|MP 6.01.48||Positional Magnetic Resonance Imaging|
|Original Policy Date
|Last Review Status/Date
Reviewed with literature search/4:2013
|Return to Medical Policy Index|
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Positional magnetic resonance imaging (MRI) allows imaging of the patient in various positions, including sitting and standing. This technology is being evaluated for the diagnosis of patients with position-dependent back pain.
Determining the cause of back pain is a complex task. In some patients, extensive evaluation with various imaging modalities does not lead to a definitive diagnosis. Some recent studies have suggested that imaging the body in various positions with “loading” of the spine may lead to more accurate diagnosis. This loading can be accomplished by having the patient sit or stand upright. Also, imaging can be completed with the patient in the position that causes the symptom(s). This is being evaluated in suspected nerve root compression and in some cases of spondylolisthesis.
An open magnetic resonance imaging (MRI) system has been developed that allows imaging of the patient in various positions. The imaging can be conducted with partial or full weight bearing. Dynamic-kinetic imaging (images obtained during movement) can also be obtained with this system. Conventional MR imaging of the spine is typically completed with the patient in a recumbent position. Weight bearing can be simulated by imaging in the supine position with a special axial loading device.
One concern with positional MRI is the field strength of the scanners. Today’s clinical MRI scanners may operate at a field strength between 0.1 Tesla (T) to 3 T and are classified as either low-field (<0.5 T), mid-field (0.5-1.0 T), or high-field (>1.0 T). Low-field MRI is typically used in open scanners. Open scanners are designed for use during interventional or intraoperative procedures, when a conventional design is contraindicated (e.g., an obese or claustrophobic patient), or for changes in patient positioning.
In general, higher field strength results in an increase in signal-to-noise ratio, spatial resolution, contrast and speed. Thus, low-field scanners produce poorer-quality images compared to high-field scanners, and the longer acquisition times with low-field scanners increases the possibility of image degradation due to patient movement. However, field strength has less of an effect on the contrast-to-noise ratio, which determines the extent to which adjacent structures can be distinguished from one another.
FONAR Corporation has 510(k) marketing clearance from the U. S. Food and Drug Administration (FDA) for an MRI system that performs positional MRI scans (i.e., FONAR’s Upright® MRI).
Positional (nonrecumbent) magnetic resonance imaging (MRI) is considered investigational, including its use in the evaluation of patients with cervical, thoracic, or lumbosacral back pain.
BlueCard/National Account Issues
State or federal mandates (e.g., FEP) may dictate that all FDA-approved devices may not be considered investigational. FDA-approved devices may be assessed on the basis of their medical necessity.
This policy was created in 2007 and updated periodically using the MEDLINE database. The most recent update was performed through March 15, 2013.
In evaluating this approach to imaging, it is important to determine if positional magnetic resonance imaging (MRI) results in additional findings. However, it is also important to determine if treatment of these additional findings results in improved outcomes. This additional step is important given the previously described false-positive findings with MRI of the spine. For example, Jarvik and colleagues reported that many MRI 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. 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. (1)
A systematic review of emerging MRI technologies for musculoskeletal imaging under loading stress was prepared by the Tufts Medical Center Evidence-based Practice Center for the Agency for Healthcare Research and Quality (AHRQ) in 2011. (2) Included were 36 studies that used positional weight-bearing MRI in patients with musculoskeletal conditions. Also included were studies evaluating axial compression devices. Most studies were cross-sectional or had case-control designs. The most commonly imaged body region was the lumbar spine. Four studies of lumbar spine were identified that compared positional weight-bearing MRI with conventional MRI, myelography, or non-weight-bearing imaging in the same MRI device; however, these studies did not report the effect of the technology on patient outcomes. Two studies of foot imaging that compared weight-bearing MRI with MRI in the supine position with the same MRI device found that the 2 techniques provided similar information. Two studies of imaging the knee joint found differences between weight-bearing MRI and non-weight-bearing MRI using the same device; no functional outcomes were reported. The potential effect on image quality of low magnetic field strengths (<0.6 Tesla) in weight-bearing MRI scanners was not assessed. The systematic review concluded that despite the large number of available studies, considerable uncertainty remains about the utility of this technique for the clinical management of musculoskeletal conditions. Examples of primary studies and key studies published after the systematic review are described below.
Comparison of Positional MRI in Neutral, Flexion, and Extension
One of the studies included in the systematic review was a 2008 quantitative comparison of positional MRI in neutral, flexion, and extension positions by Zou et al. (3) The study included 553 patients (mean age, 46 years; range: 18–76 years) with symptomatic back pain with/without radiculopathy who were referred for kinetic/positional MRI (0.6 Tesla). The disc bulge on MRI in the 3 positions (neutral, flexion, and extension) was quantified by MRI analysis software, and the bulge size was compared independently by 2 spine surgeons who were unaware of the patient’s history and clinical findings. Increased disc bulge at extension and flexion, in comparison with neutral, was seen in 16% and 12% of discs, respectively. Diagnosis of grade 2 disc bulge that had been categorized as grade 1 in neutral position (i.e., missed diagnosis) was 19.5% for extension and 15.3% for flexion MRI. Vitaz et al. 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.
