Benign versus metastatic vertebral compression fractures: combined diffusion-weighted MRI and MR spectroscopy aids differentiation.

Abstract

To determine the residual lipid fraction in fractured vertebrae by (1)H MR spectroscopy (MRS) and its confounding effect on differentiating benign from metastatic compression fractures of the spine using apparent diffusion coefficient (ADC) obtained by diffusion-weighted read-out-segmented echo-planar imaging. Fifty-two patients presenting with back pain and/or vertebral compression fractures related to different degrees of acute trauma, osteoporosis or clinically known metastatic disease underwent imaging at 1.5 T using (a) single-voxel MRS for water and lipid compositions over the fractured vertebral marrow, and (b) DWI at b = 0 and 650 s/mm(2) to compute the ADC values. In 46 fractured vertebrae, the amount of lipid displaced was variable. In low-impact trauma, lipid was either displaced partially (ADC of 1.60 ± 0.20 × 10(-3) mm(2)/s) or almost totally with a higher ADC (2.20 ± 0.27 × 10(-3) mm(2)/s). In acute high-impact trauma, the lipid fraction was negligible, yet an intermediate ADC was observed. In tumour infiltration, ADC was also intermediate (1.22 ± 0.14 × 10(-3) mm(2)/s) despite a negligible lipid fraction. The ROC curve yielded a diagnostic accuracy of 0.944. ADC-MRS analysis provides knowledge of the residual lipid fraction in fractured vertebrae that could aid in the differentiation between benign and metastatic vertebral fractures in low-impact trauma.