KR20100099507A - Implant simulation system using haptic interface - Google Patents

Abstract

PURPOSE: An implant simulation system using a haptic interface is provided to supply an implant operation experience by providing a physical/virtual implant operation environment which are almost similar to an actual implant operation environment. CONSTITUTION: A haptic device(100) implements a force or haptic for implementing the actual feel of a cure tool, and outputs the signal depending on the mechanical displacement of an operating unit(110), and displaces the operating unit according to the input signal having the information for the reaction force. A display unit(200) outputs the shape models(210,220) for a bone and an operating tool virtually. A controller(300) updates the shape and location information of the shape model outputted to the display unit according to the signal inputted from the haptic device.

Description

Implant Simulation System Using Haptic Interface

The present invention relates to an implant simulation system using a haptic interface, and more specifically, through a virtual bone model and a virtual treatment device to which a haptic interface based on a volume model is applied, the user is almost physically and visually identical to the actual implant surgery. An implant simulation system using a haptic interface capable of providing an in- implant surgical experience.

In general, haptics refers to a sensory interface technology that allows a user to feel haptics, power, and movement through a keyboard, a mouse, a joystick, and a touch screen as a user's input device.

Conventional computer technology mainly uses audiovisual information to exchange information with humans and computers. However, users want more specific and realistic information through virtual reality, and haptic technology that delivers tactile and power was developed to satisfy this.

Basically, creating a simulator using haptic technology requires haptic devices, haptic rendering and computer graphics technology. Here, the haptic device is a mechanical device having a pen-shaped manipulation unit, and is designed for interaction between a human and a virtual environment. The user gives commands to the virtual environment through the haptic device and feels the touch or power coming from the virtual environment.

The haptic technology has recently been proposed in the medical field due to the advancement of the haptic device technology as well as the computer environment, and many studies related to medical simulation of haptic feedback have been proposed. Because of this, the interest of these bone-related surgical simulations is steadily increasing.

In particular, with regard to implant surgery during bone-related surgery, except for professional dentists who have a lot of dental experience, they have learned how to handle dental tools and feel how the teeth of the patient come in contact with the dental tools. Although it should be learned, dental students receiving conventional dental treatment training have received dental treatment training using extracted teeth and artificial teeth of dental patients.

 However, in the case of dental training using artificial teeth, artificial teeth have been limited in expressing various structures, shapes, and the degree of damage of teeth that require the treatment of actual patients. In addition, in the case of implantation, the processing of the gum bone as well as the teeth should be made, but since the rigidity of the teeth and the gum bones are different, it is difficult to obtain the treatment of processing the gum bone only by the treatment training for the tooth. There was this.

In addition, advanced dental experiences have been costly because of the costly use of expensive artificial teeth and bones of the body.

The present invention was created in order to solve the above-described problems, by providing a virtual and surgical implant surgery environment that is almost the same as the actual, the implant simulation system using a haptic interface that can substitute the actual implant surgery experience The purpose is to provide.

Implant simulation system using a haptic interface according to the present invention for achieving the above object, as a force or tactile echo device for realizing the real feeling of the treatment tool, outputs a signal according to the mechanical displacement of the operation unit, the feedback (Feedback) A haptic device in which the manipulation unit is displaced according to an input signal having information about a force; A display unit configured to output a virtual shape of the bone shape model of the affected area requiring treatment and the treatment tool shape model used to treat the affected area as a virtual image; The shape and position information of the bone shape model and the treatment tool shape model are output in real time on the display unit according to a signal input from the haptic device, and the bone shape model and the treatment tool shape model are based on a volume model. And a controller configured to calculate a reaction force according to a collision of and transmit a signal having information on the calculated reaction force to the haptic device.

In this case, the collision test between the bone shape model and the treatment tool shape model is performed using the point shell of the bone shape model and the distance field of the treatment tool shape model, and is applied to the bounding sphere of the treatment tool shape model. A point shell of the included bone shape model may be extracted, and the value of the distance field may be queried from the extracted point and the sign may be determined to check whether the bone shape model and the treatment tool shape model collide with each other.

In addition, the point shell included in the boundary of the treatment tool shape model is converted to the volume space of the distance field through the following [Equation 2], the point from the position where the point of the treatment tool shape model is converted to the volume space The value of the distance field is determined through Equation 3, and when the determined distance field value is negative, the treatment tool shape model may be provided to be considered to have collided with the bone shape model.

[Equation 2]

Where S _x is the location of the distance field in the local coordinate system where the distance field of the Healing Tool geometry model is located, P _x is the location of the point shell point in the world coordinate system, D _pos is the location of the distance field in the world coordinate system, D _size is the _size of the distance field (that is, the minimum position value of the voxel minus the maximum position value of the voxel), and D _num is the resolution of the distance field, so S _x is a value between 0 and D _num -1 Is determined.)

&Quot; (3) "

d = d ₀₀₀ * (1-x) (1-y) (1-z) + d ₀₀₁ * (1-x) (1-y) (z) + d ₀₁₀ * (1-x) (y) (1 -z) + d ₀₁₁ * (1-x) (y) (z) + d ₁₀₀ * (x) (1-y) (1-z) + d ₁₀₁ * (x) (1-y) (z) + d ₁₁₀ * (x) (y) (1-z) + d ₁₁₁ * (x) (y) (z)

(Where d is the distance field value at any location (x, y, z) of the point, d _000, d _001, d _010, d _011, d _100, d _101, d ₁₁₀ and d ₁₁₁ are any of the above Refers to the value of each distance field of eight adjacent voxels based on a point located at position (x, y, z).)

