JP2001346795A - Method of evaluating alignment between x-ray source and scattered ray removing grid, and feedback method, feedback device, x-ray radiography and x-ray radiographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminating the need for a hardware and evaluate the accuracy of alignment even if an obstacle exists between a grid cassette and a X-ray source. SOLUTION: This alignment evaluating method for evaluating the accuracy of alignment between the X-ray source and a scattered X-ray removing grid comprises a radiography step (S1) of radiographing a X-ray image, a computation step (S2) of computing the contrast of the scattered X-ray removing grid for every region on the radiographed X-ray image, and evaluation steps (S3, S4) of analyzing the profile of the computed contrast and evaluating the accuracy of alignment between the X-ray source and the scattered X-ray removing grid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment evaluation method and a feedback method for evaluating the alignment accuracy between an X-ray source and a scattered X-ray removal grid in an X-ray imaging apparatus, a feedback apparatus, an X-ray imaging method, and an X-ray imaging method. X-ray imaging apparatus, more particularly, a method for evaluating the alignment and feedback of the X-ray source and the scattered X-ray removal grid in an X-ray imaging apparatus using a scattered X-ray removal grid to reduce the scattering effect on the image, The present invention relates to a feedback device, an X-ray imaging method for performing X-ray imaging using the positioning evaluation method, and an X-ray imaging device.

[0002]

2. Description of the Related Art It is a conventional problem to reduce the amount of scattered radiation detected in X-ray projection. This is, for example, chest X
This is because in the line projection, the scattered radiation occupies 30 to 50% of the detected X-rays, so that the image quality is significantly reduced. There are three basic methods for reducing the effects of scattered radiation on images obtained by two-dimensional X-ray photography. One is to use an anti-scatter grid between the subject and the sensor, the other is to use an air gap between the subject and the sensor, and the other is to estimate the scattered dose theoretically, This is a method of subtracting the estimated scattering dose. Among them, a method that is more frequently used than the other two methods is a method that uses a scattered radiation removal grid between a sensor and a subject under inspection in order to preferentially attenuate scattered radiation.

[0003] The scattered radiation removal grid is usually composed of a large number of flat lead foils (scepters) made of lead or the like.
The scepter is tilted so that the point where the X-ray source (X-ray tube) is installed is focused. X-rays not scattered in the subject (primary X-rays) pass through the grid and reach the sensor. Due to the effect of the grid means to collimate the X-rays, ie preferentially absorbing the X-rays scattered by the patient (ie traveling in a different range of angular directions than the primary X-rays), the scattered X-ray flux The ratio is greatly reduced. However, intermediate materials such as aluminum also have a damping effect, and there is a limit to reducing the thickness of the septa,
The primary X-ray flux also decreases. Therefore, the grid is designed and selected based on a trade-off between maximizing the transmission of primary photons and minimizing the transmission of scattered photons.

[0004]

The amount of transmission of primary X-rays is
If the X-ray source is not located at the focus of the septum, i.e. the focus of the grid, it will still be greatly reduced. This means that the portable radiography apparatus has a scattered radiation removal grid, as reported in the bedside radiography, where it is reported that the positioning is performed with an error of 3 ° or more in a maximum of 50% of cases. This is an important issue when using. Usually, alignment is left to the skill of the technician, and neither initial alignment assistance nor quick feedback on alignment accuracy based on the obtained images is provided. The barely available feedback is that the image has been developed and confirmed, and a retake is requested. A series of procedures of the X-ray imaging will be described with reference to a flowchart of FIG.

[0005] First, an X-ray apparatus is set according to the patient (step S10), and X-ray imaging is performed (step S1).
1) Return the X-ray apparatus to its original position (step S12),
Develop and evaluate the captured X-ray image (Step S1)
3). As a result of the evaluation, if re-imaging is not necessary (NO in step S14), the process is terminated as it is, but if re-imaging is necessary (YES in step S14), the process returns to step S10, and the X-ray apparatus setting X Redo the radiography.

Since it takes time to develop and evaluate the X-ray image performed in step S13, re-imaging is requested a while after the first imaging is performed. When a re-imaging is requested, the patient has to be searched for and recalled, and the re-imaging must be arranged such as moving or setting the X-ray apparatus, so that time is wasted. Also, even if you re-photograph in this way,
There are no systems to prevent the same or similar misalignment. Therefore, it was difficult for an engineer to learn the alignment technique based on experience.

As described above, positioning is an important problem in a portable X-ray imaging apparatus in which the grid sensor and the X-ray source are not fixed. Appropriate evaluation of alignment is required.

Several methods have been proposed to assist in alignment, some of which are suitable only for the purpose of system installation or for periodic quality checks. These methods for assessing the alignment of the X-ray source and the sensor grid are based on visible light or X-rays.
This can be done using wires or by a mechanical coupling device. A typical optical system has a laser attached to an X-ray source for irradiating a beam of light horizontal to a main X-ray beam. Also, the main X
A configuration is disclosed in which a laser beam is detected by a sensor attached to a line sensor to estimate or determine an incident angle so as to be within a predetermined angle. In another configuration, the optical reflection configuration is permanently or temporarily fixed to the grid cassette, and when an incident spot light is incident on the optical reflection configuration, the reflected spot light indicates correct alignment. Although the above method has been described for the case of using a portable X-ray imaging apparatus, the same system is used when a system in which the X-ray source (X-ray tube) -X-ray detection configuration is fixed is installed. It is possible to use

However, systems using optical images have two major problems. One is that a laser attached to each X-ray source or the like and an additional device such as a device attached to a grid sensor are required. 2
Second, there must be no obstructions between the sensor mounting location and the laser, making it difficult to place the sensor behind the patient. If there is an obstacle between the sensor and the laser, the alignment cannot be evaluated. Similar drawbacks have been observed in systems that use physical connections between the cassette and the X-ray source to ensure proper distance and angle alignment.

There is also a method using X-rays. this is,
This is a method of analyzing an X-ray image to evaluate the alignment between the X-ray source and the grid cassette. As one of such methods, a method using a profile of an X-ray image captured in a state where no object exists between the grid cassette and the X-ray source has been proposed. The evaluation of the distance between the X-ray source and the sensor is performed by comparing the average pixel value at the center of the image with the average pixel value at the end of the image. The state of the angle adjustment can be evaluated from the shape of the profile of the image. Such a method has the advantage that no additional hardware is required, but it is effective in the installation and quality check of a fixed positioning system, but when there is an object that blocks between the X-ray source and the cassette. There is a problem that it is not suitable.

However, alignment aids or mechanical additions based on optical methods have little application, particularly where alignment is most difficult (eg, a large patient).

[0012] The present invention has been made in view of the above problems, and does not require additional hardware, and evaluates the positioning accuracy even when there is an obstacle between the grid cassette and the X-ray source. It is a first object to provide a method that can do this.

A second object is to provide information for positioning the system based on the evaluation result.

It is a third object of the present invention to promptly report to the user the evaluation of the arrangement state of the system and promptly warn of the need for re-shooting.

