JPH05161632A - Radiation diagnostic device - Google Patents

Abstract

PURPOSE:To provide the radiation diagnostic device which can distinguish sections really composed of different organizations each other even when the X-ray transmitting doses are equal and can obtain an image not to erase the composition information, especially, the diseased part information of a patient. CONSTITUTION:This device is equipped with an X-ray device to obtain the image based on the X-ray transmitting dose of a reagent C for the respective two kinds of energy at least, arithmetic part 10 to calculate the relative variation ratio of the X-ray transmitting dose for the respective two kinds of energy at least for each picture element in the image, and means to obtain an image 13 corresponding to the variation ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation diagnostic apparatus for obtaining a new image based on a plurality of radiation images obtained by photographing with radiation of a plurality of types of energy.

[0002]

2. Description of the Related Art Usually, a radiation diagnostic apparatus obtains an X-ray transmission image according to a transmission amount of radiation, for example, X-rays transmitted through a subject, in other words, an X-ray absorption amount, and provides the image for diagnosis. However, the drawback of this X-ray transmission image is that even if the tissue component on the first transmission path of X-rays and the tissue component on the second transmission path are actually different, If the X-ray absorption amounts of are equal, they are displayed as if they were the same tissue, and if a specific tissue of interest, such as a blood vessel, and another tissue, such as bone, are on the same path, That is, it is hidden by bones and not displayed.

Further, in recent years, a so-called energy subtraction method has been devised, which is a method of erasing and displaying only a tissue that hinders diagnosis of a specific tissue of interest, for example, only bone or soft tissue. This energy subtraction method uses the property that the X-ray absorption coefficient of a substance depends on the energy of X-rays, and that the energy dependence of the X-ray absorption coefficient of a substance depends on the difference in the atomic number of the substance. To do. Here, the X-ray absorption coefficient is an absorptance per unit thickness (X-ray transmission path length) of a substance, and thus the same substance is the same regardless of the difference in thickness. The energy subtraction method will be described below.

In the energy subtraction method, first, X
An energy spectrum of a band in which a relatively low energy X-ray obtained by applying a relatively low kilovolt tube voltage to a X-ray tube is applied to a subject, and the X-ray transmitted through the subject has a relatively low average energy. An X-ray transmission image having a distribution (hereinafter referred to as "low energy image") is obtained. here,
For the sake of convenience, it is assumed that the transmission image area of the subject is a lung field including bones and blood vessels. Next, a tube voltage higher than the tube voltage at the time of obtaining the low energy image is applied to the X-ray tube, and the X-ray transmission image (hereinafter referred to as “X-ray transmission image” having an energy spectrum distribution of a band in which the X-ray has a relatively high average energy High energy image "
Called)).

The low energy image is subtracted from the obtained high energy image to obtain an image of the difference between the two images. However, before subtraction, each of the high energy image and the low energy image is multiplied by an appropriate weighting coefficient so that the tissue to be erased is offset by the subtraction. This weighting factor is set according to the energy dependence of the X-ray absorption coefficient of the tissue to be erased, and by variously changing it, for example, "the image in which only bone is erased" or "the image in which only soft tissue is erased" It is possible to obtain

However, the diagnosis by the "image in which the desired tissue is erased" obtained by this energy subtraction method has the following problems. That is, if the tissue that has been erased to aid in the discovery of the lesion, which is the original purpose of diagnosis, is composed of the same substance that makes up the lesion, the tissue that is erased by the lesion It will be erased with. For example, the image obtained by the energy subtraction method is the "image in which only the bones are deleted",
When the transmission image area is a lung field and the lesion to be diagnosed is a tissue containing calcium, the lesion is erased together with the bone, and as a result, accurate diagnosis is hindered.

[0007]

Therefore, an object of the present invention is to distinguish between parts that are actually composed of different tissues even if the radiation transmission amount is the same, and the composition information of the subject, especially It is an object of the present invention to provide a radiation diagnostic apparatus capable of obtaining an image without losing lesion area information.

[0008]

A radiation diagnostic apparatus according to the present invention is a radiation apparatus for obtaining an image based on a radiation transmission amount of a subject for at least two types of energy, and a radiation transmission for each of the at least two types of energy. It is characterized by comprising means for obtaining a ratio of quantities for each pixel of the image, and means for obtaining an image according to the ratio.

[0009]

According to the present invention, the tissue information for each pixel can be obtained based on the ratio of at least two types of radiation transmission amount for each energy. As a result, even if the radiation transmission amount is the same, in reality It is possible to distinguish between parts composed of different tissues and obtain an image in which the composition information of the subject, particularly the lesion information, is not lost.

