Publications by authors named "Nicole Seiberlich"

73 Publications

Characterization of cardiac amyloidosis using cardiac magnetic resonance fingerprinting.

Int J Cardiol 2021 Dec 25. Epub 2021 Dec 25.

Imaging Institute, Heart, Vascular, and Thoracic Institute, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.

Background: Cardiac amyloidosis (CA) is an infiltrative cardiomyopathy with poor prognosis absent appropriate treatment. Elevated native myocardial T and T have been reported for CA, and tissue characterization by cardiac MRI may expedite diagnosis and treatment. Cardiac Magnetic Resonance Fingerprinting (cMRF) has the potential to enable tissue characterization for CA through rapid, simultaneous T and T mapping. Furthermore, cMRF signal timecourses may provide additional information beyond myocardial T and T.

Methods: Nine CA patients and five controls were scanned at 3 T using a prospectively gated cMRF acquisition. Two cMRF-based analysis approaches were examined: (1) relaxometric-based linear discriminant analysis (LDA) using native T and T, and (2) signal timecourse-based LDA. The Fisher coefficient was used to compare the separability of patient and control groups from both approaches. Leave-two-out cross-validation was employed to evaluate the classification error rates of both approaches.

Results: Elevated myocardial T and T was observed in patients vs controls (T: 1395 ± 121 vs 1240 ± 36.4 ms, p < 0.05; T: 36.8 ± 3.3 vs 31.8 ± 2.6 ms, p < 0.05). LDA scores were elevated in patients for relaxometric-based LDA (0.56 ± 0.28 vs 0.18 ± 0.13, p < 0.05) and timecourse-based LDA (0.97 ± 0.02 vs 0.02 ± 0.02, p < 0.05). The Fisher coefficient was greater for timecourse-based LDA (60.8) vs relaxometric-based LDA (1.6). Classification error rates were lower for timecourse-based LDA vs relaxometric-based LDA (12.6 ± 24.3 vs 22.5 ± 30.1%, p < 0.05).

Conclusions: These findings suggest that cMRF may be a valuable technique for the detection and characterization of CA. Analysis of cMRF signal timecourse data may improve tissue characterization as compared to analysis of native T and T alone.
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http://dx.doi.org/10.1016/j.ijcard.2021.12.038DOI Listing
December 2021

A System for Real-Time, Online Mixed-Reality Visualization of Cardiac Magnetic Resonance Images.

J Imaging 2021 Dec 14;7(12). Epub 2021 Dec 14.

Department of Radiology, University of Michigan, Ann Arbor, MI 48109, USA.

Image-guided cardiovascular interventions are rapidly evolving procedures that necessitate imaging systems capable of rapid data acquisition and low-latency image reconstruction and visualization. Compared to alternative modalities, Magnetic Resonance Imaging (MRI) is attractive for guidance in complex interventional settings thanks to excellent soft tissue contrast and large fields-of-view without exposure to ionizing radiation. However, most clinically deployed MRI sequences and visualization pipelines exhibit poor latency characteristics, and spatial integration of complex anatomy and device orientation can be challenging on conventional 2D displays. This work demonstrates a proof-of-concept system linking real-time cardiac MR image acquisition, online low-latency reconstruction, and a stereoscopic display to support further development in real-time MR-guided intervention. Data are acquired using an undersampled, radial trajectory and reconstructed via parallelized through-time radial generalized autocalibrating partially parallel acquisition (GRAPPA) implemented on graphics processing units. Images are rendered for display in a stereoscopic mixed-reality head-mounted display. The system is successfully tested by imaging standard cardiac views in healthy volunteers. Datasets comprised of one slice (46 ms), two slices (92 ms), and three slices (138 ms) are collected, with the acquisition time of each listed in parentheses. Images are displayed with latencies of 42 ms/frame or less for all three conditions. Volumetric data are acquired at one volume per heartbeat with acquisition times of 467 ms and 588 ms when 8 and 12 partitions are acquired, respectively. Volumes are displayed with a latency of 286 ms or less. The faster-than-acquisition latencies for both planar and volumetric display enable real-time 3D visualization of the heart.
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http://dx.doi.org/10.3390/jimaging7120274DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8709155PMC
December 2021

Differential Image Based Robot to MRI Scanner Registration with Active Fiducial Markers for an MRI-Guided Robotic Catheter System.

Rep U S 2020 Oct 10;2020:2958-2964. Epub 2021 Feb 10.

Department of Electrical, Computer, and Systems Engineering, Case Western Reserve University, Cleveland, OH, USA.

In magnetic resonance imaging (MRI) guided robotic catheter ablation procedures, reliable tracking of the catheter within the MRI scanner is needed to safely navigate the catheter. This requires accurate registration of the catheter to the scanner. This paper presents a differential, multi-slice image-based registration approach utilizing active fiducial coils. The proposed method would be used to preoperatively register the MRI image space with the physical catheter space. In the proposed scheme, the registration is performed with the help of a registration frame, which has a set of embedded electromagnetic coils designed to actively create MRI image artifacts. These coils are detected in the MRI scanner's coordinate system by background subtraction. The detected coil locations in each slice are weighted by the artifact size and then registered to known ground truth coil locations in the catheter's coordinate system via least-squares fitting. The proposed approach is validated by using a set of target coils placed withing the workspace, employing multi-planar capabilities of the MRI scanner. The average registration and validation errors are respectively computed as 1.97 mm and 2.49 mm. The multi-slice approach is also compared to the single-slice method and shown to improve registration and validation by respectively 0.45 mm and 0.66 mm.
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http://dx.doi.org/10.1109/iros45743.2020.9341043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8202025PMC
October 2020

Prospective Evaluation of Repeatability and Robustness of Radiomic Descriptors in Healthy Brain Tissue Regions In Vivo Across Systematic Variations in T2-Weighted Magnetic Resonance Imaging Acquisition Parameters.

J Magn Reson Imaging 2021 09 16;54(3):1009-1021. Epub 2021 Apr 16.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA.

Background: Radiomic descriptors from magnetic resonance imaging (MRI) are promising for disease diagnosis and characterization but may be sensitive to differences in imaging parameters.

Objective: To evaluate the repeatability and robustness of radiomic descriptors within healthy brain tissue regions on prospectively acquired MRI scans; in a test-retest setting, under controlled systematic variations of MRI acquisition parameters, and after postprocessing.

