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Wink C, Ferrazzi G, Bassenge JP, Flassbeck S, Schmidt S, Schaeffter T, Schmitter S. 4D flow imaging with 2D‐selective excitation. Magn Reson Med 2019; 82:886-900. [DOI: 10.1002/mrm.27769] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 02/27/2019] [Accepted: 03/20/2019] [Indexed: 01/18/2023]
Affiliation(s)
- Clarissa Wink
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Giulio Ferrazzi
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Jean Pierre Bassenge
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
- Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a Joint Cooperation between the Charité Medical Faculty and the Max‐Delbrueck Center for Molecular Medicine Berlin Germany
| | - Sebastian Flassbeck
- Medical Physics in Radiology German Cancer Research Center (DKFZ) Heidelberg Germany
- Faculty of Physics and Astronomy Heidelberg University Heidelberg Germany
| | - Simon Schmidt
- Medical Physics in Radiology German Cancer Research Center (DKFZ) Heidelberg Germany
- Faculty of Physics and Astronomy Heidelberg University Heidelberg Germany
| | - Tobias Schaeffter
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
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2
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Bezuidenhout AF, Khatami D, Heilman CB, Kasper EM, Patz S, Madan N, Zhao Y, Bhadelia RA. Relationship between Cough-Associated Changes in CSF Flow and Disease Severity in Chiari I Malformation: An Exploratory Study Using Real-Time MRI. AJNR Am J Neuroradiol 2018; 39:1267-1272. [PMID: 29748208 DOI: 10.3174/ajnr.a5670] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2018] [Accepted: 03/21/2018] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Currently no quantitative objective test exists to determine disease severity in a patient with Chiari I malformation. Our aim was to correlate disease severity in symptomatic patients with Chiari I malformation with cough-associated changes in CSF flow as measured with real-time MR imaging. MATERIALS AND METHODS Thirteen symptomatic patients with Chiari I malformation (tonsillar herniation of ≥5 mm) were prospectively studied. A real-time, flow-sensitized pencil-beam MR imaging scan was used to measure CSF stroke volume during rest and immediately following coughing and relaxation periods (total scan time, 90 seconds). Multiple posterior fossa and craniocervical anatomic measurements were also obtained. Patients were classified into 2 groups by neurosurgeons blinded to MR imaging measurements: 1) nonspecific Chiari I malformation (5/13)-Chiari I malformation with nonspecific symptoms like non-cough-related or mild occasional cough-related headache, neck pain, dizziness, paresthesias, and/or trouble swallowing; 2) specific Chiari I malformation (8/13)-patients with Chiari I malformation with specific symptoms and/or objective findings like severe cough-related headache, myelopathy, syringomyelia, and muscle atrophy. The Spearman correlation was used to determine correlations between MR imaging measurements and disease severity, and both groups were also compared using a Mann-Whitney U test. RESULTS There was a significant negative correlation between the percentage change in CSF stroke volume (resting to postcoughing) and Chiari I malformation disease severity (R = 0.59; P = .03). Mann-Whitney comparisons showed the percentage change in CSF stroke volume (resting to postcoughing) to be significantly different between patient groups (P = .04). No other CSF flow measurement or anatomic measure was significantly different between the groups. CONCLUSIONS Our exploratory study suggests that assessment of CSF flow response to a coughing challenge has the potential to become a valuable objective noninvasive test for clinical assessment of disease severity in patients with Chiari I malformation.
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Affiliation(s)
| | - D Khatami
- From the Departments of Radiology (A.F.B., D.K., R.A.B.)
| | | | - E M Kasper
- Neurosurgery (E.M.K.), Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - S Patz
- Department of Radiology (S.P.), Brigham and Woman's Hospital, Boston, Massachusetts
| | - N Madan
- Radiology (N.M.), Tufts Medical Center, Boston, Massachusetts
| | - Y Zhao
- Philips Healthcare (Y.Z.), Boston, Massachusetts
| | - R A Bhadelia
- From the Departments of Radiology (A.F.B., D.K., R.A.B.)
