Steady-state Free Precession Sequence Research Articles

Imaging ocular water inflow in the mouse with deuterium oxide MRI

Abnormal intraocular fluid flow or clearance is involved with a variety of eye diseases such as glaucoma and diabetic retinopathy, but measurement of water exchange dynamics in the vitreous and aqueous remain challenging. 2H MRI can be used to image deuterium oxide (D₂O) as a tracer, but the signal-to-noise ratio for deuterium is low due to its low concentration, which has hampered its application to imaging the eye. To overcome this challenge, we investigated the feasibility of direct D2O MRI to measure water dynamics in the mouse eye. The balanced steady-state free precession (bSSFP) sequence provided substantially higher signal-to-noise ratio for imaging D2O in fluid compared to standard gradient echo and spin echo sequences. bSSFP allowed dynamic imaging of intraocular water inflow in the mouse with 41 s temporal resolution. The inflow rate in the vitreous was found to be faster than in the aqueous. These studies demonstrate the feasibility of in vivo imaging of water inflow dynamics into the both the vitreous and aqueous in mice, which could be useful in studies of abnormal fluid exchange in rodent models of eye disease.

Potential Prognostic Value of Native T1 in Pulmonary Hypertension Patients.

Native T1, extracellular volume fraction (ECV), and late gadolinium enhancement (LGE) characterize myocardial tissue and relate to patient prognosis in a variety of diseases, including pulmonary hypertension. The purpose of this study was to evaluate if left ventricle (LV) fibrosis measurements have prognostic value for cardiac outcomes in pulmonary hypertension subgroups. 54 patients with suspected pulmonary hypertension underwent right-heart catheterization and were classified into pulmonary hypertension subgroups: pre-capillary component (PreCompPH) and isolated post-capillary (IpcPH). Cardiac magnetic resonance imaging (MRI) scans were performed with the acquisition of balanced cine steady-state free precession, native T1, and LGE pulse sequences to measure cardiac volumes and myocardial fibrosis. Associations between cardiac events and cardiac MRI measurements were analyzed within PreCompPH and IpcPH patients. IpcPH: LV native T1 was higher in patients who experienced a cardiac event within two years vs. those who did not. In patients with LV native T1 > 1050 ms, the rate of cardiac events was higher. ECV and quantitative LGE did not differ between groups. PreCompPH: native T1, ECV, and quantitative/qualitative LGE did not differ between patients who experienced a cardiac event within two years vs. those who did not. LV native T1 may have potential value for forecasting cardiac events in IpcPH, but not in PreCompPH, patients.

Low Prevalence of Late Myocardial Injury on Cardiac MRI Following COVID-19 Infection.

The prevalence of abnormal cardiac magnetic resonance imaging (MRI) findings indicative of myocardial injury in patients who recovered from coronavirus disease 2019 (COVID-19) is currently unclear, with a high variability in the reported prevalence. To assess the prevalence of myocardial injury after a COVID-19 infection. Prospective, bicentric study. Seventy consecutive patients who recovered from COVID-19 and were previously hospitalized. Mean age was 57 years and 39% of the patients were female. Ten healthy controls and a comparator group of 75 nonischemic cardiomyopathy (NICM) patients were employed. 1.5-T, steady-state free precession (SSFP) gradient-echo sequence, modified Look-Locker inversion recovery sequence with balanced SSFP readout, T2-prepared spiral readout sequence and a T1-weighted inversion recovery fast gradient-echo sequence was acquired ~4-5 months after recovery from COVID-19. The SSFP sequence was utilized for the calculation of left and right ventricular volumes and ejection fractions (LVEF and RVEF) following manual endocardial contouring. T1 and T2 mapping was performed by pixel-wise exponential fitting, and T1 and T2 values were computed by manual contouring of the left ventricular endocardial and epicardial walls. Late gadolinium enhancement (LGE) images were graded qualitatively as LGE present or absent. T-tests and the χ2 or Fisher's exact tests were used to compare continuous and categorical variables respectively between the COVID-19 and NICM groups. Inter-rater agreement was evaluated by the intraclass correlation coefficient for continuous variables and Cohen's kappa test for LGE. Reduced RVEF occurred in 10%, LGE and elevated native T1 in 9%, reduced LVEF in 4%, and elevated T2 in 3% of COVID-19 patients, respectively. Patients with NICM had lower mean LVEF (41.6% ± 6% vs. 60% ± 7%), RVEF (46% ± 5% vs. 61% ± 9%), and a significantly higher prevalence of LGE (27% vs. 9%) when compared to those post-COVID-19. Abnormal cardiac MRI findings may show a low prevalence in patients who recovered from COVID-19 and were previously hospitalized. 2 TECHNICAL EFFICACY: Stage 2.