Study Type: Prospective.

Subjects: Fifteen healthy participants.

Field Strength/sequence: A 3.0 T, axial T -weighted 2D turbo spin-echo pulse sequence, 181 scans acquired (2 test/retest reference scans and 12 with systematic variations in contrast weighting, resolution, and acceleration per participant; removing scans with artifacts).

Assessment: One hundred and forty-six radiomic descriptors were extracted from a contiguous 2D region of white matter in each scan, before and after postprocessing.

Statistical Tests: Repeatability was assessed in a test/retest setting and between manual and automated annotations for the reference scan. Robustness was evaluated between the reference scan and each group of variant scans (contrast weighting, resolution, and acceleration). Both repeatability and robustness were quantified as the proportion of radiomic descriptors that fell into distinct ranges of the concordance correlation coefficient (CCC): excellent (CCC > 0.85), good (0.7 ≤ CCC ≤ 0.85), moderate (0.5 ≤ CCC < 0.7), and poor (CCC < 0.5); for unprocessed and postprocessed scans separately.

Results: Good to excellent repeatability was observed for 52% of radiomic descriptors between test/retest scans and 48% of descriptors between automated vs. manual annotations, respectively. Contrast weighting (TR/TE) changes were associated with the largest proportion of highly robust radiomic descriptors (21%, after processing). Image resolution changes resulted in the largest proportion of poorly robust radiomic descriptors (97%, before postprocessing). Postprocessing of images with only resolution/acceleration differences resulted in 73% of radiomic descriptors showing poor robustness.

Data Conclusions: Many radiomic descriptors appear to be nonrobust across variations in MR contrast weighting, resolution, and acceleration, as well in test-retest settings, depending on feature formulation and postprocessing.

Evidence Level: 2 TECHNICAL EFFICACY: Stage 2.
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http://dx.doi.org/10.1002/jmri.27635DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8376104PMC
September 2021

Cardiac magnetic resonance fingerprinting: Trends in technical development and potential clinical applications.

Prog Nucl Magn Reson Spectrosc 2021 02 6;122:11-22. Epub 2020 Nov 6.

Department of Radiology, University of Michigan, 1150 West Medical Center Drive, Ann Arbor, MI 48109, USA. Electronic address:

Quantitative cardiac magnetic resonance has emerged in recent years as an approach for evaluating a range of cardiovascular conditions, with T and T mapping at the forefront of these developments. Cardiac Magnetic Resonance Fingerprinting (cMRF) provides a rapid and robust framework for simultaneous quantification of myocardial T and T in addition to other tissue properties. Since the advent of cMRF, a number of technical developments and clinical validation studies have been reported. This review provides an overview of cMRF, recent technical developments, healthy subject and patient studies, anticipated technical improvements, and potential clinical applications. Recent technical developments include slice profile and pulse efficiency corrections, improvements in image reconstruction, simultaneous multislice imaging, 3D whole-ventricle imaging, motion-resolved imaging, fat-water separation, and machine learning for rapid dictionary generation. Future technical developments in cMRF, such as B and B field mapping, acceleration of acquisition and reconstruction, imaging of patients with implanted devices, and quantification of additional tissue properties are also described. Potential clinical applications include characterization of infiltrative, inflammatory, and ischemic cardiomyopathies, tissue characterization in the left atrium and right ventricle, post-cardiac transplantation assessment, reduction of contrast material, pre-procedural planning for electrophysiology interventions, and imaging of patients with implanted devices.
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http://dx.doi.org/10.1016/j.pnmrs.2020.10.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8366914PMC
February 2021

Machine Learning for Rapid Magnetic Resonance Fingerprinting Tissue Property Quantification.

Proc IEEE Inst Electr Electron Eng 2020 Jan 11;108(1):69-85. Epub 2019 Sep 11.

Department of Biomedical Engineering and the Department of Electrical Engineering and Computer Science, Case Western Reserve University, Cleveland, OH 44106 USA, the Department of Radiology and Cardiology, University Hospitals, Cleveland, OH 44106 USA, and the Department of Radiology, University of Michigan, Ann Arbor, MI 48109.

Magnetic Resonance Fingerprinting (MRF) is an MRI-based method that can provide quantitative maps of multiple tissue properties simultaneously from a single rapid acquisition. Tissue property maps are generated by matching the complex signal evolutions collected at the scanner to a dictionary of signals derived using Bloch equation simulations. However, in some circumstances, the process of dictionary generation and signal matching can be time-consuming, reducing the utility of this technique. Recently, several groups have proposed using machine learning to accelerate the extraction of quantitative maps from MRF data. This article will provide an overview of current research that combines MRF and machine learning, as well as present original research demonstrating how machine learning can speed up dictionary generation for cardiac MRF.
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http://dx.doi.org/10.1109/JPROC.2019.2936998DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595247PMC
January 2020

Deep learning reconstruction for cardiac magnetic resonance fingerprinting T and T mapping.

Magn Reson Med 2021 04 26;85(4):2127-2135. Epub 2020 Oct 26.

Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.

Purpose: To develop a deep learning method for rapidly reconstructing T and T maps from undersampled electrocardiogram (ECG) triggered cardiac magnetic resonance fingerprinting (cMRF) images.

Methods: A neural network was developed that outputs T and T values when given a measured cMRF signal time course and cardiac RR interval times recorded by an ECG. Over 8 million cMRF signals, corresponding to 4000 random cardiac rhythms, were simulated for training. The training signals were corrupted by simulated k-space undersampling artifacts and random phase shifts to promote robust learning. The deep learning reconstruction was evaluated in Monte Carlo simulations for a variety of cardiac rhythms and compared with dictionary-based pattern matching in 58 healthy subjects at 1.5T.

Results: In simulations, the normalized root-mean-square error (nRMSE) for T was below 1% in myocardium, blood, and liver for all tested heart rates. For T , the nRMSE was below 4% for myocardium and liver and below 6% for blood for all heart rates. The difference in the mean myocardial T or T observed in vivo between dictionary matching and deep learning was 3.6 ms for T and -0.2 ms for T . Whereas dictionary generation and pattern matching required more than 4 min per slice, the deep learning reconstruction only required 336 ms.