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3
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Celicanin Z, Manasseh G, Petrusca L, Scheffler K, Auboiroux V, Crowe LA, Hyacinthe JN, Natsuaki Y, Santini F, Becker CD, Terraz S, Bieri O, Salomir R. Hybrid ultrasound-MR guided HIFU treatment method with 3D motion compensation. Magn Reson Med 2017; 79:2511-2523. [PMID: 28944490 DOI: 10.1002/mrm.26897] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2017] [Revised: 08/10/2017] [Accepted: 08/11/2017] [Indexed: 01/16/2023]
Abstract
PURPOSE Treatments using high-intensity focused ultrasound (HIFU) in the abdominal region remain challenging as a result of respiratory organ motion. A novel method is described here to achieve 3D motion-compensated ultrasound (US) MR-guided HIFU therapy using simultaneous ultrasound and MRI. METHODS A truly hybrid US-MR-guided HIFU method was used to plan and control the treatment. Two-dimensional ultrasound was used in real time to enable tracking of the motion in the coronal plane, whereas an MR pencil-beam navigator was used to detect anterior-posterior motion. Prospective motion compensation of proton resonance frequency shift (PRFS) thermometry and HIFU electronic beam steering were achieved. RESULTS The 3D prospective motion-corrected PRFS temperature maps showed reduced intrascan ghosting artifacts, a high signal-to-noise ratio, and low geometric distortion. The k-space data yielded a consistent temperature-dependent PRFS effect, matching the gold standard thermometry within approximately 1°C. The maximum in-plane temperature elevation ex vivo was improved by a factor of 2. Baseline thermometry acquired in volunteers indicated reduction of residual motion, together with an accuracy/precision of near-harmonic referenceless PRFS thermometry on the order of 0.5/1.0°C. CONCLUSIONS Hybrid US-MR-guided HIFU ablation with 3D motion compensation was demonstrated ex vivo together with a stable referenceless PRFS thermometry baseline in healthy volunteer liver acquisitions. Magn Reson Med 79:2511-2523, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Zarko Celicanin
- Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Gibran Manasseh
- Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Lorena Petrusca
- Hepatobiliary and Pancreatic Interventional Radiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Klaus Scheffler
- MRC Department, MPI for Biological Cybernetics, Tübingen, Germany.,Department of Biomedical Magnetic Resonance, University of Tübingen, Tübingen, Germany
| | - Vincent Auboiroux
- Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Clinatec/LETI/CEA, 38054, Grenoble, France
| | - Lindsey A Crowe
- Radiology Department, University Hospitals of Geneva, Geneva, Switzerland
| | - Jean-Noel Hyacinthe
- Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,School of Health Sciences, HES-SO, University of Applied Sciences and Arts of Western Switzerland, Geneva, Switzerland
| | | | - Francesco Santini
- Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Christoph D Becker
- Hepatobiliary and Pancreatic Interventional Radiology, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Radiology Department, University Hospitals of Geneva, Geneva, Switzerland
| | - Sylvain Terraz
- Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Radiology Department, University Hospitals of Geneva, Geneva, Switzerland
| | - Oliver Bieri
- Department of Radiology, Division of Radiological Physics, University of Basel Hospital, Basel, Switzerland.,Department of Biomedical Engineering, University of Basel, Basel, Switzerland
| | - Rares Salomir
- Image Guided Interventions Laboratory, Faculty of Medicine, University of Geneva, Geneva, Switzerland.,Radiology Department, University Hospitals of Geneva, Geneva, Switzerland
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4
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Bhadelia RA, Patz S, Heilman C, Khatami D, Kasper E, Zhao Y, Madan N. Cough-Associated Changes in CSF Flow in Chiari I Malformation Evaluated by Real-Time MRI. AJNR Am J Neuroradiol 2015; 37:825-30. [PMID: 26705321 DOI: 10.3174/ajnr.a4629] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2015] [Accepted: 10/27/2015] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Invasive pressure studies have suggested that CSF flow across the foramen magnum may transiently decrease after coughing in patients with symptomatic Chiari I malformation. The purpose of this exploratory study was to demonstrate this phenomenon noninvasively by assessing CSF flow response to coughing in symptomatic patients with Chiari I malformation by using MR pencil beam imaging and to compare the response with that in healthy participants. MATERIALS AND METHODS Eight symptomatic patients with Chiari I malformation and 6 healthy participants were studied by using MR pencil beam imaging with a temporal resolution of ∼50 ms. Patients and healthy participants were scanned for 90 seconds (without cardiac gating) to continuously record cardiac cycle-related CSF flow waveforms in real-time during resting, coughing, and postcoughing periods. CSF flow waveform amplitude, CSF stroke volume, and CSF flow rate (CSF Flow Rate = CSF Stroke Volume × Heart Rate) in the resting and immediate postcoughing periods were determined and compared between patients and healthy participants. RESULTS There was no significant difference in CSF flow waveform amplitude, CSF stroke volume, and the CSF flow rate between patients with Chiari I malformation and healthy participants during rest. However, immediately after coughing, a significant decrease in CSF flow waveform amplitude (P < .001), CSF stroke volume (P = .001), and CSF flow rate (P = .001) was observed in patients with Chiari I malformation but not in the healthy participants. CONCLUSIONS Real-time MR imaging noninvasively showed a transient decrease in CSF flow across the foramen magnum after coughing in symptomatic patients with Chiari I malformation, a phenomenon not seen in healthy participants. Our results provide preliminary evidence that the physiology-based imaging method used here has the potential to be an objective clinical test to differentiate symptomatic from asymptomatic patients with Chiari I malformation.
