| LI Li-jun,SONG Hong-yu,PAN Jie-sen.Calculation of an equivalent square field for irregular photon beam fields[J].Chinese Journal of Radiological Medicine and Protection,2005,25(4):366-367 |
| Calculation of an equivalent square field for irregular photon beam fields |
| Received:December 02, 2004 |
| DOI： |
| KeyWords:Irregular field An equivalent square field Radiotherapy |
| FundProject: |
| Author Name | Affiliation | | LI Li-jun | Center of Radiation Oncology, Baoan Hospital, Shenzhen 518101, China | | SONG Hong-yu | Center of Radiation Oncology, Baoan Hospital, Shenzhen 518101, China | | PAN Jie-sen | Center of Radiation Oncology, Baoan Hospital, Shenzhen 518101, China | | 程媛 | Center of Radiation Oncology, Baoan Hospital, Shenzhen 518101, China |
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| Abstract:: |
| Objective To explore a rapid method of calculating an equivalent square field for irregular photon beam fields. Methods Irregular photon fields can be divided into two types: the fields symmetric to the beam central axis and the fields dissymmetric to the beam central axis. Each type contains three conditions (i.e. R>1, R=1, R<1) according to the perimeter ratios of the irregular fields to the original fields. To choose 6 irregular fields and measure the absorption doses. Then work out the equivalent square field of each of the 6 irregular fields by means of A, B and C. Finally compare the prescription doses and those measured. Results In the condition R>1, method B worked precisely. In the condition R=1, method A and method C worked rather precisely, while method B meet the accuracy demand. In the condition R>1, method A, B and C worked precisely and consistently. Conclusion Method B can be recommended for clinical use, for it is convenient for standardized operations and meets the accuracy demand. |
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