JPS62227320A - Stereoscopic image display apparatus - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a stereoscopic image display device that processes three-dimensional Voxe I data of a human body image produced by a medical tomographic 1fi imaging device and performs reprojection display.

[Technical Background of the Invention and Problems Therewith] In recent years, various CT apparatuses that display images of the inside of a human body in the form of tomographic images have appeared in the field of medical image diagnostic equipment.

Examples include an XNQ CT device that uses X-rays, an emission CT device that uses radioisotopes, an MR-CT device that uses nuclear magnetic resonance development, and an ultrasonic CT device that uses ultrasound.

When a doctor makes a diagnosis using these various CT devices,
Usually, multiple tomographic images covering the tumor area are imaged instead of one tomographic image.

Doctors look at these multiple tomographic images and, in their minds, reconstruct the three-dimensional structure inside the human body based on their anatomical knowledge.
It is diagnosing.

From the above, it can be understood that stereoscopic image display of the three-dimensional structure inside the human body is extremely useful for doctors' diagnosis.

Conventionally, various methods regarding three-dimensional display of multi-layered layers have been proposed.

For example, a coordinate conversion device, an interpolation process 1 and a contour extraction device for image data obtained by a CT device.

There is a method of image display (hereinafter referred to as "pseudo 3D display") that performs contour surface merging processing, hidden surface removal ffi embedding, etc. (Takami Yasuda et al., Simulation of external oblique surgery using 3D display of a CT image of the head) ”, Proceedings of the 23rd MF Academic Association,
P750-P751. APR, 1984).

However, in this method, the image data processing process is complicated, and large-scale and enormous hardware is required if high-speed display is to be performed.

Furthermore, even if current image processing methods are used, it is not always possible to expect stable operation for extracting the contours of organs, so there are cases where the image data of the base tomogram must be manually input, and it is not automatic. There is a problem.

A stereoscopic display method using a reprojection method has also been proposed.

This method uses three-dimensional Vox obtained from a CT multilayer surface.
cl (Volume element) is integrated in the line of sight direction to reconstruct the projected image and perform stereo display (Shigeki Yokoi et al., ``3
"Survey on dimensional representation", Information Processing Society of Japan, Computer Vision, 18-5.1982゜5.20, L.
[), l1arris, [Identificatio
or the Optimal Orientati
on of 0blique 5ections
ough Multiple Parallels
C Ding ImageJ.

Journal of Computer As5is
ted'romography, Vo15, No.
6.1981, L, D, 1Iarris, 1-D
iSpray and Visualization o
f Three-DimmcnsionalReco
structured Anatomic Morpho
logic: Experience with the T
horax, Hert, and CoronaryVa
sculatrue of Dogs J, Jou
rnal of ComputerAssisted
Tomography, Vol 3. No, 4.1
979).

However, when the X-ray CTi1iii image is reprojected and displayed, there is a problem in that organs located in front and behind the mother or air become invisible due to the following reasons.

Namely, the known publication (Illustrated Computed Tomography; 197
According to Shujunsha (published on January 10, 1999), Figure 5 (A),
As shown in (B), the CT value of each part of the human body can be recognized. According to the same figure, the mother's CT value is
The CT value of air is extremely large in the positive direction compared to soft tissue (including fat), and the CT value of air is extremely large in the negative direction compared to soft tissue. That is, as shown in the figure, the CT values of soft tissues are concentrated in the range of -50 to +50, whereas the CT values of bones are around +500, and the CT values of air are around -50.
It is about 00. In addition, the definition of CT value differs depending on the mechanical force, and the CT value of soft tissue is ±100°, the CT value of bone is +1000, and the CT value of air is -1000, but the CT value of soft tissue is There is no difference in the fact that the CT values of bones and air have large values in the positive and negative directions, respectively.

From the above, if we combine the display window level and window width (a window is a type of look-up table) with the brightness level that makes it easier for soft tissues to develop, we can see that organs that overlap in front and behind bones and air Due to the presence of bones, etc., the brightness of
saturation) and become invisible. This situation is shown in Figure 6. The same figure (A> is a schematic diagram of a cross section of the abdomen including bones, and the same figure (B) is the profile of the reprojected image in the y direction of the same figure (A) and this is adjusted to fit the soft tissue. This shows the result of window-converting the brightness.As shown in the same figure (B), if you look at the profile after window-converting the window level l and window width W based on the brightness level of the soft tissue, you can see that the bone and its front and back The brightness corresponding to the area is saturated (it becomes completely black on the monitor). Therefore, even if there is soft tissue in front and behind the bone, this soft tissue cannot be displayed during stereoscopic viewing. ,
The above also applies to organs (bones and intestines) that contain air, as shown in Figure 7 (A>), and as shown in Figure 7 (8), they correspond to air and the parts before and after it. The brightness is at the lowest level of the dynamic range, resulting in pure white on the monitor.

Therefore, the soft tissue in front of and behind the air cannot be displayed in the stereoscopic image.

