Evaluation of an on-line patient exposure meter in neuroradiology

PURPOSE: To assess the clinical performance and usefulness of an on-line patient exposure meter installed on a neuroradiologic biplane imaging system. MATERIALS AND METHODS: A commercial on-line patient exposure meter was installed on each plane of a biplane neuroradiologic imaging system. The meter computed skin exposures on the basis of selected technique factors (tube potential and current) and information about patient location relative to the x-ray tube. Simulations were performed to measure the system accuracy with an angiographic anthropomorphic head phantom with the skin exposures measured with an ionization chamber. Skin doses were computed for 114 consecutive patients who underwent diagnostic and interventional neuroradiologic procedures. RESULTS: Agreement between measured and computed skin exposures in fluoroscopy, plain radiography, and digital imaging was generally within 5% of the true skin dose. For all fluoroscopic and radiographic procedures, total median skin doses were 1.20 and 0.64 Gy for the frontal and lateral planes, respectively. In bath planes, patient skin doses resulted primarily from digital subtraction angiographic acquisitions. In 29 (25%) patients, the skin dose exceeded 2.00 Gy, but no radiation-induced deterministic effects were observed. CONCLUSION: An on-line patient exposure meter can provide accurate radiation skin dose data in patients undergoing diagnostic and therapeutic neuroradiologic procedures.