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Affiliation(s)
- R A Bhadelia
- From the Department of Radiology (R.A.B., D.K.), Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - S Patz
- Department of Radiology (S.P.), Brigham and Women's Hospital, Boston, Massachusetts
| | | | - D Khatami
- From the Department of Radiology (R.A.B., D.K.), Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - E Kasper
- Department of Neurosurgery (E.K.), Beth Israel Deaconess Medical Center, Boston, Massachusetts
| | - Y Zhao
- Phillips Healthcare (Y.Z.), Boston, Massachusetts
| | - N Madan
- Radiology (N.M.), Tufts Medical Center, Boston, Massachusetts
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5
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Celicanin Z, Auboiroux V, Bieri O, Petrusca L, Santini F, Viallon M, Scheffler K, Salomir R. Real-time method for motion-compensated MR thermometry and MRgHIFU treatment in abdominal organs. Magn Reson Med 2013; 72:1087-95. [DOI: 10.1002/mrm.25017] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 09/27/2013] [Accepted: 10/07/2013] [Indexed: 11/06/2022]
Affiliation(s)
- Zarko Celicanin
- Department of Radiology, Division of Radiological Physics; University of Basel Hospital; Basel Switzerland
- MRC Department; MPI for Biological Cybernetics; Tübingen Germany
| | | | - Oliver Bieri
- Department of Radiology, Division of Radiological Physics; University of Basel Hospital; Basel Switzerland
| | - Lorena Petrusca
- Radiology Department; University of Geneva; Geneva Switzerland
| | - Francesco Santini
- Department of Radiology, Division of Radiological Physics; University of Basel Hospital; Basel Switzerland
| | - Magalie Viallon
- Radiology Department; University of Geneva; Geneva Switzerland
| | - Klaus Scheffler
- MRC Department; MPI for Biological Cybernetics; Tübingen Germany
- Department of Biomedical Magnetic Resonance; University of Tübingen; Tübingen Germany
| | - Rares Salomir
- Radiology Department; University of Geneva; Geneva Switzerland
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6
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Bhadelia RA, Madan N, Zhao Y, Wagshul ME, Heilman C, Butler JP, Patz S. Physiology-based MR imaging assessment of CSF flow at the foramen magnum with a valsalva maneuver. AJNR Am J Neuroradiol 2013; 34:1857-62. [PMID: 23620074 DOI: 10.3174/ajnr.a3509] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE MR imaging is currently not used to evaluate CSF flow changes due to short-lasting physiological maneuvers. The purpose of this study was to evaluate the ability of MR imaging to assess the CSF flow response to a Valsalva maneuver in healthy participants. MATERIALS AND METHODS A cardiac-gated fast cine-PC sequence with ≤15-second acquisition time was used to assess CSF flow in 8 healthy participants at the foramen magnum at rest, during, and immediately after a controlled Valsalva maneuver. CSF mean displacement volume VCSF during the cardiac cycle and CSF flow waveform App were determined. A work-in-progress real-time pencil-beam imaging method with temporal resolution ≤56 ms was used to scan 2 participants for 90 seconds during which resting, Valsalva, and post-Valsalva CSF flow, respiration, and HR were continuously recorded. Results were qualitatively compared with invasive craniospinal differential pressure measurements from the literature. RESULTS Both methods showed 1) a decrease from baseline in VCSF and App during Valsalva and 2) an increase in VCSF and App immediately after Valsalva compared with values measured both at rest and during Valsalva. Whereas fast cine-PC produced a single CSF flow waveform that is an average over many cardiac cycles, pencil-beam imaging depicted waveforms for each heartbeat and was able to capture many dynamic features of CSF flow, including transients synchronized with the Valsalva maneuver. CONCLUSIONS Both fast cine-PC and pencil-beam imaging demonstrated expected changes in CSF flow with Valsalva maneuver in healthy participants. The real-time capability of pencil-beam imaging may be necessary to detect Valsalva-related transient CSF flow obstruction in patients with pathologic conditions such as Chiari I malformation.
