Effect of shielding thickness on eye dose and image quality from head computed tomography examination

Tumor detection in the head region involve high radiation doses, allowing the eye organs to be affected by radiation exposure. Shielding is required to protect the eye organs in order to receive the minimum radiation exposure. The shielding is designed from special materials that reduce the absorbed dose received by the eyes. This study aims to determine the effect of shielding thickness on the dose received by the eye and the image quality of CT scan results. Shielding from Silicon Rubber (SR)-Bismuth is fabricated with thickness variations of 0.5, 1.0 and 1.5 cm. The percentage of Bismuth addition is made at 0, 3, 5, and 10%. The results show the eye dose without shielding is 47.73 mGy and with shielding is 28.58 to 41.16 mGy only. The increased shielding thickness causes the eye dose to decrease by a maximum of 40.12%. The Hounsfield Unit (HU) value of SR-Bismuth shielding has a range of 328.76 - 3068.33 which indicates attenuation increases with the addition percentage of bismuth. Increasing the thickness of the shielding and the percentage of Bismuth causes the SNR value to decrease in both the eye and brain. The statistical test results for eye obtained p < 0.05 which means there is a significant difference between the phantom image without and with shielding, while for brain obtained p > 0.05, which means there is no significant difference between the phantom image without and with shielding. Increasing the thickness of the shielding and also the percentage of bismuth causes the HU value to increase, which means the eye dose decreases without reducing the image quality of the brain.