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Schmidt EJ, Olson G, Tokuda J, Alipour A, Watkins RD, Meyer EM, Elahi H, Stevenson WG, Schweitzer J, Dumoulin CL, Johnson T, Kolandaivelu A, Loew W, Halperin HR. Intracardiac MR imaging (ICMRI) guiding-sheath with amplified expandable-tip imaging and MR-tracking for navigation and arrythmia ablation monitoring: Swine testing at 1.5 and 3T. Magn Reson Med 2022; 87:2885-2900. [PMID: 35142398 PMCID: PMC8957513 DOI: 10.1002/mrm.29168] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 11/30/2021] [Accepted: 01/05/2022] [Indexed: 12/15/2022]
Abstract
PURPOSE Develop a deflectable intracardiac MR imaging (ICMRI) guiding-sheath to accelerate imaging during MR-guided electrophysiological (EP) interventions for radiofrequency (500 kHz) ablation (RFA) of arrythmia. Requirements include imaging at three to five times surface-coil SNR in cardiac chambers, vascular insertion, steerable-active-navigation into cardiac chambers, operation with ablation catheters, and safe levels of MR-induced heating. METHODS ICMRI's 6 mm outer-diameter (OD) metallic-braided shaft had a 2.6 mm OD internal lumen for ablation-catheter insertion. Miniature-Baluns (MBaluns) on ICMRI's 1 m shaft reduced body-coil-induced heating. Distal section was a folded "star"-shaped imaging-coil mounted on an expandable frame, with an integrated miniature low-noise-amplifier overcoming cable losses. A handle-activated movable-shaft expanded imaging-coil to 35 mm OD for imaging within cardiac-chambers. Four MR-tracking micro-coils enabled navigation and motion-compensation, assuming a tetrahedron-shape when expanded. A second handle-lever enabled distal-tip deflection. ICMRI with a protruding deflectable EP catheter were used for MR-tracked navigation and RFA using a dedicated 3D-slicer user-interface. ICMRI was tested at 3T and 1.5T in swine to evaluate (a) heating, (b) cardiac-chamber access, (c) imaging field-of-view and SNR, and (d) intraprocedural RFA lesion monitoring. RESULTS The 3T and 1.5T imaging SNR demonstrated >400% SNR boost over a 4 × 4 × 4 cm3 FOV in the heart, relative to body and spine arrays. ICMRI with MBaluns met ASTM/IEC heating limits during navigation. Tip-deflection allowed navigating ICMRI and EP catheter into atria and ventricles. Acute-lesion long-inversion-time-T1-weighted 3D-imaging (TWILITE) ablation-monitoring using ICMRI required 5:30 min, half the time needed with surface arrays alone. CONCLUSION ICMRI assisted EP-catheter navigation to difficult targets and accelerated RFA monitoring.
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Affiliation(s)
- Ehud J. Schmidt
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | - Gregory Olson
- Cardiac Arrhythmia and Heart Failure DivisionAbbott LaboratoriesMinnetonkaMinnesotaUSA
| | - Junichi Tokuda
- RadiologyBrigham and Women’s HospitalBostonMassachusettsUSA
| | - Akbar Alipour
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | | | - Eric M. Meyer
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | - Hassan Elahi
- Medicine (Cardiology)Johns Hopkins UniversityBaltimoreMarylandUSA
| | | | - Jeffrey Schweitzer
- Cardiac Arrhythmia and Heart Failure DivisionAbbott LaboratoriesMinnetonkaMinnesotaUSA
| | | | | | | | - Wolfgang Loew
- RadiologyCincinnati Children’s Hospital Medical CenterCincinnatiOhioUSA
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Nayak KS, Lim Y, Campbell-Washburn AE, Steeden J. Real-Time Magnetic Resonance Imaging. J Magn Reson Imaging 2022; 55:81-99. [PMID: 33295674 PMCID: PMC8435094 DOI: 10.1002/jmri.27411] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2020] [Revised: 10/06/2020] [Accepted: 10/09/2020] [Indexed: 01/03/2023] Open
Abstract
Real-time magnetic resonance imaging (RT-MRI) allows for imaging dynamic processes as they occur, without relying on any repetition or synchronization. This is made possible by modern MRI technology such as fast-switching gradients and parallel imaging. It is compatible with many (but not all) MRI sequences, including spoiled gradient echo, balanced steady-state free precession, and single-shot rapid acquisition with relaxation enhancement. RT-MRI has earned an important role in both diagnostic imaging and image guidance of invasive procedures. Its unique diagnostic value is prominent in areas of the body that undergo substantial and often irregular motion, such as the heart, gastrointestinal system, upper airway vocal tract, and joints. Its value in interventional procedure guidance is prominent for procedures that require multiple forms of soft-tissue contrast, as well as flow information. In this review, we discuss the history of RT-MRI, fundamental tradeoffs, enabling technology, established applications, and current trends. LEVEL OF EVIDENCE: 5 TECHNICAL EFFICACY STAGE: 1.
