ESTRO 2022 - Abstract Book

S1464

Abstract book

ESTRO 2022

Results For GTVboost, PTV margins to ensure a minimum dose to the CTV of 95% for 90% of patients were 0.3cm, 0.8cm, and 0.3cm for the lateral, craniocaudal, and anteroposterior directions, respectively. The PTV margin to cover 90% of all fractions was 1.2cm for CTVelec. Conclusion The calculated PTV margins are less than the margins that are generally used in CBCT based EBRT boost treatments for rectal cancer patients. Therefore, implantation of BioXmark® fiducials and CBCT marker matching using these fiducials may allow for significantly increased dose escalation to target volumes and reduced dose to normal tissue compared to CBCT based boosting without fiducial implantation and could be an alternative to MRI-linac based boosting.

PO-1666 Results of a 2020 UK survey for the use of online treatment monitoring solutions for IMRT/VMAT

S. Stevens 1

1 The London Clinic, Medical Physics, London, United Kingdom

Purpose or Objective Numerous commercial technologies for online treatment monitoring (OTM) in radiotherapy (RT) are currently available including electronic portal imaging device (EPID) in vivo dosimetry (IVD), transmission detectors and log files analysis. Despite this, in the UK there exists limited guidance on how to implement and commission a system for clinical use or information about the resources required to set up and maintain a service. Materials and Methods A Radiotherapy Special Interest Group (RTSIG) working party, established by Institute of Physics and Engineering in Medicine (IPEM) was formed with a view to reassess the current practice for OTM in the UK and an aim to develop consensus guidelines for the implementation of a system. A survey distributed to Heads of Medical Physics at 71 UK RT departments investigated: availability of OTM in the UK; estimates of workload; clinical implementation; methods of analysis; quality assurance; and opinions on future directions. Results The survey achieved a 76% response rate and demonstrated that OTM is widely supported in the UK, with 87% of respondents indicating all patients should undergo OTM. EPID IVD (EIVD) was the most popular form of OTM. An active EIVD service was reported by 37% of respondents, with 84% believing it was the optimal solution. This demonstrates a steady increase in adoption since 2012. Other forms of OTM were in use but they had only been adopted by a minority of centres. Financial barriers and the increase of staff workload continue to hinder wider implementation in other centres. Device automation and integration is a key factor for successful future adoption and requires support between treatment machine and OTM manufacturers. Conclusion The survey has provided an updated analysis on the use of OTM methods across the UK. Future guidance is recommended on commissioning, adoption of local tolerances and root-cause analysis strategies to assist departments intending to implement OTM. Results have recently been published as a IPEM Topical Report: IPEM topical report: results of a 2020 UK survey for the use of online treatment monitoring solutions for IMRT/VMAT. Stevens SW, Moloney S, Bangiri A, Blackmore A, Hart C, Holmes-Smith W, Pooler A, Rixham P, Doolan PJ. Phys Med Biol. 2021 Oct 19. doi: 10.1088/1361-6560/ac311a. Online ahead of print. M. LIZONDO 1 , E. Gonzalez Lao 2 , L. Oraa López 3 , B. Parra Prieto 3 , C. Fabres Martín 3 , T. Ramírez 1 , D. Navarro 1 , J. García- Miguel 1 , E. Ambroa 1 , T. Valdivielso 1 , Á. Infiestas 1 , Á. Lorenzo 1 , U. Gallardo 1 , A. Peralta 1 , G. Frontera 1 , D. Amat 1 , A. López 1 , S. Almendros 4 , M. Ballesteros 2 , M. Parcerisa 1 , R. Pujol 5 , M. Colomer 5 1 Consorci Sanitari de Terrassa, Medical Physics Unit, Radiation Oncology Department, Terrassa, Spain; 2 Consorci Sanitari de Terrassa, Quality and Patient Safety Department, Terrassa, Spain; 3 Consorci Sanitari de Terrassa, Orthopedics and Traumatology Department, Terrassa, Spain; 4 Consorci Sanitari de Terrassa, Radiation Oncology Department, Terrassa, Spain; 5 Consorci Sanitari de Terrassa, Medical Physics Unit, Radiation Oncology , Terrassa, Spain Purpose or Objective The introduction of 3D printing in health has opened our minds to a world of endless possibilities. One of these is the use of personalized 3D printed bolus for their use in radiotherapy, to adapt perfectly to the surface of the patient during all treatment sessions. Its superiority over other commercial bolus has been largely tested. Customized medical devices are contemplated in the new Regulation (EU) 2017/745, requiring a risk analysis before their manufacture, to avoid any adverse event that may affect clinical safety. The purpose of this study is to analyze the possible risks in the 3D printed bolus, establish regulatory requirements, and ensure the safety of our patients. PO-1667 Risk management plan for the 3D printed bolus in radiotherapy