A survey of the entrance surface doses in the routine radiography of children in eastern Nigeria has been carried out in three hospitals, using thermoluminescence detectors. Chest, abdomen, lumbar spine, skull and pelvis were covered in this study. Findings reveal that doses are higher than the recommended reference values elsewhere, as well as values reported for Sudan. The mean percentage difference in entrance doses for chest radiography for this study and an earlier one carried out for three hospitals in the west of Nigeria is about 44.7%. The high doses are traceable to a lack of standardization in procedure, resulting in use of low tube voltages and high currents for examination, as well as the status of facilities in the area. Recommendations are made for immediate corrective measures to lower the doses.

No abstract

The UNSCEAR (2000) observed that there could be some exposure at work which would require regulatory control but is not really considered. This study was, therefore, set up to evaluate the effective dose in timber industries in Calabar, Nigeria to determine if the evaluated dose levels could lead to any radiological health effect in the workers, and also determine if the industries require regulatory control. The gamma ray exposure at four timber industries measured using an exposure meter were converted to effective dose and compared with the public and occupational values. The evaluated effective dose values in the timber industries were below public and occupational exposure limits and may not necessarily result in any radiological health hazard. Therefore, they may not require regulatory control.

Electron applicators and cut-outs have been used for some time in the delivery of electron beam therapy. A dual electron multileaf collimator (eMLC) consisting of upper and lower eMLCs was designed, and dose distributions of electron beams delivered by it were evaluated by Monte Carlo simulations by use of the EGSnrc Monte Carlo code. The percentage depth dose (PDD), dose profiles, dose gradient falloff (G), depth of maximum dose (R(100)), surface dose, bremsstrahlung background, beam flatness, and penumbra of the dual eMLC were evaluated and compared with those simulated and measured with the standard applicators inserted into the treatment head of the medical linear accelerator (linac). The results showed good agreement in most cases. Specifically, the flatness and penumbra obtained with the dual eMLC were better than those obtained with standard applicators. It is therefore possible to use the proposed dual eMLC in the delivery of electron beam therapy without the need for applicators and cut-outs. This will minimize the inconvenience of placing cut-outs on the patients; also, changes in the required field can be effected without the therapist going into the accelerator room when the dual eMLC is finally automated. The absence of a helium bag between the upper and lower eMLCs did not offer significant changes in the dosimetry parameters compared to the eMLC fitted with the helium bag.