Spin-echo Echo-planar Imaging Sequence Research Articles

Evaluating the Therapeutic Effect of Low-Intensity Transcranial Ultrasound on Traumatic Brain Injury With Diffusion Kurtosis Imaging.

Low-intensity transcranial ultrasound (LITUS) has a therapeutic effect on traumatic brain injury (TBI). Diffusion kurtosis imaging (DKI) might be able to evaluate the effect changes of injured brain microstructure. To evaluate the therapeutic effect of LITUS in a moderate TBI rat model with DKI parameters. Prospective case-control animal study. Forty-five rats were randomly divided into sham control, TBI, and LITUS treatment groups (n = 15). Single-shot spin echo echo-planar imaging and fast T2 WI sequences at 3.0T. DKI parameters were obtained on days 1, 7, 14, 21, 28, 35, and 42 after TBI. For the mean kurtosis (MK), axial kurtosis (Ka), and radial kurtosis (Kr) values, groups were compared using a two-way analysis of variance (ANOVA). LITUS inhibited TBI and caused MK values to increase significantly during the early stage (LITUS vs. TBI, day 7, adjusted P < 0.0001) and decrease during the late stage (LITUS vs. TBI, day 42, adjusted P = 0.0156) in the damaged cortex. In the thalamus, the MK value of the TBI group began to rise on day 7, with no change observed in the LITUS group. TBI increases Ka value during the early stage in the cortex and decreases during the late stage in the cortex and thalamus. LITUS inhibited these Ka changes (LITUS vs. TBI, day 7, adjusted P = 0.0014; LITUS vs. TBI, day 42, adjusted P = 0.0026 and 0.0478, respectively, for cortex and thalamus). The Kr value increased slightly during the early stage in the cortex (TBI vs. Sham, day 1, adjusted P = 0.0016). The DKI parameter, particularly the MK value, evaluates primary cortical injury as well as the secondary brain injury that could not be detected by conventional T2 WI. 1 Technical Efficacy Stage: 4 J. Magn. Reson. Imaging 2020;52:520-531.

Blood Oxygen Level-Dependent MRI of the Myocardium with Multiecho Gradient-Echo Spin-Echo Imaging.

Background Myocardial oxygenation imaging could help determine the presence of microvascular dysfunction associated with increased cardiovascular risk. However, it is challenging to depict the potentially small oxygenation alterations with current noninvasive cardiac MRI blood oxygen level-dependent (BOLD) techniques. Purpose To demonstrate the cardiac application of a gradient-echo spin-echo (GESE) echo-planar imaging sequence for dynamic and quantitative heartbeat-to-heartbeat BOLD MRI and evaluate the sequence in populations both healthy and with hypertension in combination with a breath hold-induced CO2 intervention. Materials and Methods GESE echo-planar imaging sequence was performed in 18 healthy participants and in eight prospectively recruited participants with hypertension on a 3.0-T MRI system. T2 and T2* maps were calculated per heartbeat with a four-parameter fitting technique. Septal regions of interests were used to determine T2 and T2* values per heartbeat and examined over the course of a breath hold to determine BOLD changes. T2 and T2* changes of healthy participants and participants with hypertension were compared by using a nonparametric Mann-Whitney test. Results GESE echo-planar imaging approach gave spatially stable T2 and T2* maps per heartbeat for healthy participants and participants with hypertension, with mean T2 values of 43 msec ± 5 (standard deviation) and 46 msec ± 9, respectively, and mean T2* values of 28 msec ± 5 and 22 msec ± 5, respectively. The healthy participants exhibited increasing T2 and T2* values over the course of a breath hold with a mean positive slope of 0.2 msec per heartbeat ± 0.1 for T2 and 0.2 msec per heartbeat ± 0.1 for T2*, whereas for participants with hypertension these dynamic T2 and T2* values had a mean negative slope of -0.2 msec per heartbeat ± 0.2 for T2 and -0.1 msec per heartbeat ± 0.2 for T2*. The difference in these mean slopes between healthy participants and participants with hypertension was significant for both T2 (P < .001) and T2* (P < .001). Conclusion Gradient-echo spin-echo echo-planar imaging sequence provided quantitative T2 and T2* maps per heartbeat and enabled dynamic heartbeat-to-heartbeat blood oxygen level-dependent (BOLD)-response imaging by analyzing changes in T2 and T2* over the time of a breath-hold intervention. This approach could identify differences in the BOLD response between healthy participants and participants with hypertension. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Friedrich in this issue.

