Diffusion-weighted MR imaging offers no advantage over routine noncontrast MR imaging in the detection of vertebral metastases

Abstract

Background and purpose: Diffusion-weighted MR imaging of the spine has been used to differentiate benign from pathologic vertebral body compression fractures. We sought to determine the utility of diffusion-weighted MR imaging in the detection of vertebral metastases and to compare it with conventional noncontrast T1- and T2-weighted MR imaging.

Methods: Fifteen patients with metastases to the spine were studied using conventional MR imaging and diffusion-weighted imaging. Blinded review of all images was undertaken, and patients were categorized according to whether they had focal or multiple lesions. The signal intensity of the lesions was compared on T1-, T2- (fast spin-echo), and diffusion-weighted images.

Results: In five patients with focal disease, metastases were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 1), or hyperintense (n = 2) on T2-weighted images; and hypointense (n = 3) or hyperintense (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow. In 10 patients with disease in multiple sites, all lesions were hypointense on T1-weighted images; hypointense (n = 2), isointense (n = 4), hyperintense (n = 2), or mixed (n = 2) on T2-weighted images; and hypointense (n = 5), hyperintense (n = 3), or mixed (n = 2) on diffusion-weighted images with respect to presumed normal bone marrow.

Conclusion: As used in this study, diffusion-weighted MR imaging of the spine showed no advantage in the detection and characterization of vertebral metastases as compared with noncontrast T1-weighted imaging, but was considered superior to T2-weighted imaging.

Figures

fig 1.

Involvement of a single vertebra. A, Midsagittal T1-weighted image in a patient 6 months after spine radiation for breast metastases who presented with new pain and a positive radionuclide bone scan. This image shows hypointensity and partial wedge deformity of T7 (arrow). Note that vertebrae above and below the lesion are hyperintense as a result of prior radiation therapy. B, Corresponding T2-weighted image shows lesion (arrow) to be minimally hypointense with respect to presumed normal bone marrow above and below. C, Corresponding diffusion-weighted image shows that T7 (arrow) is hypointense relative to other vertebrae. Although the abnormality is perhaps seen better on diffusion-weighted image than on the T2-weighted image, the diffusion-weighted image is not superior to the T1-weighted image.

fig 2.

Patient with diffuse bone metastases from prostate cancer, with hypointensity on all sequences. A, Midsagittal T1-weighted image shows diffuse and mostly hypointense signal intensity in lower lumbar and sacral vertebrae. B, Corresponding T2-weighted image shows that the vertebrae are diffusely hypointense. C, Corresponding diffusion-weighted image shows that the vertebrae involved by metastases are hypointense. This hypointensity on all sequences could be related to sclerosis seen on radiographs of this region. The abnormality is more difficult to perceive on diffusion-weighted image than on T1-weighted image.

fig 3.

Patient with diffuse involvement from an unknown primary tumor, with hyperintensity on diffusion-weighted images. A, Sagittal T1-weighted image shows diffuse hypointense metastatic involvement. There are compression fractures involving T12, T9, L5, and L3. B, Corresponding T2-weighted image shows diffuse hyperintensity without focal lesions throughout all vertebrae visualized. C, Corresponding diffusion-weighted image shows that the diffuse lesions are mostly hyperintense with minimal patchy appearance. The lesions are better seen on the T1-weighted image than on the T2- and diffusion-weighted sequences.

fig 4.

Patient with diffuse involvement from lung cancer, with patchy hyperintensity on diffusion-weighted images. A, Sagittal T1-weighted image shows diffuse hypointensity throughout all visualized vertebral bodies. B, Corresponding T2-weighted image shows patchy areas of hyperintensity mixed with hypointense regions. C, Corresponding diffusion-weighted image shows patchy signal intensity throughout the vertebrae. The areas of increased signal intensity correspond to those seen on the T2-weighted image and, although more obvious on the diffusion-weighted image, the diffuse nature of disease is better seen on the T1-weighted image. The areas of hyperintensity on diffusion-weighted images are probably at least partially accounted for by shine-through artifact from the T2-weighted abnormalities. The inhomogeneous appearance of the CSF is due to the inherent sensitivity to macroscopic fluid motion of the type of diffusion-weighted imaging used in this study.