As liver is the venous organ, the elasticity is changed by blood distribution in the liver. Surgeons adjust the operation in accordance with the hardness of the liver. In laparoscopic surgery, however, as surgeons cannot touch liver directly, they determine its hardness based on laparoscopic images only. Although the gripping force measuring device for the elasticity measurement of organ intra-operation have been developed, it still has a problem of the jaw gripping shape by pin joints. Jaw griping shape cannot uniformly compress the organ, so there is a problem that the most compressed part of the organ is apt to be damaged. In order to solve this problem, calipers shaped measurement device was developed, though, it is not supposed to be used in laparoscopic surgery. In this study, we aimed to develop a calipers shaped elasticity measuring device it could be used in laparoscopic surgery. It approaches from various directions, and compresses organs uniformly.
The device was designed to be inserted through a hole of φ12 mm for using the trocar. To apply to the laparoscopic surgery, we applied foldable calipers shaped mechanism. As an evaluation, reproducibility evaluation test, ex vivo and in vivo experiments using swine liver were carried out. Full scale 1.4 N, and the error was less than ±3% in reproducibility evaluation. Further, from comparison of the results of in vivo and ex vivo, we could evaluated the properties of the liver successfully. In the in vivo experiments, the elasticity value measurement of the liver was done within 3 minutes without big problem.
We have successfully developed a new foldable calipers shaped elasticity measuring device that can be used laparoscopic surgery. We will increase the number of measurements in the in vivo as a future work.