Spin-lock (T1RHO) magnetic resonance imaging may be more effective than other imaging technologies as a quantitative measure of early intervertebral disc degeneration, according to preliminary findings presented at the annual meeting of the Orthopedic Research Society in Chicago.¹

A relatively new type of imaging technology, Spin-lock MRI uses low amplitude spin-lock radiofrequency pulses to generate a novel image contrast. The T1RHO parameter refers to the relaxation of magnetization under the influence of spin-locking. T1RHO can be measured noninvasively to generate quantitative information about low-frequency physico-chemical interactions between bulk water and surrounding molecules in biological tissues. T1RHO is highly sensitive to changes in macromolecular content, which may allow it to be used as a magnetic resonance marker of molecular changes in cartilage degeneration. The Spin-lock T1RHO MRI has been used in the brain and articular cartilage, and due to similarities between cartilage and disc, researchers sought to investigate its use in degenerative disc disease.

The new research comprises two studies: one on seven fresh-frozen cadaeveric spines including 19 discs and another of 10 asymptomatic volunteers aged 40 to 60. In the cadaver study, the discs were dissected and the nucleus pulposus removed and analyzed by spin-lock MRI. The spin-lock showed good results in terms of biochemistry and mechanics, according to lead researcher Wade Johannessen, a graduate student in bioengineering at the University of Pennsylvania in Philadelphia. In the in vivo arm of the study, spin-lock MRI also performed well as a quantitative measure of disc degeneration in terms of function and composition.

"Conventional MRI is useful for [measuring] late stages of degeneration, but it is limited in that it is not sensitive to early degenerative changes," explains Johannessen, adding that "newly emerging strategies seek to target the earliest stages of degeneration to restore disc function, and [new] technologies to diagnose early degeneration are needed."

Other advantages include ease of clinical implication, Mr. Johannessen points out. "There is no hardware modification needed, no contrast agent is used, and scans are relatively short, requiring approximately 35 minutes to complete." In addition, spin-lock T1RHO results are not susceptible to observer bias, he says. "In the future, we plan to expand to a larger study that correlates the images to clinical symptoms."

Questions still remain

Jung Yoo, MD, an orthopaedic surgeon at Oregon Health and Science University in Portland, Oregon, says he would like to see the spin-lock T1RHO compared to results from T2 weighted MRIs, another new imaging technology. "It may be better if we look at biomechanical changes and proteoglycan content, but that's not the whole picture," Dr. Yoo tells CIAOMed.

Leon Nesti, MD, PhD, assistant professor of surgery at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, and a resident in the department of orthopaedics and rehabilitation at the Walter Reed Army Medical Center in Washington, DC, agrees. "[Spin-lock T1RHO] is billed to be a more sensitive measure of changes in the water content and [has improved] spatial accuracy, but it doesn't let us know what specifically is going awry," he says. Still, "it's a nice adjunct to the current imaging modalities, but it doesn't get at the true biochemical cause of disc degeneration."

Reference

1. Johannssen W, Auerbach JD, Wheaton AJ, et al. Spin-Lock (T1RHO) MRI as a quantitative measure of intervertebral disc degeneration. Presented at: 52nd Annual Meeting of the Orthopaedic Research Society; March 18–22, 2006; Chicago, Ill. Abstract 16.