Magnetic resonance imaging reference values for cardiac morphology, function and tissue composition in adolescents.

Cardiovascular magnetic resonance (CMR) is a precise tool for the assessment of cardiac anatomy, function, and tissue composition. However, studies providing CMR reference values in adolescence are scarce. We aim to provide sex-specific CMR reference values for biventricular and atrial dimensions and function and myocardial relaxation times in this population. Adolescents aged 15-18 years with no known cardiovascular disease underwent a non-contrast 3-T CMR scan between March 2021 and October 2021. The imaging protocol included a cine steady-state free-precession sequence for the analysis of chamber size and function, as well as T2-GraSE and native MOLLI T1-mapping for the characterization of myocardial tissue. CMR scans were performed in 123 adolescents (mean age 16±0.5 years, 52% girls). Mean left and right ventricular end-diastolic indexed volumes were higher in boys than in girls (91.7±11.6 vs 78.1±8.3ml/m2, p<0.001; and 101.3±14.1 vs 84.1±10.5ml/m2, p<0.001), as was the indexed left ventricular mass (48.5±9.6 vs 36.6±6.0g/m2, p<0.001). Left ventricular ejection fraction showed no significant difference by sex (62.2±4.1 vs 62.8±4.2%, p=0.412), whereas right ventricular ejection fraction trended slightly lower in boys (55.4±4.7 vs. 56.8±4.4%, p=0.085). Indexed atrial size and function parameters did not differ significantly between sexes. Global myocardial native T1 relaxation time was lower in boys than in girls (1215±23 vs 1252±28ms, p<0.001), whereas global myocardial T2 relaxation time did not differ by sex (44.4±2.0 vs 44.1±2.4ms, p=0.384). Sex-stratified comprehensive percentile tables are provided for most relevant cardiac parameters. This cross-sectional study provides overall and sex-stratified CMR reference values for cardiac dimensions and function, and myocardial tissue properties, in adolescents. This information is useful for clinical practice and may help in the differential diagnosis of cardiac diseases, such as cardiomyopathies and myocarditis, in this population. Instituto de Salud Carlos III (PI19/01704).

Non-contrast MR angiography of pelvic arterial vasculature using the Quiescent interval slice selective (QISS) sequence.

To evaluate Quiescent Interval Slice Selective (QISS) balanced steady-state free precession (bSSFP) and QISS fast low-angle shot (FLASH) sequences for non-contrast Magnetic Resonance Angiography (MRA) of iliac arteries regarding image quality and diagnostic confidence in order to establish these sequences in daily clinical practice. A prospective study of healthy subjects (n = 10) was performed. All subjects underwent the QISS MRI protocol with bSSFP und FLASH sequences. Vessel contrast-to-background ratio (VCBR) were measured in pre-defined vessel segments. Image quality and diagnostic confidence was assessed using a Likert scale (five-point scale). Inter-reader agreement was determined using Cohen's kappa coefficient (κ). Ten healthy subjects (median age 29 years, IQR: 26.25 to 30 years) were included in this prospective study. Median MR examination time was 2:05min (IQR 1:58 to 2:16) for QISS bSSFP and 4:11min (IQR 3:57 to 4:32) for QISS FLASH. Both sequences revealed good VCBR in all examined vessel segments. VCBR (muscle tissue) were marginally higher for FLASH sequences (e.g., 0.82 vs. 0.78 in the right femoral artery, p = 0.035*), while bSSFP sequence showed significantly higher VCBR (fat tissue) in the majority of examined arterials vessels (e.g., 0.78 vs. 0.62 in right femoral artery, p = 0.001*). The image quality and diagnostic confidence of both sequences were rated as good to excellent. Moderate to good inter-reader agreement was found. QISS MRA using bSSFP and FLASH sequences are diagnostic for visualization of iliac arterial vasculature. The QISS bSSFP sequence might offer advantages due to the markedly shorter exam time and superior visualization of smaller vessels. The QISS FLASH sequence seems to be a robust alternative for non-contrast MRA since it is less sensitive to magnetic field inhomogeneities.

MRI Investigation of the Differential Impact of Left Ventricular Ejection Fraction After Myocardial Infarction in Elderly vs. Nonelderly Patients to Predict Readmission for Heart Failure.

