Johannes M. Hoogduin

High-resolution magnetization-prepared 3D-FLAIR imaging at 7.0 Tesla.

The aim of the present study is to develop a submillimeter volumetric (three‐dimensional) fluid‐attenuated inversion recovery sequence at 7T. Implementation of the fluid‐attenuated inversion recovery sequence is difficult as increased T1 weighting from prolonged T1 constants at 7T dominate the desired T2 contrast and yield suboptimal signal‐to‐noise ratio. Magnetization preparation was used to reduce T1 weighting and improve the T2 weighting. Also, practical challenges limit the implementation. Long refocusing trains with low flip angles were used to mitigate the specific absorption rate constraints. This resulted in a three‐dimensional magnetization preparation fluid‐attenuated inversion recovery sequence with 0.8 × 0.8 × 0.8 = 0.5 mm3 resolution in a clinically acceptable scan time. The contrast‐to‐noise ratio between gray matter and white matter (contrast‐to‐noise ratio = signal‐to‐noise ratio [gray matter] − signal‐to‐noise ratio [white matter]) increased from 12 ± 9 without magnetization preparation to 28 ± 8 with magnetization preparation (n = 12). The signal‐to‐noise ratio increased for white matter by 13 ± 6% and for gray matter by 48 ± 15%. In conclusion, three‐dimensional fluid‐attenuated inversion recovery with high resolution and full brain coverage is feasible at 7T. Magnetization preparation reduces the T1 weighting, thereby improving the T2 weighted contrast and signal‐to‐noise ratio. Magn Reson Med, 2010.

Effects of fluoxetine on disease activity in relapsing multiple sclerosis: a double-blind, placebo-controlled, exploratory study

Background: Suppressing the antigen-presenting capacity of glial cells could represent a novel way of reducing inflammatory activity in multiple sclerosis (MS). Aims: To evaluate the effects of fluoxetine on new lesion formation in patients with relapsing MS. Methods: In a double-blind, placebo-controlled exploratory study, 40 non-depressed patients with relapsing remitting or relapsing secondary progressive MS were randomised to oral fluoxetine 20 mg or placebo daily for 24 weeks. New lesion formation was studied by assessing the cumulative number of gadolinium-enhancing lesions on brain MRI performed on weeks 4, 8, 16 and 24. Results: Nineteen patients in both groups completed the study. The mean (SD) cumulative number of new enhancing lesions during the 24 weeks of treatment was 1.84 (2.9) in the fluoxetine group and 5.16 (8.6) in the placebo group (p = 0.15). The number of scans showing new enhancing lesions was 25% in the fluoxetine group versus 41% in the placebo group (p = 0.04). Restricting the analysis to the past 16 weeks of treatment showed that the cumulative number of new enhancing lesions was 1.21 (2.6) in the fluoxetine group and 3.16 (5.3) in the placebo group (p = 0.05). The number of patients without enhancing lesions was 63% in the fluoxetine group versus 26% in the placebo group (p = 0.02). Conclusions: This proof-of-concept study shows that fluoxetine tends to reduce the formation of new enhancing lesions in patients with MS. Further studies with this compound are warranted. Trial registration: Number: ISRCTN65586975

Signal to noise ratio and uncertainty in diffusion tensor imaging at 1.5, 3.0, and 7.0 Tesla

To compare diffusion tensor imaging (DTI) measurements at ultra high field strength (7 Tesla [T]) in human volunteers with DTI measurements performed at 1.5 and 3 Tesla.

Reproducibility of 3.0 Tesla Magnetic Resonance Spectroscopy for Measuring Hepatic Fat Content

To investigate reproducibility of proton magnetic resonance spectroscopy (1H‐MRS) to measure hepatic triglyceride content (HTGC).

The fractionated dipole antenna: A new antenna for body imaging at 7 Tesla.

Dipole antennas in ultrahigh field MRI have demonstrated advantages over more conventional designs. In this study, the fractionated dipole antenna is presented: a dipole where the legs are split into segments that are interconnected by capacitors or inductors.

