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Single photon emission computed tomography (SPECT) of the central nervous system (CNS) has many potentially useful interventional neuroradiologic applications. CNS SPECT allows easy and safe evaluation of the collateral circulation during internal carotid balloon test occlusion. The cerebrovascular distribution of intracarotid amobarbital sodium, which is used in the Wada test, can be accurately determined with simultaneous injection of a radiopharmaceutical. Easy and safe evaluation of the extent and distribution of vasospasm associated with subarachnoid hemorrhage or cerebral angiography is also possible with CNS SPECT. Images obtained after administration of acetazolamide can be compared with baseline images to evaluate cerebrovascular reserve before carotid endarterectomy. Seizure foci can be identified if peripheral intravenous injection is performed during an ictus. Thallium-201 imaging can be used to direct stereotactic brain biopsy to check for tumor recurrence. Radiologists need to familiarize themselves and their clinical colleagues with the many uses of this imaging technique.

Evidence indicates that the accumulation of glutamine in the brain plays an important role in the pathogenesis and severity of the encephalopathy of acute liver failure (ALF). This study uses in vivo proton magnetic resonance spectroscopy (1H MRS) to assess brain glutamine (GLN) in five cases of acute liver failure. The findings are consistent with prior investigations and suggest that the alpha 1H of the GLN molecule can be used for noninvasive spectroscopic quantitation of brain GLN in patients with ALF.

Hyperintensity in the basal ganglia of patients with serious liver disease is a common finding on T1-weighted magnetic resonance images. In this study, we used optical densitometry to quantitatively evaluate the hyperintense magnetic resonance image signal changes in the various regions of the brain of patients with chronic hepatic encephalopathy. The incidence and morphological distribution of the magnetic resonance signal changes were evaluated from T1-weighted magnetic resonance images of the brain from seven non-alcoholic patients and six healthy controls. Significant differences (p < 0.05) between the patient group and controls were found in the limbic system (hippocampus, temporal lobe, cingulate gyrus, and fornix), extrapyramidal system and associated myelinated pathways (lentiform nucleus, tectum, tegmentum, cerebral peduncles, internal capsule and the corpus callosum). No measurable differences were observed in the frontal, parietal, and occipital cortex, or the dorsomedial thalamus. The presence of the high signal intensity changes on T1-weighted magnetic resonance image suggests that characteristics alterations occur in functional regions of the brain in chronic hepatic encephalopathy.

Through the Magnetic Resonance Imaging (MRI) sequences with T1 weighting (TR 600 msec/TE 20 msec) of the brain, the high intensity lesions due to hepatic encephalopathy have been demonstrated markedly. The data have been collected were based upon eleven patients with clinically proven hepatic encephalopathy. Three sets of normal brain MRI which were identified with no evidence of brain or liver diseases were also included in this study. After the brain MRI slices have been identified, it showed that the affected regions of interest (ROI) were around the largest third ventricle. The histogram which was generated out of that particular slice is composed of two distinguished peaks lumped together. After the decomposition and curve fitting procedures, the Gaussian distributions were identified with the mean value and the standard deviation. One was assumed to be gray index region for gray and white matter, the other with higher gray index value was the contribution of hepatic encephalopathy. Once the range of the distribution has been determined, the affected portion can be marked and highlighted. This mechanism of histogram decomposition and curve fitting techniques shows the valuable correlation with the clinical status of MR findings.

We assessed the morphologic findings of the brain prospectively before and after cardiac surgery using magnetic resonance imaging. There were 12 patients with acyanotic and 6 with cyanotic heart disease. There were 2 deaths, and 1 patient did not have to undergo postoperative magnetic resonance imaging. The study group consisted of 15 patients completing both the preoperative and postoperative magnetic resonance imagings. All patients in the study group underwent moderate hypothermic cardiopulmonary bypass using a nonpulsatile membrane oxygenator. The mean (+/- SD) cardiopulmonary bypass time was 100 +/- 55 minutes. Ten of the preoperative studies were interpreted as normal. One third (5 of 15) of the patients showed ventriculomegaly and dilatation of the subarachnoid spaces on preoperative magnetic resonance images. Measurements of the preoperative and postoperative magnetic resonance images showed a postoperative increase in the bicaudate and third ventricular diameters. Four patients in the study group developed postoperative subdural hematomas. The subdural hematomas were small and caused no demonstrable mass effect on magnetic resonance imaging. One patient had a preoperative white matter infarction. There was 1 patient with a postoperative infarction.