ESTRO 2024 - Abstract Book

S3844

Physics - Image acquisition and processing

ESTRO 2024

When the width of the IC distribution (quantified by IC sd) is either equal to or half of the mean IC uptake for GTV-N and GTV-T, respectively, tumor cells seem well oxygenated. Hereafter, the IC distribution decrease exponentially with increasing hypoxia.

Figure 2: GTV iodine metrics vs. HF for GTV-T (closed circles) and GTV-N (open circles) for all patients and scans (16 in total). A: IC mean in [mg/cc]. B: IC sd in [mg/cc]. C: IC sd/IC mean [dimless]. Mono-exponential fits are made for GTV-T and GTV-N separately (full lines).

Conclusion:

The GTV and HF decrease with the prescribed dose although fluctuations are observed during the course of RT. The IC sd/mean ratio was found to decrease exponentially with HF. The decrease is different for the GTV-T and GTV-N, respectively, which could be ascribed to conditions specific for the local tumor micro-environment. We further hypothesize, that the narrowing in IC distribution with increasing hypoxia towards a more uniform IC uptake, could be related to the oxygen diffusion limit around the blood vessels. Further voxelwise analysis will be conducted.

Keywords: hypoxia, dual-energy CT, head-and-neck cancer

References:

[1] Nordsmark M, Overgaard J. A confirmatory prognostic study on oxygenation status and loco-regional control in advanced head and neck squamous cell carcinoma treated by radiation therapy. Radiother Oncol 2000;57:39–43.

[2] Zschaeck S, Löck S, Hofheinz F, Zips D, Saksø Mortensen L, Zöphel K, et al. Individual patient data meta-analysis of FMISO and FAZA hypoxia PET scans from head and neck cancer patients undergoing definitive radio-chemotherapy. Radiother Oncol 2020;149:189–96. https://doi.org/10.1016/J.RADONC.2020.05.022. [3] Zegers CML, van Elmpt W, Szardenings K, Kolb H, Waxman A, Subramaniam RM, et al. Repeatability of hypoxia PET imaging using [18F]HX4 in lung and head and neck cancer patients: a prospective multicenter trial. Eur J Nucl Med Mol Imaging 2015;42:1840–9. https://doi.org/10.1007/S00259-015-3100-Z.