Publication ahead of print
Journal
Radioprotection
DOI https://doi.org/10.1051/radiopro/2022008
Published online 11 March 2022

© SFRP, 2022

1 Introduction

Morocco has launched a comprehensive reform of the health system, based on the establishment of a new governance system aimed at strengthening the mechanisms of legislation and control of healthcare professionals work and consolidating hospital governance and territorial planning of health care provisions, with the objective of increasing access to health services and ensuring better patient care while meeting the safety standards recommended by international organizations (Conseil de Gouvernement, 2021). In addition, the Moroccan radiation protection system has undergone several changes in recent years, following the adoption of the new law no142-12 (Loi no142-12 – SGGM, 2014). Also, the radiation protection of patients undergoing medical imaging examinations using ionizing radiation sources is now governed by specific provisions of Chapter VII of Law no142-12 (Loi no142-12 – SGGM, 2014). The principle of justification of procedures and the principle of optimization of doses delivered constitute the basis of the legislation governing medical exposure. The establishment and use of Diagnostic Reference Levels (DRLs) is among the regulatory projects being developed by the Moroccan Agency for Nuclear and Radiological Safety and Security (AMSSNuR). These DRLs will provide a useful tool for users to evaluate their practice, and will enable Morocco to comply with international requirements for patient radiation protection. The DRLs were first adopted and developed by the International Commission on Radiological Protection (ICRP) in its Publication 73 in 1996, and are updated in Publication 135 in 2017 (ICRP, 1996; Vañó et al., 2017). An unjustified dose that exceeds the corresponding DRL value indicates that the procedure is not performed at an optimized level concerning the amount of radiation used (Dreuil and Etard, 2017). Thus, DRLs are an important optimization process, they are used as dosimetric indicators for the evaluation of the quality of facilities and procedures and the recognition of unusually high patient doses in diagnostic examinations (Vañó et al., 2017; Tsapaki, 2020; Motlagh et al., 2020). DRLs are defined for different types of equipment and examinations in groups of patients according to their age range and weight and height. In general, the establishment of DRLs is performed for all of the most common radiological procedure modalities and for high-dose procedures. The implementation of DRLs automatically puts pressure on the quarter of providers with the highest radiation levels, since the DRLs are set at the 75th percentile of the dose distribution of standard examination types. DRLs are neither exposure limits nor optimal values and do not apply to individual exposures (Dreuil and Etard, 2017; Roch et al., 2018a, 2018b).

Several studies have shown the importance of establishing Diagnostic Reference Levels as tools for optimizing practices in radiology (Roch et al., 2018a, b). In fact, Hart et al. (2012) and Shrimpton and Edyvean (2014) conducted studies in the United Kingdom, a country pioneering and introducing the collection of doses delivered to patients in the 1980s and encouraging professionals to optimize their practices. Nearly 30 years later, the doses delivered to patients during examinations have been globally reduced by half in this country. Currently, several countries, including African countries, have recently established national DRLs to optimize and reduce radiation dose fluctuations during radiological examinations. (Joseph et al., 2018; Adejo, 2020; Abdulkadir et al., 2020). Previous studies in MOROCCO have established local DRLs for CT and interventional radiology (Ou-Saada et al., 2020; Benmessaoud et al., 2020). Nevertheless, few studies have been done in diagnostic radiology, including a study conducted by the International Atomic Energy Agency (IAEA) in 2004 entitled “Optimization of radiation protection of patients undergoing radiography, fluoroscopy and CT” conducted in Africa, Asia, and Eastern Europe, including Morocco, which aimed to evaluate the importance of quality control in radiology (IAEA, 2004). However, since 2004 technological advances in the practice of radiology in Morocco have expanded radiological procedures and changed exposure practices in facilities, including the progressive replacement of film-based radiology by the digital radiology system. Digital diagnostic radiology equipment offers enhanced image quality but can lead to higher radiation doses if no optimization tools are implemented (Schegerer et al., 2019).

