Evaluation of image quality and lens's radiation dose of a low-dose cranial CT scan

Objective: To determine the lowest miliampere-second (mAs) of a cranial computed tomography (CT) scan that can maintain acceptable image quality on cranial CT scan which might help reducing the risk of cataract formation. Material and Method: The present study was performed on the 148 patients in routine daily practice sent for diagnosis of intracranial conditions by a cranial CT scan. During the cranial CT scanning, each lens's radiation dose on patient's eyes was measured by a thermoluminescent dosimeter. Clinical image quality, particularly in analysis of gray and white matter differentiation, was evaluated independently using a 5 point scale by two radiologists. Results: During standard cranial CT scan protocol with 250 miliampere-second (mAs), the total dose of left and right lens's dose were about 50.93 miligray (mGy) and 51.66 mGy, respectively. When applying low dose cranial CT scan protocols by decreasing mAs to 200, 150 and 100 mAs, the total dose of right and left lens were of 45.68 mGy and 46.04 mGy for 200 mAs, 34.65 mGy and 34.77 mGy for 150 mAs, 28.73 mGy and 29.25 mGy for 100 mAs respectively. Conclusion: A low dose cranial CT scan at 100 miliampere-second provides not only an acceptable clinical image quality, but also decreases the lens's radiation dose by 43%.