Diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration of the vertebral body.

OBJECTIVE: The aim of this study was to investigate diffusion-weighted MR imaging for differentiation of benign fracture edema and tumor infiltration with and without accompanying fracture.

SUBJECTS AND METHODS: In 10 volunteers, diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences were optimized on a clinical 1.5-T scanner. In 34 patients, MR imaging with and without diffusion-sensitizing gradients (b = 598 sec/mm(2) in spin-echo and fat-suppressed spin-echo, b = 360 sec/mm(2) in stimulated-echo) was performed. Thirty-five lesions were analyzed, with 18 caused by acute (< or =10 days old) osteoporotic or traumatic fractures and 17 caused by untreated malignant vertebral infiltration including nine fractures. Signal attenuation in diffusion-weighted images and contrast-to-noise ratio were calculated. The diffusion-weighted images were analyzed by two radiologists.

RESULTS: Images from three of 34 patients were excluded because of motion artifact. In osteoporotic and traumatic fractures, a strong signal attenuation of bone marrow edema was seen. In contrast to this, malignant-tumor infiltration caused only minor signal attenuation (p < 0.05), independent of accompanying pathologic fracture. All sequences showed identical changes of signal intensities. In four patients, initial diagnosis was changed by the findings in the diffusion-weighted images.

CONCLUSION: Diffusion-weighted spin-echo, fat-suppressed spin-echo, and stimulated-echo sequences are equally suitable for imaging of the spine. Calculation of signal attenuation and observation of signal characteristics allowed differentiation of benign fracture edema and tumor infiltration and provided excellent distinction between benign and malignant vertebral fractures in our series.