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Affiliation(s)
- R A Bhadelia
- Department of Radiology, Beth Israel Deaconess Medical Center, Boston, Massachusetts
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7
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Auboiroux V, Petrusca L, Viallon M, Goget T, Becker CD, Salomir R. Ultrasonography-based 2D motion-compensated HIFU sonication integrated with reference-free MR temperature monitoring: a feasibility studyex vivo. Phys Med Biol 2012; 57:N159-71. [DOI: 10.1088/0031-9155/57/10/n159] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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8
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Köhler MO, Denis de Senneville B, Quesson B, Moonen CT, Ries M. Spectrally selective pencil-beam navigator for motion compensation of MR-guided high-intensity focused ultrasound therapy of abdominal organs. Magn Reson Med 2011; 66:102-11. [DOI: 10.1002/mrm.22784] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 11/17/2010] [Accepted: 12/02/2010] [Indexed: 12/17/2022]
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9
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Ries M, de Senneville BD, Roujol S, Berber Y, Quesson B, Moonen C. Real-time 3D target tracking in MRI guided focused ultrasound ablations in moving tissues. Magn Reson Med 2010; 64:1704-12. [DOI: 10.1002/mrm.22548] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Revised: 05/19/2010] [Accepted: 05/26/2010] [Indexed: 01/15/2023]
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10
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Klessen C, Asbach P, Kroencke TJ, Fischer T, Warmuth C, Stemmer A, Hamm B, Taupitz M. Magnetic resonance imaging of the upper abdomen using a free-breathing T2-weighted turbo spin echo sequence with navigator triggered prospective acquisition correction. J Magn Reson Imaging 2005; 21:576-82. [PMID: 15834908 DOI: 10.1002/jmri.20293] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
PURPOSE To evaluate a free-breathing navigator triggered T2-weighted turbo spin-echo sequence with prospective acquisition correction (T2w-PACE-TSE) for MRI of the upper abdomen in comparison to a conventional T2-weighted TSE (T2w-CTSE), a single-shot TSE (T2w-HASTE), and a T1-weighted gradient-echo sequence (T1w-FLASH). MATERIALS AND METHODS A total of 40 consecutive patients were examined at 1.5 T using free-breathing T2w-PACE-TSE, free-breathing T2w-CTSE, and breath-hold T2w-HASTE and T1w-FLASH acquisition. Images were evaluated qualitatively by three radiologists regarding motion artifacts, liver-spleen contrast, depiction of intrahepatic vessels, the pancreas and the adrenal glands, and overall image quality on a four-point scale. Quantitative analysis of the liver-spleen contrast was performed. RESULTS Depiction and sharpness of intrahepatic vessels were rated significantly better (P < 0.01) using T2w-PACE-TSE compared to T2w-CTSE and T2w-HASTE sequences. Significantly higher contrast values were measured for T2w-PACE-TSE images compared to T2w-CTSE, T2w-HASTE, and T1w-FLASH images (P < 0.01). Mean examination time of the T2w-PACE-TSE was 7.91 minutes, acquisition time of the T2w-CTSE sequence was 4.52 minutes. CONCLUSION Prospective acquisition correction is an efficient method for reducing respiratory movement artifacts in T2w-TSE imaging of the upper abdomen. Compared to T2w-CTSE and T2w-HASTE sequences recognition of anatomical details and contrast can be significantly improved.
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Affiliation(s)
- Christian Klessen
- Department of Radiology, Charité-Universitary Medicine Berlin, Campus Charité Mitte, Humboldt-University of Berlin, Berlin, Germany.
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11
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Davies NP, Jezzard P. Selective arterial spin labeling (SASL): perfusion territory mapping of selected feeding arteries tagged using two-dimensional radiofrequency pulses. Magn Reson Med 2003; 49:1133-42. [PMID: 12768592 DOI: 10.1002/mrm.10475] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
To date, most perfusion magnetic resonance imaging (MRI) methods using arterial spin labeling (ASL) have employed slab-selective inversion pulses or continuous labeling within a plane in order to obtain maps derived from all major blood vessels entering the brain. However, there is great potential for gaining additional information on the territories perfused by the major vessels if individual feeding arteries could be tagged. This study demonstrates noninvasive arterial perfusion territory maps obtained using two-dimensional (2D) selective inversion pulses. This method is designated "selective ASL" (SASL). The SASL method was used to tag the major arteries below the circle of Willis. A combination of 2D selective tagging and multislice readout allows perfusion territories to be clearly visualized, with likely applications to cerebrovascular disease and stroke.
