Weight-bearing MRI of the Lumbar Spine: Technical Aspects

Abstract

Magnetic resonance imaging (MRI) has an established role in the assessment of degenerative musculoskeletal conditions. However, conventional supine MRI findings often correlate poorly with clinical findings. Some patients experience accentuated back pain in the weight-bearing position. Therefore, supine MRI may underestimate the severity of degenerative spine findings. To try and improve the clinical validity of spine imaging, axial loading devices have been used with conventional supine MR imaging to simulate loading of the upright spine. More recently, upright weight-bearing MRI systems (0.25–0.6 T) were introduced, allowing images to be obtained in the standing or seated weight-bearing position and even during upright flexion or extension, rotation, or bending. Some scanners even enable capturing of real-time spinal movement. This review addresses the technical aspects and potential challenges of weight-bearing MRI, both in clinical practice and research.

In vivo 3D tomography of the lumbar spine using a twin robotic X-ray system: quantitative and qualitative evaluation of the lumbar neural foramina in supine and upright position

“…But, intrathecal contrast administration is an invasive technique requiring specific indications and would most likely not be needed if upright MR imaging examination was broadly available. If indicated this intrathecal contrast administration might be of advantage in patients struggling to maintain the upright position, e.g., due to orthostatic syncope [10], to hold still for the length of MR examinations as image acquisition with 3D tomography with a duration of 40 s is comparatively short.…”

“…The duration of weight-bearing examinations performed with this unit is significantly shorter compared with MR in the supine and upright position, the latter usually has a longer scan time of each sequence, due to the low-field MR system which is mostly used for the upright, weight-bearing position [10]. One benefit of a 3D tomography is the short scan time, which may be more easily endured by patients with back pain or radiculopathy.…”

“…This discrepancy is a challenge for diagnosis and therapy, especially if clinical symptoms and imaging findings differ. Studies have shown that the size of the lumbar foramina decreases and stenosis increases with weight-bearing [6][7][8][9][10][11][12][13][14]. However, these studies were performed either in a seated position [8,13,[15][16][17][18] or in simulated weight-bearing in supine position by applying axial loading of 40-50% of the body weight with a compressive device-the so-called axial loaded supine MR technique [2,[19][20][21].…”

Weight-Bearing Magnetic Resonance Imaging as a Diagnostic Tool That Generates Biomechanical Changes in Spine Anatomy

“…However, weightbearing MRI (WBMRI) is a relatively novel scanning technique that has the potential to replicate the dynamic components of lumbar spine degeneration, such as gravitational changes in lumbar degenerative morphology and segmental intervertebral instability. It has been shown to exaggerate particular degenerative disk morphologies (disc height, protrusion-herniation, and spinal stenosis) and, in some cases, identify pathologies not seen on conventional supine imaging [11][12][13]. This can be explained, in part, by the laws of fluid dynamics, which states that fluids are not compressible.…”

“…Compression of the semifluid discs leads to protrusion from the narrowed disc space and possible impingement of surrounding structures [11]. Furthermore, the significant increase in the lordosis lumbar angle within the upright position allows for the detection of position-dependent symptoms of spinal canal stenosis [12][13].…”