Abstract 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 3.2 mm and the maximal posterior and anterior shifts were up to 15.0 and 26.0 mm respectively. The range of shifts varied from 11.8 to 25.6 mm. The percentage of GTV voxels that showed a shift of at least 6 mm 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.
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.
Background:
Cerebral blood flow (CBF) is reduced in normal-appearing white matter (NAWM) of subjects with multiple sclerosis (MS), but the underlying mechanism is unknown.
Objective:
The objective of ...this article is to assess the relationship between reduced NAWM CBF and both axonal mitochondrial metabolism and astrocytic phosphocreatine (PCr) metabolism.
Methods:
Ten healthy controls and 25 MS subjects were studied with 3 Tesla magnetic resonance imaging. CBF was measured using pseudo-continuous arterial spin labeling. N-acetylaspartate/creatine (NAA/Cr) ratios (axonal mitochondrial metabolism) were obtained using 1H-MR spectroscopy and PCr/β-ATP ratios using 31P-MR spectroscopy. In centrum semiovale NAWM, we assessed correlations between CBF and both NAA/Cr and PCr/β-ATP ratios.
Results:
Subjects with MS had a widespread reduction in CBF of NAWM (centrum semiovale, periventricular, frontal and occipital), and gray matter (frontoparietal cortex and thalamus). Compared to controls, NAA/Cr in NAWM of the centrum semiovale of MS subjects was decreased, whereas PCr/β-ATP was increased. We found no correlations between CBF and PCr/β-ATP. CBF and NAA/Cr correlated in controls (p = 0.02), but not in MS subjects (p = 0.68).
Conclusions:
Our results suggest that in MS patients there is no relationship between reduced CBF in NAWM and impaired axonal mitochondrial metabolism or astrocytic PCr metabolism.
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.
Progressive visual field defects, such as age-related macular degeneration and glaucoma, prevent normal stimulation of visual cortex. We investigated whether in the case of visual field defects, ...concentrations of metabolites such as N-acetylaspartate (NAA), a marker for degenerative processes, are reduced in the occipital brain region.
Participants known with glaucoma, age-related macular degeneration (the two leading causes of visual impairment in the developed world), and controls were examined by proton MR spectroscopic ((1)H-MRS) imaging. Absolute NAA, Creatine and Choline concentrations were derived from a single-voxel in the occipital region of each brain hemisphere. No significant differences in metabolites concentrations were found between the three groups.
We conclude that progressive retinal visual field defects do not affect metabolite concentration in visual brain areas suggesting that there is no ongoing occipital degeneration. We discuss the possibility that metabolite change is too slow to be detectable.
The pathogenesis of dystonia in Complex Regional Pain Syndrome type 1 (CRPS-1) is unclear. In primary dystonia, functional magnetic resonance imaging (fMRI) has revealed changes in cerebral networks ...during execution of movement. The aim of this study was to determine cerebral network function in CRPS-1 patients with dystonic postures. Cerebral processing related to both execution and imagining of hand movements in patients and controls was assessed with fMRI. Eight CRPS-1 patients with dystonic postures of the right upper extremity and 17 age-matched healthy controls were studied. Compared with controls, imaginary movement of the affected hand in patients showed reduced activation ipsilaterally in the premotor and adjacent prefrontal cortex, and in a cluster comprising frontal operculum, the anterior part of the insular cortex and the superior temporal gyrus. Contralaterally, reduced activation was seen in the inferior parietal and adjacent primary sensory cortex. There were no differences between patients and controls when they executed movements, nor when they imagined moving their unaffected hand. The altered cerebral activation pattern in patients with CRPS-1 linked dystonia most likely reflects an interface between pain-associated circuitry and higher order motor control, which points at a specific mechanistic pathophysiology of this type of dystonia.
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.
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).
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.
Morphological criteria showed poor discriminatory power, even with very-high-spatial-resolution imaging. T2* quantification allowed identification of metastatic nodal invasion.
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