|
|
|
|
|
|
|
|
 |
||
|
|
||
| |||||||||
|
Tissue aspiration experimentThis experimental set-up has been designed originally by Vuskovic and Kauer [V. Vuskovic, Diss. ETHZ Nr. 14222; M. Kauer, Diss. ETHZ Nr. 14233]. Significant improvements for in-vivo applications were introduced by Nava [2t] and later by Hollenstein [5t]. In order to perform intraoperative measurements on humans, the measurement procedure must be non-traumatic, operate under sterile conditions and comply with the time- and space-limitations in the operating room, while at the same time allowing to maintain the appropriate control over the mechanical boundary conditions. The experiment is performed by establishing thorough contact between the probe head and the tissue, and creating a prescribed time-variable vacuum in the aspiration tube such that the tissue is sucked in through the aspiration hole. During a typical experiment, a (negative) suction pressure of up to 700mbar is applied such that the displacement of the tissue apex is in the order of 3-4mm. Tissue from the surface down to about 10 mm depth contributes to the measured mechanical response. A camera captures the full side view profile of the deforming tissue.
Pressure data and images are recorded at 25Hz. The probe is designed such that it can be completely disassembled for cleaning, and for ethylene oxide gas or plasma sterilization. Time histories of measured pressure and deformation profiles are the input data for determining the biomechanical characteristics of the tissue investigated, according to two approaches. The first method is based on the iterative comparison between predicted and measured tissue response, i.e. on the solution of the so called “inverse problem” using finite element calculations, e.g. [9p], [16p]. The second approach is based on characteristic scalar parameters extracted directly from the measured data, [11p], [12p], [19p], [43p].
The above descriptions and the sketch correspond to the “standard” version of our device, used for example for in vivo measurements on human liver during abdominal surgery ([24p], [16p], [17p], [14p], [2t], [5t]). Dedicated and optimized devices have been developed based on the same operation principle for other medical applications, such as for the measurements on the human cervix during pregnancy ([43p], [19p], [12p], [11p]), or for prolapse diagnosis, [5t]. The latest development is a new device which can be applied on internal organs during laparoscopic interventions, [33p], [5t].
[Top] | |||||||||||||||||||||||||
