Endoscopic surgery is minimally invasive and presents many advantages for the patient such as reduced pain, less scarring, and quicker recovery. However, endoscopic cameras offer a narrow field of view and display only visible surfaces, which limit the application range for surgery. Thus, augmented reality (AR) visualization superposition of pre-or intra-operative 3-dimensional (invisible) information about the interior of tissues such as a tumor in a 2-dimensional endoscopic view has become an important research challenge. The purpose of our study was to realize a real-time endoscopic image overlay system for intra-operative localization of a tumor in deformative organs. Thus, we have proposed a method for endoscopic image overlay called “direct calibration of endoscopic camera (DCEC)” and developed a prototype of the system based on 3-dimensional measurement using micro-fluxgate magnetic sensors in combination with the DCEC. In this paper, we propose a novel procedure to collect sample points for the DCEC using a permanent magnet as a sample point generator under the condition that another permanent magnet is embedded in the vicinity of the tumor. To evaluate the effectiveness of the proposed procedure, we estimated a threshold of magnetic force generated from one permanent magnet embedded near the tumor through computer simulation.
