Introduction: GATE is practically the only nuclear medicine dedicated code with the option to determine the dose distribution inside the body. This code has been designed as upper layer of the GEANT4 toolkit and has been used for internal dosimetery. However, its results have not been compared to other well-developed codes. Moreover anthropomorphic voxel phantoms have never been used with GATE for internal dosimetry. The aim of present study was to compare the dose calculated with GATE to MCNP4B published data.Methods: The Zubal voxel phantom was used to model a typical adult male. Activity was assumed uniformly distributed in liver, kidneys, lungs, spleen, pancreas and adrenals. GATE Monte Carlo package was used for estimation of doses to the organs of phantom. Simulations were performed for photon energy of 0.01-1 MeV and mono-energetic electrons of 935 keV. Specific absorbed fractions for photons and s-values for electrons were calculated.Results: On average, GATE produces higher SAF values (+2.7%) for self-absorption and lower values (-2.9%) for cross-absorption. The SAF values calculated with MCNP4B for lungs as source organ at the energy of 200 and 500 keV was considerably higher than GATE data.Conclusion: Despite of differences between the GATE4 and MCNP4B, the results can be considered ensuring. This difference was almost at the same level as the reported difference between MCNPX and MCNP4b. As a result, this may be considered as validation of GATE as a proprietary code in nuclear medicine for radionuclide dosimetry applications.

Introduction: Internal dose assessment is usually performed using pre-calculated reference data derived from humanoid anatomical models. Medical Internal Radiation Dose (MIRD) has been the main source of reference data for dose assessment in nuclear medicine for diagnostic and protection objectives. These reference data are calculated assuming uniform distribution of radioisotopes in the organs of some limited number of humanoid models. Practically, however, human anatomy is too much variable that can be represented using a limited number of models. But they are valid in simple conditions they have been derived. GATE is a dedicated code to nuclear medicine and has almost been validated for internal dosimetry application; however, GATE results have never been compared to MIRD reference data. In this study, we constructed the digital form of Snyder phantom and used it with GATE to calculate the doses to the organs from photons of different energies.Methods: The mathematical Snyder phantom sampled digitally and converted to a voxel phantom. Activity was distributed uniformly within the kidneys, liver, lungs, pancreas, spleen and adrenals. The GATE Monte Carlo package was used for calculation of doses in the organs of phantoms. Simulations were performed for gamma photons of 10-1000ke V. Data derived with GATE was then compared to MIRD published data.Results: The results imply a negligible bias between MIRD and GATE data for self-irradiated organs. Bland-Altman analysis shows that the SAF values derived with GATE are on average 0.16% smaller than MIRD values for self-irradiated organs. Data derived for cross-irradiation shows a good linear relationship between SAF values derived with GATE and corresponding MIRD data. The average relative differences between MIRD and GATE data for self-irradiated organs are below 3%. For cross-irradiated organs, the relative difference was 6-10% for photon energy >30 and quite considerable (>25%) for photon energies of 10, 15, 20, and 30keV.Conclusion: Comparison of our data with corresponding MIRD data for cross-irradiated organs showed a high dependency to absolute value of SAF. Correlation between our data and MIRD was high when SAF value was high and decreased as SAF value decreased. As a result the consistency between SAF values derived with GATE and corresponding MIRD data is high when absolute value of MIRD data are greater than 0.01.

Background: Indoor radon gas (222Rn) has been recognized as one of the health hazards for human. Air radon comes mainly from basement soil and construction materials. Saghand region with rich uranium mines lies 180 km from Yazd, so the indoor radon concentration can be high. Yazd, with population of about 457000, is the biggest city near Saghand, thus, indoor gamma background radiation of Yazd could be more than the other cities of Yazd province. Materials and Methods: In this study the air radon level of 84 dwellings basement from various regions of Yazd were measured during the year 2007. To do so, a portable radon gas surveyor was used which is an active measurement method. Using this device, α radiation of each basement was measured by a solid state detector for 24 hours. Results: Radon concentrations of the basements were between 5.55 to 747.4 Bq/m3 with mean of 137.36 Bq/m3. The mean radon concentration wasn't significantly different from the EPA guide line that is mitigation recommendations level (148 Bq/m3). However, more than 30% of the basements had radon concentration more than EPA guide line. Conclusion: Using good air conditioning system in the dwelling basements is suggested.

Introduction: The accurate delivery of dose to the clinical target volume in radiotherapy can be affected with many different factors. With increased interest in 3-D conformal therapy and also in the context of multicenter clinical trials, it is necessary to provide standard techniques to assure quality in delivering treatment. An anthropomorphic phantom can be employed to verify the quality and consistency of treatments by mimicking the many steps involved in a radiotherapy process.Material and Methods: An anthropomorphic pelvic and cervix phantom was designed and fabricated to be used for imaging, treatment planning, and dosimetry application in the treatment of cervical cancer. The phantom was made of mm acrylic plates and each plate was machined and modeled based upon CT slices from a patient study. Most of the phantom was made of acrylic while contours of femur and the vertebral column were filled with appropriate materials. The CT numbers from patient images were used to adjust the composition of bone equivalent material. During the simulations, a Foley catheter and a rectal tube filled with a proper contrast agent were used to distinguish bladder and rectum from the remainder of the phantom. A23323 PTW intra- cavitary chamber which was cross calibrated against a NE 2581 ionization chamber was placed in special holes machined in phantom for dosimetry applications. The dose delivered to the isocenter (cervix), bladder and rectum were calculated using a 2D Plato treatment planning system and were compared with measured values.Results: The phantom is to be used to evaluate the consistency of a range of processes in radiation therapy, simulation, planning and delivery of treatment for cervical cancer.Conclusions: The objective of this study is to use the phantom to verify the accuracy and consistency of treatments in one institution and in national collaborative clinical trials, during acceptance testing of treatment planning systems and as an educational tool, for dosimetric research problems and for QA in radiation treatment of cervical carcinoma.