Purpose of the Invention 1 The present invention has been made in view of the above circumstances, and there are parts of sea urchin that have large CT values in the positive and negative directions compared to the CT value of sea urchin soft tissue. Even if
It is an object of the present invention to provide a stereoscopic image display device capable of displaying soft tissue before and behind the soft tissue in a stereoscopic image gallery.

[Summary of the Invention] The outline of the present invention for achieving the above object is to provide an image storage unit that stores both CT images collected for a plurality of slice planes, and a unidirectional image storage unit based on a plurality of CT images from this image storage unit. In a three-dimensional image display device that includes a reprojection calculation unit that creates a reprojection image projected on the image, and a display unit that displays the reprojection image, data from the image storage unit is input, and the CT value of the soft tissue is releveled. The present invention is characterized in that a level conversion means is provided for level converting a CT value that is outside the range to a CT value that is close to the CT value relevel of the soft tissue.

[Embodiments of the Invention] The present invention will be described below with reference to illustrated embodiments. 1st
The figure is a block diagram of the device of this embodiment.

- A first three-dimensional memory 1 which is a rotational storage section in the same figure.
stores tomographic images of multiple slice planes collected by an X-ray CT device (not shown). 8 out of 1 of this 3D menu (
The CT value of each voxel is input to the subsequent level conversion block 10, the details of which will be described later. It is designed to be output as follows. The second three-dimensional memory 11 includes the level conversion block C1
It stores the output of 0. The reprojection calculation unit 12
Based on the contents of the second three-dimensional memory 11, calculations for reprojection are executed to create a reprojected image. This reprojection calculation is basically an integral calculation of the CT value in the projection direction, and various known calculations can be adopted, but as an example of performing this calculation at high speed, the applicant previously proposed Image reconstruction device using Fourier transform (patent application 1986)
-198513tan) can also be used. The reprojected image is then displayed on the display unit 13 and used for medical diagnosis.

Next, details of the level conversion block 10 will be explained.

In FIG. 1, this level conversion block 10 converts the output of the first three-dimensional memory 1 into the second three-dimensional memory 1.
3 image transfer routes A, B, C for inputting to 1.
have. Then, each image transfer route A, B,
Gates 1 to 7, 8, and 9 are respectively provided in C, and only the - gate is opened at a predetermined timing as will be described later, and data is input to the second three-dimensional memory 11. . The image transfer routes B and C include an f(x) function conversion unit 2. g(X) function conversion units 3 are arranged respectively. During this period f (X)
, (J(X) - Examples are shown in FIGS. 2(A) and 2(B).

In both figures, X is the original CT value output from the first three-dimensional memory 1, and y is the level-converted CT value. In both figures, X and y have a 1:1 relationship at the soft tissue level (for example, a CT value of -50 to +50), that is, the output of the first three-dimensional memory 1 is transferred as is. . CT values in this level range are output via the image transfer route A and gate 7. On the other hand, the CT value that has a larger value in the positive direction than the above soft tissue level is
The level is converted by the function f(x), and the level is converted to a level close to that of soft tissue regardless of the size of the original CT value. C in this range
The T value is outputted via the image transfer rules 1 to B, that is, the ↑゛(×) function conversion unit 2 and the gate 8. Roughly speaking, a CT value having a value greater in the negative direction than the soft tissue level is level-converted by the function q(X), and similarly converted to a CT value close to the soft tissue level. The CT values in this range are output via the image transfer route C, that is, the g(X) function converter 3 and the gate 9.

To achieve the level conversion described above, the gates 7.8.9 are connected to the first . Opening/closing is controlled by the second comparator 4.5 and the NOR gate circuit 6. The first comparator 4 has the mother CT value (level a shown in FIG. 2 (A>, (B)) as a threshold value, and compares it with the CT value from the first three-dimensional memory 1. If it is larger than the darkness value, it outputs "1", and if it is smaller than the threshold value, it outputs rOJ. On the other hand, the second comparator 5 uses the CT value of air (Fig. 2 (^)) as the threshold value.

(B) has the level b shown in the figure), and if it is smaller than the threshold value when compared with the CT value from the first three-dimensional element
1" is output, and if it is larger than the threshold value, "O" is output. The NOR gate circuit 6 is connected to the first . Second comparator 4
, 5 are output by two people, and "1" is output only when Ryokawa Riki is rOJ, and "0" is output otherwise. The gate 7 has an output of 1 from the NOR gate circuit 6.
It is opened when the goo (-8 is the output of the first comparator 4) is "1", and the goo1 is opened when the goo is "1".
-0 is opened when the output of the second comparator 5 is "1".

The operation of the device configured as above will be explained.

The data read out from the first three-dimensional memory 1 is transferred to each group 1 to 7.8 through the image transfer routes A, B, and C.
Guided by 9. Here, in image transfer route A, the original data is directly guided to gate 7, in image transfer route B, the original data X is level-converted using the function f(x) and guided to gate 8, and in image transfer route C, original data The level is converted using the function g(X) and the signal is led to gate 9.

