Issue |
Radioprotection
Volume 59, Number 1, January - March
|
|
---|---|---|
Page(s) | 50 - 54 | |
DOI | https://doi.org/10.1051/radiopro/2023047 | |
Published online | 15 March 2024 |
Article
Establishment of local diagnostic reference levels for breast cancer CT protocols in radiotherapy in a single Moroccan center
1
Ibn Tofail University, Faculty of Sciences, Department of Physics, laboratory of materials and subatomic physics, Kenitra, Morocco
2
Moulay Ismail University, Faculty of Sciences, Meknes, Morocco
3
National Institute of Oncology, University Hospital Center, Rabat, Morocco
4
Biophysics Laboratory, Life and Health Sciences Research Laboratory, Faculty of Medicine and Pharmacy of Tangier, Abdelmalek Essaâdi University
5
Mohammed V University, Faculty of Medecine and Pharmacy, Rabat, Morocco
6
Mohammed V University, National Graduate School of Arts and Crafts, Rabat, Morocco
* Corresponding author: nhila.oussama@gmail.com
Received:
28
August
2023
Accepted:
11
December
2023
The objective of this study was to establish local diagnostic reference levels (LDRLs) for breast cancer computed tomography imaging in radiotherapy (CT-RT) at a single hospital in Morocco. Data were collected from 106 adult breast cancer patients aged between 33 and 78 yr during five months. Data were obtained using a Hitachi Supria 16-slice CT simulator at a regional oncology center in Morocco. CT-RT images are intended for 3D conformal radiotherapy treatment planning. Dose length product (DLP) and volumetric computed tomography dose index (CTDIvol) were evaluated by determining the 75th percentile as diagnostic reference levels for CT-RT breast cancer. LDRLs for CT-RT breast cancer have been determined in terms of DLP and CTDIvol, and they were 330.4 mGy.cm and 6.8 mGy, respectively. The DRLs were compared with other Europeans study. DRLs for this study were lower than those for the United Kingdom (UK), Croatia and Slovenia. The results of this study can be a reference for the establishment of local and national DRLs in Morocco and the optimization of CT-RT breast cancer procedures.
Key words: DRL / Computed tomography / ALARA principle / breast cancer CT protocols
© SFRP, 2024
1 Introduction
The current global cancer data estimates that 19.3 million new cases were diagnosed in 2020. Most notably, breast cancer, with over 2.3 million cases reported in this year, was the most prevalent form of cancer (Sung et al., 2021). Morocco is also affected by this global scourge. The estimated number of new cancer cases per year is close to 50,000, of which breast cancer is the most frequently diagnosed among Moroccan women, accounting for 20% of all cancer cases, according to data from the country’s cancer registry (Ministry of Health, Morocco, 2020). Radiotherapy is an inherent integral part of oncology care. Thus, more than 60% of cancer patients receive radiotherapy as their principal treatment (Doury, 2019).
The most crucial and commonly used imaging modality in radiotherapy is CT (Computed Tomography) (Nhila et al., 2023). All patients receiving radiotherapy undergo dosimetric CT scans for treatment planning. Thus, the increase in cancer incidents implies a rise in the number of performed CT scans, which in turn leads to an increase in the number of individuals exposed to ionizing radiation from CT scans. Even if CT doses are considered well below therapeutic doses, they must be monitored and kept as low as possible (ALARA principal) (Clerkin, Brennan and Mullaney, 2018). According to the linear no-threshold model, all ionizing radiation imaging processes, including CT simulations for radiotherapy, must be optimized to reduce risks, especially for cancer patients with long life expectancies (Zalokar et al., 2020). Diagnostic reference levels (DRLs) are the most commonly used tool for optimizing and identifying unusually high doses to patients from radiological examinations (Paulo et al., 2020; Elnour et al., 2021). In fact, the principles of DRLs as a tool for the optimization of patient doses were first established in 1996 through ICRP publication 73 and were updated in publication 135 from the same institution in 2017 (Talbi et al., 2022). DRLs should not be considered a boundary between acceptable and unacceptable medical practices or as dose 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.
