Vertebrae adjacent to spinal bone lesion are inconsistent reference markers: A magnetic resonance spectroscopic viewpoint

Abstract

Purpose:To ascertain the suitability of vertebrae adjacent to spinal bone lesions as a signal intensity reference on MRI, and compare the MR spectroscopic appearance of vertebral body compression fractures due to malignant tumor infiltration, bone weakening (e.g., osteoporosis), and/or minor trauma. Materials and Methods:Twenty-five patients with spinal compression fractures underwent routine spinal MRI with an additional 1 H MRS study protocol to assess the percent fat fraction of the compressed vertebrae as well as the adjacent bony environment. Peak areas for water and total lipid were calculated from short-TE single-voxel 1 H MR spectra using the LCModel analyzing tool.Results: There were consistent water-only patterns in the fractured vertebra suggesting either near complete marrow replacement by malignant tissue or local edematous fluid/ hemorrhage within the marrow spaces. However, the adjacent vertebrae showed a wide range of patterns from a dominant lipid signal to the inverse of a pronounced water level. These results far exceed the normal variation expected based on age and sex. Conclusion:The results suggest that the adjacent vertebrae may not be an accurate reference, especially in diffusion-weighted imaging (DWI), because of the large difference between the two compartments. Furthermore, in the case of gradient-echo measurements, the in-phase vs. opposed-phase effects are significant. MR IMAGES OF SPINAL VERTEBRAE reflect signals from red marrow and yellow marrow (i.e., water and lipid protons, respectively) (1). Although they are separable in MR spectroscopic techniques, in MRI the two signals become mixed within pixels. Nevertheless, the relative water/lipid composition at a location in an image can be unraveled by the use of a number of contrast-weighted techniques (1). Interpreting MR images involves making decisions as to whether regions of interest (ROIs) are hypo-, iso-, or hyperintense, which requires the use of a reference region in the same image for distinction. One can usually make an unambiguous distinction if the reference is consistent. In the case of vertebral MRI, however, it is difficult to separate lesions based on relative signal intensities (or contrast) because the reference is a priori unknown (i.e., the relative water and lipid content of the "reference" bone marrow (adjacent vertebra) is variable). This is especially true for diffusion-weighted imaging (DWI) because an unknown lipid content will affect the image intensity, which serves as the reference. The discrepancy between DWI (which depends on a reference signal) vs. the apparent diffusion coefficient (ADC) (which focuses on the lesion only) has been highlighted in a few reports (2-4). Zhou et al (2) showed that although DWI alone did not allow discrimination between benign osteoporotic fractures and pathologic malignant vertebral fractures, an ADC analysis of these lesions resulted in an improved distinction between the two pathologies. In response to Ref. 2, Mulkern and Schwartz (5) emphasized the dependency of the A...

Combined intravoxel incoherent motion diffusion-weighted MR imaging and magnetic resonance spectroscopy in differentiation between osteoporotic and metastatic vertebral compression fractures

“…In our study, the value of FF in the malignant group was significantly lower than that in the benign group, which is consistent with the previous results [23, 24]. As fat content increase with age, the fat cells will replace the lost trabecular meshwork especially in osteoporosis patients.…”

Assessment of subchondral bone marrow lipids in healthy controls and mild osteoarthritis patients at 3T

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