cused on spinal cord injuries but do offer potential for advances in this area. Additionally, NINDS put out a request for proposals (NINDS, 2001b) for studies designed to define gene expression profiles following traumatic spinal cord injuries.

Because the technologies used to identify biological markers can detect small but significant changes in gene expression, they are sensitive to slight variations in protocol. In fact, the gene profiles obtained from experimental studies are affected by differences in the instruments used to analyze the samples and by small changes in the ways in which samples are collected (e.g., the relative time after injury that tissue is collected, the location of the injury, and the quantity of the specimen) (Bareyre and Schwab, 2003). A standard set of methods is needed to minimize variability and maximize reproducibility (Bareyre and Schwab, 2003).

The spinal cord is embedded in bone and is surrounded by cerebrospinal fluid, which precludes direct visualization. The advent of neuroimaging techniques has allowed investigators to visualize the spinal cord so that they can begin to study the progression of spinal cord injuries. Magnetic resonance imaging (MRI) and computed tomography (CT) provide real-time information about the state of the injury and recovery. Moreover, imaging is noninvasive and the same region of the spinal cord can be repeatedly visualized to identify changes occurring over time. Imaging technologies, biomarkers, and molecular genetic technologies are being combined to provide researchers with powerful tools to monitor the progression of the injury and recovery through the visualization of specific molecular markers that define cellular events and functional changes.

MRI is a safe and noninvasive method of evaluating the spinal cord that provides detailed pictures of hard-to-view areas of the spine, including the spinal canal, vertebra, and soft tissue (Levitski et al., 1999). Clinicians use MRI after an individual has an acute spinal cord trauma to visualize the location and the extent of the spinal cord trauma and compressive lesions (e.g., blood clots) (AANS/CNS, 2002). It is superior to positron emission tomography (PET), CT, and other imaging technologies for the detection of abscesses or other masses near the spinal cord and is used to monitor patients with chronic compression injuries. However, imaging technologies have practical limits in the setting of acute spinal cord traumas, as a patient may not be stable enough to enter an MRI machine or may have other medical priorities that take precedence over receiving a detailed image of the spinal cord.

Functional MRI (fMRI) can provide second-by-second images of the brain to reveal changes in neuronal activity in response to different sensory