CN1265764C - X-ray checker - Google Patents

Abstract

To provide an X-ray inspection apparatus that eliminates a scattered X-ray component included in an X-ray image so as to obtain the X-ray image with high quality. SOLUTION: An X-ray grid 3 is placed between an X-ray tube 1 being an X-ray source and a subject 6. The scattered ray component included in the X-ray tube is calculated and eliminated on the basis of the amplitude of the interference fringes included in the X-ray image. The X-ray inspection apparatus can obtain an X-ray image, an X-ray fluoroscopy and X-ray CT image or the like with high quality in spite of less exposed dose.

Description

X ray checking device

Technical field

The present invention relates to use X ray, the radiation inspecting apparatus of gamma-rays isoradial particularly, relates to nondestructive inspection usefulness, therapeutic medical X ray checking device.

Background technology

In the past, reported the method and apparatus of removing various scattered x-ray compositions.For example, reported on above-mentioned X-ray detector face the X ray grid of the grid frequency that forms identical or integer/one of the detection pel spacing that has with X-ray detector, removed method (prior art 1: " spy opens bulletin flat 9-75332 number ") for the incident scattered x-ray composition of detector face tilt.

In addition, also report the basis point spread function of the scattered x-ray of instrumentation in advance, used overlapping filter to remove the method (prior art 2: " M.Honda, et al., Med.Phys., 20 (1), 59-69 (1993) ") of scattered x-ray composition.

In addition, the X ray grid that are configured in the body front that is taken by scanning have also been reported, direct instrumentation scattered x-ray composition, the device (prior art 3: " K.Doi, et al., Radiology, 161,513-518 (1986) ") of removal scattered x-ray composition.

In addition, also reported implementing wavelet transformation obtaining under the situation of downscaled images, obtained not have the method (prior art 4: " spy opens flat 10-031737 communique ") of downscaled images of the high image quality of Moire fringe for original digital image data with periodical configuration.

And then, reported that also the line matter of modified chi ray or line amount are for the method (prior art 5: " spy opens the 2000-245731 communique ") of radiation dependence of angle at the X-ray tube and the configuration X ray grid between the body that are taken.

Summary of the invention

The scattered x-ray composition accounts for more than 50% of signal component of detected X ray transmission picture according to operating position, makes the nondestructive inspection testing fixture, and the contrast of therapeutic medical X ray checking device reduces.

In prior art 1, constitute the X ray transmission material of X ray grid owing to not only block scattered x-ray and also block direct X ray composition, therefore exist the problem that reduces with the detected semaphore of X-ray detector.In order to increase the detection signal amount, need be added to the X ray amount that is mapped on the body that is taken, its result has the problem of the X ray light exposure increase of the body that is taken.In addition, have and to remove the scattered x-ray little, and be difficult in the such problem of receptor front formation X ray grid to the angle of incidence of detector.

In prior art 2,,, carry out the scattered x-ray correction for the body point spread function of instrumentation scattered x-ray composition in advance that is taken uniformly with certain tube voltage.In addition, above-mentioned scattered x-ray correction is carried out under supposing uniformly according to the composition of the body that is taken.But, in the shooting of reality, the composition of the body that is taken and thickness generation many variations, many variations also takes place in tube voltage in addition.Thereby, have and can not remove heat radiation X ray composition, the problem that the low precision of correction is so fully.

In prior art 3,, therefore have shooting or the such problem of radioscopy that to carry out the short time because limit, scan edge X ray slit is taken.

In prior art 4,, do not relate to and remove the scattered x-ray composition that is included in the original image though obtain the downscaled images of the observation usefulness of high image quality.

In prior art 5,, do not relate to yet and remove the scattered x-ray composition though, can access high-grade radioscopic image of even image quality owing to alleviate from the radiation dependence of angle of the X ray of rotating anode X-ray tube radiation.

The object of the present invention is to provide and to access from removed the X-ray examination method and the X ray checking device of the radioscopic image of scattered x-ray composition with the image of the X ray transmission picture of the detected inspection object of two-dimensional x-ray detector.