Minimum, Maximum and Mean values of different exposure parameters as well as CTDIvol and DLP.
25e percentile, Median and 75e percentile for CTDIvol and DLP at breast cancer CT-RT protocols.
Fig. 1 Distribution of CTDIvol values for CT-RT breast cancer. |
Fig. 2 Distribution of PDL values for CT-RT breast cancer. |
LDRLs for breast cancer CT-RT protocols in Morocco, compared to other DRLs.
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 changes to the radiation protection system. For this, Moroccan Agency for Nuclear and Radiological Safety and Security (AMSSNuR) is developing a regulatory project that consists of establishing and utilizing DRLs. This project has resulted in several published surveys of DRLs in different medical imaging modalities.
No previous study has been published on DRLs for CT protocols in radiotherapy in a Moroccan hospital. Therefore, the present study has been performed to establish local DRLs for breast cancer CT-RT protocols.
The results obtained show that the 75th percentile of CTDIvol and DLP for breast cancer CT-RT protocols are considerably lower than those of the European countries listed in Table 2. The UK comes closest to the DRLs in our study, with CTDIvol and PDL values of 10 mGy and 390 mGy.cm, respectively.
There are several possible reasons for these wide variations. The main reason seems the difference between CT protocols and scanner brands, and generations (Kumsa et al., 2023). In addition, disparities in operator training and experience, which vary from one country to another, may contribute to variations in exposure levels (Tahiri et al., 2022).
Moreover, even within the same country, significant dose differences may exist between centers, usually due to the lack of a standardized protocol. In some cases, the cause of these differences is difficult to explain. For instance, a study conducted to establish DRLs for the breast cancer CT-RT protocol by O’Connor et al.(O’connor, Ardle and Mullaney, 2016) concluded that significant dose differences between CT radiotherapy centers were unjustifiable.
When comparing the dosimetric indicators for CT-RT breast cancer in the UK with our own, we observed that despite the longer scan length values in this study (median value of 420 mm versus 280 mm), the DLP values are lower than those in the UK. Thus, when comparing the acquisition parameters published in the two surveys, it seems that the principal causes of the differences between CTDIvol and DLP relate to acquisition parameters affecting dose, such as FOV, mas, slice thickness and pitch as demonstrated in previous studies (Davis et al., 2018).
Worldwide data on DRLs for CT-RT breast cancer are scarce. Thus, even though the doses of our study are lower than those of previous studies, they seem insufficient to confirm the optimality of our results. In this context, we were required to compare the results of DRLs for CT-RT breast cancer against those of thoracic diagnostic CT protocols, similar to the study conducted by Connor et al.
In this context, for a complete analysis, it was necessary to compare the results of this study with those of our previous study, establishing LDRLs in Morocco for adult CT scans of different localizations, including the chest (El Mansouri et al., 2022). The results obtained show that the 75th percentile of CTDIvol and DLP of the chest CT were approximately twice as high (12.3 mGy and 632 mGy cm) as those proposed in the present study. This difference can be explained by the effect of acquisition parameters, notably kV and mAs settings, which have a significant effect on CTDIvol, as proven in previous studies (Elojeimy, Tipnis and Huda, 2010; El Mansouri et al., 2021; Talbi et al., 2021).
When comparing dose indicators between diagnostic CT scanners, kV setting and AEC mode can be major factors influencing results (Papadakis and Damilakis, 2018; Bebbington et al., 2021). However, in CT-RT protocols, practically all centers use 120 kV setting and avoid AEC technologies adjusting tube voltage to provide unchangeable conversion of attenuation coefficients to electron density, making this parameter insignificant.
