Cumulative organ dose and effective dose in adult population underwent repeated or multiple head CT examination

Abstract

The computed tomography (CT) scan is one of the most frequently used tool in diagnostic imaging. Thus, it has resulted in growing frequencies of multiple and repeated exposures of CT imaging that resulted in high cumulative doses to patients. In consequence, concern also raised among professionals and public on the potential radiation-related health effects received from repeated CT exposures. This study was aimed to evaluate the cumulative organ dose received from multiple exposures in adult patients underwent CT head examination. The retrospective dose survey was performed at Advanced Medical and Dental Institute (AMDI), Penang and Hospital Universiti Sains Malaysia (HUSM), Kelantan. A total of 203 adult patients received multiple CT exposures (3 times or more) were selected. Most of the patients that received multiple CT scans were referred from the Emergency and Neurosciences Departments of HUSM. The cumulative organ doses and effective dose from multiple CT exposures were estimated using CT ImPACT software. From the survey, most of the patients received 3 times of repeated head CT examinations with the highest frequency of repeated CT was 14 times. The highest equivalent dose was observed at eye lens with the value of 8.02 mSv for 14 CT exposures followed by bone marrow with dose values of 7.06 mSv. Based on the recommendation by International Commission on Radiological Protection (ICRP), the highest mean dose of 8.02 mSv received by the eye lens was considered at low risk which is 0.1–8.0% below the ICRP recommended value of 20 mSv. Besides, the absorbed dose to eye lens was also considered at low risk of developing radiation-induced cataract. However, the increasing numbers of repeated CT exposures contributed to the dose increment (p-value = 0.01). Moreover, the absorbed dose of the lens received after 4 exposures exceeded the range of 2 Gy of cataract risk with the M = 244.81, p = 0.01. Besides, the highest cumulative effective dose by simple calculation (32.1 mSv) and ImPACT calculation (43.8 mSv) were also differed significantly with p‒value of 0.01. The organ dose and effective dose associated with repeated CT exposures should be carefully observed and repeated examinations on the same patients should be justified to ensure the dose received by patient is as low as reasonably practicable.