Conclusion: A neural network is introduced for reconstructing cMRF T and T maps directly from undersampled spiral images in under 400 ms and is robust to arbitrary cardiac rhythms, which paves the way for rapid online display of cMRF maps.
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http://dx.doi.org/10.1002/mrm.28568DOI Listing
April 2021

Evaluation of dyspnea of unknown etiology in HIV patients with cardiopulmonary exercise testing and cardiovascular magnetic resonance imaging.

J Cardiovasc Magn Reson 2020 10 12;22(1):74. Epub 2020 Oct 12.

Harrington Heart and Vascular Institute, University Hospitals, Cleveland, OH, USA.

Aim: Human Immunodeficiency Virus (HIV) patients commonly experience dyspnea for which an immediate cause may not be always apparent. In this prospective cohort study of HIV patients with exercise limitation, we use cardiopulmonary exercise testing (CPET) coupled with exercise cardiovascular magnetic resonance (CMR) to elucidate etiologies of dyspnea.

Methods And Results: Thirty-four HIV patients on antiretroviral therapy with dyspnea and exercise limitation (49.7 years, 65% male, mean absolute CD4 count 700) underwent comprehensive evaluation with combined rest and maximal exercise treadmill CMR and CPET. The overall mean oxygen consumption (VO) peak was reduced at 23.2 ± 6.9 ml/kg/min with 20 patients (58.8% of overall cohort) achieving a respiratory exchange ratio > 1. The ventilatory efficiency (VE)/VCO slope was elevated at 36 ± 7.92, while ventilatory reserve (VE: maximal voluntary ventilation (MVV)) was within normal limits. The mean absolute right ventricular (RV) and left ventricular (LV) contractile reserves were preserved at 9.0% ± 11.2 and 9.4% ± 9.4, respectively. The average resting and post-exercise mean average pulmonary artery velocities were 12.2 ± 3.9 cm/s and 18.9 ± 8.3 respectively, which suggested lack of exercise induced pulmonary artery hypertension (PAH). LV but not RV delayed enhancement were identified in five patients. Correlation analysis found no relationship between peak VO measures of contractile RV or LV reserve, but LV and RV stroke volume correlated with PET CO (p = 0.02, p = 0.03).

Conclusion: Well treated patients with HIV appear to have conserved RV and LV function, contractile reserve and no evidence of exercise induced PAH. However, we found evidence of impaired ventilation suggesting a non-cardiopulmonary etiology for dyspnea.
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http://dx.doi.org/10.1186/s12968-020-00664-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7549205PMC
October 2020

Magnetic Resonance Fingerprinting: Implications and Opportunities for PET/MR.

IEEE Trans Radiat Plasma Med Sci 2019 Jul 4;3(4):388-399. Epub 2019 Feb 4.

Department of Radiology, Case Western Reserve University, Cleveland, OH 44106 USA.

Magnetic Resonance Imaging (MRI) can be used to assess anatomical structure, and its sensitivity to a variety of tissue properties enables superb contrast between tissues as well as the ability to characterize these tissues. However, despite vast potential for quantitative and functional evaluation, MRI is typically used qualitatively, in which the underlying tissue properties are not measured, and thus the brightness of each pixel is not quantitatively meaningful. Positron Emission Tomography (PET) is an inherently quantitative imaging modality that interrogates functional activity within a tissue, probed by a molecule of interest coupled with an appropriate tracer. These modalities can complement one another to provide clinical information regarding both structure and function, but there are still technical and practical hurdles in the way of the integrated use of both modalities. Recent advances in MRI have moved the field in an increasingly quantitative direction, which is complementary to PET, and could also potentially help solve some of the challenges in PET/MR. Magnetic Resonance Fingerprinting (MRF) is a recently described MRI-based technique which can efficiently and simultaneously quantitatively map several tissue properties in a single exam. Here, the basic principles behind the quantitative approach of MRF are laid out, and the potential implications for combined PET/MR are discussed.
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http://dx.doi.org/10.1109/trpms.2019.2897425DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7454032PMC
July 2019

Myocardial T and T quantification and water-fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T.

Magn Reson Med 2021 01 27;85(1):103-119. Epub 2020 Jul 27.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.

Purpose: This work aims to develop an approach for simultaneous water-fat separation and myocardial T and T quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

Methods: Two 15-heartbeat cMRF sequences with different rosette trajectories designed for water-fat separation at 3T and 1.5T were implemented. Water T and T maps, water image, and fat image were generated with B inhomogeneity correction using a B map derived from the cMRF data themselves. The proposed water-fat separation rosette cMRF approach was validated in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and water/oil phantoms. It was also applied for myocardial tissue mapping of healthy subjects at both 3T and 1.5T.

Results: Water T and T values measured using rosette cMRF in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology phantom agreed well with the reference values. In the water/oil phantom, oil was well suppressed in the water images and vice versa. Rosette cMRF yielded comparable T but 2~3 ms higher T values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

Conclusion: Rosette cMRF provides fat images along with myocardial T and T maps with significant fat suppression. This technique may improve visualization of the anatomical structure of the heart by separating water and fat and could provide value in diagnosing cardiac diseases associated with fibrofatty infiltration or epicardial fat accumulation. It also paves the way toward comprehensive myocardial tissue characterization in a single scan.
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http://dx.doi.org/10.1002/mrm.28404DOI Listing
January 2021

Quantifying Perfusion Properties with DCE-MRI Using a Dictionary Matching Approach.

Sci Rep 2020 06 23;10(1):10210. Epub 2020 Jun 23.

Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.

Perfusion properties can be estimated from pharmacokinetic models applied to DCE-MRI data using curve fitting algorithms; however, these suffer from drawbacks including the local minimum problem and substantial computational time. Here, a dictionary matching approach is proposed as an alternative. Curve fitting and dictionary matching were applied to simulated data using the dual-input single-compartment model with known perfusion property values and 5 in vivo DCE-MRI datasets. In simulation at SNR 60 dB, the dictionary estimate had a mean percent error of 0.4-1.0% for arterial fraction, 0.5-1.4% for distribution volume, and 0.0% for mean transit time. The curve fitting estimate had a mean percent error of 1.1-2.1% for arterial fraction, 0.5-1.3% for distribution volume, and 0.2-1.8% for mean transit time. In vivo, dictionary matching and curve fitting showed no statistically significant differences in any of the perfusion property measurements in any of the 10 ROIs between the methods. In vivo, the dictionary method performed over 140-fold faster than curve fitting, obtaining whole volume perfusion maps in just over 10 s. This study establishes the feasibility of using a dictionary matching approach as a new and faster way of estimating perfusion properties from pharmacokinetic models in DCE-MRI.
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http://dx.doi.org/10.1038/s41598-020-66985-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7311534PMC
June 2020

Cardiac cine magnetic resonance fingerprinting for combined ejection fraction, T and T quantification.

