ESTRO 2023 - Abstract Book

S1597

Digital Posters

ESTRO 2023

Fig2: HN with kVp for adipose and cortical bone Dose distributions on the CIRS Phantom using Qr40 or Sm40 at different kVp showed the following mean differences for the PTV: D99% of -0.45% (s.d = 0.05), D50% of -0.07% (s.d. = 0.03) and D2% of -0.13% (s.d. = 0.06). Sm40 doses were lower than the Qr40 doses. Dose comparisons between Sm40 and Qr40 for the patient scans showed differences for the PTV; D99% mean = -0.30% (s.d.=0.48), D50% mean=-0.35% (s.d.=0.40) and D2% mean=-0.28% (s.d. 0.46). Doses for Sm40 were lower than Qr40 except for the brain scans.

Conclusion DirectDensityTM is found to be clinically acceptable for radiotherapy treatments. The HN-D curve is more linear and less energy dependent compared to the standard method.

Poster (Digital): Intra-fraction motion management and real-time adaptive radiotherapy

PO-1857 Impact of intra-fraction margin reduction for online adaptive bladder radiotherapy

H. Stankiewicz 1 , A. Mitchell 1 , R. Huddart 2 , M. Ingle 2 , S. Nill 1 , U. Oelfke 1 , A. Dunlop 1 , S. Hafeez 2

1 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, The Joint Department of Physics, London, United Kingdom; 2 The Royal Marsden NHS Foundation Trust and The Institute of Cancer Research, Radiotherapy, London, United Kingdom Purpose or Objective The bladder is a mobile, deformable radiotherapy target. Online adaptive radiotherapy strategies enable inter-fraction bladder variation to be addressed. Intra-fraction variation also needs consideration as the bladder volume increases over time. In this study we assess intra-fraction margin required for an online MR guided adaptive bladder radiotherapy workflow delivered within 20 minutes.

Materials and Methods