In addition, the contact force (F _c ) generated by the collision between the bone shape model and the treatment tool shape model may be provided to be calculated using Equation 4 below.

&Quot; (4) "

Where k _c is the stiffness, d _i is the value of the distance field at the location of the i point shell point that collided with the Healing Tool shape model, and N _i is the normal vector of the i point that collided (Normal) Vector).)

In addition, the reaction force is indirectly calculated by using a virtual coupling (Virtual Coupling), after calculating the position of the treatment tool shape model and the haptic device, respectively, and then the treatment tool shape as a virtual spring (Virtual Spring) After the model and the haptic device are connected to each other, the force (F _vc ) of the virtual coupling is calculated by using Equation 5 below, and the direction is the same as the force (F _vc ) of the virtual coupling. Computing a reaction force that is the opposite, the control unit may be provided to transmit an input signal having information on the reaction force to the haptic device.

[Equation 5]

(Where k _d is the stiffness of the virtual spring, P _d is the position of the haptic device, and P _t is the position of the therapeutic tool shape model.)

In addition, the position of the treatment tool shape model is displayed on the display unit may be provided to be calculated through the following [Equation 6].

&Quot; (6) "

는 x에 대한 접촉힘의 변화량,

는 x에 대한 가상 커플링 힘(F_vc)의 변화량을 의미한다.)(Where Δx is the displacement of the treatment tool shape model position,

Is the change in contact force with respect to x,

Is the amount of change in the virtual coupling force (F _vc ) with respect to x.)

In addition, the Δx is calculated by Gaussian elimination in the haptic cycle, and may be provided to calculate the position of the new treatment tool shape model by adding the Δx to the position of the current treatment tool shape model.

In addition, the control unit, by applying the following Equation (7) to the calculated reaction force to add the vibration information generated when using the actual treatment tool, the reaction force including the vibration force to the user through the haptic device It may be provided to be delivered.

 [Equation 7]

Where Fn represents the calculated reaction force, b represents the sine of a period of 100 and a magnitude of 0.15 at the current time t.

In addition, in performing the volume modeling of the bone shape model, by dividing the space in which the three-dimensional surface model of the bone shape model exists by voxelizing the shape of the bone, the numerical bone density obtained through the bone density imaging equipment By applying the information of to the voxelized model, it is possible to express the different stiffness in the bone in the state given the bone density property of the bone.

The bone density imaging apparatus may be any one of a CT (Computed Tomography) imager, a magnetic resonance imaging (MRI), and an X-ray imager.

According to the implant simulation system using the haptic interface according to the present invention, it is possible to acquire a physical and visual experience that is almost the same as the actual implant surgery experience without the actual implant treatment training, and the cost of implant treatment training such as expensive artificial teeth. Since the required materials are unnecessary, the economic utility value increases.

In addition, visual and physical data such as shape and stiffness of the affected patient's bone, such as damaged teeth and gum bones, are stored and output in the medical simulation system, and the haptic device provides the same force and feel as in actual implant surgery. The benefit is that you can get an implant treatment experience that is almost as real as it is.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

First, the configuration of an implant simulation system using a haptic interface according to the present invention will be described.

1 is a schematic diagram showing a configuration of an implant simulation system using a haptic interface according to the present invention, and FIG. 2 is a block diagram of an implant simulation system using a haptic interface showing a procedure of implementing a visual rendering technique and a haptic rendering technique.

As shown in FIG. 1, an implant simulation system using a haptic interface according to the present invention includes a haptic device 100, a display unit 200, and a controller 300.

The display unit 200 outputs a bone shape model 220 of the affected area that requires treatment and a treatment tool shape model 210 used to treat the affected area as a virtual image.

Here, the affected part refers to a part of the body that requires surgery or treatment related to teeth and gum bone during implant surgery, and the treatment tool is an implant medical tool used directly on the affected part when actually performing surgery or treatment on a patient. Means.

In addition, the embodiment of the present invention describes an implant surgery for treating teeth and gum bone as an example, the structure and operation of the implant simulation system using a haptic interface of the present invention by those skilled in the art to which the present invention pertains The principle can be applied to various medical procedures such as face, jaw and skull.

Therefore, the shape of the bone shape model 220 and the treatment tool shape model 210 is a matter of course depending on the affected shape and the shape of the medical tool in the various medical surgery to be applied.

The control unit 300 is connected to the electrical signal between the display unit 200 and the haptic device 100, the image is output on the display unit 200 according to the signal input from the haptic device 100 The shape and position information of the bone shape model 220 and the treatment tool shape model 210 are updated in real time, and the reaction force according to the collision between the bone shape model 220 and the treatment tool shape model 210 based on the volume model ( Feedback force) and transmits a signal having information on the calculated reaction force to the haptic device 100.

In addition, the control unit 300 receives the motion signal from the haptic device 100 and examines the collision between the bone shape model 220 and the treatment tool shape model 210 and when the collision is based on the reaction force information based on the volume model By performing a haptic rendering to calculate and performing a visual rendering to update the screen, by performing the deformation of the bone shape model 220 according to the position change of the treatment tool shape model 210 through the display unit 200 Output to video.

The haptic device 100 is a kind of force echo device for realizing the actual feeling of the treatment tool, and outputs a signal according to the mechanical displacement of the manipulation unit 110 and according to an input signal having information on the reaction force, the manipulation unit 110. ) Is displaced.

