By Diagnosticsd & Imaging Week

Dynamic MRI is preferred over static MRI for detecting lumbar spondylolistheses – the slippage of vertebrae in the spine – and for establishing the full extent of vertebral instability, according to new research from the University of California, Los Angeles (UCLA) School of Medicine.

In the UCLA study, the authors reported the impact of flexion and extension on spinal canal stenosis. The authors said their study of the stenotic lumbar spinal canal is the first study reported that has been able to measure the changes in size that the stenotic canal undergoes when subjected to flexion and extension. They concluded that the dynamic MRI "can show with high precision the amount of change of the diameter of the spinal canal that occurs with flexion and extension."

The research was a pleasant surprise to MRI manufacturer Fonar (Melville, New York), according to Dan Culver, director of communications for the company.

"It's a tremendous study that came our way. We didn't even realize they were working on it and then they published the results," Culver told Diagnostics & Imaging Week. "We've been saying for a very long time that position matters [and] that weight-bearing matters."

The study compared dynamic upright MRI with static upright MRI, revealing an average miss rate of static MRI of 18.1%.

In the study, UCLA scientists defined the static position as the upright neutral sitting position and the dynamic positions as the flexion and extension sitting positions. The study is the first to quantify the "miss" rate of static MRI, Fonar noted.

UCLA researchers presented four scientific papers during the October annual meeting of the North American Spine Society (NASS; Burr Ridge, Illinois) in Austin, Texas comparing the visualization of spine pathology by dynamic MRI to images obtained by static MRI.

The studies also were published in the September/October issue of The Spine Journal.

According to Fonar, the studies were performed using its Upright Multi-Position MRI scanner in conjunction with the software image analysis program developed by True MRI (Anaheim, California) that provides comprehensive quantitative measurements of spinal structures in static and dynamic positions.

Fonar says its Upright MRI is the only upright weight-bearing flexion-extension MRI. It is a multi-position, dynamic MRI scanner, the company said.

"UCLA's results from a very large patient database of 1,302 patients establish beyond question that MRI miss rates of important pathology by static MRI technology are substantial and not inconsequential," said Raymond Damadian, MD, president of Fonar. "Even imaging voxels cubic micron in size, should they ever exist, would be of no value if they could not visualize the patient's problem."

For example, Damadian said, "If the surgeon cannot see the problem because static-only MRI misses it and does not visualize it, he cannot fix it. Worse yet, there is the ever-present risk that he may do the wrong surgery if he is unable to see the anatomy that causes the problem."

He said the static recumbent-only MRI is "clearly falling short of the accuracy depicting spinal structures that is needed for the surgeon to achieve top results."

The spondylolisthesis miss rates for the upright patient with back pain are likely to represent an underestimate of the number of spondylolistheses missed, the company noted. Fonar said the UCLA study only compared the upright patient in the flexion, extension and neutral sit positions and did not take into account the "misses" from static MRIs obtained with the patient lying down in the traditional non-weight-bearing position of the conventional recumbent MRI.

Fonar said the importance of paying attention to comparisons with recumbent scanning are underscored by a separate study of 58 patients performed at the University of Aberdeen (Aberdeen, Scotland) using its Dynamic Upright MRI scanner. Images of upright patients were compared to images of the same patients lying down. According to the University of Aberdeen authors, "The ability to image the spine in different postures adds significantly to the diagnostic accuracy of the MRI examination. For more than 50% of the patients examined in our study, a better understanding of the condition of the spine was obtained."

Culver said Fonar believes about half of all MRIs done are of the spine.

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