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

METHODS: 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 (18)F-FDG PET (VOIDWI, VOIPET). Overlap between volumes was assessed as a percentwise overlap. (18)F-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.

RESULTS: Seventeen patients were available for correlation analysis, and 12 patients were available for assessment of tumor overlap. The median tumor overlap between VOIDWI and VOIPET was 82% (VOIDWI in VOIPET) and 62% (VOIPET in VOIDWI) 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.

CONCLUSION: In multiparametric imaging with the integrated PET/MR scanner, the VOIs from DWI and (18)F-FDG PET were both within the target volume for radiotherapy and overlapped substantially although not completely. No correlation between (18)F-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.