Comparison Between Seated and Supine MRI
Another study included in the systematic review was by Weishaupt and colleagues, who reported finding 13 instances of nerve root deviation in the seated extension position in a 0.5 Tesla positional MRI compared with 10 instances in the supine position in a 1.0 Tesla conventional MRI in a group of 30 patients with chronic low back pain. (5) Diagnoses in the supine position changed in 4 disks (5%) in seated flexion and in 7 disks (9%) in seated extension. They also reported that positional pain score differences were related to foraminal size.
Ferreiro Perez et al. compared recumbent and upright-sitting positions in 89 patients with disc herniation or spondylolisthesis (cervical or lumbar spine) in 2007. (6) Using a 0.6 Tesla Upright MRI system for both positions, pathology (disc herniation or spondylolisthesis) was identified in 68 patients (76%). Images from 18 patients (20%) were not interpretable due to motion artifact. Pathologic features were better identified (i.e., either only evident or seen to be enlarged) in 52 of the 68 patients (76%) when in the sitting position; 10 of these were only observed in the sitting position. Pathologic features were better identified in the recumbent position in 11 of the 68 patients (16%). The overall underestimation rate was calculated to be 62% for patients in the recumbent position and 16% for those in the upright-seated position. This research suggests that there may be advantages when the position during imaging is matched with the positional symptoms of the patient. However, a more appropriate comparison group would be a standard recumbent clinical MRI system (e.g., field strength >0.6 T). In addition, technical problems with motion artifact were due to poor stabilization in an upright-sitting position.
Comparison Between Standing and Supine MRI
In a 2013 study by Tarantino, 57 patients with low back pain when standing (50% also had back pain in the supine position) received an MRI in both upright and recumbent positions using a 0.25 T tilting system. (7) A table tilt of 82 degrees was used to reproduce the orthostatic position without the patient instability associated with standing at 90 degrees. In comparison with the supine position, there was a significant decrease in intervertebral disc thickness (11.2 mm vs. 12.9 mm) along changes in other measures and a qualitative increase in the volume of disc protrusions and/or spondylolisthesis in the upright position.
Comparison Between Standing and Axial Loaded Supine MRI
A 2008 study compared vertical (standing) MRI and recumbent MRI with axial loading in patients with lumbar spinal stenosis. (8) Sixteen patients with neurogenic claudication, experienced mainly during walking or in an erect position, were recruited for this phase of the study. Each patient underwent 4 scans with a 0.6 Tesla Upright MRI system, consisting of vertical, horizontal with compression at a load of 40% of body weight, horizontal with no load, and finally horizontal with a 50% axial load. All horizontal scans were conducted with a cushion placed below the lower back to induce extension of the lumbar spine. Results showed similar dural sac cross-sectional area (DCSA) between the 2 positions, suggesting that the standing position may be adequately simulated while recumbent by axial loading and lordosis. Results were not correlated with patient symptoms in this study.
Comparison Between Upright Positional MRI and Standing Radiographs
In 2013, Diefenbach et al. assessed whether upright positional MRI could be a radiation-free method of monitoring spinal curvature in adolescent idiopathic scoliosis. (9) Twenty-five patients received anterior-posterior and lateral plain radiographs and an upright MRI, which was performed at the manufacturer’s facility. Three MRI scans were repeated due to patient movement. Assessment by 2 independent observers resulted in correlations of r=0.901 between x-ray and MRI for the Cobb angle and r=0.943 for kyphosis. Inter-rater reliability was high for both radiographs and upright MRI.
Conclusions: The literature shows a number of studies reporting that positional MRI can identify abnormalities in patients in whom conventional (supine) MRI did not identify significant abnormal findings. However, the clinical significance of these findings and the effect on patient outcomes is uncertain.
Clinical Input Received through Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.
In response to the request for input through Physician Specialty Societies and Academic Medical Centers, information was received from the American College of Radiology and 1 academic medical center while the policy was under review in 2008. Both reviews agreed that positional MRI is considered investigational.
No studies were found that described clinical outcomes of patients whose treatments were selected on the new findings of positional magnetic resonance imaging (MRI), and the incremental benefit of this imaging in clinical practice is not yet known. The clinical benefit of basing treatment decisions, including surgery, on these additional findings needs to be established. Studies that correlate the positional MRI findings with patient symptoms and outcomes of treatment are also needed. Another concern that needs further study is that positional scans, which use lower strength magnets, may be of lesser quality than those from traditional supine MRI. The scientific evidence at this time does not permit conclusions concerning the effect of this technology on health outcomes. Therefore, the use of positional MRI is considered investigational.
