Publications by authors named "Mark A Griswold"

122 Publications

Automated design of pulse sequences for magnetic resonance fingerprinting using physics-inspired optimization.

Proc Natl Acad Sci U S A 2021 10 30;118(40). Epub 2021 Sep 30.

Biomedical Engineering, Case Western Reserve University, Cleveland, OH 44106;

Magnetic resonance fingerprinting (MRF) is a method to extract quantitative tissue properties such as [Formula: see text] and [Formula: see text] relaxation rates from arbitrary pulse sequences using conventional MRI hardware. MRF pulse sequences have thousands of tunable parameters, which can be chosen to maximize precision and minimize scan time. Here, we perform de novo automated design of MRF pulse sequences by applying physics-inspired optimization heuristics. Our experimental data suggest that systematic errors dominate over random errors in MRF scans under clinically relevant conditions of high undersampling. Thus, in contrast to prior optimization efforts, which focused on statistical error models, we use a cost function based on explicit first-principles simulation of systematic errors arising from Fourier undersampling and phase variation. The resulting pulse sequences display features qualitatively different from previously used MRF pulse sequences and achieve fourfold shorter scan time than prior human-designed sequences of equivalent precision in [Formula: see text] and [Formula: see text] Furthermore, the optimization algorithm has discovered the existence of MRF pulse sequences with intrinsic robustness against shading artifacts due to phase variation.
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http://dx.doi.org/10.1073/pnas.2020516118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8501900PMC
October 2021

Feasibility of MR fingerprinting using a high-performance 0.55 T MRI system.

Magn Reson Imaging 2021 09 8;81:88-93. Epub 2021 Jun 8.

Department of Radiology, Case Western Reserve University, Cleveland, OH, United States of America. Electronic address:

Background: MR fingerprinting (MRF) is a versatile method for rapid multi-parametric quantification. The application of MRF for lower MRI field could enable multi-contrast imaging and improve exam efficiency on these systems. The purpose of this work is to demonstrate the feasibility of 3D whole-brain T1 and T2 mapping using MR fingerprinting on a contemporary 0.55 T MRI system.

Materials And Methods: A 3D whole brain stack-of-spirals FISP MRF sequence was implemented for 0.55 T. Quantification was validated using the NIST/ISMRM Quantitative MRI phantom, and T1 and T2 values of white matter, gray matter, and cerebrospinal fluid were measured in 19 healthy subjects. To assess MRF performance in the lower SNR regime of 0.55 T, measurement precision was calculated from 100 simulated pseudo-replicas of in vivo data and within-session measurement repeatability was evaluated.

Results: T1 and T2 values calculated by MRF were strongly correlated to standard measurements in the ISMRM/NIST MRI system phantom (R > 0.99), with a small constant bias of approximately 5 ms in T2 values. 3D stack-of-spirals MRF was successfully applied for whole brain quantitative T1 and T2 at 0.55 T, with spatial resolution of 1.2 mm × 1.2 mm × 5 mm, and acquisition time of 8.5 min. Moreover, the T1 and T2 quantifications had precision <5%, despite the lower SNR of 0.55 T.

Conclusion: A 3D whole-brain stack-of-spirals FISP MRF sequence is feasible for T1 and T2 mapping at 0.55 T.
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http://dx.doi.org/10.1016/j.mri.2021.06.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8749356PMC
September 2021

Rapid B-Insensitive MR Fingerprinting for Quantitative Kidney Imaging.

Radiology 2021 08 8;300(2):380-387. Epub 2021 Jun 8.

From the Departments of Radiology (C.J.M., S.F., J.R.P., N.P., M.A.G., D.M., C.A.F., Y.C.), Genetics and Genome Sciences (M.L.D.), Pediatrics (M.L.D., K.M.D., C.A.F.), and Biomedical Engineering (M.A.G., D.M., C.A.F.), Case Western Reserve University, 11100 Euclid Ave, Bowell Building, Room B131, Cleveland, OH 44106; Departments of Radiology (M.M.) and Pediatrics (K.M., K.K.), University Hospitals Cleveland Medical Center, Cleveland, Ohio; and Center for Pediatric Nephrology, Cleveland Clinic Children's Hospital, Cleveland, Ohio (A.P., K.M.D.).