Patients with ST-segment elevation myocardial infarction (STEMI), especially elderly individuals, have an increased risk of readmission for acute heart failure (AHF). To study the impact of left ventricular ejection fraction (LVEF) by MRI to predict AHF in elderly (>70 years) and nonelderly patients after STEMI. Prospective. Multicenter registry of 759 reperfused STEMI patients (23.3% elderly). 1.5-T. Balanced steady-state free precession (cine imaging) and segmented inversion recovery steady-state free precession (late gadolinium enhancement) sequences. One-week MRI-derived LVEF (%) was quantified. Sequential MRI data were recorded in 579 patients. Patients were categorized according to their MRI-derived LVEF as preserved (p-LVEF, ≥50%), mildly reduced (mr-LVEF, 41%-49%), or reduced (r-LVEF, ≤40%). Median follow-up was 5 [2.33-7.54] years. Univariable (Student's t, Mann-Whitney U, chi-square, and Fisher's exact tests) and multivariable (Cox proportional hazard regression) comparisons and continuous-time multistate Markov model to analyze transitions between LVEF categories and to AHF. Hazard ratios (HR) with 95% confidence intervals (CIs) were computed. P < 0.05 was considered statistically significant. Over the follow-up period, 79 (10.4%) patients presented AHF. MRI-LVEF was the most robust predictor in nonelderly (HR 0.94 [0.91-0.98]) and elderly patients (HR 0.94 [0.91-0.97]). Elderly patients had an increased AHF risk across the LVEF spectrum. An excess of risk (compared to p-LVEF) was noted in patients with r-LVEF both in nonelderly (HR 11.25 [5.67-22.32]) and elderly patients (HR 7.55 [3.29-17.34]). However, the mr-LVEF category was associated with increased AHF risk only in elderly patients (HR 3.66 [1.54-8.68]). Less transitions to higher LVEF states (n=19, 30.2% vs. n=98, 53%) and more transitions to AHF state (n=34, 53.9% vs. n=45, 24.3%) were observed in elderly than nonelderly patients. MRI-derived p-LVEF confers a favorable prognosis and r-LVEF identifies individuals at the highest risk of AHF in both elderly and nonelderly patients. Nevertheless, an excess of risk was also found in the mr-LVEF category in the elderly group. 2. Stage 2.

Myocardial late gadolinium enhancement using delayed 3D IR-FLASH in the pediatric population: feasibility and diagnostic performance compared to single-shot PSIR-bSSFP

BackgroundThis study compares three-dimensional (3D) high-resolution (HR) late gadolinium enhancement (LGE; 3D HR-LGE) imaging using a respiratory navigated, electrocardiographically-gated inversion recovery gradient echo sequence with conventional LGE imaging using a single-shot phase-sensitive inversion recovery (PSIR) balanced steady-state free precession (bSSFP; PSIR-bSSFP) sequence for routine clinical use in the pediatric population. MethodsPediatric patients (0–18 years) who underwent clinical cardiovascular magnetic resonance (CMR) with both 3D HR-LGE and single-shot PSIR-bSSFP LGE between January 2018 and June 2020 were included. Image quality (0–4) and detection of LGE in the left ventricle (LV) (per 17 segments), in the right ventricle (RV) (per 3 segments), as endocardial fibroelastosis (EFE), at the hinge points, and at the papillary muscles was analyzed by two blinded readers for each sequence. Ratios of the mean signal intensity of LGE to normal myocardium (LGE:Myo) and to LV blood pool (LGE:Blood) were recorded. Data is presented as median (1st–3rd quartiles). Wilcoxon signed rank test and chi-square analyses were used as appropriate. Inter-rater agreement was analyzed using weighted κ-statistics. Results102 patients were included with median age at CMR of 8 (1–13) years-old and 44% of exams performed under general anesthesia. LGE was detected in 55% of cases. 3D HR LGE compared to single-shot PSIR-bSSFP had longer scan time [4:30 (3:35–5:34) vs 1:11 (0:47–1:32) minutes, p < 0.001], higher image quality ratings [3 (3–4) vs 2 (2–3), p < 0.001], higher LGE:Myo [23.7 (16.9–31.2) vs 5.0 (2.9–9.0), p < 0.001], detected more segments of LGE in both the LV [4 (2–8) vs 3 (1–7), p = 0.045] and RV [1 (1–1) vs 1 (0–1), p < 0.001], and also detected more cases of LGE with 13/56 (23%) of patients with LGE only detectable by 3D HR LGE (p < 0.001). 3D HR LGE specifically detected a greater proportion of RV LGE (27/27 vs 17/27, p < 0.001), EFE (11/11 vs 5/11, p = 0.004), and papillary muscle LGE (14/15 vs 4/15, p < 0.001). Inter-rater agreement for the recorded variables ranged from 0.42 to 1.00. Conclusions3D HR LGE achieves greater image quality and detects more LGE than conventional single-shot PSIR-bSSFP LGE imaging, and should be considered an alternative to conventional LGE sequences for routine clinical use in the pediatric population.