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Affiliation(s)
- Krishna S. Nayak
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA,Address reprint requests to: K.S.N., 3740 McClintock Ave, EEB 400C, Los Angeles, CA 90089-2564, USA.
| | - Yongwan Lim
- Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, California, USA
| | - Adrienne E. Campbell-Washburn
- Cardiovascular Branch, Division of Intramural Research, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - Jennifer Steeden
- Institute of Cardiovascular Science, Centre for Cardiovascular Imaging, University College London, London, UK
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Hu X, Li Y, Li J, Chen H. Effects of altered blood flow induced by the muscle pump on thrombosis in a microfluidic venous valve model. LAB ON A CHIP 2020; 20:2473-2481. [PMID: 32543635 DOI: 10.1039/d0lc00287a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Deep vein thrombosis (DVT) often occurs in the lower limb veins of bedridden patients and greatly reduces the quality of life. The altered blood flow in venous valves induced by the insufficient efficacy of the muscle pump is commonly considered as a main factor. However, it is still a great challenge to observe the altered blood flow in real time, and its role in the formation of thrombi is poorly understood. Here we make a microfluidic venous valve model with flexible leaflets in a deformable channel that can mimic the motion of valves and the compression of vessels by muscle contraction, and identify the stasis and intermittent reflux in the valve pocket generated by the muscle pump. A thrombus forms in the stasis flow, while the intermittent reflux removes the fibrin and inhibits the growth of the thrombus. A flexible microfluidic device that can mimic the motion of valves and the contraction of vessels would have wide applications in the research on cardiovascular diseases.
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Affiliation(s)
- Xiangyu Hu
- State Key Laboratory of Tribology, Mechanical Engineering Department, Tsinghua University, Beijing, 100084, China.
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Liu X, Ellens N, Williams E, Burdette EC, Karmarkar P, Weiss CR, Kraitchman D, Bottomley PA. High-resolution intravascular MRI-guided perivascular ultrasound ablation. Magn Reson Med 2019; 83:240-253. [PMID: 31402512 DOI: 10.1002/mrm.27932] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 06/24/2019] [Accepted: 07/15/2019] [Indexed: 12/22/2022]
Abstract
PURPOSE To develop and test in animal studies ex vivo and in vivo, an intravascular (IV) MRI-guided high-intensity focused ultrasound (HIFU) ablation method for targeting perivascular pathology with minimal injury to the vessel wall. METHODS IV-MRI antennas were combined with 2- to 4-mm diameter water-cooled IV-ultrasound ablation catheters for IV-MRI on a 3T clinical MRI scanner. A software interface was developed for monitoring thermal dose with real-time MRI thermometry, and an MRI-guided ablation protocol developed by repeat testing on muscle and liver tissue ex vivo. MRI thermal dose was measured as cumulative equivalent minutes at 43°C (CEM43 ). The IV-MRI IV-HIFU protocol was then tested by targeting perivascular ablations from the inferior vena cava of 2 pigs in vivo. Thermal dose and lesions were compared by gross and histological examination. RESULTS Ex vivo experiments yielded a 6-min ablation protocol with the IV-ultrasound catheter coolant at 3-4°C, a 30 mL/min flow rate, and 7 W ablation power. In 8 experiments, 5- to 10-mm thick thermal lesions of area 0.5-2 cm2 were produced that spared 1- to 2-mm margins of tissue abutting the catheters. The radial depths, areas, and preserved margins of ablation lesions measured from gross histology were highly correlated (r ≥ 0.79) with those measured from the CEM43 = 340 necrosis threshold determined by MRI thermometry. The psoas muscle was successfully targeted in the 2 live pigs, with the resulting ablations controlled under IV-MRI guidance. CONCLUSION IV-MRI-guided, IV-HIFU has potential as a precision treatment option that could preserve critical blood vessel wall during ablation of nonresectable perivascular tumors or other pathologies.
