ESTRO 36 Abstract Book

S960 ESTRO 36 _______________________________________________________________________________________________

1 La Fe University and Polytechnic hospital, Radiotherapy, Valencia, Spain 2 Clínica Benidorm, Radiotherapy, Benidorm, Spain 3 General University hospital, Radiation Oncology, Valencia, Spain 4 General University hospital, Medical Physics, Valencia, Spain 5 University of Valencia, Physiology, Valencia, Spain Purpose or Objective A risk analysis of the Total Skin Electron Irradiation (TSEI) technique was performed. The aim of this study was to evaluate the safety and the quality of the treatment process, as well as to adapt the quality assurance program according to the results. Material and Methods This revision has been executed in a reference center in the TSEI technique, with 80 patients treated following the method Stanford. The risk analysis was made following the methodology proposed by the TG-100 of the AAPM, which is an alternative procedure to the guidelines proposed by the ESTRO in the ACCIDRAD project. To this end, a multidisciplinary team developed the process map, outlining the stages of treatment and steps in which each stage is divided. The potential failure modes (FMs) of each step were proposed and evaluated, according their severity (S), occurrence (O) and detectability (D), with a scale from 1 to 10. The product of this factors resulted in its priority number risk (RPN), which enabled ranking the FMs. Then, the current quality management tools were examined and the FMs were reevaluated taking to account these tools. Finally, the FMs with RPN ≥ 80 were studied and new quality management tools to reduce its RPN were proposed. Results 75 steps contained in a total of 12 stages were observed. 361 FMs were evaluated, initially 103 had a RPN ≥ 80 and 41 had S ≥ 8. After, current management tools were considered, only 30 FMs had RPN ≥ 80 (Figure 1). Thereby, new control tools were derived from the study of these 30 FMs. The riskiest FMs were associated to the patient's position during treatment. For the "general body treatment" stage, the position of the screen and the patient was marked on the floor (Figure 2a) and some templates representing the position of the feet were drawn (Figure 2b). In addition, to facilitate positioning of the patient's limbs during “hands treatment” and “feet treatment” stages, the axes must traverse the lasers and the field size within which should position the extremities were marked on the sheet (Figure 2c). These new management tools have begun to be implemented in the facility.

Conclusion Thanks to this analysis, the steps of increased risk have been discovered and new quality management tools have been proposed. However, the multidisciplinary team will perform this analysis periodically to increase the safety and quality of TSEI treatment. EP-1745 EPID and Gantry sag characterization in Elekta LINAC F. Tato de las Cuevas 1 , J. Yuste Lopez 1 1 Hosp. Univ. de Canarias, Medical Physics Dept., Santa Cruz de Tenerife, Spain Purpose or Objective The EPID (Electronic Portal Imaging Device) is a well- known useful tool for LINAC QA (like MLC QA). The position of the EPID radiation center ( RC ) is crucial for this kind of tasks. The purpose of this study is analyse the mechanical performance of EPID and Gantry for LINAC QA with EPID. Material and Methods The LINAC used is an Elekta Synergy equipped with Agility MLC and iViewGT EPID and 6 MV photons energy.