Evaluation of a single-breath-hold radial turbo-spin-echo sequence for T2 mapping of the liver at 3T

Objectives T2 mapping of the liver is a potential diagnostic tool, but conventional techniques are difficult to perform in clinical practice due to long scan time. We aimed to evaluate the accuracy of a prototype radial turbo-spin-echo (rTSE) sequence, optimized for multi-slice T2 mapping in the abdomen during one breath-hold at 3 T. Methods A multi-sample (fat: 0–35%) agarose phantom doped with MnCl2 and 80 subjects (73 patients undergoing abdomen MR examination and 7 healthy volunteers) were investigated. A radial turbo-spin-echo (rTSE) sequence with and without fat suppression, a Cartesian turbo-spin-echo (Cart-TSE) sequence, and a single-voxel multi-echo STEAM spectroscopy (HISTO) were performed in phantom, and fat-suppressed rTSE and HISTO sequences were performed in in vivo measurements. Two approaches were used to sample T2 values: manually selected circular ROIs and whole liver analysis with Gaussian mixture models (GMM). Results The rTSE-T2s values exhibited a strong correlation with Cart-TSE-T2s (R2 = 0.988) and with HISTO-T2s of water (R2 = 0.972) in phantom with an offset between rTSE and Cart-TSE maps (mean difference = 3.17 ± 1.18 ms). The application of fat suppression decreased T2 values, and the effect was directly proportional to the amount of fat. Measurements in patients yielded a linear relationship between rTSE- and HISTO-T2s (R2 = 0.546 and R2 = 0.580 for ROI and GMM, respectively). Conclusion The fat-suppressed rTSE sequence allows for fast and accurate determination of T2 values of the liver, and appears to be suitable for further large cohort studies. Key Points •Radial turbo-spin-echo T2 mapping performs comparably to Cartesian TSE-T2 mapping, but an offset in values is observed in phantom measurements. •Fat-suppressed radial turbo-spin-echo T2 mapping is consistent with T2 of water as assessed by MRS in phantom measurements. •Fat-suppressed radial turbo-spin-echo sequence allows fast T2 mapping of the liver in a single breath-hold and is correlated with MRS-based T2 of water.

A New Modified MR Dual Precision Positioning of Thin-Slice Oblique Sagittal Fat Suppression Proton Density Weighted Imaging: Its Diagnostic Accuracy in Anterior Cruciate Ligament Injury and its Grades

Purpose To evaluate the diagnostic accuracy of a new modified MR dual precision positioning of thin-slice oblique sagittal fat suppression proton density-weighted imaging (DPP-TSO-Sag-FS-PDWI) sequence in detecting ACL injuries and its grades compared to standard sequences using arthroscopy as the standard reference.Materials and Methods 42 patients enrolled in this retrospective study received the 1.5-T MRI with standard sequences and the new modified DPP-TSO-Sag-FS-PDWI sequence, and their arthroscopy results was recorded. The Mc Nemer-Bowker and weighted Kappa was performed to compare the consistency of MRI diagnosis with arthroscopic results. Finally, the diagnostic accuracy was calculated based on the true positive, true negative, false negative and false positive values.Results The diagnostic consistency of the DPP-TSO-Sag-FS-PDWI were higher than standard sequences for both reader 1 (K = 0.876 vs. 0.620) and reader 2 (K = 0.833 vs. 0.683) with good diagnostic repeatability (K = 0.794 vs. 0.598). Furthermore, the DPP-TSO-Sag-FS-PDWI can classify and diagnose three grades of ACL injury [the sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value were more than 84%], especially for grade II injury as the PPV was superior for reader 1 (92.3% vs. 53.9%) and reader 2 (84.6% vs. 69.2%).Conclusion The new modified DPP-TSO-Sag-FS-PDWI sequence can display the ACL injury on one or continuous levels by maximizing the acquisition of complete ligament shape and true anatomical images, and excluding the influence of anatomical differences between individuals. It can improve the diagnostic accuracy with good repeatability and classify three grades of the ACL injury.

