Magnetic Resonance Imaging
From Regence.com:
Conventional magnetic resonance imaging (MRI) systems acquire images with the patient in the recumbent, neutral position. Recently, a new fully open MRI system, the upright or positional MRI, has been developed which allows multiple position as well as recumbent imaging. This system allows partial or full weight bearing, as well as simultaneous kinetic maneuvers of the patient’s whole body or individual body parts.
It is theorized that imaging the body in positions related to the axial loading of the spine, which occurs when standing upright or sitting or in the specific position related to the patient’s clinical symptoms, may lead to more accurate diagnosis. This is being evaluated in patients with suspected nerve root compression and in some cases of spondylolisthesis and may be particularly relevant in cases where disease is not visible on a recumbent MRI.
FONAR Corporation has 510(k) marketing clearance from the U.S. Food and Drug Administration (FDA) for a MRI system that performs positional MRI scans.
Policy/Criteria
Positional or upright MRI for the diagnosis and management of any condition, including, but not limited to cervical, thoracic or lumbosacral back pain, is considered investigational.
Scientific Background
Validation of any new imaging technique involves the following steps:
1. Demonstration of its technical feasibility, including assessment of its reproducibility and precision. For comparison among studies, a common standardized protocol is necessary.
2. Establishment of normal and abnormal values as studied in different clinical situations. For accurate interpretation of study results, sensitivities, specificities, and positive and negative predictive values compared to a gold standard must be known.
3. Assessment of the clinical utility of both positive and negative tests. The clinical utility of an imaging study is related to how the results of that study can be used to benefit patient management. Relevant outcomes of a negative test (i.e., suspected pathology is not present) may be avoidance of more invasive diagnostic tests or avoidance of ineffective therapy. Relevant outcomes of a positive test (i.e., suspected outcome is present) may also include avoidance of a more invasive test plus the institution of specific, effective therapy.
In evaluating this approach to imaging, it is important to first determine if positional MRI results in additional findings. However, it is also important to determine if treatment of these additional findings results in improved outcomes. This second step is important given the previously described false positive findings of MR imaging of the spine. Jarvik and colleagues reported that many MR imaging findings have a high prevalence in subjects without low back pain and that findings such as bulging discs and disc protrusion are of limited diagnostic use.(2) They also reported that the less common findings of moderate or severe central stenosis, root compression, and disc extrusion were more likely to be clinically relevant.
A number of studies have reported that positional MRI can identify abnormalities in patients where conventional (supine) MRI did not identify significant abnormal findings. Weishaupt and colleagues reported finding 13 instances of nerve root deviation in the seated extension position compared with 10 instances in the supine position in a group of 30 patients with chronic low back pain. (3) They also reported that positional pain score differences were related to foraminal size. Vitaz reported changes in spinal cord compression, angulation, and alignment that occurred during physiologic movement in 20 patients with cervical spine disorders.(4) They reported excellent or good image quality in 90% of cases. Jinkins concluded that supine MRI underestimated the presence and degree of gravity-dependent spinal pathology and missed pathology of a dynamic nature.(5) Karadimas and colleagues reported the ability to demonstrate changes in healthy and degenerative discs in the weight-bearing position in 30 patients with chronic low back pain using the upright MRI.(6) Other studies have discussed the potential benefits of upright MRI or indicate it’s technical feasibility.(7-12) However, no studies were found that described clinical outcomes of patients whose treatments were selected on the new findings of positional MRI. In addition, the incremental benefit of this imaging in clinical practice is not yet known.
While this imaging approach is interesting, published results are in an early phase. Additional study is needed to first determine the characteristics of patients who might benefit from positional MR studies. The clinical benefit of basing treatment decisions, including surgery, on these additional findings needs to be established. Studies are also needed to determine if this technique might replace current diagnostic tests, such as myelography. Given this novel approach, randomized trials may be needed to adequately evaluate this technique.
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