BACKGROUND: Recently, many innovative MRI methods were generated to visualize different physiological and tumor biological aspects like the tumor microenvironment including the tumor oxygenation. In this study we want to generate diverse reference ranges of tumor regions in untreated glioblastoma patients. Standard values of quantitative MR imaging in these patients do not yet exist. METHODS: In this prospective study, we included 52 patients with a cerebral mass lesion who are radiologically suspicious for glioblastoma (GBM). Before patients underwent histological validation they received a conventional and a quantitative MRI (qMRI). The diagnosis was proven by stereotactic biopsy. Different areas of the presumably normal brain or the tumor were selected and the average value of the certain area was detected. Results: Mean values of quantitative T1 und T2 maps in milliseconds (ms) were determined in 35 histopathologically proven GBM cases. Therefore, reference ranges for different areas (enhancing tumor, peritumoral edema, necrosis and contralateral, healthy control region) were recorded. We detected significantly prolonged qT1 and qT2 relaxation times in all tumor regions compare to the healthy control region. CONCLUSION: With our data different regions of the tumor are distinguishable by quantitative values. Correlations with histopathologic analysis are ongoing.
Histological evidence suggests that pathology in Parkinson's disease (PD) goes beyond nigrostriatal degeneration and also affects the cerebral cortex. Quantitative MRI (qMRI) techniques allow the assessment of changes in brain tissue composition. However, the development and pattern of disease-related cortical changes have not yet been demonstrated in PD with qMRI methods. The aim of this study was to investigate longitudinal cortical microstructural changes in PD with quantitative T1 relaxometry.
Abstract A number of techniques that recently have been used for fast NMR‐imaging are based on a hybrid sequence of echo planar imaging (EPI) and FLASH imaging: after each NMR excitation several k ‐space lines are measured. The complete k ‐space is covered by performance of several excitations. It has been observed that there is usually an optimal hybrid sequence that maximizes the signal‐to‐noise ratio. In this work, a method is presented that allows a determination of the optimal sequence as a function of the relaxation times T 1 and T 2 * .
Abstract Most functional magnetic resonance imaging (fMRI) experiments are based on the blood oxygenation level dependent (BOLD) effect. This chapter consists of six sections. The first explains the basics of magnetic resonance imaging, the influence of static magnetic field distortions, the difference between T2*-weighted gradient echo and T2-weighted spin echo sequences, and the principles of echo planar imaging. The second section describes the physiological origin of the BOLD effect, in particular the influence of oxyhaemoglobin and deoxyhaemoglobin on the signal level in T2*-weighted images, and the contributions of cerebral blood flow, cerebral blood volume, and cerebral metabolic rate of oxygen consumption to the haemodynamic response function. In the third section, technical problems related to fMRI data acquisition are discussed. The fourth section provides an overview of fMRI data analysis and the fifth section is an introduction to functional connectivity analysis and resting state fMRI. The last section describes various clinical applications of fMRI.
There is mounting evidence that exercise has a positive effect on cognitive functions in older adults. To date, little is known about the neurometabolic and molecular mechanisms underlying this positive effect. The present study used magnetic resonance spectroscopic imaging (MRSI) to systematically explore the effects of physical activity on human brain metabolism in healthy aging. This is a randomised controlled assessor blinded two-armed trial (n = 53) to explore exercise induced neuroprotective and metabolic effects on the brain in cognitively healthy older adults. Participants (mean age 75.3 ± 7.2 years / 25 females) were allocated to a 12 week individualised aerobic exercise program intervention (n = 29) or a 12 week waiting control group (n = 24). Assessment included psychometric testing (memory, attention, executive function), assessment of movement-related parameters and a cardiopulmonary exercise test (CPET). 1H MRSI and 31P MRS were applied to measure metabolic profiles. Twelve weeks after allocation, all participants were reassessed with the same methods. We found that cerebral choline concentrations remained stable after 12 weeks of aerobic exercise in the intervention group while they increased in the waiting control group (interaction of group x time, p = 0.04). No effect of training was seen on cerebral N-acetyl-aspartate concentrations, nor on markers of neuronal energy reserve or BDNF levels (p > 0.5). Furthermore, there was no significant effect of the aerobic exercise intervention on cognitive outcomes (p > 0.5), nor on grey matter volumes (p > 0.5). The finding of stable choline concentrations in the intervention group over the three month period might indicate a neuroprotective effect of aerobic exercise. Choline might constitute a valid marker for an effect of aerobic exercise on cerebral metabolism in healthy aging.
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