NMR Biomed 2020 08 5;33(8):e4323. Epub 2020 Jun 5.

Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.

This study introduces a technique called cine magnetic resonance fingerprinting (cine-MRF) for simultaneous T , T and ejection fraction (EF) quantification. Data acquired with a free-running MRF sequence are retrospectively sorted into different cardiac phases using an external electrocardiogram (ECG) signal. A low-rank reconstruction with a finite difference sparsity constraint along the cardiac motion dimension yields images resolved by cardiac phase. To improve SNR and precision in the parameter maps, these images are nonrigidly registered to the same phase and matched to a dictionary to generate T and T maps. Cine images for computing left ventricular volumes and EF are also derived from the same data. Cine-MRF was tested in simulations using a numerical relaxation phantom. Phantom and in vivo scans of 19 subjects were performed at 3 T during a 10.9 seconds breath-hold with an in-plane resolution of 1.6 x 1.6 mm and 24 cardiac phases. Left ventricular EF values obtained with cine-MRF agreed with the conventional cine images (mean bias -1.0%). Average myocardial T times in diastole/systole were 1398/1391 ms with cine-MRF, 1394/1378 ms with ECG-triggered cardiac MRF (cMRF) and 1234/1212 ms with MOLLI; and T values were 30.7/30.3 ms with cine-MRF, 32.6/32.9 ms with ECG-triggered cMRF and 37.6/41.0 ms with T -prepared FLASH. Cine-MRF and ECG-triggered cMRF relaxation times were in good agreement. Cine-MRF T values were significantly longer than MOLLI, and cine-MRF T values were significantly shorter than T -prepared FLASH. In summary, cine-MRF can potentially streamline cardiac MRI exams by combining left ventricle functional assessment and T -T mapping into one time-efficient acquisition.
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http://dx.doi.org/10.1002/nbm.4323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7772953PMC
August 2020

Simultaneous Mapping of T and T Using Cardiac Magnetic Resonance Fingerprinting in a Cohort of Healthy Subjects at 1.5T.

J Magn Reson Imaging 2020 10 28;52(4):1044-1052. Epub 2020 Mar 28.

Department of Radiology, University of Michigan, Ann Arbor, Michigan, USA.

Background: Cardiac MR fingerprinting (cMRF) is a novel technique for simultaneous T and T mapping.

Purpose: To compare T /T measurements, repeatability, and map quality between cMRF and standard mapping techniques in healthy subjects.

Study Type: Prospective.

Population: In all, 58 subjects (ages 18-60). FIELD STRENGTH/SEQUENCE: cMRF, modified Look-Locker inversion recovery (MOLLI), and T -prepared balanced steady-state free precession (bSSFP) at 1.5T.

Assessment: T /T values were measured in 16 myocardial segments at apical, medial, and basal slice positions. Test-retest and intrareader repeatability were assessed for the medial slice. cMRF and conventional mapping sequences were compared using ordinal and two alternative forced choice (2AFC) ratings.

Statistical Tests: Paired t-tests, Bland-Altman analyses, intraclass correlation coefficient (ICC), linear regression, one-way analysis of variance (ANOVA), and binomial tests.

Results: Average T measurements were: basal 1007.4±96.5 msec (cMRF), 990.0±45.3 msec (MOLLI); medial 995.0±101.7 msec (cMRF), 995.6±59.7 msec (MOLLI); apical 1006.6±111.2 msec (cMRF); and 981.6±87.6 msec (MOLLI). Average T measurements were: basal 40.9±7.0 msec (cMRF), 46.1±3.5 msec (bSSFP); medial 41.0±6.4 msec (cMRF), 47.4±4.1 msec (bSSFP); apical 43.5±6.7 msec (cMRF), 48.0±4.0 msec (bSSFP). A statistically significant bias (cMRF T larger than MOLLI T ) was observed in basal (17.4 msec) and apical (25.0 msec) slices. For T , a statistically significant bias (cMRF lower than bSSFP) was observed for basal (-5.2 msec), medial (-6.3 msec), and apical (-4.5 msec) slices. Precision was lower for cMRF-the average of the standard deviation measured within each slice was 102 msec for cMRF vs. 61 msec for MOLLI T , and 6.4 msec for cMRF vs. 4.0 msec for bSSFP T . cMRF and conventional techniques had similar test-retest repeatability as quantified by ICC (0.87 cMRF vs. 0.84 MOLLI for T ; 0.85 cMRF vs. 0.85 bSSFP for T ). In the ordinal image quality comparison, cMRF maps scored higher than conventional sequences for both T (all five features) and T (four features).

Data Conclusion: This work reports on myocardial T /T measurements in healthy subjects using cMRF and standard mapping sequences. cMRF had slightly lower precision, similar test-retest and intrareader repeatability, and higher scores for map quality.

Evidence Level: 2 TECHNICAL EFFICACY: Stage 1 J. Magn. Reson. Imaging 2020;52:1044-1052.
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http://dx.doi.org/10.1002/jmri.27155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7772954PMC
October 2020

Magnetic resonance fingerprinting review part 2: Technique and directions.

J Magn Reson Imaging 2020 04 25;51(4):993-1007. Epub 2019 Jul 25.

Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA.

Magnetic resonance fingerprinting (MRF) is a general framework to quantify multiple MR-sensitive tissue properties with a single acquisition. There have been numerous advances in MRF in the years since its inception. In this work we highlight some of the recent technical developments in MRF, focusing on sequence optimization, modifications for reconstruction and pattern matching, new methods for partial volume analysis, and applications of machine and deep learning. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:993-1007.
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http://dx.doi.org/10.1002/jmri.26877DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6980890PMC
April 2020

Repeatability and reproducibility of 3D MR fingerprinting relaxometry measurements in normal breast tissue.

