Does the SUVmax of FDG-PET/CT Correlate with the ADC Values of DWI in Musculoskeletal Malignancies?

Purpose: To evaluate the correlation of maximum standardized uptake values (SUVmax) of 18F-Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) with the apparent diffusion coefficient (ADC) of diffusion weighted imaging (DWI) in musculoskeletal malignancies. Methods: Institutional ethics committee approved this retrospective study. Twenty-seven patients (mean age: 44.85 ± 24.07; 17 men and 10 women) with a total of 29 musculoskeletal tumors underwent both FDG-PET/CT and DWI between January 2017 and March 2020. Region-of-interest (ROI)-based maximal standardized uptake values (SUVmax) of the tumors were measured on FDG-PET/CT images. Two radiologists measured lesions’ mean and minimum apparent diffusion coefficient (ADCmean and ADCmin) using five distinct ROIs on DWI images. Pearson correlation analysis was used to assess the correlation between SUVmax and ADC values. Results: There were 18 soft tissue tumors (62.1%) and 11 bone tumors (37.9%) with a mean maximum diameter of 9.4 ± 6.2 cm. The mean SUVmax, ADCmean and ADCmin of the whole lesions were 12.93 ± 9.63, 0.85 ± 0.28 × 10–3mm2/s and 0.61 ± 0.27 × 10–3mm2/s, respectively. SUVmax had a weak correlation with tumor maximum diameter (r = 0.378, p = 0.043), whereas ADCmean and ADCmin had none. There was strong inverse correlation between SUVmax and both ADCmean (r = –0.616, p < 0.001) and ADCmin (r = –0.638, p < 0.001). Conclusion: In musculoskeletal tumors, quantitative markers of FDG uptake and diffusion restriction strongly correlate.