Different Myocardial Perfusion Status in Acute Myocardial Infarction and Infarct-like Myocarditis: A Novel Intravoxel Incoherent Motion Diffusion-weighted Imaging based MRI Study

The following study evaluated the diagnostic value of myocardial perfusion in patients with acute myocardial infarction (AMI) and "infarct-like myocarditis" using Intravoxel Incoherent Motion-Diffusion Weighted Imaging (IVIM-DWI imaging). CMR data from 20 patients with suspected AMI, 20 patients with "infarct-like myocarditis" and 20 volunteers were retrospectively analyzed. IVIM-DWI data were acquired using multi-b value single-shot spin-echo echo-planar imaging sequence. IVIM-DWI data were generated according to the 16-segments AHA-model. Cine sequences covering left and right ventricle in short axis and three long axis were analyzed using a dedicated tissue-tracking algorithm. Overall, the AMI T2+ segments exhibited decreased apparent diffusion coefficient (ADC), ADCslow, ADC fast and f values (1.39 ± 0.23 μm2/ms, 1.36 ± 0.23 μm2/ms, 70.77 ± 7.04 μm2/ms, and 0.1243 ± 0.01, respectively) compared to infarct-like myocarditis T2+ (1.48 ± 0.11 μm2/ms, 1.44 ± 0.11 μm2/ms, 87.66 ± 12.50 μm2/ms, and 0.1411 ± 0.02, respectively) and normal controls (1.55 ± 0.07 μm2/ms, 1.52 ± 0.06 μm2/ms, 108.84 ± 4.06 μm2/ms, and 0.1599 ± 0.01, respectively) (all p < 0.05). In addition, AMI LGE+ segments showed significantly lower IVIM-DWI associated parameters (1.34 ± 0.21 μm2/ms, 1.31 ± 0.21 μm2/ms, 68.75 ± 6.33μm2/ms, and 0.1198 ± 0.01) compared to infarct-like myocarditis LGE+ (1.42 ± 0.06 μm2/ms, 1.38 ± 0.08 μm2/ms, 79.12 ± 5.70 μm2/ms, and 0.1313 ± 0.02) (p < 0.05). Moreover, left ventricular peak subendo and subepi radial, circumferential, and longitudinal strain were lower in AMI T2+ segments than in infarct-like myocarditis T2+ segments and normal controls (p < 0.05); AMI LGE+ segments exhibited the lowest strain in three orientations compared to other subgroups (p < 0.05). These findings prove that IVIM-DWI may be used as a reliable sequence for evaluation of different myocardial perfusion patterns in AMI and infarct-like myocarditis. AMI may exhibit lower myocardial perfusion status compared to infarct-like myocarditis due to different pathophysiological process.

Technical success rates and reliability of spin-echo echo-planar imaging (SE-EPI) MR elastography in patients with chronic liver disease or liver cirrhosis.

To determine the technical success rates of MR elastography (MRE) according to established gradient-recalled echo (GRE) and spin-echo echo-planar imaging (SE-EPI) sequences and to compare liver stiffness (LS) values between the sequences during expiratory and inspiratory phases in patients with chronic liver disease or liver cirrhosis. One hundred and eight patients who underwent MRE were included in this retrospective study. MRE was performed at 3 T based on both sequences during expiration as well as inspiration. Technical failure of MRE was determined if there was no pixel value with a confidence index higher than 95% and/or no apparent shear waves imaged. LS measurements were performed using free-drawing region of interest. To evaluate clinical factors related to the technical success rate of MRE, we assessed etiology of liver disease, ascites, body habitus, iron deposition, and liver morphology of patients. Statistical analysis was performed with the Wilcoxon test, Bland-Altman plot, independent t test, Mann-Whitney test, and McNemar test. The technical success rate of MRE in SE-EPI was significantly higher than that of GRE (98.1% vs. 80.7%, p < 0.0001). On the basis of univariate analysis, height, weight, and BMI were significantly associated with failure of MRE (p < 0.05). There was no significant difference in LS values between GRE and SE-EPI (2.82 kPa vs. 2.92 kPa (p > 0.05)). However, the LS values were significantly higher during inspiration than expiration with both GRE and SE-EPI (p < 0.0001). MRE in SE-EPI during expiratory breath-hold can be used as a reliable examination to evaluate liver fibrosis. • The technical success rate of MR elastography in spin-echo echo-planar imaging (SE-EPI) was significantly higher than that in gradient-recalled echo (GRE) during both the inspiratory and expiratory phases. • Liver stiffness values were significantly higher during inspiration than during expiration in both GRE and SE-EPI. • MR elastography in SE-EPI during expiratory breath-hold can be used as a reliable examination in patients with liver fibrosis.

