In a series of 25 patients with histologically proven mass lesions of the posterior fossa, computerized transaxial tomography (CTT) and radionuclide (RN) brain imaging detected 23 (92%) and 22 (88%) of the 25 tumors, respectively. In this small group of patients, the difference is not statistically significant. When the results of both techniques were combined, the detection rate was 100%, which emphasizes the complementary value of the two procedures. The two lesions not detected by CTT were

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... tastatic carcinomas, and contrast enhancement was not employed. The three lesions not detected by RN imaging were cystic. The results may represent underestimates of the true sensitivity of both techniques since the use of contrast enhancement with CTT and of posterior flow studies and magnified static RN images of the posterior fossa would probably improve the sensitivity of both tests.