MR-IMAGING OF EDEMA ACCOMPANYING BENIGN AND MALIGNANT BONE-TUMORS

To evaluate the incidence, quantity, and presentation of intra- and ex traosseous edema accompanying benign and malignant primary bone lesion s, the magnetic resonance (MR) studies of 63 consecutive patients with histologically proven primary bone tumors were reviewed. MR scans wer e assessed for the presence and quantity of marrow and soft tissue ede ma and correlated with peroperative findings, resected specimens and f ollow-up data. The signal intensity and enhancement of tumor and edema prior to and after intravenous administration (if any) of gadolinium- labled diethylene triamine pentaacetate (Gd-DTPA) was analyzed. Marrow edema was encountered adjacent to 8 of 39 malignant tumors and 14 of 24 benign lesions. Soft tissue edema was found accompanying 28 of 39 m alignancies and 10 of 24 benign disorders. On unenhanced T1-weighted M R images tumor and edema were difficult to differentiate. Tumor inhomo geneity made this differentiation easier on T2-weighted sequences. In 36 patients the contrast medium Gd-DTPA was used. Edema was present in 27 of these patients and the respective enhancement of tumor and edem a could be compared. Edema always enhanced homogeneously, and in most cases it enhanced to a similar degree as or more than tumor. Marrow an d, more specifically, soft tissue edema is a frequent finding adjacent to primary bone tumors. The mere presence and quantity of marrow and soft tissue edema are unreliable indicators of the biologic potential of a lesion. Unenhanced MR scans cannot always differentiate between t umor and edema, but the administration of Gd-DTPA is of assistance in differentiating tumor from edema. Awareness of marrow and/or soft tiss ue edema adjacent to bone lesions is of importance because edema can b e a pitfall in the diagnostic work-up and staging prior to biopsy or s urgery.