JP2011138350A - Anatomical structure analysis method for subject, display method for subject anatomical structure and subject anatomical structure display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent that quality of a structure of an internal organ or a tissue of a model is greatly depends on an arrangement position or the number of control lattice points of free-form deformation (FFD) algorithm, and to smoothly deform an attitude model while holding a bodily shape, the internal tissue, and the internal organ. <P>SOLUTION: The surface of a subject is divided into three-dimensional polygonal lattices (voxels), polygonal lattice data about each divided voxel are stored in a first storage part as surface voxel coordinates, mesh deformation is applied to each piece of voxel data related to the surface voxel coordinates read from the first storage part, the surface voxel coordinates in a state in which an attitude of the subject is deformed are calculated, the calculated surface voxel coordinates after the attitude deformation are stored in a second storage part as attitude deformation surface voxel coordinates, the inside of the subject is divided into the voxels, polygonal lattice data about each divided voxel are set as internal voxel coordinates, and internal voxel coordinates after interpolation are obtained by interpolating each piece of data related to the internal voxel coordinates by use of interpolation algorithm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to, for example, an object anatomy structure analysis method, an object anatomy structure display method, and an object anatomy structure display apparatus, and more particularly to an object anatomy structure analysis method and an object related to a posture deformation model of a human body based on voxels. The present invention relates to a display method for a body anatomy structure and a target body anatomy display apparatus.

  As the use of high-frequency electromagnetic fields has increased, concerns regarding the effects of high-frequency electromagnetic fields generated from wireless communication devices have increased. The International Commission on Non-Ionizing Radiation Protection and IEEE (The Institute of Electrical and Electronics Engineers, Inc .: Institute of Electrical and Electronics Engineers (IEEE)) set standards for exposure to high-frequency electromagnetic fields. These criteria are based on the rise in body temperature caused by the absorption of electromagnetic energy. Specific absorption rate (SAR) is an estimation criterion used to determine the safety of high-frequency electromagnetic fields, and accurate estimation of SAR plays an important role.

ここでσは、組織の伝導率[S/m]を表し、ρは組織の密度[kg/m^３]を表し、Ｅは組織内[V/m]の電磁界の強さを表す（ルートは平方根）。 The SAR is defined as shown in the diagram (1).

Here, σ represents the conductivity [S / m] of the tissue, ρ represents the density [kg / m ³ ] of the tissue, and E represents the strength of the electromagnetic field in the tissue [V / m] (root) Is the square root).

  However, it is difficult to estimate the SAR directly when a human is exposed to a high frequency electromagnetic field. This is because the SAR value estimated in the diagram (1) includes the electric field strength and conductivity in the human body. Therefore, SAR has been estimated by a numerical analysis method using a voxel model of the human body that expresses the anatomical structure of the human body with minute elements.

  First, around mid-1990, an anatomical model of the head developed to estimate SAR when using a mobile phone using medical image data (Non-Patent Documents 3 to 7). Since the latter half of 1990, with the development of medical image engineering and computer performance, an anatomical model of the whole body of an adult has been developed using magnetic resonance imaging (MRI) and anatomical photographs of the human body (Non-Patent Documents 8 to 13). . These models have been used under various circumstances in order to estimate the SAR of the entire human body (Non-Patent Documents 8 to 13).

  Most recently, several anatomical models of children and pregnant women have been developed to estimate the SAR of children, pregnant women and fetuses. On the other hand, various human voxel models for the evaluation of ionizing radiation have also been created. These models can also be used for non-ionizing radiation (eg, SAR estimation) (Non-Patent Documents 20 and 21).

  However, these models typically use an upright posture, and there are limitations (problems) to simulate the actual usage of wireless communication devices such as mobile phones and laptop computers equipped with wireless LAN. is there.

  Various posture models allow us to evaluate whether electromagnetic fields are safe in actual exposure situations. However, it is difficult to create another posture model from the original standing posture. This is because the voxel model includes internal structures and complex body shapes. The sitting posture model is formed by cutting or sticking the lower limbs of the original model, allowing for the study of electromagnetic dosimetry on the sitting human body during whole body exposure in the radio frequency range ( Non-patent documents 22, 23). Based on the original model, Findlay and Dimbyro were formed by adding a model sitting in the standing model and two upper body models, and estimated SAR (Non-patent Documents 24 and 25). In order to develop these models, the limbs of the original model were cut, rotated, and reattached to the torso. Body tissue was maintained by manually reassembling the joints. Researchers who wrote Dawson and his co-authors also developed models of sitting postures and postures of reaching out hands (Non-Patent Documents 26 and 27). These models were edited manually after rotating the limbs of the standing model with a computer program. However, it is time consuming and difficult to develop a new complex posture model while performing manual work.

  In order to address these problems, the present inventors have previously developed a posture deformation technique for a voxel human body model using a free-form deformation (FFD) algorithm (Non-patent Document 28).

  This technique makes it possible to smoothly deform the posture model while maintaining the body shape, internal tissue, and organs on the voxel model. However, there is room for improvement in this technique in that the quality of the structure of the tissue or organ of the model greatly depends on the position and number of control grid points of the free-form deformation (FFD) algorithm.

