JP3163131B2 - X-ray equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an X-ray imaging apparatus having a function of determining a contrast image in contrast X-ray photography.

[0002]

2. Description of the Related Art In order to accurately insert a catheter, a guide, a wire, and the like into a target blood vessel of a subject, contrast X-ray imaging is performed in which a contrast agent is injected into a blood vessel in X-ray fluoroscopy. . However, even if the contrast agent is injected into the blood vessel, it immediately flows out of the imaging region. Therefore, in order to obtain an X-ray image (moving image) when the contrast agent is injected, it is necessary to detect the injection timing.

[0003] As a technique for detecting the timing,
The following two are known.

A first technique is disclosed in Japanese Patent Application Laid-Open No. 64-58243, and detects a contrast agent injection timing from a change in the average density of the entire screen. This method utilizes the fact that the average density of the entire screen decreases and darkens when a contrast agent mixes into the imaging region.

As the second technique, there is known a technique called "last image hold" in which an operator turns off a fluoroscopic switch simultaneously with injection of a contrast agent and holds an image immediately before the turning off.

[0006]

However, in the first technique, since the average density of the entire screen is viewed, if there is a movement of the subject, it is not determined that the contrast medium is injected. There is a problem that the detection accuracy is poor.

[0007] The above-mentioned second technique is based on the O switch of the perspective switch.
The FF must be synchronized with the injection of the contrast agent, and there is a problem that the operation is complicated.

The present invention has been made in view of the above circumstances, and has as its object to provide an X-ray imaging apparatus capable of automatically recognizing a contrast image even when a subject moves. .

[0009]

To achieve the above object, the present invention has the following arrangement.

According to a first aspect of the present invention, there is provided an X-ray imaging apparatus which obtains a digital X-ray image in time sequence by injecting a contrast agent into the object during X-ray imaging of the object. The image is divided into multiple blocks, and the average density of each block is
Mean density calculating means for determining the degree, and the mean density calculating means
Using the average density of each block obtained from
How the average density difference between adjacent blocks changes over time
Means for determining for each block of each position, that it has a determination means for pre-Symbol contrast status of each digital X-ray image based on the time-series changing mode of the flat <br/> average density difference is the calculated It is a feature.

According to a second aspect of the present invention, in the first aspect of the present invention, the determination means is based on a time-series change mode in which the average density difference is encoded.

According to a third aspect of the present invention, there is provided an X-ray imaging apparatus which obtains a digital X-ray image in time sequence by injecting a contrast agent into the object during X-ray imaging of the object. The image is divided into multiple blocks, and the average density of each block is
Mean density calculating means for determining the degree, and the mean density calculating means
And determining means for judging the contrast state of each digital X-ray image based on the output mode of the average density for each block obtained from the above.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the determination means is based on an output mode in which the average density is encoded.

[0014]

The operation of the apparatus having the above configuration will be described.

According to the first aspect of the present invention, the average density is obtained for each block divided into a plurality of blocks by the block image forming means, so that the accuracy of the contrast determination for each block is improved. Further, the time-series change mode of the average density difference differs between the contrast agent mixing and the movement of the subject. For this reason, the determination unit can accurately determine the contrast image based on the change mode even when the subject moves or the like.

According to the second aspect of the present invention, by encoding the average density difference, the determination is facilitated and the determination can be speeded up.

According to the third aspect of the present invention, the accuracy of contrast determination is improved for each block by obtaining the average density for each block divided into a plurality of blocks by the block image forming means. The output mode of the average density differs between the contrast agent mixing and the movement of the subject. For this reason, the determination means can accurately determine the contrast image based on the output mode even when the subject moves or the like.

According to the fourth aspect of the present invention, by encoding the average density, the determination is facilitated and the determination can be speeded up.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of an X-ray imaging apparatus 1 according to a first embodiment of the present invention.

