A survey of paediatric computed tomography radiation doses in two selected hospitals in Kampala, Uganda, a radiation protection concern

Abstract

Background Optimization of radiation doses during medical exposures especially in paediatrics is a basic safety requirement. Computed Tomography (CT) scan used in paediatrics is a major radiation protection concern throughout the world due to the following three primary factors; increased sensitivity, higher effective dose, and increasing use. The assessment of CT radiation doses imparted during CT scan examinations entails estimation of essential CT radiation dose descriptors, i.e. Weighted CT dose index (CTDIw) and Dose Length Product (DLP).

General Objective The over-all aim of this study was to establish the radiation dose imparted to paediatric patients during CT scan examinations through estimation of CTDIw and DLP, as well as to describe the distribution of children undergoing CT scan examination in Mulago National Referral Hospital (MNRH) and Kampala Hospital Limited (KHL).

Method This was a cross-sectional survey carried out in MNRH and KHL, between December 2012 and February, 2013. Demographic data and acquisition parameters of 257 CT scan examinations performed on pediatric patients were collected from request forms and CT scan consoles. The values of CTDIw, CTDIvol and DLP were calculated using ImPACT (Imaging Performance and Assessment of Computed Tomography) dosimetry software for Philips MX-1800 scanner of MNRH and GE Hispeed Dual scanner of KHL. Data was analyzed using mean, range, 3rd quartile, as well as chi square. Frequency tables and histograms were used to summarize the data.

Results The majority of paediatric CT scan examinations were performed on children in the age group 0-4 years and 10-14 years for KHL and MNRH, respectively. The male to female ratio was 1:1 for both the hospitals. The majority (46% MNRH and 40% KHL) of CT procedures were performed to evaluate head injuries. The highest mean values for CTDIw (43 mGy), CTDIvol (71 mGy) as well as DLP (1336 mGy.cm) were recorded for head CT scan examinations performed on older children (15-17 years) in MNRH. The values of CTDIw, CTDIvol as well as DLP for the multi-slice CT scanner used in MNRH were significantly higher when compared to the dual slice CT scanner in KHL. All CT dosimetric values of MNRH were relatively high when compared to the values reported from other countries as well the European Commission. Conclusion The main aim of all CT scan examinations especially in children is to have maximum diagnostic benefit and less radiation dose. This study has indicated a stronger need to justify CT examinations as well as use of lower radiation doses in children in view of radiation protection concern. Formulation of appropriate paediatric protocols as well as awareness among the CT users and the refereeing clinicians is crucial for use of CT scan as an accurate, appropriate and safe diagnostic tool in children. Recommendation • There is a need to establish paediatric protocol for CT scan examination especially keeping the age and weight of the children in mind at MNRH • There is need to generate awareness about radiation protection in children among the CT users and policy developers. • There is need to formulate a national, internal and external quality control and assurance scheme for Uganda. • Further studies have to be done in the future which would include a larger sample size of paediatric CT scan examinations performed on the chest and abdomen. • Further studies to establish the effect of tube current ,kilo voltage peak , slice thickness and pitch on diagnostic image quality in paediatric CT scan examinations should be done. • Developing countries should establish independent CT dosimetric values before purchasing the machines