[en] Lhermitte-Duclos disease (LDD; dysplastic cerebellar gangliocytoma) is a rare hamartomatous lesion of the cerebellar cortex and this was first described in 1920. LDD is considered to be part of the autosomal-dominant phacomatosis and cancer syndrome Cowden disease (CS). We examined the brain of a 46-year-old man, who displayed the manifestations of CS, with 7 Tesla (T) and 1.5T MRI and 1.5T MR spectroscopy (1H-MRS). We discuss the possible benefits of employing ultrahigh-field MRI for making the diagnosis of this rare lesion

[en] To evaluate the usefulness of the metal artifact reduction technique ''WARP'' in the assessment of metal-on-metal hip resurfacings at 1.5 and 3T in the context of image quality and imaging speed. Nineteen patients (25 hip resurfacings) were randomized for 1.5 and 3T MRI, both including T1 and T2 turbo spin-echo as well as turbo inversion recovery magnitude sequences with and without view angle tilting and high bandwidth. Additional 3T sequences were acquired with a reduced number of averages and using the parallel acquisition technique for accelerating imaging speed. Artifact size (diameter, area), image quality (5-point scale) and delineation of anatomical structures were compared among the techniques, sequences and field strengths using the Wilcoxon sign-rank and paired t-test with Bonferroni correction. At both field strengths, WARP showed significant superiority over standard sequences regarding image quality, artifact size and delineation of anatomical structures. At 3T, artifacts were larger compared to 1.5T without affecting diagnostic quality, and scanning time could be reduced by up to 64 % without quality degradation. WARP proved useful in imaging metal-on-metal hip resurfacings at 1.5T as well as 3T with better image quality surrounding the implants. At 3T imaging could be considerably accelerated without losing diagnostic quality. (orig.)

[en] To analyze remodeling processes after advanced core decompression (ACD) in patients with avascular femoral head necrosis by means of 3T MRI and to identify indicators for clinical outcome considering the defect size and characteristics of the bone graft and of the neighboring regeneration tissue. Thirty-four hips, with preexisting preoperative MRIs in 21 cases, were examined 1-34 months (mean 12.7) postoperatively by 3T MRI. The volume of necrosis was measured manually pre- and postoperatively to calculate absolute as well as percentage necrosis reduction. The signal intensity of the bone graft was quantified using a 4-point scale. Border phenomena between the bone graft and bone were described and classified into groups. Wilcoxon sign-rank test was used to identify correlations between the analyzed items and clinical signs of femoral head collapse after a mean follow-up time of 28.6 months (10.4-46.8). Mean percentage reduction of necrosis was significantly higher in asymptomatic patients (59.36 %) compared to patients with signs of femoral head collapse (28.78 %, p = 0.008). Signal intensity of the bone graft increased in T1w and T2w TIRM sequences over time after surgery and was significantly higher in asymptomatic patients. Five border phenomena between the bone graft and healthy bone were identified. Among them, the so-called ''rail sign'' representing three layers of remodeling tissue correlated with the histological observations. A variety of border phenomena representing remodeling processes have been described using 3T MRI. Beneath the percentage amount of necrosis reduction, we identified the signal intensity of the bone graft as an indicator for clinical outcome. (orig.)

[en] To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil. In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B₀ shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists. Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B₁ signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers. The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value. (orig.)

[en] To evaluate the diagnostic potential of PET/MRI with [¹⁸F]FDG in recurrent ovarian and cervical cancer in comparison to PET/CT. A group of 19 patients with suspected recurrence of pelvic malignancies (ovarian cancer, 11 patients; cervical cancer, 8 patients) scheduled for an [¹⁸F]FDG PET/CT were subsequently enrolled for a PET/MRI. The scan protocol comprised: (1) a T1-W axial VIBE after contrast agent adminstration, (2) an axial T2-W HASTE, (3) a coronal TIRM, (4) an axial DWI, and dedicated MR sequences of the female pelvis including (5) a T1-W VIBE before contrast agent adminstration, (6) a sagittal T2-W TSE, and (7) a sagittal T1-W dynamic VIBE. The datasets (PET/CT, PET/MRI) were rated separately by two readers regarding lesion count, lesion localization, lesion conspicuity (four-point scale), lesion characterization (benign/malignant/indeterminate) and diagnostic confidence (three-point scale). All available data (histology, prior examinations, PET/CT, PET/MRI, follow-up examinations) served as standard of reference. Median values were compared using the Wilcoxon rank sum test. Metastatic lesions were present in 16 of the 19 patients. A total of 78 lesions (malignant, 58; benign, 20) were described. Both PET/CT and PET/MRI allowed correct identification of all malignant lesions and provided equivalent conspicuity (3.86 ± 0.35 for PET/CT, 3.91 ± 0.28 for PET/MRI; p > 0.05). Diagnostic confidence was significantly higher for PET/MRI in malignant (p < 0.01) and benign lesions (p < 0.05). Both PET/CT and PET/MRI offer an equivalently high diagnostic value for recurrent pelvic malignancies. PET/MRI offers higher diagnostic confidence in the discrimination of benign and malignant lesions. Considering the reduced radiation dose and superior lesion discrimination, PET/MRI may serve as a powerful alternative to PET/CT in the future. (orig.)