The apparatus 1 includes an X-ray source (not shown) and an image intensifier (hereinafter referred to as “I. I.) 2) and I. I. The optical image of
An optical system 4 for guiding to a V camera 3 and an A / D for converting a TV video signal output from the TV camera 3 into a digital X-ray image
A converter 5, an original image frame memory 6 for storing a digital X-ray image as an original image, and a pair of buffers 7 for temporarily storing the digital X-ray image which is also the original image
A subtraction unit 8 for performing a subtraction process between the digital X-ray image (Xi) directly taken from the A / D converter 5 and the digital X-ray image (X _i-1 ) taken from the buffer 7 delayed by one frame; For example, when the original image is a 512 × 512 matrix, the original image is 128 × 128 as shown in FIG.
Is divided into 16 blocks (B _{00 to} B ₃₃ ) as one block, and a subtracted image frame memory (block image forming means) 9 for storing the subtracted image Gi after the subtraction processing, and the subtracted image Gi
An average value calculating unit (block image forming means) 10 for obtaining an average density for each block and forming a block image Si, a threshold generating unit 11 for outputting threshold values T ₁ and T ₂ , A comparison unit 12 that compares the threshold values T ₁ and T ₂ with the average density of each block of the block image Si to form an encoded image Si;
A plurality of coded image memories 13 for storing the coded images Bi
And whether the original image stored in the original image frame memory 6 is a contrast image (contrast agent is mixed) based on the data stored in each of the encoded image memories 13 and is determined to be a contrast image. And a decision unit 14 for outputting a mixed signal Sm to the digital X-ray generator 30 when the operation signal So and the mixed signal Sm are input.
A display system 16 for visually displaying a line image.

The original image frame memory 6 may be replaced with a peak trace unit 60 shown in FIG. The peak trace unit 60 shown in the figure has a comparator 61, a selector 62, and a frame memory 63.
The comparator 61 compares the data of the corresponding pixel between the output of the A / D 5 and the frame memory 63, and outputs the smaller one. This comparison is performed by scanning all pixels in one frame. Selector 62
In the case where the mixing signal Sm from the determination unit 14 is not output (in the case of inactive), the output of the A / D 5 is written to the frame memory 63 as it is, and the mixing signal Sm is output (in the case of active). Is the comparator 61
Is written to the frame memory 63. With such a configuration, the smallest value is recorded in each pixel of the frame memory 63 during the period when the mixed signal Sm is being output. Therefore, immediately before the mixed signal Sm is turned off, even if the contrast agent has disappeared, the original image in the state of the darkest dye remains in the frame memory 63.

FIG. 4 is a diagram showing the operation of the subtractor 8. The image X _i-1 to be subtracted by the subtraction unit 8 may be several frames before as long as the movement of the subject can be almost ignored even if it is not one frame before. Subtraction unit 8
Is to obtain the subtraction image Gi after the subtraction by subtracting the image X _i-1 of one frame before from an image Xi as shown in Figure 3. It should be noted that the region shown in black in the figure indicates the portion where the contrast agent is mixed.

As shown in FIG. 5, the average value calculating section 10 obtains the average density in each block b for the subtracted image Gi shown in FIG. 4 to form a block image Si. A portion where the contrast agent has flowed and disappeared has a positive value, a portion where the contrast agent has flowed in has a negative value, and a portion where no contrast agent has flown has a value of 0. Therefore, for example, a distribution of values as shown in FIG. 6 is obtained.

The threshold generation unit 11 simulates in advance a threshold value T ₁ of a subtraction value when the contrast medium flows in and a threshold value T ₂ of a subtraction value when the contrast medium flows and disappears. The values T ₁ and T ₂ are output to the comparison unit 12. The values T ₁ and T ₂ have a relationship of T ₂ > T ₁ .

Based on the transmitted threshold values T ₁ and T ₂ , the comparing section 12 converts the block image Si output from the average value calculating section 12 into “−”,
This is converted into a sign of “0” or “+”. That is, the average value in the block b is equal to the threshold value T ₁
If the value is smaller than the threshold value, the sign is “−”. If the value is between the _two values T ₁ and T ₂ , the sign is “0”. If the value is larger than the threshold value T ₂ , the sign is “+”. For example, assuming that the threshold values T ₁ and T ₂ are −5 and 5, respectively, the block image Si shown in FIG. 5 becomes “−”, “0”,
It becomes a coded image Bi coded to “+”. Comparison section 12
Performs the above operation for each frame, and stores the encoded image Bi in the encoded image memory 13 in order from # 1 to #n for each frame. For example, as shown in FIG. 7, as a result of performing subtraction with the original images X ₂ and X ₁ , the first encoded image B
_2-1 encoded image memory (# 1) stored in 13, then the original image X ₃ and X ₂ and the subtracting the result of performing coding image B _3-2 coded image memory (# 2) 13 is stored. In this way, the comparison unit 12 sequentially stores the encoded images B _4-3 and B _5-4 resulting from the subtraction of the original images X ₄ and X _{5 in the} same manner as the encoded image memory (# 3). 13, memory (# 4) 1
3 is stored. The comparison unit 12 has a memory (#
n) After the storage up to 13, the process may return to # 1 periodically to rewrite the data previously stored in # 1.

