Radioprotection No 59-1 | Page 57

O . Nhila et al .: Radioprotection 2024 , 59 ( 1 ), 50 – 54 51

Table 1 . Minimum , Maximum and Mean values of different exposure parameters as well as CTDIvol and DLP .

limits ( Vañó et al ., 2017 ). Instead , their purpose is to prevent individuals from receiving excessive doses of radiation that provide no additional clinical benefit ( Damilakis et al ., 2023 ). In order to remain consistent with evolving practices and standards , DRLs must be periodically updated in all countries ( Siiskonen et al ., 2018 ; El Mansouri et al ., 2022 ). DRLs are based on CTDIvol and DLP values at the 75th percentile ( Uushona et al ., 2022 ). For an optimal trade-off between the benefits and drawbacks of CT scanners , hospitals are recommended to make the most of the updated ( Aberle et al ., 2020 ). Although recent studies have determined DRLs for dosimetric scanners for different radiotherapy localizations ( Toroi et al ., 2015 ; O ’ connor et al ., 2016 ; O ’ connor , Ardle et al ., 2016 ; Clerkin et al ., 2018 ; Zalokar et al ., 2020 ; Božanić et al ., 2022 ), they are very few compared with DRLs for diagnostic CT scanners . No studies of this type have been published in Africa , and particularly in Morocco .

The Institute for Radiation Protection and Nuclear Safety ( IRSN ) suggests conducting regular assessments of patient doses in medical facilities for common radiological procedures ( IRSN Report , 2020 ). These doses should be compared to national and international reference levels ( Héliou et al ., 2012 ; Talbi et al ., 2022 ). If the results consistently exceed these levels , the facility must review its procedures and inspect its facilities . Thus , if the excess is not justified , corrective action should be applied ( Hendrick , 2010 ).

This survey aims to establish local ( institutional ) DRLs for breast cancer CT-RT at a single hospital in Morocco and to compare them with national DRLs in European countries .

2 Materials and methods

Data were collected for 5 months ( from 19 January 2023 to 20 June 2023 ) from a single simulator scanner ( Hitachi , Supria , 16-slice ) installed in a regional oncology center in Morocco . Data collection was prospectively performed , because the operators do not record all patient information , such as weight .

106 data were collected from adult patients between 33 and 78 yr of age who underwent CT-RT imaging with breast cancer protocols . These protocols are intended for 3D conformal treatment planning . In addition , data were acquired for patients undergoing CT-RT for curative breast radiotherapy and post-mastectomy and patients receiving supraclavicular lymph nodes radiotherapy . Also , data collection did not lead to additional radiation exposure to patients or affect the facility ’ s workflow . The data collected included : tube voltage ( kV ), tube current ( mAs ), slice thickness , rotation time , pitch , scan length , field of view ( FOV ), as well as CTDIvol and DLP .

Image quality control is not verified at this center , but all CT-RT images for breast localization were verified and approved by Radiation oncologists after confirming their suitability for volume delineation . Also , the delineation of the clinical target volume ( CTV ), which includes the conservative breast or chest wall and supraclavicular nodal regions as well as organs at risk ( OAR ), was defined according to the Radiation Therapy Oncology Group ( RTOG ) protocol .

2.1 Data analysis

The data collected were evaluated using software ( IBM SPSS Statistics version 22 ) as quantitative variables , which are represented by arithmetic mean , a first quartile ( 25th percentile ), a median ( 50th percentile ), and a third quartile ( 75th percentile ) ( Vañó et al ., 2017 ). Moreover , the DRLs established in this study were compared with those of other European countries such as the ( United Kingdom ) UK ( Wood et al ., 2018 ), Slovenia ( Božanić et al ., 2022 ), and Croatia ( Zalokar et al ., 2020 ).

3 Results

Table 1 shows the acquisition parameters adopted in the breast cancer CT-RT protocol , such as kV , pitch , rotation time , slice thickness , and reconstruction filter , which are constant for all patients . Thus , the same table shows the minimum and maximum values and means of parameters that vary according to the patient , such as mAs , FOV , scan length , as well as CTDIvol and DLP . The minimum CTDIvol value collected was 4.6 mGy and the maximum value was 21.2 mGy . As for DLP , 209 mGy . cm was the minimum value and 1267 mGy . cm was the maximum value .

Table 2 shows the 25th percentile , median , and 75th percentile values of the dosimetric indicators in terms of CTDIvol and DLP of CT-RT breast cancer . Also , the LDRLs are also shown graphically in Figures 1 and 2 , and represent the 75th percentiles of the CTDIvol and DLP distributions .

The established DRLs from this study were compared with other DRLs conducted in Uk ( Wood et al ., 2018 ), Croatia ( Božanić et al ., 2022 ), and Slovenia ( Zalokar et al ., 2020 ) as shown in Table 3 .

4 Discussion

Morocco has recently enacted a comprehensive reform of its health system , which includes the adoption of new laws and regulations designed to increase access to health services , ensure better patient care , and adhere to safety standards set by international organizations . This reform has also included