[en] In this study tumour vascularity and necrosis of intracranial astrocytomas were compared using 7 T and 1.5 T magnetic resonance imaging (MRI). Fifteen patients with histologically proven astrocytomas (WHO grades II-IV) were prospectively examined at 1.5 T (Magnetom Espree or Sonata) and 7 T (Magnetom 7 T, Siemens, Erlangen, Germany) with T2*-w (weighted), T1-w with (only a subset of five patients at 7 T) and without contrast medium, T2-w and proton-density (PD)-w MRI. Clinically used 1.5 T sequences were adapted to 7 T. Histological findings and T2*-w MR images at both field strengths were compared for the presence of assumed tumour microvascularity and necrosis. Two diffusely infiltrating astrocytomas, four anaplastic astrocytomas and nine glioblastomas were included. T2*-w images depicted susceptibility patterns representing presumed tumour microvascularity in 8 out of 15 (53%) gliomas at 7 T compared with 5 out of 15 (33%) gliomas at 1.5 T. Compared with 1.5 T MRI three additional necrotic tumour areas were depicted only on 7 T T2- and T2*-w images of one glioblastoma. On T1-w MR images, contrast enhancement of five out of five glioblastomas was similar at both field strengths. 7 T gradient-echo sequences provide excellent image contrast of presumed microvasculature and necrosis in astrocytomas. (orig.)

[en] To evaluate the technical feasibility and applicability of quantitative MR techniques (delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T2 mapping, T2* mapping) at 7 T MRI for assessing hip cartilage. Hips of 11 healthy volunteers were examined at 7 T MRI with an 8-channel radiofrequency transmit/receive body coil using multi-echo sequences for T2 and T2* mapping and a dual flip angle gradient-echo sequence before (T1_0) and after intravenous contrast agent administration (T1_G_d; 0.2 mmol/kg Gd-DTPA"2"- followed by 0.5 h of walking and 0.5 h of rest) for dGEMRIC. Relaxation times of cartilage were measured manually in 10 regions of interest. Pearson's correlations between R1_d_e_l_t_a = 1/T1_G_d - 1/T1_0 and T1_G_d and between T2 and T2* were calculated. Image quality and the delineation of acetabular and femoral cartilage in the relaxation time maps were evaluated using discrete rating scales. High correlations were found between R1_d_e_l_t_a and T1_G_d and between T2 and T2* relaxation times (all p < 0.01). All techniques delivered diagnostic image quality, with best delineation of femoral and acetabular cartilage in the T2* maps (mean 3.2 out of a maximum of 4 points). T1, T2 and T2* mapping of hip cartilage with diagnostic image quality is feasible at 7 T. To perform dGEMRIC at 7 T, pre-contrast T1 mapping can be omitted. (orig.)

[en] To investigate the influence of intravenous gadolinium on cartilage T2 and T2* relaxation times and on morphological image quality at 7-T hip MRI. 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. 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. 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. (orig.)

[en] The aim of this study was to investigate the feasibility of dynamic contrast-enhanced 7 T MRI of the liver using an eight-channel radiofrequency (RF) transmit/receive body-coil. 16 healthy subjects were examined on a 7 T MR system utilizing a custom-built eight-channel RF body-coil suitable for RF-shimming. The following data were acquired: (1) steady state free precession imaging, (2) T2w turbo spin echo imaging, (3) T1w in and opposed-phase imaging, (4) T1w 3D FLASH images pre-contrast and in arterial, portal-venous and venous phase and (5) a fat-saturated pre- and post-contrast 2D FLASH sequence. Visual evaluation of (1) the delineation of liver vasculature, (2) the overall image quality, and (3) artifact presence and consequent image impairment was performed. SNR of the liver parenchyma was measured for the contrast-enhanced 2D and 3D FLASH sequences. For statistical analysis, a Wilcoxon-Rank Test was used. Best delineation of non-enhanced liver vasculature and overall image quality was found for 2D FLASH MRI, with only slight improvement in vessel conspicuity after the application of contrast media. T2-weighted TSE imaging remained strongly impaired, falling short of diagnostic relevance and precluding a clinical application. Our results demonstrate the feasibility and diagnostic potential of dedicated contrast-enhanced 7 T liver MRI as well as the potential for non-contrast-enhanced angiographic application

[en] The aim of this study was to evaluate sequences that are established at lower magnetic field strengths for lumbar spine imaging at 7 Tesla (7 T) MR imaging. The lumbar spine of five healthy volunteers and a patient with spina bifida and meningocele were evaluated at 7 T. The examination included a T2-TSE (turbo spin echo), a 3D-DESS (double-echo steady-state sequence), a 3D-CISS (constructive interference in steady-state sequence), and a 3D-VIBE (volumetric interpolated breath hold examination) sequence. Imaging quality was evaluated by two raters on a three-level scale. The assessment included visualization of intraforaminal structures, the cauda equina, facet joints, and any abnormalities. Contrast ratios for intervertebral discs/vertebral bodies, vertebral bodies/cerebrospinal fluid (CSF) and CSF/spinal cord were calculated. The 3D-VIBE sequence provided best differentiation between intraforaminal structures. Visualization of the facet joints was reliable with VIBE, DESS, and CISS. Individual nerve roots of the cauda equina could only be delineated with the 3D-CISS sequence. CISS and DESS provided good contrast between vertebral bodies and intervertebral discs. Contrast between CSF and vertebral bodies was most pronounced for the T2-TSE sequence. Sufficient contrast between CSF and the spinal cord was only achieved with the T2-TSE sequence. VIBE and DESS sequences demonstrated best the bony malformations. Visualization of the meningocele was only possible with the 3D-CISS sequence. At 7 T most structures of the lumbar spine were visualized with a combination of sequences. At present, imaging quality is not superior to 1.5 T or 3 T, precluding routine clinical use. (orig.)