[0010]

Embodiments will be described below with reference to the drawings. Here, the radiation used in the radiation diagnostic apparatus according to the present invention will be described below as X-rays. FIG. 1 is a block diagram showing the configuration of an X-ray diagnostic apparatus according to the first embodiment of the present invention.

The X-ray diagnostic apparatus according to the first embodiment is an X-ray apparatus for obtaining X-ray transmission image data, a storage apparatus for storing the X-ray transmission image data obtained by the X-ray apparatus, and the storage apparatus. An arithmetic unit 10 for performing a predetermined arithmetic process on the X-ray transmission image data stored in, and an image (hereinafter referred to as “energy characteristic value image”) data after arithmetic output from the arithmetic unit 10 are stored and monitored. A frame memory 11 that outputs an energy characteristic value image according to the scanning method of 13, a digital / analog (D / A) converter 12 that performs digital / analog conversion of the energy characteristic value image input from the frame memory 11, and A / A monitor 13 that displays an energy characteristic value image output from the D converter 12 and a system control unit 14 that controls the entire system are provided.

The X-ray apparatus includes an X-ray tube 1 for irradiating the subject C with X-rays, an X-ray controller 3 for applying a tube voltage to the X-ray tube 1, and an X-ray tube with the subject C interposed therebetween. 1, an image intensifier 2 for converting a transmission X-ray image of the subject C into an optical image, and an optical image from the image intensifier 2 are converted into electric signals to obtain X-ray transmission image data. It comprises a TV camera 4 and an analog / digital (A / D) converter 5 for analog / digital converting the X-ray transmission image data obtained by the TV camera 4. Here, the X-ray tube 1 is X
The X-ray having energy corresponding to the tube voltage applied from the line control unit 3 is bombarded. Further, the X-ray controller 3 is the system controller 1
4 receives the tube voltage control signal and controls the tube voltage applied to the X-ray tube 1.

The storage device is an IL0 storage unit 6 and an IH0 storage unit 7.
And an ILC storage unit 8 and an IHC storage unit 9. I
The L0 storage unit 6 detects the X-ray exposure amount of the X-rays emitted from the X-ray tube 1 without passing through the subject C with relatively low energy X-rays (this X-ray exposure data). The quantity data is hard to say as an image, but for convenience of explanation, it is intentionally referred to as a “low energy image IL0”), and the IH0 storage unit 7 is a relatively high energy X-ray without passing through the subject C, that is, The X-ray exposure amount data (hereinafter, referred to as “high energy image IH0”) in which the X-ray exposure amount emitted from the X-ray tube 1 is detected is stored, and the ILC storage unit 8 receives low energy X-rays. Sample C
X-ray transmission image (hereinafter referred to as "low energy image IL
(Hereinafter referred to as “C”), and the IHC storage unit 9 stores an X-ray transmission image (hereinafter referred to as “high energy image IHC”) obtained by imaging the subject C with high-energy X-rays. These IL0
Storage unit 6, IH0 storage unit 7, ILC storage unit 8, IHC storage unit 9
The write / read timing of each is determined by the system controller 14
Controlled by. Here, the energy value of the high energy X-rays and the energy value of the low energy X-rays are the absorption coefficient of the substance of the site of interest (lesion) in the high energy X-ray and the substance of the site of interest (lesion) in the low energy X-ray. The absorption coefficient and the difference are set so that the difference is most prominent. Here, the ratio between the absorption coefficient of the high energy X-rays and the absorption coefficient of the low energy X-rays is referred to as an energy characteristic value.

The calculation unit 10 inputs each image data from each of the IL0 storage unit 6, the IH0 storage unit 7, the ILC storage unit 8 and the IHC storage unit 9, and calculates the energy characteristic value for each pixel of the image. The formula for calculating the energy characteristic value R is obtained as follows. However, the average absorption coefficient in the case of a high energy X-ray in a certain pixel (x, y) is set to μH (x, y), and the average absorption coefficient in the case of a low energy X-ray in the same pixel (x, y) is set to μL ( x, y) and the subject C of the same pixel (x, y)
, And the pixel value at the same pixel (x, y) of the high energy image IHC is IHC (x, y) and at the same pixel (x, y) of the low energy image ILC. I
Let LC (x, y) be the same pixel (x,
The pixel value in y) is IH0 (x, y) and the low energy image I
The pixel value at the same pixel (x, y) of L0 is IL0 (x, y). First, a generally known equivalent equation is shown.