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Affiliation(s)
- Xiaoyang Liu
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland.,Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Nicholas Ellens
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland.,Acertara Acoustic Laboratories, Longmont, Colorado
| | | | | | - Parag Karmarkar
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Clifford R Weiss
- Division of Interventional Radiology, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Dara Kraitchman
- Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Paul A Bottomley
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland.,Division of MR Research, Department of Radiology, Johns Hopkins University, Baltimore, Maryland
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Wang G, Zhang Y, Hegde SS, Bottomley PA. High-resolution and accelerated multi-parametric mapping with automated characterization of vessel disease using intravascular MRI. J Cardiovasc Magn Reson 2017; 19:89. [PMID: 29157260 PMCID: PMC5694914 DOI: 10.1186/s12968-017-0399-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 10/16/2017] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND Atherosclerosis is prevalent in cardiovascular disease, but present imaging modalities have limited capabilities for characterizing lesion stage, progression and response to intervention. This study tests whether intravascular magnetic resonance imaging (IVMRI) measures of relaxation times (T1, T2) and proton density (PD) in a clinical 3 Tesla scanner could characterize vessel disease, and evaluates a practical strategy for accelerated quantification. METHODS IVMRI was performed in fresh human artery segments and swine vessels in vivo, using fast multi-parametric sequences, 1-2 mm diameter loopless antennae and 200-300 μm resolution. T1, T2 and PD data were used to train a machine learning classifier (support vector machine, SVM) to automatically classify normal vessel, and early or advanced disease, using histology for validation. Disease identification using the SVM was tested with receiver operating characteristic curves. To expedite acquisition of T1, T2 and PD data for vessel characterization, the linear algebraic method ('SLAM') was modified to accommodate the antenna's highly-nonuniform sensitivity, and used to provide average T1, T2 and PD measurements from compartments of normal and pathological tissue segmented from high-resolution images at acceleration factors of R ≤ 18-fold. The results were validated using compartment-average measures derived from the high-resolution scans. RESULTS The SVM accurately classified ~80% of samples into the three disease classes. The 'area-under-the-curve' was 0.96 for detecting disease in 248 samples, with T1 providing the best discrimination. SLAM T1, T2 and PD measures for R ≤ 10 were indistinguishable from the true means of segmented tissue compartments. CONCLUSION High-resolution IVMRI measures of T1, T2 and PD with a trained SVM can automatically classify normal, early and advanced atherosclerosis with high sensitivity and specificity. Replacing relaxometric MRI with SLAM yields good estimates of T1, T2 and PD an order-of-magnitude faster to facilitate IVMRI-based characterization of vessel disease.
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Affiliation(s)
- Guan Wang
- Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, MD USA
- Division of MR Research, Department of Radiology and Radiological Sciences, Johns Hopkins University, Park building 310, 600 N Wolfe Street, Baltimore, MD 21287 USA
| | - Yi Zhang
- Division of MR Research, Department of Radiology and Radiological Sciences, Johns Hopkins University, Park building 310, 600 N Wolfe Street, Baltimore, MD 21287 USA
| | - Shashank Sathyanarayana Hegde
- Division of MR Research, Department of Radiology and Radiological Sciences, Johns Hopkins University, Park building 310, 600 N Wolfe Street, Baltimore, MD 21287 USA
| | - Paul A. Bottomley
- Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, MD USA
- Division of MR Research, Department of Radiology and Radiological Sciences, Johns Hopkins University, Park building 310, 600 N Wolfe Street, Baltimore, MD 21287 USA
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6
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Liu X, Ellens N, Williams E, Burdette EC, Karmarkar P, Bottomley P. A Combined Intravascular MRI Endoscope and Intravascular Ultrasound (IVUS) Transducer for High-Resolution Image-Guided Ablation. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2017; 25:1178. [PMID: 28761393 PMCID: PMC5533297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
An intravascular MRI (IMRI) loopless antenna is combined for the first time with an intravascular water-cooled ultrasound ablation transducer as a possible tool for providing high-resolution MRI-guided ablations of pathological tissue via intravascular access. High resolution anatomical MRI, and real-time MRI thermometry were used to monitor ablation delivery in phantoms and tissue specimens. Results show that IMRI can guide IVUS-mediated directional ablation with minimal image artifacts. This permits the monitoring of thermal dose and therapy titration while minimizing potential thermal damage to the vessel wall.