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Co-authored by Dawson, Capta, and Stuly “Study on Electromagnetic Wave Exposure of UK Workers” Medical Bio 47, 995-1012 2002

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Co-authored by Sederberg and Parry “Free pose geometry model” ACM Siggraph Conference Proceeding, pages 151-16 pages 1986

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  The present invention has been made to solve the above problems, and the present inventor proposes a new posture deformation technique. That is, the object of the present invention is to maintain the body shape, internal tissue, and organs, regardless of the position and number of control lattice points of the free-form deformation (FFD) algorithm. However, a posture deformation technique for a voxel human body model using a free-form deformation (FFD) algorithm, which can smoothly deform the posture model, and more specifically, an anatomical structure of an object having such a possibility An analysis method, a display method of a target body anatomy structure, and a target body anatomy structure display device are provided.

  Therefore, in the present invention, for human voxel models, a review of posture deformation technique using a free-form deformation (FFD) algorithm, a new method for removing the technically negative aspects of the prior art related to posture deformation, The new method is verified by experiments.

Specifically, in order to solve the above-described problem, the object anatomy analysis method according to claim 1 of the present application divides the surface of the object into a three-dimensional polygonal lattice (voxels), and each divided voxel is divided. Storing polygonal lattice data for as a surface voxel coordinate in the first storage unit,
By applying mesh deformation to each voxel data related to the surface voxel coordinates read from the first storage unit, calculating surface voxel coordinates in a state where the object is subjected to posture deformation, and the calculated surface voxel after posture deformation The coordinates are stored in the second storage unit as posture deformed surface voxel coordinates,
Interpolation obtained by dividing the inside of the object into voxels, and using polygonal lattice data for each divided voxel as internal voxel coordinates, and interpolating each data related to the internal voxel coordinates using an interpolation algorithm It is characterized by obtaining rear internal voxel coordinates.

  The first storage unit and the second storage unit are, for example, databases, and may be anything that has a function of storing and storing data obtained by the calculation method according to the present application.

  The target object refers to, for example, the human body, but may be a living organism such as an animal, a plant, or an insect, or a non-living object having a joint or similar structure (for example, a joint structure). A human body model, a robot, etc.).

  A three-dimensional polygonal lattice (voxel) means a box-type pixel, and refers to a technology that divides three-dimensionally by a unit lattice.

  Adding mesh deformation to each voxel data related to the surface voxel coordinates means that when changing the posture of an object (for example, a human body) from an upright position to sitting on a chair, the voxel data of the object is made to correspond to the posture deformation. In this application, it is based on the mathematical processing described later. However, even if it is modified by other processing methods, it can be reasonably processed that it is transformed from one aspect to another. Everything can be considered.

  Interpolating each piece of data related to the internal voxel coordinates using an interpolation algorithm is based on, for example, formulating a Laplace equation for the voxel coordinate data and discretizing it using a finite difference method (FDM) to obtain a solution. All the voxels in the boundary area are related to the voxel coordinates with points of the body surface polygon mesh, and other solutions are used to map the deformed volume from the boundary area to the source volume area by applying a certain rule. There may be.

  According to the above configuration, the post-deformation data of the internal voxel data is obtained mathematically by a certain interpolation rule in correspondence with the posture deformation of the voxel data on the body surface. It is possible to smoothly deform the posture model while maintaining the body shape, internal tissue, and organs, regardless of the position and number of control lattice points in the free-form deformation (FFD) algorithm. Become.

In addition, in order to solve the above-described problem, the object anatomical structure display method according to claim 2 of the present application divides the surface of the object into a three-dimensional polygonal lattice (voxels), and the divided voxels are divided. Are stored in the first storage unit as surface voxel coordinates,
By applying mesh deformation to each voxel data related to the surface voxel coordinates read from the first storage unit, calculating surface voxel coordinates in a state where the object is subjected to posture deformation, and the calculated surface voxel after posture deformation The coordinates are stored in the second storage unit as posture deformed surface voxel coordinates,
Interpolation obtained by dividing the inside of the object into voxels, and using polygonal lattice data for each divided voxel as internal voxel coordinates, and interpolating each data related to the internal voxel coordinates using an interpolation algorithm Store the rear internal voxel coordinates in the third storage unit,
The coordinate data stored in the second and third storage units are read out and displayed three-dimensionally.

  According to such a configuration, since a display function is further added to the above-described configuration, more accurate image display can be performed after the posture deformation of the voxel data inside the target body. For example, in the treatment, diagnosis, etc. for the human body It is possible to support from the system side to perform more precise medical practice.

Moreover, in order to solve the said subject, the target object anatomy structure display apparatus which concerns on Claim 3 of this application includes the surface division part for dividing | segmenting the surface of a target object into a three-dimensional polygonal lattice (voxel),
A first storage unit for storing polygonal lattice data for each voxel divided by the surface dividing unit as surface voxel coordinates;
Posture deformation surface voxel coordinate calculation for reading surface voxel data related to surface voxel coordinates from the first storage unit, adding mesh deformation to the data, and calculating surface voxel coordinates in a state in which the object is subjected to posture deformation And
A second storage unit for storing the calculated surface voxel coordinates after posture deformation as posture deformation surface voxel coordinates;
An internal divider for dividing the interior of the object into voxels;
An internal voxel coordinate interpolation unit for interpolating each data related to internal voxel coordinates for each voxel divided by the internal division unit using an interpolation algorithm;
A third storage unit for storing the interpolated internal voxel coordinates obtained by the internal voxel coordinate interpolation unit;
A display unit that reads out the respective coordinate data stored in the second and third storage units and displays them in a three-dimensional manner.

