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Lillaney PV, Yang JK, Losey AD, Martin AJ, Cooke DL, Thorne BRH, Barry DC, Chu A, Stillson C, Do L, Arenson RL, Saeed M, Wilson MW, Hetts SW. Endovascular MR-guided Renal Embolization by Using a Magnetically Assisted Remote-controlled Catheter System. Radiology 2016; 281:219-28. [PMID: 27019290 DOI: 10.1148/radiol.2016152036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Purpose To assess the feasibility of a magnetically assisted remote-controlled (MARC) catheter system under magnetic resonance (MR) imaging guidance for performing a simple endovascular procedure (ie, renal artery embolization) in vivo and to compare with x-ray guidance to determine the value of MR imaging guidance and the specific areas where the MARC system can be improved. Materials and Methods In concordance with the Institutional Animal Care and Use Committee protocol, in vivo renal artery navigation and embolization were tested in three farm pigs (mean weight 43 kg ± 2 [standard deviation]) under real-time MR imaging at 1.5 T. The MARC catheter device was constructed by using an intramural copper-braided catheter connected to a laser-lithographed saddle coil at the distal tip. Interventionalists controlled an in-room cart that delivered electrical current to deflect the catheter in the MR imager. Contralateral kidneys were similarly embolized under x-ray guidance by using standard clinical catheters and guidewires. Changes in renal artery flow and perfusion were measured before and after embolization by using velocity-encoded and perfusion MR imaging. Catheter navigation times, renal parenchymal perfusion, and renal artery flow rates were measured for MR-guided and x-ray-guided embolization procedures and are presented as means ± standard deviation in this pilot study. Results Embolization was successful in all six kidneys under both x-ray and MR imaging guidance. Mean catheterization time with MR guidance was 93 seconds ± 56, compared with 60 seconds ± 22 for x-ray guidance. Mean changes in perfusion rates were 4.9 au/sec ± 0.8 versus 4.6 au/sec ± 0.6, and mean changes in renal flow rate were 2.1 mL/min/g ± 0.2 versus 1.9 mL/min/g ± 0.2 with MR imaging and x-ray guidance, respectively. Conclusion The MARC catheter system is feasible for renal artery catheterization and embolization under real-time MR imaging in vivo, and quantitative physiologic measures under MR imaging guidance were similar to those measured under x-ray guidance, suggesting that the MARC catheter system could be used for endovascular procedures with interventional MR imaging. (©) RSNA, 2016.
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Affiliation(s)
- Prasheel V Lillaney
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Jeffrey K Yang
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Aaron D Losey
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Alastair J Martin
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Daniel L Cooke
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Bradford R H Thorne
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - David C Barry
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Andrew Chu
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Carol Stillson
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Loi Do
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Ronald L Arenson
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Maythem Saeed
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Mark W Wilson
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
| | - Steven W Hetts
- From the Department of Radiology and Biomedical Imaging, University of California, San Francisco, 185 Berry St, Suite 350, Room 320, San Francisco, CA 94107-5705 (P.V.L., J.K.Y., A.D.L., A.J.M., D.L.C., B.R.H.T., C.S., L.D., R.L.A., M.S., M.W.W., S.W.H.); and Penumbra, Alameda, Calif (D.C.B., A.C.)
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Nakamura S, Nakaura T, Kidoh M, Utsunomiya D, Doi Y, Harada K, Uemura S, Yamashita Y. Timing of the hepatic arterial phase at Gd-EOB-DTPA-enhanced hepatic dynamic MRI: comparison of the test-injection and the fixed-time delay method. J Magn Reson Imaging 2013; 38:548-54. [PMID: 23744782 DOI: 10.1002/jmri.24017] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Accepted: 12/05/2012] [Indexed: 12/22/2022] Open
Abstract
PURPOSE To compare the fixed-time- and the test-injection method with respect to the image quality of hypervascular hepatocellular carcinoma (HCC) and the adequacy of timing of the hepatic arterial phase (HAP) in Gd-EOB-DTPA (EOB) enhanced MRI. MATERIALS AND METHODS We studied 63 patients with computed tomography (CT) -proven hypervascular HCC: 30 (group 1) were scanned HAP using the fixed-time delay method (protocol 1); in the other 33 (group 2), we applied the test-injection method (protocol 2). We compared the protocols with respect with tumor-to-liver contrast (TLC), contrast-to-noise-ratio (CNR), and relative enhancement of the liver and tumor (REL , RET ) during HAP. Two radiologists compared the adequacy of HAP, image contrast, image noise, and overall image quality. RESULTS Under protocol 2, TLC, CNR, and REL and RET of hypervascular HCC were significantly higher (P < 0.01). The proportion of optimal HAP was significantly higher for protocol 2 than protocol 1 (P < 0.01). The visual score of the image contrast and the overall image quality were significantly higher in group 2 than group 1 (P = 0.02 and P = 0.01, respectively). CONCLUSION At EOB-enhanced hepatic dynamic MRI, the test-injection method yielded better image quality of hypervascular HCC and improved adequacy of timing of HAP.
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Affiliation(s)
- Shinichi Nakamura
- Department of Diagnostic Radiology, Amakusa Regional Medical Center, Kumamoto, Japan.
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Saeed M, Hetts SW, English J, Wilson M. MR fluoroscopy in vascular and cardiac interventions (review). Int J Cardiovasc Imaging 2012; 28:117-37. [PMID: 21359519 PMCID: PMC3275732 DOI: 10.1007/s10554-010-9774-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 12/13/2010] [Indexed: 12/22/2022]
Abstract
Vascular and cardiac disease remains a leading cause of morbidity and mortality in developed and emerging countries. Vascular and cardiac interventions require extensive fluoroscopic guidance to navigate endovascular catheters. X-ray fluoroscopy is considered the current modality for real time imaging. It provides excellent spatial and temporal resolution, but is limited by exposure of patients and staff to ionizing radiation, poor soft tissue characterization and lack of quantitative physiologic information. MR fluoroscopy has been introduced with substantial progress during the last decade. Clinical and experimental studies performed under MR fluoroscopy have indicated the suitability of this modality for: delivery of ASD closure, aortic valves, and endovascular stents (aortic, carotid, iliac, renal arteries, inferior vena cava). It aids in performing ablation, creation of hepatic shunts and local delivery of therapies. Development of more MR compatible equipment and devices will widen the applications of MR-guided procedures. At post-intervention, MR imaging aids in assessing the efficacy of therapies, success of interventions. It also provides information on vascular flow and cardiac morphology, function, perfusion and viability. MR fluoroscopy has the potential to form the basis for minimally invasive image-guided surgeries that offer improved patient management and cost effectiveness.
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Affiliation(s)
- Maythem Saeed
- Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94107-1701, USA.
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O'Donnell M, McVeigh ER, Strauss HW, Tanaka A, Bouma BE, Tearney GJ, Guttman MA, Garcia EV. Multimodality cardiovascular molecular imaging technology. J Nucl Med 2010; 51 Suppl 1:38S-50S. [PMID: 20457794 DOI: 10.2967/jnumed.109.068155] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Cardiovascular molecular imaging is a new discipline that integrates scientific advances in both functional imaging and molecular probes to improve our understanding of the molecular basis of the cardiovascular system. These advances are driven by in vivo imaging of molecular processes in animals, usually small animals, and are rapidly moving toward clinical applications. Molecular imaging has the potential to revolutionize the diagnosis and treatment of cardiovascular disease. The 2 key components of all molecular imaging systems are the molecular contrast agents and the imaging system providing spatial and temporal localization of these agents within the body. They must deliver images with the appropriate sensitivity and specificity to drive clinical applications. As work in molecular contrast agents matures and highly sensitive and specific probes are developed, these systems will provide the imaging technologies required for translation into clinical tools. This is the promise of molecular medicine.