Here, the operation unit 110 indirectly changes the positional displacement of the treatment tool shape model 210 on the display unit 200 by directly operating a user by touching a finger or a palm which is a part of the body. The force or tactile force corresponding to the reaction force is generated so that the user can directly detect the reaction force generated by the collision between the treatment tool shape model 210 and the bone shape model 220.

In addition, when the manipulation unit 110 moves by a user's manipulation, the haptic device 100 converts the movement into an electrical signal and transmits the movement to the display unit 200 via the control unit 300, and the control unit 300. Receives the reaction force information calculated from) and transmits the force and the touch corresponding to the reaction force information to the user through the operation unit (110).

Next, the operation principle of an implant simulation system using the haptic interface according to the present invention will be described with reference to FIGS. 3A to 11.

Figure 3a is a schematic diagram of the bone shape model of the present invention represented by a three-dimensional surface model, Figure 3b is a schematic view of the bone shape model of the present invention represented by a volume model, Figure 3c is a schematic diagram of the bone shape model of the present invention represented by a point shell, 4A and 4B are schematic views showing a state where the treatment tool shape model and the bone shape model of the present invention collide with each other.

5 is a conceptual diagram showing eight arbitrary voxels around the arbitrary sampling point and surroundings thereof to determine the distance field value of any voxel of the present invention, and FIG. FIG. 7 is a schematic diagram illustrating a problem that occurs when a force field is directly calculated by applying a distance field of a treatment tool shape model, and FIG. 7 is a schematic diagram illustrating a concept of a reaction force calculation method using a virtual coupling of the present invention.

8A to 8C are schematic views showing a processing method of a volume cutting procedure according to an implant simulation system using a haptic interface of the present invention, and FIG. 9 is a simplified three-dimensional surface in an implant simulation system using a haptic interface of the present invention. Schematic diagram showing a state in which the bone shape model represented by the model is cut by the treatment tool shape model, Figure 10 is a force that is not applied to the reaction force generated by the collision of the treatment tool shape model and the bone shape model of the present invention Figure 11 is a graph showing the change in size, Figure 11 is a graph showing the change in the magnitude of the force applied to the vibration generated in response to the collision of the treatment tool shape model and the bone shape model.

In general, dental implant surgery involves implanting an artificial tooth into the alveolar bone (gum bone) in which the damaged tooth is extracted. It is a state-of-the-art dental surgery that restores the original function of teeth by fixing artificial teeth after planting in alveolar bone.

In order to apply the dental implant surgery to the implant simulation system using the haptic interface according to the present invention, as shown in FIG. 2 using the haptic device 100, the display unit 200 and the control unit 300, visual This can be implemented through the Visual Rendering technique and the Haptic Rendering technique.

Referring to FIG. 2, in order to calculate reaction force using the haptic rendering technique, first, when a user manipulates the operation unit 110 of the haptic device 100 and a mechanical displacement occurs in the haptic device 100, first The haptic interface pointer is tracked by obtaining the position and direction values of the haptic device 100, and the collision is detected with the bone shape model 220 according to the change in the position of the haptic interface pointer. The contact force is calculated and based on this, the virtual coupling force is calculated. The reaction force can then be calculated by calculating a new position of the treatment tool shape model 210.

In addition, in order to express the deformation of the bone shape model 220, and to calculate the reaction force due to the collision of the bone shape model 220 and the treatment tool shape model 210, and the three-dimensional surface model shown in Figure 3a Separately, internal representation model is essential.

The bone shape model 220 and the treatment tool shape model 210 separate and use a model for visual expression and a model for tactile generation. First, the visualization of the treatment tool shape model 210 uses a surface model commonly used in computer graphics, and the bone shape model 220 uses a volume model to represent deformation, and applies a regeneration algorithm to the surface. Create a model. As a result, the surface model is used to visualize the bone shape model 220 and the treatment tool shape model 210.

In addition, different expression models are used for the bone shape model 220 and the treatment tool shape model 210 to generate the tactile sensations, through which fast collision processing and sophisticated touch can be generated.

In addition, the bone shape model 220 is a point shell that surrounds the volume of the bone to generate the tactile sense. The treatment tool shape model 210 is a data obtained by calculating the shortest distance to the surface of the three-dimensional model in advance. It is characterized by using a distance field.

That is, in the present invention, the three-dimensional surface model shown in FIG. 3B is divided into discrete volume models represented by a set of voxel (Volume element), the point shell surrounding the bone surface shown in FIG. The same representation model applies.

Here, each voxel of the bone shape model 220 has a density property of the bone representing the degree of deformation of the bone, and each point of the point shell is individually a position value and a normal vector. Has properties.

In addition, the normal vector is used to calculate the reaction force and is calculated using the density values of the surrounding voxels at the positions of all points. For example, the value of the normal vector N in the index of the voxel called (i, j, k) may be calculated by Equation 1 below.

[Equation 1]

Here, the D (i, j, k) function is the density value of the voxel at position (i, j, k), Δx, Δy, and Δz are the distances (gaps) between the voxels on the x, y and z axes, respectively. it means.

The bone shape model 220 deformed by the treatment tool shape model 210 is an object having a volume composed of voxels, and each voxel has three properties of density, hardness, and Voxel type. It is used to show and visualize the residual amount of bone in each voxel.

In addition, the hardness property of each voxel is used to determine the magnitude of the reaction force, and the Voxel type represents the relationship between the volume model and the three-dimensional surface model, and differs depending on whether the voxel is inside, outside, or on the surface. A value is assigned and the Voxel type is used to estimate the surface of the bone when the point shell is deformed by bone drilling by the treatment tool shape model 210.

