ABSTRACT
Background: The aim of the study was to analyze the effective dose record of occupationally exposed radiation workers at Bahawalpur Institute of Nuclear Medicine and Oncology department. Materials and Methods: Annual effective doses of occupationally exposed workers were measured by film badge dosimetry by sending the dosimeters to Radiation Dosimetry Laboratory [RDL], Pakistan Institute of Nuclear Science and Technology [PINSTECH], Islamabad, Pakistan. 46 Radiation workers dose records were studied for a period of 14-years [2000-13]. Professionally exposed radiation workers were divided into groups depending upon their professions. Results: Average effective doses of oncologists, nuclear physicians, medical physicists, radiation technologists, nurses and other supporting staff were in the range of 0.64-1.86, 0.61-2.27, 0.63-1.74, 0.67-2.53, 0.65-2.31 and 0.68-1.79 mSv respectively. The highest annual dose received by radiation technologist was 4.95 mSv. Nobody received the radiation dose greater than 5 mSv in any year and no overexposure case has been noticed throughout the study period. Conclusion: The results revealed that occupationally exposed individuals received doses lower than the recommended annual limits of 20 mSv y[-1]. This study provides basis to set up action level that is obligatory by Pakistan Nuclear Regulatory Authority, Pakistan
ABSTRACT
It was intended to investigate the effect of physical wedge [PW] and enhanced dynamic wedges [EDW] on contralateral breast dose during primary breast irradiation in radiotherapy treatment, using high energy photon beams. The Varian's Clinac dual mode linear accelerator model 2100 C/D and Siemen's Primus accelerators were used for radiation doses with 6 MV and 15 MV. Doses were delivered using Tangential field techniques and asymmetric collimator jaws. Eclipse three-dimensional Treatment Planning System [3DTPS] was used to measure contralateral breast dose for all fiend settings. Sixty five patients [with cancerous breast as well as chest wall] were taken and their contralateral breast doses were measured at a point 5 cm across, at 2 cm depth from the end of the medial field. The contralateral breast dose mean difference was 0.25 cGy and 0.24 cGy during the comparison of PW and EDW on Varian's Clinac and 0.19 cGy and 0.18 cGy were found for medial EDW and without medial EDW for the same machine in breast cases and chest wall cases respectively as per total prescribed dose. The mean difference for PW [Clinac] and PW [Primus] was found 0.08 cGy and 0.31 cGy and during the comparison of medial PW and without medial PW on primus machine this mean difference was 0.25 cGy and 0.51 cGy in breast cases and chest wall cases respectively as per total prescribed dose. The investigation demonstrates the significance that the EDW produces less scattered dose, which can cause second breast malignancy, compared to PW. Furthermore, the medial wedge, too, can cause second breast malignancy and should be avoided in planning
ABSTRACT
Radiotherapy Treatment Planning requires different dosimetric quantities as input in order to calculate a desired dose distribution. This study has been focused to evaluate the depth dose characteristics of superficial X-rays being used for radiotherapy treatment. Computerized 3-D water phantom of multi-data system was used. The measurements were made through PTW [Physikalirsch-Technische Werkstalten] farmer type NT-30006 waterproof ionization chamber of 0.6cc, and PTW electrometer for digital dose rate reading in Gy/min using five different diameter applicators and filters at five different values of accelerating potentials [kVps]. The dose rate at various kVp X-ray beams was observed to decrease significantly with increasing depth in water phantom for all applicator diameters from 98% [at 0.1cm depth] down to 43% [at 2cm i.e. reference condition]. The dose rate increases by increasing the value of kVp with a maximum at 150 kVp [1.6 and 0.93 Gy/min for respective applicator diameters 2.5cm and 10cm]. Applicator with 2.5cm diameter demonstrates better dose rate at 85kVp at different depths. PDD decreases lower than 50% for all combination of applicators and kVps at/or above 2cm depth so these measurements should not be considered for treatment planning. Higher energy X-rays are suggested to be used for applicators of higher diameters and smaller energy X-rays for applicators having smaller diameters