High-Resolution Diffusion Tensor Imaging (DTI) of the Cervical Spinal Cord in the Setting of Spinal Cord Injury (SCI)

Spinal cord injury (SCI) can result from trauma as well as degenerative conditions, such as cervical spondylotic myelopathy (CSM). Both have a profound impact on the physical and mental health of the affected individual. The symptoms of CSM can include weakness in the arms or legs, difficulty with walking and balance, loss of dexterity in the hands, and bowel or bladder dysfunction. Traumatic spinal cord injury often includes damage to white matter tracts resulting in irreversible functional deficits such as paraplegia or quadriplegia. Although current diagnostic imaging can reveal highly specific parameters of spinal canal anatomy, the functional anatomy of the spinal cord remains unknown. Patients with similar diagnostic findings can vary clinically with many patients having minimal to no symptoms while others may be severely incapacitated. Conventional MRI methods, such as T1/T2 weighted MRI, may easily identify the region of the damage and may depict permanent changes in the spinal cord tissue. However, conventional MRI methods are limited in their ability to correlate imaging findings with short and long term functional outcomes from spinal cord injury. DTI has the potential to improve upon conventional MRI imaging by providing information about tissue microstructure and may be particularly well suited for assessing the integrity of fiber tracts in SCI. Diffusion tensor magnetic resonance imaging (DTI) is a new technique that is highly sensitive in detecting the integrity of white matter tracts. Although information obtained from DTI has been utilized for white matter abnormalities in the brain, DTI of the spinal cord in vivo has provided many challenges. The small size of the spinal cord and the close packing of its white matter tracts require a very high image resolution to visualize these individual tracts. The resolution required to image the small cross sectional area of the spinal cord has been difficult to achieve using most widely used DTI sequences. To date, DTI measurements reports have demonstrated a practical application of DTI on the cervical spinal cord with limited spatial resolutions from 8 mm3 to 16 mm3. To achieve high-resolution DTI of the spinal cord, two novel imaging techniques for high-resolution in-vivo DTI on a clinical 3T MRI system (Trio, Siemens Medical Solution, Erlangen Germany) have been developed: 2D singleshot Interleaved Multiple Inner Volume DWEPI (ss-IMIV-DWEPI) and 3D singleshot DW STimulated EPI (3D ss-DWSTEPI). These optimized DTI pulse sequences have typically achieved approximately 2.0 or 1.253 mm3 spatial resolution within clinically achievable imaging time (\~5 min.). The sequences have been designed especially for high-resolution DTI of cervical spinal cord. They have been applied to spinal cord specimens ex vivo as well as to a small group of healthy volunteers and multiple sclerosis patients.