SAN FRANCISCO – Comprehensive stroke imaging with whole-brain or nearly whole-brain CT perfusion exposes the patient to total radiation doses that are similar to or lower than those from standard comprehensive stroke CT imaging with partial brain perfusion coverage, according to a review of 200 consecutive patients.
State-of-the-art stroke CT imaging often includes head CT, brain CT perfusion, and CT angiography of the head and neck, which may be vital for accurate diagnosis and treatment but has raised concerns about radiation exposure, Dr. Jack C. Rose explained in a poster presentation at the annual meeting of the American Neurological Association.
Dr. Rose and his colleagues at the California Pacific Medical Center, San Francisco, compared the radiation doses that patients received at their institution before and after the center switched from using the volume shuttle (nearly whole-brain) CT perfusion technique to an optimized volume helical shuttle technique. They also compared the doses with historical data from other investigators using more conventional techniques.
In 57 patients who were imaged with the volume shuttle technique, the mean total dose-length product was 7,048 mGy-cm and the mean effective dose was 16 mSv. These levels are within U.S. Food and Drug Administration safety guidelines (CT dose index volume, 0.5 Gy or less) and comparable to 6,790 mGy-cm and 16 mSv means reported from similar comprehensive stroke CT imaging with more limited CT perfusion coverage in a separate cohort of 95 patients (Neuroradiology 2009;51:635-40).
In 143 patients who were imaged with a volume helical shuttle (whole-brain) CT perfusion technique, the mean total dose-length product (6,721 mGy-cm) and effective dose (15 mSv) were 5%-6% lower than levels in the patients who underwent volume shuttle CT perfusion.
A conventional 64-slice CT scanner was used for imaging. The volume shuttle provided 8 cm of CT perfusion coverage, and the volume helical shuttle provided 14 cm of perfusion coverage. The radiation dose with the volume helical shuttle technique was minimized by limiting the maximum tube current to 350 mA.
Dr. Rose reported that the investigators have no potential conflicts of interest, except that one of his associates is a speaker for Genentech Inc.