ESTRO 37 Abstract book

S1200

ESTRO 37

PPC40 ionization chambers. For fields smaller than 5 cm x 5 cm, an ionization chamber IBA CC01, and IBA EFD and SFD diodes were also used. All field factors were also measured with Grafchromic EBT3 film. APEX reference field was 9.8 cm x 9.8 cm, with 12 cm x 14 cm as the field size fixed by the Agility MLC. Light – radiation coincidence, leaf transmission, interleaf leakage, radiation penumbra, and leaf positioning accuracy were measured using Grafchromic EBT3 film and read with FilmQAPro and ImageJ Software. Radiation penumbra have been analyzed as a function of field size, leaf positioning and depth of measurement, obtaining profiles in X and Y direction of rectangular fields. Results Figure 1 shows the differences obtained in Scp total scatter factor values obtained with the different chambers, diodes and film. For fields smaller than 1.96 cm x 1.96 cm, the volume averaging effect, lack of lateral electronic equilibrium and source obscuring effect causes the values measured with diode and film to be higher. For a 0.49 cm x 0.49 cm field, the result with EBT3 is 10% greater than that obtained with the SFD and EFD diodes, which provide similar results. This value is also a 34% and 54% superior than the one obtained with CC01 and CC13 ionization chambers.

and then determine the occurrence, severity and detectability level for each step. Obtain the RPN value multiplied by O, S, D for the values set by 1 medical physicist, 1 physician, 3 radiation therapist, 1 nurse, and 3 researchers. Analyze the RPN value and score for each individual deviation. Results According to the RPN value, the risk due to movement error of the treatment center coordinates was the largest at 95.8, and the CT origin identification step was 79.2 and the NPO and contrast agent side confirmation step was 58.5. The deviation of the score was as follows. The detectability was 0.74 ± 0.50, the severity was 1.82 ± 0.68, the occurrence was 1.25 ± 0.27. Conclusion In this study, RPN values at each stage were analyzed in order to identify high risk procedures in patient treatment and to identify risk factors. When analyze individual differences of scoring at each step, it is seen that the deviation of detectability is the smallest and the deviation of the severity is largest, so that the value itself is due to the order of S> O> D. In the present study, the stage of rectal cancer treatment is based on Gangdong Kyunghee University Hospital, and further studies are needed to standardize. EP-2169 Data quality of DICOM RT data bank and manually reported values – results from the DBCG HYPO trial C. Brink 1 , E.L. Lorenzen 2 , S.L. Krogh 2 , J. Westberg 2 , M. Berg 3 , I. Jensen 4 , M.S. Thomsen 5 , E.S. Yates 5 , B.V. Offersen 6 1 University of Southern Denmark, Institute of Clinical Research, Odense, Denmark 2 Odense University Hospital, Laboratory of Radiation Physics, Odense, Denmark 3 Vejle Hospital, Department of Medical Physics, Vejle, Denmark 4 Aalborg University Hospital, Department of Medical Physics, Aalborg, Denmark 5 Aarhus University Hospital, Department of Medical Physics, Aarhus, Denmark 6 Aarhus University, Institute of Clinical Medicine, Aarhus, Denmark Purpose or Objective Radiotherapy dose response models tend to rely on the entire dose distribution and not just few dose parameters. Currently, national DICOM RT banks are emerging to support access to the entire dose distribution. Data quality is obviously important within research, thus the data quality of the data banks should be evaluated. The current study reports the data quality of manually reported data versus data submitted to a national radiotherapy data bank. Material and Methods The current study is based on data from the 1522 Danish breast cancer patients, included in the DBCG HYPO trial. For all patients included in the trial specific dose parameters were prospectively reported manually. During the trial it was decided to utilize the national data bank for the Danish patients in the trial making it possible to compare the two data sets. In addition to dose parameters, laterality of the treatment (left/right), treatment arm (40/50 Gy), and whether a boost had been prescribed was extracted from the DICOM data in the data bank. Results Of all the categorical values (laterality, trial arm, and boost) there were only 25 inconsistencies between the manual and data bank values. The data bank contained the correct value for 23 of these inconsistencies. For the two remaining cases, the data bank stated incorrectly that a boost was not delivered. The two boosts were manually calculated electron boosts, and without a boost

Penumbra obtained at dmax depth, varies with field size, from 1.3 mm to 2.34 cm (X axis) and from 1.6 mm to 2.4 mm (Y axis), being invariant with the leaf position. Transmission and leakage complaint with vendor specifications, though an increment in transmission is observed where leafs close. Maximum deviation of the mechanic isocenter during a gantry rotation due to the APEX weight was 0.2 mm. Conclusion The mechanical and dosimetric parameters meet the manufacturer's specifications. Dual focusing provides consistent penumbra values for all field sizes. Leakage and transmission values do not reach 1%. For field factors, a combination of the values obtained with EBT3 and SFD diode seems the most suitable for its introduction in a planning system. EP-2168 Failure mode and effect analysis(FMEA) for rectal cancer 3D CRT N.H. Kwon 1 , W.K. Chung 1 , M.J. Chung 1 , E.S. Kim 2 , S.H. Choi 3 , D.O. Shin 4 , D.W. Kim 1 1 Kyung Hee University Hospital at Gangdong, Radiation Oncology, Seoul, Korea Republic of 2 Soonchunhyang University Hospital- Cheonan, Radiation Oncology, Seoul, Korea Republic of 3 Korea Institute of Radiological and Medical Science, Radiation Oncology, Seoul, Korea Republic of 4 Kyung Hee University Hospital, Radiation Oncology, Seoul, Korea Republic of Purpose or Objective A purpose of this study is scoring occurrence, severity and detectability for each stage of radiation therapy in rectal cancer, and analyze the cause, effect and risk of failure of the phase according to the RPN score. Material and Methods In radiotherapy for rectal cancer, list the steps from the treatment and outpatient part to the end of treatment,