J Magn Reson Imaging 2019 10 20;50(4):1133-1143. Epub 2019 Mar 20.

Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA.

Background: The 3D breast magnetic resonance fingerprinting (MRF) technique enables T and T mapping in breast tissues. Combined repeatability and reproducibility studies on breast T and T relaxometry are lacking.

Purpose: To assess test-retest and two-visit repeatability and interscanner reproducibility of the 3D breast MRF technique in a single-institution setting.

Study Type: Prospective.

Subjects: Eighteen women (median age 29 years, range, 22-33 years) underwent Visit 1 scans on scanner 1. Ten of these women underwent test-retest scan repositioning after a 10-minute interval. Thirteen women had Visit 2 scans within 7-15 days in same menstrual cycle. The remaining five women had Visit 2 scans in the same menstrual phase in next menstrual cycle. Five women were also scanned on scanner 2 at both visits for interscanner reproducibility.

Field Strength/sequence: Two 3T MR scanners with the 3D breast MRF technique.

Assessment: T and T MRF maps of both breasts.

Statistical Tests: Mean T and T values for normal fibroglandular tissues were quantified at all scans. For variability, between and within-subjects coefficients of variation (bCV and wCV, respectively) were assessed. Repeatability was assessed with Bland-Altman analysis and coefficient of repeatability (CR). Reproducibility was assessed with interscanner coefficient of variation (CoV) and Wilcoxon signed-rank test.

Results: The bCV at test-retest scans was 9-12% for T , 7-17% for T , wCV was <4% for T , and <7% for T . For two visits in same menstrual cycle, bCV was 10-15% for T , 13-17% for T , wCV was <7% for T and <5% for T . For two visits in the same menstrual phase, bCV was 6-14% for T , 15-18% for T , wCV was <7% for T , and <9% for T . For test-retest scans, CR for T and T were 130 msec and 11 msec. For two visit scans, CR was <290 msec for T and 10-14 msec for T . Interscanner CoV was 3.3-3.6% for T and 5.1-6.6% for T , with no differences between interscanner measurements (P = 1.00 for T , P = 0.344 for T ).

Data Conclusion: 3D breast MRF measurements are repeatable across scan timings and scanners and may be useful in clinical applications in breast imaging.

Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1133-1143.
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http://dx.doi.org/10.1002/jmri.26717DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750981PMC
October 2019

Partial volume mapping using magnetic resonance fingerprinting.

NMR Biomed 2019 05 1;32(5):e4082. Epub 2019 Mar 1.

Radiology, Case Western Reserve University, Cleveland, OH, USA.

Magnetic resonance fingerprinting (MRF) is a quantitative imaging technique that maps multiple tissue properties through pseudorandom signal excitation and dictionary-based reconstruction. The aim of this study is to estimate and validate partial volumes from MRF signal evolutions (PV-MRF), and to characterize possible sources of error. Partial volume model inversion (pseudoinverse) and dictionary-matching approaches to calculate brain tissue fractions (cerebrospinal fluid, gray matter, white matter) were compared in a numerical phantom and seven healthy subjects scanned at 3 T. Results were validated by comparison with ground truth in simulations and ROI analysis in vivo. Simulations investigated tissue fraction errors arising from noise, undersampling artifacts, and model errors. An expanded partial volume model was investigated in a brain tumor patient. PV-MRF with dictionary matching is robust to noise, and estimated tissue fractions are sensitive to model errors. A 6% error in pure tissue T resulted in average absolute tissue fraction error of 4% or less. A partial volume model within these accuracy limits could be semi-automatically constructed in vivo using k-means clustering of MRF-mapped relaxation times. Dictionary-based PV-MRF robustly identifies pure white matter, gray matter and cerebrospinal fluid, and partial volumes in subcortical structures. PV-MRF could also estimate partial volumes of solid tumor and peritumoral edema. We conclude that PV-MRF can attribute subtle changes in relaxation times to altered tissue composition, allowing for quantification of specific tissues which occupy a fraction of a voxel.
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http://dx.doi.org/10.1002/nbm.4082DOI Listing
May 2019

Parameter map error due to normal noise and aliasing artifacts in MR fingerprinting.

Magn Reson Med 2019 05 23;81(5):3108-3123. Epub 2019 Jan 23.

Physics, Case Western Reserve University, Cleveland, Ohio.

Purpose: To introduce a quantitative tool that enables rapid forecasting of T and T parameter map errors due to normal and aliasing noise as a function of the MR fingerprinting (MRF) sequence, which can be used in sequence optimization.

Theory And Methods: The variances of normal noise and aliasing artifacts in the collected signal are related to the variances in T and T maps through derived quality factors. This analytical result is tested against the results of a Monte-Carlo approach for analyzing MRF sequence encoding capability in the presence of aliasing noise, and verified with phantom experiments at 3 T. To further show the utility of our approach, our quality factors are used to find efficient MRF sequences for fewer repetitions.

Results: Experimental results verify the ability of our quality factors to rapidly assess the efficiency of an MRF sequence in the presence of both normal and aliasing noise. Quality factor assessment of MRF sequences is in agreement with the results of a Monte-Carlo approach. Analysis of MRF parameter map errors from phantom experiments is consistent with the derived quality factors, with T (T ) data yielding goodness of fit R ≥ 0.92 (0.80). In phantom and in vivo experiments, the efficient pulse sequence, determined through quality factor maximization, led to comparable or improved accuracy and precision relative to a longer sequence, demonstrating quality factor utility in MRF sequence design.

Conclusion: The here introduced quality factor framework allows for rapid analysis and optimization of MRF sequence design through T and T error forecasting.
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http://dx.doi.org/10.1002/mrm.27638DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6414267PMC
May 2019

Simultaneous multislice cardiac magnetic resonance fingerprinting using low rank reconstruction.

NMR Biomed 2019 02 18;32(2):e4041. Epub 2018 Dec 18.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.

