Jørgensen C S, Dall F H, Jensen S L, Gregersen H
SA Laboratory at the Institute of Experimental Clinical Research, Aarhus University Hospital, Denmark.
J Biomech. 1995 Jul;28(7):863-7. doi: 10.1016/0021-9290(95)95275-a.
The aim was to develop a method for the quantification of the stress-strain distribution of tubular organs in vivo using the porcine duodenum as an experimental model. We placed four electrodes for impedance planimetry and a 20 MHz ultrasound transducer inside an inflatable balloon mounted on a 6 mm-diameter probe for intraluminal use. By means of the ultrasound transducer and the impedance planimetric system, we measured the wall thickness and luminal cross-sectional area of the duodenum. We calculated the luminal radius on the basis of the latter. We validated ultrasonic measurements of wall thicknesses by comparing the former to microscopic measurements of the wall thickness of unstrained duodenal specimens in vitro. Also, we tested whether the magnitude of the applied balloon pressure affected ultrasonic measurements in vitro. The luminal and the outer radius increased non-linearly by a factor of three, rising steeply at low balloon pressures, moderately at higher pressures. The wall thickness decreased as an almost linear function of the applied balloon pressure, resulting in a 50% decrease. The stress-strain distribution calculated on the basis of the balloon pressures, the wall thicknesses and the luminal radii were non-linear. The wall reached a maximum circumferential strain of 1.71 at 6 kPa, corresponding to a stress of 64.8 kPa. Our system enabled us to quantify the stress-strain distribution of the porcine duodenum in vivo, and it may become a valuable tool for future biomechanical investigations of tubular organs in health and disease.
目的是开发一种方法，以猪十二指肠为实验模型，在体内定量管状器官的应力-应变分布。我们将四个用于阻抗平面测量的电极和一个20 MHz超声换能器放置在一个安装在6毫米直径探头内的可充气气球内，用于腔内使用。借助超声换能器和阻抗平面测量系统，我们测量了十二指肠的壁厚和管腔横截面积。我们根据后者计算管腔半径。我们通过将前者与体外未受应变的十二指肠标本壁厚的微观测量结果进行比较，验证了壁厚的超声测量。此外，我们测试了施加的气球压力大小是否会影响体外超声测量。管腔半径和外半径非线性增加了三倍，在低气球压力下急剧上升，在较高压力下适度上升。壁厚随着施加的气球压力几乎呈线性函数下降，导致壁厚下降了50%。根据气球压力、壁厚和管腔半径计算出的应力-应变分布是非线性的。在6 kPa时，壁达到最大周向应变1.71，对应应力为64.8 kPa。我们的系统使我们能够在体内定量猪十二指肠的应力-应变分布，它可能成为未来对健康和疾病状态下管状器官进行生物力学研究的有价值工具。