Comparison of technical failure of MR elastography for measuring liver stiffness between gradient-recalled echo and spin-echo echo-planar imaging: A systematic review and meta-analysis.

Magnetic resonance elastography (MRE) using a gradient-recalled echo (GRE) or a recently available spin-echo echo-planar imaging (SE-EPI) sequence is a promising noninvasive method for measuring liver stiffness. However, it sometimes fails to measure stiffness values, thereby resulting in technical failures. To assess and compare technical failures of MRE for measuring liver stiffness between GRE and SE-EPI sequences. Systematic review and meta-analysis. Eight studies with both GRE and SE-EPI, 22 studies with only GRE, one study with only SE-EPI. Either 1.5 or 3T MRE using GRE and/or SE-EPI. Through an Ovid-MEDLINE and EMBASE database search, original articles investigating the proportion of MRE technical failures in the measurement of liver stiffness published up until October 2018 were screened and selected. The pooled proportions of technical failures under GRE and SE-EPI were calculated using random-effects meta-analysis of single proportions and inverse variance for calculating weights. Subgroup analyses were performed to explore the covariates affecting heterogeneity. Head-to-head comparisons of technical failure between the sequences were conducted with eight MRE studies using both GRE and SE-EPI. The pooled proportion of technical failure under GRE MRE was 5.8% (95% confidence interval [CI], 4.6-7.4%), and a subgroup analysis showed higher technical failure rates at 3T than at 1.5T. The pooled proportion of technical failure under SE-EPI MRE was 2.0% (95% CI, 1.3-3.4%), without significant differences (P = 0.38-0.89) being observed in the subgroup analyses. In the eight studies comparing the two sequences, failure was more frequently observed with GRE than with SE-EPI (9.4% vs. 1.9%; P < 0.01). MRE conducted with SE-EPI sequences showed a lower technical failure rate than GRE sequences. With GRE sequences, a magnetic field of 3T was associated with higher technical failure rates than was 1.5T. 1 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:1086-1102.

Diffusional kurtosis imaging for differentiation of additional suspicious lesions on preoperative breast MRI of patients with known breast cancer

PurposeTo investigate the potential of diffusional kurtosis imaging (DKI) and conventional diffusion-weighted imaging (DWI) in the evaluation of additional suspicious lesions at preoperative breast magnetic resonance imaging (MRI) in patients with breast cancer. Materials and methodsFifty-three additional suspicious lesions in 45 patients with breast cancer, which were detected on preoperative breast MRI, were examined with a 3-T MR system. DKI and DWI data were obtained using a spin-echo single-shot echo-planar imaging sequence with b-values of 0, 50, 600, 1000, and 3000 s/mm2. Histogram parameters (mean, standard deviation, minimum, maximum, 10th, 25th, 50th, 75th, 90th percentiles, kurtosis, skewness and entropy) of ADC from DWI and diffusivity (D), kurtosis (K) from DKI were calculated after postprocessing. Parameters were compared between benign vs. ductal carcinoma in situ (DCIS) vs. invasive breast lesions and diagnostic performances were evaluated by receiver operating characteristic (ROC) analysis. Correlation between the mean values of D and K was analyzed according to lesion type. ResultsMultiple histogram parameters of D (mean, 25th, 50th percentile, 75th percentile, and entropy) differed between benign and invasive breast lesions (all P < 0.005), but none differed between benign vs. DCIS. D-90th percentile differed between DCIS vs. invasive cancer (P = 0.040). K-10th percentile differed between benign vs. DCIS (P = 0.015). ADC-75th percentile differed between benign vs. invasive cancer and ADC-75th percentile, ADC-90th percentile differed between DCIS vs. invasive cancer, respectively (all P < 0.005). ROC curve analysis showed high specificity for discrimination between benign and invasive cancer. D-mean and K-mean showed strong correlation in benign (rs = −0.813) and invasive lesions (rs = −0.853), but no significant correlation in DCIS. ConclusionDKI may aid in the differentiation of additional suspicious lesions at preoperative breast MRI. Both ADC and DKI may have lower potential in differentiating DCIS from benign lesions.