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Affiliation(s)
- Xiaoyang Liu
- Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
- Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States
| | - Nicholas Ellens
- Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
| | | | | | - Parag Karmarkar
- Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
| | - Paul Bottomley
- Russell H. Morgan Department of Radiology, Johns Hopkins University, Baltimore, MD, United States
- Electrical and Computer Engineering, Johns Hopkins University, Baltimore, MD, United States
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Patel K, Tarkin J, Serruys PW, Tenekecioglu E, Foin N, Zhang YJ, Crake T, Moon J, Mathur A, Bourantas CV. Invasive or non-invasive imaging for detecting high-risk coronary lesions? Expert Rev Cardiovasc Ther 2017; 15:165-179. [PMID: 28256179 DOI: 10.1080/14779072.2017.1297231] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
INTRODUCTION Advances in our understanding about atherosclerotic evolution have enabled us to identify specific plaque characteristics that are associated with coronary plaque vulnerability and cardiovascular events. With constant improvements in signal and image processing an arsenal of invasive and non-invasive imaging modalities have been developed that are capable of identifying these features allowing in vivo assessment of plaque vulnerability. Areas covered: This review article presents the available and emerging imaging modalities introduced to assess plaque morphology and biology, describes the evidence from the first large scale studies that evaluated the efficacy of invasive and non-invasive imaging in detecting lesions that are likely to progress and cause cardiovascular events and discusses the potential implications of the in vivo assessment of coronary artery pathology in the clinical setting. Expert commentary: Invasive imaging, with its high resolution, and in particular hybrid intravascular imaging appears as the ideal approach to study the mechanisms regulating atherosclerotic disease progression; whereas non-invasive imaging is expected to enable complete assessment of coronary tree pathology, detection of high-risk lesions, more accurate risk stratification and thus to allow a personalized treatment of vulnerable patients.
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Affiliation(s)
- Kush Patel
- a Barts Heart Centre, Barts Health NHS Trust , London , UK
| | - Jason Tarkin
- a Barts Heart Centre, Barts Health NHS Trust , London , UK.,b Division of Cardiovascular Medicine , University of Cambridge , Cambridge , UK
| | - Patrick W Serruys
- c Thoraxcenter , Erasmus Medical Centre , Rotterdam , The Netherlands.,d Faculty of Medicine , National Heart & Lung Institute, Imperial College , London , UK
| | | | - Nicolas Foin
- e National Heart Centre Singapore , Duke-NUS Medical School , Singapore
| | - Yao-Jun Zhang
- f Nanjing First Hospital , Nanjing Medical University , Nanjing , China
| | - Tom Crake
- a Barts Heart Centre, Barts Health NHS Trust , London , UK
| | - James Moon
- a Barts Heart Centre, Barts Health NHS Trust , London , UK
| | - Anthony Mathur
- a Barts Heart Centre, Barts Health NHS Trust , London , UK
| | - Christos V Bourantas
- a Barts Heart Centre, Barts Health NHS Trust , London , UK.,g Institute of Cardiovascular Sciences , University College London , London , UK
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Abstract
Non-invasive external magnetic resonance imaging (MRI) of large vessel atherosclerosis is a robust and promising imaging modality that can be applied for the evaluation of the atherosclerotic process in large vessels. However, it requires expertise for setup and time for data acquisition and analysis. Intravascular MRI is a promising tool, but its use remains at the pre-clinical stage within selected research groups. In this review, the current status and future role of intravascular MRI for atherosclerotic plaque characterization are summarized, along with important challenges which will be necessary to overcome prior to the wide adoption of this technique.
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Affiliation(s)
- João L Cavalcante
- Department of Medicine, Division of Cardiology, UPMC Heart & Vascular Institute, University of Pittsburgh, Pittsburgh, PA, USA
| | - Eric Larose
- Faculté de médecine, Université Laval, Quebec, Quebec, Canada.
- Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec - Université Laval, 2725 chemin Sainte-Foy, Quebec, Quebec, G1V 4G5, Canada.
