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Takeyoshi Dohi

Publications and source records attributed to Takeyoshi Dohi.

9 recordsLinked to original sources
PubMed2005

Three-dimensional display with a long viewing distance by use of integral photography.

We developed a technique of three-dimensional (3-D) display for distant viewing of a 3-D image without the need for special glasses. The photobased integral photography (IP) method allows precise 3-D images to be displayed at long viewing distances without any influence from deviated or distorted lenses in a lens array. We calculate elemental images from a referential viewing area for each lens and project the corresponding result images to photographic film through each lens. We succeed in creating an image display that appears to have three dimensionality even when viewed from a distance, with an image depth of 5.7 m or more in front of the display and 3.5 m or more behind the display. To the best of our knowledge, the long-distance IP display presented here is technically unique because it is the first report of generation of an image with such a long viewing distance.

Data Display↗
PubMed2005

Scalable high-resolution integral videography autostereoscopic display with a seamless multiprojection system.

We propose a scalable high-resolution autostereoscopic display that uses integral videography (IV) and a seamless multiprojection system. IV is an animated extension of integral photography (IP). Although IP and IV are ideal ways to display three-dimensional images, their spatial viewing resolution needs improvement; the pixel pitch of the display and the lens pitch are the main factors affecting IV image quality. We improved the quality by increasing the number and density of the pixels. Using multiple projectors, we create a scalable high-resolution image and project it onto a small screen using long-focal-length projection optics. To generate seamless IV images, we developed an image calibration method for geometric correction and color modulation. We also fabricated a lens array especially for the display device. Experiments were conducted with nine XGA projectors and nine PCs for parallel image rendering and displaying. A total of 2868 x 2150 pixels were displayed on a 241 mm x 181 mm (302.4 dots/in.) rear-projection screen. The lens pitch was 1.016 mm, corresponding to 12 pixels of the projected image. Measurement of the geometric accuracy of the reproduced IV images demonstrated that the spatial resolution of the display system matched that of the theoretical analysis.

Journal Article↗
PubMed2005

Intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery for tumor resection rate control.

RATIONALE AND OBJECTIVES: Gross-total surgery under intraoperative magnetic resonance imaging (MRI) is a promising method of glioma removal. The purpose of this article is intraoperative measurement of resected tumor volume in MRI-guided glioma surgery using semiautomatic image segmentation to unbiased resection rate control. MATERIALS AND METHODS: A newly developed software program based on a fuzzy connectedness (FC) segmentation algorithm was used to achieve fast and semiautomatic tumor segmentation and tumor volume measurement. The program was validated by retrospective study of eight glioma cases and then applied to seven glioma cases. All clinical cases underwent actual MRI-guided surgery using 0.3-T open magnets. RESULTS: The volume of the tumor before resection ranged from 10.1 to 206.7 mL. A comparison of the results of manual segmentation with those of the semiautomatic FC-based segmentation gave an average dice similarity coefficient of 0.80 and an average match of 76%. Volume measurement combined with a developed software program enabled quantitative monitoring of tumor removal, which was critical in the near-total resection of glioma in MRI-guided surgery. CONCLUSION: The FC-based tumor segmentation method can be used for intraoperative tumor segmentation and volume measurement in MRI-guided glioma surgery using 0.3-T open magnets. This method is useful for objective resection rate monitoring, which may ultimately minimize the amount of residual tumor in glioma surgery.

Adolescent↗
PubMed2004

Motion tracking in MR-guided liver therapy by using navigator echoes and projection profile matching.

RATIONALE AND OBJECTIVES: Image registration in magnetic resonance (MR) image-guided liver therapy enhances surgical guidance by fusing preoperative multimodality images with intraoperative images, or by fusing intramodality images to correlate serial intraoperative images to monitor the effect of therapy. The objective of this paper is to describe the application of navigator echo and projection profile matching to fast two-dimensional image registration for MR-guided liver therapy. MATERIALS AND METHODS: We obtain navigator echoes along the read-out and phase-encoding directions by using modified gradient echo imaging. This registration is made possible by masking out the liver profile from the image and performing profile matching with cross-correlation or mutual information as similarity measures. The set of experiments include a phantom study with a 2.0-T experimental MR scanner, and a volunteer and a clinical study with a 0.5-T open-configuration MR scanner, and these evaluate the accuracy and effectiveness of this method for liver therapy. RESULTS: Both the phantom and volunteer study indicate that this method can perform registration in 34 ms with root-mean-square error of 1.6 mm when the given misalignment of a liver is 30 mm. The clinical studies demonstrate that the method can track liver motion of up to approximately 40 mm. Matching profiles with cross-correlation information perform better than with mutual information in terms of robustness and speed. CONCLUSION: The proposed image registration method has potential clinical impact on and advantages for MR-guided liver therapy.

