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Purpose: To determine the optimal cutoff level of fluorine-18-labeled fluorodeoxyglucose (FDG) uptake in the differentiation of low-grade from high-grade cerebral tumors at position emission tomography (PET)., Materials and Methods: The authors retrospectively reviewed images from PET, magnetic resonance imaging, and computed tomography performed in 58 consecutive patients with histologically proved brain tumors. There were 32 high-grade tumors (20 gliomas) and 26 low-grade tumors (18 gliomas)., Results: The best cutoff level of FDG uptake ratios in the differentiation of high-grade from low-grade tumors was 1.5 for tumor-to-white matter (T/WM) ratios and 0.6 for tumor-to-cortex (T/C) ratios. These levels were the same when only gliomas were analyzed and when all tumors were analyzed. When a T/WM ratio of more than 1.5 was considered indicative of a high-grade tumor, the sensitivity and specificity were 94% and 77%, respectively. The results were similar for the T/C ratio., Conclusion: Cutoff levels of 1.5 for the T/WM FDG uptake ratio and 0.6 for the T/C ratio are useful in the differentiation of low-grade from high-grade gliomas with PET.

Experience in three patients (one each with meningioma, pineal tumor, and prominent jugular bulb) illustrates that magnetic resonance (MR) angiography can benefit from the administration of gadolinium diethylenetriaminepentaacetic acid. Data were acquired with a three-dimensional velocity-compensated (fast imaging with steady-state precession) sequence. MR angiograms were obtained with a ray projection algorithm by using maximum intensity values. Portions of the vascular anatomy--particularly venous structures and smaller arteries--were better portrayed on the postcontrast than on the precontrast angiograms. Enhancing lesions were also seen on the projection images. Enhancement of dura and extracranial tissues (sinus and nasal mucosa) can obscure vascular detail.

A transmesenteric herniation of bowel with subsequent bowel ischemia in a thirteen-year-old boy is reported. Radiographic findings were that of abdominal mass and branching radiolucencies secondary to gas within the mesenteric vasculature. The unusual distribution of vascular gas (mesenteric rather than portal) is thought to be secondary to obstruction of mesenteric veins by strangulation.

By providing information on two parameters, dual-energy computed tomography can offer clinically useful tissue signatures for metallic deposits (Ca) or injected iodine, as well as for different normal and abnormal types of brain parenchymal tissues and CSF. Cerebral CT was performed on 36 patients and tissue differences analyzed using Hounsfield notation.

Five patients who had undergone radiation therapy for cerebral tumors and whose conditions were deteriorating were examined by means of positron emission tomography (PET) with [18F] fluorodeoxyglucose. All five cases had similar clinical and computed tomographic findings. Using the PET technique the two cases of radiation necrosis were distinguished from the three recurrent tumors. In the two cases of radiation necrosis the rate of glucose utilization in the lesion was markedly reduced compared with the normal brain parenchyma. In the recurrent gliomas, however, the glucose metabolic rate was elevated. All five diagnoses were confirmed by biopsy or autopsy.

Matched regional ventilation/perfusion studies (V/Q) have traditionally been associated with ventilatory diseases, while mismatched V/Q studies have been associated more often with vascular abnormalities. The authors describe a patient with multiple pulmonary emboli who demonstrated matched ventilation and perfusion studies five hours after the onset of symptoms.

Twenty pediatric patients, aged 2-18 years, with known or suspected masses in the brain and/or spinal cord were studied with magnetic resonance imaging at 0.6T with and without use of 0.1 mmol/kg gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA). The multisection, multiecho imaging mode was utilized. Surgically proved mass lesions included astrocytoma (n = 6), medulloblastoma (n = 2), ependymoma (n = 1), craniopharyngioma (n = 1), oligodendroglioma (n = 1), germinoma (n = 1) and fibrosarcoma (n = 1). Presumptive diagnoses included astrocytoma (n = 3), arachnoid cyst (n = 1), tuberous sclerosis (n = 1), cryptic vascular malformation (n = 1), and normal (n = 1). There was dramatic enhancement in 11 of 20 patients, with improved definition of the presence and extent of lesions in six patients. No adverse effects were noted in any of the 20 patients. It is concluded that Gd-DTPA is useful in delineating the presence, extent, and number of certain lesions of the central nervous system in children.