ESTRO 38 Abstract book

S927 ESTRO 38

showed that already 99% of the suitable prostate carcinoma patients, but only 61% of the lung carcinoma patients are treated at the VERO. This and further diagnoses offered options for a more balanced occupancy of the institution’s Linacs. For better scheduling, the relevant tables of the Mosaiq database are visualized in a web application within the network of the institution as shown in fig.2. The output can be selected by the timeperiod, ICD-10 diagnose and Linac. Conclusion As a prove of concept the Mosaiq OIS was chosen, several questions have been answered and the result was validated. Currently, the Mosaiq queries are integrated with queries to the treatment-planning-system Pinnacle³ (Philips N.V., Amsterdam), the IMRT-verification systems ArcCHECK (Sun Nuclear GmbH, Neu-Isenburg) and Mobius3D (Mobius Medical Systems LP, Houston) allowing automated analysis of clinical parameters in large cohorts of patients. Including different data sources in a single setup is feasible for issues with the need of linking different data sets or processing vast amounts of data, which cannot be analyzed manually and reproducibly. BigData as well as machine learning applications are both in strong need for extensive and high quality data, therefore this approach is suitable.

Purpose or Objective This study was conducted to evaluate and apply dose influence of metal stent in photon and proton radiotherapy planning for hepatocellular carcinioma. Material and Methods Dose perturbations were evaluated by Monte Carlo simulation and Planning system in photon and proton. Computed tomography(CT) data sets of 1.25 mm slice thickness were obtained with containing metal stent in water equivalent solid phantom. The plan with and without metal stent consisting of nickel and titanium base alloys(Nitinol) was performed. We used Truebeam(Varian Medical System) and Pinnacle 3 (Philips Medical System) treatment planning system in photon and proton therapy system of Sumitomo and Raystation(Raysearch) treatment planning system in proton for dose calculation. The photon plan test are designed in an anterior-posterior/posterior- anterior (AP/PA) field technique using 6MV energy and proton plan are designed in AP field of Wobbling beam using 150 MeV energy. The Monte Carlo simulation was programed under same conditions for beam parameters, solid water phantom and metal stent of radiotherapy planning system and we compared the calculated dose distribution effects as with and without metal stent. The Monte Carlo was calculated using Geant4(v10.3) and GATE(v8.0). Results The thickness of the metal stent is about 0.1 mm. The stent appears blurred in the image because the stent is smaller than the size of the detector used in CT. In RTP, it was confirmed uncertainty for dose calculation that the image blurring of stent in CT can reconstruct the density of 1.08 ~ 1.3 g/cm 3 , which is much smaller than the actual density of 6.8 g/cm 3 . The treatment planning system cannot calculate dose perturbations due to stents. In the calculation of dose using Monte Carlo, dose enhance effect of photon was 1.6 ~ 3.0 % depending on the stent size due to multi scatter. The proton calculated dose reduction effect of -1.3 ~ 0.1% due to dose shadow. Conclusion Our study was performed to evaluate the uncertainty of dose calculations that could be caused by stents in radiotherapy planning and to apply them in clinical practice. In the Monte Carlo calculation, dose perturbations of 3.0% and -1.3% were observed with the use of metal stents in photons and proton. We confirmed the effect of dose change by metal stent through dose calculation and simulation. In case of RTP used in clinical practice, we can recommend to replace stent density to the average HU value of the surrounding normal tissue considering dose uncertainty by image blurring of stent that metal stent is not reflected in the planning system. EP-1721 Sensitivity study between gamma index passing rate and clinical dose volume histogram L. Szczurek 1,2 , R. Juszkat 3 , J. Szczurek 4,5 , P. Sosnowski 3,4 1 1st Department of Medicine, Poznan University of Medical Sciences, Poznan, Poland ; 2 The International Oncology Center Affidea, Poznan, Poland ; 3 Department of General and Interventional Radiology, Poznan University of Medical Sciences, Poznan, Poland ; 4 Affidea, Diagnostics Department, Poznan, Poland ; 5 Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences Purpose or Objective The sensitivity was analyzed to correctly identify the pre- treatment volumetric modulated arc therapy (VMAT) plans with high dose errors and to quantify the incidence of false negatives, for various the gamma index method. Material and Methods Twenty five high-risk prostate cancer patients and fifteen endometrial cancer patients treated with VMAT technique were analyzed. The percentage gamma passing rate (%GP) of two-dimensional (2D) and three-dimensional (3D) pre-

Electronic Poster: Physics track: Dose measurement and dose calculation

EP-1720 Evaluation of dose perturbations for metal stent in photon and proton radiotherapy planning H. Kim 1 , B. Lee 1 , S. Cho 1 , S. Jung 1 , Y. Han 1 , D. Lim 1 , H. Park 1 1 Samsung medical center, Radiation oncology, seoul, Korea Republic of