JPH03276265A - Tomographic image processor - Google Patents

Abstract

PURPOSE:To satisfactorily decrease the flowing images with the image time held as it is by simulating the flowing image emerging in the image of a 1st fault face with use of the image data on another fault face parallel to the desired 1st fault face. CONSTITUTION:The flowing image emerging in an image 3 of a 1st fault face is simulated to obtain an image. Then the 2nd image data SB showing the simulated image is obtained based on the image data S1, etc., except the 1st image data S3 showing the image 3 of the desired 1st fault face out of those image data S1 - S5 showing the images 1 - 5 of fault faces respectively. Then the 3rd image data SR showing an image where the flowing images are decreased or eliminated is obtained based on the data SB and the data S3. Thus the flowing images are decreased or eliminated with the effective image information held as it is.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a tomographic image processing apparatus that performs image processing to reduce or eliminate flow images appearing in tomographic images obtained by tomographic imaging.

(Prior Art) It is practiced in various fields to read a recorded radiation image to obtain image data, perform appropriate image processing on this image data, and then reproduce and record the image. For example, an X-ray image is recorded using an X-ray film with a low gamma value designed to be compatible with later image processing, and the X-ray image is read from the film on which it is recorded and converted into an electrical signal. By performing image processing on this electrical signal (image data) and then reproducing it as a visible image in a copy photograph, etc., it is possible to obtain a reproduced image with good image quality performance such as contrast, sharpness, and graininess. A system has been developed (see Japanese Patent Publication No. 61-5193).

In addition, the applicant has proposed radiation (X-rays, α-rays).

When irradiated with β rays, γ rays, electron beams, ultraviolet rays, etc., a part of this radiation energy is accumulated, and then when irradiated with excitation light such as visible light, stimulable fluorescence exhibits stimulated luminescence depending on the accumulated energy. A radiation image of a subject such as a human body is photographed and recorded on a sheet of stimulable phosphor using a stimulable phosphor, and this stimulable phosphor sheet is scanned with excitation light such as a laser beam. The resulting stimulated luminescent light is read photoelectrically to obtain image data, and based on this image data, a radiation image of the subject can be recorded on a recording material such as a photographic light-sensitive material, a CRT, etc. Radiation image recording and reproducing systems that output visual images have already been proposed (Japanese Patent Application Laid-open Nos. 55-12429, 58-11395, 55-
No. 163472, No. 56-104845, No. 55-1
16340 etc.).

This system has the practical advantage of being able to record images over a much wider range of radiation exposures than conventional radiographic systems using silver halide photography. In other words, in a stimulable phosphor, it is recognized that the amount of emitted light that is stimulated to emit light due to excitation after accumulation is proportional to the amount of radiation exposure over an extremely wide range.
Therefore, even if the amount of radiation exposure varies considerably due to various imaging conditions, the amount of stimulated luminescence emitted from the stimulable phosphor sheet can be read by the photoelectric conversion means by setting the reading gain to an appropriate value. By converting the radiation image into an electric signal and using this electric signal to output the radiation image as a visible image to a recording material such as a photographic light-sensitive material or a display device such as a CRT, a radiation image that is not affected by fluctuations in radiation exposure amount can be obtained. be able to.

By the way, one of the methods of photographing and recording a radiation image of a subject on a recording sheet is a method called tomography (for example, see Japanese Patent Laid-Open No. 58-67245).

In tomography, for example, the subject is fixed, a fulcrum is placed on a plane parallel to the target cross-section inside the subject, and the radiation source and recording sheet are simultaneously moved in opposite directions to achieve the target. By ensuring that the parts on the tomographic plane are photographed at the same position on the recording sheet, the images of the parts above and below the tomographic plane are erased and the part on the tomographic plane is photographed and recorded as a clear image. This is the way to do it. Various methods are used to move the radiation source and recording sheet, and one of the main methods is to move the radiation source in a straight line so that the image above and below the tomographic plane is blurred only in one predetermined direction. There is a linear tomography method that performs tomography using
There are also ways to take pictures by moving in a circle, ellipse, hypocycloid, or spiral.