[0015]

In order to achieve the first object, a positioning evaluation method of the present invention for evaluating the positioning accuracy between an X-ray source and a scattered X-ray removal grid is provided. A photographing step of photographing, a calculating step of calculating the contrast of the scattered X-ray removal grid for each predetermined region of the photographed X-ray image, and analyzing the profile of the calculated difference to obtain the X-ray source and the scattered X-ray. And evaluating an alignment accuracy between the removal grids.

Further, the X-ray imaging apparatus of the present invention for evaluating the positioning accuracy between the X-ray source and the scattered X-ray removal grid is provided by an X-ray imaging apparatus.
Imaging means for capturing a line image; calculating means for calculating the contrast of the scattered X-ray removal grid for each predetermined area of the captured X-ray image; and analyzing the calculated difference profile to obtain the X-ray source. Evaluation means for evaluating the positioning accuracy between the scattered X-ray removal grids.

According to a preferred aspect of the present invention, in the evaluation step, when the profile is a curve, the X
Assessing that the alignment between the source and the scattered X-ray removal grid is shifted in the vertical direction, and when the profile is a curve, adjusting the alignment between the X-ray source and the scattered X-ray removal grid. Is evaluated as being shifted in the vertical direction.

Further, according to a preferred aspect of the present invention, in the evaluation step, when the profile is bilaterally asymmetric, it is evaluated that the profile is displaced in the horizontal direction, and the evaluation unit determines that the profile is bilaterally asymmetric. If it is, it is evaluated that it is shifted in the horizontal direction.

According to a preferred aspect of the present invention, in the evaluation step, the evaluation is performed by comparing the profile with a reference value, and the evaluation means compares the profile with a reference value. Perform an evaluation.

In the evaluation step, different reference values are used in accordance with the spectrum of the X-rays emitted from the X-ray source and the characteristics of the scattered X-ray removal grid. Different reference values are used in accordance with the spectrum of the X-rays irradiated from the device and the characteristics of the scattered X-ray removal grid.

According to a preferred aspect of the present invention, the reference value is based on a measured value obtained by using the same or similar scattered X-ray elimination grid used in the alignment evaluation. Value.

According to a preferred aspect of the present invention, the reference value is a value based on a measurement value obtained in substantially the same X-ray spectrum state as the X-ray spectrum used in the alignment evaluation. .

According to a preferred aspect of the present invention, the reference value is a value based on a measurement value obtained by using the same or similar X-ray sensor as the X-ray sensor used in the alignment evaluation. It is.

Preferably, a plurality of reference values based on measurement values obtained for different X-ray spectrum states and different specifications of the scattered X-ray removal grid are held as a look-up table.

According to a preferred aspect of the present invention, in the calculating step, the contrast is calculated directly using an X-ray image, and the calculating means calculates the contrast directly using the X-ray image. I do.

According to another preferred embodiment of the present invention, in the calculating step, the contrast is calculated by using a spatial frequency spectrum converted from the X-ray image, and the calculating means includes: The contrast is calculated using the spatial frequency spectrum converted from.

Preferably, in the calculating step, the spatial frequency spectrum is obtained by Fourier-transforming the logarithm of the X-ray image, and the calculating means performs a Fourier transform on the logarithm of the X-ray image to convert the spatial frequency spectrum. obtain.

According to a preferred aspect of the present invention, the spatial frequency spectrum is calculated for at least two regions of the X-ray image.

According to a preferred aspect of the present invention, the predetermined regions for calculating the contrast are at least two regions, and preferably, the two regions are an end portion and a center portion of the X-ray image. .

According to a preferred aspect of the present invention, in the evaluation step, the evaluation is performed based on a ratio or a difference between the contrasts at an edge portion and a center portion of the image. The evaluation is performed based on the ratio or difference of the contrast between the part and the center part.

According to a preferred aspect of the present invention, in the evaluation step, at least one of a direction of the alignment error and a degree of the alignment error is evaluated, and the evaluation unit determines the alignment error. And / or at least one of the degree of alignment error.

In order to achieve the second object,
The alignment evaluation method further includes a display step of displaying the alignment accuracy evaluated in the evaluation step, and the X-ray imaging apparatus further includes a display unit that displays the alignment accuracy evaluated by the evaluation unit.

Further, in order to achieve the third object, positioning of the X-ray source and the scattered X-ray removal grid in X-ray imaging by an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid The accuracy feedback method includes an evaluation step of evaluating the alignment accuracy between the X-ray source and the scattered X-ray removal grid based on an X-ray image captured by the X-ray imaging apparatus, and an evaluation in the evaluation step. And a display step of displaying the positioning accuracy based on the information.

Further, in the X-ray imaging by the X-ray imaging means having an X-ray source and a scattered X-ray removal grid, a feedback device for positioning accuracy of the X-ray source and the scattered X-ray removal grid is provided. Evaluation means for evaluating the alignment accuracy between the X-ray source and the scattered X-ray removal grid based on the X-ray image captured by the method, and display means for displaying the alignment accuracy based on the evaluation of the evaluation means. Have.

Preferably, the feedback method comprises: a judging step of judging whether re-imaging is necessary based on the evaluation in the evaluating step; and, if the judging step determines that re-imaging is necessary, And a notifying step for notifying that effect, wherein the evaluation step is started immediately after the imaging by the X-ray imaging apparatus, and the feedback apparatus needs re-imaging based on the evaluation of the evaluation means. Determining means for determining whether or not re-imaging is necessary by the determining means; and notifying means for notifying the user that the re-imaging is necessary. Evaluation starts immediately after shooting by.

An X-ray imaging method using an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid includes an imaging step of capturing an X-ray image, and an X-ray imaging method based on the captured X-ray image. An evaluation step of evaluating the alignment accuracy between the radiation source and the scattered X-ray removal grid; a determination step of determining whether or not re-imaging is necessary based on the evaluation in the evaluation step; And adjusting the position of the X-ray source and the scattered X-ray removal grid based on the evaluation when it is determined that the X-ray source is necessary.

Further, an X-ray imaging apparatus using an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid comprises: an imaging means for imaging an X-ray image; An evaluation unit for evaluating the positioning accuracy between the radiation source and the scattered X-ray removal grid, and a determination unit for determining whether re-imaging is necessary based on the evaluation by the evaluation unit.

Preferably, in the X-ray imaging method, a display step of displaying positioning accuracy based on the evaluation in the evaluation step, and a step in which it is determined that re-imaging is necessary in the determination step. Notification step, a step of repeating the imaging step, and a step of returning the X-ray source and the scattered X-ray removal grid to the initial position when the determination step determines that re-imaging is not necessary. The evaluation step is started immediately after the imaging step, and the X-ray imaging apparatus re-displays the positioning accuracy based on the evaluation by the evaluation means and the determination means. When it is determined that imaging is necessary, a notifying unit for notifying that, and when the determining unit determines that re-imaging is not required, the X-ray source and the scattered X-ray removal grid are moved to the initial position. To Further comprising a to means, said evaluating means starts the evaluation immediately after photographing by the photographing means.

According to a preferred aspect of the present invention, in the evaluation step, at least one of the direction of the alignment error and the degree of the alignment error is evaluated, and the evaluation means evaluates the alignment error. At least one of the direction and the degree of alignment error is evaluated.

