Musculoskeletal neoplasm: perineoplastic edema versus tumor on dynamic postcontrast MR images with spatial mapping of instantaneous enhancement rates.

PURPOSE: To evaluate the utility of fast, contrast-enhanced, sequential magnetic resonance (MR) imaging in differentiating between extraosseous tumor and perineoplastic edema.

MATERIALS AND METHODS: Fourteen patients underwent sequential MR imaging (3.5 seconds per image) after bolus administration of gadopentetate dimeglumine. Initial rates of enhancement (initial slope) were calculated on a pixel-by-pixel basis and displayed as a "slope image"' in which pixel intensity reflected the slope value. Close correlation with wedge biopsy specimens was performed.

RESULTS: Mean initial slope values were viable extraosseous tumor, 9.33 (standard deviation, 2.23); infiltrated muscle, 9.07 (2.31); edematous muscle without tumor infiltration, 5.48 (1.27); normal muscle, 1.11 (0.65). Differences in initial slope between all neoplastic and nonneoplastic tissues were statistically significant. Within individual patients, initial slope of edematous muscle was always 20% or more lower than that of neoplastic tissue. Slope images highlighted areas of viable extraosseous tumor and infiltrated muscle against edematous and normal tissues.

CONCLUSION: Computer-generated slope images derived from sequential postcontrast MR images allow differentiation between tumor and nonneoplastic edema and may thereby guide the surgeon in planning limb-sparing procedures.