Journal of Computer Aided Surgery Vol.6 No.4
Abstract: This paper suggests an ultrasound guided needle insertion instrument which can compensate organ motion an deformation in real-time. Surgeons have suffered to find out the precise target position, particularly when the organ has movement caused by involuntary patient motion. The developed instrument can track target motion by image processing and visual servo control. In the experiments, it could correct the insertion path 7.69 times per second for a moving phantom, and the insertion error less than 3 mm was obtained. In pig experiments, the needle could be placed in the hepatic portal vein.
Keywords: Image-guided surgery, Needle insertion, Motion adaptive, Visual servo control.
Abstract: This paper presents a pneumatic chisel drive mechanism for osteotomy. This mechanism consists of a pneumatic cylinder, a piston, and a chisel. The back end of a chisel is inserted in the cylinder and supported by a spring. The piston in the cylinder is accelerated by compressed air supplied from the back end of the cylinder and collides with the chisel at the front end to give the impact for bone cutting. This mechanism allows the surgeon to hold the cylinder with both hands to aim the chisel edge at the desired point and direction without caring about striking the hammer. The stroke of the chisel is mechanically limited to reduce excessive cut. Dynamic characteristics, such as relationship between supply pressure and cutting power, is evaluated by experiments and analyses.
Keywords: Osteotomy, Chisel, Pneumatic drive.
Abstract: This paper developed an algorithm for rendering high-quality integral videography (IV) images for use in autostereoscopic three-dimensional (3-D) surgical display system. IV is an animated extension of integral photography, which provides 3-D images without having to use any supplementary glasses or tracking devices. Despite IV’s many advantages, the quality of its spatial image has thus far been poor. We proposed a high-quality image rendering method with oversampling technique to enhance the resolution of elemental IV image and a low-pass-filter to smooth the image. Testing of the method using a high-resolution IV display and
a test pattern showed that the qualities of the anti-aliased IV images were better than that of images rendered using a conventional method. An image-guided surgery display system incorporating the proposed algorithm would enable identification of optimum process for producing high-quality 3-D images for planning of and guidance during minimally invasive surgery.
Keywords: 3-D image, Integral Videography, Image assisted surgery, Oversampling, Low-pass-filter.
Abstract: Myocardial infarction and dilated cardiomyopathy significantly impair patients' cardiac functions. For these diseases, left ventricular plasty surgery has been used as a substitution for heart transplants from the 1980s and is improved to enhance the surgical effects and safety. We present a simulation system that enables cardiovascular surgeons to estimate functional improvements of left heart due to left ventricular plasty. The cardiac functions are evaluated with a PV diagram including emax, a ratio of left ventricular pressure to volume at the end systole. A normal heart, myocardial infarction, and postoperative heart were built on the finite element method (FEM). It was assumed that the ventricular wall of the model is composed of one-layer, elastic and isotropic material. We employed the Windkessel circulation model in order to compute PV diagrams. This paper presents the modeling method of a left heart on FEM, the simulation method, and an online output of the cardiac function calculations without FEM. Realistic trends of a PV diagram before and after left ventricular plasty surgery are computed.
Keywords: Cardiac function, Finite element method, Ventricular plasty surgery.
Abstract: Lasers have the capability to remove or cut bone precisely without large reaction forces. However, surgeons have had many difficulties with using lasers during operations because of the thermal damage. In this paper, we propose an optimization the overlapping ratio, using water cooling; for the efficiency of laser bone ablations per unit time without thermal damages for operational application. A water-cooling Er: YAG laser (18.5 J/cm2, l = 2.94 um, 20 Hz, 200 us) using optical fiber was operated at 0.5 - 3.0 mm/s moving velocities and repetitions. We focused specifically on the overlapping irradiated area and the interval time between the laser irradiations. Swine scapulae were ablated and its rate and performance were evaluated. The water-cooling Er: YAG laser obtained optimal ablation results when the moving velocity was set at 2.0 mm/s; the overlapping ratio is 0.89, and the ablated area along the troughs per unit time was optimized to 0.50 mm2 /s. Carbonization was not evident at this velocity. Controlling of the laser's moving velocity, we can optimize the ablation ability to 0.50 mm2 /s at 2.0 mm/s. At this velocity, the mass removal efficiency was at 208 ug/J. This result was almost same with previously conducted results accomplished by free running without water cooling.
Keywords: Ablation, Bone cutting, Laser, Water cooling.
Abstract: In neurosurgery such as the treatment of glioma, it is very important to remove tumor as accurately as possible at the boundary between tumor and normal tissue in order to prevent the recurrence. To achieve this, we had proposed a robotic laser scanning system using a micro laser with wave length of 2.8 um. This micro laser is suitable to remove the tumor at the brain surface because of its strong absorption feature by water. It is necessary, however, to keep the distance between the laser probe and the target at its focal length. In this research, we developed an automatic-focusing system using a guide laser and a CCD camera. In addition, we performed some experiments for evaluation in vitro and an in vivo test with the laser ablation on a porcine brain. Results showed that accuracy of focusing largely depends on the condition of the brain surface. In the near future, we will improve our method so that it will not be affected by the condition of the brain surface.
Keywords: Neurosurgery, Laser ablation, Automatic focusing, Medical robot, Brain tumor.