Further, according to a preferred aspect of the present invention, in the display step, at least one of a direction of the alignment error and a degree of the alignment error is displayed, and the display means includes: At least one of the direction of the error and the degree of the alignment error is displayed.

According to a preferred aspect of the present invention, in the evaluation step, the characteristic of the scattered X-ray removal grid to be recommended is further determined on the basis of the evaluated alignment accuracy, and in the display step, the characteristic is recommended. The characteristic of the scattered X-ray removal grid is further displayed, and the evaluation means further determines the recommended characteristic of the scattered X-ray removal grid based on the evaluated alignment accuracy. Further display the properties of the removal grid.

Preferably, the characteristics of the scattered X-ray removal grid are determined according to the type of examination for performing X-ray photography.

Preferably, in the display step, display is performed using at least one of a graphic image and a text image, and the display means displays at least one of a graphic image and a text image.

[0044] More preferably, in the display step, the X-ray image obtained in the imaging step is further displayed, and the display means further displays the X-ray image obtained in the imaging means.

According to a preferred aspect of the present invention, in the notifying step, the notification is performed by at least one of a visual notification and an auditory notification.
The notification is performed by at least one of a visual notification and an audible notification.

According to a preferred aspect of the present invention, in the determining step, the evaluation value of the positioning accuracy is compared with a predetermined level, and if the value is lower than the predetermined level, it is determined that re-imaging is necessary. The determination unit compares the evaluation value of the positioning accuracy with a predetermined level, and determines that re-imaging is necessary when the evaluation value is equal to or lower than the predetermined level.

Preferably, the predetermined level is determined based on characteristics of the scattered X-ray removal grid. Also,
Preferably, the characteristics of the scattered X-ray removal grid include at least one of a grid density, a grid ratio, a focal length, a material of a septum, and a material between lead foils.

[0048] More preferably, said predetermined level is determined for each of the different characteristics of said scattered X-ray removal grid.
Store as a lookup table.

According to a preferred aspect of the present invention, the adjusting step is automatically performed.

According to another preferred embodiment of the present invention, the adjusting step is performed manually.

According to a preferred aspect of the present invention, when the determination means determines that re-imaging is necessary, the X-ray imaging apparatus automatically performs the X-ray imaging based on the evaluation. There is further provided adjusting means for adjusting the alignment between the source and the scattered X-ray removal grid.

According to the above-described configuration, it is possible to save time and perform re-photographing with a more accurate position setting as compared with the conventional system in which the setting must be repeated from the beginning when re-photographing is performed. be able to. It also helps technicians to acquire technology empirically.

[0053]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) In a first embodiment of the present invention, a method for evaluating the alignment between the X-ray source 5 and the grid 9 by analyzing an X-ray image will be described. Book first
The apparatus according to the embodiment of the present invention is usually used for acquiring an X-ray image, and as shown in FIGS.
And a scattered X-ray removal grid 9 having a preset focal length, and a two-dimensional X-ray sensor 10.
Reference numeral 8 denotes a subject.

In the evaluation method according to the first embodiment of the present invention, the subject 8 may be arranged between the X-ray source 5 and the scattered X-ray removal grid 9. In addition, the two-dimensional X-ray sensor 10
For example, a digital X-ray detector such as an amorphous silicon flat panel sensor having a fluorescent screen is used, but a film screen or another sensor can also be used.

In the evaluation method according to the present invention, the grid 9
Is evaluated based on the analysis result of the X-ray image. The X-ray image is first used to calculate a difference between the maximum transmittance and the minimum transmittance for each predetermined region in a direction perpendicular to the direction of the grid sceptor 12. Hereinafter, the difference between the maximum and minimum transmittances is referred to as “grid contrast”. The grid contrast differs at each position of the image, and is characterized by the characteristics of the grid 9, the state of the spectrum of the X-ray emitted from the X-ray source 5, and the alignment between the X-ray source 5 and the grid 9. Hereinafter, the characteristics according to the alignment state will be described below with reference to FIGS. 2 and 3.

FIGS. 2 and 3 are diagrams for explaining a case where the arrangement state of the X-ray source 5 and the scattered X-ray removal grid 9 are shifted in different directions, that is, in the horizontal and vertical directions. 2 and 3, reference numeral 6 denotes a focal point of the grid 9.

Although there are differences depending on the combination of detector and grid type, when properly aligned, grid contrast is constant or nearly constant over the entire image. On the other hand, as indicated by 11 in FIG.
When the distance between the X-ray source 5 and the grid 9 is different from the focal length of the grid 9 in the direction perpendicular to the plane of the grid 9, the grid contrast becomes different toward the edge of the image. Further, as indicated by 7 in FIG. 2, even when the X-ray source 5 is at the focal plane of the grid 9 and the distance to the grid 9 in the vertical direction is appropriate, when the X-ray source 5 is out of the focal point of the grid 9, , The grid contrast of the entire image is still not constant.

As described above, the shape and value of the grid contrast indicate the state of alignment. Therefore, by comparing the measured grid contrast with the standard value and evaluating the shape of the grid contrast of the entire image, it is possible to measure the alignment accuracy in two directions, the horizontal direction and the vertical direction. That is, the evaluation method in the first embodiment is based on the fact that the grid contrast depends on the alignment state of the system.

The reason why the grid contrast depends on the alignment state of the system will be described in detail with reference to FIG. The grid 9 is composed of a plurality of septa 12, and a point where the X-ray source 5 is to be installed (ie, FIG. 2 and FIG. 3) so that primary X-rays (X-rays not scattered by the subject 8) pass through the grid 9 best. Each is mounted at an angle toward the focal point 6) in FIG. When fully aligned, the angle of incidence of this primary X-ray is
Is the same as the angle of the scepter 12. FIG. 4A shows the primary X-ray incident state, the analog profile, the pixel array, and the digital profile obtained by the pixel array when properly aligned. Profile is
Since the incident angle becomes narrower as approaching the end of the image, the X-ray incident intensity is slightly reduced due to the incident angle, but is substantially constant over the entire image.

On the other hand, as shown in FIG.
When the source 5 is not set at the focal point 6 of the grid 9, the incident angle of the primary X-ray with respect to the grid 9 is
This manifests itself as a change in the shape of the image profile. This change in shape differs depending on the alignment error, the shape of the grid, and the like.

For example, when there is an error 11 in the vertical direction as shown in FIG. 3, the incident angle of the X-ray at the center of the image does not change, and the measured grid contrast at the center of the image is properly aligned. It will be the same as if done.
However, the difference between the incident angle of the X-rays and the inclination angle of the septum 12 increases as the distance from the center of the image (the center of the grid 9) increases, and a corresponding change appears in the grid contrast profile. This effect is symmetric, and a similar shift will appear in opposite directions about the grid 9 respectively.

Further, as shown in FIG.
The effect is not symmetric about the center,
The difference between the incident angle of the X-rays and the inclination angle of the septa 12 appears as a profile in which the grid contrast is different at all positions. That is, the profile when there is an error in the horizontal direction is completely different from the profile in the state where the alignment is properly performed and the profile in the case where there is an error in the vertical direction.

Next, the procedure of the evaluation method in the first embodiment of the present invention utilizing the above features will be described.

