• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.6
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• pp.3734-3740
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• 2014

The aim of this study was provide basic information and establish the criteria in radiation therapy planning by measuring the absorbed neutron dose of normal tissues and lesions according to the number of portals. From September 2013 to January 2014, 20 patients who were diagnosed with prostate cancer and were previously treated with radiation therapy were replanned retrospectively to measure the absorbed neutron dose distribution according to the number of portals. The absorbed neutron dose was measured in each of the 5, 7 and 9 portals using a 15 MV energy, which meant a therapeutic dose of 220 cGy. The optical stimulation luminescence dosimeter was separated by 20cm and 60cm away from the center of the field of view. As a result, the average radiation dose in the abdomen appeared to have a positive relationship with the number of portals, which was statistically significant (p<.05). The average radiation dose was $4.34{\pm}1.08$. The average radiation dose in the thyroid was $2.71{\pm}.37$. Although it showed a positive relationship with the number of portals, it did not have statistical significance. The number of portals and the neutron dose depending on the position showed a significant positive relationship, particularly in the abdomen. As a result of linear regression analysis, as the number of the portal increased in steps, the average volume of the neutrons increased significantly (0.416 times). In conclusion, efficient selection of the number of portals is needed considering the difference in the absorbed neutron dose in the normal tissues depending on the number of the portals.

• Journal of radiological science and technology
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• v.35 no.4
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• pp.335-343
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• 2012

Intensity-modulated radiotherapy(IMRT) have the ability to provide better dose conformity and sparing of critical normal tissues than three-dimensional radiotherapy(3DCRT). Especially, with the benefit of health insurance in 2011, its use now increasingly in many modern radiotherapy departments. Also the use of linear accelerator with high-energy photon beams over 10 MV is increasing. As is well known, these linacs have the capacity to produce photonueutrons due to photonuclear reactions in materials with a large atomic number such as the target, flattening filters, collimators, and multi-leaf collimators(MLC). MLC-based IMRT treatments increase the monitor units and the probability of production of photoneutrons from photon-induced nuclear reactions. The purpose of this study is to quantitatively evaluate the dose of photoneutrons produced from 3DCRT and IMRT technique for Rando phantom in cervical cancer. We performed the treatment plans with 3DCRT and IMRT technique using Rando phantom for treatment of cervical cancer. An Rando phantom placed on the couch in the supine position was irradiated using 15 MV photon beams. Optically stimulated luminescence dosimeters(OSLD) were attached to 4 different locations (abdomen, chest, head and neck, eyes) and from center of field size and measured 5 times each of locations. Measured neutron dose from IMRT technique increased by 9.0, 8.6, 8.8, and 14 times than 3DCRT technique for abdomen, chest, head and neck, and eyes, respectively. When using IMRT with 15 MV photonbeams, the photoneutrons contributed a significant portion on out-of-field. It is difficult to prevent high energy photon beams to produce the phtoneutrons due to physical properties, if necessary, It is difficult to prevent high energy photon beams to produce the phtoneutrons due to physical properties, if necessary, it is need to provide the additional safe shielding on a linear accelerator and should therefore reduce the out-of-field dose.