7-T clinical MRI of the shoulder in patients with suspected lesions of the rotator cuff.

BACKGROUND: To evaluate feasibility and diagnostic performance of clinical 7-T magnetic resonance imaging (MRI) of the shoulder. METHODS: Eight patients with suspected lesions of the rotator cuff underwent 7-T MRI before arthroscopy. Image quality was scored for artifacts, B1+ inhomogeneities, and assessability of anatomical structures. A structured radiological report was compared to arthroscopy. In four patients, a visual comparison with pre-existing 1.5-T examinations was performed. RESULTS: Regarding image quality, the majority of the sequences reached values above the middle of each scoring scale. Fat-saturated proton density sequences showed least artifacts and best structure assessability. The most homogenous B1+ field was reached with gradient-echo sequences. Arthroscopy did not confirm tendinopathy/partial tear of supraspinatus in 5/8 patients, of subscapularis in 5/6, and of infraspinatus in one patient; only a partial lesion of the subscapularis tendon was missed. Pathologic findings of long bicipital tendon, acromioclavicular joint, glenohumeral cartilage, labrum, and subacromial subdeltoideal bursa were mainly confirmed; exceptions were one lesion of the long bicipital tendon, one subacromial bursitis, and one superior glenoid labrum anterior-to-posterior lesion, missed on 7-T MRI. Evaluating all structures together, sensitivity was 86%, and specificity 74%. A better contrast and higher image resolution was noted in comparison to previous 1.5-T examinations. CONCLUSIONS: 7-T MRI of the shoulder with diagnostic image quality is feasible. Overrating of tendon signal alterations was the main limitation. Although the diagnostic performance did not reach the current results of 3-T MRI, our study marks the way to implement clinical 7-T MRI of the shoulder.

An 8-channel transceiver 7-channel receive RF coil setup for high SNR ultrahigh-field MRI of the shoulder at 7T.

PURPOSE: In this work, we present an 8-channel transceiver (Tx/Rx) 7-channel receive (Rx) radiofrequency (RF) coil setup for 7 T ultrahigh-field MR imaging of the shoulder. METHODS: A C-shaped 8-channel Tx/Rx coil was combined with an anatomically close-fitting 7-channel Rx-only coil. The safety and performance parameters of this coil setup were evaluated on the bench and in phantom experiments. The 7 T MR imaging performance of the shoulder RF coil setup was evaluated in in vivo measurements using a 3D DESS, a 2D PD-weighted TSE sequence, and safety supervision based on virtual observation points. RESULTS: Distinct SNR gain and acceleration capabilities provided by the additional 7-channel Rx-only coil were demonstrated in phantom and in vivo measurements. The power efficiency indicated good performance of each channel and a maximum B1+ of 19 µT if the hardware RF power limits of the MR system were exploited. MR imaging of the shoulder was demonstrated with clinically excellent image quality and submillimeter spatial resolution. CONCLUSIONS: The presented 8-channel transceiver 7-channel receive RF coil setup was successfully applied for in vivo 7 T MRI of the shoulder providing a clear SNR gain vs the transceiver array without the additional receive array. Homogeneous images across the shoulder region were obtained using 8-channel subject-specific phase-only RF shimming.

Factors associated with contralateral liver hypertrophy after unilateral radioembolization for hepatocellular carcinoma.

INTRODUCTION: Radioembolization for the treatment of hepatocellular carcinoma (HCC) induces liver volume changes referred to as "atrophy-hypertrophy complex". The aim of this study was to investigate lobar liver volume changes after unilateral radioembolization and to search for factors associated with hypertrophy of the untreated lobe. MATERIALS AND METHODS: Seventy-five patients were retrospectively evaluated. Inclusion criteria were: (1) right-lobar radioembolization for unresectable unilateral HCC, (2) available liver computed tomography scans before, 1, 3, and at least 6 months after radioembolization. Baseline patient characteristics included clinical features, laboratory results, spleen volume, and liver computed tomography. Absolute and relative (referred to the whole liver volume) liver lobe volumes (LLV) as well as relative LLV (rLLV) change per month were evaluated and compared. RESULTS: Absolute and relative contralateral LLV continuously increased after radioembolization (p<0.001). Mean relative contralateral LLV increased from 36±11.6% before radioembolization to 50±15.3% 6 months after radioembolization. Median contralateral rLLV increase/month (within first 6 months) was 2.5%. Contralateral rLLV increase/month was significantly lower in patients with ascites (p = 0.017) or platelet count <100/nl (p = 0.009). An inverse correlation of contralateral rLVV increase/month with spleen volume (p = 0.017), patient age (p = 0.024), Child Pugh score (p = 0.001), and tumor burden (p = 0.001) was found. CONCLUSIONS: Significant contralateral hypertrophy and ipsilateral atrophy were common after unilateral radioembolization. Small spleen volume, low patient age, low Child Pugh score, absence of ascites, platelet count ≥100/nl, and low tumor burden were associated with increased contralateral hypertrophy, indicating that younger patients with compensated cirrhosis might benefit most from radioembolization in a "bridge-to-resection" setting.

Morphological and Quantitative 7 T MRI of Hip Cartilage Transplants in Comparison to 3 T-Initial Experiences.