  According to this configuration, the object anatomy structure analysis method and the object anatomy display method having the above-described configuration can be realized as a single device. Therefore, by widely distributing devices having this function, it is possible to improve the quality of services such as medical diagnosis and treatment for the entire region and country.

  According to the present application, since the post-deformation data of the internal voxel data is obtained mathematically by a certain interpolation rule in accordance with the posture deformation of the voxel data on the body surface, the structure of the model tissue or organ The posture model can be smoothly deformed while maintaining the body shape, internal tissue, and organs, regardless of the position and number of control grid points of the free-form deformation (FFD) algorithm. .

  Further, according to the present application, more accurate image display is possible after the posture deformation of the voxel data inside the target body, and for example, in the field of treatment, diagnosis, etc. for the human body, more precise medical practice can be performed. Can support from.

  Furthermore, according to the present application, by distributing devices having this function widely, it is possible to improve the quality of services such as medical diagnosis and treatment for the entire region and country.

It is a figure explaining the concept which sorts | segments a body part based on the node (joint) node of a human body model. It is the figure which showed the control lattice point allocated over the whole body of a human body voxel model. It is a conceptual diagram for demonstrating the basic concept of the volume filling illustrated by a two-dimensional similar organ. It is a figure which shows the outline | summary of the attitude | position deformation | transformation technique which concerns on one Embodiment of this invention. It is a figure which shows the outline | summary of the skeleton assembly work which concerns on one Embodiment of this invention. It is a figure which shows 3D grid display of the original attitude | position figure (a) and attitude | position deformation | transformation figure (b) which concern on one Embodiment of this invention. It is a figure showing the voxel model of Japanese men and women of the standing figure which concerns on one Embodiment of this invention. It is the figure showing what constructed the sitting voxel model with the interpolation algorithm concerning one embodiment of the present invention. It is the figure which showed the percentage difference which compared the tissue amount of the sitting posture model created using the interpolation algorithm and FFD algorithm which concern on one Embodiment of this invention with the original standing posture model. It is the functional block diagram which showed the structure of the human anatomy structure analysis / display apparatus which concerns on one Embodiment of this invention. It is a flowchart for demonstrating operation | movement of the human body anatomy structure analysis and display apparatus 20 which concerns on one Embodiment of this invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the following, the range necessary for the description for achieving the object of the present invention is schematically shown, and the range necessary for the description of the relevant part of the present invention will be mainly described. Are according to known techniques.

<Review of conventional technology>
The posture deformation technique of the human body voxel model previously proposed by the present inventors is reviewed (Non-patent Document 28). The rough model, including the fact that the boundary of the tissue forms a human voxel model, but is not smooth, has a large numerical error when estimating electromagnetic field exposure by numerical simulation at higher frequencies. turn into. Freeform Deformation Method (FFD) was introduced by Sederberg and Parry, but is effective for multi-purpose 3D geometric models found in computer designs and computer graphics (CG). To do. By this method, it is possible to easily deform the control grid point by arranging or moving it around the three-dimensional object. Therefore, the authors applied a free-form deformation (FFD) algorithm to deform a human body voxel model including complicated motion such as node rotation. First, we introduced the concept of nodes (joints) in a voxel model that allows the model's body parts such as arms and legs to move like a real human. In doing this, one node (joint) is defined as a point on the voxel model. This point is assumed to be the center of human movement.

  FIG. 1 is a diagram illustrating a concept of sorting body parts based on nodes (joint) nodes of a human body model. In the figure, the model is divided into 19 parts according to the nodes (joints), each of which is distinguished by color shades, and the joint parts are indicated by ◯.

  Next, FIG. 2 is a diagram showing control grid points assigned over the entire body of the human body voxel model. As shown in the figure, FFD control grid points are assigned to the entire body of the human voxel model. Control grid points define a space that is affected by the movement and rotation of the nodes (joints) of the model. A control grid point is associated with each node (joint). The voxel is then converted to a polyhedron with vertices on each of the four sides. Finally, after changing the posture by moving the control grid point, the hexahedral mesh is revoxed.

  The present inventor also applied this posture deformation method to a Japanese model and verified the quality of six types of posture models (Non-Patent Document 28). As a result of the experiment, it was difficult to maintain the correct anatomical structure around the deformed node (joint) of the complex posture deformation model. On the other hand, the present inventor has confirmed that the posture is smoothly deformed by the proposed technique while maintaining the continuity of the model and internal tissues and organs. However, the quality of the structure of these tissues and organs greatly depends on the position and number of control grid points in the free-form deformation (FFD) algorithm, and specialized techniques are required for the placement of the control grid points.

<Proposal of posture deformation technique>
What is needed is a posture deformation control method that is easy for the user to use, and a smooth posture deformation technique. Fortunately, tools for posture deformation of polygonal mesh models have been extensively studied, and there are general methods of posture deformation for polygonal mesh models, skeletons and skinning. As a result, the authors decided to use polygonal meshes so that users can use each other efficiently. In this paper, we will use the term “body surface polygon mesh”, which is a polygonal mesh that means the surface of the human body.