Dynamic subcortical blood flow during male sexual activity with ecological validity: a perfusion fMRI study.

This study used arterial spin labeling (ASL) fMRI to measure brain perfusion in a group of healthy men under conditions that closely resembled customary sexual behavior. Serial perfusion measures for 30 min during two self-limited periods of partnered penis stimulation, and during post-stimulatory periods, revealed novel sexual activity-related cerebral blood flow (rCBF) changes, mainly in subcortical parts of the brain. Ventral pallidum rCBF was highest during the onset of penile erection, and lowest after the termination of penis stimulation. The perceived level of sexual arousal showed the strongest positive association with rCBF in the right basal forebrain. In addition, our results demonstrate that distinct subregions of the hypothalamus and cingulate cortex subserve opposite functions during human male sexual behavior. The lateral hypothalamus and anterior part of the middle cingulate cortex showed increased rCBF correlated with penile erection. By contrast, the anteroventral hypothalamus and subgenual anterior cingulate cortex exhibited rCBF changes correlated with penile detumescence after penile stimulation. Continuous rapid and high-resolution brain perfusion imaging during normal sexual activity has provided novel insights into the central mechanisms that control male sexual arousal.

Dissected Sentinel Lymph Nodes of Breast Cancer Patients: Characterization with High-Spatial-Resolution 7-T MR Imaging

PURPOSE To investigate the association of 7-T magnetic resonance (MR) imaging characteristics with metastatic nodal invasion, determined with histopathologic assessment in dissected sentinel lymph nodes of breast cancer patients. MATERIALS AND METHODS Institutional review board approval and informed consent were obtained. From November 2008 to July 2010, 114 dissected lymph nodes from 33 women (mean age, 57 years; range, 31-80 years) with breast cancer were included. For morphological analysis, three-dimensional (3D) T1-weighted fat-suppressed fast field- (gradient-) echo (isotropic resolution, 180 μm) MR was performed; 3D nodal dimensions, maximum cortical thickness, and presence of fatty hilum were noted. For quantitative parametric analysis, two-dimensional T1-weighted and 3D T2-, T2*-, and diffusion-weighted images were acquired. Statistical analysis included generalized estimating equations (GEEs), forward and backward stepwise regression analyses, and calculation of positive predictive value (PPV) and negative predictive value (NPV). RESULTS Of 114 nodes, 26 (23%) were malignant. Morphological criteria showed weak discriminatory power: A fatty center was absent in 35% of malignant nodes and 30% of benign nodes (P = .9). Nodal volume and length-width ratio were not significantly different (P = .11 and .75, respectively). Cortical thickness (threshold level, 3 mm; P = .02) showed 91% NPV for malignancy and 95% NPV for presence of macrometastases. Quantitative parametric analyses showed comparable mean T1, T2, and T2* relaxation time constants and apparent diffusion coefficient for metastatic and benign nodes: 991 msec, 30 msec, and 18 msec and 0.17 mm²/sec versus 1035 msec (P = .14), 31 msec (P = .001; not significant after GEE), and 15 msec (P = .002) and 0.20 mm²/sec (P = .38), respectively. Mean T2* alone offered an additive discriminatory effect for identification of metastatic nodes. Consistent with the notion of pannodal changes accompanying tumor infiltration, mean T2* differed significantly even if only micrometastases were present. The interindividual differences were small, precluding easy clinical implementation. CONCLUSION Morphological criteria showed poor discriminatory power, even with very-high-spatial-resolution imaging. T2* quantification allowed identification of metastatic nodal invasion.

