| ObjectiveTo value the feasibility of MR T2star mapping of lumbar facet joints and intervertebral discs,and evaluate the diagnostic value of T2star mapping in early-stage degeneration of lumbar facet joints and intervertebral discs.Materials and Methods22patients (12male,10female; age range,20-50years; average age,31.5±10.3years) with low back pain; exclusion criteria:neurological deficits of the lower limb, previous spine surgery, intervertebral disc herniations, a body mass index>30, rheumatoid arthritis and other known joint diseases, and contraindications for MRI.)and20age-and sex-matched volunteers (10male,10female; age range,23-45years; average age,27.4±6.8years)were examined. Sagittal and axial fast spin echo T2WI and axial T2star mapping of lumber facet joints and intervertebral discs were evaluated with a3.0T MR imaging spectrometer in42subjects.The Weishaupt grading was used for L2-S1facet joints and the Pfirrmann score was used for morphological disc grading.T2star value in the facet joints and the intervertebral discs (nucleus pulposus, anterior and posterior annulus fibrosus) were measured respectively in T2star mapping imaging, and analyze the correlation of them and variance in different grading groups.ResultsTotally304facet joints and168discs were measured:①The average T2star relaxation time of facet joints was18.7±5.4ms, and18.9、18.5and17.2ms of Weishaupt grade0、Ⅰ、Ⅱ respectively. There was no significant difference in mean T2star values between facet joints in different Weishaupt grading groups (x2=5.683, P>0.05).②The average T2star relaxation time of the nueleus pulposus of iniervertebral disc was41.2±20.1ms, and47、45.5、42.7and46.6ms of Pfirrmann scores Ⅰ、Ⅱ、Ⅲ and Ⅳ respectively. There was difference in mean T2star values between nueleus pulposus in different Pfirrmann scores (x2=582.581, P<0.05), but no significant difference in mean T2star values between anterior annulus in different Pfirrmann scores (P>0.05), neither did the posterior annulus.③Facet joint T2star values showed a weak correlation with T2values of the posterior annulus (r-0.3874; p=0.014). Facet joint T2star values showed no correlation with T2values of the nueleus pulposus or anterior annulus (r-0.1874, p-0.204; r-0.0141, p-0.055)④The results showed similar facet joint T2star values in patients and healthy volunteers, and the average T2star relaxation time were18.7±5.5ms、18.9±5.1ms.The difference had no statistical significance (p>0.05).⑤The inter-rater agreement was excellent for the facet joint T2star evaluation (r=0.835, p<0.05), and fair for the morphological Weishaupt grading (kappa=0.327).The scoring was concordant in161facet joints (53%), but disagreed by one grade in135(44.4%) and by two grades in8facet joints (2.6%).⑥The results showed similar facet joint T2star values in segments with normal (Pfirrmann scores Ⅰ、Ⅱ) and abnormal Pfirrmann scores (Pfirrmann scores Ⅲ、 Ⅳ), and the average T2star relaxation time were (20.67±5.4) ms、(16..8±6.2) ms, and the difference had no statistical significance (p>0.05).Conclusion①The excellent inter-rater agreement for T2star evaluation of the facet joint means that T2star mapping can be objective,and demonstrates that T2star measurement is a quantitative tool for researching the articular cartilage based on T2star mapping.②The T2star values can be objectively reflect the feature of the degeneration pertaining to the nueleus pulposus of iniervertebral disc.T2star mapping imaging can indicate component abnormality in early articular cartilage injury without morphology change.③This study demonstrates the feasibility of a combined axial T2star mapping approach for the facet joints and intervertebral discs. |
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