  The body surface polygon mesh is embedded in the volume data. The body surface polygon mesh does not include internal structures such as tissues and organs. Therefore, volume data converted by a currently used technique such as voxelization is limited to binary information roughly classified as in the body or other areas. In order to overcome this limitation, the present inventor has come up with a new method of interpolation.

  FIG. 3 is a conceptual diagram for explaining a basic concept of volume filling exemplified in a two-dimensional similar organ. In the figure, (a) shows image data of a source (original), and (f) shows image data after transformation. (B) and (e) respectively represent coordinate image data (hereinafter also referred to as “coordinated image data”) of (a) and (f). (C) shows the body surface polygon mesh extracted from the source image data and the deformed polygon mesh. (D) shows coordinate image data displayed by rasterizing the deformed body surface polygon mesh. Only the pixels at the boundary are indicated by coordinate values.

  That is, FIG. 2 is a diagram illustrating a basic concept of interpolation according to an embodiment of the present invention using a 2D image. As shown in the figure, it can be applied to 3D volume data by increasing the size. (A) shows an image source to be deformed, and (f) is data of a deformed image as a result. In order to create an image as shown in FIG. 3 (f), the pixels I and J (upper case is the notation on the transformed image) in FIG. 3 (e) are replaced with the pixels i and j of the image source (lower case is on the image source). (Represented and displayed with a light colored circle). Therefore, image deformation is regarded as a process of creating image data (FIG. 3E), and pixels I and J have the same unit value as pixels i and j, and V (I, J) = i, j. indicate. The inventor calls this image data “coordinated image data”. FIGS. 3B and 3E respectively show the source and deformed coordinate image data. The grids in FIGS. 3B and 3E mean the curve curves necessary for i and j. Each grid corresponds to a pixel on the image source. In the present invention, the 3D version of coordinated image data is referred to as “coordinated volume data”.

  The method invented by the present inventor is to perform posture deformation using a body surface polygon mesh as shown in FIG. Since the body surface polygon mesh displays only the boundary region of the human body model, the deformation of the mesh cannot be followed only by the information of the internal pixel coordinates. By rasterizing the mesh, an imperfectly coordinated image (FIG. 3 (d)) including the coincidence of the source pixel and the boundary area displayed in blue circles is obtained. In order to create a complete coordinated image (FIG. 3 (e)) from an imperfectly coordinated image, it is necessary to reconstruct the harmony of all internal pixels represented by red circles from the pixels in the boundary area.

  In order to realize the interpolation algorithm, the inventor applied several grid generation methods. The boundary fit method (BFM, hereinafter referred to as “BFM”) is a well-established lattice generation method (Non-patent Document 30). BFM builds a mesh in a curve area from several sets of grid points in the boundary area. The coordinates of the inner region are determined using the solution of the elliptic partial differential equation from the coordinates in the boundary region. This method provides excellent results in that there is continuity, smooth and accurate deformation and is considered to meet the inventor's purpose.

The posture deformation technique proposed by the present inventor consists of three steps. (See Figure 4)
1) Extraction of body surface polygon mesh from human body model 2) Skeleton assembly and posture deformation with commissural skeleton 3) Interpolation

  FIG. 4 is a diagram showing an outline of a posture deformation technique according to an embodiment of the present invention. In the figure, (a) shows the volume displayed on the original voxel model. 4B and 4C are an original body surface polygon mesh and a body surface polygon mesh whose posture is deformed, respectively. As will be described in A below, the color of the polygon mesh (its shading) represents voxel coordinates that coincide with the grid points on the mesh. The inventor used a commercially available Autodesk Maya 2008 (trademark) for this mesh deformation stage. At this point, the user only needs to use software. This is because there is no concern about volume data. The inventor will explain the deformation process of the mesh in B below. FIG. 4 (d) illustrates the resulting volume data. The most important thing in the stage from FIG. 4C to FIG. 4D is interpolation. Details of the interpolation will be described below.

A Body surface polygram mesh extraction There are several methods for extracting a polygon mesh from volume data. The marching cube (hereinafter referred to as “MC”) is the most famous algorithm (Non-patent Document 31). However, MC sometimes fails to make a closed surface, which can cause holes in body surface polygons. The body surface polygon mesh needs to be closed when it is converted to a volume at the interpolation stage. If there is a hole in the body surface polygon mesh, the volume may collapse as a result. Therefore, the inventor uses a mesh extraction technique that creates a polygon between a human voxel and a background voxel. The algorithm for this technique (in pseudocode) is:

For each voxel in a volume dataset

For each 6-adjacent voxels

If the current voxel belongs to the human body

region and the adjacent voxel belongs to the

background

Then generate a polygon between these voxels

End If

End for
End
for

  Here, the apex portion of the body surface polygon mesh is the corner of the voxel and is represented as (i, j, k). Here, i, j, and k are integers. The authors associate the vertices of the body surface polygon mesh with the display voxel of the index (i, j, k). In doing this, the texture coordinates associated with the index are used to keep a record of the associated voxel index (i, j, k). The vertex of the voxel corresponding to the posture-transformed body surface polygon mesh requires interpolation (C below). Therefore, vertex and voxel coincidence must be followed through mesh deformation. Even if the vertex changes, the texture coordinates remain unchanged, so the two do not match. The inventor performs mesh smoothing on the extracted mesh (Non-Patent Document 32). The voxel vertices do not change for the same reason described previously, but the position changes as a result of mesh smoothing.