Abnormal cerebral microstructures revealed by diffusion kurtosis imaging in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease in which cerebral structural impairment is a consistent feature. To investigate cerebral microstructural changes in ALS using diffusion kurtosis imaging (DKI) for the first time. Prospective. Eighteen ALS patients and 20 healthy controls. DKI images were obtained by a spin-echo echo-planar imaging sequence on a 3T MRI scanner, with three b-values (0, 1000, and 2000 s/mm2 ) and 64 diffusion encoding directions. The revised ALS Functional Rating Scale (ALSFRS-R) was administered to assess disease severity, and the symptom duration and disease progression rate were also recorded. Voxel-based analysis was applied to examine the alteration of DKI metrics (ie, mean kurtosis metrics [MK], axial kurtosis [AK], and radial kurtosis [RK]) and the conventional diffusion metrics (ie, fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity). Student's t-test, chi-square test, and Pearson correlation analysis. ALS patients showed MK reductions in gray matter areas, including the bilateral precentral gyrus, bilateral paracentral lobule, and left anterior cingulate gyrus; they also showed decreased MK values in white matter (WM) in the bilateral precentral gyrus, bilateral corona radiata, bilateral middle corpus callosum, left occipital lobe, and right superior parietal lobule. The spatial distribution of the regions with reduced RK was similar to those with decreased MK. No significant AK difference was found between groups. The correlation analysis revealed significant associations between DKI metrics and clinical assessments such as ALSFRS-R score and disease duration. Additionally, several WM regions showed between-group differences in conventional diffusion metrics; but the spatial extent was smaller than that with reduced DKI metrics. The reduction in DKI metrics indicates decreased microstructural complexity in ALS, involving both motor-related areas and extramotor regions. DKI metrics can serve as potential biomarkers for assessing disease severity. 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;51:554-562.

Magnetic resonance elastography of the lungs: A repeatability and reproducibility study.

Lung diseases are one of the leading causes of death worldwide, from which four million people die annually. Lung diseases are associated with changes in the mechanical properties of the lungs. Several studies have shown the feasibility of using magnetic resonance elastography (MRE) to quantify the lungs' shear stiffness. The aim of this study is to investigate the reproducibility and repeatability of lung MRE, and its shear stiffness measurements, obtained using a modified spin echo-echo planar imaging (SE-EPI) MRE sequence. In this study, 21 healthy volunteers were scanned twice by repositioning the volunteers to image right lung both at residual volume (RV) and total lung capacity (TLC) to assess the reproducibility of lung shear stiffness measurements. Additionally, 19 out of the 21 volunteers were scanned immediately without moving the volunteers to test the repeatability of the modified SE-EPI MRE sequence. A paired t-test was performed to determine the significant difference between stiffness measurements obtained at RV and TLC. Concordance correlation and Bland-Altman's analysis were performed to determine the reproducibility and repeatability of the SE-EPI MRE-derived shear stiffness measurements. The SE-EPI MRE sequence is highly repeatable with a concordance correlation coefficient (CCC) of 0.95 at RV and 0.96 at TLC. Similarly, the stiffness measurements obtained across all volunteers were highly reproducible with a CCC of 0.95 at RV and 0.92 at TLC. The mean shear stiffness of the lung at RV was 0.93±0.22kPa and at TLC was 1.41±0.41kPa. TLC showed a significantly higher mean shear stiffness (P=0.0004) compared with RV. Lung MRE stiffness measurements obtained using the SE-EPI sequence were reproducible and repeatable, both at RV and TLC. Lung shear stiffness changes across respiratory cycle with significantly higher stiffness at TLC than RV.

Magnetic resonance elastography SE-EPI vs GRE sequences at 3T in a pediatric population with liver disease.

The goal of our study is to compare hepatic stiffness measures using gradient-recalled echo (GRE) versus spin-echo echo planar imaging (SE-EPI)-based MR Elastography (MRE) at 3T used to measure hepatic stiffness in a patients with suspected liver diseases. This retrospective study included 52 patients with liver disease who underwent a 3T MRE exam including both an investigational SE-EPI-based technique and a product GRE-based technique. Regions of interest (ROI) were placed on the elastograms to measure elastography-derived liver stiffness as well as the area included within the ROIs. The mean liver stiffness values and area of ROIs were compared. The mean liver stiffness was 3.72 kilopascal (kPa) ± 1.29 using GRE MRE and 3.78kPa ± 1.13 using SE-EPI MRE. Measurement of liver stiffness showed excellent agreement between the two pulse sequences with a mean bias of - 0.1kPa (range - 1.8 to 1.7kPa) between sequences. The mean measurable ROI area was higher with SE-EPI (313.8cm2 ± 213.8) than with the GRE technique (208.6cm2 ± 114.8), and the difference was statistically significant (P < 0.05). Our data shows excellent agreement of measured liver stiffness between GRE and SE-EPI-based sequences at 3T. Our results show the advantage of a SE-EPI MRE sequence in terms of image quality, ROI size and acquisition time with equivalent liver stiffness measurements as compared to GRE-MRE sequence.