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Ertürk MA, Sathyanarayana Hegde S, Bottomley PA. Radiofrequency Ablation, MR Thermometry, and High-Spatial-Resolution MR Parametric Imaging with a Single, Minimally Invasive Device. Radiology 2016; 281:927-932. [PMID: 27228330 DOI: 10.1148/radiol.2016151447] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Purpose To develop and demonstrate in vitro and in vivo a single interventional magnetic resonance (MR)-active device that integrates the functions of precise identification of a tissue site with the delivery of radiofrequency (RF) energy for ablation, high-spatial-resolution thermal mapping to monitor thermal dose, and quantitative MR imaging relaxometry to document ablation-induced tissue changes for characterizing ablated tissue. Materials and Methods All animal studies were approved by the institutional animal care and use committee. A loopless MR imaging antenna composed of a tuned microcable either 0.8 or 2.2 mm in diameter with an extended central conductor was switched between a 3-T MR imaging unit and an RF power source to monitor and perform RF ablation in bovine muscle and human artery samples in vitro and in rabbits in vivo. High-spatial-resolution (250-300-μm) proton resonance frequency shift MR thermometry was interleaved with ablations. Quantitative spin-lattice (T1) and spin-spin (T2) relaxation time MR imaging mapping was performed before and after ablation. These maps were compared with findings from gross tissue examination of the region of ablated tissue after MR imaging. Results High-spatial-resolution MR imaging afforded temperature mapping in less than 8 seconds for monitoring ablation temperatures in excess of 85°C delivered by the same device. This produced irreversible thermal injury and necrosis. Quantitative MR imaging relaxation time maps demonstrated up to a twofold variation in mean regional T1 and T2 after ablation versus before ablation. Conclusion A simple, integrated, minimally invasive interventional probe that provides image-guided therapy delivery, thermal mapping of dose, and detection of ablation-associated MR imaging parametric changes was developed and demonstrated. With this single-device approach, coupling-related safety concerns associated with multiple conductor approaches were avoided. © RSNA, 2016 Online supplemental material is available for this article.
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Affiliation(s)
- M Arcan Ertürk
- From the Department of Radiology, Johns Hopkins University, 600 N Wolfe St, Park 310, Baltimore, MD 21287
| | | | - Paul A Bottomley
- From the Department of Radiology, Johns Hopkins University, 600 N Wolfe St, Park 310, Baltimore, MD 21287
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Erturk MA, Hegde SS, Bottomley PA. A combined interventional high-resolution targeted ablation, thermometry and imaging probe. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2015; 23:1645. [PMID: 27570494 PMCID: PMC4999296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Affiliation(s)
- M Arcan Erturk
- Radiology, Johns Hopkins University, Baltimore, Maryland, United States; Center for Magnetic Resonance Research, University of Minnesota Medical School, Minnesota, United States
| | | | - Paul A Bottomley
- Radiology, Johns Hopkins University, Baltimore, Maryland, United States
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11
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Hegde SS, Zhang Y, Bottomley PA. Acceleration and motion-correction techniques for high-resolution intravascular MRI. Magn Reson Med 2014; 74:452-61. [PMID: 25163750 DOI: 10.1002/mrm.25436] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 08/06/2014] [Accepted: 08/11/2014] [Indexed: 11/07/2022]
Abstract
PURPOSE High-resolution intravascular (IV) MRI is susceptible to degradation from physiological motion and requires high frame-rates for true endoscopy. Traditional cardiac-gating techniques compromise efficiency by reducing the effective scan rate. Here we test whether compressed sensing (CS) reconstruction and ungated motion-compensation using projection shifting, could provide faster motion-suppressed, IVMRI. THEORY AND METHODS CS reconstruction is developed for undersampled Cartesian and radial imaging using a new IVMRI-specific cost function to effectively increase imaging speed. A new motion correction method is presented wherein individual IVMRI projections are shifted based on the IVMRI detector's intrinsic amplitude and phase properties. The methods are tested at 3 Tesla (T) in fruit, human vessel specimens, and a rabbit aorta in vivo. Images are compared using structural-similarity and "spokal variation" indices. RESULTS Although some residual artifacts persisted, CS acceleration and radial motion compensation strategies reduced motion artifact in vitro and in vivo, allowing effective accelerations of up to eight-fold at 200-300 µm resolution. CONCLUSION The 3T IVMRI detectors are well-suited to CS and motion correction strategies based on their intrinsic radially-sparse sensitivity profiles and high signal-to-noise ratios.
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Affiliation(s)
- Shashank Sathyanarayana Hegde
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA
| | - Yi Zhang
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Paul A Bottomley
- Russell H. Morgan Department of Radiology & Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA.,Department of Electrical & Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA
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Chen Y, Duan YT, Xie Q, Qin XP, Chen B, Xia L, Zhou Y, Li NN, Wu XT. Magnetic endoscopic imaging vs standard colonoscopy: Meta-analysis of randomized controlled trials. World J Gastroenterol 2013; 19:7197-7204. [PMID: 24222966 PMCID: PMC3819558 DOI: 10.3748/wjg.v19.i41.7197] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 08/17/2013] [Accepted: 09/04/2013] [Indexed: 02/06/2023] Open
Abstract
AIM: To assess the theoretical advantages of magnetic endoscope imaging (MEI) over standard colonoscopies (SCs) and to compare their efficacies.
