Comparison of the conventional positioning method and the hip-fix system for pelvic irradiation

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Comparison of the conventional positioning method and the hip-fix system for pelvic irradiation


Author: Chan, Wing-ip
Title: Comparison of the conventional positioning method and the hip-fix system for pelvic irradiation
Degree: M.Sc.
Year: 2000
Subject: Pelvis -- Diseases -- Radiotherapy
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Optometry and Radiography
Pages: ix, 79 leaves : ill. (some col.) ; 30 cm
Language: English
InnoPac Record:
Abstract: The development of a suitable and effective immobilization device for conformal treatment of the pelvic region has been a challenge in radiotherapy. This study is to investigate the treatment accuracy of the conventional set-up and the Hip-fix system for radiotherapy of the pelvic malignancies. Forty patients with carcinoma of rectum were randomised into two different set-up groups. For each patient, portal films of postero-anterior and lateral views were taken weekly during the course of treatment. By comparing the portal films with the simulation film, set-up accuracy was found. It was interpreted as the isocenter deviations for treatment fields, while for individual patient, the systematic error, random error and also total uncertainty were measured and calculated. In addition to isocenter deviation, factors that might affect the treatment accuracy like the change of patients' separation and body weight during the course of treatment were also studied. Concerning the reduced skin sparing effect of the Hip-fix system, radiation reactions of skin were recorded and analyzed for both groups of patients. The data collected from the two groups were then compared. It was found that the mean isocenter deviation of the Hip-fix group for both the posteroanterior and lateral views were significantly less than the group treated with conventional set-up method. Similar results were also found in comparing the errors of the two groups. The mean values of the systematic errors, random errors and total uncertainty calculated for both views of the Hip-fix group were also smaller than that of the group treated with conventional set-up method. Analysis of the isocenter deviations and the values of the change of parameters like the body separation and weight during the course of treatment found that there were no correlation between the treatment accuracy and the change of parameters. The observation of skin radiation reactions in the two groups showed that there was no difference between the two groups with regards to the severity and the on-set of the reactions. In conclusion, the Hip-fix system for the isocentric treatment of pelvic malignancies is better than the conventional set-up method in terms of treatment accuracy. The reduced skins sparing of the material used in the Hip-fix system does not worsen the skin radiation reaction when compared with the conventional set-up method. Hip-fix system is recommended for future development of treating pelvic diseases with conformal radiotherapy.

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