CT-scan is the most irradiating tool in diagnostic radiology. For 5% - 10% of\ndiagnostic X-ray procedures, it is responsible for 34% of irradiation according\nto UNSCEAR. Patients radiation protection must therefore be increased during\nCT-scan procedures. This requires the rigorous application of optimization\nprinciple which imposes to have ââ?¬Å?diagnostic reference levelsââ?¬Â. Objective: The\naim of this study was to determine the diagnostic reference levels (DRLs) of the\nfour most frequent CT-scans examinations of adults in Cameroon. Material\nand Method: It was a cross-sectional pilot study carried out from April to\nSeptember 2015 in five health facilities using CT-scan in Cameroon. The\nstudied variables were: patients age and sex, type of CT-scan examination\n(cerebral, chest, abdomino-pelvic, lumbar spine), Used of IV contrast (IVâË?â??/\nIV+), acquisition length, time of tube rotation, voltage (kV), mAs, pitch,\nthickness of slices, CTDIvol and DLP. For each type of examination, at least 30\npatients were included per center, consecutively on the randomly predetermined\ndays. The DRL for each type of examination was defined as the 75th percentile\nof its PDL and CTDIvol. Results: Of the 696 examinations, 41.2% were\ncerebral, 26.9% abdomino-pelvic, 17.7% lumbar spine and 14.2% chest. The\nmean age of patients was 52 Ã?± 15 years [20 - 90 years], 58.9% were 50 years and\nolder. The sex-ratio was 1.26 (55.9% males). The CT machines were 4, 8 and 16\nmultidetectors. The 75th percentile of DLP or DRLs [standard deviation] was:2\n[1150 Ã?± 278 mGyâË?â?¢cm], [770 Ã?± 477 mGyâË?â?¢cm], [720 Ã?± 170 mGyâË?â?¢cm] and [715 Ã?±\n187 mGyâË?â?¢cm] respectively for cerebral, lumbar spine, abdominopelvic and\nchest CT-scans. Taking in consideration the number of detectors, the 75th\npercentile of the Dose-Length product decreased with the increase number of\ndetectors for cerebral examinations but was the highest with 16 MDCT for the\nabdominopelvic, lumbar spine and chest CT-scans. For the chest and lumbar\nspine examinations, there was a significant increase in patient-dose with the\nincrease in the number of detectors. Conclusion: Our DRLs values lie between\nthe norms of some European countries and those of some African\ncountries. There is remarquable variation in dose for the commonest CTscans\nexaminations in Cameroon, requiring then an optimization process\nfrom these determined DRLs and establishment of national DRLs. Special\nattention to optimization should be paid when using 16 MDCT.
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