Background MR fingerprinting (MRF) provides rapid and simultaneous quantification of multiple tissue parameters in a single scan. Purpose To evaluate a rapid kidney MRF technique at 3.0 T in phantoms, healthy volunteers, and patients. Materials and Methods A 15-second kidney MRF acquisition was designed with 12 acquisition segments, a range of low flip angles (5°-12°), multiple magnetization preparation schema (T1, T2, and fat suppression), and an undersampled spiral trajectory. This technique was first validated in vitro using standardized T1 and T2 phantoms. Kidney T1 and T2 maps were then obtained for 10 healthy adult volunteers (mean age ± standard deviation, 35 years ± 13; six men) and three pediatric patients with autosomal recessive polycystic kidney disease (ARPKD) (mean age, 10 years ± 3; two boys) between August 2019 and October 2020 to evaluate the method in vivo. Results Results in nine phantoms showed good agreement with spin-echo-based T1 and T2 values ( > 0.99). In vivo MRF kidney T1 and T2 assessments in healthy adult volunteers (cortex: T1, 1362 msec ± 5; T2, 64 msec ± 5; medulla: T1, 1827 msec ± 94; T2, 69 msec ± 3) were consistent with values in the literature but with improved precision in comparison with prior MRF implementations. In vivo MRF-based kidney T1 and T2 values with and without B correction were in good agreement ( > 0.96, < .001), demonstrating limited sensitivity to B field inhomogeneities. Additional MRF reconstructions using the first nine segments of the MRF profiles (11-second acquisition time) were in good agreement with the reconstructions using 12 segments (15-second acquisition time) ( > 0.87, < .001). Repeat kidney MRF scans for the three patients with ARPKD on successive days also demonstrated good reproducibility (T1 and T2: <3% difference). Conclusion A kidney MR fingerprinting method provided in vivo kidney T1 and T2 maps at 3.0 T in a single breath hold with improved precision and no need for B correction. © RSNA, 2021 See also the editorial by Laustsen in this issue.
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http://dx.doi.org/10.1148/radiol.2021202302DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8328087PMC
August 2021

Free-Breathing Abdominal Magnetic Resonance Fingerprinting Using a Pilot Tone Navigator.

J Magn Reson Imaging 2021 10 5;54(4):1138-1151. Epub 2021 May 5.

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

Background: Quantitative T1 and T2 mapping in the abdomen provides valuable information in tissue characterization but is technically challenging due to respiratory motions. The proposed technique integrates magnetic resonance fingerprinting (MRF) and pilot tone (PT) navigator with retrospective gating to provide simultaneous quantification of multiple tissue properties in a single acquisition without breath-holding or patient set-up.

Purpose: To develop a free-breathing abdominal MRF technique for quantitative mapping in the abdomen.

Study Type: Prospective.

Population: Twelve healthy volunteers.

Field Strength/sequence: A 3 T, two-dimensional (2D) and three-dimensional (3D) spiral MRF sequence with fast imaging with steady-state free precession (FISP) readout.

Assessment: The PT navigator was compared to standard respiratory belt performance. The T1 and T2 values acquired using 2D and 3D MRF with and without PT were obtained in a phantom and compared to reference values. Digital phantom simulation was performed to evaluate PT MRF reconstruction with varying breathing patterns. In the in vivo studies, T1 and T2 values derived from PT 2D MRF were compared to 2D breath-hold MRF. T1 and T2 values derived from PT 3D MRF were compared to published values.

Statistical Tests: Principal component analysis (PCA), linear regression, relative error, Pearson correlation, paired Student's t-test, Bland-Altman Analysis.

Results: The phantom study showed PT MRF T1 values had a mean difference of 0.2% ± 0.1%, and T2 values had a mean difference of 0.1% ± 0.4% when compared to no-PT MRF values. The digital phantom experiment suggested the T1 and T2 maps at both end-exhalation and end-inhalation states resemble the corresponding ground-truth maps.

Data Conclusion: The phantom study showed good agreement between MRF T1 and T2 values and with reference values. In vivo studies demonstrated that 2D and 3D quantitative imaging in the abdomen could be achieved with integration of PT navigation with MRF reconstruction using retrospective gating of respiratory motion. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 1.
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http://dx.doi.org/10.1002/jmri.27673DOI Listing
October 2021

3D magnetic resonance fingerprinting with quadratic RF phase.

Magn Reson Med 2021 04 12;85(4):2084-2094. Epub 2020 Nov 12.

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

Purpose: To implement 3D magnetic resonance fingerprinting (MRF) with quadratic RF phase (qRF-MRF) for simultaneous quantification of T , T , ΔB , and .