OBJECTIVES: The aims of this study were to evaluate morphological and quantitative 7 T magnetic resonance imaging (MRI) hip sequences in patients after acetabular cartilage transplantation and to compare image quality with 3 T MRI. MATERIALS AND METHODS: Following approval from the local institutional ethics committee and signing informed consent, 9 patients with history of autologous acetabular cartilage transplantation were imaged at 7 T and 3 T MRI. Sequences (3-dimensional dual echo steady state, 3-dimensional T1 volume interpolated breath-hold examination, sagittal proton density [PD] turbo spin echo and coronal fat-saturated PD turbo spin echo, sagittal T1 mapping in dual flip angle technique, and multiecho spin echo/gradient echo sequences for T2 and T2* mapping) were applied after the intravenous application of Gd-DTPA according to a protocol for delayed gadolinium-enhanced MRI of cartilage and manual B1 shimming at 7 T. Images were compared intraindividually regarding image quality and assessability of cartilage structures using 5-point scales (1 = 3 T clearly superior, 5 = 7 T clearly superior) in consensus with 2 radiologists. Contrast ratios were calculated between articular cartilage, joint fluid, and subchondral bone. An adapted MOCART (MR observation of cartilage repair tissue) score was assessed independently at 3 T and 7 T. Relaxation times were measured in the transplanted acetabular region and in 2 reference regions by 2 readers independently to calculate interreader reliability. Statistical significances of field strength comparisons were calculated using Student t test and t test for dependent measurements. RESULTS: A 7 T MRI was superior to 3 T MRI in the majority of the sequences regarding subjective ratings. Furthermore, 7 T yielded comparable or better contrast ratios compared with 3 T. The criteria of the MOCART score matched totally at 3 T and 7 T, apart from the signal intensity of the repair tissue in PDw, which was rated higher at 7 T in 5 patients. Interreader reliability of all relaxation times was excellent. T1 and T2* relaxation times were significantly shorter at 7 T compared with 3 T. T2 relaxation times were longer at 7 T compared with 3 T without statistical significance. No significant difference could be seen when comparing the relaxation ratios (relaxation times after standardization to reference regions) of the cartilage transplant between the 2 field strengths. CONCLUSIONS: This study shows the feasibility of morphological and quantitative 7 T hip MRI in patients after acetabular cartilage transplantation and its predominant superiority regarding image quality, assessment of cartilage transplants, and contrast over 3 T MRI. To compare relaxation times between the field strengths, the calculation of intraindividual ratios is recommended.

7 Tesla quantitative hip MRI: a comparison between TESS and CPMG for T2 mapping.

OBJECTIVES: We aimed to evaluate the feasibility of triple-echo steady state (TESS) T2 mapping as an alternative to conventional multi-echo-spin-echo (CPMG) T2 mapping for the quantitative assessment of hip joint cartilage at 7 T. MATERIALS AND METHODS: A total of eight healthy volunteers and three patients were included. Reproducibility of both techniques was evaluated in five volunteers in five scans each. T2 relaxation times were measured by manually drawing regions of interest in multiple regions of the hip joint. Data from both methods were compared using Pearson correlation coefficient, intra-class correlation coefficient, and coefficient of repeatability. The overall image quality and presence of artifacts was assessed. RESULTS: Cartilage transplant and surrounding fluid were well depicted by both methods. Compared to CPMG, TESS provided systematically reduced T2 values (43.3 ± 7.3 vs. 19.2 ± 5.5 ms for acetabular cartilage, and 41.4 ± 5.6 vs. 21.7 ± 5.2 ms for femoral cartilage), in line with previously reported values. No correlation between both methods was found. TESS yielded a slightly better reproducibility than CPMG, while CPMG showed pronounced sensitivity to B1 inhomogeneities. CONCLUSION: TESS seems to be an attractive alternative to CPMG for improvements in quantitative hip joint imaging at 7 T, allowing shortening of the total acquisition time paired with insensitivity to B1, while rendering comparable image quality with good repeatability.

Morphological imaging and T2 and T2* mapping of hip cartilage at 7 Tesla MRI under the influence of intravenous gadolinium.

OBJECTIVES: To investigate the influence of intravenous gadolinium on cartilage T2 and T2* relaxation times and on morphological image quality at 7-T hip MRI. METHODS: Hips of 11 healthy volunteers were examined at 7 T. Multi-echo sequences for T2 and T2* mapping, 3D T1 volumetric interpolated breath-hold examination (VIBE) and double-echo steady-state (DESS) sequences were acquired before and after intravenous application of gadolinium according to a delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) protocol. Cartilage relaxation times were measured in both scans. Morphological sequences were assessed quantitatively using contrast ratios and qualitatively using a 4-point Likert scale. Student's t-test, Pearson's correlation (ρ) and Wilcoxon sign-rank test were used for statistical comparisons. RESULTS: Pre- and post-contrast T2 and T2* values were highly correlated (T2: acetabular: ρ = 0.76, femoral: ρ = 0.77; T2*: acetabular: ρ = 0.80, femoral: ρ = 0.72). Gadolinium enhanced contrasts between cartilage and joint fluid in DESS and T1 VIBE according to the qualitative (p = 0.01) and quantitative (p < 0.001) analysis. The delineation of acetabular and femoral cartilage and the labrum predominantly improved with gadolinium. CONCLUSIONS: Gadolinium showed no relevant influence on T2 or T2* relaxation times and improved morphological image quality at 7 T. Therefore, morphological and quantitative sequences including dGEMRIC can be conducted in a one-stop-shop examination. KEY POINTS: • Hip cartilage T2 values correlate highly before and after gadolinium at 7 T • Hip cartilage T2* values correlate highly before and after enhancement at 7 T • Morphological hip cartilage imaging benefits from intravenous gadolinium at 7 T • The delineation of acetabular and femoral cartilage can be improved by gadolinium • Morphological and quantitative sequences including dGEMRIC can be combined as a one-stop-shop examination.