Radiation dose and risk estimation in pediatric head CT examination

Abstract

Pediatric CT study, an excellent imaging modality, has been increasing at about 10% per year. This has raised concerns because CT examinations deliver relatively high radiation dose compared to other X-ray diagnostic examinations. Children are much more sensitive to the damaging effects of ionizing radiation than adults and have a longer time to accumulate the radiation effect throughout their lives. This is a retrospective study in pediatric patients who underwent the CT brain at Siriraj Hospital between July and December 2011. 145 cases (79 boys: 66 girls) were divided into 4 age groups as follows: Group1 0-1 years 49 patients (22:27), Group II >1-5 years 40 cases (27:13), Group III >5-10 years 29 patients (18:11) and Group IV >10-15 years 27 patients (12:15). The effective dose has been determined from the multiplication of DLP and the conversion coefficient, mSv.mGy-1.cm-1 for head. The organ dose in brain, eye lens, salivary glands, skin and thyroid were determined by ImPACTSCAN software according to ICRP 103. Radiation risks have been estimated for stochastic effect from effective dose and deterministic effect from organ dose. The results show the effective dose of group I – IV was 0.769, 0.7356, 0.7357 and 0.764 mSv respectively. The radiation risks as related to the effective dose were 5.61, 5.37, 5.37 and 5.58 per 100,000 pediatric patients undergoing head CT examination. Highest risk in cancer is 3.85, 3.68, 3.68 and 3.82 per 100,000 pediatric patients undergoing head CT examination. Lowest risk in hereditary effect was 10, 9.56, 9.56 and 9.93 per 1,000,000 individuals undergoing head CT examination. Organ doses in the brain/salivary gland, eye lens, skin and thyroid in group I were 6.13, 6.36, 0.41 and 0.19, group II 8.61, 9.85, 0.65, 0.47, group III 14.29, 15.06, 0.97, 0.75 and group IV 17.67, 18.67, 1.46 and 0.99 respectively. In this study each organ dose in one series is less than 0.02 Gy, resulted that the risk from cataract was not possible as the occurrence of cataract threshold is 0.5 Gy. Therefore, the deterministic effects would not occur for pediatric patient undergoing head CT examination at Imaging Center, Siriraj Hospital. It could be concluded that pediatric patients undergoing head CT examinations should have a benefit exceeds the small radiation risk. The radiation dose values in pediatric in this study is a useful source of information for medical workers when explaining the effects of radiation to parents of pediatric patients on scientific basis. This study looks forward to concerns and draws attention to the fact that children are not 'small adults', should be practiced differently.