ESTRO 2024 - Abstract Book

S6030

RTT - Treatment planning, OAR and target definitions

ESTRO 2024

Keywords: Bilateral breast cancer, VMAT, 3D conformal

3105

Digital Poster

Impact of multi-modality imaging (MR/CT) on RT planning volumes for pancreatic ductal adenocarcinoma

Aileen Duffton 1,2 , Laura Grocutt 3,2 , Lynsey Devlin 1,2 , Derek Grose 4,2

1 Beatson West of Scotland Cancer Centre, Radiotherapy, Glasgow, United Kingdom. 2 University of Glasgow, Institute of Sciences, Glasgow, United Kingdom. 3 Beatson West of Scotland Cancer Centre, Department of Clinical Physics and Bioengineering, Glasgow, United Kingdom. 4 Beatson West of Scotland Cancer Centre, Clinical Oncology, Glasgow, United Kingdom

Purpose/Objective:

Multi-modality imaging has the potential to improve the visualisation of pancreatic ductal adenocarcinoma (PDAC) and nearby structures, often difficult to define on CT alone. Delineation of PDAC lesions are challenging, with structure definition affected by low tissue contrast. Delineations are susceptible to inter-observer variation (IOV), with previous work in CT delineation demonstrating the impact on clinical outcomes (1,2). The aim was to investigate the impact of registered-MR/CT on RT planning volumes for PDAC, by assessing (i) volumetric difference and (ii) overlap between clinical oncologist (CO) and clinical oncology trainees (COtrain) with a gold standard (GS) when using CT and MR images.

Material/Methods:

Patients treated with RT for PDAC who had MR and CT for RT planning were included.

Patients fasted for 2 hours prior to scanning (images acquired in breath hold (BH)), dilute oral contrast administered 10 minutes before CT). An MR was acquired after 3D-contrast enhanced-CT (3DCECT), in the same position. FIESTA 4mm and Axial FIESTA 4mm FS sequences were acquired on a GE Signa HDxt 1.5T (GE Medical Systems) were acquired. Test patients were created in Eclipse V15 (Varian Medical Systems, Palo Alto). GS delineations were completed jointly by a CO and a radiologist, and CO and COtrain observers were given test cases and delineation instructions. No previous diagnostic image reports were available, only limited clinical information. Stage 1. Each observer delineated GTV and ITV structures (GTV_3D, GTV_exhale, GTV_inhale, GTV_MR, GTV_MRCT, ITV_CT, ITV_MR) on the 3D-CECT_BH RT planning scans for each test case using standardised structure sets and nomenclature (Table 1).