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Schirra CO, Weiss S, Krueger S, Caulfield D, Pedersen SF, Razavi R, Kozerke S, Schaeffter T. Accelerated 3D catheter visualization from triplanar MR projection images. Magn Reson Med 2010; 64:167-76. [DOI: 10.1002/mrm.22370] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Schirra CO, Weiss S, Krueger S, Pedersen SF, Razavi R, Schaeffter T, Kozerke S. Toward true 3D visualization of active catheters using compressed sensing. Magn Reson Med 2009; 62:341-7. [PMID: 19526499 DOI: 10.1002/mrm.22001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A crucial requirement in MR-guided interventions is the visualization of catheter devices in real time. However, true 3D visualization of the full length of catheters has hitherto been impossible given scan time constraints. Compressed sensing (CS) has recently been proposed as a method to accelerate MR imaging of sparse objects. Images acquired with active interventional devices exhibit a high CNR and are inherently sparse, therefore rendering CS ideally suited for accelerating data acquisition. A framework for true visualization of active catheters in 3D is proposed employing CS to gain high undersampling factors making real-time applications feasible. Constraints are introduced taking into account prior knowledge of catheter geometry and catheter motion over time to improve and accelerate image reconstruction. The potential of the method is demonstrated using computer simulations and phantom experiments and in vivo feasibility is demonstrated in a pig experiment.
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Affiliation(s)
- C O Schirra
- King's College London BHF Centre, Division of Imaging Sciences, NIHR Biomedical Research Centre at Guy's and St. Thomas' NHS Foundation Trust, London, UK.
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Guttman MA, Ozturk C, Raval AN, Raman VK, Dick AJ, DeSilva R, Karmarkar P, Lederman RJ, McVeigh ER. Interventional cardiovascular procedures guided by real-time MR imaging: an interactive interface using multiple slices, adaptive projection modes and live 3D renderings. J Magn Reson Imaging 2008; 26:1429-35. [PMID: 17968897 DOI: 10.1002/jmri.21199] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To develop and test a novel interactive real-time MRI environment that facilitates image-guided cardiovascular interventions. MATERIALS AND METHODS Color highlighting of device-mounted receiver coils, accelerated imaging of multiple slices, adaptive projection modes, live three-dimensional (3D) renderings and other interactive features were utilized to enhance navigation of devices and targeting of tissue. RESULTS Images are shown from several catheter-based interventional procedures performed in swine that benefit from this custom interventional MRI interface. These include endograft repair of aortic aneurysm, balloon septostomy of the cardiac interatrial septum, angioplasty and stenting, and endomyocardial cell injection, all using active catheters containing MRI receiver coils. CONCLUSION Interactive features not available on standard clinical scanners enhance real-time MRI for guiding cardiovascular interventional procedures.
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Affiliation(s)
- Michael A Guttman
- Laboratory of Cardiac Energetics, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1061, USA.
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Tsekos NV, Khanicheh A, Christoforou E, Mavroidis C. Magnetic resonance-compatible robotic and mechatronics systems for image-guided interventions and rehabilitation: a review study. Annu Rev Biomed Eng 2007; 9:351-87. [PMID: 17439358 DOI: 10.1146/annurev.bioeng.9.121806.160642] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The continuous technological progress of magnetic resonance imaging (MRI), as well as its widespread clinical use as a highly sensitive tool in diagnostics and advanced brain research, has brought a high demand for the development of magnetic resonance (MR)-compatible robotic/mechatronic systems. Revolutionary robots guided by real-time three-dimensional (3-D)-MRI allow reliable and precise minimally invasive interventions with relatively short recovery times. Dedicated robotic interfaces used in conjunction with fMRI allow neuroscientists to investigate the brain mechanisms of manipulation and motor learning, as well as to improve rehabilitation therapies. This paper gives an overview of the motivation, advantages, technical challenges, and existing prototypes for MR-compatible robotic/mechatronic devices.
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Affiliation(s)
- Nikolaos V Tsekos
- Cardiovascular Imaging Laboratory, Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110, USA.
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Sathyanarayana S, Aksit P, Arepally A, Karmarkar PV, Solaiyappan M, Atalar E. Tracking planar orientations of active MRI needles. J Magn Reson Imaging 2007; 26:386-91. [PMID: 17610285 DOI: 10.1002/jmri.20960] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To determine and track the planar orientation of active interventional devices without using localizing RF microcoils. MATERIALS AND METHODS An image-based tracking method that determines a device's orientation using projection images was developed. An automated and a manual detection scheme were implemented. The method was demonstrated in an in vivo mesocaval puncture procedure in swine, which required accurate orientation of an active transvascular needle catheter. RESULTS The plane of the catheter was determined using two projection images. The scan plane was adjusted automatically to follow the catheter plane, and its orientation with respect to a previously acquired target plane was displayed. The algorithm facilitated navigation for a fast and accurate puncture. CONCLUSION Using image-based techniques, with no mechanical design changes, the orientation of an active intravascular probe could be tracked.
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Affiliation(s)
- Shashank Sathyanarayana
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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Mattei E, Triventi M, Calcagnini G, Censi F, Kainz W, Bassen HI, Bartolini P. Temperature and SAR measurement errors in the evaluation of metallic linear structures heating during MRI using fluoroptic probes. Phys Med Biol 2007; 52:1633-46. [PMID: 17327653 DOI: 10.1088/0031-9155/52/6/006] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The purpose of this work is to evaluate the error associated with temperature and SAR measurements using fluoroptic temperature probes on pacemaker (PM) leads during magnetic resonance imaging (MRI). We performed temperature measurements on pacemaker leads, excited with a 25, 64, and 128 MHz current. The PM lead tip heating was measured with a fluoroptic thermometer (Luxtron, Model 3100, USA). Different contact configurations between the pigmented portion of the temperature probe and the PM lead tip were investigated to find the contact position minimizing the temperature and SAR underestimation. A computer model was used to estimate the error made by fluoroptic probes in temperature and SAR measurement. The transversal contact of the pigmented portion of the temperature probe and the PM lead tip minimizes the underestimation for temperature and SAR. This contact position also has the lowest temperature and SAR error. For other contact positions, the maximum temperature error can be as high as -45%, whereas the maximum SAR error can be as high as -54%. MRI heating evaluations with temperature probes should use a contact position minimizing the maximum error, need to be accompanied by a thorough uncertainty budget and the temperature and SAR errors should be specified.
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Affiliation(s)
- E Mattei
- Department of Technologies and Health, Italian National Institute of Health, Roma, Italy.
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Christoforou E, Akbudak E, Ozcan A, Karanikolas M, Tsekos NV. Performance of interventions with manipulator-driven real-time MR guidance: implementation and initial in vitro tests. Magn Reson Imaging 2007; 25:69-77. [PMID: 17222717 DOI: 10.1016/j.mri.2006.08.016] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2006] [Accepted: 08/25/2006] [Indexed: 11/24/2022]
Abstract
The purpose of this work was to implement and assess the performance of interventions inside a cylindrical magnetic resonance imaging (MRI) scanner with an MR-compatible manipulator system and manipulator-driven real-time MR guidance. The interventional system is based on a seven degree-of-freedom MR-compatible manipulator, which offers man-in-the-loop control either with a graphical user interface or with a master/slave device. The position and the orientation of the interventional tool are sent to an MR scanner for a manipulator-driven dynamic update of the imaging plane to track, visualize and guide the motion of an end-effector. Studies on phantoms were performed with a cylindrical 1.5-T scanner using an operator-managed triggered gradient-recalled echo (GRE) or a computer-managed dynamic True Fast Imaging with Steady Precession (TrueFISP). Targets were acquired with an accuracy of 3.2 mm and with an in-plane path orientation of 2.5 degrees relative to the prescribed one. Path planning, including negotiation of obstacles and needle bending, was successfully performed. The signal-to-noise ratio (SNR) of TrueFISP was 25.3+/-2.1 when the manipulator was idle and was 18.6+/-2.4 during its operation. The SNR of triggered GRE (acquired only when the manipulator was idle) was 61.3+/-1.8. In conclusion, this study shows the feasibility of performing manually directed interventions inside cylindrical MR scanners with real-time MRI.
