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Diagnostic Value of Increased Diffusion Weighting of a Steady-state Free Precession Sequence for Differentiating Acute Benign Osteoporotic Fractures from Pathologic Vertebral Compression Fractures

Andrea BaurGo,a, Armin Hubera, Birgit Ertl-Wagnera, Roland Dürra, Stefan Zyska, Susanne Arbogasta, Michael Deimlinga and Maximilian Reisera

a From the Departments of Diagnostic Radiology (A.B., A.H., B.E-W., M.R.), Orthopaedic Surgery (R.D., S.Z.), and Pathology (S.A.), University of Munich, Germany; and Siemens Medical Systems, Erlangen, Germany (M.D.).



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  		FIG 1. A–C, At {delta} = 3 ms, the bone marrow contrast has negative values (mean, -0.16; SD, 0.45) for osteoporotic fractures (group 1) and positive values (mean, 2.19; SD, 1.35) for tumorous fractures (group 2) (A). This represents the hypointense signal in benign versus hyperintense signal in malignant fractures and is statistically different at P < .001. However, there is a small overlap between the maximum values of osteoporotic fractures and the minimum values of malignant fractures at {delta} = 3 ms. This overlap is reduced with increasing diffusion weighting at {delta} = 6.0 and 9.0 ms, owing to a signal reduction in benign osteoporotic fractures (B and C).



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  		FIG 2. A, T1-weighted SE image (450/12) in an 84-year-old man with a compression fracture of the seventh thoracic vertebral body. The fracture occurred in the absence of trauma.

B, Complete replacement of the bone marrow space. STIR image (3600/60, TI = 150) shows hyperintensity in the fractured vertebral body. Note also the focal hyperintensities in the sixth thoracic vertebra (top arrow) anteriorly and in the 11th thoracic vertebra posteriorly and adjacent to the endplate (bottom arrow).

C, SSFP sequence with very low diffusion weighting ({delta} = 0.6 ms) shows hyperintense signal in the fractured vertebral body.

D–F, Increased diffusion weighting with the SSFP sequence (D = 3 ms, E = 6.0 ms, F = 9.0 ms) shows substantial signal loss in the fractured vertebral body. The fractured vertebral body is isointense at {delta} = 3 ms and markedly hypointense at {delta} = 6.0 and 9.0 ms. The diagnostic value of increased diffusion weighting is the signal loss in benign bone marrow edema. Note that the focal areas of hyperintensity on the STIR images are also hypointense on the SSFP sequence, indicating benign edema.

G, Follow-up MR study 8 months later shows healing of the fracture with restitution of fat cells.



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  		FIG 3. 62-year-old man with a vertebral fracture due to a metastasis of a transitional cell carcinoma in the fifth thoracic vertebral body.

A, Hypointensity in the vertebra on T1-weighted SE images.

B, Corresponding STIR image (3600/60, TI = 150) shows homogeneous high signal intensity in the fractured vertebral body.

C–F, SSFP image of the same slice with increasing diffusion weighting (C = 0.6 ms, D = 3.0 ms, E = 6.0 ms, and F = 9.0 ms). The signal intensity is markedly hyperintense at {delta} = 0.6 to 6.0 ms and hyperintense at {delta} = 9.0 ms. There is a signal loss in the overall image with high diffusion weighting at {delta} = 9.0 ms. Note the focal area of hyperintensity in the seventh thoracic vertebral body posteriorly (arrow, C). This represents a fat island, because it is hyperintense on T1-weighted SE images and hypointense on STIR images. Fat has an extremely low diffusion coefficient and shows no signal loss on diffusion-weighted images.





Copyright © 2009 by the American Society of Neuroradiology. Print ISSN: 0195-6108 Online ISSN: 1936-959X