(Problems to be Solved by the Invention) Radiographic transmission that exists in the central region to be observed in a radiographic image (tomographic image) obtained using this tomography method, other than the tomographic plane targeted for imaging. The image of the portion where the amount has changed significantly is the obstruction shadow (hereinafter referred to as the "flow image") along the above movement direction (in the case of linear tomography, it is one straight direction (hereinafter referred to as the "left-right direction")). ), and this flow image makes the image difficult to observe, or the object corresponding to this flow image may be mistakenly recognized as if it actually existed on the tomographic plane being photographed. There were times when I ended up.

Conventionally, the method described below is known as a method for reducing this flow image (Proceedings of the 41st General Meeting of the Japanese Society of Radiological Technology, 1985, pp. 168-169, "Elimination of Obstacle Shadows in Straight Tomography Images", Fukui Medical Science, Japan. (Detection et al., Department of Radiology, University Hospital).

This method targets straight tomography images, and since the flow image extends in one direction, left and right, the low spatial frequency in this left and right direction is used to represent the image of the tomographic plane targeted for imaging. Moving average the image data in the horizontal direction of the image, generating averaged image data that carries only the low spatial frequency components of the image in the horizontal direction, and subtracting this averaged image data from the above image data. This method generates an image in which low spatial frequency components corresponding to a flow image are relatively reduced.

Although this method has succeeded in reducing the flow image to some extent, the degree of reduction of the flow image is not sufficient, and the amount of useful information that has spatial frequency components approximately the same as that of the flow image is insufficient to reduce the flow image. There is a problem that image information is also lost.

In view of the above problems, the present invention provides a function that can sufficiently reduce the flow image while retaining this image information even when useful image information has a spatial frequency component comparable to that of the flow image. An object of the present invention is to provide a tomographic image processing apparatus equipped with the following.

(Means for Solving the Problems) The tomography image processing apparatus of the present invention provides: of a plurality of image data representing images of a plurality of parallel and different tomographic planes of a subject obtained by tomography, An image that simulates a flow image appearing in an image carried by the first image data, based on one or more image data other than the first image data representing the image of the desired first tomographic plane. flow image simulating means for obtaining second image data representing the flow image; and third image data representing an image in which the flow image has been reduced or removed based on the first image data and the second image data. The present invention is characterized by comprising a flow image removing means for determining the flow image.

Here, in the tomographic image processing apparatus, by performing interpolation calculation based on the plurality of image data,
an interpolation calculation means for obtaining one or more interpolated image data simulating an image of a new tomographic plane sandwiched between the two mutually adjacent tomographic planes; Preferably, the second image data is determined using the interpolated image data.

(Function) The present invention simulates the flow image appearing in the image of the first tomographic plane using image data of another tomographic plane parallel to the desired first tomographic plane, and The basic idea is to subtract the simulated flow image from the actual flow image that appears in the tomographic plane image.

That is, the tomographic image processing apparatus of the present invention processes the first image data based on one or more image data other than the first image data representing the image of the desired first tomographic plane. flow image simulating means for obtaining second image data representing an image simulating a flow image appearing in an image carried by the image; and a flow image simulating means for reducing the flow image based on the first image data and the second image data. Alternatively, since it is equipped with a flow image removal means for obtaining third image data representing the removed image, image information other than the flow image is saved even if it has a spatial frequency component comparable to that of the flow image. The flow image can be reduced or eliminated while the flow image remains unchanged.

Further, one or more interpolated image data simulating an image of a new tomographic plane are obtained based on the plurality of image data, and one or more interpolated image data are used together with the other image data to generate the second image. By determining this, it becomes possible to reduce or remove only the flow image with higher precision.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Here, a system using the above-mentioned stimulable phosphor sheet will be explained.

FIG. 1 is a diagram schematically showing an example of a linear tomography apparatus.

The X-ray source 6 moves in the direction of arrow A shown in the figure.

In addition, an X-ray source 6 is placed between the subject (here, the head of a human body) 8.
Five stimulable phosphor sheets stacked in positions facing 1. 2. 3.4. 5 moves in the direction of arrow B in synchronization with the movement of the X-ray source 6 while remaining stacked. This X-ray source 6 and the stimulable phosphor sheet 1. 2. 3.4
．． X-rays 7 are emitted from the X-ray source 6 many times during the movement of the stimulable phosphor sheet 1. 2. 3. Photographing was carried out multiple times at 4°5, and each stimulable phosphor sheet 1. 2. 3.4. 5
X-ray tomography images are accumulated and recorded. Here, the stimulable phosphor sheets 1 and 2.3.4.5 are placed at different distances from the X-ray source 6 and the subject 8 by the thickness of one stimulable phosphor sheet, so each stimulable Phosphor sheet 1. 2. 3.4. 5, tomographic images of mutually different tomographic planes 10, 11, 12, 13, and 14 of the subject 8 are accumulated and recorded.