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Affiliation(s)
- Eftychios Christoforou
- Mallinckrodt Institute of Radiology, Washington University Medical School, Box 8225, St. Louis, MO 63110, USA
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Arepally A, Karmarkar PV, Qian D, Barnett B, Atalar E. Evaluation of MR/Fluoroscopy–guided Portosystemic Shunt Creation in a Swine Model. J Vasc Interv Radiol 2006; 17:1165-73. [PMID: 16868170 DOI: 10.1097/01.rvi.0000228493.07075.fc] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE To evaluate three different percutaneous portosystemic shunts created with magnetic resonance (MR) imaging and fluoroscopy guidance in a swine model. MATERIALS AND METHODS In stage 1 of the experiment, an active MR intravascular needle system was created for needle tracking and extracaval punctures. Twenty inferior vena cava (IVC)/superior mesenteric vein (SMV)/portal vein (PV) punctures were performed in 10 swine (weight, 40-45 kg) in a 1.5-T short-bore interventional MR imager. With use of a real-time MR imaging sequence, the needle was guided through the IVC and into the SMV or PV (N = 20 punctures). After confirmation, a wire was advanced into the portal venous system under MR imaging guidance (N = 20). In stage 2, animals were transferred to the radiographic fluoroscopy suite for deployment of shunts. Three different shunts were evaluated in this study: (i) a commercial stent-graft, (ii) a prototype bridging stent, and (iii) a prototype nitinol vascular anastomotic device. Postprocedural necropsy was performed in all animals. RESULTS Successful MR-guided IVC/SMV punctures were performed in all 20 procedures (100%). All three shunts were deployed. Stent-grafts had the poorest mechanism for securing a shunt. The vascular anastomotic device and the bridging stent had more secure anchoring mechanisms but also had higher technical failure rates (50% and 40%, respectively). When deployed successfully, the vascular anastomotic device resulted in no bleeding at the sites of punctures at necropsy. CONCLUSION Percutaneous shunts and vascular anastomoses between the portal mesenteric venous system and IVC were successfully created with use of a combination of MR imaging and conventional fluoroscopy for guidance.
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Affiliation(s)
- Aravind Arepally
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins Medical Institutions, Blalock 545, 600 North Wolfe Street, Baltimore, MD 21287, USA.
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Affiliation(s)
- Robert J Lederman
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1538, USA.
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Arepally A, Karmarkar PV, Weiss C, Atalar E. Percutaneous MR imaging-guided transvascular access of mesenteric venous system: study in swine model. Radiology 2006; 238:113-8. [PMID: 16373762 DOI: 10.1148/radiol.2381041533] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To determine if, with use of magnetic resonance (MR) imaging guidance alone, transcaval puncture of the superior mesenteric vein (SMV) and/or portal vein is feasible with a percutaneous femoral vein approach. MATERIALS AND METHODS The Institutional Animal Care and Use Committee approved the animal studies. Ten inferior vena cava (IVC)-SMV punctures were performed in six pigs. An active MR intravascular needle system was used for all transvascular punctures, and all procedures were performed with a 1.5-T MR unit. The needle was introduced via a 12-F femoral vein sheath and advanced into the IVC by using a real-time gradient-recalled-echo sequence (3.4/1.2 [repetition time msec/echo time msec], 45 degrees flip angle, and six to eight frames per second). Fast transverse spoiled gradient-recalled acquisition in the steady state (SPGR) (6.0/1.5, 60 degrees flip angle, one frame per second) was performed to confirm needle trajectory. The needle system was advanced under real-time MR imaging to puncture the SMV. The location of the needle tip was confirmed with a fast spin-echo sequence (1904/4.5, 36-cm field of view). A direct MR portogram was obtained after the administration of gadopentetate dimeglumine at a concentration of 25% with fast SPGR (6/1.3, 90 degrees flip angle, no section selection, three frames per second). Success was defined as entry into the mesenteric venous system without traversal of any retroperitoneal organs or adjacent vasculature. RESULTS Successful MR imaging-guided IVC-SMV punctures were performed in all 10 procedures (100%). The needle was fully visualized as it traversed the retroperitoneum and entered the SMV. MR portograms were successfully obtained following all punctures through the needle. Conventional transverse MR imaging helped confirm that the needle did not traverse any retroperitoneal organs or vessels. CONCLUSION With use of only MR imaging guidance and an active MR imaging intravascular needle system, the authors were able to successfully puncture the SMV from the IVC with direct visualization of the needle and all retroperitoneal structures.
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Affiliation(s)
- Aravind Arepally
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins Medical Institutes, Blalock 545, 600 N Wolfe St, Baltimore, MD 21287, USA.
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Abstract
Magnetic resonance imaging (MRI), which provides superior soft-tissue imaging and no known harmful effects, has the potential as an alternative modality to guide various medical interventions. This review will focus on MR-guided endovascular interventions and present its current state and future outlook. In the first technical part, enabling technologies such as developments in fast imaging, catheter devices, and visualization techniques are examined. This is followed by a clinical survey that includes proof-of-concept procedures in animals and initial experience in human subjects. In preclinical experiments, MRI has already proven to be valuable. For example, MRI has been used to guide and track targeted cell delivery into or around myocardial infarctions, to guide atrial septal puncture, and to guide the connection of portal and systemic venous circulations. Several investigational MR-guided procedures have already been reported in patients, such as MR-guided cardiac catheterization, invasive imaging of peripheral artery atheromata, selective intraarterial MR angiography, and preliminary angioplasty and stent placement. In addition, MR-assisted transjugular intrahepatic portosystemic shunt procedures in patients have been shown in a novel hybrid double-doughnut x-ray/MRI system. Numerous additional investigational human MR-guided endovascular procedures are now underway in several medical centers around the world. There are also significant hurdles: availability of clinical-grade devices, device-related safety issues, challenges to patient monitoring, and acoustic noise during imaging. The potential of endovascular interventional MRI is great because as a single modality, it combines 3-dimensional anatomic imaging, device localization, hemodynamics, tissue composition, and function.
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Affiliation(s)
- Cengizhan Ozturk
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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17
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Atalar E. Radiofrequency safety for interventional MRI procedures. Acad Radiol 2005; 12:1149-57. [PMID: 16112515 DOI: 10.1016/j.acra.2005.06.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Revised: 06/08/2005] [Accepted: 06/08/2005] [Indexed: 11/30/2022]
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18
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Abstract
Although x-ray fluoroscopy (XRF) has guided diagnostic and therapeutic transcatheter procedures for decades, certain limitations still exist. XRF still visualizes tissue poorly and relies on projection of shadows that do not convey depth information. Adjunctive echocardiography overcomes some of these limitations but still suffers suboptimal or unreliable imaging windows. Furthermore, ionizing radiation exposure in children imparts a cancer risk. An interventional platform using real-time magnetic resonance imaging (MRI) may offer superior image guidance without radiation. Although there are many remaining challenges, but real-time MRI has the potential to revolutionize transcatheter therapeutics.
