033, Cincinnati, OH 45229, USA.
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Tse ZTH, Dumoulin CL, Clifford G, Jerosch-Herold M, Kacher D, Kwong R, Stevenson WG, Schmidt EJ. Improved R-wave detection for enhanced cardiac Gating using an MRI-compatible 12-lead ECG and multi-channel analysis. J Cardiovasc Magn Reson 2011. [PMCID: PMC3106913 DOI: 10.1186/1532-429x-13-s1-p3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Ho Tse ZT, Dumoulin CL, Clifford G, Jerosch-Herold M, Kacher D, Kwong R, Stevenson WG, Schmidt EJ. Real-ECG extraction and stroke volume from MR-Compatible 12-lead ECGs; testing during stress, in PVC and in AF patients. J Cardiovasc Magn Reson 2011. [PMCID: PMC3106584 DOI: 10.1186/1532-429x-13-s1-p6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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Donnelly LF, Gessner KE, Dickerson JM, Koch BL, Towbin AJ, Lehkamp TW, Moskovitz J, Brody AS, Dumoulin CL, Jones BV. Quality Initiatives: Department Scorecard: A Tool to Help Drive Imaging Care Delivery Performance. Radiographics 2010; 30:2029-38. [DOI: 10.1148/rg.307105017] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Abstract
A strategy to increase the robustness of active MR tracking of microcoils in low signal-to-noise ratio conditions was developed and tested. The method employs dephasing magnetic field gradient pulses that are applied orthogonal to the frequency-encoding gradient pulse used in conventional point-source MR tracking. In subsequent acquisitions, the orthogonal dephasing gradient pulse is rotated while maintaining a perpendicular orientation with respect to the frequency-encoding gradient. The effect of the dephasing gradient is to apply a spatially dependent phase shift in directions perpendicular to the frequency-encoding gradient. Since the desired MR signal for robust MR tracking comes from the small volume of nuclear spins near the small detection coil, the desired signal is not dramatically altered by the dephasing gradient. Undesired MR signals arising from larger volumes (e.g., due to coupling with the body coil or surface coils), on the other hand, are dephased and reduced in signal intensity. Since the approach requires no a priori knowledge of the microcoil orientation with respect to the main magnetic field, data from several orthogonal dephasing gradients are acquired and analyzed in real time. One of several selection algorithms is employed to identify the "best" data for use in the coil localization algorithm. This approach was tested in flow phantoms and animal models, with several multiplexing schemes, including the Hadamard and zero-phase reference approaches. It was found to provide improved MR tracking of untuned microcoils. It also dramatically improved MR tracking robustness in low signal-to-noise-ratio conditions and permitted tracking of microcoils that were inductively coupled to the body coil.
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Affiliation(s)
- Charles L Dumoulin
- Department of Radiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
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Tse ZTH, Dumoulin CL, Clifford G, Jerosch-Herold M, Kacher D, Kwong R, Stevenson WG, Schmidt EJ. 12-lead ECG in a 1.5 Tesla MRI: Separation of real ECG and MHD voltages with adaptive filtering for gating and non-invasive cardiac output. J Cardiovasc Magn Reson 2010. [DOI: 10.1186/1532-429x-12-s1-o95] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Schmidt EJ, Mallozzi RP, Thiagalingam A, Holmvang G, d'Avila A, Guhde R, Darrow R, Slavin GS, Fung MM, Dando J, Foley L, Dumoulin CL, Reddy VY. Electroanatomic mapping and radiofrequency ablation of porcine left atria and atrioventricular nodes using magnetic resonance catheter tracking. Circ Arrhythm Electrophysiol 2010; 2:695-704. [PMID: 19841033 DOI: 10.1161/circep.109.882472] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The MRI-compatible electrophysiology system previously used for MR-guided left ventricular electroanatomic mapping was enhanced with improved MR tracking, an MR-compatible radiofrequency ablation system and higher-resolution imaging sequences to enable mapping, ablation, and ablation monitoring in smaller cardiac structures. MR-tracked navigation was performed to the left atrium (LA) and atrioventricular (AV) node, followed by LA electroanatomic mapping and radiofrequency ablation of the pulmonary veins (PVs) and AV node. METHODS AND RESULTS One ventricular ablation, 7 PV ablations, 3 LA mappings, and 3 AV node ablations were conducted. Three MRI-compatible devices (ablation/mapping catheter, torqueable sheath, stimulation/pacing catheter) were used, each with 4 to 5 tracking microcoils. Transseptal puncture was performed under x-ray, with all other procedural steps performed in the MRI. Preacquired MRI roadmaps served for real-time catheter navigation. Simultaneous tracking of 3 devices was performed at 13 frames per second. LA mapping and PV radiofrequency ablation were performed using tracked ablation catheters and sheaths. Ablation points were registered and verified after ablation using 3D myocardial delayed enhancement and postmortem gross tissue examination. Complete LA electroanatomic mapping was achieved in 3 of 3 pigs, Right inferior PV circumferential ablation was achieved in 3 of 7 pigs, with incomplete isolation caused by limited catheter deflection. During AV node ablation, ventricular pacing was performed, 3 devices were simultaneously tracked, and intracardiac ECGs were displayed. 3D myocardial delayed enhancement visualized node injury 2 minutes after ablation. AV node block succeeded in 2 of 3 pigs, with 1 temporary block. CONCLUSIONS LA mapping, PV radiofrequency ablation, and AV node ablation were demonstrated under MRI guidance. Intraprocedural 3D myocardial delayed enhancement assessed lesion positional accuracy and dimensions.