Generally, several methods are used to estimate ESD in radiology; the indirect dosimetry method is used according to the IAEA Report Series No. 457 by direct measurement of Kerma in air using a solid detector or ionization chamber (Compagnone et al., 2005; Vassileva et al., 2005; Roch and Aubert, 2013), direct dosimetry using passive dosimeters such as thermoluminescent dosimeters (TLD) and optically stimulated luminescence (OSL) (Motlagh et al., 2020; Talbi et al., 2021). Finally, a retrospective method is used using dose estimation software such as CalDose and web-based ESD calculators such as (MICADO) from IRSN (Kramer et al., 2008; Roch et al., 2018a, b).

Locally, DRLs can be established to compare practices within a hospital, in a unit, or between hospitals in a selected region. Local DRLs should be close to or equal to national or regional DRLs that are established by the competent authorities taking into account individual national or regional circumstances such as availability of equipment and staff training. This study aims to establish local Diagnostic Reference Levels in computed radiography (CR), based on data measured and collected in health facilities in Morocco for the most frequent examinations (8 examinations) and to compare them with the values defined by several countries as well as with international standards.

2 Methods and materials

2.1 Data collection

This study was carried out in seven hospitals; 5 public radiography centers (2 university hospital centers, one local hospital, two provincial public health hospitals) and two private radiology offices with 11 radiology rooms equipped with CR radiology, 1747 adult patients of average size were taken into account in the survey (the criterion to identify an average height was the height, the average weight (70 ± 10 kg) and the thickness of the PA of the patient approximately 20 ± 5 cm). Data collection took place between April and November 2021, 8 of the most frequent radiographic examinations were included in this study, including the skull (posteroanterior [PA]), cervical spine (AP and LAT), spine lumbar (AP and LAT), thorax (PA), abdomen (AP), and pelvis (pelvis [AP]). Collection of exposure parameters such as kVp, mAs, focus-detector distance (FDD, cm), focus-to-skin distance, and patient anatomical data including weight, height, age, sex, and patient thickness were measured or calculated. Data collection was through forms produced following international recommendations and sent to radiology technicians and medical physicists by e-mail (Wachabauer et al., 2019). Data collection did not result in additional radiation exposure of patients and did not affect the facility’s workflow.

2.2 ESD calculation

The indirect dosimetry method was used according to the TRS 457 (IAEA TRS457, 2007). For each examination, a minimum of 20 adult patients was selected. The ESD (mGy) was calculated through the Air Kerma to assess the patient dose using a solid-state dosimeter (Accu-Dose + Dosimeter, RADCAL, USA, The dosimeter and the multimeter used have already a calibration certificate less than one year). Quantities measured included Kerma, dose rate, time, kVp, HVL, and beam filtration. The solid dosimeter was used to estimate the Entrance Surface Air Kerma (ESAK) (mGy) for the energy range (40–120 kV), the distance from the X-ray tube was 100 cm, and the field size was 10 × 10 cm2. The measurements were repeated three times for each exam chosen for greater precision (Motlagh et al., 2020). The tube voltage, current, and kerma in air (mGy) were recorded for each exposure under measurement conditions. ESAK is obtained from the following formula (Deevband, 2018): (1)

Air Kerma is the dose in air obtained by the dosimeter (mGy) under the measurement conditions. FDD and FSD refer to focus-to-dosimeter distance, focus-to-skin distance, respectively. BSF represents the backscattering factor. In this study, the BSF was between 1.3 and 1.5, obtained according to the recommendations of the IAEA (IAEA TRS457, 2007). The ESD was calculated by multiplying the ESAK by the mass energy absorption coefficients for tissue and air (this ratio is approximately 1.06 in digital radiology in 110 kVp, with ± 1% error According to (Deevband, 2018). The background noise was recorded to extract it from the measurement for each setting. (2)

2.3 Data analysis

The data collected were analyzed using the Statistical Package for Social Sciences version IBM SPSS 20. In each center, we used the average distribution of ESD observed for a specific examination on a representative sample, and we considered the median to compare found values in the different hospitals.

The third quartile (75th percentile) of the median entrance surface dose distribution (ESD) observed for each exam on a representative sample of patients in each center was considered to be their DRL following international recommendations (ICRP 135). A comparison of the DRL values obtained in this study with data from other countries was carried out (Zarghani et al., 2018; Alkhorayef et al., 2019). Personal patient data was not collected, and the dose data analysis was performed while respecting confidentiality.

