Radiation dose reference levels of adult patient computer tomography abdominal studies in Eldoret.

Abstract

Background: Computed Tomography (CT) is a medical imaging technique that uses X-rays to produce detailed images of the body. CT procedures contribute to 67% of the collective effective radiation due to medical procedures in the United Kingdom and United States of America. CT abdomen is one of the commonest examinations done and its international approximate effective dose is 8mSv. Radiation dose of 10mSv and above carry higher risks of radiation induced injuries. The International Commission on Radiological Protection (ICRP) in concert with International Atomic Energy Agency (IAEA) introduced a concept called Diagnostic Reference levels (DRL) with the objective of providing a reference level for the radiation dose for standard radiographic and CT examinations without compromising quality of the images and ensuring radiation safety. Diagnostic reference levels are established locally, regionally and nationally. It is primarily useful as a quality assurance tool to compare doses from different protocols and to compare scanner outputs from different manufacturers. The international DRL for adult abdominal scans as per European commission, Ireland, Japan, India, shows the Computed Tomography Dose Index (CTDIvol)(mGy), and (Dose Length Product) DLP (mGy.m) values at (35, 780), (13,1120), (30.8, 1180.5), (13.71,2336.4) respectively. In recent regional and local studies in Africa, Egypt, Nigeria, South Africa, and Tanzania estimated the adult abdominal DRLs (CTDIvol(mGy) & DLP (mGy.m)) to be (11.9–22.7,341-1314), (31,1325), (15. 716) (22.7,704) respectively. The international diagnostic reference levels (DRLs) are used as point of reference and so far, no regional protocols for abdominal CT scan have been adopted. Objective: To assess radiation dose reference levels of adult abdominal CT at MTRH, St. Luke’s Hospital, Eldoret Hospital and Mediheal Hospital. Methods: A multi-center retrospective study conducted in institutions from Eldoret with a functional radiology department doing an average of 15 abdominal CT scans per day as basis of selection namely; MTRH, Eldoret Hospital, Mediheal Hospital and St. Luke’s Hospital in a period of 6 months in the year 2021. The adult patients’ radiation dose data that were 18 years and above and referred for abdominal CT-scan during the period of study were recruited. Incomplete radiation dose summary for any patient was excluded. Consecutive sampling was applied to the 3 private facilities while systematic sampling using the interval K ~2 was used in MTRH which is a public facility. The CTDIvol and DLP from CT abdominal scans for the adults were simply obtained from the various CT machines as displayed on the console and recorded into an adapted IAEA survey form. The data was analyzed statistically via calculation of the median, interquartile ranges and construction of confidence intervals. The results were presented in tables and figures. Results: A total of 700 patient abdominal dose scans were reviewed. The age ranged from 18-101 years with a mean of 52 years with the majority being females at 53 % of patients who underwent CT abdominal scans. It was observed that 66.4% of the reviewed scans were from the public facility and Siemens was the most common scan model at 70%. The mean CTDIvol was 8.1mGy (SD=22.2) and the mean DLP values was 1699.1mGy.cm (SD=1053.1). Comparison by the type of scan model indicated that the median for the Total DLP and CTDIvol significantly differed by the model with the median for the Neusoft model being highest at 2538 mGy.cm and 10.3mGy respectively while those for the Siemens were the lowest for the two markers at 1318.5 mGy.cm for the DLP and 5.39mGy respectively. Comparison by the type of facility showed that the median DLP and CTDIvol values were significantly higher in the public facility at 1668.8mGy.cm and 6.3mGy respectively when compared to private facilities at 1282.4mGy.cm and 5.9mGy with a p value of <0.001. The average volume CTDIvol for the current study was lower than the reference countries by less than 3%. The DLP values in this study were approximately lower than the regional and comparable with most reference countries by over 50%. The Local Dose reference level (LDRL) was set as the median value for CTDIVOL and DLP at 6.1mGy and 1465 mGy.cm respectively. Conclusions: The LDRLs values were markedly lower than the regional and the international values. Recommendations: The current LDRLs can be adopted and maintained by both the private and public facilities.