Free-breathing high resolution modified Dixon steady-state angiography with compressed sensing for the assessment of the thoracic vasculature in pediatric patients with congenital heart disease

Background Cardiovascular magnetic resonance angiography (CMRA) is a non-invasive imaging modality of choice in pediatric patients with congenital heart disease (CHD). This study was aimed to evaluate the diagnostic utility of a respiratory- and electrocardiogram-gated steady-state CMRA with modified Dixon (mDixon) fat suppression technique and compressed sensing in comparison to standard first-pass CMRA in pediatric patients with CHD at 3 T. Methods In this retrospective single center study, pediatric CHD patients who underwent CMR with first-pass CMRA followed by mDixon steady-state CMRA at 3 T were analyzed. Image quality using a Likert scale from 5 (excellent) to 1 (non-diagnostic) and quality of fat suppression were assessed in consensus by two readers. Blood-to-tissue contrast and quantitative measurements of the thoracic vasculature were assessed separately by two readers. CMRA images were reevaluated by two readers for additional findings, which could be identified only on either one of the CMRA types. Paired Student t test, Wilcoxon test, and intraclass correlation coefficients (ICCs) were used for statistical analysis. Results 32 patients with CHD (3.3 ± 1.7 years, 13 female) were included. Overall image quality of steady-state mDixon CMRA was higher compared to first-pass CMRA (4.5 ± 0.5 vs. 3.3 ± 0.5; P < 0.001). Blood-to-tissue contrast ratio of steady-state mDixon CMRA was comparable to first-pass CMRA (7.85 ± 4.75 vs. 6.35 ± 2.23; P = 0.133). Fat suppression of steady-state mDixon CMRA was perfect in 30/32 (94%) cases. Vessel diameters were greater in first-pass CMRA compared to steady-state mDixon CMRA with the greatest differences at the level of pulmonary arteries and veins (e.g., right pulmonary artery for reader 1: 10.4 ± 2.4 vs. 9.9 ± 2.3 mm, P < 0.001). Interobserver agreement was higher for steady-state mDixon CMRA for all measurements compared to first-pass CMRA (ICCs > 0.92). In 9/32 (28%) patients, 10 additional findings were identified on mDixon steady-state CMRA (e.g., partial anomalous venous return, abnormalities of coronary arteries, subclavian artery stenosis), which were not depicted using first-pass CMRA. Conclusions Steady-state mDixon CMRA offers a robust fat suppression, a high image quality, and diagnostic utility for the assessment of the thoracic vasculature in pediatric CHD patients.

Reducing SAR in 7T brain fMRI by circumventing fat suppression while removing the lipid signal through a parallel acquisition approach

Ultra-high-field functional magnetic resonance imaging (fMRI) offers a way to new insights while increasing the spatial and temporal resolution. However, a crucial concern in 7T human MRI is the increase in power deposition, supervised through the specific absorption rate (SAR). The SAR limitation can restrict the brain coverage or the minimal repetition time of fMRI experiments. In the majority of today’s studies fMRI relies on the well-known gradient-echo echo-planar imaging (GRE-EPI) sequence, which offers ultrafast acquisition. Commonly, the GRE-EPI sequence comprises two pulses: fat suppression and excitation. This work provides the means for a significant reduction in the SAR by circumventing the fat-suppression pulse. Without this fat-suppression, however, lipid signal can result in artifacts due to the chemical shift between the lipid and water signals. Our approach exploits a reconstruction similar to the simultaneous-multi-slice method to separate the lipid and water images, thus avoiding undesired lipid artifacts in brain images. The lipid-water separation is based on the known spatial shift of the lipid signal, which can be detected by the multi-channel coils sensitivity profiles. Our study shows robust human imaging, offering greater flexibility to reduce the SAR, shorten the repetition time or increase the volume coverage with substantial benefit for brain functional studies.

Variation of inversion delay for wrist joint MR imaging with SPAIR technique: which ID is optimal?

Background: The current fat suppression technique in magnetic resonance imaging (MRI) significantly diagnoses abnormalities in musculoskeletal disorders. The spectral attenuated inversion recovery (SPAIR) fat suppression (FS) technique had an inversion delay (ID) parameter that allows choosing between full or partial FS. This was the first research related to the optimal setting of the ID time variation in the SPAIR technique on T2-weighted MRI wrist joint images.Objectives: This study aims to find out anatomical information with the most optimal ID value of the MRI wrist joint image T2 turbo spin-echo (TSE) FS SPAIR coronal slice sequence.Method: This study was a pre-experimental post-test only. Scanning MR wrist joint 16 volunteers took data with the qualitative analysis used three radiologists (visual grading) with statistical data analysis.Results: Image information of the MRI wrist joint T2 TSE FS SPAIR coronal slices sequence showed differences in the variation of ID (p<0.001), where the ID of 85 ms produced the most optimal image information.Conclusion: MRI image of the wrist joint of the T2 TSE FS SPAIR coronal slices sequence the most optimal with an ID variation of 85 ms compared to ID 70 ms and 100 ms.