METHODS: Electronic databases, including PubMed, EMBASE, the Cochrane library and the Science Citation Index, were searched to retrieve relevant trials. In addition, abstracts from papers presented at professional meetings and the reference lists of retrieved articles were reviewed to identify additional studies. The meta-analyses were performed using RevMan 5.1. A random effect model with the Mantel-Haenszel method was used for pooling dichotomous and continuous data. A sensitivity analysis was performed by excluding the trials with a small number of patients and by excluding the trials performed by inexperienced providers.
RESULTS: Eight randomized controlled trials (RCTs), including 2967 patients, were included in the meta-analysis to compare cecal intubation rates and times, sedation dose, abdominal pain scores and the use of ancillary maneuvers between MEI and SC. The overall OR was 1.92 (95%CI: 1.13-3.27, eight RCTs), as indicated by the cecal intubation rate of MEI compared with SC, but MEI did not have any distinct advantage over SC for cecal intubation time (MD = -0.07, 95%CI: -0.16-0.02; three RCTs). MEI did not generally result in lower pain scores. Outcomes were also analyzed for the two subgroups based on the endoscopists’ experience level to evaluate cecal intubation rates. MEI presented better outcomes for non-experienced colonoscopists than experienced colonoscopists.
CONCLUSION: The real-time magnetic imaging system is of benefit in training and educating inexperienced endoscopists and improves the cecal intubation rate for experienced and inexperienced endoscopists.
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Karimi H, Dominguez-Viqueira W, Cunningham CH. Spatial encoding using the nonlinear field perturbations from magnetic materials. Magn Reson Med 2013; 72:399-408. [PMID: 24105884 DOI: 10.1002/mrm.24950] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Revised: 08/19/2013] [Accepted: 08/20/2013] [Indexed: 11/07/2022]
Abstract
PURPOSE A proof-of-concept study was performed to assess the technical feasibility of using magnetic materials to generate spatial encoding fields. THEORY AND METHODS Spatially varying magnetic fields were generated by the placement of markers with different volume susceptibilities within the imaging volume. No linear gradients were used for spatial encoding during the signal acquisition. A signal-encoding model is described for reconstructing the images encoded with these field perturbations. Simulation and proof-of-concept experimental results are presented. Experiments were performed using field perturbations from a cylindrical marker as an example of the new encoding fields. Based on this experimental setup, annular rings were reconstructed from signals encoded with the new fields. RESULTS Simulation results were presented for different acquisition parameters. Proof-of-concept was supported by the correspondence of regions in an image reconstructed from experimental data compared to those in a conventional gradient-echo image. Experimental results showed that inclusions of dimensions 1.5 mm in size could be resolved with the experimental setup. CONCLUSION This study shows the technical feasibility of using magnetic markers to produce encoding fields. Magnetic materials will allow generating spatial encoding fields, which can be tailored to an imaging application with less complexity and at lower cost compared to the use of gradient inserts.
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Affiliation(s)
- Hirad Karimi
- Department of Medical Biophysics, University of Toronto, Toronto, Canada; Sunnybrook Research Institute, Physical Sciences Department, Toronto, Ontario, Canada
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Erturk MA, El-Sharkawy AMM, Moore J, Bottomley PA. 7 Tesla MRI with a transmit/receive loopless antenna and B1-insensitive selective excitation. Magn Reson Med 2013; 72:220-6. [PMID: 23963978 DOI: 10.1002/mrm.24910] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2013] [Revised: 06/25/2013] [Accepted: 07/15/2013] [Indexed: 11/10/2022]
Abstract
PURPOSE Use of external coils with internal detectors or conductors is challenging at 7 Tesla (T) due to radiofrequency (RF) field (B1 ) penetration, B1 -inhomogeneity, mutual coupling, and potential local RF heating. The present study tests whether the near-quadratic gains in signal-to-noise ratio and field-of-view with field-strength previously reported for internal loopless antennae at 7T can suffice to perform MRI with an interventional transmit/receive antenna without using any external coils. METHODS External coils were replaced by semi-rigid or biocompatible transmit/receive loopless antennae requiring only a few Watts of peak RF power. Slice selection was provided by spatially selective B1 -insensitive composite RF pulses that compensate for the antenna's intrinsically nonuniform B1 -field. Power was adjusted to maintain local temperature rise ≤1°C. Fruit, intravascular MRI of diseased human vessels in vitro, and MRI of rabbit aorta in vivo are demonstrated. RESULTS Scout MRI with the transmit/receive antennae yielded a ≤10 cm cylindrical field-of-view, enabling subsequent targeted localization at ∼100 μm resolution in 10-50 s and/or 50 μm MRI in ∼2 min in vitro, and 100-300 μm MRI of the rabbit aorta in vivo. CONCLUSION A simple, low-power, one-device approach to interventional MRI at 7T offers the potential of truly high-resolution MRI, while avoiding issues with external coil excitation and interactions at 7T.