ILC (x, y) = IL0 (x, y) .exp (-. Mu.L (x, y) .t (x, y)) (1) IHC (x, y) = IH0 (x, y) ) ・ Exp (−μH (x, y) ・ t (x, y)) (2) Next, from equations (1) and (2), the energy characteristic value R (x, y) at the pixel (x, y) is calculated. ) Can be expressed by the following formula.
However, "In" is a natural logarithm. R (x, y) = μH (x, y) / μL (x, y)

= {Ln (ILC (x, y) / IL0 (x, y))} / {ln (IHC (x, y) / IH0 (x, y))} (3) The calculation according to equation (3) is performed for each pixel of the image input from the storage device, and output as energy characteristic value image data. This energy characteristic value image data is displayed on the monitor 13 via the frame memory 11 and the digital / analog (D / A) converter 12 as described above. Next, the operation of the X-ray diagnostic apparatus according to the first embodiment configured as described above will be described with reference to FIGS. 2 to 6.

FIG. 2 is a diagram showing the composition and X-ray path of the subject for explaining the operation of the X-ray diagnostic apparatus shown in FIG. 1. FIG. 3 is an X-ray path for the subject shown in FIG. It is a figure which shows the comparison of the X-ray dose distribution of each high and low energy image, FIG. 4 is a figure which shows the change of the absorption coefficient with respect to the X-ray energy for every X-ray path shown in FIG. 2, and FIG. 5 is a diagram showing energy characteristic values calculated according to the ratio of the absorption coefficients shown in FIG. 4 for each X-ray path of the subject shown in FIG.

As shown in FIG. 2, the subject C is assumed to be composed of a tissue a composed of a uniform material layer and a tissue b composed of a material having an atomic number different from that of the material. Here, for convenience sake, four X-ray paths P1, P2, P3 and P4 will be described. This 4
Each of the X-ray paths P1, P2, P3 and P4 is assumed to pass through different positions in the subject C shown in FIG. As shown in FIG. 2, the X-ray paths P1 and P2 have the same length (hereinafter simply referred to as "path length") in the subject C according to the positions of the X-ray paths, but on the X-ray path. The compositions are different, and the positions P3 and P4 have the same path length, but the compositions on the X-ray path are different, and the positions P4 and P1 have the same composition on the X-ray path for the uniform substance a, The length is different.

First, relatively low energy, for example, tube voltage 7
An X-ray image obtained by directly detecting the X-rays emitted from the X-ray tube 1 without using the subject C with the X-rays obtained at 0 kV, that is, a low energy image IL0 is obtained and stored in the IL0 storage unit 6. To do. Similarly, an X-ray image obtained by directly detecting X-rays emitted from the X-ray tube 1 without passing through the subject C with relatively high energy, for example, X-rays obtained at a tube voltage of 120 kV, that is, high energy The image IH0 is obtained and stored in the IH0 storage unit 7.

Next, the same low energy (tube voltage 70 kV) X-rays as when the low energy image IL0 is obtained, this time an X-ray transmission image obtained through the subject C, that is, the low energy image I.
The LC is obtained and stored in the ILC storage unit 8. Similarly, when the high energy image IH0 is obtained, the same high energy (tube voltage 120 k
The X-ray transmission image obtained through the subject C with the high-energy X-ray of V), that is, the high-energy image IHC is obtained and stored in the IHC storage unit 9.

Here, as shown in FIG. 3, four X-ray paths P
The transmitted X-ray doses at 1, P2, P3, and P4 differ depending on the difference in composition and thickness, and also due to the difference in X-ray energy. As shown in FIG. 4, the X-ray paths P1 and P4 having the same composition have the same change state of the absorption coefficient, and the change state of the absorption coefficient at the X-ray paths P1 and P4 and the change state of the absorption coefficient at the paths P2 and P3. Is different from. For this reason, the energy characteristic value R at the position of the subject C corresponding to each X-ray path obtained by the calculation unit 10 is as shown in FIG.
In the case of 4, the energy characteristic values of the X-ray paths P1 and P4 and the energy characteristic values of the X-ray paths P2 and P3 are different. The energy characteristic value image is obtained according to the obtained energy characteristic value and displayed on the monitor 13.

This energy characteristic value image makes it possible to distinguish between portions actually composed of different tissues at the time of diagnosis, and to obtain composition information of the subject, particularly lesion area information, without disappearing.