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Affiliation(s)
- A N Raval
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Building 10, Room 2c713, MSC 1538, Bethesda, MD 20892-1538, USA
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19
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Wacker FK, Elgort D, Hillenbrand CM, Duerk JL, Lewin JS. The Catheter-Driven MRI Scanner: A New Approach to Intravascular Catheter Tracking and Imaging-Parameter Adjustment for Interventional MRI. AJR Am J Roentgenol 2004; 183:391-5. [PMID: 15269031 DOI: 10.2214/ajr.183.2.1830391] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
OBJECTIVE Our aim was to test the feasibility of a hands-free approach to MRI that allows the interventionalist to track an angiographic catheter in real time throughout the procedure and to automatically change imaging parameters by catheter manipulation. MATERIALS AND METHODS A tracking method that is based on an active device localization was implemented on a 1.5-T MRI scanner. The system determines the current position and orientation of a catheter in 3D space in an endless feedback loop. Automatic scanning plane-adjustment procedures written in the software of the MRI system ensure image acquisition at the location of the catheter tip. The system calculates the device velocity to automatically adjust parameters such as field of view (FOV) and resolution. To evaluate the feasibility and performance in vivo and ex vivo, we performed experiments in two vessel phantoms and on six pigs. RESULTS The system collected the tracking data within 40 msec; an additional 10-20 msec was then required to perform the localization and velocity calculations and to update the image parameters. The system could localize a motionless catheter in the aorta in 100% and a moving catheter in 98% of measured attempts. The system responded in real time to changes in device velocity by dynamically adjusting spatial resolution and FOV in both phantom and porcine trials. Using this technique, we successfully catheterized the renal artery in two pigs. CONCLUSION Active tracking, combined with automatic scanning plane and imaging parameter adjustment, provides an intuitive MRI scanner interface for the guidance of the vascular procedure.
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Affiliation(s)
- Frank K Wacker
- Department of Radiology, Case Western Reserve University, 11100 Euclid Ave., MRI Bolwel B124, Cleveland, OH 44106, USA.
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20
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Hillenbrand CM, Elgort DR, Wong EY, Reykowski A, Wacker FK, Lewin JS, Duerk JL. Active device tracking and high-resolution intravascular MRI using a novel catheter-based, opposed-solenoid phased array coil. Magn Reson Med 2004; 51:668-75. [PMID: 15065238 DOI: 10.1002/mrm.20050] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A novel two-element, catheter-based phased array coil was designed and built for both active MR device tracking and high-resolution vessel wall imaging. The device consists of two independent solenoid coils that are wound in opposite directions, connected to separate receive channels, and mounted collinearly on an angiographic catheter. The elements were used independently or together for tracking or imaging applications, respectively. The array's dual functionality was tested on a clinical 1.5 T MRI scanner in vitro, in vivo, and in situ. During real-time catheter tracking, each element gave rise to a high-amplitude peak in the respective projection data, which enabled reliable and robust device tracking as well as automated slice positioning. In vivo microimaging with 240 microm in-plane resolution was achieved in 9 s using the device and TrueFISP imaging. Therefore, a single device was successfully implemented that met the combined requirements of intravascular device tracking and imaging.
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Affiliation(s)
- Claudia M Hillenbrand
- Department of Radiology, University Hospitals of Cleveland, Cleveland, Ohio 44106, USA
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21
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Elgort DR, Wong EY, Hillenbrand CM, Wacker FK, Lewin JS, Duerk JL. Real-time catheter tracking and adaptive imaging. J Magn Reson Imaging 2004; 18:621-6. [PMID: 14579407 DOI: 10.1002/jmri.10402] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PURPOSE To evaluate the performance of a real-time MR system for interventional procedures that adjusts specific image parameters in real time based on a catheter's speed of insertion. MATERIALS AND METHODS The system was implemented using only the hardware provided with a standard short-bore 1.5 T scanner (Siemens Magnetom Sonata) (with the exception of small tracking markers affixed to the catheter). The system tracks the position of an MR microcoil-instrumented catheter and automatically updates the scan plane's position and orientation, as well as other features, including, but not limited to, field of view, resolution, tip angle, and TE. A real-time feedback loop continuously localizes the tracking markers, updates the scan plane position and orientation, calculates the catheter's speed, adjusts the value of specific image parameters, then collects new image data, reconstructs an image, and provides it for immediate display. The system was evaluated in phantom and in vivo porcine experiments. RESULTS The system is able to accurately localize a moving catheter in the abdominal aorta, calculate the device speed, and respond by adjusting specified image parameters 98% of the time, with precision of approximately 2 mm and 1.5 degrees. CONCLUSION Simply slowing the speed of the catheter allows the clinician to adjust predetermined image parameters. This work also has the potential to build a degree of intelligence into the scanner, enabling it to react to changes in the clinical environment and automatically optimize specific image parameters.
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Affiliation(s)
- Daniel R Elgort
- Department of Radiology, University Hospitals of Cleveland and Case Western Reserve University, Cleveland, Ohio 44106, USA
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22
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Tsekos NV, Atalar E, Li D, Omary RA, Serfaty JM, Woodard PK. Magnetic resonance imaging-guided coronary interventions. J Magn Reson Imaging 2004; 19:734-49. [PMID: 15170780 DOI: 10.1002/jmri.20071] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Magnetic resonance imaging (MRI) guidance for coronary interventions offers potential advantages over conventional x-ray angiography. Advantages include the use of nonionizing radiation, combined assessment of anatomy and function, and three-dimensional assessment of the coronary arteries leading to the myocardium. These advantages have prompted a series of recent studies in this field. Real-time coronary MR angiography, with low-dose catheter-directed intraarterial (IA) infusion of contrast media, has achieved in-plane spatial resolution as low as 0.8 x 0.8 mm2 and temporal resolution as short as 130 msec per image. Catheter-based IA injection of contrast agent has proven useful in the collection of multislice and three-dimensional images, not only for coronary intervention guidance, but also in the assessment of regional myocardial perfusion fed by the affected vessel. Actively visible guidewires and guiding catheters, based on the loopless antenna concept, have been effectively used to negotiate tortuous coronary vessels during catheterization, permitting placement of coronary angioplasty balloon catheters. Passive tracking approaches have been used to image contrast agent-filled coronary catheters and to place susceptibility-based endovascular stents. Although the field is in its infancy, these early results demonstrate the feasibility for performing MRI-guided coronary interventions. Although further methodological and technical developments are required before these methods become clinically applicable, we anticipate that MRI someday will be included in the armamentarium of techniques used to diagnose and treat coronary artery disease.
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Affiliation(s)
- Nikolaos V Tsekos
- Cardiovascular Imaging Laboratory, Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri 63110, USA.
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23
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Abstract
Minimally invasive interventional radiological procedures, such as balloon angioplasty, stent placement or coiling of aneurysms, play an increasingly important role in the treatment of patients suffering from vascular disease. The non-destructive nature of magnetic resonance imaging (MRI), its ability to combine the acquisition of high quality anatomical images and functional information, such as blood flow velocities, perfusion and diffusion, together with its inherent three dimensionality and tomographic imaging capacities, have been advocated as advantages of using the MRI technique for guidance of endovascular radiological interventions. Within this light, endovascular interventional MRI has emerged as an interesting and promising new branch of interventional radiology. In this review article, the authors will give an overview of the most important issues related to this field. In this context, we will focus on the prerequisites for endovascular interventional MRI to come to maturity. In particular, the various approaches for device tracking that were proposed will be discussed and categorized. Furthermore, dedicated MRI systems, safety and compatibility issues and promising applications that could become clinical practice in the future will be discussed.
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Affiliation(s)
- L W Bartels
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Heidelberglaan 100, Room E.01.335, 3584 CX Utrecht, The Netherlands.
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24
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Eggers H, Weiss S, Boernert P, Boesiger P. Image-based tracking of optically detunable parallel resonant circuits. Magn Reson Med 2003; 49:1163-74. [PMID: 12768595 DOI: 10.1002/mrm.10459] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this work strategies for the robust localization of parallel resonant circuits are investigated. These strategies are based on the subtraction of two images, which ideally differ in signal intensity at the positions of the devices only. To modulate their signal amplification, and thereby generate the local variations, the parallel resonant circuits are alternately detuned and retuned during the acquisition. The integration of photodiodes into the devices permits their fast optical switching. Radial and spiral imaging sequences are modified to provide the data for the two images in addition to those for a conventional image in the same acquisition time. The strategies were evaluated by phantom experiments with stationary and moving catheter-borne devices. In particular, rapid detuning and retuning during the sampling of single profiles is shown to lead to a robust localization. Moreover, this strategy eliminates most of the drawbacks usually associated with image-based tracking, such as low temporal resolution. Image-based tracking may thus become a competitive (if not superior) alternative to projection-based tracking of parallel resonant circuits.