Another object of the present invention is to provide the X-ray examination method and the X ray checking device that can access high-quality radioscopic image when reducing the X ray light exposure of checking object.

In order to achieve the above object, in the present invention, configuration X ray grid detect the X ray transmission picture of checking object with two-dimensional x-ray detector between x-ray source and inspection object.To checking that the incident X ray of object is the slot-shaped X ray that has passed through the X ray grid.X ray that see through to check object comprises slot-shaped radio-frequency component (directly X ray composition) and by the non-slot-shaped low-frequency component (scattered x-ray composition) of checking the object scattering.If detect the X ray transmission picture of checking object with two-dimensional x-ray detector, then directly the X ray composition produces interference fringe between two-dimensional x-ray detector and X ray grid, and the scattered x-ray composition does not produce interference fringe.

Now, suppose with the roughly orthogonal direction of the detection faces center position of focus that is connected x-ray source and two-dimensional x-ray detector, make the change in location slight distance of X ray grid, then the phase place of interference fringe changes.At this moment, the amplitude of interference fringe reflects that direct X ray becomes component.That is, be accompanied by the variation of X ray grid position, the signal component of variation is direct X ray composition, and indeclinable signal component is equivalent to the scattered x-ray composition.

According to the above, can ask the distributed image (below, be called the scattered x-ray distributed image) of the scattered x-ray composition the image that is included in the X ray transmission picture of checking object from the amplitude of interference fringe.In addition, can ask direct X ray distributed image from X ray transmission image subtraction scattered x-ray distributed image.Followingly ask the operation of direct X ray distributed image to call the scattered x-ray correction above-mentioned.

In order to ask the amplitude of interference fringe, need become the image (below, be called interference fringe image) of interference fringe composition and the image of composition (below, be called non-interference fringe image) in addition to the instrumentation separation of images.In order to obtain interference fringe image, can detect and form 2 X ray transmission pictures with the interference fringe that roughly differs 180 degree phase places, generate the difference image of 2 X ray transmission pictures.On the other hand, in order to obtain non-interference fringe image, can generate the addition image that above-mentioned phase place almost differs 2 X ray transmission pictures of 180 degree.Wherein, between two X ray transmission pictures, in order to form the interference fringe that phase place almost differs 180 degree, the slight distance that need correctly control the position of X ray grid changes.

On the other hand, phase place 2 X ray transmission pictures almost differing 180 degree also can generate in order to following method.In the following description, the grid density of X ray grid is taken as the value that direct X ray composition is difficult to occur in the interference fringe (inconspicuous) that produces between two-dimensional x-ray detector and the X ray grid.In addition, the slit orientation in the X ray grid is called the slit orientation.

From X ray transmission picture,, generate the image (below, be called abstract image) that goes out pixel every 1 pixel decimation along the slit orientation.By extraction, in abstract image, interfere striped every 1 pixel.Generate 2 abstract images.Wherein, to be the extraction position that makes pixel stagger 1 pixel mutually and generate along the slit orientation for 2 abstract images.At this moment, the interference fringe that forms in 2 abstract images has the phase place that roughly differs 180 degree.Thereby, obtain the difference of these 2 abstract images, can generate interference fringe image.In addition, according to interference fringe image, can carry out the scattered x-ray correction.

In the correction of scattered x-ray composition, ask direct X ray to become component according to the amplitude of interference fringe.The amplitude of interference fringe becomes component proportional with direct X ray, its ratio (below, be called amplitude ratio) obtain according to instrumentation in advance.Amplitude ratio is to use under state that place not check object resulting spatial image to obtain.Spatial image is one or more tube voltages, and one or more spatial images that go out of the combine detection of the different X ray grid of one or more scattered x-ray clearances according to X-ray tube.Use method same as described above to generate interference fringe image for each spatial image.At this moment, become component to obtain amplitude ratio as direct X ray for the ratio of interference fringe image amplitude.Wherein, directly X ray becomes component to obtain as the semaphore of spatial image self.