Diffusion tensor imaging parameters in differentiation recurrent breast cancer from post-operative changes in patients with breast-conserving surgery

Aim of the workTo investigate mean diffusivity (MD) and fractional anisotropy (FA) measured by diffusion tensor imaging (DTI) as complementary tools to differentiate recurrent breast cancer from post-operative changes in patients with breast-conserving surgery (BCS). Patients and MethodsProspective study was conducted upon 30 patients with BCS that underwent DTI and dynamic contrast MR imaging. DTI was performed using an axial two-dimensional spin-echo echo-planar imaging sequence. The MD and FA of the lesions were calculated by 2 observers. A single pixel seed isotropic region of interest was placed in the solid part of the tumor on the axial color FA map guided by an enhanced part of the tumor. The final diagnosis was done by biopsy for all patients. ResultsThe pathological examination proved to be recurrent breast cancer (n = 13) and post-operative changes (n = 17). Recurrent breast cancer had significantly lower MD (P = 0.001, 0.001) and higher FA (P = 0.003, 0.02) than in post-operative changes for both observers respectively. At ROC curve analysis of MD, the AUC was 0.86 and 0.85 by both observers. The threshed MD was (0.86, 0.85 × 10−3 mm2/s) used for differentiation between entities revealed sensitivity (76.9%, 92.3%), specificity (82.4%, 64.7%) and accuracy (80%, 76.7%) of both observers respectively. At ROC curve analysis of FA, the AUC was 0.82 and 0.75 by both observers. The threshold FA (0.82, 0.75) was used for differentiation between entities revealed sensitivity (92.3%, 76.9%), specificity (70.6%, 70.6%) and accuracy of (80.0%, 73.3%) of both observers respectively. There was a strong positive correlation of MD (r = 0.86) and FA (r = 0.73) of both observers. Combined analysis of FA and MD used for differentiation between entities had AUC (0.90, 0.88) revealed sensitivity (92.3%, 92.3%), specificity (82.4%, 70.6%) and accuracy of (86.7%, 80.0%) for both observers respectively. ConclusionsCombined analysis of MD and FA of DTI may play an important role as a non-invasive method for differentiation recurrent breast cancer from post-operative changes in patients with BCS.

Improvement of Reliability of Diffusion Tensor Metrics in Thigh Skeletal Muscles

ObjectiveQuantitative diffusion tensor imaging (DTI) of skeletal muscles is challenging due to the bias in DTI metrics, such as fractional anisotropy (FA) and mean diffusivity (MD), related to insufficient signal-to-noise ratio (SNR). This study compares the bias of DTI metrics in skeletal muscles via pixel-based and region-of-interest (ROI)-based analysis. MethodsDTI of the thigh muscles was conducted on a 3.0-T system in N = 11 volunteers using a fat-suppressed single-shot spin-echo echo planar imaging (SS SE-EPI) sequence with eight repetitions (number of signal averages (NSA) = 4 or 8 for each repeat). The SNR was calculated for different NSAs and estimated for the composite images combining all data (effective NSA = 48) as standard reference. The bias of MD and FA derived by pixel-based and ROI-based quantification were compared at different NSAs. An “intra-ROI diffusion direction dispersion angle (IRDDDA)” was calculated to assess the uniformity of diffusion within the ROI. ResultsUsing our standard reference image with NSA = 48, the ROI-based and pixel-based measurements agreed for FA and MD. Larger disagreements were observed for the pixel-based quantification at NSA = 4. MD was less sensitive than FA to the noise level. The IRDDDA decreased with higher NSA. At NSA = 4, ROI-based FA showed a lower average bias (0.9% vs. 37.4%) and narrower 95% limits of agreement compared to the pixel-based method. ConclusionThe ROI-based estimation of FA is less prone to bias than the pixel-based estimations when SNR is low. The IRDDDA can be applied as a quantitative quality measure to assess reliability of ROI-based DTI metrics.

