Feasibility of Multiparametric Imaging with PET/MR in Head and Neck Squamous Cell Carcinoma

The purpose of this study was to investigate and assess the correlation and reproducibility of multiparametric imaging in head and neck cancer patients.

Twenty-one patients were included in this prospective scan-rescan study. All patients were scanned twice on an integrated PET and MRI scanner. Gross tumor volumes were defined on T2-weighted MR images, and volumes of interest were defined on diffusion-weighted MRI and ¹⁸F-FDG PET (VOI_DWI, VOI_PET). Overlap between volumes was assessed as a percentwise overlap. ¹⁸F-FDG uptake and diffusion were measured using SUV and apparent diffusion coefficient, and correlation was tested across and within patients and as a voxel-by-voxel analysis.

Seventeen patients were available for correlation analysis, and 12 patients were available for assessment of tumor overlap. The median tumor overlap between VOI_DWI and VOI_PET was 82% (VOI_DWI in VOI_PET) and 62% (VOI_PET in VOI_DWI) on scan 1 and scan 2, respectively. Across patients, the correlation between SUV and apparent diffusion coefficient was weak and nonsignificant. However, in individual patients a weak but significant correlation was identified on a voxel-by-voxel basis.

In multiparametric imaging with the integrated PET/MR scanner, the VOIs from DWI and ¹⁸F-FDG PET were both within the target volume for radiotherapy and overlapped substantially although not completely. No correlation between ¹⁸F-FDG uptake and DWI could be found across patients, but within individual patients a statistically significant, but weak, voxel-by-voxel correlation was found. The findings suggest that information on glucose uptake and diffusion coefficient carries complementary information of interest that may be relevant for radiotherapy treatment planning.