FIG. 1 is a flowchart showing the procedure of an evaluation method based on X-ray image analysis according to the first embodiment of the present invention.

First, in step S1, the sensor 10
To capture an X-ray image. When taking an image, an appropriate voltage applied to the X-ray source (X-ray tube) is selected, and the voltage
Take a line image. For example, a lung examination may be performed at a tube voltage of 100 kVp. The sensor 10
If is a film screen system, the film must be digitized.

Next, in step S2, a grid contrast of the photographed X-ray image is created. Here, a profile indicating a change in the amount of X-ray transmitted through the grid 9 is created in a direction perpendicular to the direction of the grid scepter 12 over the entire image captured by the sensor 10. Here, a grid contrast profile is created as described above. First, the concept of grid contrast creation will be described.

When the position of a pixel in one direction of an image for which grid contrast is to be created is x, I (x)
X-ray flux that receives light at a certain pixel x in the sensor 10,
If B (x) is an X-ray flux at a position above the X-ray source corresponding to the pixel x (on the X-ray source side) and G (x) is the transmittance of the grid 9 corresponding to the pixel x, I (x) = B (X) G
(X). Using this, G (x) is set for each predetermined pixel number area of the sensor 10 in the image profile.
Find the contrast of This is called "grid contrast". Here, the grid contrast is a difference between the maximum value and the minimum value of G (x) for each predetermined number of pixels, but is not necessarily limited to this.

In the fully aligned state, G
The minimum value of (x) corresponds to a value obtained from a pixel including a region where X-rays are blocked by the septum 12 (typically, lead), and G
The maximum value of (x) corresponds to a value obtained from a pixel that receives only X-rays that pass through the space 13 (usually aluminum) between the septa 12 in the grid 9. In contrast,
For example, when the grid 9 is displaced in the vertical direction as shown in FIG.
Since the area where X-rays are blocked by 2 is widened, the amount of X-ray entering a certain pixel x is small, and the value obtained from the pixel x is low. Therefore, the minimum value of G (x) will be lower than in the fully aligned state. Furthermore, depending on the inclination angle of the septum 12 and the incident angle of X-rays,
In some cases, X-rays passing only through the space 13 may not exist, in which case the maximum value of G (x) becomes low. As described above, when the alignment is completely performed, the grid contrast becomes substantially constant, but when the alignment is inappropriate, the grid contrast changes.

Specifically, the direct space analysis method (ie,
Grid contrast is created by using one of the method using the image itself) and the spatial frequency analysis method. First, the direct spatial analysis method will be described.

The spatial variation of the signal, which is large enough to be unaffected by the grid contrast pattern and in one direction of the detected X-ray field, is caused by the spatial variation of the X-ray field created by the X-ray source 5. Object 8 existing between the X-ray source 5 and the grid 9 so that the variation
Calculate the average pixel value (moving average) for each predetermined region (predetermined number of pixels) small enough not to affect the created profile, and A grid transmission image (normalized image) can be obtained by dividing by the average pixel value of the included predetermined region. This is the simplest method, and is more suitable when the subject 8 does not exist between the X-ray source 5 and the scattered X-ray removal grid 9.

FIG. 5 shows a 100 μm pixel, 60 lines / pixel.
3 shows an example of a profile obtained by simulation using a cm sensor. By calculating the maximum value-minimum value for each predetermined area based on such a graph, the grid contrast is calculated over the entire image in a direction perpendicular to the direction of the grid sceptor 12. As an example of the method of the present invention, the calculation is performed every 1 mm. Alternatively, the calculation may be performed only for the center part and the end part of the image.

A contrast image may be generated by dividing each pixel value by a value obtained by applying a polynomial function expression or another relational expression to the pixel value of the local image. In this case, in detail, the above-mentioned relational expression may be such that the result of the division indicates the grid contrast of the relevant portion and is as independent as possible from the above factors such as the heel effect and the presence of the subject.

Further, the above-described division is performed for each pixel and then averaged over a plurality of rows (a direction horizontal to the direction of the grid septa 12), or the original image is first divided into a plurality of rows before calculating the profile. By averaging over, S /
A profile with a high N ratio can be obtained. In this case, the number of rows to be averaged depends on the improvement of the S / N ratio and the grid 9
Is determined in consideration of the expansion of the influence of the angle error in the installation of the camera. The same can be said for the spatial frequency analysis method described below.

Next, the spatial frequency analysis method will be described. As an example of this method, the logarithm of the image is converted using, for example, a Fourier transform method.

The X-ray profile corresponding to the grid is represented by B
(X) If the transmittance of the grid is G (x), the logarithm of the image is log (I (x)) = since the image profile is given by I (x) = B (x) G (x). log (B (x)) + log (G
(X))

Is given by Accordingly, if the frequency of the peak in the spatial frequency spectrum with respect to the change in the transmittance of the scattered X-ray removal grid 9 is such that there is no background or the background is at a small frequency, the scattered X
The peak and background in the spatial frequency spectrum for the change in transmittance of the line removal grid 9 can be distinguished, and the height of the peak can be used as a measure of the grid transmittance. Since its height is proportional to the above-mentioned grid contrast, it can be used as grid contrast. FIG. 8 shows this. Frequency spectra are calculated for various regions in the image profile. In one example, a 128 pixel wide area (ie, 1
For a 00 μm pixel, a 12.8 mm area) is used
The spectrum and analysis are evaluated every 1 mm. However, such detailed analysis is usually not required and coarse intervals may be sufficient.
In addition, it is only necessary to perform analysis on one end and the central part of the image, which is effective when calculation speed is important.

An example of the profile obtained by the above method is shown in FIGS. The profiles shown in FIGS. 7 and 8 are examples using a detector of 100 μm pixels (the resolution of the detector is determined by the pixel configuration) and a grid of scattered X-rays of 60 lines / cm. ±
5 shows an example of a profile between 5 cm. Note that the y-axis in FIGS. 7 and 8 indicates the grid contrast, and the higher the value, the higher the value. Also, the results shown in FIGS. 7 and 8 are for explanation, and it goes without saying that the analysis of the alignment based on the change in the grid contrast can be applied to detectors of other specifications.

Next, in steps S3 and S4, the detected grid contrast is analyzed, and the alignment between the X-ray source 5 and the grid 9 is evaluated. When the X-ray source 5 and the grid 9 are properly aligned, the straight lines 501 and 601 in FIGS. 7 and 8 are used, although the profile of the grid contrast is strictly dependent on the grid design and the X-ray spectrum. As shown, it is constant or nearly constant over the entire image.

On the other hand, when the distance between the X-ray source 5 and the grid 9 is longer or shorter than the focal length of the grid as shown in FIG. 3, the grid contrast becomes a U-shaped curve 502 as shown in FIG. Become. As this shape approaches a straight line, the distance between the X-ray source 5 and the grid 9 and the focal length of the grid 9 are more appropriately matched.

Therefore, in step S3, the degree of the obtained curve of the grid contrast is evaluated.