FIG. 2 is a diagram schematically showing an example of a tomographic image obtained as described above.

Five stimulable phosphor sheets shown in FIG. 1, 2゜3.
4.5, a tomographic image 8' corresponding to the tomographic plane of the subject 8 is recorded approximately at the center of the center sheet 3, for example. Flow images 9 are formed at both the left and right corners of this image 8', but since the object of observation is near the center of the image 8', these flow images 9 at both corners do not pose a particular problem. However, near the center of the image 8', as shown in the figure, there is a flow image 15 extending left and right (directions corresponding to the moving directions of the X-ray source 6 and the sheets 1, 2, 3, 4, and 5 shown in Fig. 1). is mixed in. Since this flow image 15 appears within the observation area of the image 8', it is a flow image that needs to be removed.

FIG. 3 is a perspective view showing an example of an X-ray image reading device and a computer system including an embodiment of the tomographic image processing device of the present invention.

An X-ray image reading device 20 for each of the five stimulable phosphor sheets 1, 2, 3, 4, and 5 on which X-ray tomography images have been recorded.
is set in the specified position. Here, the description will be made assuming that the stimulable phosphor sheet 1 is set. The stimulable phosphor sheet 1 set at a predetermined position is transported by a sheet conveying means 2 such as an endless belt driven by a motor 21.
2, it is transported (sub-scanning) in the direction of arrow Y. on the other hand,
The excitation light beam 24 emitted from the laser light source 23 is reflected and deflected by a rotating polygon mirror 26 that is driven by a motor 25 and rotates at high speed in the direction of the arrow, passes through a focusing lens 27 such as an fθ lens, and then changes its optical path by a mirror 28. The light enters the stimulable phosphor sheet 1 and performs main scanning in the direction of arrow X, which is substantially perpendicular to the direction of sub-scanning (direction of arrow Y). From the part of the stimulable phosphor sheet 1 irradiated with the excitation light 24, stimulated luminescence light 2 is emitted in an amount corresponding to the accumulated and recorded X-ray image information.
9 is emitted, and this stimulated luminescence light 29 is guided by a light guide 30 and then passed through a photomultiplier (photomultiplier tube).
31 photoelectrically detected. The light guide 30 is made by molding a light-guiding material such as an acrylic plate, and is arranged so that the linear entrance end surface 30a extends along the main scanning line on the stimulable phosphor sheet 1. A photomultiplier 31 is mounted on the injection end surface 30b formed in an annular shape.
The light-receiving surfaces of the two are combined. The stimulated luminescent light 29 that has entered the light guide 30 from the incident end surface 30a is transmitted through the light guide 30.
The stimulated luminescent light 29 that travels through the interior of the camera through repeated total reflection, exits from the exit end face 30b and is received by the photomultiplier 31, and the stimulated luminescence light 29 representing an X-ray image is sent to the photomultiplier 31.
is converted into an electrical signal by

The analog output signal SA output from the photomultiplier 31 is logarithmically amplified by the logarithmic amplifier 32, and the A/D
The image data is digitized by a converter 33 to obtain image data as a digital signal. This image data is image data representing an X-ray tomography image stored and recorded on the stimulable phosphor sheet 1, and this image data will be referred to as Sl.

The obtained image data S1 is stored in the computer system 40.
is input. This computer system 40 has a configuration that includes an example of the tomographic image processing apparatus of the present invention, and includes a main body section 41. A drive section 42 into which a floppy disk as auxiliary memory is inserted and driven. It is comprised of a keyboard 43 for an operator to input necessary instructions to the computer system 40, and a CRT display 44 for displaying necessary information.

In the same manner as above, other stimulable phosphor sheets 2゜3.4.
5 are also read, and each image data s2. s3.
s, , S5 are obtained and input into the computer system 40.

FIG. 4 is a diagram showing the flow of processing in the computer system 40.

Here, the image data “1 + 52 * S3,
S4.

The X-ray tomography images carried by S are referred to as image 1, image 22, image 35, image 41, and image 5, respectively.

