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1. Right Ventricular Function and T1 ‐Mapping in Boys With Duchenne Muscular Dystrophy

   https://doi.org/10.1002/jmri.27729  

   Dual, Seraina A. ; Maforo, Nyasha G. ; McElhinney, Doff B. ; Prosper, Ashley ; Wu, Holden H. ; Maskatia, Shiraz ; Renella, Pierangelo ; Halnon, Nancy ; Ennis, Daniel B. ( May 2021 , Journal of Magnetic Resonance Imaging)

   Clinical management of boys with Duchenne muscular dystrophy (DMD) relies on in‐depth understanding of cardiac involvement, but right ventricular (RV) structural and functional remodeling remains understudied.

   To evaluate several analysis methods and identify the most reliable one to measure RV pre‐ and postcontrast T1 (RV‐T1) and to characterize myocardial remodeling in the RV of boys with DMD.

   Prospective.

   Boys with DMD (N = 27) and age‐/sex‐matched healthy controls (N = 17) from two sites.

   3.0 T using balanced steady state free precession, motion‐corrected phase sensitive inversion recovery and modified Look‐Locker inversion recovery sequences.

   Biventricular mass (Mi), end‐diastolic volume (EDVi) and ejection fraction (EF) assessment, tricuspid annular excursion (TAE), late gadolinium enhancement (LGE), pre‐ and postcontrast myocardial T1 maps. The RV‐T1 reliability was assessed by three observers in four different RV regions of interest (ROI) using intraclass correlation (ICC).

   The Wilcoxon rank sum test was used to compare RV‐T1 differences between DMD boys with negative LGE(−) or positive LGE(+) and healthy controls. Additionally, correlation of precontrast RV‐T1 with functional measures was performed. AP‐value <0.05 was considered statistically significant.

   A 1‐pixel thick RV circumferential ROI proved most reliable (ICC > 0.91) for assessing RV‐T1. Precontrast RV‐T1 was significantly higher in boys with DMD compared to controls. Both LGE(−) and LGE(+) boys had significantly elevated precontrast RV‐T1 compared to controls (1543 [1489–1597] msec and 1550 [1402–1699] msec vs. 1436 [1399–1473] msec, respectively). Compared to healthy controls, boys with DMD had preserved RVEF (51.8 [9.9]% vs. 54.2 [7.2]%,P = 0.31) and significantly reduced RVMi (29.8 [9.7] g vs. 48.0 [15.7] g), RVEDVi (69.8 [29.7] mL/m²vs. 89.1 [21.9] mL/m²), and TAE (22.0 [3.2] cm vs. 26.0 [4.7] cm). Significant correlations were found between precontrast RV‐T1 and RVEF (β = −0.48%/msec) and between LV‐T1 and LVEF (β = −0.51%/msec).

   Precontrast RV‐T1 is elevated in boys with DMD compared to healthy controls and is negatively correlated with RVEF.

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2. Myocardial T 1 and T 2 quantification and water–fat separation using cardiac MR fingerprinting with rosette trajectories at 3T and 1.5T

   https://doi.org/10.1002/mrm.28404  

   Liu, Yuchi ; Hamilton, Jesse ; Eck, Brendan ; Griswold, Mark ; Seiberlich, Nicole ( July 2020 , Magnetic Resonance in Medicine)

   This work aims to develop an approach for simultaneous water–fat separation and myocardial T₁and T₂quantification based on the cardiac MR fingerprinting (cMRF) framework with rosette trajectories at 3T and 1.5T.

   Two 15‐heartbeat cMRF sequences with different rosette trajectories designed for water–fat separation at 3T and 1.5T were implemented. Water T₁and T₂maps, water image, and fat image were generated with B₀inhomogeneity correction using a B₀map 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.

   Water T₁and T₂values 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 T₁but 2~3 ms higher T₂values in the myocardium of healthy subjects than the original spiral cMRF method. Epicardial fat deposition was also clearly shown in the fat images.

