ESTABLISHMENT OF LOCAL DIAGNOSTIC REFERENCE LEVELS FOR PAEDIATRIC ABDOMINAL-PELVIS AND CHEST-ABDOMINAL-PELVIS COMPUTED TOMOGRAPHY IN MOROCCO: SUGGESTS THE NEED FOR IMPROVED OPTIMIZATION EFFORTS.

The purpose of the current study was to derive the local diagnostic reference levels (LDRLs) for paediatric abdominal-pelvis (AP) and chest-abdominal-pelvis (CAP) computed tomography in Morocco. The data were gathered retrospectively from two hospitals for 6 months. The LDRLs were defined by volume CT dose index (CTDIvol), dose-length product (DLP) per sequence, DLP per procedure and size-specific dose estimates (SSDE). The SSDE assessment was based on the effective diameters of patients scanned. A total of 630 CT examinations were collected involving 324 AP and 306 CAP scans. The proposed LDRLs for AP, in terms of CTDIvol (mGy), were 6.9, 8.5, 8.5 and 8.5 for < 1, 1 to < 5, 5 to < 10 and 10 to < 15 y age groups, respectively. In terms of DLP (mGy.cm) per procedure, they were 436.3, 534.5, 687.9 and 961.7. In terms of SSDE (mGy), thet were 16.73, 16.83, 17.5 and 15.8 for < 1, 1 to < 5, 5 to < 10 and 10 to < 15 y, respectively. The corresponding LDRLs for CAP, in terms of CTDIvol (mGy), were 7.3, 7.3, 7.3 and 10.35. In terms of DLP (mGy.cm) per procedure, they were 531, 622.5, 705 and 936. In terms of SSDE (mGy), they were 16.22, 15.05, 14.47 and 15.2, respectively, for the four age groups. The derived dose levels were mostly higher than those found in other studies, which demonstrates the need for dose optimization and paediatric protocol standardization as well as the timeliness of the intent to establish not only local DRLs but national ones in the near future.

Design of a protective shield for a radiological emergency intervention using Monte Carlo simulation and an anthropomorphic phantom.

Due to the increasing use of radioactive sources, new challenges appear for the protection of humans and the environment against ionizing radiation. Thus, organizations handling these sources must be endowed with plans how to react in case of any radiological emergency situations. Monte Carlo simulations are among the most widely employed methods used for the management and reconstruction of radiological incidents and accidents. In this work, results of a Monte Carlo simulation study with the Geant4 simulation toolkit using a digital anthropomorphic phantom are reported. The investigated scenario included an emergency intervention carried out inside the ionization cell of the National Institute of Agronomic Research (NIAR) of Tangier/Morocco, which houses a 60Co gamma irradiator. In this scenario, a radiological incident was assumed where the source cage of the gamma irradiator is stuck in the guide tube and not completely inserted into its storage container. The objective of this work was to design a radiation shield to protect an operator during the emergency intervention and make sure that any radiation exposure is below the recommended dose limits, taking into account the date of occurrence (which determines the activity of the source at the time of the emergency situation) of the accident and economic aspects of shielding design. In this work, the maximum time available for the operator to accomplish the operation intervention while remaining protected is calculated. The results obtained show that the shielding prototype developed gives the operator a time between 3 and 300 s, depending on shielding design. It is concluded that shielding of the type investigated in the present study will allow any facility to manage the assumed emergency scenario, should it occur.