日本コンピュータ外科学会誌 Vol. 19(2017) No. 2

Here we review the preclinical evaluation methodologies of thermal induced damage to tissues caused by surgical devices. Many innovative surgical devices based on thermal energy sources have been studied to offer less invasive treatment with fewer complications. Before these devices are used clinically, their safety must be validated using various methods to simulate the clinical situation with reasonable accuracy. We surveyed various preclinical studies and summarized methodologies to evaluate thermal induced damages. All the methodologies were categorized according to their invasiveness and measurement parameters (physical or biological parameters). In these studies, the damage was evaluated by one or more sub-assessments and attempted to clarify effective intensity and distribution of intervention to minimize the damage. For damage evaluation research, choice of techniques is extensive but decisions must be based on the nature of intervention.

An endoscope with assisting mechanism of Cochlear implant (hereinafter called “CI”) insertion in water for endoscopic ear surgery has been successfully fabricated and evaluated. This device consists of an endoscope with an imaging and a perfusion system and a CI insertion assisting mechanism at a tip of the endoscope. Outer and inner diameters of the endoscope shaft are 3.75 mm and 3.19 mm, respectively. A rod lens for an imager, optical fiber bundle for light guide and a silicone rubber tube are assembled into the shaft. The CI insertion assisting mechanism has not only insertion assistance function but also CI removal function. For the CI insertion assistance, a polyimide tube has been used as a sheath. For removal assistance, two kinds of mechanisms have been proposed. One is rotational mechanism and the other is opening mechanism using shape memory alloy wire actuator. Using the fabricated endoscope and the assisting mechanisms, CI insertion operation has been demonstrated by a medical doctor, and their functions and advantages were evaluated.

Our previous study revealed that the physiological lordosis of cervical spines was reduced in videofluorography during normal swallowing. In the study, cervical spines were manually extracted in all the frames of videofluorography. Therefore it was difficult to apply this extraction method to the videofluorography of larger dataset. The present paper proposes an automatic tracking method of cervical spinous processes, which are parts of cervical spines, in videofluorography by use of the two-dimensional template matching technique. In the method, cervical spinous processes can be extracted automatically, though templates should be set manually only in the first frame of videofluorography. The automatic tracking method was applied to from C1 to C6 cervical spinous processes in actual videofluorography of three cases, who were planned to undergo posterior cervical spinal fusion. The cervical spinous processes were able to be tracked at the accuracy of more than 85% in Jaccared index. The experimental results demonstrated that the proposed method was promising as a means of analyzing the motion of cervical spinous processes in videofluorography during swallowing.

The generation of patient-specific models is one of the difficult problems in the clinical application of surgery simulators. In particular, when estimation of soft tissue deformation is required, a finite element (FE) mesh needs to be generated from the patient's medical images. One of the effective methods of FE mesh generation is the volume embedding approach. In this approach, the medical volume data are embedded in a simple volumetric mesh such as orthogonal grid. However, the volume embedding method generates an incorrect boundary surface in the FE mesh. This makes it difficult to solve the contact problem between tools and embedded volumes. In this paper, an efficient contact handling method for embedded volumes using the signed distance field is described. In addition, its application to haptic rendering is introduced.