Set-up errors analyses in IMRT treatments for nasopharyngeal carcinoma to evaluate time trends, PTV and PRV margins
| Autor: | Franceschini Marzia, Giancarlo Zonca, V. Mongioj, Carlo Fallai, Patrizia Olmi, Emanuele Pignoli, Ester Orlandi, Mauro Palazzi, Elena Deponti, Claudia Sangalli, C. Stucchi |
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| Rok vydání: | 2010 |
| Předmět: |
Adult
Male Time Factors medicine.medical_treatment Population Planning target volume medicine Humans Radiology Nuclear Medicine and imaging education Aged education.field_of_study Phantoms Imaging Time trends business.industry Radiotherapy Planning Computer-Assisted Carcinoma Nasopharyngeal Neoplasms Radiotherapy Dosage Hematology General Medicine Middle Aged Intensity-modulated radiation therapy medicine.disease Radiation therapy Oncology Nasopharyngeal carcinoma Head and Neck Neoplasms Digitally reconstructed radiographs Female Anthropomorphic phantom Radiotherapy Intensity-Modulated Nuclear medicine business |
| Zdroj: | Acta Oncologica. 50:61-71 |
| ISSN: | 1651-226X 0284-186X |
| Popis: | the aims of this study were to analyze the systematic and random interfractional set-up errors during Intensity Modulated Radiation Therapy (IMRT) in 20 consecutive nasopharyngeal carcinoma (NPC) patients by means of Electronic Portal Images Device (EPID), to define appropriate Planning Target Volume (PTV) and Planning Risk Volume (PRV) margins, as well as to investigate set-up displacement trend as a function of time during fractionated RT course.before EPID clinical implementation, an anthropomorphic phantom was shifted intentionally 5 mm to all directions and the EPIs were compared with the digitally reconstructed radiographs (DRRs) to test the system's capability to recognize displacements observed in clinical studies. Then, 578 clinical images were analyzed with a mean of 29 images for each patient.phantom data showed that the system was able to correct shifts with an accuracy of 1 mm. As regards clinical data, the estimated population systematic errors were 1.3 mm for left-right (L-R), 1 mm for superior-inferior (S-I) and 1.1 mm for anterior-posterior (A-P) directions, respectively. Population random errors were 1.3 mm, 1.5 mm and 1.3 mm for L-R, S-I and A-P directions, respectively. PTV margin was at least 3.4, 3 and 3.2 mm for L-R, S-I and A-P direction, respectively. PRV margins for brainstem and spinal cord were 2.3, 2 and 2.1 mm and 3.8, 3.5 and 3.2 mm for L-R, A-P and S-I directions, respectively. Set-up error displacements showed no significant changes as the therapy progressed (p0.05), although displacements3 mm were found more frequently when severe weight loss or tumor nodal shrinkage occurred.these results enable us to choose margins that guarantee with sufficient accuracy the coverage of PTVs and organs at risk sparing. Collected data confirmed the need for a strict check of patient position reproducibility in case of anatomical changes. |
| Databáze: | OpenAIRE |
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