Amplitude ratio is according to the change in location of spatial image.Thereby,, be kept in the memorizer in advance the distribution of the distribution of amplitude ratio as calibration image generation amplitude ratio.In order to generate the calibration image, at first, generate interference fringe image for spatial image.Then, generate the distribution of amplitudes image of interference fringe image according to the above-mentioned interference stripe pattern.At last, the pixel value with the distribution of amplitudes image is removed the image that each pixel value generated of spatial image as the calibration image.

Use the calibration image, the order that looks like to carry out the scattered x-ray correction for X ray transmission arbitrarily is as follows.At first, generate interference fringe image for X ray transmission picture (original image).Then, generate the distribution of amplitudes image of interference fringe according to the above-mentioned interference stripe pattern.And then, read the calibration image from memorizer, deduct the long-pending scattered x-ray distributed image of asking of above-mentioned calibration image and above-mentioned distribution of amplitudes image from above-mentioned X ray transmission picture (original image).At last, deduct above-mentioned scattered x-ray distributed image from above-mentioned X ray transmission picture (original image) and generate direct X ray distributed image.

Reading calibration from memorizer during image, from memorizer read corresponding to detect the X ray transmission as the time tube voltage and the calibration image of the combination of X ray grid.

When continuous detecting is checked the almost same position of object, separate particular time interval, use same scattered x-ray distributed image, can remove the scattered x-ray composition from the image of a plurality of X ray transmission pictures.

X ray grid as using in the above explanation can use parallel gate, perhaps are with the focus grid.In addition, can use the intersection grid of two parallel gate or the configuration of band focus grid juxtaposition.

As described above, in the present invention, can carry out high-precision scattered x-ray correction by the simple calculations processing.

Description of drawings

Fig. 1 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 1st embodiment.

Fig. 2 is the figure that is used to illustrate the principle of removing scattered x-ray.

Fig. 3 is the figure that is used to illustrate the position relation of X ray grid and plane X-ray detector.

Fig. 4 is the detection that is used for illustrating at the X ray transmission picture that is undertaken by the plane X-ray detector, detects the figure of locations of pixels.

Fig. 5 is the figure of relation that is used to illustrate the Nyquist frequency of the spatial frequency distribution of direct X ray composition and scattered x-ray composition and plane X-ray detector.

Fig. 6 is the figure that is used to illustrate for the interval sampling of detected X ray transmission picture.

Fig. 7 is the Nyquist frequency and the direct figure of the relation of the spatial distribution frequency of X ray composition and scattered x-ray composition when being used to interval sampling is described.

Fig. 8 is the figure that is used to illustrate other establishing method of projection gate density.

Fig. 9 is used to illustrate the figure of method that derives the spatial distribution of interference fringe amplitude according to interference fringe image.

Figure 10 is other the figure of sampling approach that is used for illustrating interval sampling.

Figure 11 is the block diagram that is used to illustrate the order of asking the calibration image.

Figure 12 is used to illustrate the block diagram of asking the order of scattered x-ray distributed image according to the calibration image.

Figure 13 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 2nd embodiment.

Figure 14 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 3rd embodiment.

Figure 15 is the figure of relation that is used for illustrating the Nyquist frequency of the present invention's the 3rd embodiment projection gate density and plane X-ray detector.

Figure 16 is the figure that is used for illustrating in the small variations of the X ray grid of the present invention the 3rd embodiment.

Being used to of Figure 17 illustrates the figure of structure of the X ray checking device of the present invention the 3rd embodiment.

Figure 18 is the figure that is used to illustrate the position relation of the X ray grid of X ray checking device of 4 embodiment of the present invention and X-ray detector.

The specific embodiment

Embodiment 1

Fig. 1 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 1st embodiment.In addition, among Fig. 1, be the y axle with the left and right directions in the paper, the above-below direction in the paper is the z axle, is the x axle perpendicular to the direction of paper.