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Affiliation(s)
- Holger Eggers
- Philips Research, Sector Technical Systems, Hamburg, Germany.
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25
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Yang X, Atalar E, Zerhouni EA. Intravascular MR imaging and intravascular MR-guided interventions. INTERNATIONAL JOURNAL OF CARDIOVASCULAR INTERVENTIONS 2003; 2:85-96. [PMID: 12623594 DOI: 10.1080/acc.2.2.85.96] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Intravascular MR technology, using an intravascularly placed MR receiver probe to acquire high-resolution angiographic MR images (i.e. intravascular MR imaging) and to guide cardiovascular interventional therapies (i.e. intravascular MR-guided interventions), is a new, very attractive development in the field of MR imaging. The new technology offers unique advantages for cardiovascular imaging and interventions, including superior contrast capability and multiplanar imaging capabilities without the use of contrast agents and with no risk of ionizing radiation. Thecombination of intravascular MR techniques with other advanced MR imaging techniques, such as functional MR imaging, will open new avenues for the future comprehensive management of cardiovascular atherosclerotic disease. Further improvements in intravascular MR fluoroscopy with true real-time display, analogous to X-ray fluoroscopy, will dramatically establish the role of intravascular MR technology in modern medicine.
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Affiliation(s)
- Xiaoming Yang
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
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26
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Worthley SG, Helft G, Fuster V, Fayad ZA, Shinnar M, Minkoff LA, Schechter C, Fallon JT, Badimon JJ. A novel nonobstructive intravascular MRI coil: in vivo imaging of experimental atherosclerosis. Arterioscler Thromb Vasc Biol 2003; 23:346-50. [PMID: 12588782 DOI: 10.1161/01.atv.0000053183.08854.a4] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE MRI is being used to characterize the composition of atherosclerotic plaques. However, the resolution achievable using surface radiofrequency coils is limited by the signal to noise ratio. We studied the utility of a new intravascular (IV) MRI probe for high-resolution in vivo imaging of atherosclerotic lesions. METHODS AND RESULTS Balloon-injured Watanabe heritable hyperlipidemic rabbits served as the experimental model of atherosclerosis. The newly developed IV MRI probe is 1.3 mm in diameter and can be positioned over a guidewire. MRI was performed with both an external phased-array coil and the IV MR coil. MR observations were correlated with histopathology. After MRI, the animals were killed and analysis of agreement between MR and histopathology was performed. The IV MR coil allows aortic images to be obtained with 156x156 micro m(2) in-plane resolution versus 352x352 micro m(2) when used with the external phased-array coil. No significant motion artifacts were noted, despite the continuation of arterial blood flow during image acquisition around the IV probe. The different components of the atherosclerotic lesions (lipid core and fibrous cap) were easily identified. There was an excellent agreement between MRI with the IV coil and histopathology by simple linear regression for both the mean wall thickness (r=0.88, slope 0.82, P<0.0001) and vessel wall area (r=0.86, slope 1.08, P<0.0001). CONCLUSIONS The new nonobstructive design for this intravascular coil provides great promise for additional work in high-resolution MRI characterization of atherosclerotic plaques in vivo. The ability to position the probe with a guidewire allows its placement under fluoroscopic or MRI guidance, whereas its size is compatible with human coronary arteries.
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Affiliation(s)
- Stephen G Worthley
- Zena and Michael A. Wiener Cardiovascular Institute, Mount Sinai School of Medicine, New York, NY, USA.
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27
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Peters DC, Lederman RJ, Dick AJ, Raman VK, Guttman MA, Derbyshire JA, McVeigh ER. Undersampled projection reconstruction for active catheter imaging with adaptable temporal resolution and catheter-only views. Magn Reson Med 2003; 49:216-22. [PMID: 12541240 PMCID: PMC2396305 DOI: 10.1002/mrm.10390] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
In this study undersampled projection reconstruction (PR) was used for rapid catheter imaging in the heart, employing steady-state free precession (SSFP) contrast. Active catheters and phased-array coils were used for combined imaging of anatomy and catheter position in swine. Real-time imaging of catheter position was performed with relatively high spatial and temporal resolution, providing 2 x 2 x 8 mm spatial resolution and four to eight frames per second. Two interactive features were introduced. The number of projections (Np) was adjusted interactively to trade off imaging speed and artifact reduction, allowing acquisition of high-quality or high-frame-rate images. Thin-slice imaging was performed, with interactive requests for thick-slab projection images of the signal received solely from the active catheter. Briefly toggling on catheter-only projection images was valuable for verifying that the catheter tip was contained within the selected slice, or for locating the catheter when part of it was outside the selected slice.
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Affiliation(s)
- Dana C Peters
- Laboratory of Cardiac Energetics, National Institutes of Health, Bethesda, Maryland 20892-0161, USA.
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28
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Serfaty JM, Yang X, Foo TK, Kumar A, Derbyshire A, Atalar E. MRI-guided coronary catheterization and PTCA: A feasibility study on a dog model. Magn Reson Med 2003; 49:258-63. [PMID: 12541245 DOI: 10.1002/mrm.10393] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The aim of this work was to demonstrate the feasibility of MRI-guided coronary artery catheterization and intervention in a dog model. Experiments were performed on 10 healthy dogs. A 9F introducer sheath was placed through a right carotid artery cutdown. A prototype 0.014-inch coronary MRI guidewire, a prototype 7 French MRI-guiding catheter, and two flexible surface coils were connected to a GE 1.5 T CV/i scanner for simultaneous visualization of the guidewire, guiding catheter, and chest anatomy. Images were displayed in real time on an in-room monitor. A nongated, single-slice fast gradient-echo sequence was used to obtain real-time images of the catheters and background anatomy during the intervention. Fifteen selective catheterizations were attempted in the coronary arteries, and all were successful. Selective injection of diluted gadolinium into the MRI-guiding catheter provided dynamic 2D projection coronary angiography in all cases, confirming successful catheterization. Percutaneous transluminal coronary angioplasty (PTCA) was attempted after two catheterizations, and all attempts were successful. Inflation of the balloon angioplasty catheter was performed successfully in the left anterior and circumflex arteries. Our results indicate that coronary artery catheterization and intracoronary balloon angioplasty are feasible with MRI guidance only. MRI guidance may be used as an alternative to X-ray guidance in coronary artery interventions in the future.
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Omary RA, Green JD, Fang WS, Viohl I, Finn JP, Li D. Use of internal coils for independent and direct MR imaging-guided endovascular device tracking. J Vasc Interv Radiol 2003; 14:247-54. [PMID: 12582194 DOI: 10.1097/01.rvi.0000058328.82956.15] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE To test the hypotheses that a single internal guide wire coil (i) permits independent and direct depiction of guide wires and catheters and (ii) improves catheter-tracking accuracy and depiction compared to external receiver coils. MATERIALS AND METHODS Standard 5-6-F angiographic catheters were filled with dilute 4% gadolinium chelate. A single 0.030-inch-diameter internal guide wire coil was placed inside the catheter. True fast imaging with steady-state precession was used to directly visualize the guide wire. Inversion recovery-prepared fast low-angle shot technique was used to track catheters over a thick slice. In phantom experiments, we compared catheter signal-to-noise ratios (SNRs) with the internal coil and a phased-array surface coil with use of the Wilcoxon signed-rank test. Tip-tracking accuracy was assessed with use of linear regression. In pigs (n = 7), catheters and guide wires were independently tracked in real time. RESULTS In phantoms, catheter SNR with the internal coil (12.0) was significantly greater than that with the surface coil (4.0; P =.001). Tip-tracking accuracy was also improved with use of the internal coil (R(2) = 0.94 vs 0.50). In swine vasculature, catheters and guide wires could be directly and independently tracked at 1.7-2.0 frames per second. Catheters were clearly visualized with use of the internal coil, with a typical catheter background contrast-to-noise ratio of 6.6. Catheters were not visible with use of the external coil because of the small catheter size compared to the slice thickness. CONCLUSION Internal guide wire coils permit independent and direct depiction of guide wires and catheters in vivo for MR imaging-guided endovascular interventions. They also improve catheter tracking accuracy and depiction compared to external coils.
