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.

Dosimetry quality control based on percent depth dose rate variation for checking beam quality in radiotherapy.

Recently, the quality management inside a radiotherapy department has been crucial to treat cancer efficiently. Thus, many international bodies recommend multiple methods to check in periodically the dosimetry quality beyond the depth of 10 cm as the beam quality index. However, they evade checking out the beam dosimetry quality on both the build-up dose and the electronic equilibrium regions. The objective of this study is to cover the overall variation of the percent depth dose (PDD) by including all sub-regions in the procedure evaluation of the beam quality. In this work, we have studied and examined the dosimetry quality by considering the whole PDD variation. The PDD rate is therefore introduced to determine accurately the quality as an overall notion in external beam radiotherapy according to the field size and photon beam energy. We have presented the reasons and methods to introduce particles contamination, such as electrons and low photon energy in this new approach. The latter enables us to figure the dosimetry quality by extending the International Atomic Energy Agency (IAEA) procedure at any field size less than 25 × 25 cm2 under the current conditions without being limited to 10 × 10 cm2 on the exponential decay region.