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Affiliation(s)
- Nigel P Davies
- FMRIB Center, Department of Clinical Neurology, University of Oxford, John Radcliffe Hospital, UK.
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12
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Nehrke K, Börnert P, Groen J, Smink J, Böck JC. On the performance and accuracy of 2D navigator pulses. Magn Reson Imaging 1999; 17:1173-81. [PMID: 10499679 DOI: 10.1016/s0730-725x(99)00043-0] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The purpose of this study was to investigate and to optimize the performance of two-dimensional spatially selective excitation pulses used for navigator applications on a clinical scanner. The influence of gradient imperfections, off-resonance effects, and incomplete k-space covering on the pencil beam-shaped spatial excitation profile of the 2D RF pulse was studied. The studies involved experiments performed on phantoms and in vivo. In addition, simulations were carried out by numerical integration of the Bloch equations. The accuracy of positioning of the pencil beam was increased by a factor of three by employing a simple correction scheme for the compensation of gradient distortions. The spatial selectivity of the 2D RF pulse was improved by taking sampling density corrections into account. The 2D RF pulse performance was found to be sufficient to monitor the diaphragm motion even at moderate gradient strength. For applications, where a high spatial resolution is required or a less characteristic contrast is present a strong gradient system is recommended.
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Affiliation(s)
- K Nehrke
- Department of Radiology, Medical Faculty of Charité of the Humboldt University of Berlin, Campus Virchow-Clinic, Germany.
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13
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Stuber M, Botnar RM, Danias PG, Kissinger KV, Manning WJ. Submillimeter three-dimensional coronary MR angiography with real-time navigator correction: comparison of navigator locations. Radiology 1999; 212:579-87. [PMID: 10429721 DOI: 10.1148/radiology.212.2.r99au50579] [Citation(s) in RCA: 200] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Three-dimensional free-breathing coronary magnetic resonance angiography was performed in eight healthy volunteers with use of real-time navigator technology. Images acquired with the navigator localized at the right hemidiaphragm and at the left ventricle were objectively compared. The diaphragmatic navigator was found to be superior for vessel delineation of middle to distal portions of the coronary arteries.
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Affiliation(s)
- M Stuber
- Cardiovascular Division, Beth Israel Deaconess Medical Center, Boston, MA, USA.
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Abstract
The effect of in-plane motion on the point spread function (velocity PSF) in spiral imaging is studied experimentally and derived mathematically and is shown to consist of a smoothed, trailing edge and fringes around the leading edge. The velocity PSF remains largely in phase with the static PSF, consistent with the absence of signal loss by motion-related phase shifts in central k space. However, single-shot spiral imaging gives no clear improvement in complex and turbulent flow signal uniformity compared with echo-planar imaging with early, central k-space acquisition, which requires explanation given the spiral's earlier coverage of central k space. Alternate leading-edge fringes of the spiral's velocity PSF are in antiphase to the source, and cancellation may occur when these overlap other in-phase signals. Phase variations toward peripheral k space in turbulent flow also cause distortion. It is concluded that spiral imaging may lose complex and turbulent flow signals because of complex PSF distortion.
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Affiliation(s)
- P D Gatehouse
- Magnetic Resonance Unit, Royal Brompton Hospital, Chelsea, London, United Kingdom.
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15
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Abstract
The information about the current respiratory motion state used in conventional gating to accept or to reject data can further be used to obtain motion statistics during an MR scan. This can serve to monitor changes in the respiratory pattern of the patient by comparison of motion statistics subsequently obtained during scanning. Two indicators are introduced: first a parameter that registers changes of the motion pattern, and second an indicator that expresses the quality of the data set already obtained. Based on these indicators, the gating algorithm decides to change gating parameters during scanning automatically. This new approach has the potential to increase the scan efficiency considerably without the need of operator interaction and/or significant patient cooperation. The basic principle is described and illustrated for the motion-adapted gating technique, and first in vivo results are presented to underline the feasibility of this concept.