As shown in FIG. 8, the judging section 14 comprises a first table 141, a plurality of counters 142 provided corresponding to the number of code numbers to be described later, an address generator 143, 2 tables 144.

The address generator 143 generates the same n addresses simultaneously in each coded image memory 13, and then generates the next n addresses simultaneously in each coded image memory 13.
This is repeated until the last address.

The first table 141 determines a code number (“code 0”, “code 1”, etc.) based on data fetched for each address from each coded image memory 13 and generates the code number. Is what you do. For example, when the code number for the first address is “code 0”, “1” is input to the counter 142 for “code 0”, and “0” is input to the other counters 142.

The determination of the code number by the first table 141 is based on the assumption that data as shown in FIG. 9 is obtained for a certain address. As shown in the first example, if all are “0”, “code 0” is used. As shown in the second example, if “−” is continued between “0” (position shift), “code 1” is used. As shown in the example, when "+" continues between "0" (position shift), "code 2" is used, and as shown in the fourth example, "0", "-", "+", "0" If they appear in order (contrast agent mixture), they are determined in advance as "code 3", and as shown in the fourth example, if "0", "-", and "+" appear randomly, they are determined as "code 4". A standard is determined, and a code number is output according to the standard.

That is, the pattern of the contrast agent mixing shows that the change between n frames is focused on one block b1 (see FIG. 7) in each encoded image Bi. It changes from "0" to "-", and further changes to "+" and "0" (code 3). On the other hand, when the original image of the subject moves from left to right to X ₁₀ , X ₁₁ , and X ₁₂ , as shown in FIG. Image B _11-10 ,
_B12-11 suddenly _changes from "0" to "+" (block b2),
A change mode different from the contrast agent inflow, such as "-" to "0" (block b3) or "-" to "+" (block b4), is shown (code 1 or code 2).

The counter 142 counts up each time "1" is input from the first table 141, and finally sums up the number for each frame to produce a second table 144.
Is output to

The second table 144 stores each counter 142
It is determined whether or not the original image is a contrast image based on the output value from. If it is determined that the original image is a contrast image, a mixed signal Sm is output. For example, if the number of “codes 3” is at least a predetermined number or more and the number of “codes 0, 1, 4” is equal to or less than a predetermined number according to the output value from each counter 142, the original image is a contrast image (contrast agent mixed). Is determined. If the number of “code 1” or “code 2” is equal to or more than a predetermined number, it is determined that the position is misaligned, and the mixed signal Sm is not output. As described above, the determination unit 14 can accurately determine whether or not the image is a contrast image based on the time-series change mode of the encoded image Bi, in distinction from the movement of the subject.

Next, the operation of the above-described embodiment apparatus 1 will be described with reference to FIG.

An operator injects a small amount of a contrast agent into the subject while performing X-ray fluoroscopy of the subject. X-rays transmitted through a subject by X-ray photography are I.D. I. 2 is converted to an optical image by the TV camera 3 via the optical system 4
It is converted to a video signal, and the digital X
It is output as a line image. The digital X-ray images include those before mixing the contrast agent, those during mixing, and those after mixing and flowing away. The digital X-ray images are all stored in the original image frame memory 6, and are also output to a subtraction unit 8 and a pair of buffers 7 for generating an encoded image Bi.