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Affiliation(s)
- Ehud J Schmidt
- Department of Radiology, Brigham and Women's Hospital, Boston, MA 02115, USA.
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Schmidt EJ, Yoneyama R, Dumoulin CL, Darrow RD, Klein E, Kiruluta AJ, Hayase M. 3D coronary motion tracking in swine models with MR tracking catheters. J Magn Reson Imaging 2009; 29:86-98. [DOI: 10.1002/jmri.21468] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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Schmidt EJ, Thiagalingam A, d'Avila A, Holmvang G, Guhde R, Darrow RD, Dando JD, Peterson S, Mallozzi RP, Dumoulin CL, Reddy VY. 307 MRI-guided atrio-ventricular node ablation in swine models using MRI tracking. J Cardiovasc Magn Reson 2008. [DOI: 10.1186/1532-429x-10-s1-a110] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Dukkipati SR, Mallozzi R, Schmidt EJ, Holmvang G, d'Avila A, Guhde R, Darrow RD, Slavin G, Fung M, Malchano Z, Kampa G, Dando JD, McPherson C, Foo TK, Ruskin JN, Dumoulin CL, Reddy VY. Electroanatomic mapping of the left ventricle in a porcine model of chronic myocardial infarction with magnetic resonance-based catheter tracking. Circulation 2008; 118:853-62. [PMID: 18678773 DOI: 10.1161/circulationaha.107.738229] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND X-ray fluoroscopy constitutes the fundamental imaging modality for catheter visualization during interventional electrophysiology procedures. The minimal tissue discriminative capability of fluoroscopy is mitigated in part by the use of electroanatomic mapping systems and enhanced by the integration of preacquired 3-dimensional imaging of the heart with computed tomographic or magnetic resonance (MR) imaging. A more ideal paradigm might be to use intraprocedural MR imaging to directly image and guide catheter mapping procedures. METHODS AND RESULTS An MR imaging-based electroanatomic mapping system was designed to assess the feasibility of navigating catheters to the left ventricle in vivo using MR tracking of microcoils incorporated into the catheters, measuring intracardiac ventricular electrograms, and integrating this information with 3-dimensional MR angiography and myocardial delayed enhancement images to allow ventricular substrate mapping. In all animals (4 normal, and 10 chronically infarcted swine), after transseptal puncture under fluoroscopic guidance, catheters were successfully navigated to the left ventricle with MR tracking (13 to 15 frames per second) by both transseptal and retrograde aortic approaches. Electrogram artifacts related to the MR imaging gradient pulses were successfully removed with analog and digital signal processing. In all animals, it was possible to map the entire left ventricle and to project electrogram voltage amplitude maps to identify the scarred myocardium. CONCLUSIONS It is possible to use MR tracking to navigate catheters to the left ventricle, to measure electrogram activity, and to render accurate 3-dimensional voltage maps in a porcine model of chronic myocardial infarction, completely in the MR imaging environment. Myocardial delayed enhancement guidance provided dense sampling of the proximity of the infarct and accurate localization of complex infarcts.
