Methods and applications of diffusion imaging of vertebral bone marrow

Diffusion-weighted imaging (DWI) is an MRI technique that is sensitive to random water movements at spatial scales far below typical MRI voxel dimensions. DWI is a valuable tool for the diagnoses of diseases that involve alterations in water mobility. In the spine, DWI has proven to be a highly useful method for the differential diagnosis of benign and malignant compression fractures. In these pathologies, the microscopic structure of bone marrow is altered in a very different ways, leading to different water mobility, which can be depicted by DWI. Most of the pulse sequences developed for MRI can be adapted for DWI. However, these DWI-adapted sequences are frequently affected by artifacts, mostly caused by physiological motion. Therefore, the introduction of additional correction techniques, or even the development of new sequences is necessary. The first part of this article describes the principles of DWI and the sequences used for DWI of the spine: spin echo (SE), turbo spin echo (TSE), single-shot echo planar imaging (EPI), and steady-state free precession (SSFP) sequences. In the second part, clinical applications of DWI of the spinal bone marrow are extensively discussed.