ABSTRACT
OBJECTIVE: The aim of this study is to evaluate the efficacy of electronic portal imaging (EPI) to measure the set-up errors for four different sites of irradiation caused by patient positioning. METHODS: A total number of 95 portal images of 11 patients (3 pelvic, 1 total cranium, 3 mantle and 4 tangential fields for breast) were collected during the course of study. The first portal images after a correction of set-up errors according to the simulation films were accepted as the reference images for the subsequent sessions. By matching each portal image with the reference image, the deviations in lateral (x) and superior-inferior (y) axis for all and additionally in antero-posterior (z) axis for pelvis, and standard deviations were calculated. RESULTS: The set-up errors caused by patient's positioning are completely abolished in 15 mm planning target volume (PTV) margins for all studied cases. CONCLUSION: Standard PTV margins usually completely cover the set-up errors caused by patient's positioning.
Subject(s)
Neoplasms/radiotherapy , Radiotherapy Planning, Computer-Assisted/methods , Adenocarcinoma/pathology , Adenocarcinoma/radiotherapy , Adenocarcinoma/surgery , Brain Neoplasms/pathology , Brain Neoplasms/radiotherapy , Breast Neoplasms/pathology , Breast Neoplasms/radiotherapy , Breast Neoplasms/surgery , Carcinoma, Ductal, Breast/pathology , Carcinoma, Ductal, Breast/radiotherapy , Carcinoma, Ductal, Breast/surgery , Carcinoma, Squamous Cell/pathology , Carcinoma, Squamous Cell/radiotherapy , Combined Modality Therapy , Electronics, Medical , Endometrial Neoplasms/pathology , Endometrial Neoplasms/radiotherapy , Feasibility Studies , Female , Hodgkin Disease/pathology , Hodgkin Disease/radiotherapy , Humans , Lymphatic Metastasis/radiotherapy , Neoplasms/pathology , Organ Specificity , Radiotherapy, Adjuvant , Rectal Neoplasms/pathology , Rectal Neoplasms/radiotherapy , Rectal Neoplasms/surgeryABSTRACT
The prone position can be used for the planning of adjuvant radiotherapy after conservative breast surgery in order to deliver less irradiation to lung and cardiac tissue. In the present study, we compared the results of three-dimensional conformal radiotherapy planning for five patients irradiated in the supine and prone position. Tumor stage was T1N0M0 in four patients and T1N1M0 in one. All patients had been previously submitted to conservative breast surgery. Breast size was large in three patients and moderate in the other two. Irradiation in the prone position was performed using an immobilization foam pad with a hole cut into it to accommodate the breast so that it would hang down away from the chest wall. Dose-volume histograms showed that mean irradiation doses reaching the ipsilateral lung were 8.3 ± 3.6 Gy with the patient in the supine position and 1.4 ± 1.0 Gy with the patient in the prone position (P = 0.043). The values for the contralateral lung were 1.3 ± 0.7 and 0.3 ± 0.1 Gy (P = 0.043) and the values for cardiac tissue were 4.6 ± 1.6 and 3.0 ± 1.7 Gy (P = 0.079), respectively. Thus, the dose-volume histograms demonstrated that lung tissue irradiation was significantly lower with the patient in the prone position than in the supine position. Large-breasted women appeared to benefit most from irradiation in the prone position. Prone position breast irradiation appears to be a simple and effective alternative to the conventional supine position for patients with large breasts, since they are subjected to lower pulmonary doses which may cause less pulmonary side effects in the future