Even if the positions of the X-ray source 5 and the grid 9 are correctly aligned in the vertical direction, if the horizontal alignment is not appropriate as shown in FIG.
602 and 603 indicate that the value of the grid contrast increases. In this case, the change in contrast level can be used to indicate a horizontal alignment error. The larger the difference between the ideal contrast value calculated in a certain X-ray spectrum and the actual contrast value, the more inappropriate the horizontal alignment is. The direction of the error (i.e., right or left, which can be expressed as the +,-direction of the x direction) is the profile of the profile as shown by line 603 in FIG. 8 for a very poor horizontal alignment. It can be evaluated from asymmetry. That is, in general, the less asymmetry on either side of the grid center of the contrast profile, the less appropriate the horizontal alignment. In this way, by comparing with the profile measured in advance, it is evaluated whether the improper alignment is caused by an error in the right direction or an error in the left direction (that is, in the + direction or the − direction). be able to.

As described above, in step S4, the alignment is evaluated by comparing the contrast profile with the profile (standard profile) measured in advance.

In the digital system, the measured G (x) is affected by the sampling effect. The above discussion can be said about the measured value G (x) when the pixel size is not small enough to cause a change in transmission due to the grid 9.

As described above, according to the first embodiment, it is possible to evaluate the alignment accuracy without adding hardware even if there is an obstacle between the grid cassette and the X-ray source. Can be.

The evaluation method described in the first embodiment can be used to evaluate the positioning accuracy between the installed X-ray source and the grid. This evaluation can be performed in various ways. In one example, two alignment evaluation values are calculated. One evaluation value is the difference or ratio of the grid contrast calculated at one end of the image and the center of the image, and is an evaluation value for the accuracy of the vertical distance between the X-ray source 5 and the grid 9 cassette. , Or a vertical alignment evaluation value. When the difference is zero or the ratio is 1, it indicates a perfect alignment state in the same direction. The other evaluation value is obtained by comparison with a standard profile or the like, and it is possible to calculate a class or a specific distance.

Another example that can be used with the method described above is that the difference or ratio between the calculated grid contrast value and the nominal value for the same grid 9 under the same spectral conditions with proper alignment. Is used as an evaluation value of the accuracy of the horizontal distance between the X-ray source 5 and the grid 9 cassette or an evaluation value of the horizontal alignment, and when the difference is zero or the ratio is 1, the value in the same direction is used. Indicates perfect alignment. This method is effective at the center of the grid 9 image. Depending on the combination of sensor and grid,
Grid contrast profile shapes can also be used.

The first embodiment is for specifically describing the present invention. For example, a change in grid contrast is determined by an X-ray system (including a sensor).
And the design of the grid. Therefore, different systems will make different changes.

(Second Embodiment) In the second embodiment, a user interface for notifying a user of the position of the X-ray imaging system is provided.
The user interface will allow the user to improve the alignment based on the analysis of the system's alignment using X-ray images,
Further, an instruction is given as to whether re-imaging is necessary.

FIG. 9 is a diagram showing the configuration of an X-ray imaging system according to the second embodiment. In FIG. 9, 31
Is an X-ray tube as an X-ray source, 32 is a wide X-ray beam emitted from the X-ray tube 32, 33 is a subject, a patient in this case, 34 is a scattered radiation removal grid, and 35 is a two-dimensional X-ray detector. 36, an image capture circuit; 37, a preprocessing circuit;
8 is a CPU, 39 is a main memory, 40 is an operation panel, and 41 is a display.

In the above configuration, the patient 33 is
Irradiated by a wide X-ray beam 32 emitted from
The X-rays that have passed through the patient 33 and the scattered radiation removal grid 34 enter a two-dimensional X-ray detector 35, and form an electric two-dimensional X-ray image. The image signal obtained from the detector 35 is passed to a pre-processing circuit 37 via an image capture circuit 36, and is subjected to pre-processing such as offset correction and gain correction. Thereafter, the processed image is under the control of the CPU 38.
It is stored in the main memory 39. The following processes described in the second embodiment are all performed using images stored in the main memory 39. Control by the user is performed via the operation panel 40, and visual feedback to the user is performed via the display 41.

A series of procedures of X-ray imaging by the X-ray imaging system having the above configuration will be described with reference to the flowchart of FIG.

First, an X-ray apparatus is set in accordance with the patient (step S10), and X-ray imaging is performed (step S1).
1) Immediately, the X-ray tube 31 and the scattered X-ray removal grid 34
Is automatically evaluated (step S15).
As a result, when it is determined that the alignment between the X-ray tube 31 and the scattered X-ray removal grid 34 is appropriate (step S1).
(NO in 6), and at that stage, the X-ray apparatus is returned to the original position (step S17), and the process is terminated. However, if it is determined that re-imaging is necessary due to insufficient alignment, the position of the X-ray tube is adjusted by the drive unit 42 (step S18), and the process returns to step S11 to perform imaging again. Do. As an example of the case where the positioning is inappropriate, there is one described in the first embodiment with reference to FIGS. 2 and 3.

Next, with reference to FIG. 11, a more detailed operation including the judgment in step S16 after performing the alignment evaluation in step S15 of FIG. 10 will be described.

In step S15 in FIG. 10, an automatic evaluation of the alignment of the system is performed.
It starts by capturing a line image and is based on analysis of the X-ray image itself. Some examples of specific analysis methods are shown below.

(A) A method of analyzing variations in grid contrast over the entire image.

(B) A method of analyzing the position and shape of an X-ray shadow of an additional object attached to a normal grid. The position of the X-ray source can be calculated.

(C) A method of analyzing an average gray scale variation in an image area where there is no obstacle between the sensor and the X-ray source.

When the evaluation is completed, a calculation for dividing the evaluation into grades is performed in step S21 of FIG. 11, and the calculated result is displayed to the user. This is basically a result of converting the result obtained in step S15 in FIG. 10 into a user-friendly class such as “1” to “5”. Here "5"
Indicates that the alignment is perfect, and "1" indicates that the alignment is very inappropriate. Step S1
Depending on the method used in 5, the following two grades can be used.

(A) Grade proportional to vertical movement

(B) Grade proportional to horizontal movement

In step S21, without dividing the evaluation into grades,
It is also possible to display to the user the distance and direction in which the X-ray source should move.

Since the importance of vertical movement and horizontal movement required for re-photographing is different, the proportional constant of each scale is different. In addition, it is possible to calculate a class and a specific distance by comparing with a standard profile. One example of an interface used for vertical and / or horizontal alignment is shown in FIG. In FIG. 12, if -10 to +10 are minus, they are in the minus direction (for example, left or down), and if plus, they are plus (for example, right or up). The distance for moving the X-ray tube 31 is shown in FIG. In the example shown in FIG. 12, since the arrow points to about +2.5 cm, it indicates that moving the X-ray source 31 to the right or upward by about 2.5 cm will provide appropriate alignment accuracy.

In step S22, using the result obtained in step S15 and a look-up table, an example of which is shown in FIG. 13, the range of the grid characteristics (grid ratio, grid density) allowed in this alignment is determined. Inform the user using any stage display. In this step, a grid is selected based on the predicted level of the scattered X-rays, and the level is determined based on the type of examination (for example, imaging part (chest, etc.), imaging position (front / side, etc.), X-ray generation conditions ( It is necessary to determine what kind of inspection is to be performed because of the dependence on the tube voltage.

