CONTRIBUTION OF MAGNETIC-RESONANCE SPECTROSCOPIC IMAGING AND L-[1-C-11]TYROSINE POSITRON EMISSION TOMOGRAPHY TO LOCALIZATION OF CEREBRAL GLIOMAS FOR BIOPSY

PROTON MAGNETIC RESONANCE spectroscopic imaging (H-1-MRSI) and positron emission tomography with the tracer L-[1-C-11]tyrosine (C-11-TYR) were used to localize gliomas for biopsy or resection. This is especially helpful in cases of low-grade gliomas, if these lesions are not visualized by contrast-enhanced computed tomographic and magnetic resonance imaging scans. The clues to improved localization are provided by changes in tissue metabolite contents, such as elevation of phosphocholine, indicating cellular proliferation; decrease of N-acetylaspartate, denoting toss of neurons (as these are replaced by tumor cells); and elevation of lactate, pointing to the prevalence of glycolysis, as observed in many tumors. These data on tissue metabolite content have been obtained in vivo in the patient by proton magnetic resonance spectroscopy; metabolite maps derived from these data then visualize the distribution of the various metabolites over the section of the brain under investigation. Alternatively, localization of a tumor may be achieved by means of positron emission tomography depicting the pattern of uptake of the amino acid tracer C-11-TYR, as it tends to be incorporated in the process of cellular proliferation and protein biosynthesis. Five cases are presented as examples

Time-of-flight magnetic resonance angiography in the follow-up of intracranial aneurysms treated with Guglielmi detachable coils

The purpose of this study was to evaluate time-of-flight magnetic resonance angiography (MRA) in the follow-up of intracranial aneurysms treated with Guglielmi detachable coils (GDCs). From January 1998 to January 2002 27 MRA and intra-arterial digital subtraction angiography (IADSA) examinations were analyzed for residual aneurysms and arterial patency following GDC placement. A total number of 33 intracranial aneurysms was analyzed, including 18 located in the posterior circulation. The MRA analysis was based on source images in combination with maximum intensity projections. The IADSA was used as the reference standard. Two aneurysms were excluded from evaluation, because of susceptibility artefacts from other aneurysms, which were clipped. Sensitivity and positive predictive values of MRA in revealing residual aneurysms were, respectively, 89% and 80%. Specificity in ruling out remnant necks and residual flow around coils was, respectively, 91% and 97%, with a negative predictive value of, respectively, 95% and 100%. Specificity and negative predictive value of MRA for arterial occlusion were, respectively, 87% and 100% for the parent arteries and, respectively, 85% and 100% for the adjacent arteries. MRA is a reliable diagnostic tool in the follow-up of GDC treatment, and it may replace IADSA in excluding residual flow around coils and aneurysmal necks and in ruling out arterial occlusion