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Spinal Cord Injury: Progress, Promise, and Priorities
Unlike MRI, fMRI, and CT scans, PET scans detect and localize specific naturally occurring proteins; molecules, such as sugars and water; and other substances, such as neurotransmitters, which have been modified to emit radioactive energy.
At present, PET scans are not commonly used in the clinic to assess spinal cord injuries. However, as discussed below, the technology has much potential to provide researchers and clinicians with a means by which to visualize changes in gene expression in the spinal cord.
Next Steps: Future Imaging Technologies
Imaging technologies provide clinicians with important tools to gauge the responses of patients to different therapies (Jacobs et al., 2003). The creation of sensitive assays that merge image-based technologies with biomarker research will allow investigators and clinicians to use specific tracers to localize molecular, genetic, and cellular processes in real time, thus providing further insight into the biological processes that affect the progression of the injury (Blasberg and Gelovani, 2002).
As of January 2005, no clinical studies in the United States were specifically examining the use of imaging marker technologies for the study of spinal cord injuries. In comparison, markers are used to assess the state of MS and Alzheimer’s disease and imaging techniques are used to monitor the effects of different treatments for these conditions. For example, imaging assays are being developed to visualize specific neurotransmitter levels and to determine if they are involved in memory loss (Brown et al., 2003).
The Future of Magnetic Resonance Technology
In animals with syringomyelia, diffusion-weighted MRI, which is sensitive to the diffusion or random motion of water molecules in tissue, can detect cystic lesions in the gray matter of the spinal cord (Schwartz et al., 1999). The increased sensitivity offered by diffusion-weighted MRI will enable physicians to detect specific complications of spinal cord injuries sooner, thus increasing the potential for treatment.
Magnetic resonance technology can be adapted to provide more than diagnostic information about the structural changes occurring in response to a spinal cord injury. In 2001, Bulte and colleagues used magnetic resonance to track oligodendrocyte stem cells that were prelabeled with super paramagnetic iron oxide nanocomposites, which are small beads invisible to the naked eye that can be detected by MR technology (Bulte et al., 1999, 2001). Using this approach, the investigators were able to track the real-time migration and integration of these oligodendrocyte stem cells for up to 6 weeks in the same animal, which is important for distinguishing the