4.1 Limitation and perspective
Firstly, the sample size for this study was limited, and patient weight data were not available, thereby making assessment of body size’s effect on the NRD value impossible. Secondly, DRL values were established in a single Moroccan center and included data from a single CT examination. Future studies could include other body examinations and variation of scanner brands in several hospitals. Finally, we have established DRLs for CT-RT breast cancer in order to optimize the risk of radiation-induced cancer, especially given the high radiosensitivity of the contralateral breast. Several studies have established DRLs for pediatric CT procedures (Bawazeer et al., 2022; Geryes et al., 2022; Akhlaghi et al., 2014), but as far as we know, no study has addressed DRLs for pediatric CT-RT protocols, and for this reason we would like to eventually explore this issue.
5 Conclusion
In recent years, researchers have approached the establishment of DRLs for CT-RT to provide a platform for dose comparison and optimization of CT procedures. To our knowledge, only a few European countries have been able to establish DRLs for the most common localizations such as pelvis, ORL, and Breast in their countries. This is the first Moroccan study to establish CT-RT breast cancer DRLs in a single institution. The local NRDs established showed good radiation protection practices in this hospital. Therefore, the results of this study could be a benchmark for the establishment of local and national DRLs in Morocco and the optimization of CT-RT breast cancer procedures.
Conflict of interest
The authors declare that they have no conflicts of interest in relation to this article.
Funding
There was no funding from any source for this study.
Ethical Approval
This study did not carry out activities that would require approval by a research ethics committee.
Informed consent
This article does not contain any studies involving human subjects.
Authors contributions
All authors contributed to the design and implementation of the research, to the analysis of the results and to the writing of the manuscript. All authors read and approved the final version of the paper.
References
- Aberle C, et al. 2020. Update of national diagnostic reference levels for adult CT in Switzerland and assessment of radiation dose reduction since 2010. Eur Radiol 30 (3): 1690–1700. https://doi.org/10.1007/s00330-019- 06485-1. [CrossRef] [PubMed] [Google Scholar]
- Akhlaghi P, Miri Hakimabad H, Rafat Motavalli L. 2014. An overview of exposure parameters, dose measurements and strategies for dose reduction in pediatric CT examinations. Radioprotection 49 (1): 9–15. https://doi.org/10.1051/radiopro/2013072. [CrossRef] [EDP Sciences] [Google Scholar]
- Bawazeer O, et al. 2022. Assessment of pediatric radiation doses in brain CT procedures. Radioprotection 57 (4): 305–310. https://doi.org/10.1051/RADIOPRO/2022027. [CrossRef] [EDP Sciences] [Google Scholar]
- Bebbington NA, et al. 2021. Validation of CARE kV automated tube voltage selection for PET-CT: PET quantification and CT radiation dose reduction in phantoms. EJNMMI Physics 8 (1): 1–14. https://doi.org/10.1186/S40658-021-00373-8/FIGURES/6. [CrossRef] [PubMed] [Google Scholar]
- Božanić A, et al. 2022. National reference levels of CT procedures dedicated for treatment planning in radiation oncology. Phys Med 96 (September 2021): 123–129. https://doi.org/10.1016/j.ejmp.2022.03.001. [CrossRef] [PubMed] [Google Scholar]
- Clerkin C, Brennan S, Mullaney LM. 2018. Establishment of national diagnostic reference levels (DRLs) for radiotherapy localisation computer tomography of the head and neck. Rep Pract Oncol Radiother 407–412. https://doi.org/10.1016/j.rpor.2018.07.012. [CrossRef] [PubMed] [Google Scholar]
