Subarachnoid space disease: diagnosis with fluid-attenuated inversion-recovery MR imaging and comparison with gadolinium-enhanced spin-echo MR imaging--blinded reader study.

PURPOSE: To evaluate fluid-attenuated inversion-recovery (FLAIR) magnetic resonance (MR) imaging in a blinded reader study for the detection of proved subarachnoid space (SAS) disease. MATERIALS AND METHODS: FLAIR MR imaging was performed in 62 patients (21 with proved SAS or meningeal disease) and 41 control patients. A subset of 24 patients (eight patients with proved SAS disease and 16 control patients) also underwent gadolinium-enhanced T1-weighted MR imaging. FLAIR images were interpreted blindly and independently by two neuroradiologists. RESULTS: For SAS disease, the overall sensitivity, specificity, and accuracy of FLAIR for both readers were 85%, 93%, and 90%. In the 15 patients with inflammatory or neoplastic meningitis only (six patients with acute subarachnoid hemorrhage [SAH] excluded), the sensitivity, specificity, and accuracy of FLAIR for both readers were 82%, 93%, and 90%. All six acute SAH cases were interpreted as abnormal on FLAIR images by both readers. In the 24 patients who underwent both FLAIR and gadolinium-enhanced T1-weighted MR imaging, the sensitivity, specificity, and accuracy of FLAIR imaging were 86%, 91%, and 89%; the sensitivity, specificity, and accuracy of gadolinium-enhanced T1-weighted imaging were 43%, 88%, and 74%. CONCLUSION: FLAIR is highly sensitive and specific for the diagnosis of SAS disease. Unenhanced FLAIR is superior to gadolinium-enhanced T1-weighted MR imaging for the diagnosis of SAS disease. These data have important implications, because FLAIR is performed without the costs and inherent risks of intravenous contrast agents. FLAIR also appears to be highly sensitive but nonspecific for acute SAH.

Differentiating recurrent tumor from radiation necrosis: time for re-evaluation of positron emission tomography?

UNLABELLED: Our purpose was to evaluate the ability of FDG PET to differentiate recurrent tumor from posttherapy radiation necrosis. METHODS: MR images, PET scans, and medical records of 84 consecutive patients with a history of a treated intracranial neoplasm were evaluated retrospectively. In all patients, recurrent tumor or radiation necrosis was suggested by clinical or MR findings. Metabolic activity of the PET abnormality was compared qualitatively with normal contralateral gray and white matter. RESULTS: PET findings were confirmed histologically in 31 patients. With contralateral white matter as the standard of comparison, the PET scan sensitivity and specificity were found to be 86% and 22%, respectively. With contralateral gray matter as the reference standard, the sensitivity and specificity became 73% and 56%, respectively. Overall, nearly one third of the patients would have been treated inappropriately in either scheme had the PET scan been the sole determinant of therapy. CONCLUSION: Our data suggest that the ability of FDG PET to differentiate recurrent tumor from radiation necrosis is limited. Both false-positive and false-negative PET scan results contributed to unacceptably low sensitivity and specificity values.

An alternative to GRASE: toward spin-echo-like contrast with independent reconstruction of gradient-echo images.

Multiple gradient echoes are generated for each RF echo of a Carr-Purcell-Meiboom-Gill (CPMG) train. Independently, phase-encoded fast spin-echo images are obtained from the different gradient echoes. Presently, three images are formed from three gradient-echoes from each of four RF echoes. The two peripheral gradient echo images are encoded for a late effective TE, then summed after reconstruction: this image has decreased fat intensity and increased susceptibility contrast compared with fast spin echo. The central gradient echoes yielded another image of intermediate contrast useful for neuroimaging. Raw data from the variously timed gradient echoes are not combined as they are in GRASE.