Optimizing diffusion-weighted magnetic resonance imaging for evaluation of lung tumors: A comparison of respiratory triggered and free breathing techniques

PurposeThe aim of this study was to compare respiratory-triggered (RT) and free breathing (FB) diffusion weighted imaging (DWI) techniques regarding apparent diffusion coefficient (ADC) measurements and repeatability in non-squamous non-small cell lung cancer (NSCLC) measuring the total tumor volume. Material and MethodsA total of 57 magnetic resonance imaging (MRI) examinations were analyzed. DWI was obtained by a single-shot spin-echo echo-planar imaging sequence, and for each MRI examination 2 consecutive RT and 2 consecutive FB DWI sequences were performed. Two radiologists independently read the images and made measurements. For each tumor the mean ADC value of the whole tumor volume was calculated. The difference in mean ADCs between FB and RT DWI was evaluated using the paired-sample t-test. The repeatability of ADC measurements related to imaging method was evaluated by intra class correlations (ICC) for each of the FB and RT DWI pairs. ResultsThere were no significant differences in mean ADCs between FB and RT (Reader 1 p = 0.346, Reader 2 p = 0.583). The overall repeatability of ADC measurement was good for both acquisition methods, with ICCs > 0.9. Subgroup analysis showed somewhat poorer repeatability in small tumors (50 ml or less) and tumors in the lower lung zones for the RT acquisition, with ICC as low as 0.72. ConclusionsNo difference in ADC measurement or repeatability between FB and RT DWI in whole lesion ADC measurements of adenocarcinomas in the lung was demonstrated. The results imply that in this setting the FB acquisition method is accurate and possibly more robust than the RT acquisition technique.

Role of the combination of FA and T2* parameters as a new diagnostic method in therapeutic evaluation of parkinson's disease.

Simple diffusion delivery (SDD) has attained good effects with only tiny amounts of drugs. Fractional anisotropy (FA) and relaxation time T2* that indicate the integrity of fiber tracts and iron concentration within brain tissue were used to evaluate the therapeutic effect of SDD. To evaluate therapeutic effect of SDD in the Parkinson's disease (PD) rat model with FA and T2* parameters. Prospective case-control animal study. Thirty-two male Sprague Dawley rats (eight normal, eight PD, eight SDD, and eight subcutaneous injection rats). Single-shot spin echo echo-planar imaging and fast low-angle shot T2 WI sequences at 3.0T. Parameters of FA and T2* on the treated side of the substantia nigra were measured to evaluate the therapeutic effect of SDD in a PD rat model. The effects of time on FA and T2* values were analyzed by repeated measurement tests. A one-way analysis of variance was conducted, followed by individual comparisons of the mean FA and T2* values at different timepoints. The FA values on the treated side of the substantia nigra in the SDD treatment group and subcutaneous injection treatment group were significantly higher at week 1 and lower at week 6 than that of the PD control group (SDD vs. PD, week 1, adjusted P = 0.012; subcutaneous vs. PD, week 1, adjusted P < 0.001; SDD vs. PD, week 6, adjusted P = 0.004; subcutaneous vs. PD, week 6, adjusted P = 0.024). The T2* parameter in the SDD treatment group and subcutaneous injection treatment group was significantly higher than that in the PD control group at week 6 (SDD vs. PD, adjusted P = 0.032; subcutaneous vs. PD, adjusted P < 0.001). The combination of FA and T2* parameters can potentially serve as a new effective evaluation method of the therapeutic effect of SDD. 1 Technical Efficacy: Stage 4 J. Magn. Reson. Imaging 2017.

Comparison of spin-echo echoplanar imaging and gradient recalled echo-based MR elastography at 3 Tesla with and without gadoxetic acid administration

To compare spin-echo echoplanar imaging (SE-EPI) and gradient recalled echo (GRE) MR elastography (MRE) at 3 T with and without gadoxetic acid administration. We included 84 patients who underwent MRE before and after gadoxetic acid administration, each time using SE-EPI and GRE sequences. Diagnostic performance for predicting clinical liver cirrhosis and high-risk oesophageal varices was assessed using the area under the receiver-operating characteristic curve (AUC). The relationships between T2* and success of MRE, and correlations of liver stiffness (LS) values between the two sequences or before and after gadoxetic acid administration, were investigated. SE-EPI-MRE resulted in a significantly lower failure rate than GRE-MRE (1.19% vs. 10.71%, P = 0.018). Increased T2* was related to higher probability of successful LS measurement (odds ratio, 1.426; P = 0.004). The AUC of SE-EPI-MRE was comparable to that of GRE-MRE for the detection of clinical liver cirrhosis (0.938 vs. 0.948, P = 0.235) and high-risk oesophageal varices (0.839 vs. 0.752, P = 0.354). LS values were not significantly different before and after gadoxetic acid administration. SE-EPI-MRE can substitute for GRE-MRE for the detection of clinical liver cirrhosis and high-risk oesophageal varices. SE-EPI-MRE is particularly useful in patients with iron deposition, with lower failure rates than GRE-MRE. • LS values are comparable between SE-EPI-MRE and GRE-MRE. • Administration of gadoxetic acid does not influence LS measurement. • The failure rate of SE-EPI-MRE is significantly lower than that of GRE-MRE.