Lipoma of the corpus callosum: Fat in the brain

Intracranial lipomas are very rare, slow-growing, and benign tumors usually asymptomatic but occasionally associated with symptoms like a seizure. This rare occurrence is usually diagnosed incidentally and magnetic resonance imaging is the choice of investigation and diagnosis can be confirmed with fat suppression sequences. Management of corpus callosal lipoma is mainly conservative management with surgery not indicated due to the location and its peripheral structures. Managing seizure is the mainstay of the treatment. We present a case of incidentally diagnosed tubulonodular corpus callosal lipoma after having an event of a fall injury.

Radiomics-Based Distinction of s-HCC and Precancerous Lesion Based on Precontrast MRI

Background: To assess the feasibility of radiomics based on precontrast MRI for the distinguish of s-HCC and pre-HCC.Method: We retrospectively analyzed 146 nodules from 78 patients, with pathological confirmed. Each nodule was segment on precontrast MRI sequence(TIWI and fat-suppression T2WI), retrospectively. 1223radiomics features were extracted and the optimal 10 features were selected by LASSO to establish the logistic regression radiomics model. Result: The AUC, sensitivity and specificity of the training group and test group were 0.757 (95% CI 0.638 -0.853), 83.02% , 66.67% and 0.789 (95% CI 0.643-0.895), 88.89% and 80.00%, respectively. The AUC, sensitivity and specificity of the training group and test group were 0.903 (95% CI 0.807-0.962), 86.79% , 86.67% and 0.778 (95% CI 0.632-0.887), 75.00%, 80.00%, respectively. Delong test has proved that, the diagnositic performances of radiomics model based on T2WI were higher than that of radiomics model based on T1WI (p = 0.0379).Conclusion: Radiomics model can classify s-HCC and pre-HCC based on precontrast MRI. And may serve as an adjunct tool for accurate diagnosis of s-HCC.

Differences between 3D isovoxel fat suppression VIBE MRI and CT models of proximal femur osseous anatomy: A preliminary study for bone tumor resection planning

Purpose To evaluate the osseous anatomy of the proximal femur extracted from a 3D-MRI volumetric interpolated breath-hold (VIBE) sequence using either a Dixon or water excitation (WE) fat suppression method, and to measure the overall difference using CT as a reference standard. Material and methods This retrospective study reviewed imaging of adult patients with hip pain who underwent 3D hip MRI and CT. A semi-automatically segmented CT model served as the reference standard, and MRI segmentation was performed manually for each unilateral hip joint. The differences between Dixon-VIBE-3D-MRI vs. CT, and WE-VIBE-3D-MRI vs. CT, were measured. Equivalence tests between Dixon-VIBE and WE-VIBE models were performed with a threshold of 0.1 mm. Bland–Altman plots and Lin’s concordance-correlation coefficient were used to analyze the agreement between WE and Dixon sequences. Subgroup analyses were performed for the femoral head/neck, intertrochanteric, and femoral shaft areas. Results The mean and maximum differences between Dixon-VIBE-3D-MRI vs. CT were 0.2917 and 3.4908 mm, respectively, whereas for WE-VIBE-3D-MRI vs. CT they were 0.3162 and 3.1599 mm. The mean differences of the WE and Dixon methods were equivalent (P = 0.0292). However, the maximum difference was not equivalent between the two methods and it was higher in WE method. Lin’s concordance-correlation coefficient showed poor agreement between Dixon and WE methods. The mean differences between the CT and 3D-MRI models were significantly higher in the femoral shaft area (P = 0.0004 for WE and P = 0.0015 for Dixon) than in the other areas. The maximum difference was greatest in the intertrochanteric area for both techniques. Conclusion The difference between 3D-MR and CT models were acceptable with a maximal difference below 3.5mm. WE and Dixon fat suppression methods were equivalent. The mean difference was highest at the femoral shaft area, which was off-center from the magnetization field.