Shinobu Mizuta

Graphic and movie illustrations of human prenatal development and their application to embryological education based on the human embryo specimens in the Kyoto collection

Morphogenesis in the developing embryo takes place in three dimensions, and in addition, the dimension of time is another important factor in development. Therefore, the presentation of sequential morphological changes occurring in the embryo (4D visualization) is essential for understanding the complex morphogenetic events and the underlying mechanisms. Until recently, 3D visualization of embryonic structures was possible only by reconstruction from serial histological sections, which was tedious and time‐consuming. During the past two decades, 3D imaging techniques have made significant advances thanks to the progress in imaging and computer technologies, computer graphics, and other related techniques. Such novel tools have enabled precise visualization of the 3D topology of embryonic structures and to demonstrate spatiotemporal 4D sequences of organogenesis. Here, we describe a project in which staged human embryos are imaged by the magnetic resonance (MR) microscope, and 3D images of embryos and their organs at each developmental stage were reconstructed based on the MR data, with the aid of computer graphics techniques. On the basis of the 3D models of staged human embryos, we constructed a data set of 3D images of human embryos and made movies to illustrate the sequential process of human morphogenesis. Furthermore, a computer‐based self‐learning program of human embryology is being developed for educational purposes, using the photographs, histological sections, MR images, and 3D models of staged human embryos. Developmental Dynamics 235:468–477, 2006.

Visualization of human prenatal development by magnetic resonance imaging (MRI).

It is essential to visualize the structures of embryos and their internal organs three‐dimensionally to analyze morphogenesis; this used to rely solely on serial histological sectioning and solid reconstruction, which were tedious and time‐consuming. We have applied imaging with a magnetic resonance (MR) microscope equipped with a 2.35 T superconducting magnet to visualize human embryos; we were successful in acquiring high‐resolution sectional images and in identifying the detailed structures of major organs. The imaging process was facilitated by using a super‐parallel MR microscope. A dataset of MR images of more than 1,000 human embryos, now collected, will be important for future biomedical research and for education.

Prostaglandin E2 facilitates excitatory synaptic transmission in the nucleus tractus solitarii of rats.

Prostaglandin E2 (PGE2) binding sites are rich in the nucleus tractus solitarii (NTS). We studied the effects of PGE2 on evoked excitatory postsynaptic currents (eEPSCs) and miniature EPSCs (mEPSCs) in voltage-clamped neurons in rat NTS slices. eEPSCs and mEPSCs, mediated by non-NMDA glutamate receptors, fluctuated in size from event to event. In 37.5% of neurons, PGE2 increased the mean size of eEPSCs and changed the size distribution non-proportionally. In 42.9% of neurons, PGE2 increased the frequency of mEPSCs keeping the skewed size distribution unchanged. However, PGE2 did not modulate postsynaptic non-NMDA receptor sensitivity. We propose that size distributions of eEPSCs before and after PGE2 application are predictable from those of mEPSCs by quantal analysis with multinomial distribution. Our results suggest that PGE2 facilitates evoked and spontaneous release of glutamate vesicles.

Detailed motion analysis of the left ventricular myocardium using an MR tagging method with a dense grid

Detailed analysis of myocardial deformation through a whole cardiac cycle was accomplished using a tagging method with a high‐density grid. Four sets of tagged images with a 4‐mm‐spacing grid were measured by generating four tagging pulses arranged at regular intervals in the cardiac cycle. Through each set of images, tag intersections were tracked semi‐automatically. The estimated motions of tag intersections were concatenated so that sequential positions of myocardium were connected through a whole cardiac cycle. In vitro evaluation of the precision of this technique showed that the mean error of tracked 4‐mm tag intersections was less than 0.47 ± 0.17 mm, even on the quite low‐contrast images, and the concatenation error caused by double concatenation was comparable to the interpolation error in the subendocardial area obtained with 8‐mm tag intersection motion. The small difference between the two mean distance curves of the in vivo evaluation indicated that the method is useful for analyzing heart wall abnormalities. Magn Reson Med 44:73–82, 2000.