3-T Magnetic Resonance Diffusion-Weighted Imaging (DWI) for Characterization of Hepatic Masses

Objective: To evaluate the role of DWI and ADC in differentiating benign from malignant hepaticmasses Materials and methods: Forty-one patients with fifty-two focal hepatic masses were included in our study. MRI was done using coronal T2-weighted single-shot turbo spin-echo, breath hold axial 3-D gradient-echo, breath hold 2- D gradient-echo in and out-of-phase, respiratory-triggered axial turbo spin-echo T2 sequence with fat saturation, followed by free breathing Diffusion-weighted MR imaging using a single-shot spin-echo echo planar imaging sequence and finally triphasic -MRI. Results: Forty-one patients (Fifty-two lesions) were included in our study. Twenty-three lesions were benign; eight of them were cysts (mean ADC values of 3.15 ± 0.34 × 10-3 mm2/s) and fifteen lesions were hemangiomas (mean ADC values of 2.10 ± 0.25 × 10-3 mm2/s). Twenty-nine lesions were malignant; twelve HCC lesions (mean ADC values of 1.10 ± 0.32 × 10-3 mm2/s) and seventeen masses were metastasis (mean ADC values of 0.96 ± 0.23 × 10-3 mm2/s). Sensitivity and specificity of DWI in differentiating malignant from benign hepatic masses were 96.6% and 95.7% respectively. Conclusion: DWI is an easy technique to obtain and to be evaluated. ADC values can differentiate benign from malignant liver masses with high sensitivity and specificity.

Analysis of the diffusion tensor imaging parameters of a normal cervical spinal cord in a healthy population

Background: Diffusion tensor imaging (DTI) shows great advantage in the diagnosis of brain diseases, including cervical spinal cord (CSC) disease. This study aims to obtain the normal values of the DTI parameters for a healthy population and to establish a baseline for CSC disease diagnosis using DTI.Methods: A total of 36 healthy adults were subjected to magnetic resonance imaging (MRI) for the entire CSC using the Siemens 3.0 T MR System. Sagittal DTI acquisition was carried out with a single-shot spin-echo echo-planar imaging (EPI) sequence along 12 non-collinear directions. Fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values were determined at different cervical levels using a region of interest (ROI) method, following which they were correlated with parameters, like age and sex. Further, diffusion tensor tracking (DTT) was carried out to reconstruct the white matter fiber bundles of the CSC.Results: The full and complete fiber bundle structure of a normal CSC was confirmed in both the T2-weighted and DTI images. The FA and ADC values were significantly negatively correlated with each other and showed strongly negative and positive correlations with age, respectively, but not with sex. Additionally, there was no significant difference between the FA and the ADC values at different cervical levels.Conclusion: The DTI technique can act as an important supplement to the conventional MRI technique for CSC observation. Moreover, the FA and ADC values can be used as sensitive parameters in the DTI study on the CSC by taking the effects of age into consideration.

Increased Cortical Cerebral Blood Flow in Asymptomatic Human Immunodeficiency Virus-Infected Subjects

Human immunodeficiency virus (HIV)-infected individuals are at high risk for ischemic stroke. To investigate the physiological basis for this risk, we used magnetic resonance imaging (MRI) to measure oxygen extraction fraction (OEF) and cerebral blood flow (CBF) in treatment-naive asymptomatic HIV-infected subjects and controls. In treatment-naive asymptomatic HIV-infected subjects and age-, gender-, and race-matched controls, OEF was measured by MRI asymmetric spin-echo echo-planar imaging sequences and CBF was measured by MRI pseudocontinuous arterial spin labeling. Twenty-six treatment-naive HIV-infected subjects and 27 age-, gender-, race-matched controls participated. Whole-brain, gray matter (GM), and white matter OEF were not different between the groups (all P > .70). Unexpectedly, HIV-infected subjects had significantly higher CBF in cortical GM (72.9 ± 16.2 mL/100 g/min versus 63.9 ± 9.9 mL/100 g/min; P = .01) but not in subcortical GM (P = .25). The observed increase in cortical GM CBF in treatment-naive HIV-infected subjects is unexpected, contrary to CBF decreases reported in HIV-infected subjects on treatment, and may represent an initial increase in metabolic activity due to an HIV-mediated inflammation.

