Lumbar Spine Anatomy in Supine versus Weight- Bearing Magnetic Resonance Imaging: Detecting Significant Positional Changes and Testing Reliability of Quantification

STUDY DESIGN

Testing between and within group differences and assessing reliability of measurements.

PURPOSE

To study and compare lumbar spine morphology in supine and weight-bearing (WB) magnetic resonance imaging (MRI).

OVERVIEW OF LITERATURE

Upright lumbar MRI may uncover anatomical changes that may escape detection when using conventional supine imaging. This study quantified anatomical dimensions of the lumbar spine in the supine and WB MRI, compared specific morphometric differences between them, and tested the intra-rater reliability of the measurements. Repeated measures analysis was used to compare within- and between-session measurements performed on the supine and WB images. Reliability and agreement were assessed by calculating intraclass correlation (ICC) coefficient.

METHODS

Data from 12 adults without any history of back pain were used in this study. Sagittal T2-weighted images of the lumbar spine were acquired in the supine and WB positions twice (in two separate sessions scheduled within a week). Linear, angular dimensions, and cross-sectional areas (CSAs) were measured using proprietary software. Supine and WB data acquired from the two imaging sessions were tested for intra-rater reliability. Quantified data were normalized for each session to test the significance of differences. ICC was calculated to test the reliability of the measurements.

RESULTS

Linear, angular, and CSA measurements demonstrated strong within-position (supine and WB) correlations (r -values, 0.75-0.97). Between-position (supine vs. WB) differences were significant for all measured dimensions (p<0.05). Between-session measurements demonstrated a strong correlation (r -values, 0.64-0.83). Calculated ICC showed strong agreement among the measurements.

CONCLUSIONS

Anatomical dimensions of the lumbar spine may demonstrate consistent and significant differences between supine and WB MRI for specific structural parameters.

Upright, Weight-Bearing, Dynamic-Kinetic MRI of the Spine pMRI/kMRI

The purpose of this study was to demonstrate the general utility of the first dedicated magnetic resonance imaging (MRI) unit enabling upright, weight-bearing positional evaluation of the spinal column ( pMRI) during various dynamic- kinetic maneuvers ( kMRI) in patients with degenerative conditions of the spine.

This study consisted of a prospective analysis of cervical and lumbar imaging examinations. All studies were performed on a recently introduced whole body MRI system (Stand-Up™ MRI, Fonar Corp, Melville, NY). The system operates at 0.6T using an electromagnet with a horizontal field, transverse to the longitudinal axis of the patient's body. Depending upon spinal level, all examinations were acquired with either a cervical or lumbar solenoidal radiofrequency receiver coil. This unit is configured with a top/front-open design, incorporating a patient-scanning table with tilt, translation and elevation functions. The unique motorized patient handling system developed for the scanner allows for vertical (upright, weight bearing) and horizontal (recumbent) positioning of all patients. The top/front-open construction also allows dynamic-kinetic flexion and extension maneuvers of the spine. Patterns of bony and soft tissue change occurring among recumbent ( rMRI) and upright neutral positions ( pMRI), and dynamic- kinetic acquisitions ( kMRI) were sought.

Depending on the specific underlying pathologic degenerative condition, significant alterations observed on pMRI and kMRI that were either more or less pronounced than on rMRI included: fluctuating anterior and posterior disc herniations, hypermobile spinal instability, central spinal canal and spinal neural foramen stenosis and general sagittal spinal contour changes. No patient suffered from feelings of claustrophobia that resulted in termination of the examination.

In conclusion, the potential relative beneficial aspects of upright, weight-bearing ( pMRI), dynamic-kinetic ( kMRI) spinal imaging on this system over that of recumbent MRI ( rMRI) include: the revelation of occult disease dependent on true axial loading, the unmasking of kinetic-dependent disease, and the ability to scan the patient in the position of clinically relevant signs and symptoms. This imaging unit also demonstrated low claustrophobic potential and yielded relatively high-resolution images with little motion/chemical-shift artifact.

Does evaluator experience have an impact on the diagnosis of lumbar spine instability in dynamic MRI? Interobserver agreement study

OBJECTIVES

We aimed to evaluate interobserver agreement in the definition of spine instability among spine neuroradiologists with or without experience in dynamic magnetic resonance imaging (MRI).

MATERIAL AND METHODS

Two expert neuroradiologists and two residents retrospectively evaluated the pre-operative dynamic MRI examinations of patients with vertebral instability. Segmental motion, defined as excessive (more than 3 mm) translational motion from supine to upright, was investigated in 103 subjects (309 segments) using kinetic MRI. Radiographic parameters which can help indicate segmental instability include disc degeneration, facet joint osteoarthritis, and ligament flavum hypertrophy. These three radiographic parameters were simultaneously evaluated, and the combinations corresponding to significant segmental instability at each level were determined. The agreement among the neuroradiologists was calculated using the kappa coefficient. All patients had neurosurgical intervention to stabilize the spine.

RESULTS

Agreement was high among experienced and non-experienced neuroradiologists. Agreement was nearly perfect for spinal location of spinal instability.

CONCLUSIONS

This study demonstrates that the experience of the evaluator has a low impact on the assessment of spinal instability if correct classification is used. The interobserver agreement confirms the usefulness and safety of kinetic MRI in the correct diagnosis of spinal instability even by less experienced evaluators.

Axial loaded imaging of the lumbar spine 18 years later. Is it still a valuable examination?

This paper reviews experience with 12100 Axial Loader (AL) studies of the lumbar spine both in CT and in MRI 18 years after the development of axial loaded CT and MRI. The Axial Loader device is described together with the CT and MR acquisitions. Disc, intersomatic and articular facet changes are described with a breakdown of the classification of abnormalities as elementary or complex dynamic modifications.

Intrathecal gadolinium-enhanced MR cisternography in the evaluation of clinically suspected cerebrospinal fluid rhinorrhea in humans: early experience

In this prospective multicenter study, the authors evaluated the utility of magnetic resonance (MR) cisternography after intrathecal administration of gadopentetate dimeglumine in 15 patients clinically suspected of having cerebrospinal fluid (CSF) rhinorrhea. By means of lumbar puncture, a single dose of 0.5 mL of gadopentetate dimeglumine was injected into the lumbar subarachnoid space. Thirteen patients showed leakage of contrast material through the cribriform plate into the ethmoid or sphenoid air cells. No leakage was observed in two patients. The study results show the relative safety and feasibility of low-dose gadolinium-enhanced MR cisternography in confirming the presence and determining the focus of active CSF leaks.