Reduced field-of-view diffusion-weighted MRI can identify restricted diffusion in the spinal cord of dogs and cats with presumptive clinical and high-field MRI diagnosis of acute ischemic myelopathy

Diffusion-weighted imaging MRI is the gold standard imaging technique for diagnosis of suspected acute brain ischemia in dogs and cats; however, it is technically challenging to apply to spinal cord imaging, due to its very small size, the inherent low spatial resolution of diffusion-weighted imaging, and the marked distortion resulting from magnetic field inhomogeneities caused by the osseous components of the vertebral column surrounding the spinal cord. Ischemic myelopathy is a common cause of acute non-compressive myelopathy in dogs and cats. Technological improvement in diffusion-weighted imaging pulse sequences allow imaging at smaller field of view with better spatial resolution and less image distortion. We sought to evaluate reduced field-of-view diffusion-weighted imaging MRI using a dedicated proprietary pulse sequence (FOCUS, General Electric) in a small sample of dogs and cats with a presumptive clinical and MRI diagnosis of acute ischemic myelopathy that were imaged with this pulse sequence. Five dogs and two cats fitted these inclusion criteria. In all of them, hyperintense spinal cord parenchyma signal was seen on diffusion-weighted imaging images corresponding to decreased signal on apparent diffusion coefficient map indicative of restricted diffusion, consistent with ischemia and cytotoxic edema. These areas matched the areas of abnormal T2-weighted signal and cord swelling observed on conventional spinal MRI. This small exploratory descriptive study indicates feasibility and possible usefulness of reduced field-of-view diffusion-weighted imaging MRI in dogs and cats with suspected acute ischemic myelopathy and that it may be added to the imaging protocol of the spine in such patients in an appropriate clinical setting.