A survey of practice patterns for real-time intrafractional motion-management in particle therapy

Abstract

Background and purpose: Organ motion compromises accurate particle therapy delivery. This study reports on the practice patterns for real-time intrafractional motion-management in particle therapy to evaluate current clinical practice and wishes and barriers to implementation.

Materials and methods: An institutional questionnaire was distributed to particle therapy centres worldwide (7/2020-6/2021) asking which type(s) of real-time respiratory motion management (RRMM) methods were used, for which treatment sites, and what were the wishes and barriers to implementation. This was followed by a three-round DELPHI consensus analysis (10/2022) to define recommendations on required actions and future vision. With 70 responses from 17 countries, response rate was 100% for Europe (23/23 centres), 96% for Japan (22/23) and 53% for USA (20/38).

Results: Of the 68 clinically operational centres, 85% used RRMM, with 41% using both rescanning and active methods. Sixty-four percent used active-RRMM for at least one treatment site, mostly with gating guided by an external marker. Forty-eight percent of active-RRMM users wished to expand or change their RRMM technique. The main barriers were technical limitations and limited resources. From the DELPHI analysis, optimisation of rescanning parameters, improvement of motion models, and pre-treatment 4D evaluation were unanimously considered clinically important future focus. 4D dose calculation was identified as the top requirement for future commercial treatment planning software.

Conclusion: A majority of particle therapy centres have implemented RRMM. Still, further development and clinical integration were desired by most centres. Joint industry, clinical and research efforts are needed to translate innovation into efficient workflows for broad-scale implementation.

Keywords: Image-guided particle therapy; Intrafraction motion; Particle/proton therapy; Real-time respiratory motion management; Rescanning.

Fig. 1

(a) Overview of RRMM implementation globally (N = 68) and (b) the situation of rescanning implementation (Q11: Are you applying re-scanning for any treatment site?).

Fig. 2

Percentage of active RRMM users (globally, N = 44) using different motion mitigations for various mobile treatment sites (Q13: Do you perform active RRMM for any treatment site in your particle facility?/Q14: Which treatment site are you treating with active RRMM?).

Fig. 3

Status and wishes for the future regarding the RRMM technique for various mobile treatment sites, reported for active RRMM users only (globally, N = 44). Comparing two adjacent bars shows the difference between currently applied technique and what active RRMM users wish to implement for a particular treatment site. (Q17: Which active RRMM technique do you use currently/would like to use in the future?).

Fig. 4

Usage of different motion monitoring signals for (a) guiding active RRMM delivery and (b) conducting 4DCT reconstruction. (Q20: Which motion monitoring signal are you using to guide the active RRMM procedure?/Q21: Which motion monitoring signal are you using for 4DCT sorting/reconstruction?).

Fig. 5

Scoring (median) of the main barriers to (a) extend or change the active RRMM technique for a site currently treated with RRMM and (b) to implement RRMM for a new treatment site.

Fig. 6

Summary of the most important conclusions from 3 round DELHI consensus analysis. Green box summarizes the vision, yellow boxes for general requirements and orange boxes for priorities. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)