B. Assembly of Skeleton and Modification of Posture with Commissural Skeleton FIG. 5 is a diagram showing an outline of the skeleton assembly work according to one embodiment of the present invention. In the figure, (a) shows a skeleton structure, (b) shows a boundary mesh attached to the skeleton, and (c) shows a boundary mesh. As shown in the figure, a skeleton structure is attached to the mesh. The skeleton structure consists of bones and joints. Bones connect with joints to create a hierarchical structure. The work of attaching to the skeleton structure is called “skeleton setup” (Non-patent Document 33). On the CG, the skeleton structure is attached to a human body mesh model for moving the human body model. Once the skeleton structure is attached to the mesh, the vertices of each mesh are deformed together with the skeleton structure (Non-patent Document 34).

  Skeletons can be clarified in two main ways. Forward kinematics (FK; hereinafter referred to as “FK”) and inverse kinematics (IK; hereinafter referred to as “IK”). While FK requires a clear joint angle, IK provides a simple way to clarify posture. The present inventor has selected one of the methods for mesh posture deformation.

  When the skeleton is set, it can be smoothly deformed by using the attached mesh and skinning algorithm. Skeleton animation and skinning are common techniques in the CG and gaming industries, and readily available application software products such as Autodesk Maya ™ support this technology. Since this work is unique to software, it is not described in this article. In this paper, we explain the posture deformation that can be achieved simply by setting a skeleton.

C Interpolation There is currently a body surface polygon mesh whose posture has been deformed. First, a body surface polygon mesh is converted into a binary volume database using a voxelization technique using graphic hardware (Non-patent Document 35). The body surface polygon mesh is converted into slice-type voxels. A method of displaying a body surface polygon mesh in a slice in a triangle through an open graphics library (Open Graphics Library (Open GL)) of a program interface is used. If the voxel is inside the posture deformable body surface polygon mesh, the value is set to 1. In other cases, the value is 0. In the present invention, the boundary area of the volume data is defined as a voxel other than 0 and next to 0. Every border voxel is associated with a voxel coordinate with a body polygon mesh point. An image is constructed from the boundary of the deformed volume to the source volume. The last task is to create internal voxel coordinates. In the boundary region, voxel coordinates are interpolated to complete coordinated volume data of the deformed volume.

  The inventor defines a number of terms and notations for mathematical formulation. The inventor's volume data is specialized for human body data and includes two areas of the human body and the background. Name the internal voxels of the human body model. For example, the non-zero voxel described above is attached as a support area. When S is a support area, the voxel in the boundary area is expressed as “∂S”. The inventor defines the problem as follows.

を仮定する。

となるような１対１写像Ｆ：Ｖｄ→Ｖｓを見つける。
（Ｆとｆは、Ｆ^ｉ（ｉ＝１，２，３）及びｆ^ｉ（ｉ＝１，２，３）がスカラー関数であるとき、Ｆ＝（Ｆ^１，Ｆ^２，Ｆ^３）とｆ＝（ｆ^１、ｆ^２、ｆ^３）と定義付けられる３Ｄベクトル関数である。） Let Vs be the source volume support area and Vd be the binary volume support area. One-to-one mapping

Assuming

Find a one-to-one mapping F: Vd → Vs such that
(F and f are F = (F ¹ , F ² , F ³ ) and f when F ⁱ (i = 1, 2, 3) and f ⁱ (i = 1, 2, 3) are scalar functions. = 3D vector function defined as (f ¹ , f ² , f ³ ).

  f is the voxel coordinate of the boundary area, and F is the voxel coordinate of the support area.

ここで、Δは、３Ｄラプラシアン演算子で、
Δ＝∂^２/∂x^２＋∂^２/∂ｙ^２＋∂^２/∂ｚ^２
と定義される。 Since there is a Dirichlet boundary value problem, a solution for F is obtained by the following Laplace equation.

Where Δ is the 3D Laplacian operator
Δ = ∂ ² / ∂x ² + ∂ ² / ∂y ² + ∂ ² / ∂z ²
Is defined.

ここで、∇は、勾配演算子（∂ｘ、∂ｙ、∂ｚ）である。 The solution of the Laplace equation is obtained with the Dirichlet boundary value, and the solution F becomes a smooth one-to-one mapping with continuity. This equation consists of the following minimization problem:

Here, ∇ is a gradient operator (∂x, ∂y, ∂z).

(| ∇F ¹ | ² + | ∇F ² | ² + | ∇F ³ | ² ) can be considered as the rate of change in volume or density (Non-patent Document 30). In this sense, F is a deformation minimization map, and it can be expected that the reconstructed volume data becomes smooth.

のように離散化される。ｉ,ｊ,ｋは格子点を表す。 This equation is discretized with numbers to give an answer. Since the calculation region is a linear lattice, that is, a voxel lattice, it can be easily calculated by the finite difference method (FDM). The Laplace equation for solving all F ^l (l = 1, 2, 3) is a finite difference equation.

It is discretized as follows. i, j, and k represent lattice points.