As described above, the algorithm of the haptic rendering technique according to the present invention uses a distance field in the treatment tool shape model 210 in addition to the three-dimensional surface model information for collision inspection and reaction force calculation. The distance field is data calculated in advance (before simulation) of the shortest distance to the surface of the 3D surface model within a range of a predetermined distance.

The method for generating the distance field is generated by dividing a given three-dimensional model into voxels and calculating the shortest distance from the location of each voxel to the surface. The distance field value uses signed floating point. If the value is 0, the surface is negative. If the surface is positive, the distance is positive.

4A and 4B, the distance field is generated at a high volume resolution only in the front portion of the treatment tool shape model 210 (the portion corresponding to the inside of the circle shown by the blue dotted line in FIGS. 4A and 4B).

In fact, since the treatment tool is in contact with the affected part (tooth and gum bone) is limited to the front part through this, the efficient and sophisticated collision treatment, through which the minute part of the treatment tool makes contact with the affected area.

For fast collision testing of bone geometry models and tools, the bounding sphere overlap test and volume-based collision test are performed in order. The bounding sphere refers to the smallest sphere that can contain a given treatment tool shape model 210, such as the blue dotted line circle shown in FIGS. 4A-4B, according to the movement of the treatment tool shape model 210. Update the location of the boundary sphere.

 In this case, the volume-based collision inspection is performed only when the boundary sphere collides with the bone shape model 220. The volume-based collision test is performed using the point shell of the bone shape model 220 and the distance field of the treatment tool shape model 210, and the bone shape model included in the boundary of the treatment tool shape model 210. Finding a point shell of 220, query the value of the distance field at the point and determine the sign to determine whether the bone shape model 220 and the treatment tool shape model 210 collides.

In this case, since the coordinate systems of the distance fields of the point shell and the treatment tool shape model 210 of the point shell of the bone shape model 220 are different from each other of the bone shape model 220 through Equation 2 below. Convert points to volume space in the distance field.

[Equation 2]

Where S _x is the location of the distance field in the local coordinate system where the distance field of the Healing Tool shape model is located, P _x is the location of the point shell point in the world coordinate system, D _pos is the location of the distance field in the world coordinate system, D _size is the _size of the distance field (ie, the minimum position value of the voxel minus the maximum position value of the voxel), and D _num denotes the resolution of the distance field. Therefore, S _x is determined to be a value between 0 and D _num -1.

Subsequently, a value of a distance field is determined using trilinear interpolation at a position where each point of the treatment tool shape model 210 is converted into volume space, that is, S _x .

For example, referring to FIG. 5, if the value of the distance field is d at any voxel position (x, y, z), the position (x, y, z) is expressed as shown in Equation 3 below. The distance values (d _000, d _001, d _000, d _011, d _100, d _101, d _110, and d ₁₁₁ ) of eight adjacent voxels are calculated by a weighted average of the current position. The value can be determined.

&Quot; (3) "

d = d ₀₀₀ * (1-x) (1-y) (1-z) + d ₀₀₁ * (1-x) (1-y) (z) + d ₀₁₀ * (1-x) (y) (1 -z) + d ₀₁₁ * (1-x) (y) (z) + d ₁₀₀ * (x) (1-y) (1-z) + d ₁₀₁ * (x) (1-y) (z) + d ₁₁₀ * (x) (y) (1-z) + d ₁₁₁ * (x) (y) (z)

Where d is a distance field value at an arbitrary position (x, y, z) of the point, d _000, d _001, d _010, d _011, d _100, d _101, d ₁₁₀ and d ₁₁₁ are arbitrary positions Refers to the distance field values of eight neighboring voxels based on a point located at (x, y, z).

Here, since a signed distance field is used for the treatment tool shape model 210, when the value of the distance field is negative, the treatment tool shape model 210 is connected to the bone shape model 220. It means that the collision.

In addition, when a collision between the bone shape model 220 and the treatment tool shape model 210 is detected, the contact force is calculated using Equation 4 below, and the contact force is the point of the point shell where the contact occurred. It is the sum of the contact forces.

&Quot; (4) "

Here, k _c is the stiffness, d _i is the value of the distance field obtained from the location of the i-point shell point collided with the treatment tool shape model, N _i is the normal vector of the i-point collided (Normal Vector) ).

In this case, when d and k values are extracted directly from the volume data, it is difficult to obtain continuous values because of the discrete nature of the volume data, which is solved by generating a smooth (continuous) value through the above-described triple interpolation.

On the other hand, Figure 6 is a schematic diagram showing a problem that occurs when the force is calculated directly using the point shell of the bone shape model 220 and the distance field of the treatment tool shape model 210.

Referring to FIG. 6, since a soft reaction force is obtained only when the treatment tool shape model 210 does not enter the bone shape model 220 (Shallow Penetration), the contact force may be directly transmitted to the haptic device 100. Can't.

More specifically, as shown in FIG. 6, when the treatment tool shape model 210 is in free space, no reaction force is generated (FIG. 6A).

However, the size of the distance field value obtained as the treatment tool shape model 210 moves inward and inward of the bone shape model 220 increases as compared with the previous value of FIG. 6 (a). 6 (b)-(c))

In addition, if the treatment tool shape model 210 is moved more deeply to the bone shape model 220, the point of the point shell will occur over the intermediate axis of the distance field of the treatment tool shape model 210, In this case, the increased reaction force is reduced again ((c)-(d) of FIG. 6).

