ESTRO 38 Abstract book

S1199 ESTRO 38

E-posters RTT

the treatment rooms was analyzed by using the independent T-test of SPSS Vision18 software. Results In rooms 1 and 2 with the wobbling system, the waiting time without and with time-dividing in one work day are 60.84±10.52 and 45.36± 0.17 minutes ( p =0.173). In rooms 1 and 2 with the pencil beam system, the waiting time without and with time-dividing in one work day are 56.58±3.42 and 48.02±6.70 minutes ( p =0.249). With all four treatment rooms simultaneous operation, the waiting time without and with time-dividing in one work day are 58.71±6.85 and 46.70±4.16 minutes ( p =0.024). In rooms 1, 2, 3, and 4, the waiting time without and with time- dividing in one work day are 52.37±17.32 and 44.63±13.25 minutes ( p <0.05), 66.67±19.86 and 45.00±12.95 minutes ( p <0.05), 54.37±16.81 、 45.26±10.42 minutes ( p <0.05), and 57.04±22.89 and 43.70±12.64 minutes ( p <0.05), respectively. The percentages of waiting time more than 60 minutes without and with time-dividing are 35.2% and 16.7%, respectively. Conclusion In proton therapy, the use time-dividing could reduce the patient's waiting time, decrease the discomfort of patients, minimize the random error of treatment, and improve the stability. EP-2171 Optimizing individual customized neck rests for proton therapy of brain tumors A. Schouboe 1 , M. Gioertz 1 , P. Randers 1 , A. Harboell 1 , C.R. Hansen 1 , A. Vestergaard 1 1 Aarhus University Hospital, Danish Center for Particle Therapy, Aarhus N, Denmark Purpose or Objective To study the reproducibility of individually customized neck rests for positioning patients with brain tumors undergoing irradiation in a Proton Centre. The Head and Neck board (HN board) is designed with an indentation for positioning the neck rest which has smooth sloping surfaces to ensure no steep gradients related to proton therapy. The system could potentially introduce an error in positioning of the individually customized neck rests. The purpose of this study was to evaluate the use of two neck rests with respect to displacement, ease of use and patient comfort. Material and Methods Individual customized neck rests from two different manufactures (A and B) were tested on 5 healthy volunteers. One individual customized neck rest from each manufacture was customized for each volunteer. The volunteer was positioned on the HN board with the head in neutral neck position. In customizing individually neck rest we focused on comfortable and adequate support to the neck with no gaps underneath the head or neck. The aim was to create a neck rest as homogenous as possible in order to avoid large abrupt density variations, which for proton treatments can reduce plan robustness. The volunteer was immobilized with a thermoplastic mask. A Beekly spot was placed underneath the HN-board and defined as reference. Two Beekly spots were placed in the same longitudinal plan as the reference and two on the cranial part of the neck rest (Fig 1). To evaluate the reproducibility of the positioning of the neck rests, the volunteer was re-positioned and a MRI scan was performed. Results A total of 10 MRI were evaluated. The mean longitudinal shifts were 1.4 mm (range 0.2-2.3 mm) and 1.3 mm (range 0.9-1.0 mm) for neck rest A and B, respectively. The cranial markers revealed no significant rotational error in positioning. The staff's main experience was to be extremely watchful when customizing the neck rest to make sure the material fitted in the indentation of the HN board to avoid the neck rests from being displaced. They

Electronic Poster: RTT track: Patient preparation, positioning and immobilisation

EP-2169 Are treatment times with breast DIBH comparable to free breathing? D. Ledsom 1 , V. Acton 1 , R. Biggar 1 1 Clatterbridge Cancer Centre, Department of Radiotherapy, Bebington- Wirral, United Kingdom Purpose or Objective The use of deep inspiration breath hold (DIBH) at the author’s centre was extended to treat all breast cancer patients irrespective of laterality or nodal status in March 2017. This audit investigated the duration of treatment before and after implementation of the DIBH technique for all breast cancer patients to determine if the standard 15 minute appointment slot was still achievable. Material and Methods Varian Aria reports (v13.6) was used to identify treatment start and end time for all breast cancer patients treated March 2016 to February 2017 (left DIBH, right free breathing (FB)) and April 2017 to March 2018 (right and left DIBH). Data from March 2017 was excluded due to crossover of techniques. Results For all breast patients treated between March 2016- February 2017 (n=801, right sided FB, left sided DIBH) median treatment time was 12m:08s (SD 5:09) compared to 12m:47s (SD 5:22) when all patients were treated in DIBH (n=1288, April 2017-March 2018). Data was stratified by laterality to compare FB and DIBH treatment times. For FB (n=418), median treatment time was 11m:50s (SD 5:01), versus DIBH (n=610) 12m:56s (SD 5:27). The difference was statistically significant (p<0.01). Outliers were excluded from data. Conclusion Median treatment time increased by 1 minute with DIBH; although this was statistically significant it was not clinically significant as there was no substantial increase in treatment time and the 15 minute appointment slot was achieved. DIBH treatment time therefore does not impact on capacity or extend appointment times. EP-2170 Scheduling optimization to reduce patient waitting beam times in four-room proton therapy center C.Y. Lin 1 1 Chang Gung Memorial Hospital, Radiation Oncology, Taoyuan, Taiwan Purpose or Objective In proton therapy, patients are required to lie flat and wait on the treatment bed for the conversion of the beam before treatment. The displacement resulted from maintaining the posture with long time might lose the advantages of proton therapy. This study attempts to use the time difference to reduce wait time and provide the stability of the treatment posture. Material and Methods We recorded patients’ waiting time from rooms 1 and 2 with the same wobbling system (Sumitomo Proton therapy System) and rooms 3 and 4 with the same pencil beam system. There were 27 working days for each time-dividing and non-time-dividing. For non-time-dividing, number of patients in room 1, 2, 3, and 4 are 262, 289, 219, and 231 and number of irradiation fields in room 1, 2, 3, and 4 are 528,584, 523, and 533, respectively. For time-dividing, number of patients in room 1, 2, 3, and 4 are 222, 210, 260, and 261 and number of irradiation fields in room 1, 2, 3, and 4 are 466,464, 682, and 621, respectively. The waiting time difference of time-dividing or not between