NAKADA Teruhiro Yamagata University, School of Medicine, Professor, 医学部, 教授 (50009495)
KUBOTA Yohko Yamagata University, School of Medicine, Associate Professor, 医学部, 助教授 (60125763)
|Budget Amount *help
¥2,400,000 (Direct Cost : ¥2,400,000)
Fiscal Year 1997 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1996 : ¥1,800,000 (Direct Cost : ¥1,800,000)
It is commonly pointed out that dynamic properties soft tissues can provede us additional mechanical informations. Therefore, they can be quite significant as one criteria for the method of diagnosis in normal and pathological mammalian internal organs. A new approach is presented here to establish identification for dynamic properties of mammalian biological soft tissues. Its theoreticla principles are developed and possible applications are also investigated. A linear biological soft tissue strip is attached at the tip of small uniform cantilever beam and is modeled by the combination of spring and dashpot. Dynamic properties of this biological soft tissue, which are viscoelastic and have strong dependence upon frequency, are measured as capabilities of vilbration absorber against free damped vibrations of the small cantilever beam. Natural frequency and logarithmic decrement of the vibrations of the whole system are experimentally measured. Then, by enforcing theoretical analysis, e
lasticity constant and viscous damping coefficient of the tissue are computed to characterize viscoelastic properties of the soft tissues.
The normal, hypertrophic and cancerous biopsy specimen, which are picked out from prostate tissue of human, have been used to demonstrate the feasibility of this method. There was a significant correlation between the viscous damping coefficient and elasticity constant in the case of normal and cancer, while in hypertrophic, there was negative correlation. In cancer tissues, though they have a good correlation coefficient, the range is quite narrow, which means that they lost the ability to coordinate structure and function because of the cancer cell. On the other hand, there exists distinctive differences in the gradient of regression line among normal, cancer and hypertrophic. These suggest that the relationships between viscous damping coefficient and elasticity constant provides useful information in diagnosis for the human prostate tissue.
Also, aorta wall tissue of normal and the spontaneously hypertensive rat have examined to investigate influences of hypertension and aging upon mechanical properties of the aorta wall tissue. The results suggest that characteristics of dynamic elasticity constant and viscous damping coefficient of the aorta wall tissue can reflect effects of hypertension and aging. The presence or the lack of material adaptation and remodeling of arterial wall may play the main roll for the results obtained.