Accordingly, when the front portion of the treatment tool shape model 210 in which the distance field is located completely passes the surface of the bone shape model 220, the collision between the treatment tool shape model 210 and the bone shape model 220 may be detected. It becomes impossible and reaction force is not generated. (FIG. 6D)

In addition, another problem that may occur when calculating the haptic feedback based on the volume model is that, depending on the number of point shells, the maximum expressive stiffness (stiffness) of the haptic device 100 may occur. Acquisition of reaction information may be unstable.

As described above, the front of the treatment tool shape model 210 is completely passed through the surface of the bone shape model 220, or virtually to solve the problem that occurs when the maximum expressive stiffness of the haptic device 100 The reaction force can be computed in an indirect way using the coupling (Virtual Coupling) technique.

The virtual coupling refers to virtually connecting the haptic device 100 and the treatment tool shape model 210 represented on the display 200.

More specifically, the virtual coupling (Virtual Coupling) separately calculates the position of the treatment tool shape model 210 and the haptic device 100, respectively, and the two are the virtual spring (Virtual Spring) Connect with

Therefore, as the position of the treatment tool shape model 210 and the haptic device 100 on the display unit 200 is spaced apart, the force of the virtual spring increases, and the force of the haptic device 100 is increased. Since it is transmitted to the operation unit 110, the user will feel a greater force or touch.

Here, FIG. 7 is a schematic diagram illustrating a concept of a reaction force calculation method using virtual coupling, and a treatment tool shown as a solid on the left side of FIG. 7 is a treatment tool shape model outputted on the display unit 200. The treatment tool shown in the image of 210, a wire frame shows the position and orientation of the haptic device 100 in the world coordinate system, and the hexagonal body formed by the points shown on the right side of FIG. Arbitrary image of the bone shape model 220.

As shown in FIG. 7, since the treatment tool shown as a solid is a treatment tool visible to the user, the treatment tool shown in the wire frame may not come into contact with or pass through the bone shape model 220. Since it is represented on the display unit 200 by reflecting the position, it may naturally contact or pass through the bone shape model 220.

As described above, the virtual coupling means connecting the two treatment tools to the virtual spring, and the user actually feels the force of the virtual spring generated according to the change of the position of the two treatment tools.

Therefore, in the implant simulation system using the haptic interface of the present invention, since reaction force is associated with the virtual spring force, it is possible to stabilize the unstable reaction force information by adjusting the virtual spring parameter.

First, in order to calculate the reaction force using the virtual coupling technique, the position of the treatment tool shape model 210 and the position of the haptic device 100 on the display are respectively calculated, and then, as a virtual spring. The treatment tool shape model 210 and the haptic device 100 are connected to each other. Here, the force Fvc of the virtual coupling may be defined by Equation 5 below.

[Equation 5]

Here, F _vc represents the force of the virtual coupling, k _d represents the stiffness of the virtual spring, P _d represents the position of the haptic device 200 and P _t represents the position of the treatment tool shape model 210.

In this case, k _d is determined in consideration of the maximum renderable stiffness that the haptic device 100 can express, and P _d is the size of the virtual space in which the tool moves the physical position of the haptic device 100. It is calculated by scaling to. In addition, P _t can be calculated by the above-described force equilibrium equation.

Next, a method of calculating the position of the treatment tool shape model 210 will be described.

When the sum of the contact force and the virtual coupling force is '0' (zero), since the force is in equilibrium, the position of the treatment tool shape model 210 is fixed in equilibrium.

However, when the user manipulates the operation unit 110 of the haptic device 100, the equilibrium state is broken. At this time, the treatment tool shape model 210 that is the object of the simulation is moved to a new position where the sum of the forces is '0'. This may be expressed as Equation 6 below.

&Quot; (6) "

는 x에 대한 접촉힘의 변화량을,

는 x에 대한 가상 커플링 힘(F_vc)의 변화량을 의미한다.Here, Δx is the displacement of the treatment tool shape model position,

Is the change in contact force with respect to x,

_Denotes the amount of change in the virtual coupling force F _vc relative to x.

In addition, Δx, that is, positional displacement of the treatment tool shape model 210, means a positional force (Positional force) to move the treatment tool shape model in order to maintain the equilibrium of the force.

In addition, through [Equation 6], x, y, z coordinates can be obtained a three-line equation (three linear equations), Δx can be calculated by the Gaussian elimination method in the haptic cycle.

More specifically, the above Denotes the change amount of the contact force when the treatment tool shape model 210 moves by x. This can be obtained by multiplying the distance field value by the change in the distance field value and the normal vector of the point shell.

는 x만큼 치료도구 형상모델(210)이 움직일 때 가상 커플 링의 힘의 변화량을 나타낸다. 따라서, 상기 [수학식 3]에서 알 수 있듯이 가상 커플링의 힘은 햅틱 사이클 동안에 햅틱장치의 위치(P_d)가 고정되어 있다고 한다면, -P_t에만 영향을 받고 P_t는 치료도구 형상모델의 변화량과 x의 변화량은 같으므로

는 -I(음의 단위행렬)가 된다.In addition,

Denotes the amount of change in the force of the virtual coupling when the treatment tool shape model 210 moves by x. Hence, the as it can be seen from the equation (3)] If there is a fixed location (P _d) of the haptic device during a power cycle of the virtual coupling is haptic, receiving only affect -P _t P _t is the treatment tool shape model Since the amount of change is equal to the amount of change in x

Becomes -I (negative unit matrix).

Thereafter, the position of the new treatment tool shape model 210 can be calculated by adding Δx to the position of the current treatment tool shape model 210.