Free-breathing, Contrast Agent-free Whole-Heart MTC-BOOST Imaging: Single-Center Validation Study in Adult Congenital Heart Disease.

To assess the clinical performance of the three-dimensional, free-breathing, Magnetization Transfer Contrast Bright-and-black blOOd phase-SensiTive (MTC-BOOST) sequence in adult congenital heart disease (ACHD). In this prospective study, participants with ACHD undergoing cardiac MRI between July 2020 and March 2021 were scanned with the clinical T2-prepared balanced steady-state free precession sequence and proposed MTC-BOOST sequence. Four cardiologists scored their diagnostic confidence on a four-point Likert scale for sequential segmental analysis on images acquired with each sequence. Scan times and diagnostic confidence were compared using the Mann-Whitney test. Coaxial vascular dimensions at three anatomic landmarks were measured, and agreement between the research sequence and the corresponding clinical sequence was assessed with Bland-Altman analysis. The study included 120 participants (mean age, 33 years ± 13 [SD]; 65 men). The mean acquisition time of the MTC-BOOST sequence was significantly lower compared with that of the conventional clinical sequence (9 minutes ± 2 vs 14 minutes ± 5; P < .001). Diagnostic confidence was higher for the MTC-BOOST sequence compared with the clinical sequence (mean, 3.9 ± 0.3 vs 3.4 ± 0.7; P < .001). Narrow limits of agreement and mean bias less than 0.08 cm were found between the research and clinical vascular measurements. The MTC-BOOST sequence provided efficient, high-quality, and contrast agent-free three-dimensional whole-heart imaging in ACHD, with shorter, more predictable acquisition time and improved diagnostic confidence compared with the reference standard clinical sequence.Keywords: MR Angiography, Cardiac Supplemental material is available for this article. Published under a CC BY 4.0 license.

Approximate scaling of the SSFP steady state.

It is shown that the steady state of rapid, TR-periodic steady-state free precession (SSFP) sequences at small to moderate flip angles exhibits a universal, approximate scaling law with respect to variations of . Implications for the accuracy and precision of relaxometry experiments are discussed. The approximate scaling law is derived from and numerically tested against known analytical solutions. To assess the attainable estimator precision in a typical relaxometry experiment, we calculate the Cramér-Rao bound (CRB) and perform Monte Carlo (MC) simulations. The approximate universal scaling holds well up to moderate flip angles. For pure steady state relaxometry, we observe a significant precision penalty for simultaneous estimation of and , whereas good estimates can be obtained without even knowing the correct actual flip angle. Simultaneous estimation of and from a set of SSFP steady states alone is not advisable. Apart from separate measurements, the problem can be addressed by adding transient state information, but, depending on the situation, residual effects due to the scaling may still require some attention.

An Integrated Algorithm for Differentiating Hypertrophic Cardiomyopathy From Hypertensive Heart Disease.

Differentiating hypertrophic cardiomyopathy (HCM) from hypertensive heart disease (HHD) is challenging. To identify differences between HCM and HHD on a patient basis using MRI. Retrospective. A total of 219 subjects, 148 in phase I (baseline data and algorithm development: 75 HCM, 33 HHD, and 40 controls) and 71 in phase II (algorithm validation: 56 HCM and 15 HHD). Contrast-enhanced inversion-prepared gradient echo and cine-balanced steady-state free precession sequences at 3.0 T. MRI parameters assessed included left ventricular (LV) ejection fraction (LVEF), LV end systolic and end diastolic volumes (LVESV and LVEDV), mean maximum LV wall thickness (MLVWT), LV global longitudinal and circumferential strain (GRS, GLS, and GCS), and native T1. Parameters, which were significantly different between HCM and HHD in univariable analysis, were entered into a principal component analysis (PCA). The selected components were then introduced into a multivariable regression analysis to model an integrated algorithm (IntA) for screening the two disorders. IntA performance was assessed for patients with and without LGE in phase I (development) and phase II (validation). Univariable regression, PCA, receiver operating curve (ROC) analysis. A P value <0.05 was considered statistically significant. Derived IntA formulation included LVEF, LVESV, LVEDV, MLVWT, and GCS. In LGE-positive subjects in phase l, the cutoff point of IntA ≥81 indicated HCM (83% sensitivity and 91% specificity), with the area under the ROC curve (AUC) of 0.900. In LGE-negative subjects, a higher possibility of HCM was indicated by a cutoff point of IntA ≥84 (100% sensitivity and 82% specificity), with an AUC of 0.947. Validation of IntA in phase II resulted in an AUC of 0.846 in LGE-negative subjects and 0.857 in LGE-positive subjects. A per-patient-based IntA algorithm for differentiating HCM and HHD was generated from MRI data and incorporated FT, LGE and morphologic parameters. 3. Stage 2.