Methods: 3D MRF data with effective undersampling factor of 3 in the slice direction were acquired with quadratic RF phase patterns for T , T , and sensitivity. Quadratic RF phase encodes the off-resonance by modulating the on-resonance frequency linearly in time. Transition to 3D brings practical limitations for reconstruction and dictionary matching because of increased data and dictionary sizes. Randomized singular value decomposition (rSVD)-based compression in time and reduction in dictionary size with a quadratic interpolation method are combined to be able to process prohibitively large data sets in feasible reconstruction and matching times.

Results: Accuracy of 3D qRF-MRF maps in various resolutions and orientations are compared to 3D fast imaging with steady-state precession (FISP) for T and T contrast and to 2D qRF-MRF for contrast and ΔB . The precision of 3D qRF-MRF was 1.5-2 times higher than routine clinical scans. 3D qRF-MRF ΔB maps were further processed to highlight the susceptibility contrast.

Conclusion: Natively co-registered 3D whole brain T , T , , ΔB , and QSM maps can be acquired in as short as 5 min with 3D qRF-MRF.
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http://dx.doi.org/10.1002/mrm.28581DOI Listing
April 2021

Assessment of Mixed-Reality Technology Use in Remote Online Anatomy Education.

JAMA Netw Open 2020 09 1;3(9):e2016271. Epub 2020 Sep 1.

School of Medicine, Case Western Reserve University, Cleveland, Ohio.

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http://dx.doi.org/10.1001/jamanetworkopen.2020.16271DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499123PMC
September 2020

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

Mixed reality as a time-efficient alternative to cadaveric dissection.

Med Teach 2020 08 13;42(8):896-901. Epub 2020 May 13.

Interactive Commons, Case Western Reserve University, Cleveland, OH, USA.

: The extent of medical knowledge increases yearly, but the time available for students to learn is limited, leading to administrative pressures to revise and reconfigure medical school curricula. The goal of the present study is to determine whether the mixed reality platform HoloAnatomy represents an effective and time-efficient modality to learn anatomy when compared to traditional cadaveric dissection. This was a prospective, longitudinal study of medical students completing a musculoskeletal anatomy course at Case Western Reserve University School of Medicine. Participants were divided into two groups based on learning platform (HoloAnatomy versus traditional cadaveric dissection) and content area (upper limb versus lower limb anatomy). Time spent in lab and end of course practical exam scores were compared between groups. The average study time of 48 medical students who completed study requirements was 4.564 h using HoloAnatomy and 7.318 h in the cadaver lab ( = 0.001). No significant difference was found between exam scores for HoloAnatomy and cadaver learners ( = 0.185). Our results indicate that HoloAnatomy may decrease the time necessary for anatomy didactics without sacrificing student understanding of the material.
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http://dx.doi.org/10.1080/0142159X.2020.1762032DOI Listing
August 2020

Dynamic, Simultaneous Concentration Mapping of Multiple MRI Contrast Agents with Dual Contrast - Magnetic Resonance Fingerprinting.

Sci Rep 2019 12 27;9(1):19888. Epub 2019 Dec 27.

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

Synchronous assessment of multiple MRI contrast agents in a single scanning session would provide a new "multi-color" imaging capability similar to fluorescence imaging but with high spatiotemporal resolution and unlimited imaging depth. This multi-agent MRI technology would enable a whole new class of basic science and clinical MRI experiments that simultaneously explore multiple physiologic/molecular events in vivo. Unfortunately, conventional MRI acquisition techniques are only capable of detecting and quantifying one paramagnetic MRI contrast agent at a time. Herein, the Dual Contrast - Magnetic Resonance Fingerprinting (DC-MRF) methodology was extended for in vivo application and evaluated by simultaneously and dynamically mapping the intra-tumoral concentration of two MRI contrast agents (Gd-BOPTA and Dy-DOTA-azide) in a mouse glioma model. Co-registered gadolinium and dysprosium concentration maps were generated with sub-millimeter spatial resolution and acquired dynamically with just over 2-minute temporal resolution. Mean tumor Gd and Dy concentration measurements from both single agent and dual agent DC-MRF studies demonstrated significant correlations with ex vivo mass spectrometry elemental analyses. This initial in vivo study demonstrates the potential for DC-MRF to provide a useful dual-agent MRI platform.
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http://dx.doi.org/10.1038/s41598-019-56531-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6934650PMC
December 2019

Holographic Reconstruction of Axonal Pathways in the Human Brain.

Neuron 2019 12 7;104(6):1056-1064.e3. Epub 2019 Nov 7.

