MRI histogram analysis enables objective and continuous classification of intervertebral disc degeneration

Abstract

Purpose Magnetic resonance imaging (MRI) is the best diagnostic imaging method for low back pain. However, the technique is currently not utilized in its full capacity, often failing to depict painful intervertebral discs (IVDs), potentially due to the rough degeneration classification system used clinically today. MR image histograms, which reflect the IVD heterogeneity, may offer sensitive imaging biomarkers for IVD degeneration classification. This study investigates the feasibility of using histogram analysis as means of objective and continuous grading of IVD degeneration. Methods Forty-nine IVDs in ten low back pain patients (six males, 25-69 years) were examined with MRI (T2-weighted images and T2-maps). Each IVD was semi-automatically segmented on three mid-sagittal slices. Histogram features of the IVD were extracted from the defined regions of interest and correlated to Pfirrmann grade. Results Both T2-weighted images and T2-maps displayed similar histogram features. Histograms of well-hydrated IVDs displayed two separate peaks, representing annulus fibrosus and nucleus pulposus. Degenerated IVDs displayed decreased peak separation, where the separation was shown to correlate strongly with Pfirrmann grade (P \ 0.05). In addition, some degenerated IVDs within the same Pfirrmann grade displayed diametrically different histogram appearances. Conclusions Histogram features correlated well with IVD degeneration, suggesting that IVD histogram analysis is a suitable tool for objective and continuous IVD degeneration classification. As histogram analysis revealed IVD heterogeneity, it may be a clinical tool for characterization of regional IVD degeneration effects. To elucidate the usefulness of histogram analysis in patient management, IVD histogram features between asymptomatic and symptomatic individuals needs to be compared.

Early changes in the extracellular matrix of the degenerating intervertebral disc, assessed by Fourier transform infrared imaging

“…Future experiments with polarized light to determine the local orientation of the fibers, combined with immunohistochemical staining of multiple collagen types, may determine the contributions of the different processes. Recently, two studies were published that investigated the relation between degeneration and the heterogeneity of MRI signals in the intervertebral disc 24,25 , both indicating that the disorder of the ECM of the intervertebral disc is a relevant measure for disc degeneration. Furthermore, the intensity of the T2 signal on MRI, commonly used to determine disc degeneration, is dependent on the integrity and orientation of collagen fibers 26,27 .…”

Differences in IVD characteristics between low back pain patients and controls associated with HIZ as revealed with quantitative MRI

“…The distribution of the mean T2-map value and SD in the sub-regions was plotted to show the regional behavior in the cohorts. Moreover, the distribution of IVD T2-map values was evaluated using the histogram analysis method proposed by Waldenberg et al [9]. The method uses a two-component Gaussian probability distribution model to separate the full range of IVD T2-map values into two sections.…”

“…In the last decade, various quantitative MRI methods have been developed that provide new objective and continuous IVD measures [9–11]. However, no specific pain marker for LBP has yet been found [12], probably due to the inclusion of overlapping phenotypes in the study cohorts and the use of gross quantitative IVD measures in the analysis.…”

“…texture and histogram analysis. For example, Waldenberg et al recently demonstrated the feasibility of histogram analysis in LBP-patients and showed a large spread in heterogeneity metrics for IVDs with similar degeneration grade [9]. Hence, comparison of such detailed quantitative metrics between symptomatic and asymptomatic individuals could potentially be of value in the diagnosis of LBP.…”

Characterization of Intervertebral Disc Changes in Asymptomatic Individuals with Distinct Physical Activity Histories Using Three Different Quantitative MRI Techniques

“…[ 5 ]. Additionally, advanced analysis software has enabled the automated quantification of the IVD degeneration, as well as the detailed characterization of different degeneration patterns [ 6 ]. However, comparisons of the usefulness of quantitative MRI have received little attention.…”