Barrett Hilary E, Mulvihill John J, Cunnane Eoghan M, Walsh Michael T
Biomed Eng Online. 2015;14 Suppl 1(Suppl 1):S5. doi: 10.1186/1475-925X-14-S1-S5. Epub 2015 Jan 9.
Calcification is a marked pathological component in carotid artery plaque. Studies have suggested that calcification may induce regions of high stress concentrations therefore increasing the potential for rupture. However, the mechanical behaviour of the plaque under the influence of calcification is not fully understood. A method of accurately characterising the calcification coupled with the associated mechanical plaque properties is needed to better understand the impact of calcification on the mechanical behaviour of the plaque during minimally invasive treatments. This study proposes a comparison of biochemical and structural characterisation methods of the calcification in carotid plaque specimens to identify plaque mechanical behaviour. Biochemical analysis, by Fourier Transform Infrared (FTIR) spectroscopy, was used to identify the key components, including calcification, in each plaque sample. However, FTIR has a finite penetration depth which may limit the accuracy of the calcification measurement. Therefore, this FTIR analysis was coupled with the identification of the calcification inclusions located internally in the plaque specimen using micro x-ray computed tomography (μX-CT) which measures the calcification volume fraction (CVF) to total tissue content. The tissue characterisation processes were then applied to the mechanical material plaque properties acquired from experimental circumferential loading of human carotid plaque specimen for comparison of the methods. FTIR characterised the degree of plaque progression by identifying the functional groups associated with lipid, collagen and calcification in each specimen. This identified a negative relationship between stiffness and 'lipid to collagen' and 'calcification to collagen' ratios. However, μX-CT results suggest that CVF measurements relate to overall mechanical stiffness, while peak circumferential strength values may be dependent on specific calcification geometries. This study demonstrates the need to fully characterise the calcification structure of the plaque tissue and that a combination of FTIR and μX-CT provides the necessary information to fully understand the mechanical behaviour of the plaque tissue.
钙化是颈动脉斑块中显著的病理成分。研究表明，钙化可能会诱发高应力集中区域，从而增加斑块破裂的可能性。然而，钙化影响下斑块的力学行为尚未完全明确。为了更好地理解在微创治疗期间钙化对斑块力学行为的影响，需要一种能够准确表征钙化以及相关斑块力学特性的方法。本研究对颈动脉斑块标本中钙化的生化和结构表征方法进行比较，以确定斑块的力学行为。通过傅里叶变换红外光谱（FTIR）进行生化分析，用于识别每个斑块样本中的关键成分，包括钙化。然而，FTIR的穿透深度有限，这可能会限制钙化测量的准确性。因此，将这种FTIR分析与使用微X射线计算机断层扫描（μX-CT）识别斑块标本内部的钙化内含物相结合，μX-CT可测量钙化体积分数（CVF）与总组织含量的关系。然后将组织表征过程应用于从人体颈动脉斑块标本的实验性周向加载中获取的斑块力学材料特性，以比较这些方法。FTIR通过识别每个标本中与脂质、胶原蛋白和钙化相关的官能团来表征斑块进展程度。这确定了硬度与“脂质与胶原蛋白”以及“钙化与胶原蛋白”比率之间呈负相关。然而，μX-CT结果表明，CVF测量与整体力学硬度相关，而峰值周向强度值可能取决于特定的钙化几何形状。本研究表明有必要全面表征斑块组织的钙化结构，并且FTIR和μX-CT的结合提供了充分理解斑块组织力学行为所需的信息。