Echo-Planar Imaging↗
PubMed2004

Surgical navigation by autostereoscopic image overlay of integral videography.

This paper describes an autostereoscopic image overlay technique that is integrated into a surgical navigation system to superimpose a real three-dimensional (3-D) image onto the patient via a half-silvered mirror. The images are created by employing a modified version of integral videography (IV), which is an animated extension of integral photography. IV records and reproduces 3-D images using a microconvex lens array and flat display; it can display geometrically accurate 3-D autostereoscopic images and reproduce motion parallax without the need for special devices. The use of semitransparent display devices makes it appear that the 3-D image is inside the patient's body. This is the first report of applying an autostereoscopic display with an image overlay system in surgical navigation. Experiments demonstrated that the fast IV rendering technique and patient-image registration method produce an average registration accuracy of 1.13 mm. Experiments using a target in phantom agar showed that the system can guide a needle toward a target with an average error of 2.6 mm. Improvement in the quality of the IV display will make this system practical and its use will increase surgical accuracy and reduce invasiveness.

Depth Perception↗
PubMed2004

[The overview of robot surgery].

Surgical operations have developed in the method which skillful surgeon's hands and eyes are used. However, to realize a new surgical therapy in the 21st century, it is necessary to use various advanced technologies; surgical robots, three dimensional medical images, computer graphics, computer simulation technology and others. Three dimensional medical image for surgical operation provides surgeons with advanced vision. Surgical robots provide surgeons with advanced hand, but it is not a machine to do the same action of a surgeon using scissors or a scalpel. The advanced vision and hands available to surgeons are creating new surgical fields which are minimally invasive surgery, non-invasive surgery, virtual reality micro-surgery, tele-surgery, fetus surgery, neuro-informatics surgery and others in the 21st century.

Computer Graphics↗
PubMed2003

Three-dimensional volume rendering of fetal MR images for the diagnosis of congenital cystic adenomatoid malformation.

RATIONALE AND OBJECTIVES: Great expertise is necessary to mentally compile a series of individual two-dimensional image sections into a three-dimensional (3D) composite view that can aid in differential diagnosis. The purpose of this study was to test 3D volume-rendering techniques for differentiating congenital cystic adenomatoid malformation from congenital diaphragmatic hernia. MATERIALS AND METHODS: The authors acquired T2-weighted magnetic resonance (MR) images of a 27-week fetus in the sagittal plane and then applied the 3D volume-rendering method to the MR image data sets to obtain a composite 3D image. RESULTS: It was unclear on the MR images whether the intestines were situated above or below the diaphragm. The composite image showed that the intestines were not herniated into the chest, and this facilitated a diagnosis of congenital cystic adenomatoid malformation rather than congenital diaphragmatic hernia. CONCLUSION: The 3D volume-rendering techniques aided in the assessment of fetal organ structure and could be applied also to preoperative simulation and planning of fetal surgery.

Cystic Adenomatoid Malformation of Lung, Congenita↗
PubMedDate not supplied

Feasibility study of imaging of intraductal papillary mucinous tumors of the pancreas based on integral photography.

BACKGROUND/AIMS: The principle of integral photography was first proposed by Lippman in 1908. Recently, the three-dimensional display system based on the principle of integral photography was developed. It projects three-dimensional objects using a lens array called a fly's eye lens and photographic film. Some groups have used it for surgical navigation in brain surgery. In this study, we tried to generate integral photographic images of intraductal papillary mucinous tumors of the pancreas, and evaluated the feasibility of this method. METHODOLOGY: Five patients with an intraductal papillary mucinous tumor of pancreas were studied. We used MRI data as three-dimensional data. MRI data were acquired with a 1.5-T clinical imager (Signal.5; GE Medical Systems, U.S.A). We used multi-slab single-shot fast spin-echo sequences. Section thickness was between 2 and 3mm in the coronal plane. From these data, integral photographic images were generated on a liquid crystal display by a three-dimensional rendering algorithm. RESULTS: Three-dimensional images using the principle of integral photography could be generated in all 5 cases. We could recognize these images as three-dimensional images by slightly moving the viewpoint to up, down, left, and right. From these images, we were able to grasp the three-dimensional relationship between the tumor, bile duct, and pancreatic duct. Using these three-dimensional images, a variety of minimally invasive surgical procedures were performed for intraductal papillary mucinous tumor of the pancreas, more safely and speedily than formerly. CONCLUSIONS: The images based on integral photography are suitable for medical imaging and are useful for surgical planning.

Adenocarcinoma, Mucinous↗