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

Three-dimensional documentation of the axonal pathways connecting gray matter components of the human brain has wide-ranging scientific and clinical applications. Recent attempts to map human structural connectomes have concentrated on using tractography results derived from diffusion-weighted imaging data, but tractography is an indirect method with numerous limitations. Advances in holographic visualization platforms provide a new medium to integrate anatomical data, as well as a novel working environment for collaborative interaction between neuroanatomists and brain-imaging scientists. Therefore, we developed the first holographic interface for building axonal pathways, populated it with human histological and structural MRI data, and assembled world expert neuroanatomists to interactively define axonal trajectories of the cortical, basal ganglia, and cerebellar systems. This blending of advanced visualization hardware, software development, and neuroanatomy data enabled the translation of decades of amassed knowledge into a human axonal pathway atlas that can be applied to educational, scientific, or clinical investigations.
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http://dx.doi.org/10.1016/j.neuron.2019.09.030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6948195PMC
December 2019

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

MR Fingerprinting and ADC Mapping for Characterization of Lesions in the Transition Zone of the Prostate Gland.

Radiology 2019 09 23;292(3):685-694. Epub 2019 Jul 23.

From the Department of Radiology, Mayo Clinic, Rochester, Minn (A.P.); Department of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland (V.C.O.); Departments of Biomedical Engineering (W.C.L., M.A.G.), Epidemiology and Biostatistics (S.M., M.S.), and Radiology (Y.J., C.B., M.A.G., V.G.), Case Western Reserve University, Cleveland, Ohio; Department of Radiology, University of Michigan, UH B1 G503, 1500 E. Medical Center Drive, SPC 5030, Ann Arbor, MI 48109-5030 (Y.J., V.G.); Department of Radiology, Mayo Clinic, Phoenix, Az (I.J.P.); Departments of Radiology (I.J.P., D.N., C.B., M.A.G.) and Urology (I.J., L.E.P.), University Hospitals Cleveland Medical Center, Cleveland, Ohio.

BackgroundPreliminary studies have shown that MR fingerprinting-based relaxometry combined with apparent diffusion coefficient (ADC) mapping can be used to differentiate normal peripheral zone from prostate cancer and prostatitis. The utility of relaxometry and ADC mapping for the transition zone (TZ) is unknown.PurposeTo evaluate the utility of MR fingerprinting combined with ADC mapping for characterizing TZ lesions.Materials and MethodsTZ lesions that were suspicious for cancer in men who underwent MRI with T2-weighted imaging and ADC mapping ( values, 50-1400 sec/mm), MR fingerprinting with steady-state free precession, and targeted biopsy (60 in-gantry and 15 cognitive targeting) between September 2014 and August 2018 in a single university hospital were retrospectively analyzed. Two radiologists blinded to Prostate Imaging Reporting and Data System (PI-RADS) scores and pathologic diagnosis drew regions of interest on cancer-suspicious lesions and contralateral visually normal TZs (NTZs) on MR fingerprinting and ADC maps. Linear mixed models compared two-reader means of T1, T2, and ADC. Generalized estimating equations logistic regression analysis was used to evaluate both MR fingerprinting and ADC in differentiating NTZ, cancers and noncancers, clinically significant (Gleason score ≥ 7) cancers from clinically insignificant lesions (noncancers and Gleason 6 cancers), and characterizing PI-RADS version 2 category 3 lesions.ResultsIn 67 men (mean age, 66 years ± 8 [standard deviation]) with 75 lesions, targeted biopsy revealed 37 cancers (six PI-RADS category 3 cancers and 31 PI-RADS category 4 or 5 cancers) and 38 noncancers (31 PI-RADS category 3 lesions and seven PI-RADS category 4 or 5 lesions). The T1, T2, and ADC of NTZ (1800 msec ± 150, 65 msec ± 22, and [1.13 ± 0.19] × 10 mm/sec, respectively) were higher than those in cancers (1450 msec ± 110, 36 msec ± 11, and [0.57 ± 0.13] × 10 mm/sec, respectively; < .001 for all). The T1, T2, and ADC in cancers were lower than those in noncancers (1620 msec ± 120, 47 msec ± 16, and [0.82 ± 0.13] × 10 mm/sec, respectively; = .001 for T1 and ADC and = .03 for T2). The area under the receiver operating characteristic curve (AUC) for T1 plus ADC was 0.94 for separation. T1 and ADC in clinically significant cancers (1440 msec ± 140 and [0.58 ± 0.14] × 10 mm/sec, respectively) were lower than those in clinically insignificant lesions (1580 msec ± 120 and [0.75 ± 0.17] × 10 mm/sec, respectively; = .001 for all). The AUC for T1 plus ADC was 0.81 for separation. Within PI-RADS category 3 lesions, T1 and ADC of cancers (1430 msec ± 220 and [0.60 ± 0.17] × 10 mm/sec, respectively) were lower than those of noncancers (1630 msec ± 120 and [0.81 ± 0.13] × 10 mm/sec, respectively; = .006 for T1 and = .004 for ADC). The AUC for T1 was 0.79 for differentiating category 3 lesions.ConclusionMR fingerprinting-based relaxometry combined with apparent diffusion coefficient mapping may improve transition zone lesion characterization.© RSNA, 2019
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http://dx.doi.org/10.1148/radiol.2019181705DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6716564PMC
September 2019

Magnetic resonance fingerprinting Part 1: Potential uses, current challenges, and recommendations.

