Establishment of standard x-ray qualities to be used in diagnostic level at SSDLs

The objective of the present work is to modify x-ray machine (used by the secondary standard dosimetry laboratory in Sudan) to produce x-ray qualities suitable for the calibration at diagnostic level. It based on experimental evaluations. The importance of this study appears in development of protocols to calibrate the instruments used in diagnostic radiology in by good response of the instruments and low cost. In particular, the half value layer (HVL) values for the following qualities 40, 60, 80, 100, 120 and 150 were determined using various attenuation layers. Ionization chamber was used to determine the free air kerma rate at a distance of 100 cm from the x-ray generator. The obtained HVL values were compared with standard values of diagnostic levels. It was observed that the HVL of the present x-ray machine in most qualities are smaller than the standard ones. An approved method (described in the standard IEC 61267) was applied to determine the amount of additional filtration required to meet the standard values. The results show that the available cupper layers were not suitable for this purpose as most of the x-ray was absorbed in the material. Aluminum layers, on the other hand , show good performances to reduce the beams to the desired levels. The amount of additional filtration (from aluminum layers) needed in order to establish standard x-ray qualities to be used in diagnostic level were determined.(Author)