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Affiliation(s)
- Reed A Omary
- Department of Radiology, Northwestern University Medical School, 676 North St. Clair, Suite 800, Chicago, Illinois 60611, USA.
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Quick HH, Kuehl H, Kaiser G, Hornscheidt D, Mikolajczyk KP, Aker S, Debatin JF, Ladd ME. Interventional MRA using actively visualized catheters, TrueFISP, and real-time image fusion. Magn Reson Med 2003; 49:129-37. [PMID: 12509828 DOI: 10.1002/mrm.10334] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An integrated system for performing interventional magnetic resonance angiography (MRA) with actively visualized instruments and real-time image fusion was implemented on a 1.5 T scanner. True fast imaging with steady precession (TrueFISP) imaging provided high acquisition speed paired with high signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the simultaneous visualization of active instruments and arterial morphology. The system enabled simultaneous image reconstruction and image postprocessing of multiple receiver channels, with subsequent image fusion display in real time. Optional interleaved image acquisition in two planes provided additional important information for biplanar instrument guidance. Various vascular interventions, including selective catheterization and subsequent selective MRA of the abdominal aorta, renal arteries, superior mesenteric artery (SMA), hepatic artery, and aortic arch, were performed on 10 pigs under MR guidance. In terms of instrument contrast, image acquisition, reconstruction, and fusion speed, the setup represents a powerful platform for performing interventional MRA procedures.
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Affiliation(s)
- Harald H Quick
- Department of Diagnostic and Interventional Radiology, University Hospital Essen, Essen, Germany.
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Quick HH, Ladd ME. Interventionelle MRA: Konzepte zur aktiven Visualisierung von Kathetern und Stents. Z Med Phys 2003; 13:188-92. [PMID: 14562542 DOI: 10.1078/0939-3889-00159] [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: 11/18/2022]
Abstract
A precondition to safe guidance of vascular guidewires and catheters during the course of magnetic resonance (MR)-guided vascular intervention is a high-contrast visualization of the instruments. The integration of miniature radiofrequency (RF) coils and coaxial cables into guidewires and catheters enables the reception of RF signal from the lumen of blood vessels, and thus the active visualization of the instruments. Moreover, metallic vascular implants (stents) can be modified to act as intravascular RF antennas that inductively couple their RF signal to a conventional surface RF coil. Such stent resonators show signal amplification inside the lumen of the stent and thus can be visualized with high contrast in MR images. Furthermore, once such a device has been implanted, the method offers the potential for non-invasive long-term follow-up of the stent patency.
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Affiliation(s)
- Harald H Quick
- Institut für Diagnostische und Interventionelle Radiologie Universitätsklinikum Essen.
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Lederman RJ, Guttman MA, Peters DC, Thompson RB, Sorger JM, Dick AJ, Raman VK, McVeigh ER. Catheter-based endomyocardial injection with real-time magnetic resonance imaging. Circulation 2002; 105:1282-4. [PMID: 11901036 PMCID: PMC1317571 DOI: 10.1161/01.cir.0000012425.71261.fc] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND We tested the feasibility of targeted left ventricular (LV) mural injection using real-time MRI (rtMRI). METHODS AND RESULTS A 1.5T MRI scanner was customized with a fast reconstruction engine, transfemoral guiding catheter-receiver coil (GCC), MRI-compatible needle, and tableside consoles. Commercial real-time imaging software was customized to facilitate catheter navigation and visualization of injections at 4 completely refreshed frames per second. The aorta was traversed and the left ventricular cavity was entered under direct rtMRI guidance. Pigs underwent multiple injections with dilute gadolinium-DTPA. All myocardial segments were readily accessed. The active GCC and the passive Stiletto needle injector were readily visualized. More than 50 endomyocardial injections were performed with the aid of rtMRI; 81% were successful with this first-generation prototype. CONCLUSION Percutaneous endomyocardial drug delivery is feasible with the aid of rtMRI, which permits precise 3-dimensional localization of injection within the LV wall.
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Affiliation(s)
- Robert J Lederman
- Cardiovascular Branch, Division of Intramural Research, National Heart Lung and Blood Institute, National Institutes of Health, Bethesda, Md 20892-1061, USA.
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Abstract
This work describes a real-time imaging and visualization technique that allows multiple field of view (FOV) imaging. A stream of images from a single receiver channel can be reconstructed at multiple FOVs within each image frame. Alternately, or in addition, when multiple receiver channels are available, image streams from each channel can be independently reconstructed at multiple FOVs. The implementation described here provides for real-time visualization of the placement of guidewires and catheters on a dynamic roadmap during interventional procedures. The loopless catheter antenna, an electrically active intravascular probe, was used for MR signal reception. In 2D projection images, the catheter and surrounding structures within its diameter of sensitivity appear as bright signal. The simplicity of the resulting images allows very-narrow-FOV imaging to decrease imaging time. Very-narrow-FOV images are acquired on MR receiver channels that collect guidewire or catheter data. These very-narrow-FOV images provide very high frame rate continuous, real-time imaging of the interventional devices (25 fps). Large-FOV images are formed from receiver channels that collect anatomical data from standard imaging surface coils, and simultaneously provide a dynamic, frequently updated roadmap. These multiple-FOV images are displayed together, improving visualization of interventional device placement.
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Affiliation(s)
- Pelin Aksit
- Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-0845, USA
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35
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Guttman MA, McVeigh ER. Techniques for fast stereoscopic MRI. Magn Reson Med 2001; 46:317-23. [PMID: 11477636 PMCID: PMC2396259 DOI: 10.1002/mrm.1194] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2000] [Accepted: 02/12/2001] [Indexed: 11/11/2022]
Abstract
Stereoscopic MRI can impart 3D perception with only two image acquisitions. This economy over standard multiplanar 3D volume renderings allows faster frame rates, which are needed for real-time imaging applications. Real-time 3D perception may enhance the appreciation of complex anatomical structures, and may improve hand-eye coordination while manipulating a medical device during an image-guided interventional procedure. To this goal, a system is being developed to acquire and display stereoscopic MR images in real-time. A clinically used, fast gradient-recalled echo-train sequence has been modified to produce stereo image pairs. Features have been added for depth cueing, view sharing, and bulk signal suppression. A workstation was attached to a clinical MR scanner for fast data extraction, image reconstruction and stereoscopic image display.
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Affiliation(s)
- M A Guttman
- Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892-1061, USA.
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36
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Abstract
Important advances in rapid magnetic resonance (MR) imaging technology and its application to cardiovascular imaging have been made during the past decade. High-field-strength clinical magnets, high-performance gradient hardware, and ultrafast pulse sequence technology are rapidly making the vision of a comprehensive "one-stop shop" cardiac MR imaging examination a reality. This examination is poised to have a significant effect on the management of coronary artery disease by means of assessment of wall motion with tagging and pharmacologic stress testing, evaluation of the coronary microvasculature with perfusion imaging, and direct visualization of the coronary arteries with MR coronary angiography. This article reviews current state-of-the-art pulse sequence technology and its application to the evaluation of ischemic heart disease by means of MR tagging with dobutamine stress testing, MR perfusion imaging, and MR coronary angiography. Cutting edge areas of research in coil design and exciting new areas of metabolic and oxygen level-dependent imaging are also explored.