Construction and application of 3D model sequence to illustrate the development of the human embryo

Embryology is one of the basic subjects in medical education, to learn the process of human development especially from fertilization to birth. The shape deformation in the development of human embryo is one of the most important points to be comprehended, but it is difficult to illustrate the deformation by texts, 2D drawings, photographs and so on, because it is extremely complicated. The purpose of our research is to construct a 3D model sequence to illustrate the deformation of human embryo, and to make the model sequence into the teaching materials for medical education. Firstly, 3D images of the specimens of human embryo were acquired using MR microscopy. Next, an initial 3D model sequence was manually modified by comparing with the features of the acquired images under the supervision of medical doctors, because the images were influenced not only by the noise or limitation of resolution in MR image acquisition, but also by the variation of shape depending on the difference of subject. Using the constructed 3D model sequence, CG animations and an interactive VRML system were composed as the teaching materials for embryology. These materials were quite helpful to understand the shape deformation compared with the conventional materials.

Description of digital images by region-based contour trees

In analyzing the morphological information of objects in images, isosurfaces play important and application-independent roles. For continuous scalar field, Contour Trees have been used as a tool to select and visualize isosurfaces. However, the tree structure of contour trees is based on the critical points which does not exist in digital images. In this paper, we propose a tree structure of isosurfaces in digital images named Region-based Contour Tree. The proposed method describes a finite number of isosurfaces in digital images completely, without redundancy.

Volume Visualization Using Gradient-Based Distance among Voxels

The aim of this work is to visualize 3D objects in volume data with minimum numbers of user-defined models or parameters. In this report, we propose a novel method that utilizes the distances along the optimum paths between a seed voxel in a target object and other voxels. The distance here is defined using gradient between adjacent voxels along the path. The distance is also used as the criterion of path optimization. The visualization is carried out by rendering the volume where the initial voxel values are replaced with the distances. Experimental results for an image of human embryo obtained with MR microscopy have displayed the effectiveness of this method.

Simultaneous process of automated 3D registration and segmentation on medical images

we propose a novel method that deals with simultaneous process of registration among images and segmentation of image using plural images for 3D head images of different modalities in identical subject. In this method, image segmentation is performed by using the result of vector quantification (VQ) for multi-dimensional feature space distribution that describes the relation of voxel value. Registration is carried out by optimization of parameters of translation and rotation using the minimization of VQ distortion. First, we examined characteristics of feature space histogram using simplified head images. Next, we showed the usefulness of proposed method for these images. Here, we estimated the measure of VQ distortion and automated method to extract VQ centroids. Finally, an example that applied this method to T1 emphasized MR image and cbf-PET image was shown.

Three-dimensional reconstruction of the coronary arterial tree from several sets of biplane angiograms with simultaneous estimation of imaging geometry

A new method is proposed for reconstructing the 3D structure of the coronary arterial tree from angiograms. Instead of identification of corresponding points on the images, several sets of biplane angiograms are used, and the parameters of the imaging geometries are simultaneously estimated. Several sets of biplane angiograms are usually obtained during one angiographic test. However, only one set of biplane angiogram is usually used for 3D reconstruction of the coronary arterial tree. If only one set of biplane angiogram is used for 3D reconstruction, it is necessary to identify corresponding points on both images. Identification of correspondent points on both images is, however, very difficult and often impossible. To overcome this difficulty, we use several sets of biplane angiograms for 3D reconstruction. If the precise parameters of the imaging geometries are known, the 3D structure of the coronary arterial tree can be obtained by back parameters of the imaging geometries are known, the 3D structure of the coronary arterial tree can be obtained by back projecting each angiogram. However, only the approximate parameters of the imaging geometries are usually known. Therefore, we developed a method for 3D reconstruction of a coronary arterial tree with simultaneous estimation of the imaging geometry. In this paper, we present the algorithm for our method and demonstrate the application to clinical data.

Bio-Medical Application of Information Systems

Our laboratory focuses on the applications of information systems to biomedical researches in the COE program. We have constructed 3D morphology database system of human embryo and biomedical simulation system of the heart. The 3D morphology database system is assembled from a huge collection of human embryo samples and the 3D morphology is derived from real measurement data. By searching document data concerning embryo, parents and pregnancy, user can observe 3D morphological data of the embryo and compare them. For the simulation of the heart, we have designed and constructed a system dedicated to biomedical simulation by taking account of hierarchical structures of biological system from molecular scale to body scale. The wall motion simulation of the heart using our biomedical simulation system is based on cellular level model of cardiac muscle and physiological behavior of heart can be reproduced from cell to organ level