ESTRO 2021 Abstract Book

S1550

ESTRO 2021

Conclusion Large intra-mandible differences in radio-sensitivity for ORN were observed. Dose effect relations were established for different regions of the mandible corresponding to dental elements. Extraction of the dental element of interest or its neighbors increased the local sensitivity of the mandible for ORN. These findings strongly support, and can guide studies to selectively spare sensitive regions of the mandible to decrease the risk of ORN. PO-1821 Impact of motion compensated reconstruction of 4DCT on radiomic features C. Sargeant 1 , A. Davey 1 , M. van Herk 1 , A. McWilliam 1 1 The University of Manchester, Division of Cancer Sciences - Faculty of Biology, Medicine and Health, Manchester, United Kingdom Purpose or Objective 4DCT is routinely used for imaging early-stage NSCLC patients treated with SABR. With individual 4D phases and reconstructions available, there is uncertainty surrounding the optimal 4DCT image for radiomics. We compare for the first time, the impact of motion compensated (MC) reconstructions with 4D phase selection on radiomic prediction of distant recurrence (DR). Materials and Methods 4DCT and follow-up data was collected for 262 NSCLC patients treated with SABR. Patients with tumour volumes ≤2cm³ and missing clinical data were excluded. The 4DCT scan consisted of 10 phases including end of exhale (T50) and peak inhale (T0). In-house software generated Mean and Median MC reconstructions. An in-house validated approach converted the clinical ITV into the GTV on T50, which was rigidly translated to T0 and MC scans before thresholding to provide a better GTV for each reconstruction (Fig.1A).