ESTRO 2021 Abstract Book

S1402

ESTRO 2021

Conclusion In order to generate pCT from prostate MRI for dose calculation, the Pix2Pix with the perceptual loss function and the ResNet 9 blocks generator provides a MAE of 30 HU. This MAE value shows a high precision of the generated pCTs. The next step will be an evaluation of dose uncertainties for generated pCTs. PO-1678 simulation of low-dose cone beam CT for paediatric image-guided proton beam therapy J. Lindsay 1 , A. Bryce-Atkinson 1 , S. Meara 2,1 , D. Lines 3 , M. van Herk 1,4 , M. Aznar 1,4 1 The University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom; 2 The Christie NHS Foundation Trust, Radiotherapy, Manchester, United Kingdom; 3 The Christie NHS Foundation Trust, Proton Therapy, Manchester, United Kingdom; 4 The Christie NHS Foundation Trust, Radiotherapy Research, Manchester, United Kingdom Purpose or Objective CBCT is used in image-guided proton beam therapy (IGPT) to reduce positioning errors and detect anatomical changes. In children, CBCT is often used sparingly due to dose concerns. In IGPT, anatomical changes are of particular importance due to potential range effects. Lower dose CBCT would allow for more frequent imaging – ensuring accurate treatment delivery while reducing overall dose burden. In this work, we present a novel offline simulation and reconstruction method for low-dose CBCT, solving for unique reconstruction problems in a commercial IGPT system, and present a preliminary visual grading analysis (VGA) study on simulated low- dose patient images. Materials and Methods All CBCT images were acquired with the Varian Probeam (Varian Medical Systems, Palo Alto, USA) on-board