Sheldrick Kyle, Chamoli Uphar, Masuda Koichi, Miyazaki Shingo, Kato Kenji, Diwan Ashish D
Spine Service, Department of Orthopaedic Surgery, St. George & Sutherland Clinical School University of New South Wales Sydney New South Wales Australia.
School of Biomedical Engineering, Faculty of Engineering & Information Technology University of Technology Sydney Sydney New South Wales Australia.
JOR Spine. 2019 Aug 1;2(3):e1060. doi: 10.1002/jsp2.1060. eCollection 2019 Sep.
Estimation of intervertebral disc degeneration on magnetic resonance imaging (MRI) is challenging. Qualitative schemes used in clinical practice correlate poorly with pain and quantitative techniques have not entered widespread clinical use.
As part of a prior study, 25 New Zealand white rabbits underwent annular puncture to induce disc degeneration in 50 noncontiguous lumbar discs. At 16 weeks, the animals underwent multi-echo T2 MRI scanning and were euthanized. The discs were stained and examined histologically. Quantitative T2 relaxation maps were prepared using the nonlinear least squares method. Decay Variance maps were created using a novel technique of aggregating the deviation in the intensity of each echo signal from the expected intensity based on the previous rate of decay.
Decay Variance maps showed a clear and well demarcated nucleus pulposus with a consistent rate of decay (low Decay Variance) in healthy discs that showed progressively more variable decay (higher Decay Variance) with increasing degeneration. Decay Variance maps required significantly less time to generate (1.0 ± 0.0 second) compared with traditional T2 relaxometry maps (5 (±0.9) to 1788.9 (±116) seconds). Histology scores correlated strongly with Decay Variance scores (r = 0.82, < .01) and weakly with T2 signal intensity (r = 0.32, < .01) and quantitative T2 relaxometry (r = 0.39, < .01). Decay Variance had superior sensitivity and specificity for the detection of degenerate discs when compared to T2 signal intensity or Quantitative T2 mapping.
Our results show that using a multi-echo T2 MRI sequence, Decay Variance can quantitatively assess disc degeneration more accurately and with less image-processing time than quantitative T2 relaxometry in a rabbit disc puncture model. The technique is a viable candidate for quantitative assessment of disc degeneration on MRI scans. Further validation on human subjects is needed.
在磁共振成像（MRI）上评估椎间盘退变具有挑战性。临床实践中使用的定性方案与疼痛的相关性较差，而定量技术尚未广泛应用于临床。
作为先前一项研究的一部分，对25只新西兰白兔的50个非连续腰椎间盘进行环状穿刺以诱导椎间盘退变。在16周时，对这些动物进行多回波T2 MRI扫描，然后实施安乐死。对椎间盘进行染色并进行组织学检查。使用非线性最小二乘法制备定量T2弛豫图。衰减方差图是使用一种新技术创建的，该技术基于先前的衰减率汇总每个回波信号强度与预期强度的偏差。
衰减方差图显示，在健康椎间盘中，髓核清晰且界限分明，衰减率一致（低衰减方差），随着退变加剧，衰减逐渐变得更具变异性（更高的衰减方差）。与传统的T2弛豫测量图（5（±0.9）至1788.9（±116）秒）相比，衰减方差图生成所需的时间明显更少（1.0±0.0秒）。组织学评分与衰减方差评分密切相关（r = 0.82，P <.01），与T2信号强度弱相关（r = 0.32，P <.01），与定量T2弛豫测量弱相关（r = 0.39，P <.01）。与T2信号强度或定量T2映射相比，衰减方差在检测退变椎间盘方面具有更高 的敏感性和特异性。
我们的结果表明，在兔椎间盘穿刺模型中，使用多回波T2 MRI序列，与定量T2弛豫测量相比，衰减方差可以更准确地定量评估椎间盘退变，且图像处理时间更短。该技术是MRI扫描中定量评估椎间盘退变的一个可行候选方法。需要在人体受试者上进行进一步验证。