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Affiliation(s)
- R Sinkus
- The Philips Research Laboratories, Hamburg, Germany
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16
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St Lawrence K, Lee TY, Henkelman M. Spatial localization combining projection presaturation with a two-dimensional excitation pulse. Magn Reson Med 1998; 40:944-7. [PMID: 9840842 DOI: 10.1002/mrm.1910400623] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Single-shot spatial localization of short T1 nuclei was achieved by outer volume suppression with projection presaturation followed by selective excitation of the desired volume with a two-dimensional (2D) pulse. After the projection, presaturation with a 2D pulse avoided signal contamination from magnetization regrowth in the outer volume, whereas preceding the 2D pulse with projection presaturation reduced any unwanted excitation in the outer volume caused by the 2D pulse. The improvement in outer volume suppression achieved by combining these two techniques was demonstrated by images collected after the application of projection presaturation alone, a 2D pulse alone, and the two combined.
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Affiliation(s)
- K St Lawrence
- Department of Radiology and the Lawson Research Institute, St. Joseph's Health Centre, London, Ontario, Canada
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17
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Börnert P, Aldefeld B. On spatially selective RF excitation and its analogy with spiral MR image acquisition. MAGMA (NEW YORK, N.Y.) 1998; 7:166-78. [PMID: 10050943 DOI: 10.1007/bf02591334] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The basic principles of the design of spatially selective RF pulses are described, and their analogy with MR image acquisition and reconstruction is shown. The paper focuses on RF-pulse design and imaging schemes in which spiral k-space trajectories are used. The sensitivity of RF excitation to gradient-system imperfections and to spatially varying off-resonance are analyzed, and suitable measures of correction are discussed. The spatial resolution obtainable with selective RF pulses and the consequences of the linearity of the pulse-design problem are examined. Phantom experiments showing the performance of multidimensional spatially selective RF pulses further illustrate the analogy with MR image acquisition.
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Affiliation(s)
- P Börnert
- Philips Research Laboratories, Hamburg, Germany
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18
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Meyerand ME, Moritz CH, Wong EC. Single-shot, motion insensitive cardiac imaging on a standard clinical system. Magn Reson Med 1998; 40:930-3. [PMID: 9840839 DOI: 10.1002/mrm.1910400620] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The overall goal of this study was the development and application of a less motion sensitive, single-shot MRI technique for use on a standard clinical system in a dynamic imaging setting, such as cardiac scanning. Time encoding, a single-shot line scanning technique, has been used to produce single-shot, small field-of-view cardiac images without the use of presaturation pulses. The major advantages of this method are: (1) as a line scanning technique, time encoding is minimally sensitive to motion when compared with 2D Fourier methods, and (2) aliasing will not occur if the object being imaged extends beyond the field of view.
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Affiliation(s)
- M E Meyerand
- Biophysics Research Institute, Medical College of Wisconsin, Milwaukee, USA
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Weiger M, Börnert P, Proksa R, Schäffter T, Haase A. Motion-adapted gating based on k-space weighting for reduction of respiratory motion artifacts. Magn Reson Med 1997; 38:322-33. [PMID: 9256114 DOI: 10.1002/mrm.1910380223] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A new modified type of gating is presented that shows the ability to reduce the total scan time with almost conserved image quality compared with conventional gating. This new motion-adapted gating approach is based on a k-space-dependent gating threshold function. MR data acquired are only accepted if the motion-induced displacements measured from a reference position are below the chosen gating threshold function. During the MR measurement the scanner analyses respiratory motion decides in real-time which data in k-space could be measured according to the gating threshold function and performs data acquisition. In the present paper the approach will be described and discussed. Simulations based on in vivo data and initial in vivo experiments are presented to compare different variants of the new approach mutually and to the conventional technique. The analysis given is focused on spin warp type sequences, which are the best candidates for this approach.
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Affiliation(s)
- M Weiger
- Physikalisches Institut, Universität Würzburg, Germany
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21
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Urchuk SN, Fremes SE, Plewes DB. In vivo validation of MR pulse pressure measurement in an aortic flow model: preliminary results. Magn Reson Med 1997; 38:215-23. [PMID: 9256100 DOI: 10.1002/mrm.1910380209] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
MR imaging experiments were conducted to investigate the feasibility of estimating vascular pulse pressure waveforms from measurements of blood flow rates and vessel cross-sectional area. Blood flow waveforms were measured in the aorta's of three 25-30-kg pigs at multiple imaging sections using phase-contrast velocity imaging. Estimates of pulse pressure were derived from these data by evaluating a model characterizing the relationship between pressure, flow, and the cross-sectional area of a vessel segment. Comparisons between the MR-derived estimates of pressure and those obtained from a micromanometer pressure catheter indicate that accurate measurements (mean error +/- SD = 8.2 +/- 3.4, n = 6) can be obtained using conventional velocity imaging techniques. Optimization of the method will require the application of rapid imaging techniques and the development of strategies for obtaining a more localized measurement. With these improvements, our results suggest that MR-based measurement of pulse pressure and related elastic parameters is feasible.
