In phase II and III trials of gadoteridol (Gd-HP-D03A), a new nonionic, low-osmolar contrast agent, 40 patients with intracranial neoplasms underwent magnetic resonance (MR) imaging with experimental doses of 0.05-0.3 mmol/kg. Fifteen patients also underwent contrast studies with the standard dose (0.1 mmol/kg) of gadopentetate dimeglumine. Both gadopentetate dimeglumine and gadoteridol appear to have a similar effect when given in equal doses (0.1 mmol/kg, n = 5). Lesion enhancement and delineation were better at higher experimental doses (0.2 or 0.3 mmol/kg, n = 7) and worse at a lower experimental dose (0.05 mmol/kg, n = 3). Quantitative analysis of 10 lesions examined with identical imaging protocols revealed a directly proportional relationship (r = .975) between lesion contrast ratio and dose over a range of 0.05-0.3 mmol/kg. Phantom experiments support the clinical results. Improved enhancement, detection, and delineation of central nervous system (CNS) neoplasms resulting from increased injected doses of gadoteridol have the potential to be clinically significant and may justify the possibly higher cost of increased contrast material dosage. Lower doses may not be adequate for the evaluation of most CNS tumors.

Controversy exists regarding the optimal treatment for patients with multiple brain abscesses. These lesions are often small and located deep in the brain and close to vital structures, making surgery difficult. With this in mind the authors review their experience in treating multiple abscesses using computerized tomography (CT)-guided stereotaxic aspiration. From 1983 to 1985, 15 patients were treated for multiple brain abscesses, of whom eight underwent stereotaxic aspiration. There were a total of 28 abscesses in these eight patients: 11 abscesses were aspirated and two excised using CT-guided techniques. Most were cortical in location, although there were 12 in the deep white matter, one in the thalamus, and two in the caudate nucleus. All patients received a total of 6 weeks of antibiotic therapy. Follow-up CT showed resolution of the abscesses in all patients. Currently, four are neurologically normal, one has a mild hemiparesis, one has a well-controlled seizure disorder, and one requires supportive care. A single death occurred 5 weeks postoperatively of unrelated causes. Location, size, and age of an abscess all have bearing upon the response to management and outcome of the patient. Stereotaxic surgery is a procedure with minimal morbidity and mortality. Stereotaxic aspiration should be considered in patients with small, multiple, or deep-seated abscesses, in those who are poor operative candidates, and in those who have failed prior therapy.

Twenty-seven patients underwent 29 computerized tomography (CT)-guided stereotactic biopsy procedures for untreated or recurrent malignant astrocytomas. Biopsies were obtained from the hypodense center, enhancing margin, and hypodense periphery as seen on contrast-enhanced CT scans, with diagnostic yields of (number of biopsies yielding tumor/number of biopsies obtained): 34/61 (56%), 68/101 (67%), and 8/22 (36%) from these three zones, respectively. Although tumor was identified in all three zones, diagnostic yield was significantly higher in the hypodense center and enhancing margin. Comparison of patients with untreated tumors to those with recurrent tumors demonstrated no statistical difference in tumor distribution, although there was a trend toward a higher yield from the hypodense periphery in the recurrent tumor group. Tumor was found up to 15 mm beyond the CT-enhancing margin, in addition to extending beyond the area of abnormality on T2-weighted magnetic resonance images. These findings suggest that serial stereotactic biopsies should be targeted to the hypodense center and enhancing margin for improved diagnostic yield. Biopsy material obtained from the hypodense periphery that demonstrates tumor also indicates that a tumor volume beyond the confines of the CT-enhancing margin should be considered when calculating dosimetry for interstitial radiation.

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Previous studies of intracranial collateral circulation have not distinguished between true "collateral" blood flow (flow to a region that occurs only when a primary artery is occluded) and "overlap" flow (flow to a region that is present under both normal and demand conditions). These experiments had three purposes: 1) to identify tissues that were truly collateral dependent, 2) to determine potential for true collateral flow in the absence of overlap flow, and 3) to determine whether an anatomical basis for overlap flow could be demonstrated. Branches (700-900 microns) of the dog middle cerebral artery (MCA) were perfused with autologous blood. The perfused region, which was the area at risk, was identified by intravenous injection of neutral red dye. Microspheres were used to measure regional cerebral blood flow (rCBF). Overlap flow was determined by perfusion of the artery with microsphere-free blood. True collateral flow (total rCBF minus overlap flow) was determined by analysis of rCBF to the risk area after cessation of vessel perfusion. Most of the risk area had substantial levels of overlap flow (about one-third of base line). In the center of the area at risk, the true collateral-dependent area was identified [mean overlap flow 4 +/- 1 (mean +/- SE) ml.min-1.100 g-1], which had high levels of perfusion from collateral vessels (102 +/- 14) within 30 s of vascular occlusion. Microfil injection into two adjacent MCA branches showed discrete borders between vascular territories, with no overlapping vessels.(ABSTRACT TRUNCATED AT 250 WORDS)