ESTRO 2022 - Abstract Book

S1633

Abstract book

ESTRO 2022

1 Cancer Hospital Chinese Academy of Medical Science,Shenzhen Center, Radiation Oncology, Shen Zhen, China

Purpose or Objective We would like to study if a systematic breathing coaching could improve the efficiency of left breast surface-guided DIBH (SG-DIBH) radiotherapy treatment. Materials and Methods 25 left breast DIBH patients, who were treated between June 2020 and May 2021, were divided into two groups. Group A (before March 2021) consisted of 13 patients which the CT simulation was done without systematic breathing coaching. While a systematic breathing coaching was conducted to 12 patients in Group B (after March 2021). Group A patients were only given simple breath hold instruction and repeated the breath hold for 3 times on the CT couch before the scanning. Before entering the CT simulation room, an educating video were shown to Group B patients to understand the rationales of DIBH and how to ensure a good breath hold during the scanning and treatment. Before the scanning, they had to repeat the breath hold on the CT couch for at least 5 times to ensure the reproducibility. Each breath hold had to last for at least 25 seconds. They were also instructed to practise at home for 10-15 minutes every day until the first day of the treatment. Both Group A and Group B patients were positioned using SGRT system (AlignRT, Vision RT, UK), 6-field IMRT treatment technique. The treatment times recorded by the machine (Varian, Palo Alto, CA) were retrieved. The treatment time was defined as the duration of CBCT scanning and beam on time of each treatment field, patient positioning time was not included. t-test was used for data analysis. Results The treatment time for Group A and B were 528.86±261.64 seconds and 448.06±159.89 seconds. p value is statistically significant (p<0.05). The average treatment time was reduced by 14.9%. Conclusion SG-DIBH treatment efficiency can be greatly improved with effective systematic breathing coaching implementation in the department. This will further enhance the patient’s treatment compliancy and experience as well.

PO-1840 The Feasibility of SGRT on Locally Advanced Cervical Cancer Patients with Bladder Protocol

Q. liu 1 , L. Su 1 , D. Tang 1 , Z. Wu 1 , Z. Yang 1 , H. Peng 1

1 Xiangya Hospital, Central South University, Department of Radiation Oncology, Changsha, Hunan, China

Purpose or Objective The use of SGRT on pelvis region has been a controversial discussion for the past few years. Bladder inconsistency and topography of pelvis region could be the root cause of the uncertainties including accuracy and reproducibility. Hence, we would like to study further if a good bladder management could improve the use of SGRT on cervical cancer patients. Materials and Methods 11 locally advanced cervical cancer patients who received concurrent chemoradiotherapy were enrolled and analyzed in this study. All patients were positioned in supine position. Patient’s bladder volume was measured with AvantSonic Z5 Bladder Scanner (AvantSonic Technology Co., Ltd) before treatment. The difference between the measured bladder volume and CT-sim bladder volume should be within ±15%. Then, patient was positioned based on isocenter skin markings (1 anterior and 2 laterals). The couch vertical value was kept the same as the latest CBCT couch acquired value. CBCT was taken and registration was performed accordingly. 3D translational and rotational shifts were recorded and applied. Next, SGRT system (OSMS, Varian, Palo Alto, CA) was activated to start monitoring. A standard recommended region of interest (ROI) was used across all patients, as shown in Figure 1. The 6DoF deltas shown on the SGRT system were recorded. The deltas represented the discrepancies between CBCT and the reconstructed 3D surface. The average, standard deviation and the error distributions were analyzed using ANOVA test and chi-square test with SPSS software (IBM corp.). A difference of P < 0.05 was considered statistically significant. Figure 1: Pelvis ROI