As described above, according to the X-ray diagnostic apparatus of the present embodiment, it is possible to distinguish between portions actually composed of different tissues, and the energy characteristics such that the composition information of the subject, especially the lesion information, does not disappear. You can get the value.

Next, a second embodiment will be described. Figure 6
FIG. 6 is a block diagram showing a configuration of an X-ray diagnostic apparatus according to a second embodiment of the present invention. Regarding the components of this embodiment, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals and their description is omitted.

In this embodiment, the high-energy image IHC stored in the IHC storage unit 9 and the energy characteristic value image stored in the frame memory 11 are individually weighted by the weighting processing unit 20 to obtain 1 It obtains a single image, that is, a weighted image. However, the X-ray transmission image for weighting the energy characteristic value image may be the low energy image ILC, or the high energy image IHC and the low energy image ILC.
It may be an average image obtained by averaging and.

The weighting processing section 20 performs the calculation of the following equation. However, the variables used in the following equation are those used in equation (1), and the pixel value at the pixel (x, y) of the weighted image A is A (x, y). However, a and b are weighting factors. A (x, y) = a · R (x, y) + b · IHC (x, y) (4)

This calculation is performed for each pixel to obtain a weighted image A. Although not shown, the weighting processing unit 20 is provided with a volume for independently adjusting the weighting factors a and b, and an appropriate weighted image A can be obtained by variously adjusting the weighting factors a and b. it can. By observing the weighted image A, it is possible to make a diagnosis while confirming the position of the region of interest.

As described above, according to the X-ray diagnostic apparatus of the present embodiment, as in the first embodiment, it is possible to distinguish between portions that are actually composed of different tissues, and the composition information of the subject, especially The diagnosis can be made without losing the lesion information, and the position of the lesion can be confirmed in more detail than in the case of the first embodiment.

Next, a third embodiment will be described. Figure 7
FIG. 6 is a block diagram showing a configuration of an X-ray diagnostic apparatus according to a third embodiment of the present invention. Regarding the components of this embodiment, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals and their description is omitted. The present invention obtains one image by using the information of the energy characteristic value image as the degree of emphasis of the frequency processing of the X-ray transmission image.

In this embodiment, the high energy image IHC stored in the IHC storage unit 9 is frequency-processed by the frequency processing unit 21 based on the pixel value of the energy characteristic value image stored in the frame memory 11. A frequency-processed image is obtained. However, the energy characteristic value image and the X-ray transmission image subjected to the frequency processing may be the low energy image ILC, or an average image obtained by averaging the high energy image IHC and the low energy image ILC. .

The frequency processing section 21 calculates the following equation. However, the variables used in the following equation are those used in equation (1), and the pixels (x,
Let the pixel value in y) be B (x, y). Where k
(I, j) are filter coefficients, and m and n are filter sizes.

[0032]

[Equation 1]

The calculation of the equation (5) is performed for each pixel to obtain the frequency processed image B. Although not shown, the frequency processing unit 21
, The filter coefficient k (i, j) and the filter size m,
Volumes for adjusting n are provided respectively, and an appropriate frequency processed image B can be obtained by variously adjusting the filter coefficient k (i, j) and the filter sizes m, n. With this frequency-processed image B, it is possible to make a diagnosis while confirming the boundary position between tissues, which cannot be recognized only by the X-ray transmission image.

As described above, the X-ray diagnostic apparatus according to this embodiment can more accurately distinguish the boundary positions of the portions actually composed of different tissues as compared with the case of the first embodiment. In addition, it is possible to make a diagnosis without erasing the composition information of the subject, especially the lesion information, and it is possible to confirm the position of the lesion in more detail than the confirmation.

Next, a fourth embodiment will be described. Figure 8
FIG. 6 is a block diagram showing a configuration of an X-ray diagnostic apparatus according to a fourth embodiment of the present invention. Regarding the components of this embodiment, the same components as those of the first embodiment shown in FIG. 1 are designated by the same reference numerals and their description is omitted.

In this embodiment, an energy characteristic value image stored in the frame memory 11 and represented by grayscale information is color-processed by the color processing section 22 to obtain a color energy characteristic value image C. The color processing unit 22 is the arithmetic unit 1
The energy characteristic value image R obtained from 0 and output from the frame memory 11 is converted into the energy characteristic value of each pixel by using three kinds of hues, usually three primary colors of red (R), blue (B) and green (G). Depending on the hue and its chromaticity. The colorized color energy characteristic value image C is displayed on the monitor 13 via the D / A converter 12. As described above, according to the X-ray diagnostic apparatus of this embodiment, the X-ray transmission image can be displayed more faithfully than in the case of the previous embodiment, and the portions composed of different tissues can be clearly distinguished by color. It is possible to make a diagnosis without erasing the composition information of the subject, especially the lesion information.