Furthermore, here, image data S3 is first image data representing an image of a desired first tomographic plane (tomographic plane 12 shown in FIG. 1) according to the present invention, that is, image 3 is an image to be observed. Therefore, here we will show the flow image 15 that appears in this image 3.
(See Figure 2).

Here, first, two image data S1. Calculation is performed according to equation 3 (1) for each pixel that corresponds to each other based on SZ, and these two image data S1
．． Interpolated image data S1□ is obtained that simulates an image of an intermediate tomographic plane between two tomographic planes corresponding to Sz. Similarly, calculations are performed according to each equation 3 (2) (3) (4), and the interpolated image data S23゜S
34+S 45 is found. In this embodiment, the interpolated image data S1□+S23+S34 is generated in accordance with the above equations (1) to (4) in the computer system 40.
+S45, or an example of interpolation calculation means according to the present invention.

Next, image data S1°s2. except image data S3. s,
, S, and the interpolated image data S obtained as above
, □r 823+534+S45, by performing so-called blur mask processing to relatively reduce the spatial frequency component (low spatial frequency component) of the flow image in the same manner as in the conventional example described above for the direction in which the flow image is generated. , each of these image data s1. s. +
SZ + 523r S34+S4, S4q,
The flow image appearing in the image carried by S5 is reduced. Although this is not essential in the present invention, these image data S1+S12. SZ, S23
・S34・S, ・S45・Since each image carried by S5 may contain information other than the tomographic plane corresponding to each image as a flow image, the flow image appearing in image 3 is 15 (see Figure 2), each of the above image data S1, S+2, SZ,
S23・S34・S4・S4. Since it is preferable that each image carried by t and s contains only information of each tomographic plane corresponding to each image, the flow image appearing in each image is reduced.

Next, the image data S engineering SI2 obtained as above
r 82' r S23 r S34 r
Based on each of 54S45 + 85', each image data Si', S+2, SZ,
S23 ・534SA' + 845 +
85', each image data S1, S12 r carrying a simulated flow image is simulated to show how the subject information of each tomographic plane corresponding to 85' appears as a flow image in image 3.
S21 S23 + S34 1 Sa
r S45 + S5' is generated.

FIG. 5 is a diagram illustrating an example of a filter for generating an image simulating a flow image.

Here, each image data Sl
r S+2 + Sz r S23 +
534Sa' + 845 + Ss' is convolved with the function shown in FIG. 5, and the flow image appearing in image 3 is simulated. Here, image data S23
Since S34 carries an image of a tomographic plane adjacent to the tomographic plane of image 3, a narrow filter function as shown in FIG. 5(a) is adopted as a filter function when performing convolution integration. As the distance from the tomographic plane of image 3 increases, image data S2, S, and ' are shown in Fig. 5(b).
, for image data S+2 + S45', the fifth
Figure (C), image data s1. For s5', see Figure 5 (
The filter function of d) is adopted.

Image data S1, S1□, Sz, 523S, simulating the flow image appearing in image 3 as described above
S number + 845 r Average value sB of S5'
-(St' +s, □'+82''+823+554
'+Sa'``S45''``S5') /
8...(5) is obtained for each pixel that corresponds to each other,
As a result, simulated flow image data SB representing an image simulating the flow image appearing in image 3 is obtained. In this embodiment, this simulated flow image data SB corresponds to the second image data according to the present invention, and is the image data sl, s, □ of the computer system 40 (see FIG. 3).

Sz r S2i, Si4. S4t S4
9. The function of obtaining simulated flow image data S8 based on S5 corresponds to flow image simulating means according to the present invention.

Next, according to the following formula (6), 5R-83-α・SB ...... (6)
For each corresponding pixel, weighted subtraction is performed between the image data S3 representing image 3 and the simulated flow image data SB obtained in the above manner, so that the same low space as the flow image I5 appearing in image 3 is Only the flow image 15 is reduced while leaving valid image information of frequency components. Here, α is a value determined through experiments or the like so that the flow image is best reduced, and for example, 0.9 to 0.95 is adopted.

Next, although it is not essential in the present invention, in this embodiment, the image data SR is further subjected to blur mask processing to relatively reduce the spatial frequency components (low spatial frequency components) of the flow image, and the image data SR is Image data SR' in which flow images remaining in the carried image are further reduced is generated.