- Damilakis J, et al. 2023. How to establish and use local diagnostic reference levels: an ESR EuroSafe Imaging expert statement. Insights Imaging 14 (1). https://doi.org/10.1186/s13244-023-01369-x. [CrossRef] [Google Scholar]
- Davis AT, et al. 2018. Assessment of the variation in CT scanner performance (image quality and Hounsfield units) with scan parameters, for image optimisation in radiotherapy treatment planning. Phys Med 45(May 2017): 198–204. https://doi.org/10.1016/j.ejmp.2017.11.036. [Google Scholar]
- Doury P. 2019. Benorylate Symposium, Helsinki, June 3, 1975. Closing remarks. Scand J Rheumatol Suppl 5 (13): 37–40. [Google Scholar]
- El Mansouri M, et al. 2021. Impact of tube voltage on radiation dose (CTDI) and image quality at chest CT examination. At Indones 47 (2): 105. https://doi.org/10.17146/aij.2021.1120. [CrossRef] [Google Scholar]
- El Mansouri M, et al. 2022. Establishing local diagnostic reference levels for adult computed tomography in Morocco. Radioprotection 57 (1): 61–66. https://doi.org/10.1051/radiopro/2021035. [CrossRef] [EDP Sciences] [Google Scholar]
- Elnour AR, et al. 2021. Estimation of radiation risk and establishment of diagnostic reference levels for patients undergoing computed tomography chest-abdomen-pelvic examinations in Sudan. Radiat Prot Dosim 196 (1-2): 104–109. https://doi.org/10.1093/RPD/NC AB136. [CrossRef] [PubMed] [Google Scholar]
- Elojeimy S, Tipnis S, Huda W. 2010. Relationship between radiographic techniques (kilovolt and milliampere-second) and CTDIvol. Radiat Prot Dosim 141 (1): 43–49. https://doi.org/10.1093/RPD/N CQ138. [CrossRef] [PubMed] [Google Scholar]
- Habib Geryes B, et al. 2022. Cumulative effective dose from imaging in infants with esophageal atresia: How low can we go? Radioprotection 57 (3): 201–208. https://doi.org/10.1051/RADIOPRO/2022015. [CrossRef] [EDP Sciences] [Google Scholar]
- Héliou R, Normandeau L, Beaudoin G. 2012. Towards dose reduction in CT: patient radiation dose assessment for CT examinations at university health center in Canada and comparison with national diagnostic reference levels. Radiat Prot Dosim 148 (2): 202–210. https://doi.org/10.1093/RPD/N CR024. [CrossRef] [PubMed] [Google Scholar]
- Hendrick RE. 2010. Radiation doses and cancer risks from breast imaging studies. Radiology 257 (1): 246–253. https://doi.org/10.1148/RADIOL 10100570. [CrossRef] [PubMed] [Google Scholar]
- IRSN Report. 2020. Analysis of data for updating diagnostic reference levels in radiology and nuclear medicine: 2016–2018 report, pp. 1–137. [Google Scholar]
- Kumsa MJ, et al. 2023. Establishment of local diagnostic reference levels for common adult CT examinations: a multicenter survey in Addis Ababa. BMC Med Imaging 1–9. https://doi.org/10.1186/s12880-023- 00963-1. [PubMed] [Google Scholar]
- Ministry of Health, Morocco. 2020 ; plan national du cancer de prévention et de contrôle’, xxx 2020 https://www.sante.gov.ma/Documents/2021/03/Plan_National_de_Prevention_et_de_Controle_du_Cancer_2020-2029_VF.pdf? csf=1&e=ejDjaj [Google Scholar]
- Nhila O, et al. 2023. The effect of CT reconstruction filter selection on Hounsfield units in radiotherapy treatment planning. J Radiother Pract 22. https://doi.org/10.1017/s1460396923000249. [CrossRef] [PubMed] [Google Scholar]
- O’connor S, Ardle OMC, Mullaney L. 2016. Establishment of national diagnostic reference levels for breast cancer CT protocols in radiation therapy. Brit J Radiol 89 (1066): 1–6. https://doi.org/10.1259/bjr 20160428. [Google Scholar]