On the other hand, the original data X from the first three-dimensional memory 1 is
1st. The signal is also input to second comparators 4 and 5. And this first one. The opening and closing of each of the gates 7, 8, and 9 is controlled based on the comparator horns from the second comparators 4 and 5 and the output of a NOR gate circuit 6 which uses the comparison output as a two-man power source.

That is, when the original data X is within the range of the soft tissue level, the first. The outputs of the second comparators 4 and 5 are both rOJ, and therefore the output of the NOR gate circuit 6 becomes "1", so the gate 7 is opened and the original data X is output as is through this gate 7. Become.

When the original data X is larger than the soft tissue level X (that is, when it is the bone level in FIG.
1-1" is output from the gate 8, and the gate 8 is opened. Data whose level has been converted by the function f(x) is output through the gate 8.

If the original data X is smaller than the soft tissue level Data whose level has been converted by the function Q(X) is outputted through the gate 9.

In this way, the CT value that is outside the soft tissue level can be expressed by the function f
(x) and function (IX) are respectively converted to CT values close to the soft tissue level. Thereafter, the reprojection calculation is performed in the same manner as in the past, and the reprojected image is displayed on the display device 13.

The profile of the reprojected image when the above level conversion is performed is shown in FIGS. 3A and 3B.

Figures 3 (A> and (B) are respectively Figure 6 (A)).

FIG. 7 shows the profile of a reprojected image when the tomographic image model shown in A> is projected in the y direction.

In Figure 3 (A), the brightness level of the bone has been lowered, so the soft tissue profile in front and behind the bone also appears at a sufficiently child-friendly level. On the other hand, in Figure 3 (B), the Because the brightness level has been increased, the soft tissue profile in front and behind the air region also appears at a sufficiently visible level.

As a result, it is possible to display even soft tissue overlapping bones and air in a 3D image, and in particular, it is possible to display 3D images of organs such as the abdomen containing bones or the stomach and intestines containing air with sufficiently high diagnostic ability. It can be displayed as

Note that the present invention is not limited to the above embodiments, and various modifications can be made within the scope of the gist of the present invention. For example, as an example of the level conversion means, in the above embodiment, bones,
The CT value of the air level is compared as a threshold value, and the level conversion output is selected based on the comparison result, but instead of the level conversion block 10, a level change 4%-y-bull memory 20 shown in FIG. 4 is used. may also be used. The memory 20 shown in the figure stores functions not shown in FIG. 2 (A> or FIG. 2 <8) as data. When the CT value X of the original image is input from the address input terminal of this memory 20, the value on the horizontal axis in FIGS. 2(A) and (B) is specified,
If the configuration is such that the corresponding vertical axis value (function value) is output from the output end of the memory 20, level conversion exactly the same as in the above embodiment can be realized.

Note that it is not impossible to perform such level conversion before displaying on the display unit 13. However, in this case, the thickness of the bone and air in the projection direction must be taken into consideration, so that a simple level conversion as in the present invention is not possible.

[Effects of the Invention] As detailed above, according to the present invention, even if there is a region such as mother, air, etc. that has a CT value larger in the positive or negative direction than the CT value of soft tissue, It is possible to provide a stereoscopic image display device that can display soft tissue before and behind the soft tissue in a stereoscopic image.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 (
A) and (B) are characteristic diagrams showing examples of conversion functions for level conversion, respectively, and FIG. 3 (A). (B) is a characteristic diagram showing the profile of the y-direction projection record obtained by the same apparatus, FIG. 4 is a schematic explanatory diagram showing a modification of the level converting means, and FIG. 5 (A). (B) is a characteristic diagram that does not show the CT values of each part of the human body, Figure 6 (
A) is a schematic diagram of a cross-section of the abdomen including bones, and Figure 6 (B) is the profile of the reprojected image in the y direction of the same figure (A) and the result of window-converting the brightness by fitting it to the soft tissue. Figure 7 (A> is a schematic diagram of a cross-section of an organ containing air, Figure 7 (B) is a profile of the reprojected image in the y direction of Figure (A) and its projection into soft tissue. It is a diagram showing the result of window-converting the luminance with V. 1... Image storage unit, 10. 20... Level conversion means, 12... Image reconstruction unit, 13... Display unit. Agent Patent Attorney Nori Chika Udo
Person Hu Dianfu (A) (B) Figure 2 (A) (B) Figure 3 Figure 4 (A) Figure 5 (A) Figure 6

Claims (1)

[Claims] an image storage unit that stores CT images collected for a plurality of slice planes; a reprojection calculation unit that creates a reprojection image projected in one direction based on the plurality of CT images from the image storage unit; A stereoscopic image display device comprising a display unit that inputs data from the image storage unit and converts CT values that are outside the CT value level of soft tissue into CT values that are close to the CT value level of the soft tissue. A stereoscopic image display device comprising a level conversion means for converting a level into a value.