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Affiliation(s)
- S B Reeder
- Department of Radiology, Rm H1306, Stanford University, 300 Pasteur Dr, Stanford, CA 94304, USA.
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37
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Abstract
Current safety regulations for local radiofrequency (rf) heating, developed for externally positioned rf coils, may not be suitable for internal rf coils that are being increasingly used in interventional MRI. This work presents a two-step model for rf heating in an interventional MRI setting: (1) the spatial distribution of power in the sample from the rf pulse (Maxwell's equations); and (2) the transformation of that power to temperature change according to thermal conduction and tissue perfusion (tissue bioheat equation). The tissue bioheat equation is approximated as a linear, shift-invariant system in the case of local rf heating and is fully characterized by its Green's function. Expected temperature distributions are calculated by convolving (averaging) transmit coil specific absorption rate (SAR) distributions with the Green's function. When the input SAR distribution is relatively slowly varying in space, as is the case with excitation by external rf coils, the choice of averaging methods makes virtually no difference on the expected heating as measured by temperature change (deltaT). However, for highly localized SAR distributions, such as those encountered with internal coils in interventional MRI, the Green's function method predicts heating that is significantly different from the averaging method in current regulations. In our opinion, the Green's function method is a better predictor since it is based on a physiological model. The Green's function also elicits a time constant and scaling factor between SAR and deltaT that are both functions of the tissue perfusion rate. This emphasizes the critical importance of perfusion in the heating model. The assumptions made in this model are only valid for local rf heating and should not be applied to whole body heating.
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Affiliation(s)
- C J Yeung
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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38
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Nitz WR, Oppelt A, Renz W, Manke C, Lenhart M, Link J. On the heating of linear conductive structures as guide wires and catheters in interventional MRI. J Magn Reson Imaging 2001; 13:105-14. [PMID: 11169811 DOI: 10.1002/1522-2586(200101)13:1<105::aid-jmri1016>3.0.co;2-0] [Citation(s) in RCA: 211] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The interest in performing vascular interventions under magnetic resonance (MR) guidance has initiated the evaluation of the potential hazard of long conductive wires and catheters. The objective of this work is to present a simple analytical approach to address this concern and to demonstrate the agreement with experimental results. The first hypothesis is that a long conductive structure couples with the electric field of the radio frequency (RF) transmit coil. The second hypothesis is that this coupling induces high voltages near the wire ends. These voltages can cause tissue heating due to induced currents. The experimental results show an increase in coupling when moving a guide wire toward the wall of an RF transmit coil, documented with a temperature increase of a saline solution in close proximity to the tip of the guide wire. The coupling of the wire not only presents a potential hazard to the patient, but also interferes with the visualization of the wire. A safe alternative would be the use of nonconducting guide wires. J. Magn. Reson. Imaging 2001;13:105-114.
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Affiliation(s)
- W R Nitz
- Department of Radiology, University of Regensburg, Germany.
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39
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Nitz WR, Oppelt A, Renz W, Manke C, Lenhart M, Link J. On the heating of linear conductive structures as guide wires and catheters in interventional MRI. J Magn Reson Imaging 2001. [DOI: 10.1002/1522-2586(200101)13:1%3c105::aid-jmri1016%3e3.0.co;2-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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40
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Yang X, Atalar E. Intravascular MR imaging-guided balloon angioplasty with an MR imaging guide wire: feasibility study in rabbits. Radiology 2000; 217:501-6. [PMID: 11058652 DOI: 10.1148/radiology.217.2.r00oc17501] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To develop a technique for intravascular magnetic resonance (MR)-guided balloon angioplasty with use of an MR imaging guide wire. MATERIALS AND METHODS An MR imaging guide wire (0.6-mm loopless antenna) that could be placed within a balloon catheter was manufactured. The guide wire was expected to function as either an MR receiver probe in real-time MR imaging or a guide wire for use with interventional devices. Laparotomy was performed in eight rabbits, and a dilatable stenosis was created at the upper abdominal aorta. Balloon angioplasty, validated at pre- and postoperative MR aortography with renal contrast enhancement was performed by using a 1.5-T MR unit with a fast spoiled gradient-echo pulse sequence, short repetition and echo times, and a rate of three frames per second. RESULTS During MR tracking, the entire length of the MR imaging guide wire was always visible as a band of high signal intensity. In all cases, the MR imaging guide wires were passed through the aortic stenoses dilated by means of balloon inflation. Before balloon angioplasty, flow in the aorta distal to the stenosis was decreased, which caused mild contrast enhancement in each kidney. After balloon angioplasty, distal flow was restored, resulting in substantial renal enhancement. CONCLUSION The MR imaging guide wire is a potential tool for use in endovascular interventional MR imaging.
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Affiliation(s)
- X Yang
- Department of Radiology, Johns Hopkins University School of Medicine, Outpatient Center Rm 4243, 601 N Caroline St, Baltimore MD 21287-0845, USA.
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41
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Abstract
In this study the feasibility of intraarterial contrast administration was investigated. Its use for navigation and treatment evaluation during MR-guided intravascular interventions was explored in phantom and animal experiments. An injection protocol was developed, which accounts for sequence parameters and vessel flow rate. Tracking a bolus of contrast agent was useful to verify the catheter tip position and to assess flow conditions. Compared to intravenous contrast-enhanced magnetic resonance angiography (CE-MRA), selective contrast administration permitted a strongly reduced dose. In two-dimensional (2D) acquisitions overlap of vessels was prevented. Injection and acquisition were easily and accurately synchronized in selective 3D CE-MRA, and a high contrast concentration could be maintained during the entire acquisition. Selective injection is useful in the course of an intervention, to facilitate navigation, provide information on flow conditions, and to evaluate treatment progress repeatedly.
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Affiliation(s)
- C Bos
- Department of Radiology, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands.
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42
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Buecker A, Neuerburg JM, Adam GB, Glowinski A, Schaeffter T, Rasche V, van Vaals JJ, Molgaard-Nielsen A, Guenther RW. Real-time MR fluoroscopy for MR-guided iliac artery stent placement. J Magn Reson Imaging 2000; 12:616-22. [PMID: 11042645 DOI: 10.1002/1522-2586(200010)12:4<616::aid-jmri15>3.0.co;2-f] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The purpose of this study was to test the feasibility of real-time magnetic resonance (MR) guidance of iliac artery stent placement. Radial scanning together with the sliding window reconstruction technique was implemented on a 1.5 T magnet, yielding a frame rate of 20 images per second. Seven prototype nitinol ZA stents were deployed in iliac arteries of living pigs under MR control. All stents were well visualized on the radial MR images, allowing depiction of the mounted stents as well as stent deployment without anatomy-obscuring artifacts. Stent placement was sucessful in all cases and took 6 minutes on average. The position of the stents was correctly visualized by real-time radial MR scanning, as proved by digital subtraction X-ray angiography. Combined radial scanning and the sliding window reconstruction technique allow real-time MR-guided stent placement in iliac arteries.
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Affiliation(s)
- A Buecker
- Clinic for Diagnostic Radiology, University of Technology, D-52057 Aachen, Germany.
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43
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Abstract
A new optical method of detuning parallel resonant circuits is described. This method involves the integration of a photoresistor in parallel with the inductor and capacitor of a parallel resonant circuit, in this case a magnetic resonance imaging (MRI) receiver coil. A fiberoptic cable extending the length of the interventional device is used in conjunction with an external light source to deliver light to the photoresistor. Exposing the photoresistor to light changes its bulk resistance and greatly lowers the Q of the parallel resonant circuit, effectively detuning it. By combining this optical detuning scheme with inductive coupling of the interventional device-mounted microcoils to a standard MRI coil, a completely wireless device for active device tracking has been created. This new device improves on current technology by simplifying device complexity and reducing patient risk by eliminating the need for electrical connections between the device-mounted microcoils to the MR receiver channel.