The X ray checking device of embodiment 1 is by X-ray tube 1, collimator 2, X ray grid 3, plane X-ray detector 4, pillar 5, detected body (inspection object) 6, bed board 7, bed 8, monitor 9, control station 10, clinic control platform 11, image storage 100, image processing apparatus 101, the calibration image is preserved memorizer 102, and the scattered x-ray image is preserved memorizer 103 formations such as grade.In addition, above-mentioned each device and mechanism use well-known device and mechanism.Below, by X-ray tube 1, collimator 2, the system that X ray grid 3 and plane X-ray detector 4 constitute is called camera system.

Camera system is fixed on the pillar 5.Pillar 5 can make bed board 7 tilt by not shown leaning device.Wherein, incline direction is and the parallel plane direction of yz.By pillar 5 is tilted, can freely change direction of illumination for the X ray of detected body 6.In addition, along x, y and z direction move bed board 7 and the position of detected body 6 of configuration on bed board 7 by well-known travel mechanism.And then X ray grid 3 are for the x of pillar 5, and the position of y and z direction can be regulated by not shown apparatus for adjusting position.

Among Fig. 1, the distance of the X ray origination point of X-ray tube 1 and the input face of plane X-ray detector 4 is 100cm.In addition, the X ray input face of plane X-ray detector 4 is that every limit is the square of 204.8mm.Pixel count 1024 * 1024 pixel cells of plane X-ray detector 4, the size on a limit of each pixel are 200 μ m.In addition, the representational frame per second of plane X-ray detector 4 is 30[frame/seconds during the X ray transmission], also can be taken as 7.5 or 15[frame/second].In addition, in plane X-ray detector 4, use known direct type X-ray detector or indirect-type X-ray detector.Representational example as direct type detector or indirect-type detector, can enumerate " M.Choquette; et al.; SPIE Vol.3977,128～136 (2000) " (below, be called document 1) and " Tom J.C.Bruiins; et al.; SPIE Vol.3977,117-127 (2000) " (below, be called document 2) etc. respectively.

The distance of the X ray origination point of X-ray tube 1 and the input face of X ray grid 3 is 40cm.X ray grid 3 are known grid, are formed with a plurality of slits that X ray absorbent material and X ray transmission material dispose mutually.The slit direction of X ray grid 3 only is formed on a direction, and it is parallel with the y axle that configuration pillar 5 makes that above-mentioned slit direction becomes.These X ray grid 3 use plumbous aspect the X ray absorbing material, use paper aspect the X ray transmission material, and are not limited to these materials, for example also can use tungsten and aluminum etc.Grid are 12: 1 than (grid ratio), and grid density is 70[bar/cm], the thickness of lead foil is 50[μ m].In addition, X ray grid 3 have focus, and its focal length is 40[cm].

Secondly, the action of the X ray checking device of present embodiment 1 is described.This X ray checking device is obtained the radioscopy image and the X ray photographic images of detected body 6, shows on monitor 9 after having removed the scattered x-ray composition that is included in these images.The irradiation of the X ray during from radioscopy and X ray shooting, the order till the demonstration of scattered x-ray correction image is as follows.

At first, examiner (operator) operator's console 10 or 11 indication beginning radioscopy or the shootings of clinic control platform are from X-ray tube 1 radiation X ray.Then, detect the X ray that has seen through detected body 6, directly be recorded in the pixel memories 100 with plane X-ray detector 4.And then image processing apparatus 101 only extracts the scattered x-ray composition in the X ray transmission picture that is recorded in the image storage 100, is kept at the scattered x-ray image and preserves in the memorizer 103.At last, the X ray transmission image subtraction of subtractor 104 from be kept at image storage 100 is kept at the scattered x-ray component-part diagram picture in the scattered x-ray image preservation memorizer 103, generates the scattered x-ray correction image, shows on monitor 9.In addition, when radioscopy, up to indicate the end perspective by the examiner till, carry out above-mentioned a series of operation repeatedly.

At this moment, scattered x-ray component-part diagram picture both can generate when the radioscopy picture is input to image storage 100 at every turn, also can generate at every a plurality of frames (common 2～30 frames).Every a plurality of frames generate the scattered x-ray component-part diagrams as the time, to generate till the next scattered x-ray component-part diagram picture during, use same scattered x-ray component-part diagram picture to carry out the scattered x-ray correction approx.Below, such approximate correcting method calls correction at interval during radioscopy.When the mobile phase of the body 6 that is taken is big for the frame per second of plane X-ray detector 4, can carry out interval correction.Revise by adopting at interval, owing to can not reduce the processing speed that image processing apparatus 101 requires, therefore can the simplification device structure.

