ESTRO 2023 - Abstract Book

S552

Sunday 14 May 2023

ESTRO 2023

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Conclusion The result of this study indicates the feasibility of predicting intrafractional prostate motion from CBCT images with high accuracy of probabilistic predictions. However, it would require at least 1 fraction to be treated first. As such this may help with quality assurance tests and possibly improve patient’s overall treatments by implementing adaptive planning. PD-0661 Dosimetric comparison: Virtual Unenhanced Dual Energy CT versus contrast CT for treatment planning M. Afifah 1 , D. den Boer 1 , L. Bulthuis 1 , T. Rosario 1 , J. Verbeek-Spijkerman 1 , A. Bel 1 , Z. van Kesteren 1 1 Amsterdam UMC, Radiotherapy, Amsterdam, The Netherlands Purpose or Objective Iodine contrast is commonly used to aid CT delineation in radiotherapy. However, this contrast is not present during treatment. A commonly employed strategy to account for this, is by applying a density override to the contrast-enhanced structures (CES) during treatment planning. Dual-Energy CT (DECT) is an emerging CT technique with the capability of generating virtual unenhanced (VUE) reconstructions from contrast-enhanced acquisitions, removing iodine-contrast from the images, eliminating the need to manually remove the CES. An observation from VUE images is that regions outside the CES, e.g. bones, also encounter a reduction in CT intensity, see Figure 1. The aim of this study is to assess the dosimetric effect of such a CT number reduction for treatment planning dose calculations based on VUE images, compared to the clinically used contrast-enhanced CT. The assessment is done in order to evaluate the feasibility of VUE application in the RT workflow.