3 Results

In this investigation, eight radiological procedures were analyzed, including the skull (AP), thorax (AP), cervical spine (AP and LAT), lumbar spine (AP and LAT), abdomen (AP), and pelvis (AP), which represent the most frequently performed examinations in the seven Moroccan Hospitals. The International Commission on Radiological Protection (ICRP) has advised establishing Diagnostic Reference Levels for routine radiological examinations (Vañó et al., 2017; Benmessaoud et al., 2020) therefore, non-routine procedures were excluded from the current study. Data from 1747 patients were collected, including patient anatomical information and exposure parameters, which were provided in Table 1, representing patient data including mean age, weight, and height, and the thickness of the patients examined in this study. The kVp and mAs exposure parameter data for all imaging centers are shown in Table 2. The recommendations of Publication 135 of ICRP (2017) are respected in this study, and the estimation of ESD for the different examinations (Vañó et al., 2017). Descriptive statistical values of ESD such as minimum (min), mean, maximum (max), median, third quartile (75° percentile), and standard deviation (SD) are shown in Table 3.

Graph 1 represents the median values for each procedure and each radiology center. For confidentiality reasons, hospital names are not shown.

Table 4 presents the value of the DRL (mGy) of this study and compares it to the levels of other countries and international organizations. In this table, the NRDs for all exams were reasonable and sometimes lower than those reported by official organizations such as the IRSN, and the National Radiology Protection Board (NRPB), except for the radiography of the thorax (PA and LAT).

Table 1

The mean and SD of age, weight, height, and thickness of patients.

Table 2

The mean, SD, min, and max of exposure values.

Table 3

The median, mean, min, max, and the 75° percentile distribution of ESD (mGy) of radiography examinations.

Table 4

Comparison of the DRL value of ESD (mGy) between this study and the international organizations and other countries.

4 Discussion

The Institute for Radiation Protection and Nuclear Safety (IRSN) has recommended that, in each facility, a periodic assessment of the doses delivered to patients for frequent radiological procedures are performed. The dose calculated by the type of examination for a significant number of patients must be compared with the value of the national and international reference levels. If the results show that the DRLs are regularly exceeded, a review of the procedures and an inspection of the facilities are necessary. Thereafter, corrective action should be considered if the excess is not justified.

No survey has been conducted on DRLs in Morocco previously. Therefore, this is the first study to establish DRLs for the most frequent radiological examinations in Morocco. Data from 1747 patients 57% female and 43% male were collected, the mean age for all radiological procedures was 48.37 years, the mean weight was 70.5 kg, the mean height of the patients was 165.12 cm, and the mean thickness of all patients undergoing radiographs was 23.1 cm, as listed in Table 1. The average exposure parameters for each examination are displayed in Table 2.

It can be seen in Table 3 that the lowest mean ESD value was 0.6 mGy for the chest X-ray (PA) and the highest was 9.5 mGy for the lumbar spine (LAT). The 75° percentile ESD values, for the 8 most frequent radiographic examinations included in this study are presented in Table 3. The comparison between the seven Moroccan hospitals was performed based on the median ESD values as the typical dose value for each facility as shown in Figure 1. The comparison showed variability in ESD between hospitals for most examinations; H7 recorded the highest median ESD (2.8 mGy) for the cranial examination (PA), followed by H1, which recorded a median value of 2.6 mGy, the least was H5 with a median score of 1.9 mGy.

Similarly, there was variability in ESD related to lung examination between hospitals. H7 recorded the highest median ESD (0.6 mGy), centers 3 and 5 recorded the same median value (0.51 mGy), whereas center 1 recorded a median ESD of 0.41 mGy. Likewise, there was variability in ESD related to the lumbar exam between centers for the projection (Lat); H6 recorded the highest median ESD (7.7 mGy) and H4 recorded the median value of 6.5 mGy. For the abdominal (AP) examination, the highest value was recorded at center 4 with a median ESD value of 7.1 mGy, and centers 1 and 7 recorded the lowest median ESD values (6.4 mGy). Also, center 7 recorded the highest median ESD value for pelvic examination (AP) with 6.3 mGy, while the center that recorded the lowest value was center 1 with a value of 5.3 mGy. Centers 6 and 7 recorded the highest median ESD 2.3 mGy each for the cervical examination (Lat), followed by center 6 which recorded a median value of 2.1 mGy, the least was center 1 with a median score of 1.3 mGy.