   Rosette cMRF provides fat images along with myocardial T₁and T₂maps 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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3. Simultaneous multislice cardiac magnetic resonance fingerprinting using low rank reconstruction

   https://doi.org/10.1002/nbm.4041  

   Hamilton, Jesse I. ; Jiang, Yun ; Ma, Dan ; Chen, Yong ; Lo, Wei‐Ching ; Griswold, Mark ; Seiberlich, Nicole ( December 2018 , NMR in Biomedicine)

   This study introduces a technique for simultaneous multislice (SMS) cardiac magnetic resonance fingerprinting (cMRF), which improves the slice coverage when quantifying myocardialT_1,T₂, andM₀. 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 inT₁andT₂for 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 myocardialT₁andT₂mapping compared with both single‐slice cMRF and conventional cardiac mapping sequences. Thus, this technique is a first step toward whole‐heart simultaneousT₁andT₂quantification with cMRF.

    

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4. Spatial Gradients of Quantitative MRI as Biomarkers for Early Detection of Osteoarthritis: Data From Human Explants and the Osteoarthritis Initiative

   https://doi.org/10.1002/jmri.28471  

   Wilson, Robert L. ; Emery, Nancy C. ; Pierce, David M. ; Neu, Corey P. ( October 2022 , Journal of Magnetic Resonance Imaging)

   Healthy articular cartilage presents structural gradients defined by distinct zonal patterns through the thickness, which may be disrupted in the pathogenesis of several disorders. Analysis of textural patterns using quantitative MRI data may identify structural gradients of healthy or degenerating tissue that correlate with early osteoarthritis (OA).

   To quantify spatial gradients and patterns in MRI data, and to probe new candidate biomarkers for early severity of OA.

   Retrospective study.

   Fourteen volunteers receiving total knee replacement surgery (eight males/two females/four unknown, average age ± standard deviation: 68.1 ± 9.6 years) and 10 patients from the OA Initiative (OAI) with radiographic OA onset (two males/eight females, average age ± standard deviation: 57.7 ± 9.4 years; initial Kellgren‐Lawrence [KL] grade: 0; final KL grade: 3 over the 10‐year study).

   3.0‐T and 14.1‐T, biomechanics‐based displacement‐encoded imaging, fast spin echo, multi‐slice multi‐echoT2mapping.

   We studied structure and strain in cartilage explants from volunteers receiving total knee replacement, or structure in cartilage of OAI patients with progressive OA. We calculated spatial gradients of quantitative MRI measures (eg, T2) normal to the cartilage surface to enhance zonal variations. We compared gradient values against histologically OA severity, conventional relaxometry, and/or KL grades.

   Multiparametric linear regression for evaluation of the relationship between residuals of the mixed effects models and histologically determined OA severity scoring, with a significance threshold atα = 0.05.

   Gradients of individual relaxometry and biomechanics measures significantly correlated with OA severity, outperforming conventional relaxometry and strain metrics. In human explants, analysis of spatial gradients provided the strongest relationship to OA severity (R² = 0.627). Spatial gradients of T2 from OAI data identified variations in radiographic (KL Grade 2) OA severity in single subjects, while conventional T2 alone did not.

   Spatial gradients of quantitative MRI data may improve the predictive power of noninvasive imaging for early‐stage degeneration.

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5. Cardiac cine magnetic resonance fingerprinting for combined ejection fraction, T 1 and T 2 quantification

   https://doi.org/10.1002/nbm.4323  

   Hamilton, Jesse I. ; Jiang, Yun ; Eck, Brendan ; Griswold, Mark ; Seiberlich, Nicole ( June 2020 , NMR in Biomedicine)

   This study introduces a technique called cine magnetic resonance fingerprinting (cine‐MRF) for simultaneous T₁, T₂and 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 T₁and T₂maps. 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 mm²and 24 cardiac phases. Left ventricular EF values obtained with cine‐MRF agreed with the conventional cine images (mean bias −1.0%). Average myocardial T₁times 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 T₂values 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 T₂‐prepared FLASH. Cine‐MRF and ECG‐triggered cMRF relaxation times were in good agreement. Cine‐MRF T₁values were significantly longer than MOLLI, and cine‐MRF T₂values were significantly shorter than T₂‐prepared FLASH. In summary, cine‐MRF can potentially streamline cardiac MRI exams by combining left ventricle functional assessment and T₁‐T₂mapping into one time‐efficient acquisition.

    

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