Effect of Averaging Measurements From Multiple MRI Pulse Sequences on Kidney Volume Reproducibility in Autosomal Dominant Polycystic Kidney Disease.

Total kidney volume (TKV) is an important biomarker for assessing kidney function, especially for autosomal dominant polycystic kidney disease (ADPKD). However, TKV measurements from a single MRI pulse sequence have limited reproducibility, ± ~5%, similar to ADPKD annual kidney growth rates. To improve TKV measurement reproducibility on MRI by extending artificial intelligence algorithms to automatically segment kidneys on T1-weighted, T2-weighted, and steady state free precession (SSFP) sequences in axial and coronal planes and averaging measurements. Retrospective training, prospective testing. Three hundred ninety-seven patients (356 with ADPKD, 41 without), 75% for training and 25% for validation, 40 ADPKD patients for testing and 17 ADPKD patients for assessing reproducibility. T2-weighted single-shot fast spin echo (T2), SSFP, and T1-weighted 3D spoiled gradient echo (T1) at 1.5 and 3T. 2D U-net segmentation algorithm was trained on images from all sequences. Five observers independently measured each kidney volume manually on axial T2 and using model-assisted segmentations on all sequences and image plane orientations for two MRI exams in two sessions separated by 1-3 weeks to assess reproducibility. Manual and model-assisted segmentation times were recorded. Bland-Altman, Schapiro-Wilk (normality assessment), Pearson's chi-squared (categorical variables); Dice similarity coefficient, interclass correlation coefficient, and concordance correlation coefficient for analyzing TKV reproducibility. P-value < 0.05 was considered statistically significant. In 17 ADPKD subjects, model-assisted segmentations of axial T2 images were significantly faster than manual segmentations (2:49 minute vs. 11:34 minute), with no significant absolute percent difference in TKV (5.9% vs. 5.3%, P=0.88) between scans 1 and 2. Absolute percent differences between the two scans for model-assisted segmentations on other sequences were 5.5% (axial T1), 4.5% (axial SSFP), 4.1% (coronal SSFP), and 3.2% (coronal T2). Averaging measurements from all five model-assisted segmentations significantly reduced absolute percent difference to 2.5%, further improving to 2.1% after excluding an outlier. Measuring TKV on multiple MRI pulse sequences in coronal and axial planes is practical with deep learning model-assisted segmentations and can improve TKV measurement reproducibility more than 2-fold in ADPKD. 2 TECHNICAL EFFICACY: Stage 1.

Bladder involvement in placenta accreta spectrum disorder with placenta previa: MRI findings and outcomes correlation

BackgroundPlacental accreta spectrum (PAS) disorder with bladder involvement can be associated with maternal and neonatal morbidity. Magnetic resonance imaging (MRI) may provide accurate preoperative diagnoses. ObjectiveThis study had 2 aims: to retrospectively review the MRI findings for bladder involvement in PAS with placental previa and to correlate bladder involvement with maternal and neonatal outcomes. Materials and methodsMRI images of 48 patients with severe PAS (increta and percreta) with placenta previa/low-lying placenta were evaluated by 2 experienced radiologists blinded to the final diagnoses. Nine MRI findings and stepwise logistic regression analysis were assessed to identify predictive MRI findings for bladder involvement. The correlations between PAS patients with bladder involvement and clinical outcomes were analyzed using Fisher’s exact test. ResultsOf the 48 patients, 27 did not have bladder involvement, while 21 did. Logistic regression analysis identified 2 predictive MRI features for bladder involvement. They were abnormal vascularization (OR,6.94; 95 %CI,1.05–45.75) and loss of the chemical shift line at the uterovesical interface (OR, 4.41; 95 %CI, 0.63–30.98). The sensitivity and specificity of the combined MRI features were 38.1 % and 100 %, respectively (p = 0.001). A significant correlation was found between bladder involvement and massive blood loss during surgery (p = 0.022). ConclusionsPAS with bladder involvement was significantly correlated with massive surgical blood loss. Prenatally, the disorder was predicted with high specificity by the combination of loss of chemical shift artifacts in the steady-state free precession sequence and abnormal vascularization at the uterovesical interface on MRI.