This study introduces a technique for simultaneous multislice (SMS) cardiac magnetic resonance fingerprinting (cMRF), which improves the slice coverage when quantifying myocardial T T , and M . The single-slice cMRF pulse sequence was modified to use multiband (MB) RF pulses for SMS imaging. Different RF phase schedules were used to excite each slice, similar to POMP or CAIPIRINHA, which imparts tissues with a distinguishable and slice-specific magnetization evolution over time. Because of the high net acceleration factor (R = 48 in plane combined with the slice acceleration), images were first reconstructed with a low rank technique before matching data to a dictionary of signal timecourses generated by a Bloch equation simulation. The proposed method was tested in simulations with a numerical relaxation phantom. Phantom and in vivo cardiac scans of 10 healthy volunteers were also performed at 3 T. With single-slice acquisitions, the mean relaxation times obtained using the low rank cMRF reconstruction agree with reference values. The low rank method improves the precision in T and T for both single-slice and SMS cMRF, and it enables the acquisition of maps with fewer artifacts when using SMS cMRF at higher MB factors. With this technique, in vivo cardiac maps were acquired from three slices simultaneously during a breathhold lasting 16 heartbeats. SMS cMRF improves the efficiency and slice coverage of myocardial T and T mapping compared with both single-slice cMRF and conventional cardiac mapping sequences. Thus, this technique is a first step toward whole-heart simultaneous T and T quantification with cMRF.
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http://dx.doi.org/10.1002/nbm.4041DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755311PMC
February 2019

Cardiac Magnetic Resonance Fingerprinting: Technical Overview and Initial Results.

JACC Cardiovasc Imaging 2018 12;11(12):1837-1853

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio; Department of Cardiovascular Medicine, University Hospitals, Harrington Heart and Vascular Institute, Cleveland Medical Center and Case Western Reserve School of Medicine, Cleveland, Ohio; Department of Radiology, Case Western Reserve University, Cleveland, Ohio. Electronic address:

Cardiovascular magnetic resonance is a versatile tool that enables noninvasive characterization of cardiac tissue structure and function. Parametric mapping techniques have allowed unparalleled differentiation of pathophysiological differences in the myocardium such as the delineation of myocardial fibrosis, hemorrhage, and edema. These methods are increasingly used as part of a tool kit to characterize disease states such as cardiomyopathies and coronary artery disease more accurately. Currently conventional mapping techniques require separate acquisitions for T and T mapping, the values of which may depend on specifics of the magnetic resonance imaging system hardware, pulse sequence implementation, and physiological variables including blood pressure and heart rate. The cardiac magnetic resonance fingerprinting (cMRF) technique has recently been introduced for simultaneous and reproducible measurement of T and T maps in a single scan. The potential for this technique to provide consistent tissue property values independent of variables including scanner, pulse sequence, and physiology could allow an unbiased framework for the assessment of intrinsic properties of cardiac tissue including structure, perfusion, and parameters such as extracellular volume without the administration of exogenous contrast agents. This review seeks to introduce the basics of the cMRF technique, including pulse sequence design, dictionary generation, and pattern matching. The potential applications of cMRF in assessing diseases such as nonischemic cardiomyopathy are also briefly discussed, and ongoing areas of research are described.
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http://dx.doi.org/10.1016/j.jcmg.2018.08.028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6394856PMC
December 2018

Magnetic resonance fingerprinting with quadratic RF phase for measurement of T simultaneously with δ , T , and T.

Magn Reson Med 2019 03 30;81(3):1849-1862. Epub 2018 Oct 30.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio.

Purpose: This study explores the possibility of using a gradient moment balanced sequence with a quadratically varied RF excitation phase in the magnetic resonance fingerprinting (MRF) framework to quantify T in addition to , T , and T tissue properties.

Methods: The proposed quadratic RF phase-based MRF method (qRF-MRF) combined a varied RF excitation phase with the existing balanced SSFP (bSSFP)-based MRF method to generate signals that were uniquely sensitive to , T , T , as well as the distribution width of intravoxel frequency dispersion, . A dictionary, generated through Bloch simulation, containing possible signal evolutions within the physiological range of , T , T , and , was used to perform parameter estimation. The estimated T and were subsequently used to estimate T . The proposed method was evaluated in phantom experiments and healthy volunteers (N = 5).

Results: The T and T values from the phantom by qRF-MRF demonstrated good agreement with values obtained by traditional gold standard methods (r = 0.995 and 0.997, respectively; concordance correlation coefficient = 0.978 and 0.995, respectively). The T values from the phantom demonstrated good agreement with values obtained through the multi-echo gradient-echo method (r = 0.972, concordance correlation coefficient = 0.983). In vivo qRF-MRF-measured T , T , and T values were compared with measurements by existing methods and literature values.

Conclusion: The proposed qRF-MRF method demonstrated the potential for simultaneous quantification of , T , T , and T tissue properties.
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http://dx.doi.org/10.1002/mrm.27543DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7325599PMC
March 2019

Realistic 4D MRI abdominal phantom for the evaluation and comparison of acquisition and reconstruction techniques.

Magn Reson Med 2019 03 5;81(3):1863-1875. Epub 2018 Nov 5.

Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio.

Purpose: This work presents a 4D numerical abdominal phantom, which includes T and T relaxation times, proton density fat fraction, perfusion, and diffusion, as well as respiratory motion for the evaluation and comparison of acquisition and reconstruction techniques.

Methods: The 3D anatomical mesh models were non-rigidly scaled and shifted by respiratory motion derived from an in vivo scan. A time series of voxelized 3D abdominal phantom images were obtained with contrast determined by the tissue properties and pulse sequence parameters. Two example simulations: (1) 3D T mapping under breath-hold and free-breathing acquisition conditions and (2) two different reconstruction techniques for accelerated 3D dynamic contrast-enhanced MRI, are presented. The source codes can be found at https://github.com/SeiberlichLab/Abdominal_MR_Phantom.

Results: The proposed 4D abdominal phantom can successfully simulate images and MRI data with nonrigid respiratory motion and specific contrast settings and data sampling schemes. In example 1, the use of a numerical 4D abdominal phantom was demonstrated to aid in the comparison between different approaches for volumetric T mapping. In example 2, the average arterial fraction over the healthy hepatic parenchyma as calculated with spiral generalized autocalibrating partial parallel acquisition was closer to that from the fully sampled data than the arterial fraction from conjugate gradient sensitivity encoding, although both are elevated compared to the gold-standard reference.