Comparing the Moroccan hospitals listed in Figure 1, in terms of all examinations, the median values recorded at H1 for all radiological examinations were lower than those of all other hospitals. While the median values recorded at H7 followed by H6 were higher. The higher values observed in H7 are justified by the techniques used; very short patient source distance with an average of 82 cm compared to 88 cm for the other hospitals. Whilst, the high values observed with an apparent increase in H6 are also due to the fact that the examinations are performed by exposure parameters (kV, mAs) too high.

Several studies in medical imaging have shown the importance of DRLs as a tool for optimizing radiology practices (Beauvais-March et al., 2003; Roch et al., 2018a, 2018b). To evaluate the DRLs, the 75° percentile values from this study were compared with previous studies on Diagnostic Reference Levels for other countries and international organizations. Table 4 shows the comparison of Diagnostic Reference Levels established for radiographic examinations with IRSN (France), NRPB (UK), Japan, Sudan, and Iran. The evaluation for the skull radiograph in PA showed that the 75th percentile was higher than that of Sudan and Iran, and almost comparable to that of NRPB and Japan. Regarding the DRLs results of chest radiography in PA were slightly higher than those of IRSN, NRPB, and JAPAN studies, and almost similar to Sudan studies and largely lower than Iran. The DRLs for AP abdominal radiography in our study was lower than that of IRSN and higher than that of the other studies (NRPB, Japan, Sudan, and Iran). The DRLs for pelvic radiography in AP were lower than those of IRSN and higher than those of the other studies (NRPB, Japan, and Iran). According to Table 4, generally, the DRL values of this study were comparable to the studies and DRLs of the international organizations, however, variations between the DRLs of the current study with the international organizations (IRSN and NRPB) and the other countries reported, the DRL values for the same type of procedure may be different due to the differences in the thickness of the patients, as well as the difference between the radiographic equipment used and the techniques employed (Vodovatov et al., 2017; Motlagh et al., 2020).

It can be explained also by the lack of training programs in optimizing medical exposure and in quality control techniques at the national level, mainly in new digital radiography techniques that can lead to increased patient doses.

The implementation of clinical training for medical physicists in radiology and of a relevant regulation will help to overcome these difficulties

This study had a limited sample size; the established DRLs were implemented at only seven Moroccan hospitals and included data from only eight radiological examinations. Future studies could consider including pediatric patients as an additional group and increase the number of hospitals involved. Also in CT and interventional radiology.

thumbnail Fig. 1

Comparison of mean ESD (mGy) values between the seven Moroccan hospitals.

5 Conclusion

The introduction of DRLs is an important step in the control and optimization of patient radiation protection. The regulatory body “AMSSNuR” and the concerned departments are working to establish DRLs in terms of examination indications so that health professionals can appropriate this tool and use it to optimize their practice. Training and information programs, with the involvement of the learned society, are therefore necessary to encourage professionals to use DRLs to evaluate and optimize their practices.

Conflict of interest

All authors declare that they have no conflicts of interest.

Funding

The authors received no financial support for the research.

Ethical approval

Not applicable.

Informed consent

Not applicable.

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.

References

Cite this article as: Talbi M, Tahiri Z, Eddaoui K, El Mansouri M, Nhila O, Benmessaoud M, Ait Ouaggou I, Chakir E, Sebihi R, Khalis M. 2022. Local Diagnostic Reference Levels (LDRLs) for routine X-ray examinations in Morocco. Radioprotection, https://doi.org/10.1051/radiopro/2022008.

All Tables

Table 1

The mean and SD of age, weight, height, and thickness of patients.

Table 2

The mean, SD, min, and max of exposure values.

Table 3

The median, mean, min, max, and the 75° percentile distribution of ESD (mGy) of radiography examinations.

Table 4

Comparison of the DRL value of ESD (mGy) between this study and the international organizations and other countries.

All Figures

thumbnail Fig. 1

Comparison of mean ESD (mGy) values between the seven Moroccan hospitals.

In the text

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