MATERIALS AND METHODS. The records of 724 consecutive patients who were referred to St. Mary's Medical Center department of radiology for fluoroscopic lumbar puncture from January 2003 through April 2007 were retrospectively reviewed. Emergency requests (191) were discarded along with those for patients with clinical signs of pseudotumor cerebri (21), normal pressure hydrocephalus (3), and failed attempts (4). The collective total was 505 elective lumbar punctures.

RESULTS. The blood patch rate for the 22-gauge Whitacre needle was 4.2%. The result for the 22-gauge Quincke point needle was 15.1% whereas that for the 20-gauge Quincke point needle was 29.6%. In addition, the level of puncture showed a blood patch rate that increased as the level of lumbar puncture lowered. The highest level of lumbar puncture was L1-L2 with the lowest recorded level being L5-S1.

CONCLUSION. The Whitacre needle is associated with a significantly lower incidence of blood patch rate after lumbar puncture. The highest level of puncture (L1-L2) also provides the lowest level of blood patch rate.

MATERIALS AND METHODS. We evaluated 34 patients with an enhancing brain tumor on MRI, including seven lymphomas, nine high-grade gliomas, and 18 metastatic tumors. All patients also underwent FDG PET. For PET image analysis, regions of interest were placed over the tumor (T), contralateral cortex (C), and white matter (WM). Average and maximum pixel values were determined at each site. On the basis of these measurements, average and maximum standard uptake values (SUV_avg and SUV_max) were calculated, along with activity ratios (T/C_avg, T/WM_avg, T/WM_max, and T/C_max), and comparisons among lesions were then made.

RESULTS. All parameters were significantly higher for lymphoma than for other tumors (p < 0.01). High-grade gliomas showed significantly higher SUV_avg and SUV_max than metastatic tumors (p < 0.05). Other parameters did not differ between lesion types. SUV_max was the most accurate parameter for distinguishing lymphomas. Using an SUV_max of 15.0 as a cutoff for diagnosing CNS lymphoma, only one high-grade glioma was found as a false-positive (SUV_max, 18.8).

CONCLUSION. FDG PET may be useful for differentiating common enhancing malignant brain tumors, particularly lymphoma versus high-grade glioma and metastatic tumor. FDG PET can provide useful information for distinguishing between lymphoma and other malignant enhancing brain tumors and is recommended when differential diagnoses are difficult to narrow using MRI alone.