Abstract
CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR. Patients radiation protection must therefore be increased during CT-scan procedures. This requires the rigorous application of optimization principle which imposes to have “diagnostic reference levels”. Objective: The aim of this study was to determine the diagnostic reference levels (DRLs) of the four most frequent CT-scans examinations of adults in Cameroon. Material and Method: It was a cross-sectional pilot study carried out from April to September 2015 in five health facilities using CT-scan in Cameroon. The studied variables were: patients age and sex, type of CT-scan examination (cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IV﹣/ IV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch, thickness of slices, CTDIvol and DLP. For each type of examination, at least 30 patients were included per center, consecutively on the randomly predetermined days. The DRL for each type of examination was defined as the 75th percentile of its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were cerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The mean age of patients was 52 ± 15 years [20 - 90 years], 58.9% were 50 years and older. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16 multidetectors. The 75th percentile of DLP or DRLs [standard deviation] was: [1150 ± 278 mGy·cm], [770 ± 477 mGy·cm], [720 ± 170 mGy·cm] and [715 ± 187 mGy·cm] respectively for cerebral, lumbar spine, abdominopelvic and chest CT-scans. Taking in consideration the number of detectors, the 75th percentile of the Dose-Length product decreased with the increase number of detectors for cerebral examinations but was the highest with 16 MDCT for the abdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar spine examinations, there was a significant increase in patient-dose with the increase in the number of detectors. Conclusion: Our DRLs values lie between the norms of some European countries and those of some African countries. There is remarquable variation in dose for the commonest CT-scans examinations in Cameroon, requiring then an optimization process from these determined DRLs and establishment of national DRLs. Special attention to optimization should be paid when using 16 MDCT.
Highlights
Computed tomography (CT-scan) is known as the most important medical cause of human exposure due to ionizing radiations in diagnostic radiology
For 5% - 10% of diagnostic X-ray procedures, it is responsible for 34% of irradiation according to UNSCEAR
Patients radiation protection must be increased during CT-scan procedures
Summary
Computed tomography (CT-scan) is known as the most important medical cause of human exposure due to ionizing radiations in diagnostic radiology. In its 2008 annual report, the UN Scientific Committee (UNSCEAR) estimated that, on a global scale, CT-scans accounted for only 5% of medical imaging examinations (versus 27% for chest X-rays) but contributed 34% to the annual collective dose (3% for chest x-ray) [1]. Patients radiation protection must be increased during CT-scan procedures. With rapid and constant technological developments, CT-scan has become the most requested examination in numerous clinical situations. Some indications, such as pretherapethic workup of various malignant tumors and total bodyscan, require the exploration of several regions of the body, and the increase of patient-dose [2]. Sub-Saharan Africa countries as Cameroon experienced the increase number of CT-scan machines in public and private health facilities. In 2016 more than 20 CT machines are available in Cameroon compare to five in 2004
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