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Affiliation(s)
- M Arcan Erturk
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, USA; Russell H. Morgan Department of Radiology and Radiological Sciences, Johns Hopkins University, Baltimore, Maryland, USA
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Early detection and invasive passivation of future culprit lesions: a future potential or an unrealistic pursuit of chimeras? Am Heart J 2013; 165:869-881.e4. [PMID: 23708157 DOI: 10.1016/j.ahj.2013.02.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 02/18/2013] [Indexed: 11/22/2022]
Abstract
New advances in image and signal processing have allowed the development of numerous invasive and noninvasive imaging modalities that have revealed details of plaque pathology and allowed us to study in vivo the atherosclerotic evolution. Recent natural history of atherosclerosis studies permitted us to evaluate changes in the compositional and morphological characteristics of the plaque and identify predictors of future events. The idea of being able to identify future culprit lesions and passivate these plaques has gradually matured, and small scale studies have provided proofs about the feasibility of this concept. This review article summarizes the recent advances in the study of atherosclerosis, cites the current evidence, highlights our limitations in understanding the evolution of the plaque and in predicting plaque destabilization, and discusses the potentiality of an early invasive sealing of future culprit lesions.
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Hegde SS, Zhang Y, Bottomley PA. Accelerated, motion-corrected high-resolution intravascular MRI at 3T. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2013; 21:0473-473. [PMID: 25346624 PMCID: PMC4207268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
| | - Yi Zhang
- Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States
| | - Paul A Bottomley
- Radiology, Johns Hopkins University, Baltimore, Maryland, United States
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Qian D, Bottomley PA. High-resolution intravascular magnetic resonance quantification of atherosclerotic plaque at 3T. J Cardiovasc Magn Reson 2012; 14:20. [PMID: 22448884 PMCID: PMC3340302 DOI: 10.1186/1532-429x-14-20] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 03/26/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The thickness of fibrous caps (FCT) of atherosclerotic lesions is a critical factor affecting plaque vulnerability to rupture. This study tests whether 3 Tesla high-resolution intravascular cardiovascular magnetic resonance (CMR) employing tiny loopless detectors can identify lesions and accurately measure FCT in human arterial specimens, and whether such an approach is feasible in vivo using animal models. METHODS Receive-only 2.2 mm and 0.8 mm diameter intravascular loopless CMR detectors were fabricated for a clinical 3 Tesla MR scanner, and the absolute signal-to-noise ratio determined. The detectors were applied in a two-step protocol comprised of CMR angiography to identify atherosclerotic lesions, followed by high-resolution CMR to characterize FCT, lesion size, and/or vessel wall thickness. The protocol was applied in fresh human iliac and carotid artery specimens in a human-equivalent saline bath. Mean FCT measured by 80 μm intravascular CMR was compared with histology of the same sections. In vivo studies compared aortic wall thickness and plaque size in healthy and hyperlipidemic rabbit models, with post-mortem histology. RESULTS Histology confirmed plaques in human specimens, with calcifications appearing as signal voids. Mean FCT agreed with histological measurements within 13% on average (correlation coefficient, R = 0.98; Bland-Altman analysis, -1.3 ± 68.9 μm). In vivo aortic wall and plaque size measured by 80 μm intravascular CMR agreed with histology. CONCLUSION Intravascular 3T CMR with loopless detectors can both locate atherosclerotic lesions, and accurately measure FCT at high-resolution in a strategy that appears feasible in vivo. The approach shows promise for quantifying vulnerable plaque for evaluating experimental therapies.