Feasibility of Non-Gated Dynamic Fetal Cardiac MRI for Identification of Fetal Cardiovascular Anatomy

Introduction: The aim of this study was to evaluate the feasibility of identifying the fetal cardiac and thoracic vascular structures with non-gated dynamic balanced steady-state free precession (SSFP) MRI sequences. Methods: We retrospectively assessed the visibility of cardiovascular anatomy in 60 fetuses without suspicion of congenital heart defect. Non-gated dynamic balanced SSFP sequences were acquired in three anatomic planes of the fetal thorax. The images were analyzed following a segmental approach in consensus reading by an experienced pediatric cardiologist and radiologist. An imaging score was defined by giving one point to each visualized structure, yielding a maximum score of 21 points. Image quality was rated from 0 (poor) to 2 (excellent). The influence of gestational age (GA), field strength, placenta position, and maternal panniculus on image quality and imaging score were tested. Results: 30 scans were performed at 1.5T, 30 at 3T. Heart position, atria, and ventricles could be seen in all 60 fetuses. Basic diagnosis (>12 points) was achieved in 54 cases. The mean imaging score was 16.8+/−3.8. Maternal panniculus (r = −0.3; p = 0.015) and GA (r = 0.6; p < 0.001) correlated with imaging score. Field strength influenced image quality, with 1.5T being better than 3T images (p = 0.012). Imaging score or quality was independent of placenta position. Conclusion: Fetal cardiac MRI with non-gated SSFP sequences enables recognition of basic cardiovascular anatomy.

Effect of Metabolic Dysfunction-Associated Fatty Liver Disease on Left Ventricular Deformation and Atrioventricular Coupling in Patients With Metabolic Syndrome Assessed by MRI.

Metabolic dysfunction-associated fatty liver disease (MAFLD) was recently recognized as an important risk factor for cardiovascular diseases. To examine the effect of MAFLD on cardiac function in metabolic syndrome by MRI. Retrospective. One hundred seventy-nine patients with metabolic syndrome (MetS), 101 with MAFLD (MAFLD [+]) and 78 without (MAFLD [-]). Eighty-one adults without any of the components of MetS or cardiac abnormalities were included as control group. 3.0 T; balanced steady-state free precession sequence. Left atrial (LA) strain was assessed during three phases: reservoir strain (LA-RS), conduit strain (LA-CS), and booster strain (LA-BS). Left ventricular (LV) global longitudinal (LV-GLS) strain was also derived. The left atrioventricular coupling index (LACI) was calculated as the ratio of LA end-diastolic volume (LA-EDV) and LV-EDV. Student's t test or Mann-Whitney U test; One-way analysis of variance. A P value <0.05 was considered statistically significant. Among MetS patients, individuals with MAFLD had significantly lower magnitude LV-GLS (-11.6% ± 3.3% vs. -13.8% ± 2.7%) than those without MAFLD. For LA strains, LA-RS (36.9% ± 13.7% vs. 42.9% ± 13.5%) and LA-CS (20.0% ± 10.6% vs. 24.1% ± 9.2%) were also significantly reduced in MAFLD (+) compared to MAFLD (-). The LACIs (17.2% [12.9-21.2] % vs. 15.8% [12.2-19.7] %) were significantly higher in patients with MAFLD compared to those without MAFLD. After adjustment for other clinical factors, MAFLD was found to be independently correlated with LV-GLS (β=-0.270) and LACI (β=0.260). MAFLD had an unfavorable effect on LV myocardial strain in MetS. Moreover, LA strain and atrioventricular coupling were further impaired in patients with concomitant MAFLD compared to those without MAFLD. Last, MAFLD was independently associated with subclinical LV dysfunction and atrioventricular coupling after adjustment for other clinical factors. 3 TECHNICAL EFFICACY: 3.

Motility Mapping Quantification Using the Classical Optical Flow Algorithm for Small Bowel Crohn's Disease: Comparison with Balloon-assisted Enteroscopy Findings.