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Affiliation(s)
- Srinivas R Dukkipati
- Cardiac Arrhythmia Service, Massachusetts General Hospital and Harvard Medical School, Boston, Mass., USA
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Reddy VY, Malchano ZJ, Dukkipati S, Godtfred H, Schmidt EJ, Dumoulin CL, Mallozzi RP, Ruskin JN. Interventional MRI: Electroanatomical mapping using real-time MR tracking of a deflectable catheter. Heart Rhythm 2005. [DOI: 10.1016/j.hrthm.2005.02.880] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Abstract
The emergence of parallel MRI techniques and new applications for real-time interactive MRI underscores the need to evaluate performance gained by increasing the capability of MRI phased-array systems beyond the standard four to eight high-bandwidth channels. Therefore, to explore the advantages of highly parallel MRI a 32-channel 1.5 T MRI system and 32-element torso phased arrays were designed and constructed for real-time interactive MRI. The system was assembled from multiple synchronized scanner-receiver subsystems. Software was developed to coordinate across subsystems the real-time acquisition, reconstruction, and display of 32-channel images. Real-time, large field-of-view (FOV) body-survey imaging was performed using interleaved echo-planar and single-shot fast-spin-echo pulse sequences. A new method is demonstrated for augmenting parallel image acquisition by independently offsetting the frequency of different array elements (FASSET) to variably shift their FOV. When combined with conventional parallel imaging techniques, image acceleration factors of up to 4 were investigated. The use of a large number of coils allowed the FOV to be doubled in two dimensions during rapid imaging, with no degradation of imaging time or spatial resolution. The system provides a platform for evaluating the applications of many-channel real-time MRI, and for understanding the factors that optimize the choice of array size.
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Feng L, Dumoulin CL, Dashnaw S, Darrow RD, Delapaz RL, Bishop PL, Pile-Spellman J. Feasibility of Stent Placement in Carotid Arteries with Real-time MR Imaging Guidance in Pigs. Radiology 2005; 234:558-62. [PMID: 15591432 DOI: 10.1148/radiol.2341031950] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
All examinations were performed with approval from the institutional animal care and use committee of Columbia University. To assess the feasibility of real-time magnetic resonance (MR) imaging-guided neurovascular intervention in a swine model, the authors placed stents in the carotid arteries of five domestic pigs. Seven-French vascular sheaths were placed in the target carotid arteries via femoral access by using active MR tracking. Ten nitinol stents (8-10 x 20-40 mm) were successfully deployed in the target segments of carotid arteries bilaterally. MR imaging and necropsy findings confirmed stent position. Necropsy revealed no gross vascular injury. Study results demonstrated the feasibility of performing real-time MR imaging-guided neurovascular intervention by using an active-tracking technique in an animal model.
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Affiliation(s)
- Lei Feng
- Department of Radiology, Columbia University, 177 Fort Washington Ave, MHB 8SK, New York, NY 10032, USA
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Feng L, Dumoulin CL, Dashnaw S, Darrow RD, Guhde R, Delapaz RL, Bishop PL, Pile-Spellman J. Transfemoral catheterization of carotid arteries with real-time MR imaging guidance in pigs. Radiology 2004; 234:551-7. [PMID: 15591433 DOI: 10.1148/radiol.2341031951] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
All procedures and protocols were approved by the institutional animal care and use committee of Columbia University. To determine whether transfemoral catheterization of the carotid arteries can be performed entirely with real-time magnetic resonance (MR) imaging guidance, the authors catheterized the carotid arteries in six domestic pigs by using active-tracking catheters and guidewires and MR tracking software created for neurovascular procedures. The carotid arteries were successfully catheterized 24 times, on average within 5 minutes after insertion of the catheter into the femoral artery. Results demonstrated the feasibility of performing transfemoral catheterization of the carotid arteries with active MR tracking devices in a conventional MR imaging unit.
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Affiliation(s)
- Lei Feng
- Department of Radiology, Columbia University, 177 Fort Washington Ave, MHB 8SK, New York, NY 10032, USA
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Zhu Y, Hardy CJ, Sodickson DK, Giaquinto RO, Dumoulin CL, Kenwood G, Niendorf T, Lejay H, McKenzie CA, Ohliger MA, Rofsky NM. Highly parallel volumetric imaging with a 32-element RF coil array. Magn Reson Med 2004; 52:869-77. [PMID: 15389961 PMCID: PMC2819016 DOI: 10.1002/mrm.20209] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2004] [Accepted: 05/14/2004] [Indexed: 11/08/2022]
Abstract
The improvement of MRI speed with parallel acquisition is ultimately an SNR-limited process. To offset acquisition- and reconstruction-related SNR losses, practical parallel imaging at high accelerations should include the use of a many-element array with a high intrinsic signal-to-noise ratio (SNR) and spatial-encoding capability, and an advantageous imaging paradigm. We present a 32-element receive-coil array and a volumetric paradigm that address the SNR challenge at high accelerations by maximally exploiting multidimensional acceleration in conjunction with noise averaging. Geometric details beyond an initial design concept for the array were determined with the guidance of simulations. Imaging with the support of 32-channel data acquisition systems produced in vivo results with up to 16-fold acceleration, including images from rapid abdominal and MRA studies.
