Magnetic resonance imaging
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Assess the feasibility of proton MR spectroscopic imaging (1H-MRSI) of the striatum (putamen and caudate nucleus) in patients with Parkinson's disease and evaluate striatal neuronal density. Proton MRSI of the striatum and thalamus with 2 cc spatial resolution was performed in 10 patients with Parkinson's disease, 1 patient with atypical parkinsonism, and 13 control subjects. Single voxel proton MR spectra with signals from choline metabolites (Cho), creatine metabolites (Cr), and the putative neuronal marker, N-acetyl-aspartate (NAA), were obtained from the putamen and thalamus, but not the caudate nucleus, of patients with parkinsonism and control subjects. ⋯ The putaminal NAA/Cho ratio of the single subject with atypical parkinsonism was lower than that of 9 of the 10 patients with classic Parkinson's disease and 11 of the 13 control subjects. Likewise, the putaminal NAA/Cr ratio in the single subject with atypical parkinsonism was lower than that of 7of the patients with guided selection of spectra from very small brain volumes, is a technique that can be used to evaluate neuronal density in individual subcortical gray nuclei in the brains of patients with parkinsonism. Using this technique, we have shown that Parkinson's disease produces no change in relative levels of the neuronal marker, NAA, in the putamen.
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Craniopharyngiomas are most commonly located extra-axially in the sellar or suprasellar area. They are benign but aggressive neoplasms. This paper reports an 8-year-old girl with a large craniopharyngioma originating from the suprasellar region and extending to the posterior cranial fossa down to the region of the foramen magnum.
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Comparative Study
Fast flair imaging of the brain using the fast spin-echo and gradient spin-echo technique.
The purpose of this study was to compare the gradient spin-echo (GRASE) to the fast spin-echo (FSE) implementation of fast fluid-attenuated inversion recovery (FLAIR) sequences for brain imaging. Thirty patients with high signal intensity lesions on T2-weighted images were examined on a 1.5 T MR system. Scan time-minimized thin-section FLAIR-FSE and FLAIR-GRASE sequences were obtained and compared side by side. ⋯ Physiological ferritin deposition appeared slightly darker on FLAIR-GRASE images and susceptibility artifacts were stronger. Fatty tissue was less bright with FLAIR-GRASE. With current standard hardware equipment, the GRASE technique is not an adequate alternative to FSE for the implementation of fast FLAIR sequences in routine clinical MR brain imaging.
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Comparative Study
Fast spin-echo (FSE) and gradient- and spin-echo (GRASE) in fast MRI of the pelvis.
In this prospective study two different T2-weighted fast spin-echo (FSE) sequences and a gradient- and spin-echo (GRASE) sequence were compared in 20 consecutive patients undergoing clinical pelvic MR examinations. A GRASE and two FSE sequences were applied, whereby the FSE sequences differed from each other by altered echo spacings (15.0 and 22.5 ms) and T2 contrast. Quantitative image analysis included ROI evaluation of different S/N and C/N values. ⋯ Therefore, FSE15.0 was optimal for low intensity lesions. Short acquisition times of FSE and GRASE sequences allow application of two different techniques-fat hypointense respectively bright-for excellent lesion visualisation. This study demonstrates the usefulness of contrast manipulation in fast T2-weighted MRI techniques without special techniques, such as fat saturation.
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Currently, hyperoxia is being investigated as a method for producing contrast in magnetic resonance images of the brain, solid tumors, and the eye. However, the underlying physiological mechanisms involved in this type of contrast are still not completely understood. ⋯ These data demonstrate that dissolved plasma oxygen does not become an important contrast mechanism until the arterial oxygen tension exceeds approximately 350 mm Hg. The implication of this result to studies in other organs is discussed.