Conclusion: This realistic abdominal MR phantom can be used to simulate different pulse sequences and data sampling schemes for the comparison of acquisition and reconstruction methods under controlled conditions that are impossible or prohibitively difficult to perform in vivo.
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http://dx.doi.org/10.1002/mrm.27545DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7728431PMC
March 2019

Three-dimensional MR Fingerprinting for Quantitative Breast Imaging.

Radiology 2019 01 30;290(1):33-40. Epub 2018 Oct 30.

From the Departments of Radiology (Y.C., A.P., S.P., S.D., D.F.M., D.M., J.B., N.S., M.A.G., D.P., V.G.) and Biomedical Engineering (J.I.H., N.S., M.A.G., V.G.), Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH 44106; and Department of Radiology, University Hospitals Cleveland Medical Center, Cleveland, Ohio (Y.C., A.P., S.P., S.D., D.F.M., D.M., J.B., M.A.G., D.P., V.G.).

Purpose To develop a fast three-dimensional method for simultaneous T1 and T2 quantification for breast imaging by using MR fingerprinting. Materials and Methods In this prospective study, variable flip angles and magnetization preparation modules were applied to acquire MR fingerprinting data for each partition of a three-dimensional data set. A fast postprocessing method was implemented by using singular value decomposition. The proposed technique was first validated in phantoms and then applied to 15 healthy female participants (mean age, 24.2 years ± 5.1 [standard deviation]; range, 18-35 years) and 14 female participants with breast cancer (mean age, 55.4 years ± 8.8; range, 39-66 years) between March 2016 and April 2018. The sensitivity of the method to B field inhomogeneity was also evaluated by using the Bloch-Siegert method. Results Phantom results showed that accurate and volumetric T1 and T2 quantification was achieved by using the proposed technique. The acquisition time for three-dimensional quantitative maps with a spatial resolution of 1.6 × 1.6 × 3 mm was approximately 6 minutes. For healthy participants, averaged T1 and T2 relaxation times for fibroglandular tissues at 3.0 T were 1256 msec ± 171 and 46 msec ± 7, respectively. Compared with normal breast tissues, higher T2 relaxation time (68 msec ± 13) was observed in invasive ductal carcinoma (P < .001), whereas no statistical difference was found in T1 relaxation time (1183 msec ± 256; P = .37). Conclusion A method was developed for breast imaging by using the MR fingerprinting technique, which allows simultaneous and volumetric quantification of T1 and T2 relaxation times for breast tissues. © RSNA, 2018 Online supplemental material is available for this article.
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http://dx.doi.org/10.1148/radiol.2018180836DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312432PMC
January 2019

Magnetic resonance fingerprinting: a technical review.

Magn Reson Med 2019 01 14;81(1):25-46. Epub 2018 Sep 14.

Department of Radiology, Case Western Reserve Universityand University Hospitals Cleveland Medical Center, Cleveland, Ohio.

Multiparametric quantitative imaging is gaining increasing interest due to its widespread advantages in clinical applications. Magnetic resonance fingerprinting is a recently introduced approach of fast multiparametric quantitative imaging. In this article, magnetic resonance fingerprinting acquisition, dictionary generation, reconstruction, and validation are reviewed.
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http://dx.doi.org/10.1002/mrm.27403DOI Listing
January 2019

a-f BLAST: Non-Iterative Radial k-t BLAST Reconstruction for Real-Time Imaging.

IEEE Trans Med Imaging 2019 03 27;38(3):775-790. Epub 2018 Sep 27.

Non-Cartesian trajectories are advantageous in the collection and reconstruction of dynamic MR images. Like many other fast imaging methods, the reconstruction technique k-t broad-use linear acquisition speed-up technique (BLAST) has been extended to non-Cartesian k-t BLAST through a conjugate gradient-based approach. However, it is necessary to transform and grid the data to a Cartesian domain as part of the reconstruction, a process which can be time consuming and computationally intensive. In this paper, a new non-iterative reconstruction, a-f BLAST, is proposed to extend k-t BLAST to radial sampling. The a-f BLAST reconstruction is performed in a previously unexplored domain termed the angular frequency-temporal frequency (a-f) space and uses similar steps to Cartesian k-t BLAST. The performance of this method was demonstrated on retrospectively undersampled numerical phantoms and compared with k-t BLAST, non-Cartesian k-t BLAST, and the sliding window technique. In addition, the reconstruction was tested on retrospectively and prospectively undersampled in vivo cardiac data. The a-f BLAST is shown to have a similar reconstruction time as k-t BLAST as well as outperform k-t BLAST in terms of root-mean-square error.
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http://dx.doi.org/10.1109/TMI.2018.2872419DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469684PMC
March 2019

Investigating and reducing the effects of confounding factors for robust T and T mapping with cardiac MR fingerprinting.

Magn Reson Imaging 2018 11 30;53:40-51. Epub 2018 Jun 30.

Dept. of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA; Dept. of Radiology, University Hospitals Cleveland Medical Center, Cleveland, OH, USA. Electronic address:

This study aims to improve the accuracy and consistency of T and T measurements using cardiac MR Fingerprinting (cMRF) by investigating and accounting for the effects of confounding factors including slice profile, inversion and T preparation pulse efficiency, and B. The goal is to understand how measurements with different pulse sequences are affected by these factors. This can be used to determine which factors must be taken into account for accurate measurements, and which may be mitigated by the selection of an appropriate pulse sequence. Simulations were performed using a numerical cardiac phantom to assess the accuracy of over 600 cMRF sequences with different flip angles, TRs, and preparation pulses. A subset of sequences, including one with the lowest errors in T and T maps, was used in subsequent analyses. Errors due to non-ideal slice profile, preparation pulse efficiency, and B were quantified in Bloch simulations. Corrections for these effects were included in the dictionary generation and demonstrated in phantom and in vivo cardiac imaging at 3 T. Neglecting to model slice profile and preparation pulse efficiency led to underestimated T and overestimated T for most cMRF sequences. Sequences with smaller maximum flip angles were less affected by slice profile and B. Simulating all corrections in the dictionary improved the accuracy of T and T phantom measurements, regardless of acquisition pattern. More consistent myocardial T and T values were measured using different sequences after corrections. Based on these results, a pulse sequence which is minimally affected by confounding factors can be selected, and the appropriate residual corrections included for robust T and T mapping.
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http://dx.doi.org/10.1016/j.mri.2018.06.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7755105PMC
November 2018

Magnetic Resonance Fingerprinting-An Overview.

