Measuring and modeling patient-specific distributions of material properties in abdominal aortic aneurysm wall
Measuring and modeling patient-specific distributions of material properties in abdominal aortic aneurysm wall
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DOI：
10.1007/s10237-012-0436-1
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发表时间：
2013-08-01
影响因子：
3.5
通讯作者：
Gee, M. W.
中科院分区：
文献类型：
--
作者：
Reeps, C.;Maier, A.;Gee, M. W.
用于腹主动脉瘤（AAA）破裂风险分层的临床确立的直径标准和计算有限元（FE）分析的新方法均基于AAA壁的群体平均、均匀材料特性的假设。材料特性的患者间和患者内变化的存在是已知的，但迄今为止尚未得到充分解决。为了在将来能够对患者特定的AAA壁特性进行术前估计，我们研究了无创评估的临床参数与实验测量的AAA壁特性之间的关系。我们在开放手术中采集了n = 163个AAA壁标本（n = 50例患者），并记录了确切的切除部位。使用单轴拉伸试验测试试样的厚度、弹性性能和失效载荷。此外，从手术期间的记录和患者图表中获得了43个非侵入性可评估的患者特异性或患者特异性参数。将实验结果与非侵入性评估参数相关联，并创建简单的回归模型来数学地描述这些关系。血管壁厚度与PET/CT评估的切除部位的代谢活性（rho = 0.499，P = 4 x 10（-7））和实验室血液分析的血小板计数（rho = 0.445，P = 3 x 10（-9））相关性最显著。患有糖尿病的患者的壁厚度增加，而患有慢性肾病（CKD）的患者的壁厚度显著变薄。弹性AAA壁特性与切除部位（PET/CT）的代谢活性、存在的钙化以及AAA近端未扩张主动脉的直径显著相关。失效特性（壁强度和失效张力）与患者的病史和实验室血液分析结果相关。有趣的是，CKD患者的AAA壁衰竭张力显著降低，血液中钾和尿素水平分别升高，两者均与肾脏疾病相关。本研究是未来术前评估AAA壁特性的第一步。结果可以传送到直径标准和FE分析，以改进破裂风险预测。CKD患者的AAA壁失效张力降低的事实意味着该患者组的AAA破裂风险增加，AAA直径更小。
Both the clinically established diameter criterion and novel approaches of computational finite element (FE) analyses for rupture risk stratification of abdominal aortic aneurysms (AAA) are based on assumptions of population-averaged, uniform material properties for the AAA wall. The presence of inter-patient and intra-patient variations in material properties is known, but has so far not been addressed sufficiently. In order to enable the preoperative estimation of patient-specific AAA wall properties in the future, we investigated the relationship between non-invasively assessable clinical parameters and experimentally measured AAA wall properties. We harvested n = 163 AAA wall specimens (n = 50 patients) during open surgery and recorded the exact excision sites. Specimens were tested for their thickness, elastic properties, and failure loads using uniaxial tensile tests. In addition, 43 non-invasively assessable patient-specific or specimen-specific parameters were obtained from recordings made during surgery and patient charts. Experimental results were correlated with the non-invasively assessable parameters and simple regression models were created to mathematically describe the relationships. Wall thickness was most significantly correlated with the metabolic activity at the excision site assessed by PET/CT (rho = 0.499, P = 4 x 10(-7)) and to thrombocyte counts from laboratory blood analyses (rho = 0.445, P = 3 x 10(-9)). Wall thickness was increased in patients suffering from diabetes mellitus, while it was significantly thinner in patients suffering from chronic kidney disease (CKD). Elastic AAA wall properties had significant correlations with the metabolic activity at the excision site (PET/CT), with existent calcifications, and with the diameter of the non-dilated aorta proximal to the AAA. Failure properties (wall strength and failure tension) had correlations with the patient's medical history and with results from laboratory blood analyses. Interestingly, AAA wall failure tension was significantly reduced for patients with CKD and elevated blood levels of potassium and urea, respectively, both of which are associated with kidney disease. This study is a first step to a future preoperative estimation of AAA wall properties. Results can be conveyed to both the diameter criterion and FE analyses to refine rupture risk prediction. The fact that AAA wall from patients suffering from CKD featured reduced failure tension implies an increased AAA rupture risk for this patient group at comparably smaller AAA diameters.