If (i, j, k) is inside Vd, F ^l (i, j, k) is an unknown. When (i, j, k) is on the ∂Vd boundary, F ^l (i, j, k) is constant. Finally, a linear equation is derived. Various numerical methods are available to solve this large linear equation. A sequential overrelaxation method (SOR, hereinafter referred to as “SOR”) is applied to a finite difference equation for each configuration of F ⁱ (i = 1, 2, 3). SOR can be performed easily and brings sufficient results to the present invention.

Coordinate volumes are created by interpolation. The voxel values of the coordinate volume of (i, j, k) are (F ¹ (i, j, k), F ² (i, j, k), F ³ (i, j, k)). To create deformed volume data, the source volume is resampled by referring to the coordinated volume.

  FIG. 6 is a diagram showing a 3D grid display of an original posture diagram (a) and a posture deformation diagram (b) according to an embodiment of the present invention. In (a), the thinnest line (original red line) is parallel to the i-axis, the next lightest line (original green line) is parallel to the axis j, and the darkest line (original blue line). ) Is parallel to the axis k. In (b), the three color curves show the mapping image of the line in (a). In the figure, the apex portion of the body surface polygon mesh is the voxel corner, which is represented as (i, j, k). Here, i, j, and k are integers. That is, the figure shows voxel coordinate curves of source coordinate volume data and deformed volume data. The curve of the source coordinate volume is an orthogonal lattice, and the deformed volume data is a curved lattice. The lattice is smoothly deformed without interruption. The deformation of the lattice is limited to the indirect bending region, and can be expected to be a volume deformation characteristic.

<Experimental result>
Here, the experimental results of the posture deformation technique proposed by the present inventor are evaluated. This technique was applied to an adult male and female voxel model developed by the present inventors. FIG. 7 is a diagram illustrating a voxel model of Japanese men and women standing up according to an embodiment of the present invention. These models are composed of legislative models with 2 mm resolution and are divided into 51 different tissues. In the figure with added volume, the bones of the model are highlighted. In the sagittal plane diagram, tissues and organs are displayed in different colors (light shades). The bones are displayed in white and dark (originally brown). These models were created from MRI data of healthy people close to the Japanese average, 171.4 cm for men, 63.1 kg for women, 159.1 cm for women and 52.6 kg. These models are standing in a style with both hands on their side as seen in FIG. It is a legislative model with 2 millimeter resolution and is divided into 51 tissues and organs.

  The inventor created body surface mesh models for these models and set up a skeleton using software Maya. As an example, I made a mesh model with a sitting posture at Software Maya. FIG. 8 is a diagram illustrating a construction of a sitting voxel model using an interpolation algorithm according to an embodiment of the present invention. The sitting posture model is constructed by the deformation technique proposed here. In the figure with the volume added, the bones of the model are highlighted. In the sagittal view, tissues and organs are displayed in different colors. The bones are displayed in white and dark (originally brown). Reconstruction by interpolation was performed on an XP Professional (32-bit) PC with AMD Opteron 2.6-GHz × 2 dual-core processes and 3 gigabyte RAM within 30 minutes. This time is the same as the time spent on the previous posture deformation.

  From FIG. 7 and FIG. 8, it is clear that the sitting male / female model can be smoothly deformed while holding internal tissues and organs. As seen in the sagittal plane of the male model in FIG. 8, the patella of the model is created above the knee relative to the anterior surface by the FFD algorithm (Non-Patent Document 28) (this is anatomically) The patella of the sitting model is anatomically correct.

  The weights of the sitting male and female models are 3.8% and 2.2% lighter than the original standing model, respectively. The inventor has compared the sizes of the main structures of the standing model and the sitting model. FIG. 9 shows the difference, and the tissue amount of the sitting posture model created by using the interpolation algorithm or the FFD algorithm (Non-Patent Document 28) according to one embodiment of the present invention is used as the original standing posture model. It is the figure which showed the percentage difference compared with.

  That is, FIG. 9 shows a difference in size of the sitting model (Non-patent Document 28). As a result, it turned out that the size of the structure of the sitting model created by the interpolation algorithm is lighter than the original model. While the error of the structure of the model created by the interpolation algorithm is within 8%, the error of the original model structure was slightly larger than the sitting model. In the case of the technique that deformed the posture in this paper, it can be concluded that the error in the size of the tissue mainly occurs when the mesh is deformed. The internal volume of the mesh area was changed when the mesh was deformed. The rate of change depends on the skinning algorithm. In the case of the present inventor, the skinning algorithm means the “smooth skinning” function of Autodesk Maya 2008 Software ™. The volume is changed in the area near the bend, and there is almost no change in the other parts. The volume change rate is equal at the bending joint, which is a numerical characteristic of the Dirichlet boundary problem. The volume change rate is determined only by the space change, and the error of the organization is not related. The resampling process of the pose deformation technique (see “C” above) can also produce another error. The sampling process of the source volume causes an aliasing problem in which a curve is jagged on a computer. It is estimated that the error caused by the resampling process is reduced by using the anti-aliasing technique. However, this error is not so important when the human body evaluates exposure to electromagnetic fields. This is because an uncertainty of 20% to 30% is generally included.

  On the other hand, it should be noted that the method proposed in the present invention has its limitations. The meshes with deformed postures cannot intersect. The mesh representing the human body has only one internal area. However, a mesh that intersects itself may have two internal regions. Then, when voxelization is performed at the interpolation stage, there is a possibility that an erroneous area is converted into two or more intersecting areas. As a result, when the posture deforming meshes intersect themselves, there is a possibility that erroneous volume data is created in the posture deforming model by the interpolation work.