Prostate cancer: correlation of intravoxel incoherent motion MR parameters with Gleason score

PurposeTo evaluate the potential of intravoxel incoherent motion (IVIM) imaging to predict histological prognostic parameters by investigating whether IVIM parameters correlate with Gleason score. Materials and methodsThe institutional review board approved this retrospective study, and informed consent was waived. A total of 41 patients with histologically proven prostate cancer who underwent prostate MRI using a 3T MRI machine were included. For eight diffusion-weighted imaging b-values (0, 10, 20, 50, 100, 200, 500, and 800s/mm2), a spin-echo echo-planar imaging sequence was performed. D, f, D⁎, and ADCfit values were compared among three groups of patients with prostate cancer: Gleason score 6 (n=9), 7 (n=16), or 8 or higher (n=16). Receiver operating characteristic (ROC) curves were generated for D, f, D⁎, and ADCfit to assess the ability of each parameter to distinguish cancers with low Gleason scores from cancers with intermediate or high Gleason scores. ResultsPearson's coefficient analysis revealed significant negative correlations between Gleason score and ADCfit (r=−0.490, P=.001) and Gleason score and D values (r=−0.514, P=.001). Gleason score was poorly correlated with f (r=0.168, P=.292) and D⁎ values (r=−0.108, P=.500). The ADCfit and D values of prostate cancers with Gleason scores 7 or ≥8 were significantly lower than values for prostate cancers with Gleason score 6 (P<.05). ROC curves were constructed to assess the ability of IVIM parameters to discriminate prostate cancers with Gleason score 6 from cancers with Gleason scores 7 or ≥8. Areas under the curve were 0.671 to 0.974. ADCfit and D yielded the highest Az value (0.960–0.956), whereas f yielded the lowest Az value (0.633). ConclusionsThe pure molecular diffusion parameter, D, was the IVIM parameter that best discriminated prostate cancers with low Gleason scores from prostate cancers with intermediate or high Gleason scores.

In vivo free-breathing DTI &amp; IVIM of the whole human heart using a real-time slice-followed SE-EPI navigator-based sequence: a reproducibility study in healthy volunteers

In this study, we proposed an efficient free-breathing strategy for rapid and improved cardiac diffusion-weighted imaging (DWI) acquisition using a single-shot spin-echo echo planar imaging (SE-EPI) sequence. Methods: A real-time slice-following technique during free-breathing was combined with a sliding acquisition-window strategy prior Principal Component Analysis temporal Maximum Intensity Projection (PCAtMIP) postprocessing of in-plane co-registered diffusion-weighted images. This methodology was applied to 10 volunteers to quantify the performance of the motion correction technique and the reproducibility of diffusion parameters. Results: The slice-following technique offers a powerful head–foot respiratory motion management solution for SE-EPI cDWI with the advantage of a 100% duty cycle scanning efficiency. The level of co-registration was further improved using nonrigid motion corrections and was evaluated with a co-registration index. Vascular fraction f and the diffusion coefficients D and D* were determined to be 0.122 ± 0.013, 1.41 ± 0.09 × 10−3 mm2/s and 43.6 ± 9.2 × 10−3 mm2/s, respectively. From the multidirectional dataset, the measured mean diffusivity was 1.72 ± 0.09 × 10−3 mm2/s and the fractional anisotropy was 0.36 ± 0.02. Conclusion: The slice-following DWI SE-EPI sequence is a promising solution for clinical implementation, offering a robust improved workflow for further evaluation of DWI in cardiology. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

Diffusion-weighted MR neurography of the brachial and lumbosacral plexus: 3.0 T versus 1.5 T imaging

PurposeTo compare intraindividually the nerve conspicuity of the brachial and lumbosacral plexus on diffusion-weighted (DW) MR neurography (MRN) at two different field strengths. Materials and methods16 healthy volunteers were investigated at 3.0T and 1.5T applying optimized variants of a DW spin-echo echo-planar imaging sequence with short TI inversion recovery fat suppression. Full-volume (FV) and curved sub-volume (CSV) maximum intensity projection (MIP) images were reconstructed and nerve conspicuity was visually assessed. Moreover, visible length and sharpness of the nerves were quantitatively analyzed. ResultsOn FV MIP images, nerve conspicuity at 3.0T compared to 1.5T was worse for brachial plexus (P=0.00228), but better for lumbosacral plexus (P=0.00666). On CSV MIP images, nerve conspicuity did not differ significantly for brachial plexus, but was better at 3.0T for lumbosacral plexus (P=0.00091). The visible length of the analyzed nerves did not differ significantly with the exception of some lumbosacral nerves, which were significantly longer at 3.0T. The sharpness of all investigated nerves was significantly higher at 3.0T by about 40–60% for cervical and 97–169% for lumbosacral nerves. ConclusionDW MRN imaging at 3.0T compared to 1.5T is superior for lumbosacral plexus, but not for brachial plexus.