Whole-body MR-DWIBS vs. [18F]-FDG-PET/CT in the study of malignant tumors: a retrospective study

Our aim was to assess the overall diagnostic accuracy of magnetic resonance diffusion-weighted whole-body imaging with background signal suppression (MR-DWIBS) compared with ([(18)F]-fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT), considered the reference standard of whole-body tumour imaging modalities, in a series of consecutive patients with malignant tumour.

Thirty-eight patients diagnosed with a malignant tumour over a 4-month period were enrolled in this retrospective, observational study. PET/CT and MR-DWIBS images were reviewed in double-blind manner by a nuclear medicine physician and radiologists with 4 years experience. Lesion size, standard uptake value (SUV) and apparent diffusion coefficient (ADC) were measured and calculated for each lesion.

The qualitative analysis of MR-DWIBS and [(18)F]-FDG-PET/CT showed that two patients were negative at both techniques. MR-DWIBS was positive in 36 patients, 34 of whom were positive and two negative at [(18)F]-FDG-PET/CT, respectively. Two hundred and fifty-five lesions were identified by MR-DWIBS and 184 by [(18)F]-FDG-PET/CT, which was a significative discordance. Correlation between SUV and ADC of lesions positive at both techniques was not statistically significant. The mean difference between lesion size in [(18)F]-FDG-PET/CT and MR-DWIBS was not statistically significant. No correlation was found between glucose metabolism and water motion.

MR-DWIBS may be used to evaluate localisation of parenchymal neoplasms but is less efficacious in characterising lymph-node and skeletal lesions. [(18)F]-FDG-PET/CT remains the best whole-body technique to identify lymph-node and skeletal lesions, but its limitation is identifying tumours with low glucose metabolism as in mucinous neoplasms. MR-DWIBS evaluation must be integrated with morphological images to increase MR diagnostic accuracy.