<Conclusion>
The present inventor has proposed a new posture modification technique for a human voxel model. In the proposed technique, the polygon mesh of the model is created based on the body surface of the voxel model and is deformed using a skeleton animation of a commercially available 3D CG software function. An arbitrary voxel model is constructed by applying an interpolation algorithm to the deformed mesh data. In order to verify the behavior of the proposed posture transformation technique, this technique was used to construct a sitting posture model from standing Japanese men and women. As a result, these sitting posture models were able to smoothly perform posture deformation while maintaining the structural state of internal tissues and organs. Furthermore, in the evaluation of the exposure of the electromagnetic field to the human body, the weight of the tissue and organ of any model relative to the original standing model tissue and organ weight was a reasonable difference. Various human voxel models can be constructed easily and quickly using the proposed posture deformation technique. The posture model constructed by the author's technique can be used for simulating the exposure evaluation of the electromagnetic field when the wireless communication device or the wireless terminal is actually used.

<Embodiment as an object anatomy display apparatus>
FIG. 10 is a functional block diagram showing the configuration of the human anatomy structure analysis / display apparatus according to an embodiment of the present invention. As shown in the figure, the human anatomical structure analysis / display device 20 includes a surface dividing unit 210 that executes, as an algorithm, a function of dividing the surface of the human body model 1 in a standing posture into a three-dimensional polygonal lattice (voxel). Postural deformation that performs a function of calculating postural deformation surface voxel coordinates 320 of the human body model 11 after deforming posture (for example, sitting posture) by applying mesh deformation to the obtained surface voxel data 310 and deforming the human body model 1 By applying an interpolation algorithm to the surface voxel coordinate calculation unit 220, an internal division unit 230 that executes the function of dividing the inside of the human body model 11 into voxels as an algorithm, and each of the divided internal voxel coordinate data 330 The function of interpolating and obtaining internal voxel coordinate data 340 after interpolation is an algorithm. An internal voxel coordinate interpolation unit 240 to be executed, and a display unit 250 that reads the posture-deformed surface voxel coordinates 320 and the interpolated internal voxel coordinate data 340 stored in the respective storage devices and displays them on the monitor 40 in a three-dimensional manner. Configured. In addition, a first storage device 260 for storing and storing the surface voxel data 310 as a surface voxel coordinate database, and a second storage for storing and storing the posture deformed surface voxel coordinates 320 as a posture deformed surface voxel coordinate database. A device 270 and a third storage device 280 for storing and storing the interpolated internal voxel coordinate data 340 as an interpolated internal voxel coordinate database are provided. FIG. 1 shows an example in which the first storage device 260, the second storage device 270, and the third storage device 280 are provided separately from the human anatomy structure analysis / display device 20. It may be stored inside the analysis / display device 20. Further, the human anatomy structure analysis / display device 20 and each of the storage devices 260 to 280, the human anatomy structure analysis / display device 20, and the monitor 40 may be connected by a network or may be directly connected.

  The surface division unit 210 and the internal division unit 230 divide the human body surface and the inside of the human body as the object into a three-dimensional unit grid in units of three-dimensional polygonal grids (voxels), and use the divided units as voxel coordinates. Arithmetic unit (unit), central processing unit (unit), processor, or a program or software for causing a computer to execute such a function, a routine, or these in an executable format. This is realized by a recording medium or a recording medium (hereinafter referred to as “program etc.”) incorporating this recording medium.

  As described above, the posture deformation surface voxel coordinate calculation unit 220 has a function of performing data conversion when the posture of the human body is changed from, for example, an upright posture to a chair posture by applying mesh deformation. This is realized by a program to be executed.

  As described above, the internal voxel coordinate interpolation unit 240 formulates a Laplace equation for the voxel coordinate data and discretizes it using a finite difference method (FDM) to obtain a solution. All the voxels in the boundary area are associated with the voxel coordinates with points on the body surface polygon mesh, and the mapping from the boundary area of the deformed volume to the area of the source volume has a function. Is done.

  The display unit 250 has a function of visualizing desired data by reading out information from a storage device or the like and outputting the information to the monitor (device) 40 after performing a certain display enabling operation. Specifically, it has a function of creating three-dimensional display data based on the posture-deformed surface voxel coordinates 320 and the interpolated internal voxel coordinate data 340 stored in the storage devices 270 and 280 and displaying them on the monitor 40. It is realized by a program that executes such a function.

  Next, the operation of the human anatomy structure analysis / display apparatus configured as described above will be described.

  FIG. 11 is a flowchart for explaining the operation of the human anatomical structure analysis / display device 20 according to an embodiment of the present invention. As shown in the figure, first, the surface dividing unit 210 divides the surface of the human body model 1 in the standing posture into a three-dimensional polygonal lattice (voxel), and the surface voxel data 310 thus obtained is used as a surface voxel coordinate database. 1 storage device 260 (step S101).

  Next, the posture-deformed surface voxel coordinate calculation unit 220 applies mesh deformation to the surface voxel data 310 to calculate the posture-deformed surface voxel coordinates 320 of the post-deformed posture human body model 11, and thus obtained posture-deformed surface voxel coordinates 320. Is stored in the second storage device 270 as a posture-deformed surface voxel coordinate database (step S102).

