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Optimization of Timing and Positioning of the Technetium Brain Scan

University of Cincinnati, Cincinnati, Ohio

ABSTRACT

Kinetic studies were performed with intravenous pertechnetate in 20 essentially normal individuals. Counting rates over the brain followed a consistent pattern which is described and compared with the decline in blood counts. At 30 mm the observed brain counting rate was 89% of the plateau level and was falling at a single exponential rate with a half-time of 160 min. The ratio of counts recorded over the brain to counts in peripheral blood rose to a maximum 30–60 mm after injection. This change in ratio and the observation that some neoplasms are not distinguishable before 30 min make it reasonable to insist on a waiting period of at least 30 min before examining the injected patient. In patients with suspected A-V malformations early views (0–5 min) are of value because late photos may not show the lesion. Spuriously positive scintiphotographs are easily obtained by imperfect positioning, largely because of the accentuation of superficial activity. Recommendations for routine and special views are given.