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Affiliation(s)
- S N Urchuk
- Department of Medical Biophysics, Sunnybrook Health Science Centre, University of Toronto, Ontario, Canada
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22
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Abstract
MRI of the abdomen has been under development for well over a decade. In the past, considerable work was directed toward identification and suppression of the artifacts caused by motion. However, within the last several years, image quality has further improved, particularly as various fast-scan techniques have been adapted for abdominal imaging. The purpose of this work is to review these technical developments. Specific methods include adaptation of the acquisition time to breath-holding, acquisition over multiple respiratory cycles, adjustment of the contrast of various sequences, and development of more sensitive receiver coils and faster gradient systems. Opportunities for future development are also identified, including improved slice sampling, increased in-plane spatial resolution, real-time means for monitoring respiration, and expanded applications. As these technical advances are implemented, it is expected that the overall sensitivity and specificity of abdominal MRI will further improve.
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Affiliation(s)
- S J Riederer
- Magnetic Resonance Laboratory, Mayo Clinic, Rochester, MN 55905, USA
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23
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Wigström L, Lindström L, Sjöqvist L, Thuomas KA, Wranne B. M-mode magnetic resonance imaging: a new modality for assessing cardiac function. CLINICAL PHYSIOLOGY (OXFORD, ENGLAND) 1995; 15:397-407. [PMID: 7554773 DOI: 10.1111/j.1475-097x.1995.tb00529.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Magnetic resonance imaging (MRI) studies of the heart have been used for some years, but there are few tools available to quantify cardiac motion. A method has been developed that creates an M-mode MRI image, analogous to the one used in echocardiography, to display motion along a line as a function of time. The M-mode image is created from MRI images acquired with an ordinary gradient echo cine sequence. In a cinematographic display of the images, a cursor line can be positioned in order to determine the orientation of the measurement. A resampling algorithm then calculates the appearance of the M-mode image along the cursor line. The MRI method has been compared to echocardiographic M-mode in a phantom study and by measuring mitral and tricuspid annulus motion in 20 normal subjects. The phantom study showed no significant differences between MRI and echocardiographic M-mode measurements (difference < 1 mm). The annulus motion exhibits a similar pattern using both methods and the measured amplitudes are in close agreement. M-mode MRI provides similar information to echocardiography, but the cursor line can be placed arbitrarily within the image plane and the method is thus not limited to certain acoustic windows. This makes M-mode MRI a promising technique for assessing cardiac motion.
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Affiliation(s)
- L Wigström
- Department of Clinical Physiology, Faculty of Health Sciences, Linköping University, Sweden
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24
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Abstract
MRI has developed very rapidly and now provides anatomic and functional information in cases of valvular heart disease. MRI has several important attributes that make it advantageous for the evaluation of valvular heart disease. First, the natural contrast between flowing blood and surrounding cardiovascular structures provides sharp delineation of endocardial and epicardial borders without the need for contrast media. This feature in combination with the essential three-dimensional nature of this imaging technique allows precise quantification of cardiac volumes, function, and mass without the use of any assumed formulas or geometric models. Second, blood flow-sensitive GRE techniques are able to identify areas of turbulent flow caused by stenotic or regurgitant valves. With this technique regurgitant jets can be visualized and semiquantitative grading can be performed as with color Doppler. Third, recently developed velocity-encoded techniques permit measurements of blood flow velocities across stenotic native and prosthetic heart valves and retrograde flow caused by regurgitation. Moreover, the close interstudy reproducibility of measurements of cardiac dimensions and valvular regurgitation suggests a role in assessing the effect of therapeutic interventions.