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Affiliation(s)
- Di Qian
- Division of MR Research, Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, USA
| | - Paul A Bottomley
- Division of MR Research, Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, MD, USA
- Division of MR Research, Department of Radiology and Radiological Science, Johns Hopkins School of Medicine, 600 N Wolfe St, Park 310, Baltimore, MD, USA
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Erturk MA, El-Sharkawy AMM, Bottomley PA. The Interventional Loopless Antenna at 7 Tesla. PROCEEDINGS OF THE INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE ... SCIENTIFIC MEETING AND EXHIBITION. INTERNATIONAL SOCIETY FOR MAGNETIC RESONANCE IN MEDICINE. SCIENTIFIC MEETING AND EXHIBITION 2012; 2012:2944. [PMID: 25346623 PMCID: PMC4207296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Mehmet Arcan Erturk
- Electrical & Computer Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States ; Department of Radiology, Johns Hopkins University, Baltimore, Maryland, United States
| | | | - Paul A Bottomley
- Electrical & Computer Engineering Department, Johns Hopkins University, Baltimore, Maryland, United States ; Department of Radiology, Johns Hopkins University, Baltimore, Maryland, United States
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Ertürk MA, El-Sharkawy AMM, Bottomley PA. Interventional loopless antenna at 7 T. Magn Reson Med 2011; 68:980-8. [PMID: 22161992 DOI: 10.1002/mrm.23280] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2011] [Revised: 09/02/2011] [Accepted: 10/10/2011] [Indexed: 11/12/2022]
Abstract
The loopless antenna magnetic resonance imaging detector is comprised of a tuned coaxial cable with an extended central conductor that can be fabricated at submillimeter diameters for interventional use in guidewires, catheters, or needles. Prior work up to 4.7 T suggests a near-quadratic gain in signal-to-noise ratio with field strength and safe operation at 3 T. Here, for the first time, the signal-to-noise ratio performance and radiofrequency safety of the loopless antenna are investigated both theoretically, using the electromagnetic method-of-moments, and experimentally in a standard 7 T human scanner. The results are compared with equivalent 3 T devices. An absolute signal-to-noise ratio gain of 5.7 ± 1.5-fold was realized at 7 T vs. 3 T: more than 20-fold higher than at 1.5 T. The effective field-of-view area also increased approximately 10-fold compared with 3 T. Testing in a saline gel phantom suggested that safe operation is possible with maximum local 1-g average specific absorption rates of <12 W kg(-1) and temperature increases of <1.9°C, normalized to a 4 W kg(-1) radiofrequency field exposure at 7 T. The antenna did not affect the power applied to the scanner's transmit coil. The signal-to-noise ratio gain enabled magnetic resonance imaging microscopy at 40-50 μm resolution in diseased human arterial specimens, offering the potential of high-resolution large-field-of-view or endoscopic magnetic resonance imaging for targeted intervention in focal disease.
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Affiliation(s)
- Mehmet Arcan Ertürk
- Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, United States of America
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Yu SS, Ortega RA, Reagan BW, McPherson JA, Sung HJ, Giorgio TD. Emerging applications of nanotechnology for the diagnosis and management of vulnerable atherosclerotic plaques. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2011; 3:620-46. [PMID: 21834059 DOI: 10.1002/wnan.158] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
An estimated 16 million people in the United States have coronary artery disease (CAD), and approximately 325,000 people die annually from cardiac arrest. About two-thirds of unexpected cardiac deaths occur without prior recognition of cardiac disease. A vast majority of these deaths are attributable to the rupture of 'vulnerable atherosclerotic plaques'. Clinically, plaque vulnerability is typically assessed through imaging techniques, and ruptured plaques leading to acute myocardial infarction are treated through angioplasty or stenting. Despite significant advances, it is clear that current imaging methods are insufficiently capable for elucidating plaque composition--which is a key determinant of vulnerability. Further, the exciting improvement in the treatment of CAD afforded by stenting procedures has been buffered by significant undesirable host-implant effects, including restenosis and late thrombosis. Nanotechnology has led to some potential solutions to these problems by yielding constructs that interface with plaque cellular components at an unprecedented size scale. By leveraging the innate ability of macrophages to phagocytose nanoparticles, contrast agents can now be targeted to plaque inflammatory activity. Improvements in nano-patterning procedures have now led to increased ability to regenerate tissue isotropy directly on stents, enabling gradual regeneration of normal, physiologic vascular structures. Advancements in immunoassay technologies promise lower costs for biomarker measurements, and in the near future, may enable the addition of routine blood testing to the clinician's toolbox--decreasing the costs of atherosclerosis-related medical care. These are merely three examples among many stories of how nanotechnology continues to promise advances in the diagnosis and treatment of vulnerable atherosclerotic plaques.
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Affiliation(s)
- Shann S Yu
- Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA
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Lederman RJ, Faranesh AZ. Getting closer for high-resolution vascular MRI. JACC Cardiovasc Imaging 2011; 3:1166-7. [PMID: 21071005 DOI: 10.1016/j.jcmg.2010.09.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 09/16/2010] [Indexed: 11/25/2022]
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Kramer CM, Narula J. Whither catheter-based intravascular magnetic resonance imaging of atherosclerosis? JACC Cardiovasc Imaging 2011; 3:1203-4. [PMID: 21071014 DOI: 10.1016/j.jcmg.2010.10.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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