Echo-planar perfusion imaging is useful in the preoperative assessment of tumor grade and in providing diagnostic information not available with conventional MR imaging. The areas of perfusion abnormality are invaluable in the precise targeting of the stereotactic biopsy.

Gadolinium-enhanced magnetic resonance (MR) imaging studies of 30 histologically proved cranial meningiomas revealed a linear enhanced structure or "tail" extending away from the tumor mass along the dural surface in 18 cases (60%). Contrast material-enhanced computed tomographic studies available in 10 of these 18 cases did not depict this structure. Characteristic features of this MR finding were reviewed, and criteria were defined to distinguish this tail from other enhanced structures. To assess the differential diagnostic value of this finding, gadolinium diethylenetriaminepentaacetic acid-enhanced MR studies of a control group of other extraaxial lesions as well as superficial intraaxial tumors that abut the meninges were reviewed. These cases failed to show this MR feature. Pathologic correlation was available in three meningiomas with the finding of a tail, and these demonstrated meningothelial tumor nodules in the samples taken from areas corresponding to the enhanced regions on MR images. This is in agreement with other recent pathologic studies of the dura mater surrounding meningiomas. The authors believe that the linear enhanced structure described may represent tissue containing tumoral nodules. Awareness of this MR sign may be useful in distinguishing meningiomas from other lesions and in planning total resection of the infiltrated dura mater.

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Summary: Young normal subjects, old normal subjects, and patients with senile dementia of the Alzheimer's type (SDAT) were studied with both computed tomography (CT) and positron emission transaxial tomography (PETT). Increases in ventricular size with both aging and disease were measured. Regional glucose metabolic rate was not affected by age, but was markedly reduced in SDAT pa tients. These data indicate that in normal aging, structural brain changes may be more salient than biochemical Abbreviations used: CM, Canthomeatal; CT, computed to mography; FDG, 18F-2-deoxy-2-fluoro-D-glucose; GDS, Global Deterioration Scale; PETT, positron emission transaxial tomog raphy; SDAT, senile dementia of the Alzheimer's type. It is possible that a number of methodological variables, such as subject selection criteria and methods of scan analysis, may account for these