To quantify bowel motility shown on cine MRI using the classical optical flow algorithm and compare it with balloon-assisted enteroscopy (BAE) findings in patients with Crohn's disease (CD). This retrospective study included 29 consecutive patients with CD who had undergone MR enterocolonography (MREC) and BAE between March and May 2017. We developed computer software to present motion vector magnitudes between consecutive cine MR images as bowel motility maps via a classical optical flow algorithm using the Horn-Schunck method. Cine MR images were acquired with a balanced steady-state free precession sequence in the coronal direction to capture small bowel motility. The small bowels were divided into three segments. In total, 63 bowel segments were assessed via BAE and MREC. Motility scores on the maps, simplified MR index of activity (sMaRIA), and MREC score derived from a 5-point MR classification were assessed independently by two radiologists and compared with the CD endoscopic index of severity (CDEIS). Correlations were assessed using Spearman's rank coefficient. The areas under the receiver-operating characteristic curve (AUCs) of motility score for differentiating CDEIS was calculated; a P value < 0.05 was considered statistically significant. Motility score was negatively correlated with CDEIS (r = -0.59 [P < 0.001] and -0.54 [P < 0.001]), and the AUCs of motility scores for detecting CDEIS ≥ 3 were 88.2% and 78.6% for observers 1 and 2, respectively. There were no significant differences in the AUC for detecting CDEIS ≥ 3 and CDEIS ≥ 12 between motility and sMaRIA or MREC score. The motility map was feasible for locally quantifying the bowel motility. In addition, the motility score on the map reflected the endoscopic inflammatory activity of each small bowel segment in patients with CD; hence, it could be used as a tool in objectively interpreting cine MREC to predict inflammatory activity in CD.

Automated MR Image Prescription of the Liver Using Deep Learning: Development, Evaluation, and Prospective Implementation.

There is an unmet need for fully automated image prescription of the liver to enable efficient, reproducible MRI. To develop and evaluate artificial intelligence (AI)-based liver image prescription. Prospective. A total of 570 female/469 male patients (age: 56 ± 17 years) with 72%/8%/20% assigned randomly for training/validation/testing; two female/four male healthy volunteers (age: 31 ± 6 years). 1.5 T, 3.0 T; spin echo, gradient echo, bSSFP. A total of 1039 three-plane localizer acquisitions (26,929 slices) from consecutive clinical liver MRI examinations were retrieved retrospectively and annotated by six radiologists. The localizer images and manual annotations were used to train an object-detection convolutional neural network (YOLOv3) to detect multiple object classes (liver, torso, and arms) across localizer image orientations and to output corresponding 2D bounding boxes. Whole-liver image prescription in standard orientations was obtained based on these bounding boxes. 2D detection performance was evaluated on test datasets by calculating intersection over union (IoU) between manual and automated labeling. 3D prescription accuracy was calculated by measuring the boundary mismatch in each dimension and percentage of manual volume covered by AI prescription. The automated prescription was implemented on a 3T MR system and evaluated prospectively on healthy volunteers. Paired t-tests (threshold=0.05) were conducted to evaluate significance of performance difference between trained networks. In 208 testing datasets, the proposed method with full network had excellent agreement with manual annotations, with median IoU > 0.91 (interquartile range < 0.09) across all seven classes. The automated 3D prescription was accurate, with shifts <2.3cm in superior/inferior dimension for 3D axial prescription for 99.5% of test datasets, comparable to radiologists' interreader reproducibility. The full network had significantly superior performance than the tiny network for 3D axial prescription in patients. Automated prescription performed well across single-shot fast spin-echo, gradient-echo, and balanced steady-state free-precession sequences in the prospective study. AI-based automated liver image prescription demonstrated promising performance across the patients, pathologies, and field strengths studied. 4. Stage 1.

Steady-State Free Precession sequences for high and low field NMR spectroscopy in solution: Challenges and opportunities

The receptivity of NMR spectroscopy is low when compared to other techniques. Historically, increasing the strength of the static magnetic field has been the major approach to increase NMR sensitivity. In recent years several polarization transfer protocols have been used to enhance the signal-to-noise ratio (SNR), although they require special accessories and/or sample preparation. In this paper, we consider both the challenges and opportunities of steady-state free precession (SSFP) pulse sequences as a simple and efficient alternative to enhance SNR, in standard high-resolution and benchtop low-resolution NMR spectrometers. The maximum gain in these sequences is obtained with the shortest time between the pulses (Tp). However, when Tp<T2, the SSFP signal contains FID and echo components which lead to phase, intensity, and truncation artifacts on spectra obtained by Fast Fourier transform (FT). Several phase alternation SSFP sequences were used to cancel the echo component and minimize these problems in the FT spectra. Krylov base diagonalization method (KBDM) was used to eliminate the phase and truncation problems in spectra acquired by SSFP pulse sequences and can be a viable alternative to FT. The experiments were performed in high and low resolution (bench top) NMR spectrometers and significant enhancements in SNR of low receptivity nuclei such as 13C and 15N could be achieved. The SSFP sequences were also shown to enhance SNR in nuclei with high receptivity such as 19F and 31P, in very dilute samples, as is common in environmental and biological samples.