J Magn Reson Imaging 2020 03 2;51(3):675-692. Epub 2019 Jul 2.

Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado, USA.

Magnetic resonance fingerprinting (MRF) is a powerful quantitative MRI technique capable of acquiring multiple property maps simultaneously in a short timeframe. The MRF framework has been adapted to a wide variety of clinical applications, but faces challenges in technical development, and to date has only demonstrated repeatability and reproducibility in small studies. In this review, we discuss the current implementations of MRF and their use in a clinical setting. Based on this analysis, we highlight areas of need that must be addressed before MRF can be fully adopted into the clinic and make recommendations to the MRF community on standardization and validation strategies of MRF techniques. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:675-692.
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http://dx.doi.org/10.1002/jmri.26836DOI Listing
March 2020

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

Development of high-resolution 3D MR fingerprinting for detection and characterization of epileptic lesions.

J Magn Reson Imaging 2019 05 23;49(5):1333-1346. Epub 2018 Dec 23.

Epilepsy Center, Cleveland Clinic, Cleveland, Ohio, USA.

Background: Conventional MRI can be limited in detecting subtle epileptic lesions or identifying active/epileptic lesions among widespread, multifocal lesions.

Purpose: We developed a high-resolution 3D MR fingerprinting (MRF) protocol to simultaneously provide quantitative T , T , proton density, and tissue fraction maps for detection and characterization of epileptic lesions.

Study Type: Prospective.

Population: National Institute of Standards and Technology (NIST) / International Society for Magnetic Resonance in Medicine (ISMRM) phantom, five healthy volunteers and 15 patients with medically intractable epilepsy undergoing presurgical evaluation with noninvasive or invasive electroclinical data.

Field Strength/sequence: 3D MRF scans and routine clinical epilepsy MR protocols were acquired at 3 T.

Assessment: The accuracy of the T and T values were first evaluated using the NIST/ISMRM phantom. The repeatability was then estimated with both phantom and volunteers based on the coefficient of variance (CV). For epilepsy patients, all the maps were qualitatively reviewed for lesion detection by three independent reviewers (S.E.J., M.L., I.N.) blinded to clinical data. Region of interest (ROI) analysis was performed on T and T maps to quantify the multiparametric signal differences between lesion and normal tissues. Findings from qualitative review and quantitative ROI analysis were compared with patients' electroclinical data to assess concordance.

Statistical Tests: Phantom results were compared using R-squared, and patient results were compared using linear regression models.

Results: The phantom study showed high accuracy with the standard values, with an R of 0.99. The volunteer study showed high repeatability, with an average CV of 4.3% for T and T in various tissue regions. For the 15 patients, MRF showed additional findings in four patients, with the remaining 11 patients showing findings consistent with conventional MRI. The additional MRF findings were highly concordant with patients' electroclinical presentation.

Data Conclusion: The 3D MRF protocol showed potential to identify otherwise inconspicuous epileptogenic lesions from the patients with negative conventional MRI diagnosis, as well as to correlate with different levels of epileptogenicity when widespread lesions were present.

Level Of Evidence: 3. Technical Efficacy Stage: 3. J. Magn. Reson. Imaging 2019;49:1333-1346.
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http://dx.doi.org/10.1002/jmri.26319DOI Listing
May 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

Optimal Experiment Design for Magnetic Resonance Fingerprinting: Cramér-Rao Bound Meets Spin Dynamics.

IEEE Trans Med Imaging 2019 03 4;38(3):844-861. Epub 2018 Oct 4.

