Clinical verification of possibility of dose reduction in CT scanning of the brain

Computed tomography is a significant source of the population's exposure to ionizing radiation. Clinical verification of the possibility of patient dose reduction in CT scanning of the brain was the aim of this study. A Siemens Somatom AR Star was used in the investigations. First, image quality indicators (contrast and spatial resolution) were analyzed in relation to the intensity of the scanning x-ray beam using a Catphan phantom. Dosimetric evaluation was also performed. The clinical study involved examination of the brains of 100 patients. Nine details of the image important in diagnostics were analyzed.The routine anode current value was applied in 50 patients, while the other 50 received a reduced value. The diagnostic images were evaluated by two independent radiologists who did not know the parameters used during the examinations.To make the results objective, semiquantitative analysis was used. A reduction in the anode current from 105 mA to 63 mA did not deteriorate the visualization of low-contrast objects; only the size of the smallest detectable object was slightly greater (minimal deterioration of the contrast resolution). The diagnostic images obtained with the routinely used and the reduced anode current values did not show significant differences in the visualization of the selected image details. CT examinations of the brain can be performed at a reduced anode current with no loss of the diagnostic significance of the examination. The dose to the patient is reduced by 40% when the modified protocol is implemented. (author)