The look-up table in FIG. 13 shows the maximum grid ratio (ratio of grid septum width to septum height) for obtaining an image in an allowable range when the system is in a certain state of alignment. Note that other grid specifications may be indicated. The number of columns and rows of such a look-up table will vary with the number of x-ray systems, sensors, and grid types used.

FIG. 14 shows an example of a graphic image used for feeding back the positioning accuracy to the user.
Shown in In this example, the allowable range of the grid ratio is shown. The feedback shown in FIG. 12 and FIG.
As shown in FIG. 5, it can be displayed as a single graphic image or text image, and can be processed as a single process. Further, in order to easily show the direction and the degree of the positioning error, as shown in FIG.
May be displayed together with a graphic image indicating a positioning error. The X-ray image 91 is displayed at an appropriate angle so that the user can easily understand, for example, the left and right directions. In the second embodiment, the X-ray image is X
The display is made in a state where the patient is viewed from the tube so that the direction of the alignment error can be easily understood. In addition, a distinction may be made between posterior (PA) vision and anteroposterior (AP) vision indicating whether the X-rays have entered from the back side of the patient or from the opposite side.

In step S23, the result obtained in step S15 in FIG. 10 is compared with a preset level, and if the accuracy of the positioning is higher than the preset level, the process is terminated as it is, and In this case, a visual or audible warning is given to the user in step S24. Thereby, when re-imaging is likely to be necessary, the user's attention is paid to the visual information provided in steps S21 and S22. FIG. 17 shows an example of an image displayed as a warning on the user's screen.

Thus, the user compares the grid actually used with the grid range information displayed in step S22, and determines whether re-imaging is necessary.

According to the second embodiment, there is an advantage that the user does not need to input information. By clearly displaying the grids that are normally acceptable, with the measured alignment accuracy, the user only has to consider whether re-imaging is necessary and, if re-imaging is necessary, The positioning can be adjusted based on the instructions displayed in steps S21 and S22.

Further, when the user needs to re-take the image before returning the X-ray apparatus to the original position and before the patient is moved, the positioning accuracy is determined. Re-imaging can be performed appropriately and promptly without wasting time.

The user may input a grid type before shooting. In that case, based on the grid type and the measured alignment accuracy, refer to the lookup table that holds the relationship between the grid characteristics and the alignment accuracy, and the alignment accuracy exceeds the allowable range of the input type grid. Warn if you are. This look-up table may be similar to the one shown in FIG. 13 described above. FIG. 18 shows an example of the feedback graphic image displayed in this case. This feedback graphic image shows the allowed alignment range (depending on a number of factors, such as grid characteristics)
5 shows the alignment accuracy obtained from the most recently captured image.

Further, when the user performs a predetermined inspection, the same grid may always be used. For example, in the case of a chest examination, a grid having a grid ratio of 10: 1 is always used. In the second embodiment, the user does not enter the used grid type. This is because the grid type is estimated based on the test selection in the sensor control interface.

(Modification) In the second embodiment,
When it is detected that the positioning is inappropriate, a warning may be issued to the user, and then the X-ray tube may be automatically driven to an appropriate positioning position. FIG. 19 shows the system configuration in this case, and FIG. 20 shows the operation.

FIG. 19 shows the position of the X-ray tube as a grid 34.
Drive unit 42 that can be driven horizontally and vertically with respect to the surface of
Is different from the configuration in FIG. The other configuration is the same as the configuration in FIG.

The operations shown in the flowchart of FIG. 20 are the same as those already described with reference to FIG. 11 for steps S21 to S24, and therefore, description thereof will be omitted. If the positioning is inappropriate, step S25
Displays the positioning error in the vertical and horizontal directions, and further controls the drive unit 42 in steps S26 and S27 to move the X-ray tube 31 in the horizontal and vertical directions to the correct positioning position, respectively.

[0116]

Another object of the present invention is to supply a storage medium (or a recording medium) on which a program code of software for realizing the functions of the above-described embodiments is recorded to a system or apparatus, and to provide the system or apparatus. It is needless to say that the present invention can also be achieved by a computer (or CPU or MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes the present invention. When the computer executes the readout program codes, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instructions of the program codes. It goes without saying that a case where some or all of the actual processing is performed and the functions of the above-described embodiments are realized by the processing is also included.

Further, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the program code is read based on the instruction of the program code. , The CPU provided in the function expansion card or the function expansion unit performs part or all of the actual processing,
It goes without saying that a case where the function of the above-described embodiment is realized by the processing is also included.

When the present invention is applied to the above-mentioned storage medium, the storage medium includes the above-described FIG. 1, FIG. 10 and FIG.
Alternatively, a program code corresponding to the flowchart shown in FIG. 20 is stored.

[0119]

As described above, according to the present invention, it is not necessary to add hardware, and it is possible to evaluate the positioning accuracy even when there is an obstacle between the grid cassette and the X-ray source. A method can be provided.

Further, information for positioning the system can be provided based on the evaluation result.

Further, the user can be immediately notified of the evaluation regarding the arrangement state of the system, and can promptly warn of the need for re-imaging.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a positioning evaluation procedure of an X-ray imaging system according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a case where a positional relationship between an X-ray source and a grid is shifted in a horizontal direction.

FIG. 3 is a diagram illustrating a case where a positional relationship between an X-ray source and a grid is shifted in a vertical direction.

FIG. 4 is a diagram showing the relationship between the inclination of the scepter and the incident angle of X-rays in a state where the alignment is completely performed and a state where the alignment is inappropriate.

FIG. 5 is a diagram illustrating a profile of a grid image obtained by averaging pixel values in a partial region and correcting a change in X-ray flux.

FIG. 6 is a diagram showing a spatial frequency spectrum of an image when an object exists.

FIG. 7 is a diagram showing grid contrast profiles in a completely aligned state and a vertically misaligned state.

FIG. 8 is a diagram showing grid contrast profiles in a completely aligned state and a state in which the alignment is horizontally misaligned.

FIG. 9 is a block diagram illustrating a configuration of an X-ray imaging apparatus according to a second embodiment of the present invention.

FIG. 10 is a flowchart illustrating a series of procedures of X-ray imaging by the X-ray imaging system according to the second embodiment of the present invention.

FIG. 11 is a flowchart illustrating a more detailed operation of the operation shown in FIG. 10;

FIG. 12 is a vertical and / or vertical view according to the second embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of an interface used for horizontal alignment.

FIG. 13 is a diagram illustrating a look-up table indicating a range of a grid characteristic allowed in alignment according to the second embodiment of the present invention.

FIG. 14 is a diagram illustrating an example of an interface for indicating a grid characteristic in a range allowed by alignment accuracy according to the second embodiment of the present invention.

FIG. 15 is a diagram illustrating another example of an interface for indicating grid characteristics in a range allowed by the alignment accuracy according to the second embodiment of the present invention.

FIG. 16 is a diagram illustrating an example in which an X-ray image is displayed together with the image in FIG. 14;

FIG. 17 is a diagram illustrating an example of a warning image displayed when re-imaging is likely to be required.

FIG. 18 is a diagram illustrating an example of an interface indicating alignment accuracy when grid characteristics are input in advance according to the second embodiment of the present invention.

