ESTRO 36 Abstract Book

S643 ESTRO 36 _______________________________________________________________________________________________

RAD AB, Sweden) and compared to a reference scan taken at the beginning of each session. The Catalyst TM system works through an optical surface scanning with LED light (blue: λ = 450 nm) and reprojection captured by a CCD camera (green: λ = 528 nm; red: λ = 624 nm), which provide target position control during treatment delivery. For 3D surface reconstruction, the system uses a non-rigid body algorithm to calculate the distance between the surface and the isocenter and using the principle of optical triangulation. Three-dimensional deviations and relative position differences during the whole treatment fraction were calculated by the system and analyzed statistically. Results Overall, the magnitude of the deviation vector showed a mean change of 1.3 mm +/- 0.4 mm (standard deviation) and a median change of 1.1 mm during dose application (beam-on time only). Along the lateral and longitudinal axis changes were quite similar (0.9 mm +/- 0.3 mm vs. 0.9 mm +/- 0.5 mm), on the vertical axis the mean change was 1.1 mm +/- 0.3 mm. The mean net beam-on time of radiation therapy was 2.8 minutes. There was no linear correlation between the length of the fraction and the magnitude of deviation. Pearson’s correlation coefficient between mean time and mean magnitude of deviation vector over all patients was 0.25 (p-value= 0.175). Conclusion Mean real-time intrafraction motion was within two millimeters in all directions and is therefore of minor clinical relevance in postoperative radiotherapy of breast cancer. EP-1187 Heart dose evaluation in two free-breathing and deep-breathing modes of breast cancer patients R. Anbiae 1 , A.R. Taji 1 , A. Ahmari 1 , Z. Siavashpour 2 , M. Beigi 1 1 Shahid Beheshti Medical University, Radiation Oncology, Tehran, Iran Islamic Republic of 2 Shahid Beheshti University, Medical Radiation Engineering, Tehran, Iran Islamic Republic of Purpose or Objective To investigate how much respiratory manner of breast cancer patients during external beam radiotherapy would 21 patients with left breast cancer underwent CT simulation without contrast in one day and two positions; breath hold and free breathing, prospectively. Two CT image sets were imported to treatment planning system (Eclipse, version 6). Volumes of PTV (that included breast and chest wall), heart and ipsilateral lung in both image sets were contoured by an individual radiation oncologist. An experienced physicist designed the plans for both CTs. Prescribed dose was 50 Gy in 25 fractions for all included cases. Plans were then confirmed by the oncologist and heart and lung dose volume parameters were exported. Lung and heart Volumes, their V30 and V22.5 and also mean heart dose (MHD) in two condition were studied and analyzed. Results Mean age of patients was 46.9±12.1.Twelve patients had done MRM and 9 of them had done BCS. Mean heart volume, its V30, V22.5 and MHD in two breathing conditions, breath hold and free breathing, were 519±108 and 526±107 (P=0.545), 1.89±2.41 and 62.88±2.04 (P=0.030) , 2.41±2.68 and 4.35±3.42 (P=0.048) and 0.98±0.7 and 1.42±0.5 (P=0.002), respectively. Also left lung volume and V30 of lung in breath hold and free breathing modes were 1763±315 and 1114±219 (P<0.001) and 8.72±3.27 and 8.92±4.29 (P=0.819) respectively. Person correlation did not show linear relation between lung volume and its mentioned DVH parameters; for MHD obtained r=-0.421 (P=0.057), for heart V30 and V22.5 affect their heart dose. Material and Methods

obtained r=-0.500 (P=0.021) and obtained r=-0.371 (P=0.097) and also, for heart volume r=0.032 (P=0.889). Conclusion All MHD and heart V30 and V22.5 variables were significantly higher with deep breathing in our study. It was shown that irritated heart volume was reduced significantly in this condition. V30 of lung were lower in deep breathing so deep breathing can be efficient method in left breath teletherapy. EP-1188 DIBH radiotherapy in left-sided breast cancer patients using an optical surface scanning system S. Schönecker 1 , M. Pazos 1 , P. Freislederer 1 , D. Reitz 1 , H. Scheithauer 1 , S. Corradini 1 , C. Belka 1 1 LMU University of Munich, Radiation Oncology, Munich, Germany Purpose or Objective There is a potential for adverse cardiovascular effects in long-term breast cancer survivors following adjuvant radiotherapy (RT). For this purpose, the deep inspiration breath-hold technique (DIBH) has been introduced into clinical practice, to maximally reduce the radiation dose to the heart. In the present study radiotherapy in DIBH was applied using the optical surface scanning system A total of 38 patients with left-sided breast cancer following breast conserving surgery were analysed. Normofractionated and hypofractionated radiotherapy protocols were eligible for this prospective clinical trial. Patient surface data and respiratory parameters were acquired using the laser surface scanner Sentinel TM (C-RAD AB, Uppsala, Sweden) during CT acquisition in free breathing (FB) and DIBH. Dual treatment plans were created and dosimetric output parameters of organs at risk were compared using Wilcoxon signed-rank test. For treatment application the optical surface scanner Catalyst TM (C-RAD AB, Uppsala, Sweden) was used and gating control was performed with an individual audio and video glasses-based feedback system. The Catalyst TM is interconnected to the LINAC systems via a gating interface and allows for a continuous and touchless surface scanning. Results Following initial patient training and treatment setup, radiotherapy in DIBH with the Catalyst TM /Sentinel TM system was time-efficient and reliable. 30 of 38 patients were treated using normofractionated treatment protocols. In these patients, the reduction of the mean heart dose for DIBH compared to FB was 43.2 % (2.45 to 1.39 Gy; p < 0.001). The maximum doses to the heart and LAD were reduced by 47.2 % (41.3 to 21.8 Gy; p < 0.001) and 61.7 % (31.2 to 11.9 Gy; p < 0.001), respectively. For 8 hypofractionated regimes the reduction of the mean heart dose for DIBH compared to FB was 50.1 % (2.13 to 1.06 Gy; p = 0.012). The maximum doses to the heart and LAD were reduced by 49.7 % (38.8 to 19.5 Gy; p = 0.012) and 77.3% (29.9 to 6.8 Gy; p = 0.012), respectively. Overall, also the mean lung dose and the V20 of the ipsilateral lung were significantly lower (-16.1 % and -17.8 %) for DIBH (Lung Mean 6.64 Gy; Lung V 20 = 11.7 %) compared to FB (Lung Mean 7.92 Gy; Lung V 20 = 14.2 %; p each <0.001). Conclusion The Catalyst TM /Sentinel TM system enabled a fast and reliable application and surveillance of DIBH in daily clinical routine. Furthermore, the present data confirm that using the DIBH technique during RT could significantly reduce high dose areas and mean doses to the heart. Catalyst TM /Sentinel TM . Material and Methods