A local dose management system for brain computed tomography in Nigeria

Abstract

Background: Computed Tomography (CT) constitutes 6.3% of medical X-ray procedures, however, this essential imaging tool represents the highest contribution (43.2%) of artificial human exposure to ionising radiation. Modern CT technology has made radiological equipment more efficient, with the ability to produce high-quality diagnostic images with lower radiation doses. However, accumulated exposure to ionising radiation has the potential to result in radiation side effects and injuries; even cancer induction. Therefore, there is a need to ensure that justification and optimisation principles are successfully applied in clinical practice to prevent the likelihood of radiation injury. AIM: The study developed and implemented the first prospective manual Radiation Dose Management System (RDMS) for brain CT procedures in a busy CT centre in Nigeria. This is to promote the concept of dose justification and optimisation in medical imaging. Methods: The study was conducted in a CT centre located at a tertiary hospital in Nigeria. The research was carried out in phases starting with a systematic literature review on RDMSs to determine the most appropriate RDMS for this site. Articles on RDMS were sourced from PubMed, EBSCOhost, Web of Science, SCOPUS and Cochrane Library databases. The articles were screened for review using the preferred reporting items for systematic review and meta-analysis flow chart. Thereafter, a questionnaire-based study using a convenience sampling method investigated the knowledge of CT dose optimisation and justification among 50% (17 out of 34) radiographers, 35% (16 out of 46) radiologists and 84% (92 out of 110) referring physicians. Findings from these two studies were used in developing and implementing a manual RDMS. This instrument was used to prospectively track and monitor the radiation dose and scan parameters of patients having brain CT. The data extracted from the screened articles in the systematic review was synthesised narratively. Meanwhile, data from the questionnaire and RDMS phases were analysed using the Statistical Package for Social Sciences (SPSS) version 20. The tracked doses were analysed in mean, median and 3rd quartile. These values were checked to determine compliance with the established national and international Diagnostic Reference Levels (DRLs). Results: A total of 38 articles were selected and synthesised narratively. The results revealed that there are electronic and manual RDMS and provided an indication of their strengths and weaknesses for given environments. The questionnaire-based study showed that more radiographers (47.1%) than radiologists (18.8%) had good knowledge of CT doses and image quality. However, the difference in knowledge was not found to be significant (p = 0.167) which could be ascribed to the small sample size of the participants. In addition, knowledge of diagnostic reference levels (DRLs) was significantly (p = 0.033) higher amongst radiographers (52.9%) as compared to radiologists (12.5%). Meanwhile, physicians understood the principles of dose justification. However, their knowledge of referral guidelines was limited. The developed and implemented RDMS tracked and monitored radiation doses of 596 patients for brain CT scans grouped as <1 year: 36 (6%); 1-<5 years: 38 (7%); 5-<10 years: 25 (4%); 10-<15 years: 31 (5%) and adult (>15 years): 466 (78%). Patients identified with high doses above the Volume Computed Tomography Dose Index (CTDIvol) notification were as follows: <1 year: 1 (2.8%), 1-<5: 1 (2.6%), 5-<10: 0 (0%), 10-<15: 0 (0%) and adult (>15 years): 11 (2.4%). Furthermore, examinations with doses above the Dose Length Product (DLP) notification value were as follows:<1 year: 1 (2.8%); 1-<5:1 (2.6%); 5-<10:1 (4%); 10-<15: 1 (3.2%) and adults (>15 years): 18 (3.9%). The established typical paediatric DLP values were two-three times higher than the international paediatric DLP DRLs. Conclusion: This thesis has for the first time, developed and implemented a manual RDMS specifically for brain CT examinations in a busy centre in Nigeria. Findings from the systematic literature review and questionnaire studies culminated in the development and implementation of this RDMS. The developed RDMS provided prospective assessment and records of patient scan parameters and dosimetric information which indicates patient procedures where the dose value is above the locally established notification values in CTDIvol and DLP. Furthermore, the dose record shows that the paediatric DLP DRLs were two to three times higher than the international paediatric DLP DRLs. This calls for total protocol review and optimisation, considering the local CT centre’s needs and practices for paediatric imaging.