Development of an aperture-type radiation regulator for shielding against secondary radiation from x-ray tubes and collimators in computed tomography

Abstract

During computed tomography (CT) scans, radiation scatters in all directions, increasing radiation exposure. In this study, an aperture-type radiation regulator was developed to provide shielding against secondary radiation from the x-ray tube and collimator in CT. To evaluate the usefulness of the developed aperture-type radiation regulator, (1) spatial dose distribution within the CT room was measured, (2) dose intensity at 1 m from the isocenter was compared, (3) absorbed dose in the nearby organs was evaluated using a human equivalent phantom, and (4) noise, CNR, and SNR were compared for assessment of image quality. The results showed that the developed aperture-type radiation regulator reduced the intensity of secondary radiation by approximately 25% in front of the gantry and 15% to the rear of the gantry. The maximum dose distribution on 10 μGy was reduced by approximately 18% in front of the gantry and 12% in the rear. In addition, when the neck and head were scanned, the absorbed dose in the chest decreased by 25% and 40%, respectively, and noise was reduced by 3.3%–4.5% for different phantoms. Evaluation of abdominal CT images showed 18% noise reduction, with 27% and 28% increases in the signal-to-noise and contrast-to-noise ratios, respectively. These results confirmed that the proposed aperture-type radiation regulator can reduce radiation exposure without affecting primary radiation that creates medical images. The results also confirmed that the radiation regulator effectively improves the quality of medical images.