ESTRO 2022 - Abstract Book

S1631

Abstract book

ESTRO 2022

Conclusion This study indicated differences in breast IMC radiotherapy practice among ATNEC participating centres in the UK . Although some centres routinely used field-based techniques, they implemented volume-based breast IMC radiotherapy through the trial QA programme. Findings from this pre-trial QA questionnaire provided reassurance that all ATNEC participating centres could comply the standards as required in the trial protocol.

PO-1836 The Clinical Effectiveness of SGRT on Extremities Patients: Accuracy and Potential Margins Reduction

Y. zhang 1 , F. Huan 1 , X. Feng 1 , F. Lu 1 , Z. Li 1 , G. Wei 1 , W. Li 1 , H. Li 1

1 Cancer Hospital, Chinese Academy of Medical Sciences, Radiation Oncology, Beijing, China

Purpose or Objective Unlike other body sites, extremities patient positioning is challenging due to lack of comprehensive immobilisation devices as well as familiarity of the staff experience. We would like to investigate if the newly installed SGRT system could be clinically useful for extremities patients in terms of accuracy and PTV margins reduction. Materials and Methods 24 random patients who were treated upper or lower extremities between September 2020 and August 2021 were analysed retrospectively. 12 patients in the control group (Group A) used the traditional setup method: lasers and skin markings (one anterior and two lateral). While the other 12 patients in the experimental group (Group B) used SGRT system (AlignRT, Vision RT) for patient setup. In Group B, all patients were aligned within 1mm and 1° tolerance. A total of 209 and 168 CBCT images were acquired for Group A and B respectively. Both translational and rotational shifts were recorded. The positioning errors ( Σ ± σ ): systematic errors ( Σ ) and random errors ( σ ) were calculated. Systematic error was defined as the standard deviation of individual mean positioning error; random error was defined as the root mean square of individual standard deviation positioning error. A formula of 2.5 Σ +0.7 σ was applied for CTV to PTV margins calculation. Results The positioning errors for Group A and B were (2.52±3.08)mm and (1.14±1.43)mm, (2.26±2.51)mm and (1.38±1.88)mm, (4.80±3.41)mm and (1.26±1.76)mm in x (lateral), y (longitudinal) and z(vertical) directions; (0.82±1.12)° and (0.71±0.69)°, (0.52±1.18)° and (0.89±0.82)°, (1.49±1.14)° and (1.11± 1.53)° in Rx (Pitch), Ry (Roll) and Rz (Yaw) directions. The percentages of translational and rotational distribution errors were shown in the table 1. The calculated CTV-PTV margins were 8.5mm, 7.4mm, 14.4mm and 3.9mm, 4.8mm, 4.4mm in x, y and z directions for Group A and B respectively. Table 1: The distribution errors of translational and rotational shifts.

Conclusion The use of SGRT can improve the positioning accuracy especially in lateral and vertical direction. Accurate and reproducible positioning could potentially reduce the PTV margins significantly for better side effects management.

PO-1837 Overwhelmed by information

G. Samsøe 1 , L. Gerberg 1 , M. Bruvo 1

1 University College Copenhagen, Faculty of Health, Department of Technology, Radiography, Copenhagen, Denmark

Purpose or Objective During radiotherapy course (RT) for head and neck cancer (HNC) in Denmark, there is a wide range of written information material available to patients in the form of leaflets and internet sites. Patients meet many different radiographers and other healthcare professionals who need to inform them about treatments and side effects. But do the patients have the ability to absorb the information at a given time? The aim of this study is to explore male HNC survivals experience of the distribution of information given during the RT and its influence on their quality of life.

Materials and Methods