Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
Department of Radiology, Stanford University, Stanford, CA, USA.
J R Soc Interface. 2022 Aug;19(193):20220403. doi: 10.1098/rsif.2022.0403. Epub 2022 Aug 3.
The inability to detect early degenerative changes to the articular cartilage surface that commonly precede bulk osteoarthritic degradation is an obstacle to early disease detection for research or clinical diagnosis. Leveraging a known artefact that blurs tissue boundaries in clinical arthrograms, contrast agent (CA) diffusivity can be derived from computed tomography arthrography (CTa) scans. We combined experimental and computational approaches to study protocol variations that may alter the CTa-derived apparent diffusivity. In experimental studies on bovine cartilage explants, we examined how CA dilution and transport direction (absorption versus desorption) influence the apparent diffusivity of untreated and enzymatically digested cartilage. Using multiphysics simulations, we examined mechanisms underlying experimental observations and the effects of image resolution, scan interval and early scan termination. The apparent diffusivity during absorption decreased with increasing CA concentration by an amount similar to the increase induced by tissue digestion. Models indicated that osmotically-induced fluid efflux strongly contributed to the concentration effect. Simulated changes to spatial resolution, scan spacing and total scan time all influenced the apparent diffusivity, indicating the importance of consistent protocols. With careful control of imaging protocols and interpretations guided by transport models, CTa-derived diffusivity offers promise as a biomarker for early degenerative changes.
无法检测到关节软骨表面的早期退行性变化，而这些变化通常是骨关节炎退化的前兆，这是研究或临床诊断中早期疾病检测的一个障碍。利用临床关节造影术中已知的模糊组织边界的伪影，可以从计算机断层扫描关节造影术 (CTa) 扫描中得出对比剂 (CA) 的扩散系数。我们结合了实验和计算方法来研究可能改变 CTa 衍生表观扩散系数的实验方案变化。在对牛软骨外植体的实验研究中，我们研究了 CA 稀释和运输方向（吸收与解吸）如何影响未经处理和酶消化的软骨的表观扩散系数。使用多物理场模拟，我们研究了实验观察结果的机制以及图像分辨率、扫描间隔和早期扫描终止的影响。吸收过程中的表观扩散系数随着 CA 浓度的增加而降低，其降低量与组织消化引起的增加量相似。模型表明，渗透压引起的流体流出对浓度效应有很大贡献。模拟对空间分辨率、扫描间距和总扫描时间的改变都影响了表观扩散系数，表明了一致方案的重要性。通过对成像方案的精心控制和运输模型的指导解释，CTa 衍生的扩散系数有望成为早期退行性变化的生物标志物。