Magnetic resonance (MR) fingerprinting is a new quantitative imaging paradigm, which simultaneously acquires multiple MR tissue parameter maps in a single experiment. In this paper, we present an estimation-theoretic framework to perform experiment design for MR fingerprinting. Specifically, we describe a discrete-time dynamic system to model spin dynamics, and derive an estimation-theoretic bound, i.e., the Cramér-Rao bound, to characterize the signal-to-noise ratio (SNR) efficiency of an MR fingerprinting experiment. We then formulate an optimal experiment design problem, which determines a sequence of acquisition parameters to encode MR tissue parameters with the maximal SNR efficiency, while respecting the physical constraints and other constraints from the image decoding/reconstruction process. We evaluate the performance of the proposed approach with numerical simulations, phantom experiments, and in vivo experiments. We demonstrate that the optimized experiments substantially reduce data acquisition time and/or improve parameter estimation. For example, the optimized experiments achieve about a factor of two improvement in the accuracy of T maps, while keeping similar or slightly better accuracy of T maps. Finally, as a remarkable observation, we find that the sequence of optimized acquisition parameters appears to be highly structured rather than randomly/pseudo-randomly varying as is prescribed in the conventional MR fingerprinting experiments.
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http://dx.doi.org/10.1109/TMI.2018.2873704DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6447464PMC
March 2019

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

Fast magnetic resonance fingerprinting for dynamic contrast-enhanced studies in mice.

Magn Reson Med 2018 12 9;80(6):2681-2690. Epub 2018 May 9.

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

Purpose: The goal of this study was to develop a fast MR fingerprinting (MRF) method for simultaneous T and T mapping in DCE-MRI studies in mice.

Methods: The MRF sequences based on balanced SSFP and fast imaging with steady-state precession were implemented and evaluated on a 7T preclinical scanner. The readout used a zeroth-moment-compensated variable-density spiral trajectory that fully sampled the entire k-space and the inner 10 × 10 k-space with 48 and 4 interleaves, respectively. In vitro and in vivo studies of mouse brain were performed to evaluate the accuracy of MRF measurements with both fully sampled and undersampled data. The application of MRF to dynamic T and T mapping in DCE-MRI studies were demonstrated in a mouse model of heterotopic glioblastoma using gadolinium-based and dysprosium-based contrast agents.

Results: The T and T measurements in phantom showed strong agreement between the MRF and the conventional methods. The MRF with spiral encoding allowed up to 8-fold undersampling without loss of measurement accuracy. This enabled simultaneous T and T mapping with 2-minute temporal resolution in DCE-MRI studies.

Conclusion: Magnetic resonance fingerprinting provides the opportunity for dynamic quantification of contrast agent distribution in preclinical tumor models on high-field MRI scanners.
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http://dx.doi.org/10.1002/mrm.27345DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6226386PMC
December 2018

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

Estimation of perfusion properties with MR Fingerprinting Arterial Spin Labeling.

Magn Reson Imaging 2018 07 12;50:68-77. Epub 2018 Mar 12.

Dept. of Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.

In this study, the acquisition of ASL data and quantification of multiple hemodynamic parameters was explored using a Magnetic Resonance Fingerprinting (MRF) approach. A pseudo-continuous ASL labeling scheme was used with pseudo-randomized timings to acquire the MRF ASL data in a 2.5 min acquisition. A large dictionary of MRF ASL signals was generated by combining a wide range of physical and hemodynamic properties with the pseudo-random MRF ASL sequence and a two-compartment model. The acquired signals were matched to the dictionary to provide simultaneous quantification of cerebral blood flow, tissue time-to-peak, cerebral blood volume, arterial time-to-peak, B, and T A study in seven healthy volunteers resulted in the following values across the population in grey matter (mean ± standard deviation): cerebral blood flow of 69.1 ± 6.1 ml/min/100 g, arterial time-to-peak of 1.5 ± 0.1 s, tissue time-to-peak of 1.5 ± 0.1 s, T of 1634 ms, cerebral blood volume of 0.0048 ± 0.0005. The CBF measurements were compared to standard pCASL CBF estimates using a one-compartment model, and a Bland-Altman analysis showed good agreement with a minor bias. Repeatability was tested in five volunteers in the same exam session, and no statistical difference was seen. In addition to this validation, the MRF ASL acquisition's sensitivity to the physical and physiological parameters of interest was studied numerically.
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http://dx.doi.org/10.1016/j.mri.2018.03.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5970985PMC
July 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

Simultaneous multislice magnetic resonance fingerprinting with low-rank and subspace modeling.

