PURPOSE This study aimed to explore the feasibility of the fractal method used in decoding disk heterogeneity, hoping to find a reliable imaging biomarker for the quantitative and continuous grading of intervertebral disks (IVDs). METHODS Totally, 180 IVDs in 65 low back pain patients (29 males, 36 female, 28-69 years) were examined with MRI. Each IVD was manually segmented on axial slice (at the mid-height layer of the disk). All disks were visually evaluated regarding degeneration grade, using Pfirrmann classification, by two experienced radiologists. Fractal dimension (FD) of the IVD was calculated from the defined regions of interest and correlated with Pfirrmann grade. RESULTS Fractal dimension differed significantly between any two groups (P < 0.01). The mean FDs for the four grades were as follows: Pfirrmann 1: 1.13 ± 0.02; Pfirrmann 2: 1.30 ± 0.05; Pfirrmann 3: 1.50 ± 0.05; and Pfirrmann 4: 1.65 ± 0.02. The well-hydrated IVDs displayed low fractal dimension. Degenerated IVDs displayed increased fractal dimension caused by disk heterogeneity, where the fractal dimension was shown to correlate strongly with Pfirrmann grade. CONCLUSIONS Fractal dimension associated well with IVD degeneration, determined with Pfirrmann grading, suggesting that the IVD fractal analysis was a suitable detection tool for the objective and continuous classification of IVD degeneration. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

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分形维数是否是用于椎间盘定量分类的可靠成像生物标记？

目的本研究旨在探讨用分形方法解码椎间盘异质性的可行性，希望找到一种可靠的成像生物标记物，用于椎间盘（IVD）的定量和连续分级。方法对65例下腰痛患者（男性29例，女性36例，年龄28-69岁）进行180次IVD检查。将每个IVD手动分割为轴向切片（在磁盘的中间高度层）。两名经验丰富的放射科医生使用Pfirrmann分类法对所有光盘的变性等级进行了视觉评估。IVD的分形维数（FD）是根据定义的感兴趣区域计算的，并与Pfirrmann等级相关。结果分形维数在两组之间均存在显着差异（P <0.01）。四个年级的平均FD如下：Pfirrmann 1：1.13±0.02；菲尔曼2：1.30±0.05; 菲曼3：1.50±0.05; 和Pfirrmann 4：1.65±0.02。水分充分的IVD显示出较低的分形维数。退化的IVDs显示出由磁盘异质性引起的分形维数增加，其中分形维数与Pfirrmann等级密切相关。结论分形维数与IVD变性良好相关，通过Pfirrmann分级确定，这表明IVD分形分析是用于IVD变性的客观和连续分类的合适检测工具。这些幻灯片可以在电子补充材料下找到。分形维数与Pfirrmann等级密切相关。结论分形维数与IVD变性良好相关，通过Pfirrmann分级确定，表明IVD分形分析是用于IVD变性的客观和连续分类的合适检测工具。这些幻灯片可以在电子补充材料下找到。分形维数与Pfirrmann等级密切相关。结论分形维数与IVD变性良好相关，通过Pfirrmann分级确定，表明IVD分形分析是用于IVD变性的客观和连续分类的合适检测工具。这些幻灯片可以在电子补充材料下找到。