Estimation of ischemic tolerance time of rat liver by ultrasonic spectroscopy investigations

As a result of isolation from blood circulation in any organ the ischemic stress causes alterations in the physiological state of the cells. After the ischemic tolerance time the tissue is in a condition where resuscitation is no longer possible. Therefore the monitoring of the present state of the organ is a requirement in the investigations on the probability of successful revival of the organ. The modifications in the physiological state and in the tissue structure due to ischemic stress also alters the elasto-acoustic properties of the tissue. These effects can be detected by ultrasonic spectroscopy. The process of ischemia in rat liver specimen was investigated by the spectral analysis of the backscattered RF-data. The condition of the organ tissue was described by means of two frequency dependent acoustical parameters, the attenuation and the backscatter parameter, respectively. To improve the reliability of the method a set of independent scanlines of the specimen was used (B-mode like image). A dependence of the acoustic parameters on time, type of protection solution and temperature during ischemia was found. The use of a set of scanlines provides more information about the quality of the perfusion and protects from the inclusion of disruptive elements in the parameter analysis