ESTRO 2024 - Abstract Book

S3842

Physics - Image acquisition and processing

ESTRO 2024

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1551

Digital Poster

Tumor hypoxia assessment using dual-energy CT derived iodine concentration in head and neck cancer

Jens Edmund 1,2 , Christian Maare 1 , Henriette Klitgaard Mortensen 1 , Kristin Skougaard 3 , Camilla Kjaer Lonkvist 1 , Laura Ann Rechner 1 1 Department of Oncology, Herlev & Gentofte Hospital, Herlev, Denmark. 2 Niels Bohr Institute, Copenhagen University, Copenhagen, Denmark. 3 Centre for Medicines Licensing, Human Medicines, Oncology, Danish Medicines Agency, Copenhagen, Denmark

Purpose/Objective:

Tumor hypoxia is a well-known negative prognostic factor in head and neck cancer (HNC) [1]. Hypoxia can be reliably imaged with PET-tracers such as 18 F-Fluoroazomycin-arabinoside (FAZA) [2] but these have found limited use in the clinic. In contrast, dual-energy CT (DECT) has recently become readily available clinically. In DECT, the iodine concentration (IC), visualizing the perfused blood volume, can be extracted. Here, we investigate the relationship between IC and hypoxia within the gross tumor volume (GTV) of tumors (GTV-T) and positive lymph nodes (GTV-N) in HNC patients.

Material/Methods:

6 HNC patients (pts 1-6) receiving radiotherapy (RT) underwent same-day corresponding DECT and FAZA PET scans in the beginning (session 1, pts 1-5), midway (session 2, all pts) and near-end (session 3, pts 1-3; 5-6) of the RT course. Each scanning session was separated by 14 days giving a total of 16 DECT-FAZA datasets when pooling all patients and sessions. The GTV-T, GTV-N, and a well-oxygenated neck muscle (M) were delineated at all scanning sessions. The IC maps (resolution 1x1x2 mm 3 ) were extracted using the Advanced Workstation v.3.2 (GE Healthcare), rigidly registered to the FAZA PET scans, and re-sampled to the lowest resolution of the FAZA (2x2x5 mm 3 ). Voxels were masked according to the delineated GTV-T, GTV-N, and M. Hypoxia was defined as voxels having a FAZA tumor-to-muscle (TMR) signal ratio > 1.2 as this is a well-established procedure in the literature [2,3]. The GTV volume, hypoxic fraction (HF), and IC mean and standard deviation (sd) were calculated for all of the scanning sessions.