Annu Int Conf IEEE Eng Med Biol Soc 2017 Jul;2017:3264-3268

Magnetic resonance fingerprinting (MRF) is a new quantitative imaging paradigm that enables simultaneous acquisition of multiple magnetic resonance tissue parameters (e.g., T, T, and spin density). Recently, MRF has been integrated with simultaneous multislice (SMS) acquisitions to enable volumetric imaging with faster scan time. In this paper, we present a new image reconstruction method based on low-rank and subspace modeling for improved SMS-MRF. Here the low-rank model exploits strong spatiotemporal correlation among contrast-weighted images, while the subspace model captures the temporal evolution of magnetization dynamics. With the proposed model, the image reconstruction problem is formulated as a convex optimization problem, for which we develop an algorithm based on variable splitting and the alternating direction method of multipliers. The performance of the proposed method has been evaluated by numerical experiments, and the results demonstrate that the proposed method leads to improved accuracy over the conventional approach. Practically, the proposed method has a potential to allow for a 3× speedup with minimal reconstruction error, resulting in less than 5 sec imaging time per slice.
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http://dx.doi.org/10.1109/EMBC.2017.8037553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5895455PMC
July 2017

P magnetic resonance fingerprinting for rapid quantification of creatine kinase reaction rate in vivo.

NMR Biomed 2017 Dec 15;30(12). Epub 2017 Sep 15.

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

The purpose of this work was to develop a P spectroscopic magnetic resonance fingerprinting (MRF) method for fast quantification of the chemical exchange rate between phosphocreatine (PCr) and adenosine triphosphate (ATP) via creatine kinase (CK). A P MRF sequence (CK-MRF) was developed to quantify the forward rate constant of ATP synthesis via CK ( kfCK), the T relaxation time of PCr ( T1PCr), and the PCr-to-ATP concentration ratio ( MRPCr). The CK-MRF sequence used a balanced steady-state free precession (bSSFP)-type excitation with ramped flip angles and a unique saturation scheme sensitive to the exchange between PCr and γATP. Parameter estimation was accomplished by matching the acquired signals to a dictionary generated using the Bloch-McConnell equation. Simulation studies were performed to examine the susceptibility of the CK-MRF method to several potential error sources. The accuracy of nonlocalized CK-MRF measurements before and after an ischemia-reperfusion (IR) protocol was compared with the magnetization transfer (MT-MRS) method in rat hindlimb at 9.4 T (n = 14). The reproducibility of CK-MRF was also assessed by comparing CK-MRF measurements with both MT-MRS (n = 17) and four angle saturation transfer (FAST) (n = 7). Simulation results showed that CK-MRF quantification of kfCK was robust, with less than 5% error in the presence of model inaccuracies including dictionary resolution, metabolite T values, inorganic phosphate metabolism, and B miscalibration. Estimation of kfCK by CK-MRF (0.38 ± 0.02 s at baseline and 0.42 ± 0.03 s post-IR) showed strong agreement with MT-MRS (0.39 ± 0.03 s at baseline and 0.44 ± 0.04 s post-IR). kfCK estimation was also similar between CK-MRF and FAST (0.38 ± 0.02 s for CK-MRF and 0.38 ± 0.11 s for FAST). The coefficient of variation from 20 s CK-MRF quantification of kfCK was 42% of that by 150 s MT-MRS acquisition and was 12% of that by 20 s FAST acquisition. This study demonstrates the potential of a P spectroscopic MRF framework for rapid, accurate and reproducible quantification of chemical exchange rate of CK in vivo.
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http://dx.doi.org/10.1002/nbm.3786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5690599PMC
December 2017

Dual Contrast - Magnetic Resonance Fingerprinting (DC-MRF): A Platform for Simultaneous Quantification of Multiple MRI Contrast Agents.

Sci Rep 2017 08 16;7(1):8431. Epub 2017 Aug 16.

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

Injectable Magnetic Resonance Imaging (MRI) contrast agents have been widely used to provide critical assessments of disease for both clinical and basic science imaging research studies. The scope of available MRI contrast agents has expanded over the years with the emergence of molecular imaging contrast agents specifically targeted to biological markers. Unfortunately, synergistic application of more than a single molecular contrast agent has been limited by MRI's ability to only dynamically measure a single agent at a time. In this study, a new Dual Contrast - Magnetic Resonance Fingerprinting (DC - MRF) methodology is described that can detect and independently quantify the local concentration of multiple MRI contrast agents following simultaneous administration. This "multi-color" MRI methodology provides the opportunity to monitor multiple molecular species simultaneously and provides a practical, quantitative imaging framework for the eventual clinical translation of molecular imaging contrast agents.
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http://dx.doi.org/10.1038/s41598-017-08762-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5559598PMC
August 2017

Low rank approximation methods for MR fingerprinting with large scale dictionaries.

Magn Reson Med 2018 04 13;79(4):2392-2400. Epub 2017 Aug 13.

