A study led by The University of Hong Kong (HKU)’s Department of Orthopaedics and Traumatology is said to be the first to report the Ultra-Short Time-to-Echo Disc Sign (UDS) as a new low back pain (LBP) imaging biomarker—providing insights into degenerative disc disease of the spine.

As compared with the “conventional” T2-weighted magnetic resonance imaging (MRI), which has been broadly used to diagnose LBP in the past 30 years—UDS was found to be more sensitive and reliable to identify the cause and treatment of LBP. Such findings are expected to reduce healthcare costs, resulted from inaccurate diagnosis, and improve patient outcomes.

The research has been published in the international journal Spine this month (August 2017 issue).

Conventional MRI is costly and ineffective in diagnosing LBP


According to Global Burden of Disease 2010 study, LBP causes more disability than any other conditions in the world – affecting up to 80% of the population.

The reasons behind LBP are complex and numerous. Factors may include obesity, lack of exercise or simply sitting for extended periods at work stations. Yet, studies have pointed out lumbar disc degeneration as one of the major risk factors leading to the disease.

Over the years, MRI has been considered the gold-standard among imaging options to assess soft-tissues of the human body, in particular, the intervertebral discs of the spine – to understand what may lead and cause LBP. However, the current imaging technology, the “conventional” T2-weighted MRI, is not highly sensitive and reliable in diagnosing LBP. As a result, it may not be useful to “predict” future LBP episodes secondary to disc degeneration.

Such shortcomings may provide a rationale as to why it is common to find symptomatic individuals with seemingly normal (i.e. non-degenerated) discs and asymptomatic individuals with degenerative disc changes on conventional MRI. Due to inaccurate diagnosis of LBP and identification of pain mechanisms, outcomes of LBP treatments are often tenuous and have been criticised. Ultimately, apart from unsatisfactory patient outcomes, this puts heavy burden on the healthcare costs.

Dr Dino Samartzis points out that UTE MRI can identify “hidden” degenerative disc findings in an easy, quick and reliable fashion that helps us understand the pain may indeed have its ‘origins’ within the disc. Photo credit: Li Ka Shing Faculty of Medicine, HKU
Dr Dino Samartzis points out that UTE MRI can identify “hidden” degenerative disc findings in an easy, quick and reliable fashion that helps us understand the pain may indeed have its ‘origins’ within the disc. Photo credit: Li Ka Shing Faculty of Medicine, HKU

“For the past 30 years, it has been argued time and time again that findings on conventional MRI or imaging that are commonly used worldwide are not strongly related to LBP or disability. Many clinicians and scientists have often questioned the practical use of having patients undergo such costly conventional imaging to determine the source of pain and that degenerative disc findings are commonplace among individuals, who are also not in pain. Our study provides the ‘missing link’ between imaging findings of the spine and the development of LBP and disability,” explained Dr Dino Samartzis, lead investigator of the study and Associate Professor of Department of Orthopaedics and Traumatology at HKU.

Encouraging findings promote further understanding in the pathologies and therapies for LBP


In the past decade, various novel MRI technologies have been developed in an effort to address more sensitive measures to assess spine degeneration. One such imaging technology is Ultra-Short Time-to-Echo (UTE) MRI.

UTE MRI assesses MRI signal from short T2 components that are not detected on conventional T2-weighted MRI. It can be performed on any MRI machine; and takes approximately 15 – 20 minutes to scan the lumbar spine of one individual, which is similar in time as conventional MRI sequences.

Utilising UTE MRI, the research team has identified a new disc biomarker, called the UDS, and its clinical importance.

A total of 108 Southern Chinese participants were recruited for the study. T2-weighted MRI was used to assess disc degeneration and other phenotypes, and T1-rho MRI values represented quantitative proteoglycan content (i.e. water) of the disc. UDS was detected on UTE as a hyper- or hypo-intense band across a disc. The cumulative number of UDS levels represented a UDS score; whereas summated degenerated scores of lumbar levels via T2-weighted MRI represented a cumulative disc degeneration score. Subject demographics, LBP every day (chronic) in the past year and disability profiles (Oswestry Disability Index: ODI) were obtained.

MRI of the lumbar spine of a subject with no chronic low back pain: (Left) T2-weighted MRI noting multilevel disc degeneration and Modic changes; (Right) Ultra-short time-to-echo (UTE) MRI noting no UTE disc sign (UDS). Photo credit: Li Ka Shing Faculty of Medicine, HKU
MRI of the lumbar spine of a subject with no chronic low back pain: (Left) T2-weighted MRI noting multilevel disc degeneration and Modic changes; (Right) Ultra-short time-to-echo (UTE) MRI noting no UTE disc sign (UDS). Photo credit: Li Ka Shing Faculty of Medicine, HKU

Results revealed the UDS was noted in 39.8% subjects, of which 61.4% occurred at the lower lumbar levels. Subjects with UDS had significantly more disc degeneration and levels with pathologic changes of the vertebral bodies (i.e. Modic changes). Based on disc levels, a higher prevalence of disc degeneration and disc bulges/protrusions, Modic changes and spondylolisthesis (i.e. slippage of the vertebral body) were noted in UDS discs than non-UDS discs. T1-rho values were lower in UDS discs than non-UDS discs.

MRI of the lumbar spine of a subject with chronic low back pain and disability: (Left) T2-weighted MRI noting multilevel disc degeneration and Modic changes; (Right) Ultra-short time-to-echo (UTE) MRI noting multilevel UTE disc sign (UDS), noted by white arrows. Photo credit: Li Ka Shing Faculty of Medicine, HKU
MRI of the lumbar spine of a subject with chronic low back pain and disability: (Left) T2-weighted MRI noting multilevel disc degeneration and Modic changes; (Right) Ultra-short time-to-echo (UTE) MRI noting multilevel UTE disc sign (UDS), noted by white arrows. Photo credit: Li Ka Shing Faculty of Medicine, HKU

Meanwhile, the majority of UDS could not be detected on conventional T2-weighted MRI. Additionally, the UDS score was significantly correlated with worse ODI scores and pain, whereas T2-weighted cumulative disc degeneration score was not. The study revealed 39.5% of UDS subjects who had multi-level involvement also had a higher prevalence of LBP. However, this correlation was not found on T2-weighted MRI.

Dr Henry Pang says that the study promotes further understanding in the pathologies and therapies for low back pain and lumbar degeneration. Photo credit: Li Ka Shing Faculty of Medicine, HKU
Dr Henry Pang says that the study promotes further understanding in the pathologies and therapies for low back pain and lumbar degeneration. Photo credit: Li Ka Shing Faculty of Medicine, HKU

“Among various MRI sequences, UTE MRI is the only sequence so far in our study that has shown definite correlation between back pain, disability and degenerative disc changes. At the same time, as our study group unveils the previously hidden pathologies in traditional MRI, these findings may promote further understanding in the pathologies and therapies for LBP and lumbar degeneration,” noted Dr Henry Pang, Master of Research in Medicine student, Li Ka Shing Faculty of Medicine, HKU and first author of the study.

Moving forward, study plans are underway to identify what these UDS findings truly represent and how they could contribute to the mechanism of LBP – as well as predicting future episodes of pain.

Further initiatives are also being planned to address large-scale, prospective and multicentre international studies to further validate our findings, and assess the utility of the UDS on different clinical and research platforms. MIMS

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