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Affiliation(s)
- S Globits
- Department of Radiology, University of California, San Francisco
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25
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Hardy CJ, Bolster BD, McVeigh ER, Adams WJ, Zerhouni EA. A one-dimensional velocity technique for NMR measurement of aortic distensibility. Magn Reson Med 1994; 31:513-20. [PMID: 8015404 PMCID: PMC2570027 DOI: 10.1002/mrm.1910310507] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A technique is presented for rapidly and noninvasively determining aortic distensibility, by NMR measurement of wave velocity in the aorta. A two-dimensional NMR selective-excitation pulse is used to repeatedly excite a cylinder of magnetization in the aorta, with magnetization read out along the cylinder axis each time. A toggled bipolar flow-encoding pulse is applied prior to readout, to produce a non-dimensional phase-contrast flow image. Cardiac gating and data interleaving are employed to improve the effective time resolution to 2 ms. Wave velocities are determined from the slope of the leading edge of flow measured on the resulting M-mode velocity image. The technique is sensitive over a range of distensibilities from 10(-6) to 10(-3) m s2/kg. The average value in the descending thoracic aorta in seven normal subjects was found to be 4.8 x 10(-5) m s2/kg, with a significant inverse correlation with age.
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Affiliation(s)
- C J Hardy
- GE Corporate Research and Development Center, Schenectady, New York 12301
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26
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Hardy CJ, Darrow RD, Nieters EJ, Roemer PB, Watkins RD, Adams WJ, Hattes NR, Maier JK. Real-time acquisition, display, and interactive graphic control of NMR cardiac profiles and images. Magn Reson Med 1993; 29:667-73. [PMID: 8505903 DOI: 10.1002/mrm.1910290514] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A highly interactive MRI scanner interface has been developed that allows, for the first time, real-time graphic control of one-dimensional (1D) and two-dimensional (2D) cardiac MRI exams. The system comprises a Mercury array processor (AP) in a Sun SPARCserver with two connections to the MRI scanner, a data link that passes the NMR data directly to the AP as they are collected, and a control link that passes commands from the Sun to the scanner to redirect the imaging pulse sequence in real time. In the 1D techniques, a cylinder or "pencil" of magnetization is repeatedly excited using gradient-echo or spin-echo line-scan sequences, with the magnetization read out each time along the length of the cylinder, and a scrolling display generated on the Sun monitor. Rubber-band lines drawn on the scout image redirect the pencil or imaging slice to different locations, with the changes immediately visible in the display. M-mode imaging, 1D flow imaging, and 2D fast cardiac imaging have been demonstrated on normal volunteers using this system. This platform represents an operator-"friendly" way of directing real-time imaging of the heart.
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Affiliation(s)
- C J Hardy
- General Electric Corporate Research and Development Center, Schenectady, New York 12301
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27
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Butts K, Hangiandreou NJ, Riederer SJ. Phase velocity mapping with a real time line scan technique. Magn Reson Med 1993; 29:134-8. [PMID: 8419735 DOI: 10.1002/mrm.1910290125] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A real-time, 20-Hz, one-dimensional MR velocity imaging technique is described. A two-dimensional RF pulse excites a 3-cm diameter column. Velocity maps are formed from the phase difference between successive flow encoded and compensated acquisitions. A three-point subtraction variation provides reduced sensitivity to static spins.
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Affiliation(s)
- K Butts
- Magnetic Resonance Laboratory, Mayo Clinic, Rochester, Minnesota
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28
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Abstract
BACKGROUND Currently available noninvasive techniques for measuring blood flow velocities are constrained by limited view orientations (Doppler ultrasound) or limited time resolution (magnetic resonance imaging, MRI). We describe an MRI technique for measuring flow velocities in real time at arbitrary orientations within a cylindrical volume or "beam": V-mode nuclear magnetic resonance (NMR). METHODS AND RESULTS The technique was implemented on a standard 1.5-T clinical NMR imager with no special hardware and was tested on phantoms and human volunteers. The beam can be fired at rates up to 60 times per second, allowing measurements on a time scale that is appropriate for ungated cardiac studies. In phantoms, steady flow velocities were measured with the beam aligned along the direction of flow, and the measured velocities correlated well with the actual velocities (r > 0.99). The radial distribution of velocities in phantoms under constant flow conditions was also determined. In humans, flow of blood in the descending aortas of normal and aortic insufficiency subjects was measured. Distinctive backflow of blood because of aortic insufficiency was readily apparent. CONCLUSIONS The V-mode NMR technique is capable of acquiring clinically relevant real-time blood flow information from any desired angle of view with no attenuation at bone or air-tissue interfaces.
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Affiliation(s)
- J D Pearlman
- Department of Medicine, Massachusetts General Hospital, Boston
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