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Affiliation(s)
- E Y Wong
- Department of Biomedical Engineering, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, Ohio 44106, USA
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44
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Serfaty JM, Atalar E, Declerck J, Karmakar P, Quick HH, Shunk KA, Heldman AW, Yang X. Real-time projection MR angiography: feasibility study. Radiology 2000; 217:290-5. [PMID: 11012459 DOI: 10.1148/radiology.217.1.r00se42290] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Intraarterial injections of small doses of gadopentetate dimeglumine were combined with a fast spoiled-gradient-echo magnetic resonance (MR) sequence to obtain real-time projection angiographic images of the rabbit aorta and canine coronary arteries. Arterial filling and washout, as well as venous and perfusion phases, were clearly displayed, demonstrating that arterial fluoroscopy in which an MR technique is used is feasible.
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Affiliation(s)
- J M Serfaty
- Departments of Radiology and Biomedical Engineering, Biomedical Engineering, Division of Cardiology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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45
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Serfaty JM, Yang X, Aksit P, Quick HH, Solaiyappan M, Atalar E. Toward MRI-guided coronary catheterization: visualization of guiding catheters, guidewires, and anatomy in real time. J Magn Reson Imaging 2000; 12:590-4. [PMID: 11042641 DOI: 10.1002/1522-2586(200010)12:4<590::aid-jmri11>3.0.co;2-3] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The success of x-ray fluoroscopy-guided coronary catheterization depends in part on the ability to obtain simultaneous and real-time visualization of the guidewire, guiding catheter, and anatomy of the chest. The hypothesis explored in this paper is that magnetic resonance imaging (MRI) could provide this ability. This hypothesis was tested with loopless antennas used as the guidewire and a guiding catheter and two surface coils, each connected to four different receiver channels of a GE 1.5-T CV/I MRI scanner. Experiments were conducted on six healthy dogs. Intravascular antennas were inserted in the right carotid artery and maneuvered in the aorta while running a fast gradient-echo sequence (TR/TE 5/1.3 msec, flip angle 7 degrees). Real-time projection images of the chest anatomy, together with the guidewire and guiding catheter, were obtained. Positioning of the MRI guiding catheter either in the descending aorta, ascending aorta, or heart was achieved easily. This study represents a step toward MRI-guided coronary catheterization.
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Affiliation(s)
- J M Serfaty
- Department of Radiology and Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-0845, USA
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46
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Abstract
Several attributes make magnetic resonance imaging (MRI) attractive for guidance of intravascular therapeutic procedures, including high soft tissue contrast, imaging in arbitrary oblique planes, lack of ionizing radiation, and the ability to provide functional information, such as flow velocity or flow volume per unit time, in conjunction with morphologic information. For MR guidance of vascular interventions to be safe, the interventionalist must be able to visualize catheters and guidewires relative to the vascular system and surrounding tissues. A number of approaches for rendering instruments visible in an MR environment have been developed, including both passive and active techniques. Passive techniques depend on contrast agents or susceptibility artifacts that enhance the appearance of the catheter in the image itself, whereas active techniques rely on supplemental hardware built into the catheter, such as a radiofrequency (RF) coil. Additionally, the ability to introduce an RF coil mounted on a catheter presents the opportunity to obtain high-resolution images of the vessel wall. These images can provide the capability to distinguish and identify various plaque components. The additional capabilities of MRI could potentially open up new applications within the purview of vascular interventions beyond those currently performed under X-ray fluoroscopic guidance.
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Affiliation(s)
- M E Ladd
- Department of Radiology, University Hospital Essen, D-45122 Essen, Germany.
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47
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Abstract
The safety of the barewire loopless catheter antenna in transmit mode is addressed with respect to radiofrequency (RF) heating. Analytical expressions for electric field and specific absorption rate (SAR) distributions surrounding the antenna are postulated and experimentally verified. Limiting RF transmit power to 40-70 mW time-averaged power, depending on the specific antenna design, will ensure that the current regulatory guideline of SAR of 8 W/kg in any gram of tissue is not exceeded. These limits can act as guidelines for the design of RF pulses for use with this device. Further study is required to examine the safety of the antenna in receive mode.
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Affiliation(s)
- C J Yeung
- Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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48
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Abstract
Stent deployment is used to improve the immediate and long-term results of vascular interventions in various vascular sites. X-ray angiography as an imaging modality is often limited in providing an accurate assessment with regard to vessel size, plaque calcification, or stent deployment. In this study, the potential of using the stent endoprothesis as a radiofrequency (RF) receive-only probe for MR guidance and lesion imaging was investigated. Three different principles were developed to visualize stents actively, the first employing the stent as a loop antenna, the second employing the stent in an electrical dipole configuration, and the third employing the stent in a hybrid configuration as a coaxial line antenna. The three configurations resulted in different signal characteristics. Based on two of these antenna configurations, stent deployment devices were built and evaluated in in vitro as well as in vivo sheep experiments. Active stent visualization allows real-time MR guidance through the vessel tree and monitoring of stent deployment. In addition, the stent antenna may become useful for high resolution imaging of the vessel wall. Magn Reson Med 42:738-745, 1999.
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Affiliation(s)
- H H Quick
- Institute of Diagnostic Radiology, University Hospital Zürich, Zürich, Switzerland
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49
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Abstract
The purpose of this study was to develop a non-invasive method of imaging the thoracic aorta that would provide both morphological detail within the aortic wall and information about regional aortic wall motion. An esophageal probe is described that allows transesophageal MR imaging (TEMRI) of the thoracic aorta and has several potential advantages over the competing non-vasculoinvasive techniques of transesophageal echocardiography (TEE) or standard MRI. The probe consists of a loopless antenna housed inside a modified Levin gastric tube, with external matching and tuning circuitry. Using this probe, the thoracic aorta has been imaged in longitudinal and cross-sectional views. Details of the aortic wall were readily seen. Tissue tagging for measurement of focal stress/strain relationships was demonstrated to be feasible. TEMRI avoids the risks inherent in intravascular MRI yet provides comparable image quality. Potential applications of the device are discussed.
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Affiliation(s)
- K A Shunk
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287-0845, USA
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50
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Yang X, Bolster BD, Kraitchman DL, Atalar E. Intravascular MR-monitored balloon angioplasty: an in vivo feasibility study. J Vasc Interv Radiol 1998; 9:953-9. [PMID: 9840040 DOI: 10.1016/s1051-0443(98)70429-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
Abstract
PURPOSE To develop a new method for monitoring balloon angioplasty by using an intravascular magnetic resonance (MR) imaging technique. MATERIALS AND METHODS Nine New Zealand White rabbits were used: seven for technique refinement, including surgery, device insertion, stenosis creation, and MR protocol development; and two for the final MR imaging of the balloon angioplasty. The in vivo experimental method involved insertion of a catheter antenna and a balloon catheter, via femoral arteriotomies bilaterally, into the target site of the upper abdominal aorta, where a stenosis was artificially created by binding a plastic cable tie. Then, the entire process of the dilation of the stenosis with balloon inflation was monitored under MR fluoroscopy. RESULTS Catheter insertions were successful, and a 5-mm-long stenosis of the aorta was produced in all nine rabbits. Eight complete balloon angioplasty procedures were satisfactorily monitored and recorded, showing clearly the stenosis of the aorta at the beginning of the procedure, the dilation of the stenosis during the balloon inflation, and the complete opening of the stenosis after balloon dilation. CONCLUSION Preliminary results of in vivo balloon angioplasty monitored with intravascular MR imaging are presented. MR fluoroscopy, based on the intravascular MR imaging technique, may represent a potential alternative to x-ray fluoroscopy for guiding interventional treatment of cardiovascular diseases.
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Affiliation(s)
- X Yang
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD 21287-0845, USA
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