CMR feature tracking in patients with dilated cardiomyopathy: patterns of myocardial strain and focal fibrosis

BackgroundThere is a paucity of data on cardiovascular magnetic resonance feature tracking (CMR-FT) in patients with dilated cardiomyopathy (DCM). We aimed at describing global and segmental myocardial strain patterns and...

Normal Values of Magnetic Resonance T1ρ Relaxation Times in the Adult Heart at 1.5T MRI.

T1ρ mapping is a new quantitative MRI technique in recent years. In order to use T1ρ mapping as a noncontrast method to assess myocardial fibrosis, it is necessary to establish a range of normal values. To establish a potential normal range of cardiac T1ρ values in healthy adults and to explore the influence of slice location and gender on T1ρ values. Prospective. A total of 57 healthy volunteers without cardiovascular risk factors (age 26.7 ± 11.8 years; 29 males). 1.5 T; modified Look-Locker inversion recovery (MOLLI) (T1 mapping), multiecho gradient-spin-echo (GraSE) (T2 mapping) and T1ρ -prepared steady-state free precession (T1ρ mapping) sequences. Basal, mid, and apical short-axis left ventricular T1 , T2 , and T1ρ maps were acquired. T1ρ maps at spin-locking frequencies of 5 and 400 Hz were subtracted to create myocardial fibrosis index (mFI) maps. Slice-average and global average T1 , T2 , T1ρ , and mFI values were determined. Shapiro-Wilk test, Independent t-test, ANOVA test, Pearson correlation coefficient (r). P value < 0.05. The global average values of T1 , T2 , T1ρ, and mFI were 1053 ± 34 msec, 51.9 ± 2.3msec, 47.9 ± 2.8msec, and 4.4 ± 1.6msec. T1ρ values showed a significant gradual increase from the basal slice to the apical slice of the heart (basal 46.5 ± 2.7msec, mid 48.0 ± 2.9msec, apical 49.2 ± 3.3msec). The T1ρ and mFI values of females (49.7 ± 2.4msec and 5.1 ± 1.2msec, respectively) were significantly higher than those of males (46.2 ± 1.9msec and 3.7 ± 1.7msec, respectively). In addition, there was a moderate positive correlation between global T1ρ values and global T1 values (r=0.44, P < 0.05) and a moderate positive correlation between global T1ρ values and global T2 values (r=0.42, P < 0.05). In this study, the global T1ρ values of healthy adults' hearts were 47.9 ± 2.8msec. This study found that gender and slice location of myocardium can affect the T1ρ values. 4 TECHNICAL EFFICACY: Stage 1.

Feasibility of flow-related enhancement brain perfusion MRI.

Brain perfusion imaging is of enormous importance for various neurological diseases. Fast gradient-echo sequences offering flow-related enhancement (FREE) could present a basis to generate perfusion-weighted maps. In this study, we obtained perfusion-weighted maps without contrast media by a previously described postprocessing algorithm from the field of functional lung MRI. At first, the perfusion signal was analyzed in fast low-angle shot (FLASH) and balanced steady-state free precession (bSSFP) sequences. Secondly, perfusion maps were compared to pseudo-continuous arterial spin labeling (pCASL) MRI in a healthy cohort. Thirdly, the feasibility of the new technique was demonstrated in a small selected group of patients with metastases and acute stroke. One participant was examined with bSSFP and FLASH sequences at 1.5T and 3T, different flip angles and slice thicknesses. Twenty-five volunteers had bSSFP imaging and pCASL MRI. Three patients with cerebral metastases and one with acute ischemic stroke had bSSFP imaging and were compared to T1 post-contrast images and CT perfusion. Frequency analyses, SNR and perfusion contrast were compared at different flip angles and slice thicknesses. Regional correlations and Sorensen-Dice overlap were calculated in the healthy cohort. Dice overlap of the pathologies in the patient cohort were calculated. The bSSFP sequence presented detectable perfusion signal within brain vessel and parenchyma together with superior SNR compared to FLASH. Perfusion contrast and its corticomedullary differentiation increased with flip angle. Mean regional correlation was 0.36 and highly significant between FREE maps and pCASL and grey and white matter Dice match were 72% and 60% in the healthy cohort. Pathologies presented good overlap between FREE perfusion-weighted and T1 post-contrast images. The feasibility of FREE brain perfusion imaging has been shown in a healthy cohort and selected patient cases with brain metastases and acute stroke. The study demonstrates a new approach for non-contrast brain perfusion imaging.