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Affiliation(s)
- Yudong Zhu
- General Electric Global Research Center, Schenectady, New York 12309, USA.
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Schumacher HC, Dumoulin CL, Feng L, Mangla S, Meyers PM, Hirsch J, Mohr JP, DeLaPaz RL, Pile-Spellman J. Real-time magnetic resonance imaging for interventional neuroradiological procedures. Surg Technol Int 2004; 11:183-96. [PMID: 12931300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
Over the last two decades, interventional neuroradiologists have developed powerful techniques for the treatment of cerebrovascular disorders and brain tumors. Current interventional neuroradiological procedures are performed under X-ray fluoroscopy, which has allowed for high temporal and spatial resolution. However, these imaging techniques do not provide the treating physician with vital anatomic and functional information regarding vessel walls and the surrounding brain tissue. Better visualization of vessel structures and real-time information about the state of perfusion and metabolism of the surrounding brain tissue (real-time magnetic resonance arteriography, diffusion and perfusion-weighted imaging, apparent diffusion coefficient maps) would enhance safety and efficacy of neuroendovascular procedures available currently. Recent advances in magnetic resonance hardware and software have permitted significant enhancements in temporal and spatial resolution, which have resulted in the capability of visualizing anatomic structures with real-time fluoroscopy and angiography. This review outlines how real-time magnetic resonance procedures may replace conventional X-ray fluoroscopy in diagnostic and interventional neuroradiology during the next decade.
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Affiliation(s)
- H Christian Schumacher
- Doris and Stanley Tananbaum Stroke Center, Neurological Institute, New York Presbyterian Hospital, College of Physicians and Surgeons of Columbia University, New York, NY, USA
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40
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Abstract
A new method for MRI of an extended field of view (FOV) has been developed and validated. The method employs concurrent MR data acquisition and patient table motion. Table motion-induced image artifacts are minimized by sweeping the frequency of the receiver at a rate matching the table's speed. Multiple regional images are collected and combined to reconstruct the full FOV. The imaging parameters and table speed are chosen to ensure that each regional image of the subject is collected while the corresponding anatomy is in the useable imaging volume of the scanner. Additional strategies are applied to further reduce field inhomogeneity-induced artifacts, especially distortions due to gradient field nonlinearity. The method is robust and can be easily incorporated into most multislice 2D and volumetric 3D imaging pulse sequences. It is anticipated that this technique will be useful for a variety of applications, including angiographic runoffs, whole-body screening, and short-magnet imaging.
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Affiliation(s)
- Yudong Zhu
- GE Global Research Center, Niskayuna, New York 12309, USA.
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Dumoulin CL, Rohling KW, Piel JE, Rossi CJ, Giaquinto RO, Watkins RD, Vigneron DB, Barkovich AJ, Newton N. Magnetic resonance imaging compatible neonate incubator. ACTA ACUST UNITED AC 2002. [DOI: 10.1002/cmr.10028] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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42
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Sotak CH, Dumoulin CL, Levy GC. Software for quantitative analysis by carbon-13 Fourier transform nuclear magnetic resonance spectrometry. Anal Chem 2002. [DOI: 10.1021/ac00255a043] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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43
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Sherwin SJ, Shah O, Doorly DJ, Peiró J, Papaharilaou Y, Watkins N, Caro CG, Dumoulin CL. The influence of out-of-plane geometry on the flow within a distal end-to-side anastomosis. J Biomech Eng 2000; 122:86-95. [PMID: 10790834 DOI: 10.1115/1.429630] [Citation(s) in RCA: 68] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This paper describes a computational and experimental investigation of flow in a proto-type model geometry of a fully occluded 45 deg distal end-to-side anastomosis. Previous investigations have considered a similar configuration where the centerlines of the bypass and host vessels lie within a plane, thereby producing a plane of symmetry within the flow. We have extended these investigations by deforming the bypass vessel out of the plane of symmetry, thereby breaking the symmetry of the flow and producing a nonplanar geometry. Experimental data were obtained using magnetic resonance imaging of flow within perspex models and computational data were obtained from simulations using a high-order spectral/hp element method. We found that the nonplanar three-dimensional flow notably alters the distribution of wall shear stress at the bed of the anastomosis, reducing the peak wall shear stress peak by approximately 10 percent when compared with the planar model. Furthermore, an increase in the absolute flux of velocity into the occluded region, proximal to the anastomosis, of 80 percent was observed in the nonplanar geometry when compared with the planar geometry.