That is, after calculating Δx by Gaussian elimination through Equation 6, adding _{Δx to} the position P _{t_old} of the previous treatment tool shape model 210 to maintain the equilibrium of force. The location of the treatment tool shape model (P _t ) can be obtained.

Here, the reaction force actually transmitted to the user is the force of the virtual coupling and since the position value P _d of the haptic device 100 has already been calculated, the force of the new virtual coupling (F _vc ) is obtained through Equation (5). Can be obtained.

Finally, by applying Newton's third law, the law of action reaction, the haptic device 100 transmits a signal outputting a force having the same size but the opposite direction as F _vc .

Then, the volume data of the bone shape model 220 is modified through the visual rendering technique based on the calculated reaction force information, and based on the modified volume information, the changed position of Voxel and its value are searched.

Here, when the treatment tool applied to the implant simulation system using the haptic interface of the present invention is a tool for deforming bone, such as a drill, it is preferable to reduce the density value of the volume collided with the treatment tool shape model 210. .

Therefore, the force and time required to deform the bone change according to the amount of decrease in density value, so it is necessary to accurately determine the decrease density value (BRR). According to the experimental results of applying the medical simulation system of the present invention, when the density value of the unmodified voxel is 100 unit, the bone shape model 220 is 7 msec in 1 msec by the treatment tool shape model 210. When the unit was removed, a strain rate similar to that of a drill (4 mm burr) used in actual implant surgery was obtained.

Then, recreate the Suface model for the changed part. Here, the Marching cube algorithm proposed by Lorensen in 1987 is used for surface model regeneration.

Here, the Marching cube algorithm is a typical algorithm used to polygonize volume data, and generates up to four triangles for a cuboid having eight vertices as vertices.

On the other hand, as the CPU of the system used in the implant simulation system using the haptic interface of the present invention, the Intel® Core ^TM CPU E8400@3.00 Ghz processor and the graphics card GeForce8800 GTS can be used, the haptic device 100 is SenantAble PHANTOM Premium 1.5 may be used, wherein the maximum force that the haptic device 100 can produce is 8.5 N and the maximum expressive rigidity is preferably 0.6 N / mm.

Here, the reaction force is equal to the new position of the treatment tool shape model 210 and the opposite force of the virtual coupling force (Virtual Coupling Force) between the haptic device 100, the most important point of the reaction force calculation is the haptic device 100 Consider the maximum force that can be exerted and the maximum expressive stiffness.

Therefore, if a large force that cannot be produced by the haptic device 100 is required, or if the haptic device 100 exerts a force beyond the expressible stiffness, the haptic device 100 may operate unstable. Therefore, in order to generate a stable reaction force, the magnitude of the reaction force should be limited to 8.5N or less and the rigidity of the virtual coupling to 0.6N / mm or less.

Here, the maximum expressive stiffness refers to the maximum amount of force that can be increased each time the haptic device 100 moves 1 mm. 0.6N / mm means that a stable force can be produced only by increasing the force to 0.6N or less each time the haptic device 100 is moved by 1mm.

Meanwhile, in the implant simulation system using the haptic interface of the present invention, the volume cutting process is performed every haptic cycle in order to handle the change in the shape of the bone shape model 220 while drilling the bone shape model 220 as the treatment tool shape model 210. Procedure is performed.

In the volume cutting procedure, first, the voxel of the bone shape model 220 that contacts the treatment tool shape model 210 using the distance field of the treatment tool shape model 210 and the volume data of the bone shape model 220. ), The property of density is subtracted by a certain value according to the speed of the drill in the found voxel.

In this case, the voxel type is updated to correspond to the density property of the bone shape model 220, and thus the points of the point shell are also removed and generated.

8A to 8C are schematic views illustrating a processing method of a volume cutting processing procedure according to an implant simulation system using a haptic interface of the present invention.

8A to 8B indicate the point of the point shell before cutting the bone shape model 220, and the point of the removed portion of the bone shape model 220 by the treatment tool shape model 210. The points of the shell are erased. In addition, the blue dot shown in Figs. 8A to 8C means the point of the new point shell generated.

As such, in order to fill the empty spots of the removed point shells, the boundary-fill algorithm is applied by using the voxel type attribute of the bone shape model 220.

9 is a schematic diagram showing a state in which the bone shape model 220, which is simplified and represented as a three-dimensional surface model in the implant simulation system using the haptic interface of the present invention, is cut by the treatment tool shape model 210. Referring to FIG.

Here, the resolution of the volume used in the bone shape model 220 is 48x48x48, the spacing between voxels is 0.05. In addition, the resolution of the volume used in the treatment tool shape model 210 is 32x64x32, Voxel size is 0.02.

Here, the resolution is a number indicating how many voxels are present in the X, Y, and Z axes, and the higher the resolution value is, the more precisely the model can be represented, and the distance field expressed in high resolution is treated. When applied to the shape model 210, it is possible to elaborate the collision process and even to generate a touch when the detail of the actual surgical tool (for example, the groove grooves in the surgical tool) touches the bone of the affected area.

Here, the numerical values (48x48x48, 32x64x32) relating to the resolution of the volume described above are resolutions required only for the specifications of the CPU and the graphics card of the PC applicable to the present invention described above, and are changed according to the specifications of the CPU and the graphics card. It should be understood that the resolution figures may be changed.

Here, in the specification of the CPU and the graphics card, the resolution of the volume of the bone shape model 220 is 48x48x48, the resolution of the volume of the treatment tool shape model 210 is reproducible from the volume model when using a resolution lower than 32x64x32 The shape of the bone shape model 220 is not smooth surface model can be coarse. Since a polygon is generated from the volume data using a polygonalization algorithm, if the regeneration algorithm is applied to a low resolution volume model, a surface model with a rough surface is generated.

