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Background:

An effective method for management of large and bulky malignant tumors. This treatment modality is also known as Specially Fractionated Radiation Therapy (SFRT). In this treatment technique a grid block converted the open radiation field into a series of pencil beams. Dosimetric characteristics of an external beam grid radiation field have been investigated using experimental and Monte Carlo simulation technique.

Grid radiation therapy, using the megavoltage X-ray beam, has been proven to be

Materials and Methods:

radiation field have been determined using experimental and Monte Carlo simulation technique, for 6- and 18 MV X-ray beams from a Varian Clinics 2100C/D. The measurements were performed using LiF TLD and film in Solid Water phantom Material. Moreover, the MCNP Monte Carlo code was utilized to calculate the dose distribution in the grid radiation field in the same phantom material. The results of the experimental data were compared to the theoretical values, to validate this technique. Upon the agreement between the two techniques, dose distributions can be calculated for the grid field with different patterns and sizes of holes, in order to find an optimal design of the grid block.

Dose distributions (%DD as well as the beam profiles) of a grid

Results:

simulation technique was in good agreement with the measured data. In addition, the 3D dose distribution of the grid field generated by the Monte Carlo simulation gave more detailed information about the dose pattern of the grid.

The results of dose profiles for 6 MV X-ray beams obtained with the Monte Carlo

Conclusion:

Carlo simulation technique can be utilized to optimize the pattern, size and spacing between the holes, for optimal clinical results.

The grid block can be used as a boost for treatment of bulky tumors. The MonteIran. J. Radiat. Res., 2005 2 (4): 167-174

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Background: Health hazards associated with exposure due to the natural radioactivity which is a part of our physical environment are of great concern. In order to assess the risks associated with exposure due to the natural radioactivity in soil and building materials, extensive studies have been carried out all over the world. The most commonly encountered radionuclide’s are ²³⁸U, ²³²Th, their decay products and ⁴⁰K. Materials and Methods: In order to study the concentration of these radionuclides soil, sand, gravel aggregates, bricks and marble, samples were collected from different sites and local suppliers of the district Mirpur, Azad Kashmir (Pakistan). ²²⁶Ra, ²³²Th, and ⁴⁰K activities in the collected samples were measured using HPGe detector. The measured specific radioactivity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied samples ranged from 10 ±1 to 47 ± 2, 18 ± 1 to 75 ± 4 and 40 ± 3 to 683 ±3 Bq.kg-1, respectively. Results: From the measured activity concentration, radium equivalent activity, external and internal hazard indices, gamma and alpha indices, terrestrial absorbed dose and annual effective dose were calculated. Maximum value of radium equivalent activity of 197.1 ± 9 Bq.kg-1 was observed in soil sample whereas minimum value of 45.9 ± 2 Bq.kg-1 was found in gravel aggregates. Relatively higher mean values of hazard indices were found in brick samples. Annual effective dose varied from 0.06 ± 0.01 to 0.47 ± 0.02 mSv.y-1. Conclusion: Current values of annual effective dose, radium equivalent activity and hazard indices have been found to be within the recommended limits. Iran. J. Radiat. Res., 2011 9(2): 77-87

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Background: Natural radionuclides are always present in the environment. Human exposure to the background radiation is inevitable. It is therefore important to assess health risk associated with these radionuclides. Materials and Methods: The distribution of natural radionuclides ²³⁸U, ²³²Th and ⁴⁰K in soil samples collected from all the twenty (20) local Governments headquarter areas in Ogun state, Nigeria were determined by gamma spectroscopy using a high-purity germanium detector. The measured concentrations were used in estimating the radiological risk pose to people living in these communities. Results: The activity concentrations measured ranged between 3 ± 1 Bqkg^-1(Otta) to 27 ± 6 Bqkg^-1(odeda) for ²³⁸U, 10 ± 1 Bqkg^-1(Otta) to 126 ± 6 Bqkg^-1(Ijebu Igbo) for ²³²Th and 7 ± 6 Bqkg^-1(Aiyetoro) to 497 ± 1 Bqkg^-1(Odeda) for ⁴⁰K. The mean radium equivalent calculated was 77.6 Bqkg^-1 which is lower than 370 Bqkg^-1 of the world average and the hazard indices calculated were lower than unity. Conclusion: The absorbed rate and annual effective dose estimated for most of the locations are in good agreement with world average values except for Akomoje, Ake-Abeokuta, Ogere, Ijebu-Igbo and Odeda.