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Affiliation(s)
- S J Sherwin
- Aeronautics Department, Imperial College, London, United Kingdom
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44
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Beaulieu CF, Hodge DK, Bergman AG, Butts K, Daniel BL, Napper CL, Darrow RD, Dumoulin CL, Herfkens RJ. Glenohumeral relationships during physiologic shoulder motion and stress testing: initial experience with open MR imaging and active imaging-plane registration. Radiology 1999; 212:699-705. [PMID: 10478235 DOI: 10.1148/radiology.212.3.r99se31699] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To test the hypotheses that open dynamic magnetic resonance (MR) imaging can (a) be used to evaluate and define normal shoulder motion in active joint motion and muscle contraction and (b) be used in conjunction with physical examination. MATERIALS AND METHODS With an open-configuration, 0.5-T MR imaging system and active image-plane tracking, 10 shoulders were studied in five asymptomatic subjects to establish normal patterns of glenohumeral motion during abduction and adduction and internal and external rotation. Preliminary studies of physical examination during MR imaging, in which a physician examiner applied mechanical force to the humeral head, were also performed. RESULTS During abduction and adduction and internal and external rotation maneuvers with active subjects muscle contraction, the humeral head remained precisely centered on the glenoid fossa in all asymptomatic subjects, which is in agreement with findings of previous radiographic studies. Application of force to the humeral head by an examiner was associated with as much as 6 mm of anterior translation and 13 mm of posterior translation. CONCLUSION Dynamic MR imaging of the glenohumeral joint is possible over a wide range of physiologic motion in vertically open systems. Use of an MR tracking coil enabled accurate tracking of the anatomy of interest. These preliminary measurements of normal glenohumeral motion patterns begin to establish normal ranges of motion and constitute a necessary first step in characterizing pathologic motion in patients with common clinical problems such as instability and impingement.
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Affiliation(s)
- C F Beaulieu
- Department of Radiology, Stanford University Medical Center, CA 94305, USA
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45
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Pearle AD, Daniel BL, Bergman AG, Beaulieu CF, Lang P, Dumoulin CL, Darrow RD, Norbash AM, Napper CL, Hurtak W, Butts K. Joint motion in an open MR unit using MR tracking. J Magn Reson Imaging 1999; 10:8-14. [PMID: 10398972 DOI: 10.1002/(sici)1522-2586(199907)10:1<8::aid-jmri2>3.0.co;2-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A system for active scan plane guidance during kinematic magnetic resonance (MR) examination of joint motion was developed utilizing an external tracking coil and MR tracking software. In a phantom study and during upright, weight-bearing, physiologic knee flexion, the external tracking coil maintained the scan plane through desired structures. Thus, MR tracking provides a robust method to guide the scan plane during MR imaging of active joint motion.
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Affiliation(s)
- A D Pearle
- Department of Diagnostic Radiology, Stanford University School of Medicine, California 94305, USA
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Aoki S, Nanbu A, Araki T, Ma X, Araki T, Kumagai H, Dumoulin CL, Darrow RD, Shimazu N, Tsukamoto T, Moriya H, Nakajima H. Active MR tracking on a 0.2 Tesla MR imager. Radiat Med 1999; 17:251-7. [PMID: 10440117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/13/2023]
Abstract
An active MR tracking system was implemented on a 0.2 Tesla open MRI system. Interventional devices with receive-only microcoils at their tips were developed and investigated on the scanner. Microcoils having a diameter of about 1 mm and 20 turns were found to provide sufficient signal-to-noise ratios for stable tracking. Positional accuracy and precision were found to be acceptable under practical conditions. Simulation of MR-guided biopsy using biplane images with tracking was performed in a gelatin phantom and dog livers. Successful tracking of catheters with integrated microcoils was also demonstrated in the aorta and IVC of live dogs.
