RESUMEN
The purpose of this study was to find the accurate absorbed dose in the femur bone marrow during the X-ray radiography for constant mAs and AEC techniques. The DOSXYZnrc was used to simulate radiation doses in two human femurs during diagnostic radiography. EGSnrc phantoms produced from actual CT images of human femurs were modified by adding seven micrometre layers of marrow tissues. The X-ray machine was simulated using BEAMnrc using 30 billions particles for different combinations of energies and filters. The resultant data was used to in DOSXYSnrc simulations to evaluate the absorbed dose in the human femur. In the head of the femur, for 2.5 mm aluminium filtered 85 kVp X-ray set at 50 mAs, the absorbed dose in the marrow was found to be 1.360 mGy, tilde 36% of the absorbed dose in the cortical bone. It was also found that for the constant mAs technique, the radiation dose in the marrow over the studied energies and filter combination, ranges from 0.356 mGy to 2.403 mGy, with higher dose recorded for higher kVp settings. However, for the AEC technique, the dose is lower for higher kVp settings. For a typical setting, viz. 85 kVp, 6 mAs at 48 inches SID, the bone marrow absorbed dose was found to be 0.186 mGy for the constant mAs technique and 0.0308 mGy for the AEC technique. It was confirmed that the radiation dose is lower when the AEC exposure technique is used as opposed to using constant mAs technique. For the AEC technique, typical dose to the bone marrow was found to be tilde 0.05 mGy, decreasing with both kVp settings and beam filtration. For constant mAs technique, the typical dose to bone marrow is found to be higher, tilde 0.2 mGy, decreasing with the amount of filtration used but increasing with the kVp setting
RESUMEN
This study has been carried out to determine the accumulation of heavy metals [arsenic, copper, lead, tin and zinc] in fish samples collected from former tin mining catchment. Total eight types of fish family having fifteen different species are identified. Cyperinidae is the most abundant family with eight different species found in the catchment. Fish samples were analysed by using inductively coupled plasma optical emission spectrophotometer ICP-OES. The accuracy of method is validated by certified reference material. The highest level of arsenic was observed in Hampala macrolepidota while Osteochilus hasselti shows the least. For Copper concentrations, the maximum was obtained in Mastacembelus armatus and the minimum in Oxyeleotris marmorata. High levels of lead, tin and zinc were found in the Rasbora elegans, Trichogaster trichopterus, Oxyeleotris marmorata respectively while Macrobrachium resenbergii, Mastacembelus armatus, Rasbora elegans had the least concentrations. The sequence of order of the heavy metals measured was Sn > Pb >Zn > Cu> As, respectively. The results showed elevated levels of tin, lead and zinc in all the fish samples although copper and arsenic were available in relatively low concentration in the most samples. Sn, Pb, and Zn concentration in the samples were greater than Malaysia food act permissible levels. Hazard index < 1 suggests unlikely adverse health effects whereas HI > 1 suggests the probability of adverse health effects. Although the heavy metals analysed in the catchment did not pose any immediate health risk to humans but due to the bioaccumulation and magnification of these heavy metals in humans, it is essential to safeguard levels of the metals in the environment