[Intensity modulated radiation therapy: analysis of patient specific quality control results, experience of René-Gauducheau Centre]. / Radiothérapie conformationnelle avec modulation d'intensité: analyse des résultats des contrôles précliniques, expérience du centre René-Gauducheau.

PURPOSE: Systematic verifications of patient's specific intensity-modulated radiation treatments are usually performed with absolute and relative measurements. The results constitute a database which allows the identification of potential systematic errors. MATERIAL AND METHODS: We analyzed 1270 beams distributed in 232 treatment plans. Step-and-shoot intensity-modulated radiation treatments were performed with a Clinac (6 and 23 MV) and sliding window intensity-modulated radiation treatments with a Novalis (6 MV). RESULTS: The distributions obtained do not show systematic error and all the control meet specified tolerances. CONCLUSION: These results allow us to reduce controls specific patients for treatments performed under identical conditions (location, optimization and segmentation parameters of treatment planning system, etc.).

[Validation of intensity modulated radiation therapy patient plans with portal images]. / Validation des plans de radiothérapie conformationnelle avec modulation d'intensité avec les images portales.

The goal of this study was to show the feasibility of step and shoot intensity-modulated radiation therapy pre-treatment quality control for patients using the electronic portal imaging device (iViewGT) fitted on a Sli+ linac (Elekta Oncology Systems, Crawley, UK) instead of radiographic films. Since the beginning of intensity-modulated radiation therapy treatments, the dosimetric quality control necessary before treating each new patient has been a time-consuming and therefore costly obligation. In order to fully develop this technique, it seems absolutely essential to reduce the cost of these controls, especially the linac time. Up to now, verification of the relative dosimetry field by field has been achieved by acquiring radiographic films in the isocenter plane and comparing them to the results of the XiO planning system (Computerized Medical Systems, Missouri, USA) using RIT113 v4.1 software (Radiological Imaging Technology, Colorado, USA). A qualitative and quantitative evaluation was realised for every field of every patient. A quick and simple procedure was put into place to be able to make the same verifications using portal images. This new technique is not a modification of the overall methodology of analysis. The results achieved by comparing the measurement with the electronic portal imaging device and the calculation with the treatment planning system were in line with those achieved with the films for all indicators we studied (isodoses, horizontal and vertical dose profiles and gamma index).