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Affiliation(s)
- S Aoki
- Department of Radiology, Yamanashi Medical University, Nakakoma-gun, Japan
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47
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Wildermuth S, Dumoulin CL, Pfammatter T, Maier SE, Hofmann E, Debatin JF. MR-guided percutaneous angioplasty: assessment of tracking safety, catheter handling and functionality. Cardiovasc Intervent Radiol 1998; 21:404-10. [PMID: 9853147 DOI: 10.1007/s002709900288] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE Magnetic resonance (MR)-guided percutaneous vascular interventions have evolved to a practical possibility with the advent of open-configuration MR systems and real-time tracking techniques. The purpose of this study was to assess an MR-tracking percutaneous transluminal angioplasty (PTA) catheter with regard to its safety profile and functionality. METHODS Real-time, biplanar tracking of the PTA catheter was made possible by incorporating a small radiofrequency (RF) coil in the catheter tip and connecting it to a coaxial cable embedded in the catheter wall. To evaluate potentially hazardous thermal effects due to the incorporation of the coil, temperature measurements were performed within and around the coil under various scanning and tracking conditions at 1.5 Tesla (T). Catheter force transmission and balloon-burst pressure of the MR-tracking PTA catheter were compared with those of a standard PTA catheter. The dilatative capability of the angioplasty balloon was assessed in vitro as well as in vivo, in an isolated femoral artery segment in a swine. RESULTS The degree of heating at the RF coil was directly proportional to the power of the RF pulses. Heating was negligible with MR tracking, conventional spin-echo and low-flip gradient-echo sequences. Sequences with higher duty cycles, such as fast spin echo, produced harmful heating effects. Force transmission of the MR-tracking PTA catheter was slightly inferior to that of the standard PTA catheter, while balloon-burst pressures were similar to those of conventional catheters. The MR-tracking PTA catheter functioned well both in vitro and in vivo. CONCLUSION The in vivo use of an MR-tracking PTA catheter is safe under most scanning conditions.
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Affiliation(s)
- S Wildermuth
- Institute of Diagnostic Radiology, University Hospital Zürich, Switzerland
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48
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Abstract
The acquisition of complete three-dimensional (3D), segmented gradient-echo data sets to visualize the coronary arteries can be both time consuming and sensitive to motion, even with use of multiple breath-holding or respiratory gating. An alternate hybrid approach is demonstrated here, in which real-time interactive imaging is first used to locate an optimal oblique coronary scan plane. Then, a limited number of contiguous slices are acquired around that plane within a breath-hold with use of two-dimensional (2D) segmented gradient-echo imaging. Dual inversion nulling is used to suppress fat and myocardium. Finally, if needed, a limited reformat of the data is performed to produce images from relatively long sections of the coronaries. This approach yields relatively rapid visualization of portions of the coronary tree. Several different methods are compared for interactively moving the scan plane.
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Affiliation(s)
- C J Hardy
- GE Corporate Research and Development, Schenectady, New York 12301, USA
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49
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Erhart P, Ladd ME, Steiner P, Heske N, Dumoulin CL, Debatin JF. Tissue-independent MR tracking of invasive devices with an internal signal source. Magn Reson Med 1998; 39:279-84. [PMID: 9469711 DOI: 10.1002/mrm.1910390215] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
An improved MR tracking coil design is described that provides more robust tracking performance. It is shown theoretically and experimentally that a coil equipped with an internal spin source increases the signal-to-noise ratio in comparison to a coil system without internal source. The tracking behavior is stable even in air, which is important for laparoscopic work, in which the device has to be placed inside the inflated abdomen. Two types of coil windings were tested: one with the windings perpendicular to the coil axis and the other one with the windings tilted relative to this axis. The experiments showed no significant effect on the signal-to-noise ratio between the two types. The improved MR-tracking coil design with internal source was successfully used in cholecystostomies and in laparoscopic interventions; both procedures were performed on swine.
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Affiliation(s)
- P Erhart
- University Hospital, Zürich, Switzerland
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50
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Ladd ME, Zimmermann GG, McKinnon GC, von Schulthess GK, Dumoulin CL, Darrow RD, Hofmann E, Debatin JF. Visualization of vascular guidewires using MR tracking. J Magn Reson Imaging 1998; 8:251-3. [PMID: 9500289 DOI: 10.1002/jmri.1880080142] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
MR tracking of a vascular guidewire sized for a .035-inch (.89-mm) catheter lumen was performed. The guidewire was actively tracked by incorporation of a miniature radiofrequency (RF) receive coil built into its tip. After in vitro validation, simultaneous tracking of the guidewire and a catheter was performed in the aortic and abdominal vessels of a swine at 1.5 T. The ability to track such a small device and the ability to simultaneously track multiple devices are significant steps towards vascular interventions under MR guidance.
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Affiliation(s)
- M E Ladd
- Department of Radiology, University Hospital Zürich, Switzerland.
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