Curr Opin Biomed Eng 2017 Sep;3:56-66

Department of Radiology, Case Western Reserve University, University Hospitals Cleveland Medical Center, Cleveland, Ohio, USA.

Magnetic Resonance Fingerprinting (MRF) is a new approach to quantitative magnetic resonance imaging that allows simultaneous measurement of multiple tissue properties in a single, time-efficient acquisition. The ability to reproducibly and quantitatively measure tissue properties could enable more objective tissue diagnosis, comparisons of scans acquired at different locations and time points, longitudinal follow-up of individual patients and development of imaging biomarkers. This review provides a general overview of MRF technology, current preclinical and clinical applications and potential future directions. MRF has been initially evaluated in brain, prostate, liver, cardiac, musculoskeletal imaging, and measurement of perfusion and microvascular properties through MR vascular fingerprinting.
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http://dx.doi.org/10.1016/j.cobme.2017.11.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5984038PMC
September 2017

Single breath-hold 3D cardiac T mapping using through-time spiral GRAPPA.

NMR Biomed 2018 06 10;31(6):e3923. Epub 2018 Apr 10.

Department of Radiology, Case Western Reserve University, Cleveland, OH, USA.

The quantification of cardiac T relaxation time holds great potential for the detection of various cardiac diseases. However, as a result of both cardiac and respiratory motion, only one two-dimensional T map can be acquired in one breath-hold with most current techniques, which limits its application for whole heart evaluation in routine clinical practice. In this study, an electrocardiogram (ECG)-triggered three-dimensional Look-Locker method was developed for cardiac T measurement. Fast three-dimensional data acquisition was achieved with a spoiled gradient-echo sequence in combination with a stack-of-spirals trajectory and through-time non-Cartesian generalized autocalibrating partially parallel acquisition (GRAPPA) acceleration. The effects of different magnetic resonance parameters on T quantification with the proposed technique were first examined by simulating data acquisition and T map reconstruction using Bloch equation simulations. Accuracy was evaluated in studies with both phantoms and healthy subjects. These results showed that there was close agreement between the proposed technique and the reference method for a large range of T values in phantom experiments. In vivo studies further demonstrated that rapid cardiac T mapping for 12 three-dimensional partitions (spatial resolution, 2 × 2 × 8 mm ) could be achieved in a single breath-hold of ~12 s. The mean T values of myocardial tissue and blood obtained from normal volunteers at 3 T were 1311 ± 66 and 1890 ± 159 ms, respectively. In conclusion, a three-dimensional T mapping technique was developed using a non-Cartesian parallel imaging method, which enables fast and accurate T mapping of cardiac tissues in a single short breath-hold.
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http://dx.doi.org/10.1002/nbm.3923DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5980781PMC
June 2018

Quantitative perfusion imaging of neoplastic liver lesions: A multi-institution study.

Sci Rep 2018 03 21;8(1):4990. Epub 2018 Mar 21.

Radiology, Case Western Reserve University, Cleveland, OH, United States.

We describe multi-institutional experience using free-breathing, 3D Spiral GRAPPA-based quantitative perfusion MRI in characterizing neoplastic liver masses. 45 patients (age: 48-72 years) were prospectively recruited at University Hospitals, Cleveland, USA on a 3 Tesla (T) MRI, and at Zhongshan Hospital, Shanghai, China on a 1.5 T MRI. Contrast-enhanced volumetric T1-weighted images were acquired and a dual-input single-compartment model used to derive arterial fraction (AF), distribution volume (DV) and mean transit time (MTT) for the lesions and normal parenchyma. The measurements were compared using two-tailed Student's t-test, with Bonferroni correction applied for multiple-comparison testing. 28 hepatocellular carcinoma (HCC) and 17 metastatic lesions were evaluated. No significant difference was noted in perfusion parameters of normal liver parenchyma and neoplastic masses at two centers (p = 0.62 for AF, 0.015 for DV, 0.42 for MTT for HCC, p = 0.13 for AF, 0.97 for DV, 0.78 for MTT for metastases). There was statistically significant difference in AF, DV, and MTT of metastases and AF and DV of HCC compared to normal liver parenchyma (p < 0.5/9 = 0.0055). A statistically significant difference was noted in the MTT of metastases compared to hepatocellular carcinoma (p < 0.001*10-5). In conclusion, 3D Spiral-GRAPPA enabled quantitative free-breathing perfusion MRI exam provides robust perfusion parameters.
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http://dx.doi.org/10.1038/s41598-018-20726-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5862961PMC
March 2018

Iterative Jacobian-Based Inverse Kinematics and Open-Loop Control of an MRI-Guided Magnetically Actuated Steerable Catheter System.

IEEE ASME Trans Mechatron 2017 Aug 16;22(4):1765-1776. Epub 2017 May 16.

Case Western Reserve University, Cleveland, Ohio 44106, USA. Department of Electrical Engineering and Computer Science.

This paper presents an iterative Jacobian-based inverse kinematics method for an MRI-guided magnetically-actuated steerable intravascular catheter system. The catheter is directly actuated by magnetic torques generated on a set of current-carrying micro-coils embedded on the catheter tip, by the magnetic field of the magnetic resonance imaging (MRI) scanner. The Jacobian matrix relating changes of the currents through the coils to changes of the tip position is derived using a three dimensional kinematic model of the catheter deflection. The inverse kinematics is numerically computed by iteratively applying the inverse of the Jacobian matrix. The damped least square method is implemented to avoid numerical instability issues that exist during the computation of the inverse of the Jacobian matrix. The performance of the proposed inverse kinematics approach is validated using a prototype of the robotic catheter by comparing the actual trajectories of the catheter tip obtained via open-loop control with the desired trajectories. The results of reproducibility and accuracy evaluations demonstrate that the proposed Jacobian-based inverse kinematics method can be used to actuate the catheter in open-loop to successfully perform complex ablation trajectories required in atrial fibrillation ablation procedures. This study paves the way for effective and accurate closed-loop control of the robotic catheter with real-time feedback from MRI guidance in subsequent research.
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http://dx.doi.org/10.1109/TMECH.2017.2704526DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5731790PMC
August 2017
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