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

Purpose: This work proposes new low rank approximation approaches with significant memory savings for large scale MR fingerprinting (MRF) problems.

Theory And Methods: We introduce a compressed MRF with randomized singular value decomposition method to significantly reduce the memory requirement for calculating a low rank approximation of large sized MRF dictionaries. We further relax this requirement by exploiting the structures of MRF dictionaries in the randomized singular value decomposition space and fitting them to low-degree polynomials to generate high resolution MRF parameter maps. In vivo 1.5T and 3T brain scan data are used to validate the approaches.

Results: T , T , and off-resonance maps are in good agreement with that of the standard MRF approach. Moreover, the memory savings is up to 1000 times for the MRF-fast imaging with steady-state precession sequence and more than 15 times for the MRF-balanced, steady-state free precession sequence.

Conclusion: The proposed compressed MRF with randomized singular value decomposition and dictionary fitting methods are memory efficient low rank approximation methods, which can benefit the usage of MRF in clinical settings. They also have great potentials in large scale MRF problems, such as problems considering multi-component MRF parameters or high resolution in the parameter space. Magn Reson Med 79:2392-2400, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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http://dx.doi.org/10.1002/mrm.26867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5811391PMC
April 2018

Regularly incremented phase encoding - MR fingerprinting (RIPE-MRF) for enhanced motion artifact suppression in preclinical cartesian MR fingerprinting.

Magn Reson Med 2018 04 10;79(4):2176-2182. Epub 2017 Aug 10.

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

Purpose: The regularly incremented phase encoding-magnetic resonance fingerprinting (RIPE-MRF) method is introduced to limit the sensitivity of preclinical MRF assessments to pulsatile and respiratory motion artifacts.

Methods: As compared to previously reported standard Cartesian-MRF methods (SC-MRF), the proposed RIPE-MRF method uses a modified Cartesian trajectory that varies the acquired phase-encoding line within each dynamic MRF dataset. Phantoms and mice were scanned without gating or triggering on a 7T preclinical MRI scanner using the RIPE-MRF and SC-MRF methods. In vitro phantom longitudinal relaxation time (T ) and transverse relaxation time (T ) measurements, as well as in vivo liver assessments of artifact-to-noise ratio (ANR) and MRF-based T and T mean and standard deviation, were compared between the two methods (n = 5).

Results: RIPE-MRF showed significant ANR reductions in regions of pulsatility (P < 0.005) and respiratory motion (P < 0.0005). RIPE-MRF also exhibited improved precision in T and T measurements in comparison to the SC-MRF method (P <  0.05). The RIPE-MRF and SC-MRF methods displayed similar mean T and T estimates (difference in mean values < 10%).

Conclusion: These results show that the RIPE-MRF method can provide effective motion artifact suppression with minimal impact on T and T accuracy for in vivo small animal MRI studies. Magn Reson Med 79:2176-2182, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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http://dx.doi.org/10.1002/mrm.26865DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5809208PMC
April 2018

Design analysis of an MPI human functional brain scanner.

Int J Magn Part Imaging 2017 23;3(1). Epub 2017 Mar 23.

MGH-HST A.A. Martinos Center for Biomedical Imaging, Dept. of Radiology, Massachusetts General Hospital, Charlestown, MA, USA.

MPI's high sensitivity makes it a promising modality for imaging brain function. Functional contrast is proposed based on blood SPION concentration changes due to Cerebral Blood Volume (CBV) increases during activation, a mechanism utilized in fMRI studies. MPI offers the potential for a direct and more sensitive measure of SPION concentration, and thus CBV, than fMRI. As such, fMPI could surpass fMRI in sensitivity, enhancing the scientific and clinical value of functional imaging. As human-sized MPI systems have not been attempted, we assess the technical challenges of scaling MPI from rodent to human brain. We use a full-system MPI simulator to test arbitrary hardware designs and encoding practices, and we examine tradeoffs imposed by constraints that arise when scaling to human size as well as safety constraints (PNS and central nervous system stimulation) not considered in animal scanners, thereby estimating spatial resolutions and sensitivities achievable with current technology. Using a projection FFL MPI system, we examine coil hardware options and their implications for sensitivity and spatial resolution. We estimate that an fMPI brain scanner is feasible, although with reduced sensitivity (20×) and spatial resolution (5×) compared to existing rodent systems. Nonetheless, it retains sufficient sensitivity and spatial resolution to make it an attractive future instrument for studying the human brain; additional technical innovations can result in further improvements.
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http://dx.doi.org/10.18416/ijmpi.2017.1703008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5526464PMC
March 2017
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