Abstract Book

S176

ESTRO 37

succeed to irradiated mice that locally developed RILD associated fibrosis. Bringing together multiple expert form radiation oncology, animal radiation, cell transplantation, bioinformatics, liver biology, we succeed to identify putative RILD marker should allow to better describe RILD mechanistic and further evaluation of prophylactic and therapeutic interventions. SP-0331 Science slam: Report back from ESTRO mobility grants physics: Modern dose calculation algorithms in brachytherapy G. Fonseca 1 , S.L. Thrower 2 , K. Gifford 2 , F. Verhaegen 1 1 GROW-School for Oncology and Developmental Biology- Maastricht University Medical Center, Department of Radiation Oncology MAASTRO, Maastricht, The Netherlands 2 The University of Texas MD Anderson Cancer Center, Department of Radiation Physics, Houston, USA To calculate and compare two commercially available Model Based Dose Calculation Algorithms (MBDCA) and Monte Carlo (MC) simulations for an APBI brachytherapy case. Methods Oncentra ® brachy ver. 4.5 ACE (Advanced Collapsed cone Engine, Elekta AB, Stockholm, Sweden), Acuros™ BV ver. 13 (Varian Medical Systems, Inc., Palo Alto, CA) and MCNP ver. 6.1.1 were used to calculate dose for an APBI brachytherapy case. The input for all calculations was a clinical APBI brachytherapy case with the SAVI ® (Cianna Medical, Aliso Viejo, CA) device. The HU to density calibration curve from ACE was used for all calculations. AMIGOBrachy was used to convert the patient CT geometry into voxels to generate the input deck for MCNP and to convert ACE files into the Acuros format. DVHs, target coverage (V 90 , V 95 , and V 100 ), highest dose to normal breast tissue (V 150 , V 200 ) and critical structure doses (dose to the highest 0.1 and 1.0 cc volume D 0.1cc , D 1cc for skin and rib) were compared. Dose ratios were also computed and compared amongst the algorithms. Results: Results obtained using a uniform water medium (Dose-to-water-in-water, D w,w ) demonstrate agreement within 1.1 ± 1.2% (mean difference ± one standard deviation) for all the methods. Isodoses indicate agreement better than 0.3 mm (Figure 1a). This is impressive considering that Varian and Nucletron/Elekta HDR source designs are slightly different. The agreement is slightly worse 2.0 ± 2.2% (mean difference ± one standard deviation) comparing dose-to-medium-in- medium (D m,m ). Here isodose differences (Figure 1b) are visible near tissue interfaces (≈1.2 mm shift of 75% isodose line proximal to the skin surface). Table 1 shows less the 1.1% difference between the commercial algorithms and MC for the clinical dose metrics in water (D w,w ). Clinical dose metrics obtained using D m,m show up to 8.4% difference between the commercial algorithms and MC and 4.3% difference between ACE and Acuros. Larger differences were observed for lung due to material misassignment as a significant volume of the lung was automatically assigned as air in the commercial system while the lung was manually assigned in the MC interface. Abstract text Purpose

Conclusions D w,w

is very consistent between different algorithms while MBDCA and MC showed worse agreement. Tissue segmentation issues will most likely be part of the clinical routine soon and differences should be clarified so treatments from different centers, possibly using different commercial systems, can be compared. SP-0332 Science slam: Report back from ESTRO mobility grants RTT E. Strata 1 , M. Sarra Fiore 1 , B.A. Jereczek-Fossa 1 1 IEO - European Institute of Oncology, Radiotherapy, Milano, Italy Abstract text Report back from ESTRO Mobility Grants RTT E. Strata (1), M. Sarra Fiore (1), B.A. Jereczek-Fossa (1;2) 1 Division of Radiation Oncology, European Institute of ONCOLOGY, Milan Italy 2 Department of Oncology and Hemato-oncology, University of Milan, Italy There cannot be any limitations or borders in order to keep up with new technological innovations in the medical field and give our patients the best care they deserve. We can improve ourselves and our skills by observing and studying new realities and nonetheless, sharing ideas and knowledge with other professionals. Cultural exchange and interdisciplinary science are the basis to fulfill these purposes. Thanks to the Estro Mobility Grant I had the great opportunity of spending two weeks in Utrecht Medicine Center (UMC) Radiotherapy Department. The aim of my visit was to improve my knowledge of various imaging techniques and protocols currently used at the UMC Radiotherapy Department for IGRT treatments. Moreover, my ultimate goal was to be able to improve the approach to IGRT modality and protocol at the European Institute of Oncology in Milan, Italy. During my visit, I was significantly involved in observing various cancer treatments focusing on IGRT treatments and protocols that use on-line CBCT image guidance. I have improved my understanding of the way in which radiation therapists (RTTs) record and study the images acquired in order to correct the patient set-up. At UMC, RTTs are essential for the control and correction of the patient’s