FDG-PET and diffusion-weighted MRI in head-and-neck cancer patients: implications for dose painting.

Abstract

PURPOSE

The purpose of this study was to investigate if FDG-PET and DWI identify the same or different targets for dose escalation in the GTV of HN cancer patients. Additionally, the dose coverage of DWI-targets in an FDG-PET-based dose painting plan was analyzed.

CONCLUSIONS

FDG-PET and DWI contain different information, resulting in different targets. Further information about failure patterns and dose relations can be obtained by adding DWI to currently ongoing dose painting trials.

RESULTS

The average maximum SUV was 13.9 and the mean ADC was 1.17 · 10(-3) mm(2)/s. The average ρ between SUV and ADC was -0.2 (range: -0.6 to 0.4). The ADC-targets were only partly overlapping the SUV(50%max)-target and the dose parameters were significantly smaller in the ADC-targets compared to the SUV(50%max)-target.

MATERIALS AND METHODS

Eighteen HN cancer patients underwent FDG-PET and DWI exams, which were converted to standardized uptake value (SUV)- and apparent diffusion coefficient (ADC)-maps. The correspondence between the two imaging modalities was determined on a voxel-level using Spearman's correlation coefficient (ρ). Dose painting plans were optimized based on the 50% isocontour of the maximum SUV ( SUV(50%max)). Dose coverage was analyzed in three different SUV- and three different ADC-targets using the mean dose and the near-minimum and near-maximum doses.