Comparison of sources of exit fluence variation for IMRT
| Autor: | Peter B. Greer, Joseph K Gardner, Song Wang, Luke Clews, J. James. Gordon, Jeffrey V. Siebers |
|---|---|
| Rok vydání: | 2009 |
| Předmět: |
Quality Control
Materials science Radiological and Ultrasound Technology business.industry Maximum deviation Uncertainty Radiotherapy Dosage Fluence Imaging phantom Standard deviation Beam delivery Treatment delivery Humans Radiology Nuclear Medicine and imaging In patient Radiotherapy Intensity-Modulated Artifacts Nuclear medicine business Quality assurance Simulation |
| Zdroj: | Physics in Medicine and Biology. 54:N451-N458 |
| ISSN: | 1361-6560 0031-9155 |
| DOI: | 10.1088/0031-9155/54/19/n03 |
| Popis: | The fluence exiting a patient during beam delivery can be used as treatment delivery quality assurance, either by direct comparison with expected exit fluences or by backprojection to reconstruct the patient dose. Multiple possible sources of measured exit fluence deviations exist, including changes in the beam delivery and changes in the patient anatomy. The purpose of this work is to compare the deviations caused by these sources. Machine delivery-related variability is measured by acquiring multiple dosimetric portal images (DPIs) of several test fields without a patient/phantom in the field over a time period of 2 months. Patient anatomy-related sources of fluence variability are simulated by computing transmission DPIs for a prostate patient using the same incident fluence for 11 different computed tomography (CT) images of the patient anatomy. The standard deviation (SD) and maximum deviation of the exit fluence, averaged over 5 mm x 5 mm square areas, is calculated for each test set. Machine delivery fluence SDs as large as 1% are observed for a sample patient field and as large as 2.5% for a picket-fence dMLC test field. Simulations indicate that day-to-day patient anatomy variations induce exit fluence SDs as large as 3.5%. The largest observed machine delivery deviations are 4% for the sample patient field and 7% for the picket-fence field, while the largest difference for the patient anatomy-related source is 8.5%. Since daily changes in patient anatomy can result in substantial exit fluence deviations, care should be taken when applying fluence back-projection to ensure that such deviations are properly attributed to their source. |
| Databáze: | OpenAIRE |
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