Practice Guidelines and Position Statements
A 2007 health technology assessment from the Washington State Health Care Authority determined that there was insufficient evidence to make any conclusions about upright MRI’s effectiveness, including whether upright MRI: accurately identifies an appropriate diagnosis; can safely and effectively replace other tests; or results in equivalent or better diagnostic or therapeutic outcomes. (10) Evidence considered the most compelling for this decision included:
- Technology is 10-years old, but no accuracy studies and very few reliability studies
- Of the studies available, most were poor quality and sample sizes were very small
- Image quality is lower and some evidence of higher percentage of individuals not being able to complete the test due to pain from positioning
- Other tests are currently available for diagnosing same conditions, even though it was noted that those tests might also have limitations
- One study that was of higher quality raised the possibility that upright MRI might be less beneficial due to decreased findings
- There are no evidence based clinical guidelines addressing appropriate upright MRI usage.
Medicare National Coverage
No national coverage determination was identified.
- Jarvik JJ, Hollingworth W, Heagerty P et al. The Longitudinal Assessment of Imaging and Disability of the Back (LAIDBack) Study: baseline data. Spine (Phila Pa 1976) 2001; 26(10):1158-66.
- Dahabreh IJ, Hadar N, Chung M. Emerging magnetic resonance imaging technologies for musculoskeletal imaging under loading stress: scope of the literature. Ann Intern Med 2011; 155(9):616-24.
- Zou J, Yang H, Miyazaki M et al. Missed lumbar disc herniations diagnosed with kinetic magnetic resonance imaging. Spine (Phila Pa 1976) 2008; 33(5):E140-4.
- Vitaz TW, Shields CB, Raque GH et al. Dynamic weight-bearing cervical magnetic resonance imaging: technical review and preliminary results. South Med J 2004; 97(5):456-61.
- Weishaupt D, Schmid MR, Zanetti M et al. Positional MR imaging of the lumbar spine: does it demonstrate nerve root compromise not visible at conventional MR imaging? Radiology 2000; 215(1):247-53.
- Ferreiro Perez A, Garcia Isidro M, Ayerbe E et al. Evaluation of intervertebral disc herniation and hypermobile intersegmental instability in symptomatic adult patients undergoing recumbent and upright MRI of the cervical or lumbosacral spines. Eur J Radiol 2007; 62(3):444-8.
- Tarantino U, Fanucci E, Iundusi R et al. Lumbar spine MRI in upright position for diagnosing acute and chronic low back pain: statistical analysis of morphological changes. J Orthop Traumatol 2013; 14(1):15-22.
- Madsen R, Jensen TS, Pope M et al. The effect of body position and axial load on spinal canal morphology: an MRI study of central spinal stenosis. Spine (Phila Pa 1976) 2008; 33(1):61-7.
- Diefenbach C, Lonner BS, Auerbach JD et al. Is radiation-free diagnostic monitoring of Adolescent Idiopathic Scoliosis feasible using upright positional MRI? Spine (Phila Pa 1976) 2013.
- Washington State Health Care Authority. Health Technology Assessment on Upright/Positional MRI. 2007. Available online at: http://www.hta.hca.wa.gov/documents/decision_and_finding_070530_public.pdf Last accessed March 2013.
|CPT||No specific code|
|ICD-9 Diagnosis||Investigational for all diagnoses|
|ICD-10-CM (effecitve 10/1/14)||Investigational for all diagnoses|
|M45.0-M45.9||Ankylosing spondylitis code range|
|M47.01-M47.9||Spondylosis code range|
|M50.00-M50.93||Cervical disc disorders code range|
|M51.04-M51.9||Thoracic, thoracolumbar, and lumbosacral intervertebral disc disorders code range|
|M54.00-M54.9||Dorsalgia code range|
|ICD-10-PCS (effective 10/01/14)||ICD-10-PCS codes are only used for inpatient services. There is no specific ICD-10-PCS code for this imaging.
The following codes might be used.
|BR30Y0Z, BR30YZZ, BR30ZZZ, BR31Y0Z, BR31YZZ, BR31ZZZ, BR32Y0Z, BR32YZZ, BR32ZZZ, BR33Y0Z, BR33YZZ, BR33ZZZ, BR37Y0Z, BR37YZZ, BR37ZZZ, BR39Y0Z, BR39YZZ, BR39ZZZ||Imaging, axial skeleton, magnetic resonance imaging (MRI), code by body part, use of contrast and whether enhanced or not|
Magnetic Resonance Imaging, Positional
|02/15/07||Add to Radiology section||New Policy|
|04/09/08||Replace Policy||Policy updated with literature review; reference numbers 5 and 6 added; clinical input reviewed; policy statement unchanged|
|04/24/09||Replace Policy||Policy updated with literature review; reference number 7 added; policy statement unchanged|
|04/08/2010||Replace policy||Policy updated with literature review through February 2010; references 8 and 9 added; policy statement unchanged|
|4/14/11||Replace policy||Policy updated with literature review through January 2011; reference 9 added; policy statement unchanged|
|04/12/12||Replace policy||Policy updated with literature review through February 2012; Rationale section revised and references reordered; reference 2 added; some references removed; policy statement unchanged|
|04/11/13||Replace policy||Policy updated with literature review through March 15, 2013; references 7 and 9 added; policy statement unchanged|