Visible light in IGRT: AlingRT
S. Cantera Cabañas, L. Parreño Romeu, F. Salvador, V. Laguna Molina, R. Martínez San Juan, N. Hidalgo Llopis, P. Calatayud Cuesta · Reports of Practical Oncology & Radiotherapy · 2013
Introduction.New treatment techniques based on intensity modulated (IMRT) improve the conformation of the dose distribution to the target volume, minimizing the absorbed dose in the organs at risk Due to the complexity of these techniques a pretreatment patient-specific quality control is necessary.Purpose.To implement a quality control procedure to ensure the agreement between the planned and the delivered treatment.Materials and methods.In our company there are available 2 Varian CLINAC 21EX accelerators and 1 Xio (Elekta) treatment planning system (TPS) To verify the absorbed dose, the treatment plan is calculated based on computed tomography (CT) images of the phantom I'mRT (Scanditronix-Wellhofer).After irradiating the treatment plan on the phantom, the measured dose at the isocenter is compared with the calculated dose from TPS using a 3D ionization camera PinPoint 0016 cc (PTW31016).A portal imaging device, EPID, (Portal Vision AS1000) is used to check the dose distribution.The treatment plan is calculated on the CT of the EPID and an integrated image of each beam is obtained.The correspondence between the pixel values and the dose is known by prior calibration of the EPID.Comparison between the measured dose distribution and the dose calculated from TPS is made with the software OmniPro I'mRT (IbaDosimetry).Results.The discrepancy between the dose measured by ionization chamber and the calculated dose should be less than ±3% for the acceptance of the treatment.The dosimetric distributions were evaluated using gamma analysis.Treatments are only accepted with gamma test results (3%, 3 mm) <1 higher than 95%.Conclusions.The procedure used for treatment verification has proved to be accurate, fast and simple.Moreover, EPID-based dosimetry allows immediate analysis of the results and presents the additional advantage of allowing separate evaluation of each beam's dose distribution.