Bagi P, Thind P, Colstrup H
Department of Urology, Rigshospitalet, Copenhagen, Denmark.
Med Biol Eng Comput. 1993 Nov;31(6):580-4. doi: 10.1007/BF02441805.
Based on a theoretical model, the urethral stress-relaxation response following a sudden forced dilatation was studied in ten healthy female volunteers. The energy dissipation following a sudden urethral dilatation proved to follow the function Y = Z + C alpha e-t/tau alpha + C beta e-t/tau beta. Hence, a mechanical model was chosen, consisting of two Maxwell elements and one Hooke element coupled in parallel. The decay in force following deformation may be described as F = F(o) exp (-t.E/eta) for each Maxwell element. Thus, it was possible to determine the elastic E and viscous eta coefficients for the participating mechanical equivalents in the model, and thereby quantitatively describe the visco-elastic properties in the urethra. The reproducibility of the elastic and the viscous coefficients proved to be fairly high, and they seemed to be unaffected by the size of dilatation. On the other hand, the rate of dilatation clearly influenced the computed parameters. However, this phenomenon was easily explained by the duration of the deformation, which allowed the viscous elements to move before any measurements were performed. The present method permits in vivo evaluation of the elastic and viscous properties of the urethra, as well as other accessible biological tubes, and may be of value in the description of normal physiological and pathophysiological behaviour of the structures studied.
基于一个理论模型，对10名健康女性志愿者在突然强制扩张后尿道的应力松弛反应进行了研究。结果表明，尿道突然扩张后的能量耗散符合函数Y = Z + Cαe^(-t/τα) + Cβe^(-t/τβ)。因此，选择了一个由两个麦克斯韦元件和一个胡克元件并联组成的力学模型。每个麦克斯韦元件变形后力的衰减可描述为F = F(0) exp (-t.E/η)。由此，可以确定模型中参与的力学等效元件的弹性系数E和粘性系数η，从而定量描述尿道的粘弹性特性。弹性系数和粘性系数的可重复性相当高，而且它们似乎不受扩张大小的影响。另一方面，扩张速率明显影响计算参数。然而，这种现象很容易用变形持续时间来解释，因为变形持续时间使得粘性元件在进行任何测量之前就发生了移动。本方法允许对尿道以及其他可触及的生物管道的弹性和粘性特性进行体内评估，并且在描述所研究结构的正常生理和病理生理行为方面可能具有价值。