FIG. 19 shows X in a modification of the second embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a radiographic apparatus.

FIG. 20 shows X in a modification of the second embodiment of the present invention.
It is a flowchart which shows the detailed procedure of X-ray imaging by a radiography system.

FIG. 21 is a flowchart showing a series of procedures of X-ray imaging by a conventional X-ray imaging system.

[Explanation of symbols]

 Reference Signs List 5 X-ray source 6 Focus of grid 7 Horizontal error 8 Subject 10 is a two-dimensional X-ray sensor 9 Scattered X-ray removal grid 10 Two-dimensional X-ray detector 11 Vertical error 12 Septa 13 Space 31 X-ray tube 32 Wide X Ray beam 33 subject 34 scattered radiation removal grid 35 two-dimensional X-ray detector 36 image capture circuit 37 preprocessing circuit 38 CPU 39 main memory 40 operation panel 41 display 42 drive unit

Claims (71)

[Claims] 1. A positioning evaluation method for evaluating the positioning accuracy between an X-ray source and a scattered X-ray removal grid, comprising: an imaging step of capturing an X-ray image; A calculating step of calculating the scattered X-ray removal grid contrast, and analyzing the profile of the calculated contrast,
An evaluation step of evaluating alignment accuracy between the X-ray source and the scattered X-ray removal grid. 2. The evaluation step according to claim 1, wherein when the profile is a curve, the alignment between the X-ray source and the scattered X-ray removal grid is evaluated as being shifted in the vertical direction. Alignment evaluation method described in 1. 3. The alignment evaluation method according to claim 1, wherein in the evaluation step, when the profile is asymmetrical in the left-right direction, the profile is evaluated as being shifted in a horizontal direction. 4. The method according to claim 1, wherein in the evaluation step, the evaluation is performed by comparing the profile with a reference value. 5. The evaluation step according to claim 4, wherein different reference values are used according to the spectrum of the X-ray emitted from the X-ray source and the characteristics of the scattered X-ray removal grid. Alignment evaluation method. 6. The method according to claim 1, wherein the reference value is the same as or similar to the scattered X-ray removal grid used in the alignment evaluation.
The alignment evaluation method according to claim 5, wherein the value is a value based on a measurement value obtained using a line removal grid. 7. The method according to claim 5, wherein the reference value is a value based on a measurement value obtained in substantially the same X-ray spectrum state as the X-ray spectrum used in the alignment evaluation. The alignment evaluation method described. 8. The method according to claim 5, wherein the reference value is a value based on a measurement value obtained by using the same or similar X-ray sensor as that used in the alignment evaluation. 7. The alignment evaluation method according to any one of 7. 9. A plurality of reference values based on measured values obtained for different X-ray spectrum states and different specifications of the scattered X-ray removal grid are stored as a look-up table. The alignment evaluation method according to any one of the above. 10. The alignment evaluation method according to claim 1, wherein in the calculating step, the contrast is calculated by directly using an X-ray image. 11. The alignment evaluation method according to claim 1, wherein in the calculating step, the contrast is calculated using a spatial frequency spectrum converted from an X-ray image. 12. The method according to claim 11, wherein in the calculating step, the spatial frequency spectrum is obtained by Fourier-transforming the logarithm of the X-ray image. 13. The method according to claim 12, wherein the spatial frequency spectrum is
13. The method according to claim 11, wherein the calculation is performed for at least two regions of the line image. 14. The apparatus according to claim 1, wherein the predetermined areas for calculating the contrast are at least two areas.
14. The alignment evaluation method according to any one of claims 13 to 13. 15. The X-ray image according to claim 13, wherein the two regions are an end portion and a center portion of the X-ray image.
Alignment evaluation method described in 1. 16. The alignment evaluation method according to claim 15, wherein in the evaluation step, the evaluation is performed based on a ratio or a difference between the contrasts at an edge and a center of an image. 17. The alignment evaluation according to claim 1, wherein in the evaluation step, at least one of a direction of the alignment error and a degree of the alignment error is evaluated. Method. 18. The alignment evaluation method according to claim 1, further comprising a display step of displaying the alignment accuracy evaluated in said evaluation step. 19. An X-ray imaging apparatus for evaluating the positioning accuracy between an X-ray source and a scattered X-ray removal grid, comprising: an imaging unit for imaging an X-ray image; Calculating means for calculating the contrast of the scattered X-ray removal grid; analyzing the calculated profile of the contrast;
An X-ray imaging apparatus, comprising: an evaluation unit that evaluates the positioning accuracy between the X-ray source and the scattered X-ray removal grid. 20. The apparatus according to claim 19, wherein when the profile is a curve, the evaluation means evaluates that the alignment between the X-ray source and the scattered X-ray removal grid is vertically displaced. An X-ray imaging apparatus according to claim 1. 21. The X-ray imaging apparatus according to claim 19, wherein the evaluation unit evaluates that the profile is horizontally displaced when the profile is asymmetric. 22. The X-ray imaging apparatus according to claim 19, wherein the evaluation unit performs the evaluation by comparing the profile with a reference value. 23. The apparatus according to claim 22, wherein the evaluation means uses different reference values according to the spectrum of the X-ray emitted from the X-ray source and the characteristics of the scattered X-ray removal grid. X-ray imaging device. 24. The reference value is a value based on a measurement value obtained by using the same or similar scattered X-ray elimination grid used in the alignment evaluation and the same or similar scattered X-ray elimination grid. An X-ray imaging apparatus according to claim 23. 25. The method according to claim 23, wherein the reference value is a value based on a measurement value obtained in substantially the same X-ray spectrum state as the X-ray spectrum used in the alignment evaluation. The X-ray imaging apparatus according to claim 1. 26. The method according to claim 23, wherein the reference value is a value based on a measurement value obtained by using the same or similar X-ray sensor as that used in the alignment evaluation. 25. The X-ray imaging apparatus according to any one of 25. 27. The system according to claim 23, further comprising a look-up table holding a plurality of reference values based on measurement values obtained for different X-ray spectrum states and different specifications of the scattered X-ray removal grid. 2
7. The X-ray imaging apparatus according to any one of 6. 28. An X-ray imaging apparatus according to claim 19, wherein said calculating means calculates said contrast by directly using an X-ray image. 29. The X-ray imaging apparatus according to claim 19, wherein said calculating means calculates said contrast using a spatial frequency spectrum converted from an X-ray image. 30. The X-ray imaging apparatus according to claim 29, wherein the calculation unit obtains the spatial frequency spectrum by Fourier-transforming the logarithm of the X-ray image. 31. The spatial frequency spectrum is
31. The X-ray imaging apparatus according to claim 29, wherein the calculation is performed for at least two regions of the line image. 32. The predetermined area for calculating the contrast is at least two areas.
32. The X-ray imaging apparatus according to any one of 9 to 31. 33. The X-ray image according to claim 31, wherein the two regions are an end portion and a center portion of the X-ray image.
An X-ray imaging apparatus according to claim 1. 34. The X-ray imaging apparatus according to claim 33, wherein the evaluation unit performs the evaluation based on a ratio or a difference between the contrasts at an edge and a center of an image. 35. The X-ray imaging apparatus according to claim 19, wherein the evaluation unit evaluates at least one of a direction of the alignment error and a degree of the alignment error. apparatus. 36. The X-ray imaging apparatus according to claim 19, further comprising display means for displaying the positioning accuracy evaluated by said evaluation means. 37. A storage medium holding a program code for realizing the alignment evaluation method according to claim 1. 38. A feedback method for positioning accuracy of the X-ray source and the scattered X-ray removal grid in X-ray imaging by an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid, Based on the X-ray image taken by the imaging device,