Next, the subtraction section 8 forms a subtraction image Gi based on the images Xi and Xi _-1 sent from the A / D converter 5. Further, the subtraction unit 8 temporarily stores the subtraction image Gi in the subtraction image frame memory 9. Next, the averaging unit 10 forms a block image Si based on the subtraction image Gi. Comparison section 1
2 forms an encoded image Bi obtained by encoding the block image Si based on the threshold values T ₁ and T ₂ from the threshold generator 11 and sequentially encodes the encoded image memory 13
To be stored. When the determination unit 14 determines that the original image captured in the original image frame memory 6 is a contrast image based on the time-series change mode of the encoded image Bi stored in each encoded image memory 13, The signal Sm is sent to the original image frame memory 6 and the display unit 16.

Next, the original image frame memory 6 stores the judgment unit 1
4 to the display system 16. When an operation signal So is transmitted to the display system 16 by a switch operation performed simultaneously with the injection of the contrast agent by the operator, and the mixed signal Sm is further transmitted to the display system 16, the display system 16 outputs both the mixed signal Sm and the operation signal So. When Sm and So are complete, the original image fetched from the original image frame memory 6, that is, a contrast image is displayed, and the mixed signal Sm sent from the determination unit 14 is displayed. The operator determines that the mixed signal Sm is displayed on the display system 16 immediately after transmitting the operation signal So.
Make sure that is correctly determined. And display system 1
The image displayed in 6 is used for diagnosis.

According to the apparatus 1 of the embodiment, the operator can automatically and reliably obtain a contrast image even when the subject moves.

Further, since the operation signal is input, even if the judgment unit 14 erroneously judges that the contrast agent is mixed due to the movement of the subject even though the contrast agent is not injected. Since it is not displayed on the display system 16, it does not interfere with the normal see-through state.

FIG. 12 is a schematic configuration diagram of an X-ray imaging apparatus 20 according to a second embodiment of the present invention. The main difference from the first embodiment 1 is that the threshold generator 2
1, a comparing unit 22, an encoded image memory 23, and a determining unit 2
There are four. The components having the same functions as those of the device 1 of the first embodiment are denoted by the same reference numerals, and the detailed description thereof will be omitted. It should be noted that the original image frame memory 6 may be replaced by the peak trace unit 60 shown in FIG. 3 in the second embodiment device 20 as in the first embodiment device 1.

The threshold generator 21 outputs more (four in this embodiment) threshold values T21, T22, T23 and T24 as compared with the first embodiment. By providing a large number of threshold values T21 to T24, the determination accuracy of the determination unit 24 can be increased.

The comparing section 22 calculates the average value calculating section 12 based on the transmitted threshold values T21 to T24.
The block image Si output from is expressed as "-
−], “−”, “0”, “+”, and “++”. That is, “−−” when the average value in the block b is smaller than the threshold value T21, “−” when the average value is between the threshold value T21 and the value T22, and “−−” between the threshold value T22 and the value T23. "0" when the threshold value is reached, the threshold value T23 and the value T24
If it is between “+”, the threshold value T
If it is larger than 24, an encoded image is created as a code of “++” and stored in the encoded image memory 23.

The coded image memory 23 has a plurality of devices 1 in the first embodiment, but one in the second embodiment.

As shown in FIG. 13, the determination section 24
A distributor 241, a plurality (five in this example) of counters 242 provided corresponding to the number of codes, and an address generator 2
43 and a table 244.

The address generator 243 generates addresses sequentially from the first address to the last address in the coded image memory 23.

When the sign of a certain pixel of the coded image stored in the coded image memory 23 is “−−”, the distributor 241 sets “1” to the counter 242 for the code “−−”. The operation of inputting "0" to the other counter 242 is similarly performed for other codes.

The counter 242 outputs “1” from the distributor 241.
Is counted up each time is input, and finally the number is summed up for each frame and output to the table 244.

The table 244 determines whether or not the original image is a contrast image from the output values from the respective counters 242, and outputs a mixed signal Sm when the image is determined to be a contrast image. For example, when a contrast agent is mixed, the sign “−” increases and the sign “+” decreases. Also, the sign “−” is small and “+”
When there is much, it is determined that the phase in which the contrast agent flows out. In this case, it is determined that the image is a contrast image, and the mixed signal Sm is output. Further, in the case of a positional shift, the numbers of “−” and “+” are substantially the same, and in this case, the mixed signal Sm is not output.
Other examples include extremely large numbers of "-" or "+"
There may be a case where there is at least one "+" and there are few "-" and "-". In the former case, it is considered that the level of the entire image has changed due to a change in the X-ray output or the like.