In addition, when a volume having a low resolution is used in the distance field, not only accurate collision processing is performed but also discontinuous values are extracted when the value of the distance field is extracted, resulting in destabilization of reaction force.

In addition, the point of the point shell covering the whole of the bone shape model 220 is generated 2,958 points, the bone shape model 220 is a number of points generated or deleted by drilling, the maximum number of points is more than 4,500 This can be

Such haptic rendering and volume cutting procedures are handled within the range of 1 kHz, and visual rendering is preferably performed within the range of 60 Hz.

In this case, the visual rendering is performed at 60 Hz, which means 60 frames per second (rendering). Therefore, when the visual rendering speed is 60 Hz, the rapid rendering of the treatment tool shape model 210 is not missed. The state of the movement can also be expressed smoothly.

In addition, it is a number commonly used in the haptics community, and the speed of haptic rendering must be 1Khz or more so that the user can feel the touch of the actual object (therapeutic tool). If the speed of the haptic rendering falls below 1 kHz, the number of collision detection is reduced, which may cause the object to pass through, and the haptic device may become unstable.

On the other hand, in the present invention, by adding a fine vibration to the reaction force calculated by the virtual coupling is provided to more realistically reproduce the touch of the actual treatment tool.

To implement this, sample the value of the value in a sinusoid of 100 and a 0.15 magnitude rock period of 1 kHz, and add the calculated vibration force to the finally calculated y value of the feedback force. . This is defined by Equation 7 below.

[Equation 7]

Wherein the [Equation 7] and the like, the calculated reaction force is referred to as Fn, the cycle at the current time (t) 100 and calculates a value of b in the sinusoidal size of 0.15, haejumyeon more to F _n on the value vibration Applied reaction force can be obtained.

Here, Figure 10 is a graph showing the change in the magnitude of the force is not applied to the reaction force generated by the collision of the treatment tool shape model 210 and the bone shape model 220, Figure 11 is the treatment tool shape model (210) and the bone shape model 220 is a graph showing the magnitude change of the force applied vibration to the reaction force generated by the collision.

As shown in FIG. 10 and FIG. 11, by adding a fine vibration to the reaction force calculated by the virtual coupling it can be more realistic to realize the effect that the user can feel the touch of the actual treatment tool.

In addition, in the present invention, by applying virtual coupling to the voxel-based haptic rendering technique to generate a stable and smooth feedback force, the bone shape model 220 is drilled as a treatment tool shape model 210. While producing a smooth and stable feedback force.

On the other hand, in general, the bones of the human body is different depending on the site, but in most cases, the bone density of the internal than the outside of the bone shows a low state. This is common in the case of teeth, but in the case of actual implant surgery, when drilling a tooth or gum bone, the outside has a high bone density, which requires a strong force to press the treatment tool. As a result, drilling is possible even with a relatively small force.

Therefore, in the implant simulation system using the haptic interface according to the present invention, in performing the volume modeling of the bone shape model, bone density of the bone obtained using imaging equipment such as CT (Computed Tomography) or MRI (Magnetic Resonance Imaging) By applying the information to the volume modeling is provided so that the bone shape model 220 having a bone density property can be represented.

In order to implement this, first, the affected part is photographed with an imaging device such as CT or MRI to obtain information on the bone density of the bone of the affected part.

Here, in the image taken by CT or MRI, a portion having a high bone density appears bright according to a difference in bone density of a bone, and a portion having a relatively low bone density appears dark. That is, the higher the bone density, the closer to white, and the lower, the closer to black, the numerical value of the bone density of the bone can be obtained using the difference in brightness of the photographed image.

Therefore, by dividing the space where the 3D surface model exists discretely, the shape of the bone is voxelized, and by applying the information of the quantified bone density as described above to the voxelized model, the voxel model is used to determine the bone density. Attribute can be given.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

1 is a schematic diagram showing the configuration of an implant simulation system using a haptic interface of the present invention,

2 is a block diagram of an implant simulation system using a haptic interface showing a procedure of implementing the visual rendering technique and the haptic rendering technique of the present invention;

Figure 3a is a schematic representation of a three-dimensional surface model of the bone shape model of the present invention,

Figure 3b is a schematic representation of the bone shape model of the present invention as a volume model,

Figure 3c is a schematic representation of the bone shape model of the present invention in the distance field,

4A and 4B are schematic views showing a state in which a treatment tool shape model and a bone shape model collide with each other of the present invention;

5 is a conceptual diagram illustrating the arbitrary voxel and eight voxels in the vicinity thereof to determine the distance field value of the arbitrary voxel of the present invention;

6 is a schematic diagram showing a problem that occurs when the force is calculated directly using the distance field of the point shell and the treatment tool shape model of the bone shape model of the present invention,

7 is a schematic diagram showing the concept of a reaction force calculation method using a virtual coupling of the present invention,

8A to 8C are schematic views showing a processing method of a volume cutting processing procedure according to an implant simulation system using a haptic interface of the present invention;

9 is a schematic diagram showing a state in which a bone shape model represented by a three-dimensional surface model is simplified and cut by a treatment tool shape model in an implant simulation system using a haptic interface of the present invention;

10 is a graph showing a change in the magnitude of the force is not applied to the reaction force generated by the collision of the treatment tool shape model and the bone shape model of the present invention,

11 is a graph showing the change in the magnitude of the force applied to the vibration generated in response to the collision between the treatment tool shape model and the bone shape model.