Decreased Cerebellar Fiber Density in Cortical Myoclonic Tremor but Not in Essential Tremor

Pathophysiology of tremor generation remains uncertain in ‘familial cortical myoclonic tremor with epilepsy’ (FCMTE) and essential tremor (ET). In both disorders, imaging and pathological studies suggest involvement of the cerebellum and its projection areas. MR diffusion tensor imaging allows estimation of white matter tissue composition, and therefore is well suited to quantify structural changes in vivo. This study aimed to compare cerebellar fiber density between FCMTE and ET patients and healthy controls. Seven FCMTE patients, eight ET patients, and five healthy controls were studied. Cerebellum was annotated based on fractional anisotropy (FA) and mean diffusivity volumes. Mean cerebellar FA values were computed as well as mean cerebellar volume. Group statistics included one-way ANOVAs and post hoc independent t tests. Mean FA of the cerebellar region for FCMTE was 0.242 (SD = 0.012), for ET 0.259 (SD = 0.0115), and for controls 0.262 (SD = 0.0146). There was a significant group effect for FA (F(2) = 4.9, p = 0.02). No difference in mean cerebellar volume was found. Post hoc independent t tests revealed significantly decreased mean FA in FCMTE patients compared to controls (t[10] = 2.5, p = 0.03) and ET patients (t[13] = 2.9, p = 0.01), while there was no difference in mean FA between ET patients and controls (t[11] < 1.0). This study indicates for the first time microstructural damage of the cerebellar white matter in FCMTE in vivo. These results ascertain a role of the cerebellum in ‘cortical tremor’.

Diffusion weighted MRI in head-and-neck cancer: geometrical accuracy.

INTRODUCTION The aim of this study is to assess the geometric accuracy of diffusion weighted (DW)-MRI by quantification of geometric distortions in the gross tumor volume (GTV) in head and neck (HN) cancer. MATERIALS & METHODS A retrospective analysis was performed on the data of 23 patients (with 24 lesions). For these patients, magnetic field maps and DW-MRI were acquired. The magnetic field maps were converted to voxel displacement maps. GTV delineations were transferred onto these voxel displacement maps and the voxel shifts in the GTV were analyzed. RESULTS The median shift was 3.2mm and the maximal posterior and anterior shifts were up to 15.0 and 26.0mm respectively. The range of shifts varied from 11.8 to 25.6mm. The percentage of GTV voxels that showed a shift of at least 6mm was found to be 23.2%. CONCLUSIONS Current DW-MRI images of HN tumors show severe distortions up to centimeters, which restrict the use of DW-MRI scans for GTV definition in RT treatment planning.

Microbleeds, lacunar infarcts, white matter lesions and cerebrovascular reactivity — A 7 T study ☆

The underlying pathology of lacunar infarcts, white matter lesions and also of microbleeds is poorly understood. We assessed whether the presence of lacunar infarcts, white matter lesions or microbleeds on MRI was associated with a decrease in cerebrovascular reactivity, and assessed whether this association was similar for lacunar infarcts, white matter lesions and microbleeds. BOLD-fMRI scan with breath-holding at 7 T and anatomical scans at 1.5 T were available in 49 patients with atherosclerotic disease from the Second Manifestations of ARTerial disease (SMART) study. Microbleeds and lacunar infarcts were scored visually and volumetric assessment of white matter lesions was performed on the 1.5 T scan. The percentage of voxels with a significant signal change on breath-holding and the whole brain signal change were calculated as measures of cerebrovascular reactivity. The mean percentage of voxels with a significant signal change was 25.1% (SD 6.6) and the mean percentage whole brain signal change was 1.20% (SD 0.51). Age, gender, and diastolic blood pressure were significantly associated with cerebrovascular reactivity. Cerebrovascular reactivity was lower with increasing age, lower in females compared to males and lower with lower diastolic blood pressure. ANCOVA showed that patients with microbleeds (n=18) had a significantly lower whole brain signal change than patients without microbleeds, with a mean difference of -0.36% (95% CI -0.64 to 0.07), independent of age, sex, systolic and diastolic blood pressure and non-lacunar infarcts. No significant associations were found for presence of lacunar infarcts or white matter lesion volume with whole brain signal change or percentage of voxels with a significant signal change. The results show that presence of microbleeds is associated with an impaired cerebrovascular reactivity in patients with atherosclerotic disease, whereas no significant association was found for the presence of lacunar infarcts or white matter lesions in our study.