This paper presents a new colonoscope navigation system. CT colonography is utilized for colon diagnosis based on CT images. If polyps are found while CT colonography, colonoscopic polypectomy can be performed to remove them. While performing a colonoscopic examination, a physician controls colonoscope based on his/her experience. Inexperienced physicians may occur complications such as colon perforation while colonoscopic examinations. To reduce complications, a navigation system of colonoscope while performing the colonoscopic examinations is necessary. We propose a colonoscope navigation system. This system has a new colonoscope tracking method. This method obtains a colon centerline from a CT volume of a patient. A curved line (colonoscope line) representing the shape of colonoscope inserted to the colon is obtained by using electromagnetic sensors. A coordinate system registration process that employs the ICP algorithm is performed to register the CT and sensor coordinate systems. The colon centerline and colonoscope line are registered by using a line registration method. The position of the colonoscope tip in the colon is obtained from the line registration result. Our colonoscope navigation system displays virtual colonoscopic views generated from the CT volumes. A viewpoint of the virtual colonoscopic view is a point on the centerline that corresponds to the colonoscope tip. Experimental results using a colon phantom showed that the proposed colonoscope tracking method can track the colonoscope tip with small tracking errors.
A volume phase holographic grating (VPHG) achieves very high diffraction efficiency up to 100% for S or P polarized
light at the first diffraction order. However, diffraction efficiency of the VPHG for non-polarized light becomes low
according as Bragg angle becomes large, and bandwidth of diffraction efficiency becomes narrow according as refractive
index modulation of grating lattice becomes small. A volume binary grating with rectangular lattice, consists of high and
low refractive index media with large or small duty ratio, is able to achieve very high efficiency nearly 100% and a wide
band width for both S and P polarization light. We have successfully fabricated germanium immersion gratings of step
groove shape with resolving power of 45,000 at 10 micron by using a nano-precision 3D grinding machine and ELID
(ELectrolytic In-process Dressing) method. However, the method requires a large amount of machine times and efforts.
We had proposed a novel immersion grating with slot shape lattice of total reflection mirrors, which achieves high
performance and lower fabrication cost. We describe the photolithography and the latest plasma nano-technologies for
fabrications of the novel diffraction gratings in our presentation. We also introduce birefringence volume gratings in this