This means that the flow image 15 appearing in image 3 is
1. S+2゜Sz + S23+ S34+ s
It also includes information from object parts other than the respective tomographic planes corresponding to a l Sa, + s5. Therefore, the flow image simulated based on the information of a finite number of tomographic planes (simulated flow image data SR) is Since it is possible that the flow image actually appears in image 3, it may be somewhat different, so regarding the image data SR that has been reduced in flow image as described above, the valid image information in the image carried by the image data SR is The flow image remaining in the image is further reduced to the extent that the flow image remains sufficiently.

Image data S from which the flow image obtained in this way has been removed
, 1' are transmitted to an image output device (not shown), and the image output device outputs a visible image based on the image data SR'.

Incidentally, in the above embodiment, the interpolated image data S L2+ S
2LS 34+S 4 g was calculated, but this interpolated image data S12°S 23. S 341 S 4
5 is omitted, and the image data Sl + s2.
The simulated flow image data S may be obtained based on Sa and s5. Further, in the above embodiment, five stimulable phosphor sheets L, 2. 3.4. Five image data Str representing images of mutually different tomographic planes obtained using Str.
Although the processing was performed based on Sz + S3 r Sa rS5, the number of image data used in carrying out the present invention is not limited to five, and the desired degree of flow image reduction, calculation time, etc. This can be determined in various ways with consideration.

Furthermore, although the above description has only been made regarding tomography of a straight trajectory, the present invention is not limited to this, but can also be applied to tomography of a trajectory such as a circle, an ellipse, a hypocycloid, or a spiral. In tomography of a trajectory other than a straight line, the superimposed blurred image (flow image) becomes two-dimensional, and its shape differs depending on the type of trajectory. Therefore, it is necessary to perform two-dimensional processing in blur mask processing and simulation processing.

Furthermore, in the above embodiment, a system using a stimulable phosphor sheet was described, but the tomographic image processing apparatus of the present invention can also be applied to a system using an X-ray sensitive silver salt film, etc. in addition to a system using a stimulable phosphor sheet. Of course, it can also be applied to systems.

(Effects of the Invention) As described in detail above, the tomographic image processing apparatus of the present invention provides an image of a desired first tomographic plane among a plurality of image data representing images of each of a plurality of tomographic planes. Based on image data other than the first image data representing the image, second image data representing an image simulating the flow image appearing in the image of the first tomographic plane is obtained, and this second image data and Since the configuration is configured to obtain third image data representing an image in which the flow image is reduced or removed based on the first image data representing the image of the first tomographic plane, the image of the first tomographic plane is Flow images in the image can be reduced or removed while leaving valid image information.

Further, by performing interpolation operations and calculations based on the plurality of image data, interpolated image data that simulates an image of a new tomographic plane is obtained, and this interpolated image data is used together with the other image data to obtain the second image. By obtaining the data, it is possible to more reliably reduce or remove flow images in the image of the first tomographic plane while leaving valid image information in the image.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing an example of a linear tomography device, FIG. 2 is a diagram schematically showing an example of a tomography image, and FIG. 3 is a diagram schematically showing an example of an X-ray image reading device and FIG. 4 is a perspective view showing a computer system including an embodiment of a tomographic image processing device; FIG. 4 is a diagram showing the flow of processing in the computer system; FIG. 5 is a diagram showing an image simulating a flow image. FIG. 1.2, 3, 4.5... stimulable phosphor sheet 6...
X-ray source 8...Subject 10, 11.12.
13.14... Fault plane 15... Flow image
20... X-ray image reading device 28... Laser light source
26... Rotating polygon mirror 29... Stimulated luminescent light 31... Photo multiplier 40... Computer system Fig. 1 Fig. 2

Claims (2)

[Claims] (1) A first image representing an image of a desired first tomographic plane among a plurality of image data representing images of a plurality of parallel and different tomographic planes of a subject obtained by tomography; flow image simulating means for obtaining second image data representing an image that simulates the flow image appearing in the image carried by the first image data, based on one or more other image data excluding the data; A tomographic cross section characterized by comprising: flow image removal means for obtaining third image data representing an image in which the flow image has been reduced or removed, based on the first image data and the second image data. Photographed image processing device. (2) Interpolation for obtaining one or more interpolated image data that simulates an image of a new tomographic plane sandwiched between the two adjacent tomographic planes by performing an interpolation calculation based on the plurality of image data. The tomographic image processing according to claim 1, further comprising a calculation means, wherein the flow image simulating means uses the interpolated image data together with the other image data to obtain the second image data. Device.