ESTRO 2024 - Abstract Book

S5899

RTT - Service evaluation, quality assurance and risk management

ESTRO 2024

1231

Digital Poster

Are Ring-Gantry Linacs Sufficient to Deliver a Modern Radiotherapy Service?

John McLellan 1 , Andrew Bromiley 1 , David Carnegie 1 , Polly Darby 1 , Adam El-Qmache 1 , Julie Fox 1 , Liam Murphy 1 , Richard Cheyne 1 , Catriona Burnett 2 , Nicola Miller 2 , Gillian McIntosh 2 , Diane Younger 2 , Natalie McLean 2 , Rafael Moleron 3 1 NHS Grampian, Radiotherapy Physics, Aberdeen, United Kingdom. 2 NHS Grampian, Radiotherapy, Aberdeen, United Kingdom. 3 NHS Grampian, Oncology, Aberdeen, United Kingdom

Purpose/Objective:

New ‘disruptive’ technologies often drive rapid changes in radiotherapy. For example, VMAT and IMRT treatments quickly replaced conformal treatments once dynamic treatments and inverse-planning became available. Now that MR linacs, ring-gantry linacs, and on-table re-planning have emerged, the potential exists for a rapid shift to on-line adaptive radiotherapy (oART) as a new standard of care. However, ring-gantry linacs currently offer only a single photon beam energy and they have no flattening filter, no couch rotation, and no electron beams. But the question arises: does a modern radiotherapy service actually require any of these functions? In preparation for replacing two of our three linacs with Varian Ethos systems, our department undertook an examination of all our clinical procedures. The aim was: (1) to redesign treatment processes for the new technology and (2) establish whether replacing all three linacs with ring-gantry systems was technically feasible.

Material/Methods:

We reviewed our workflows and identified six key elements that would be significantly impacted by having only ring gantry linacs:

1. We used planar imaging extensively for Image Guided Radiotherapy (IGRT) but only cone-beam CT (CBCT) images would now be possible. 2. Palliative treatments were often delivered with simple plain-field arrangements but no flattened fields would be available. 3. The use of electron beams were used for treating superficial lesions but no electron beams would be available. 4. Non-coplanar arcs were common but no table rotations would now be possible. 5. Long target volumes, e.g. for the treatment of limbs, often required extended distance but this would no longer be feasible. 6. SABR treatments require high numbers of MU but the dose-rate is lower for ring-gantry linacs than for FFF modes on typical C-arm linacs.

In each case, we investigated alternative approaches and, where possible, designed systems to overcome the limitations imposed by ring-gantry linacs.