Diffusion-weighted imaging of tumor recurrencies and posttherapeutical soft-tissue changes in humans

The aim of this study was to examine soft tissue tumor recurrences and post therapeutic soft tissue changes in humans with a diffusion-weighted steady- state free precession (SSFP) sequence. Twenty-four patients with 29 patholo gies of the pelvis or the extremities were examined. The lesions were class ified as follows: group 1, recurrent viable tumors (n = 10); group 2, posto perative hygromas (n = 7); and group 31 posttherapeutic reactive inflammato ry muscle changes (n = 12). The sequence protocol in these patients consist ed of short tau inversion recovery images, T2-weighted spin-echo (SE), pre- and postcontrast T1-weighted SE images and the diffusion-weighted SSFP seq uence. The signal loss on diffusion weighting was evaluated visually on a f our-grade scale and quantitatively. The signal intensities were measured in regions of interest and a regression analysis was performed. Statistical a nalyses was performed utilizing the Student's t-test. The signal loss was s ignificantly higher for hygromas and edematous muscle changes than for recu rrent tumors (p < 0.001) indicating higher diffusion of water protons. The regression coefficient was -0.11 (mean) for tumors. Hygromas had a signific antly higher signal loss than inflammatory edematous muscle changes (p < 0. 01). The regression coefficients were -0.29 (mean) for hygromas and -0.22 ( mean) for edematous muscle changes. The SSFP sequence seems to be a suitabl e method for diffusion-weighted imaging of the musculoskeletal system in hu mans. These preliminary results suggest that the signal loss and the regres sion coefficients can be used to characterize different types of tissue.