<Explanation of symbols for the main parts of the drawings>

100 ... haptic device 110 ... control panel

200 Display unit 210 Treatment tool shape model

220 ... bone shape model 300 ... control unit

Claims (10)

A force or tactile echo device for realizing the actual feeling of a treatment tool, the apparatus comprising: a haptic device that outputs a signal according to a mechanical displacement of an operation unit and displaces the operation unit according to an input signal having information on feedback force; A display unit configured to output a virtual shape of the bone shape model of the affected area requiring treatment and the treatment tool shape model used to treat the affected area as a virtual image; The shape and position information of the bone shape model and the treatment tool shape model are output in real time on the display unit according to a signal input from the haptic device, and the bone shape model and the treatment tool shape model are based on a volume model. And a control unit which transmits a signal having information on the calculated reaction force to the haptic device by calculating the reaction force according to the collision of the haptic device. The method of claim 1, The collision test of the bone shape model and the treatment tool shape model is performed by applying a distance field of the point shell and the treatment tool shape model of the bone shape model, Extracting the point shell of the bone shape model included in the bounding sphere of the treatment tool shape model, querying the value of the distance field at the extracted point and determining the sign to determine the bone shape model and the treatment tool shape model Implant simulation system using a haptic interface, characterized in that for checking the collision of the. 3. The method of claim 2, The point shell included in the boundary of the treatment tool shape model is converted into the volume space of the distance field through Equation 2 below. The value of the distance field is determined by the following Equation 3 at the point where the point of the treatment tool shape model is converted to volume space, and when the determined distance field value is negative (-), the treatment tool shape model is Implant simulation system using a haptic interface, characterized in that the impact on the bone shape model. [Equation 2]

Where S _x is the location of the distance field in the local coordinate system where the distance field of the Healing Tool geometry model is located, P _x is the location of the point shell point in the world coordinate system, D _pos is the location of the distance field in the world coordinate system, D _size is the _size of the distance field (that is, the minimum position value of the voxel minus the maximum position value of the voxel), and D _num is the resolution of the distance field, so S _x is a value between 0 and D _num -1 Is determined.) &Quot; (3) &quot; d = d ₀₀₀ * (1-x) (1-y) (1-z) + d ₀₀₁ * (1-x) (1-y) (z) + d ₀₁₀ * (1-x) (y) (1 -z) + d ₀₁₁ * (1- x) (y) (z) + d ₁₀₀ * (x) (1-y) (1-z) + d ₁₀₁ * (x) (1-y) (z) + d ₁₁₀ * (x) (y) (1-z) + d ₁₁₁ * (x) (y) (z) (Where d is the distance field value at any location (x, y, z) of the point, d _000, d _001, d _010, d _011, d _100, d _101, d ₁₁₀ and d ₁₁₁ are any of the above Refers to the value of each distance field of eight adjacent voxels based on a point located at position (x, y, z).) The method of claim 3, wherein The contact force (F _c ) generated by the collision between the bone shape model and the treatment tool shape model, Implant simulation system using a haptic interface, characterized in that calculated using [Equation 4] below. &Quot; (4) &quot;

Where k _c is the stiffness, d _i is the value of the distance field at the location of the i point shell point that collided with the Healing Tool shape model, and N _i is the normal vector of the i point that collided (Normal) Vector).) The method of claim 4, wherein The reaction force is calculated indirectly by using virtual coupling (Virtual Coupling), After calculating the position of the treatment tool shape model and the haptic device respectively, connecting the treatment tool shape model and the haptic device with a virtual spring and then using Equation 5 below. Compute the force (F _vc ) of the virtual coupling to calculate the reaction force of the same magnitude but the opposite direction of the force (F _vc ) of the virtual coupling, The control unit, the implant simulation system using a haptic interface, characterized in that for transmitting the input signal having the information on the reaction force to the haptic device. [Equation 5]

(Where k _d is the stiffness of the virtual spring, P _d is the position of the haptic device, and P _t is the position of the therapeutic tool shape model.) The method of claim 5, Implant simulation system using a haptic interface, characterized in that the position of the treatment tool shape model output on the display unit can be calculated through the following Equation (6). &Quot; (6) &quot;

(Where Δx is the displacement of the treatment tool shape model position,

Is the change in contact force with respect to x,

Is the amount of change in the virtual coupling force (F _vc ) with respect to x.) The method of claim 6, Δx is calculated by Gaussian elimination in the haptic cycle, Implant system using a haptic interface, characterized in that the position of the new treatment tool shape model can be calculated by adding the Δx to the position of the current treatment tool shape model. The method of claim 5, wherein the control unit, In addition to the calculated reaction force, by applying Equation 7 below, vibration information generated when using a real treatment tool is added, and a reaction force including vibration force is transmitted to the user through the haptic device. Implant simulation system using a haptic interface.  [Equation 7]

Where Fn represents the calculated reaction force, b represents the sine of a period of 100 and a magnitude of 0.15 at the current time t. The method of claim 1, In performing the volume modeling of the bone shape model, By dividing the space where the three-dimensional surface model of the bone shape model exists discretely, the shape of the bone is voxelized, and by applying the numerical information of the bone density obtained through the bone density imaging equipment to the voxelized model, An implant simulation system using a haptic interface, characterized in that the bone shape model is volume modeled with a bone density property. The method of claim 9, wherein the bone density imaging equipment, Implant simulation system using a haptic interface, characterized in that any one of the CT (Computed Tomography), MRI (Magnetic Resonance Imaginger) and X-Ray imager.

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