According to the apparatus 20 of the second embodiment configured as described above, it is possible to determine the presence or absence of the contrast agent from one coded image, and therefore, compared to the apparatus 1 of the first embodiment,
The contrast image can be determined quickly.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention. For example, when performing a contrast-enhanced X-ray imaging of a periodically changing portion such as a heart motion, a subtraction process is performed on an image having the same cardiac phase based on a phase signal such as a heartbeat synchronization signal such as an R wave. Alternatively, an encoded image may be formed on an in-phase image in the same manner as in the present embodiment to find a contrast image.

[0051]

According to the present invention described in detail above, the following effects can be obtained.

According to the first aspect of the present invention, the digital X-ray image is divided into blocks, and the contrast of each digital X-ray image is determined based on the time-series change mode of the average density of each block. Therefore, it is possible to provide an X-ray imaging apparatus capable of automatically recognizing a contrast image even when a subject moves or the like.

According to the second aspect of the present invention, in addition to the effect of the first aspect, since the average density difference is coded, the determination is facilitated and the determination can be speeded up.

According to the third aspect of the present invention, the digital X-ray image is divided into blocks, and the contrast of each digital X-ray image is determined based on the output mode of the average density of each block. It is possible to provide an X-ray imaging apparatus capable of automatically recognizing a contrast image even when there is a movement of the image.

According to the fourth aspect of the present invention, in addition to the effect of the third aspect, since the average density difference is encoded, the determination is facilitated and the determination can be speeded up.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an X-ray imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an operation of a subtraction unit of the device shown in FIG.

FIG. 3 is a diagram showing another example of the original image frame memory shown in FIG. 1;

FIG. 4 is a diagram showing an operation of a subtraction unit of the device shown in FIG.

FIG. 5 is a diagram illustrating an example of a block image.

FIG. 6 is a diagram illustrating an example of an encoded image.

FIG. 7 is a diagram illustrating an example of an original image and a coded image showing a temporal change mode when a contrast agent is mixed.

FIG. 8 is a diagram illustrating a configuration of a determination unit illustrated in FIG. 1;

FIG. 9 is a diagram illustrating an operation of a determination unit illustrated in FIG. 8;

FIG. 10 is a diagram showing an example of an original image and an encoded image showing a temporal change mode when a subject moves.

FIG. 11 is a view showing the operation of the device shown in FIG. 1;

FIG. 12 is a schematic configuration diagram of an X-ray imaging apparatus according to a second embodiment of the present invention.

13 is a diagram illustrating a configuration of a determination unit illustrated in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 X-ray imaging apparatus 9 Subtraction image frame memory (block image forming means) 10 Average value calculation part (block image forming means) 14 Judgment part Bi, _B2-1 , _B3-2 , _B4-3 , _{B5- 4} , _B11-10 , B
_12-11 coded image Si block image X ₁ to X _5, X ₁₀ to X ₁₂ digital X-ray image

Claims (4)

(57) [Claims] 1. An X-ray imaging apparatus which obtains a digital X-ray image in time sequence by injecting a contrast agent into the object during X-ray imaging of the object, wherein the digital X-ray image is divided into a plurality of blocks. Average density calculation to calculate the average density for each block by dividing
Output means and each block obtained from the average density calculation means.
Using the average density of
Time-sequential change of the average density difference for each block at each position
Means for determining, X-rays imaging apparatus characterized by having a determining means for pre-Symbol contrast status of each digital X-ray image based on the time-series changing mode of the average density difference is thus determined. 2. The X-ray imaging apparatus according to claim 1, wherein the determination unit is based on a time-series change mode in which the average density difference is encoded. 3. An X-ray imaging apparatus which obtains a digital X-ray image in time sequence by injecting a contrast agent into the object during X-ray imaging of the object, wherein the digital X-ray image is divided into a plurality of blocks. Average density calculation to calculate the average density for each block by dividing
Output means and each block obtained from the average density calculation means.
Digital X based on the average density output mode
An X-ray imaging apparatus comprising: a determination unit configured to determine a contrast state of a line image. 4. The X-ray imaging apparatus according to claim 3, wherein the determination unit is based on an output mode in which the average density is encoded.