We are developing a pseudo 3D visualization system by superimposing ultrasound images for endoscopic ultrasonography. The system consists of an ultrasonic endoscope and an electro-magnetic measurement sensor. The pseudo 3D volume is reconstructed by superimposing ultrasound images captured by the ultrasonic endoscope at arbitrary points, and displayed for surgeons by overlaying on endoscopic images in real-time.
We are conducting joint researches with Medical School of Kyushu University and Osaka University. The research topics include the navigation system for endoscopic robotics surgery, 3D diagnosis system for hip replacement surgery, image guide for endotracheal intubation, etc. For instance, we propose a method to estimate a 3D shape of patient's femur from two radiographs and a parametric femoral model. Firstly, we develop the parametric femoral model utilizing statistical procedure of 3D femoral models taken by CT images of a number of patients. Then, the pose and patient-specific shape parameters of the parametric model are estimated from two 2D radiographs using a distance map constructed by the Level Set Method. Experiments using synthesized images, fluoroscopic images of a phantom femur, and in vivo images for hip prosthesis patients are successfully carried out, and it is verified that the proposed system has practical applications.
We have proposed a new registration algorithm of 2D color images and 3D geometric models for the navigation system of surgical robot. A 2D-3D registration procedure is used to precisely superimpose a tumor model on an endoscopic image and is therefore indispensable for the surgical navigation system. Thus, the performance of the 2D-3D registration procedure influences directly the usability of the surgical robot operating system. One of the typical techniques that has been developed is the use of external markers. However, the accuracy of this method is reduced by the breathing or heartbeat of the patient, as well as other unknown factors. For precise registration of 3D models and 2D images without external markers or special measurement devices, a new registration method is proposed that utilizes the 2D images and their distance maps as created by the Fast Marching Method.