ESTRO 2024 - Abstract Book

S4129

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2024

Online Adaptive Radiotherapy is a feasible, well tolerated, patient friendly and efficient technique for treatment of Cervical cancer, with reduced treatment related acute toxicities and increased patient compliance.

The On Couch Time can be optimized with experience and expertise.

PET CT based SIB facilitates dose escalation which can translate to an Increased BED, whilst ensuring no increase in toxicity, Which can translate into an increased local control.

Interim PET CT scans allow for adapting the contour based on the scan so as to precisely deliver the escalated dose to the metabolically active tumor volume.

Online adaptive RT is futuristic and with AI training, the process is expected to be more accurate thus improving the treatment quality.

The combination of both these techniques facilitates monitored precise dose escalation with maximal normal tissue sparing.

This proof of concept study requires validation with large number in randomized trial.

Keywords: INTERIMPETCT,Pelvic malignancies,

3233

Digital Poster

A method for accumulating dose-volume histograms based on assumptions of random motion

Øyvind L Rørtveit

Haukeland University Hospital, Department of oncology and medical physics, Bergen, Norway

Purpose/Objective:

The problem of calculating the accumulated dose over multiple CT scans (representing radiotherapy (RT) fractions) commonly occurs in applications relating to motion and uncertainty management. The most common measure used to interpret dose to a region of interest (ROI) is the dose-volume histogram (DVH). In the calculation of DVHs, the geometrical distribution of the dose is lost. Therefore, there is no correct way of accumulating DVHs from multiple fractions without additional information. A common procedure is to use deformable image registration to accumulate deformed dose matrices onto a reference ROI shape, and then calculate the resulting DVH of the ROI using the accumulated dose matrix. This procedure requires access to both structures and dose matrices as well as complex and time-consuming software for deformable registration. Since spatial information is lost in the calculation of DVHs, assumptions must be made when approximating the accumulation without this information. The accuracy of the approximation will depend on the appropriateness of the assumptions. The simplest approach is averaging the volume dose by dose. Implicitly, this approach makes the