  Next, the internal division unit 230 divides the inside of the human body model 11 into voxels to obtain internal voxel coordinate data 330 (step S103).

  Next, the internal voxel coordinate interpolation unit 240 interpolates each internal voxel coordinate data 330 by applying an interpolation algorithm to obtain post-interpolation internal voxel coordinate data 340, and thus the interpolated internal voxel coordinate data thus obtained. 340 is stored in the third storage device 280 as an interpolated internal voxel coordinate database (step S104).

  Next, the display unit 250 reads the posture-deformed surface voxel coordinates 320 and the interpolated internal voxel coordinate data 340 stored in the respective storage devices, and displays them three-dimensionally on the monitor 40 (step S105).

  As described above in detail, according to the present invention, the post-posture deformation data of the internal voxel data is obtained mathematically by a certain interpolation rule in accordance with the posture deformation of the voxel data on the body surface. Since the quality of the structure of the tissue and organ of the model is not greatly affected by the position and number of control lattice points of the free-form deformation (FFD) algorithm, the posture model is maintained while maintaining the body shape, internal tissue, and organs. Can be smoothly deformed.

  Further, according to the present invention, a more accurate image display can be performed after the posture deformation of the voxel data inside the target body, for example, in a system for performing a more precise medical practice in the place of treatment, diagnosis, etc. for the human body Support from the surface.

  In addition, according to the present invention, it is possible to improve the quality of services such as medical diagnosis and treatment for the entire region and country by widely distributing devices having this function.

  The above-described embodiment is merely an example for realizing the technical idea according to the present invention, and the technical idea according to the present invention can be applied to other embodiments.

  Furthermore, even when the apparatus, method, and system produced using the present invention are mounted on the secondary product and commercialized, the value of the present invention is not reduced at all.

  As described above, according to the present application, more accurate image display is possible after posture deformation of the voxel data inside the target body, and for example, more precise medical practice is performed in the field of treatment, diagnosis, etc. for the human body. Is possible.

  Therefore, the present application has great applicability for the information industry including the medical machine industry.

DESCRIPTION OF SYMBOLS 1 ... Human body model, 11 ... Post-deformation posture (for example, sitting posture) human body model, 20 ... Human body anatomy structure analysis and display apparatus, 40 ... Monitor, 210 ... Surface division part, 220 ... Posture deformation surface voxel coordinate calculation part, 230 ... Internal division unit 240 ... Internal voxel coordinate interpolation unit 250 ... Display unit 260 ... First storage device 270 ... Second storage device 280 ... 31st storage device

Claims (3)

Dividing the surface of the object into a three-dimensional polygonal lattice (voxels), storing polygonal lattice data for each of the divided voxels as surface voxel coordinates in a first storage unit;
By applying mesh deformation to each voxel data related to the surface voxel coordinates read from the first storage unit, calculating surface voxel coordinates in a state where the object is subjected to posture deformation, and the calculated surface voxel after posture deformation The coordinates are stored in the second storage unit as posture deformed surface voxel coordinates,
Interpolation obtained by dividing the inside of the object into voxels, and using polygonal lattice data for each divided voxel as internal voxel coordinates, and interpolating each data related to the internal voxel coordinates using an interpolation algorithm A method for analyzing an anatomical structure of an object, characterized by obtaining posterior internal voxel coordinates. Dividing the surface of the object into a three-dimensional polygonal lattice (voxels), storing polygonal lattice data for each of the divided voxels as surface voxel coordinates in a first storage unit;
By applying mesh deformation to each voxel data related to the surface voxel coordinates read from the first storage unit, calculating surface voxel coordinates in a state where the object is subjected to posture deformation, and the calculated surface voxel after posture deformation The coordinates are stored in the second storage unit as posture deformed surface voxel coordinates,
Interpolation obtained by dividing the inside of the object into voxels, and using polygonal lattice data for each divided voxel as internal voxel coordinates, and interpolating each data related to the internal voxel coordinates using an interpolation algorithm Store the rear internal voxel coordinates in the third storage unit,
A method for displaying a target anatomical structure, wherein the respective coordinate data stored in the second and third storage units are read and displayed three-dimensionally. A surface dividing unit for dividing the surface of the object into a three-dimensional polygonal lattice (voxel);
A first storage unit for storing polygonal lattice data for each voxel divided by the surface dividing unit as surface voxel coordinates;
Posture deformation surface voxel coordinate calculation for reading surface voxel data related to surface voxel coordinates from the first storage unit, adding mesh deformation to the data, and calculating surface voxel coordinates in a state in which the object is subjected to posture deformation And
A second storage unit for storing the calculated surface voxel coordinates after posture deformation as posture deformation surface voxel coordinates;
An internal divider for dividing the interior of the object into voxels;
An internal voxel coordinate interpolation unit for interpolating each data related to internal voxel coordinates for each voxel divided by the internal division unit using an interpolation algorithm;
A third storage unit for storing the interpolated internal voxel coordinates obtained by the internal voxel coordinate interpolation unit;
An object anatomical structure display device comprising: a display unit that reads out the respective coordinate data stored in the second and third storage units and displays them three-dimensionally.

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