Although not shown, the color energy characteristic value image C and the X-ray transmission image (grayscale image) obtained by the apparatus of this embodiment, for example, the high energy image IHC stored in the IHC storage unit 9 are superposed. That is, one image may be obtained by using the high energy image IHC as the brightness of the color energy characteristic value image C, and the one image may be displayed. In this case, the position of the lesion area in the subject can be accurately recognized by observing such superimposed images. The X-ray transmission image to be superimposed here may be a low energy image ILC or a high energy image ILC.
It may be an average image obtained by averaging HC and low energy image ILC.

The present invention is not limited to the above embodiments, but can be implemented with various modifications without departing from the gist of the present invention. For example, in the above embodiment, the tube voltage was changed to obtain X-rays of two kinds of energy. However, a filter is inserted between the X-ray tube and the subject or between the subject and the image intensifier, or a filter is used. X by inserting
The linear energy may be changed.

In the above embodiment, the correction of each pixel of the X-ray image obtained without the object to output the correction to the storage unit in order to make the conversion characteristics of the image intensifier and the TV camera uniform and eliminate the error. It may be performed before, or the scattered radiation correction or the beam hardening correction may be performed. That is, the error component due to the scattered radiation generated during the transmission of the object C included in the X-ray transmission image data input from the X-ray device by the scattered radiation correction is removed, and the X-ray transmission image data having no error component due to the scattered radiation is obtained. Obtainable. Also, the component due to the soft X-ray can be removed from the X-ray transmission image data by the beam hardening correction, and the X-ray transmission image data having only the component due to the hard X-ray can be obtained.

In the above embodiment, the X-ray images ILO and IH0 obtained without passing through the subject are taken every time when the apparatus of this embodiment is operated.
That is, for each X-ray of various energies and for each gain of the imaging system at the time of conversion of various pixel values, it is stored and the appropriate X-ray images ILO and IH0 are selected by inputting the imaging conditions. In that case, the X-ray image ILO,
There is no need to find IH0 each time the apparatus of this embodiment operates, and diagnosis can be performed very efficiently. Alternatively, the X-ray images ILO and IH0 may be calculated from the imaging conditions using a predetermined approximate function formula.

[0041]

As described above, according to the present invention, the tissue information for each pixel can be obtained based on the relative change rate of the X-ray transmission amount for at least two types of energy.
As a result, even if the X-ray transmission amount is the same, it is possible to obtain an image in which the portions actually composed of different tissues can be distinguished from each other and the composition information of the subject, particularly the lesion information, is not lost. It is possible to obtain an X-ray diagnostic apparatus capable of performing the above.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a composition of an object and an X-ray path for explaining the operation of the X-ray diagnostic apparatus shown in FIG.

FIG. 3 is a diagram showing a comparison of X-ray dose distributions of high and low energy images of the subject shown in FIG.

FIG. 4 is a diagram showing changes in absorption coefficient with respect to X-ray energy on the X-ray path shown in FIG.

5 is a view of each X-ray path of the subject shown in FIG.
The figure which showed the change of the absorption coefficient shown in FIG.

FIG. 6 is a block diagram showing a configuration of an X-ray diagnostic apparatus according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing the arrangement of an X-ray diagnostic apparatus according to the third embodiment of the present invention.

FIG. 8 is a block diagram showing the arrangement of an X-ray diagnostic apparatus according to the fourth embodiment of the present invention.

[Explanation of symbols]

1 ... X-ray tube, 2 ... Image intensifier, 3 ... X
Line control unit, 4 ... TV camera, 5 ... Analog / digital converter, 6 ... IL0 storage unit, 7 ... IH0 storage unit, 8 ... ILC storage unit, 9 ... IHC storage unit, 10 ... Arithmetic unit, 11 ... Frame memory , 12 ... Digital / analog converter, 13 ... Monitor, 14 ... System control section.

Front page continued (72) Inventor Dr. Nakayama 1385-1 Shimoishigami, Otawara-shi, Tochigi Stock company Toshiba Nasu factory

Claims (1)

[Claims] 1. A radiation apparatus for obtaining an image based on the radiation transmission amount of a subject for each of at least two types of energy; and a ratio of the radiation transmission amount for each of at least two types of energy is obtained for each pixel of the image. A radiation diagnostic apparatus comprising: a means; and means for obtaining an image according to the ratio.