A feedback method, comprising: an evaluation step of evaluating alignment accuracy between the X-ray source and the scattered X-ray removal grid; and a display step of displaying alignment accuracy based on the evaluation in the evaluation step. 39. A judging step of judging whether or not re-imaging is necessary based on the evaluation in the evaluation step, and, when it is judged by the judging step that re-imaging is necessary, notifying that effect. 39. The feedback method according to claim 38, further comprising a notification step, wherein the evaluation step is started immediately after imaging by the X-ray imaging apparatus. 40. An X-ray imaging method using an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid, comprising: an imaging step of capturing an X-ray image; X-ray source and scattered X
An evaluation step of evaluating alignment accuracy with the line removal grid; a determination step of determining whether re-imaging is necessary based on the evaluation in the evaluation step; and determining that re-imaging is required by the determination step Adjusting the position of the X-ray source and the scattered X-ray removal grid based on the evaluation. 41. A display step of displaying positioning accuracy based on the evaluation in the evaluation step, and a notification step of notifying that re-imaging is required by the determination step, Repeating the imaging step, and further comprising: returning the X-ray source and the scattered X-ray removal grid to an initial position when it is determined that re-imaging is not necessary in the determination step. 41. The X-ray imaging method according to claim 40, wherein the method is started immediately after the imaging step. 42. The evaluation step according to claim 38, wherein at least one of a direction of the alignment error and a degree of the alignment error is evaluated.
The method according to any of the above. 43. The method according to claim 38, wherein in said displaying step, at least one of a direction of the alignment error and a degree of the alignment error is displayed. . 44. In the evaluation step, a recommended characteristic of the scattered X-ray removal grid is further determined based on the evaluated alignment accuracy, and in the display step, the recommended characteristic of the scattered X-ray removal grid is further displayed. 42. A method according to claim 38, 39 or 41. 45. The characteristic of the scattered X-ray removal grid is as follows:
The method according to claim 44, wherein the determination is made according to the type of examination to be performed. 46. The display step according to claim 38, wherein the display is performed using at least one of a graphic image and a text image.
The method according to any of the above. 47. The method according to claim 38, wherein in the displaying step, an X-ray image obtained in the photographing step is further displayed. 48. The method according to claim 39, wherein, in the notifying step, the notification is performed by at least one of a visual notification and an audible notification. 49. The method according to claim 39, wherein in the determining step, the evaluation value of the positioning accuracy is compared with a predetermined level, and when the evaluation value is equal to or lower than the predetermined level, it is determined that re-imaging is necessary. The method according to any of the above. 50. The method according to claim 49, wherein the predetermined level is determined based on characteristics of the scattered X-ray removal grid. 51. The characteristic of the scattered X-ray removal grid is as follows:
Grid density, grid ratio, focal length, septum material,
The method according to claim 44, 45 or 50, comprising at least one of the following materials: 52. The method according to claim 52, wherein the predetermined level is different from the scattering X
A method according to claim 49 or claim 50, wherein the characteristics of each of the line removal grids are maintained as a look-up table. 53. The method of claim 40, wherein said adjusting step is performed automatically. 54. The method of claim 40, wherein said adjusting step is performed manually. 55. A feedback device for positioning accuracy of the X-ray source and the scattered X-ray removal grid in the X-ray imaging by the X-ray imaging means having the X-ray source and the scattered X-ray removal grid, Based on the X-ray image taken by the imaging means,
A feedback device comprising: an evaluation unit that evaluates the alignment accuracy between the X-ray source and the scattered X-ray removal grid; and a display unit that displays the alignment accuracy based on the evaluation by the evaluation unit. 56. A judging means for judging whether or not re-imaging is necessary based on the evaluation of said evaluating means, and a notification for notifying that re-imaging is necessary if said judging means determines 55. The feedback device according to claim 55, further comprising: means, wherein the evaluation means starts evaluation immediately after imaging by the X-ray imaging means. 57. An X-ray imaging apparatus using an X-ray imaging apparatus having an X-ray source and a scattered X-ray removal grid, comprising: an imaging unit configured to capture an X-ray image; X-ray source and scattered X
An X-ray imaging apparatus comprising: an evaluation unit that evaluates a positioning accuracy with a line removal grid; and a determination unit that determines whether re-imaging is necessary based on the evaluation by the evaluation unit. 58. A display means for displaying the positioning accuracy based on the evaluation by the evaluation means, and a notifying means for notifying when re-imaging is necessary by the judging means, When the determination unit determines that re-imaging is not necessary, the imaging unit further includes a unit that returns the X-ray source and the scattered X-ray removal grid to an initial position. The X-ray imaging apparatus according to claim 57, wherein the evaluation is started. 59. The apparatus according to claim 55, wherein said evaluating means evaluates at least one of a direction of the alignment error and a degree of the alignment error. 60. The apparatus according to claim 55, wherein said display means displays at least one of a direction of the alignment error and a degree of the alignment error. . 61. The evaluation means further determines a recommended characteristic of the scattered X-ray removal grid based on the evaluated positioning accuracy, and the display means further displays the recommended characteristic of the scattered X-ray removal grid. 6. The method according to claim 5, wherein
The apparatus according to any of claims 5, 56 and 58. 62. The characteristic of the scattered X-ray removal grid is as follows:
62. The apparatus according to claim 61, wherein the determination is made according to a type of examination for performing X-ray imaging. 63. The apparatus according to claim 55, wherein said display means displays at least one of a graphic image and a text image. 64. The display device according to claim 5, wherein the display unit further displays an X-ray image obtained by the imaging unit.
Apparatus according to 5, 56 and 58. 65. The apparatus according to claim 56, wherein the notifying unit performs the notification by at least one of a visual notification and an audible notification. 66. The apparatus according to claim 56, wherein said judging means compares the evaluation value of the positioning accuracy with a predetermined level, and judges that re-imaging is necessary when the evaluation value is lower than the predetermined level. An apparatus according to any of the preceding claims. 67. The apparatus according to claim 66, wherein the predetermined level is determined based on characteristics of the scattered X-ray removal grid. 68. The characteristic of the scattered X-ray removal grid is as follows:
Grid density, grid ratio, focal length, septum material,
68. The apparatus according to claim 61, 62 or 67, comprising at least one of the following materials: 69. The apparatus according to claim 6, further comprising a look-up table holding a plurality of predetermined levels for each of the different characteristics of the scattered X-ray removal grid.
67. The apparatus according to 6 or 67. 70. An adjusting means for automatically adjusting the alignment between the X-ray source and the scattered X-ray removal grid based on the evaluation when the determining means determines that re-imaging is necessary. 58. The device of claim 57, comprising: 71. A storage medium holding a program code for realizing the method according to any one of claims 38 to 54.