Diagnostic Reference Levels of Adults CT-Scan Imaging in Cameroon: A Pilot Study of Four Commonest CT-Protocols in Five Radiology Departments

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. •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 CTscans 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.

Adult Computed Tomography examinations in Uganda: Towards determining the National Diagnostic Reference Levels

“…The volume CTDI is comparable to the Kenyan study of 2015 but lower than the European comparisons. These DRL findings were higher than all the comparisons [ 6 , 11 – 15 , 19 , 22 ]. This being the first nationwide study in Uganda, these variations are expected because of the differences in machines, lack of standardized protocols, wide variations in experience and training amongst the various CT radiographers and no National DRLs as a benchmark.…”

“…The volume CTDI was lower than the regional and international studies; the DLP was lower than some of the African studies but comparable so a couple of European studies. For abdominal CT scan examination, the average volume CTDI and DLP estimates were 12.54 mGy and 1418.3 mGycm, respectively; the volume CTDI was lower than all the comparisons, however the DLP was way higher than other studies [ 6 , 11 – 15 , 19 , 22 – 24 ]. The average volume CTDI and DLP estimates for lumbar spine CT were 19.48 mGy and 843.8 mGycm, respectively.…”

Comparison of Radiation Dose in CT Examinations At PIMS with European Commission Reference Doses

“…With regards to the analysis of scan length (mentioned in Tables II-III), all the regional multiphasic exams demonstrated less than double mean length compared to their monophasic counterparts, except for abdomenpelvis scans, wherein a higher proportion of three or more phase studies imparted by liver & KUB protocols resulted in more than double multiphasic mean scan length when compared to their single-phase counterparts. In table IV, a -AD = achievable dose (median value); DRL = Diagnostic reference level b -cervical spine protocol for fractures was utilized mean scan length values from our institution were compared with other international studies 15,[19][20] , revealing that the head and chest region scan lengths were similar, while those of abdomen-pelvis and neck region were 2-2.5 times higher than those of other countries, which likely explains the significantly higher dose values observed for these regions at our institution. Table V summarizes our proposed diagnostic reference levels (75th percentile value) and proposed achievable dose (50th percentile value) for dose metrics organized according to anatomical regions, inclusive of all phases & sub-regions, alongside results from other countries and regional DRLs.…”

Radiation doses during computed tomography scan imaging in Hassan II Hospital, Agadir, Morocco

“…Apart from the thoracic abdomino-pelvic procedure, our DRL values are superior to those established by other countries such as the United Kingdom (2014), France (2016), China (2019), and Belgium (2020) [ 4 , 27 - 29 ]. Furthermore, our DRLs for chest CT-scan, are lower than those in Cameroon (2017) [ 30 ]. Consequently, our patient-doses DRLs are between those of industrialized countries with advanced facilities and advanced cultures of optimization, such as China, the United Kingdom, France, and Belgium, and DRLs of an African country such as Cameroon.…”

“…Radiologists should methodically add DLP notification on radiological reports for patient radioprotection reasons [ 31 ]. On lumbar spine CT scans, higher DRLs have been seen in Belgium, China, the United Kingdom, France, and Cameroon [ 4 , 27 - 30 ]; this is due to the presence of multiple high attenuating bone structures in the spine, which necessitates the use of large doses to provide satisfactory image quality. We have evaluated the first results of DRLs, which can already be used for optimization while we wait for a national survey to assess the DRLs with the help of competent authorities.…”