- Papadakis AE, Damilakis J. 2019. Automatic tube current modulation and tube voltage selection in pediatric computed tomography a phantom study on radiation dose and image quality. Invest Radiol 54(5):265–272 https://doi.org/10.1097/RLI 0000000000000537. [Google Scholar]
- Paulo G, et al. 2020. Diagnostic reference levels based on clinical indications in computed tomography: a literature review. Insights Imaging 11 (1). https://doi.org/10.1186/s13244-020-00899-y. [CrossRef] [Google Scholar]
- Siiskonen T, et al. 2018. Establishing the European diagnostic reference levels for interventional cardiology. Phys Med 54(June): 42–48. https://doi.org/10.1016/j.ejmp.2018.09.012. [CrossRef] [PubMed] [Google Scholar]
- Sung H, et al. 2021. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 Countries. CA: A Cancer Journal for Clinicians 71 (3): 209–249. https://doi.org/10.3322/caac.21660. [CrossRef] [PubMed] [Google Scholar]
- Tahiri Z, Talbi M, El Mansouri M. 2022. Evaluation of Moroccan physician’s knowledge about radiation doses and risks from pediatric computed tomography. Radioprotection 57 (2): 123–126. https://doi.org/10.1051/RADIOPRO/2022007. [CrossRef] [EDP Sciences] [Google Scholar]
- Talbi M, et al. 2021. Estimation of computed tomography dose index (CTDI) using monte carlo simulation. Mosc Univ Phys Bull 76 (1): S103–S109. https://doi.org/10.3103/S0027134922010180/METRICS. [Google Scholar]
- Talbi M, et al. 2022a. Local diagnostic reference levels (LDRLs) for full-field digital mammography (FFDM) and digital breast tomosynthesis (DBT) procedures in Morocco. J Med Imaging Radiat Sci 53 (2): 242–247. https://doi.org/10.1016/j.jmir.2022.03.008. [CrossRef] [PubMed] [Google Scholar]
- Talbi M, et al. 2022b. Local diagnostic reference levels (LDRLs) for routine X-ray examinations in Morocco. Radioprotection 57 (2): 149–155. https://doi.org/10.1051/radiopro/2022008. [CrossRef] [EDP Sciences] [Google Scholar]
- Toroi P, Kaijaluoto S, Bly R. 2015. Patient exposure levels in radiotherapy CT simulations in Finland. Radiat Prot Dosim 167 (4): 602–607. https://doi.org/10.1093/rpd/ncu363. [CrossRef] [PubMed] [Google Scholar]
- Uushona V, et al. 2022. Establishment of regional diagnostic reference levels in adult computed tomography for four african countries: a preliminary survey. Radiat Prot Dosim 198 (7): 414–422. https://doi.org/10.1093/RPD/NC AC074. [CrossRef] [PubMed] [Google Scholar]
- Vañó E, et al. 2017. ICRP publication 135: diagnostic reference levels in medical imaging. Ann ICRP 46 (1): 1–144. https://doi.org/10.1177/0146645317717209. [Google Scholar]
- Wood TJ, et al. 2018. IPEM topical report: the first UK survey of dose indices from radiotherapy treatment planning computed tomography scans for adult patients. Phys Med Biol 63 (18). https://doi.org/10.1088/1361-6560/AA CC87. [Google Scholar]
- Zalokar N, Žager Marciuš V, Mekiš N. 2020. Establishment of national diagnostic reference levels for radiotherapy computed tomography simulation procedures in Slovenia, Eur J Radiol 127(March): 108979. https://doi.org/10.1016/j.ejrad.2020.108979. [CrossRef] [PubMed] [Google Scholar]
Cite this article as: Nhila O, Talbi M, Youssoufi MA, El Mansouri M, Tahiri Z, Chakir EM, Azougagh M. 2024. Establishment of local diagnostic reference levels for breast cancer CT protocols in radiotherapy in a single Moroccan center. Radioprotection 59(1): 50–54
All Tables
Minimum, Maximum and Mean values of different exposure parameters as well as CTDIvol and DLP.
25e percentile, Median and 75e percentile for CTDIvol and DLP at breast cancer CT-RT protocols.
All Figures
Fig. 1 Distribution of CTDIvol values for CT-RT breast cancer. |
|
In the text |
Fig. 2 Distribution of PDL values for CT-RT breast cancer. |
|
In the text |
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.