Aspect the extraction of above-mentioned scattered x-ray composition, use the calibration image that is kept in the calibration image preservation memorizer 102.Narrate in the back about scattered x-ray composition extract operation of being undertaken by image processing apparatus 101 and the details of calibrating image.

Fig. 2 is the figure that is used to illustrate the principle of removing scattered x-ray.Wherein, Fig. 2 (A) expression sees through the direct X ray of detected body 6 and the relation of plane X-ray detector 4, and Fig. 2 (B) is illustrated in the scattered x-ray of scattering-in of detected body 6 and the relation of plane X-ray detector 4 in addition.

At first, in Fig. 2 (A), the same X ray 200 that takes place from X ray origination point 20 blocks a part by the X ray absorbing material 21 of X ray grid 3 inside.Thereby transmitted X-rays grid 3 later X ray become slot-shaped X ray 201.Below, so slot-shaped X ray 201 is called modulation of X-ray.Modulation of X-ray 201 is roughly foursquare X-ray beams, himself has the signal component of high frequency.Therefore the X ray (directly X ray) that has seen through the inside of detected body 6 and the pixel 22 of plane X-ray detector 4 between cause interference, interfere striped (Moire fringe).On the other hand, in Fig. 2 (B), owing to scattering loses the signal component of high frequency, therefore and between the pixel 22 do not interfere striped at X ray (scattered x-ray) 202 of the scattering-in of detected body 6.

According to the above as can be known, interference fringe only reflects direct X ray, and the amplitude of interference fringe becomes component proportional with direct X ray.Thereby, by asking the amplitude of interference fringe, can be separated into direct X ray composition and scattered x-ray composition to detection signal, carry out the scattered x-ray correction.Wherein, in order to carry out the scattered x-ray correction, need to solve following 2 problems.That is, ask the amplitude of interference fringe to become the ratio (problem 1) of branch with direct X ray, and the amplitude (problem 2) of asking interference fringe.

About problem 1, can use detected X ray transmission picture under the state of not placing detected body 6 (below, as spatial image), ask the amplitude of interference fringe to become the ratio (below, as calibration than) of branch with direct X ray.That is,,, then can easily ask the calibration ratio if therefore can ask the amplitude of interference fringe because the signal that is included in the spatial image only is direct X ray composition.

About problem 2, for example, can ask the amplitude of interference fringe by the position of X ray grid 3 being observed the phase place variation of interference fringe along the horizontal direction minute movement time.But said method has at a high speed and carries out accurately mobile so technical difficulty of X ray grid 3.Therefore, in present embodiment 1, adopt the method for the amplitude of the interval sampling instrumentation interference fringe of passing through pixel.Details about interval sampling is narrated in the back.

Fig. 3 is the figure that is used to illustrate the position relation of X ray grid 3 and plane X-ray detector 4.The distance table of the plane of incidence from X ray origination point 20 to X ray grid 3 is shown d, the distance table of the input face from X ray origination point 20 to plane X-ray detector 4 is shown D.The value of d in the present embodiment 1 is 40[cm], the value of D is 100[cm].The slit direction of X ray grid 3 is configured to parallel with the y direction of principal axis.

In addition, X-ray detector 4 is arranged such that being arranged as of pixel is parallel with x and y direction.The position of the x of above-mentioned arrangement and y direction is expressed as i respectively, the j direction, its position is shown as (i, j) (i, j=0,1 ..., 1023).In addition, for simply, use propylene model 30 in the following description as detected body 6.Wherein, propylene model 30 is made of acrylic panel and lead rod 31.Lead rod 31 is configured in the center of acrylic panel, makes its long side direction parallel with the y direction.

Fig. 4 illustrates to detect the figure of locations of pixels in the detection of the X ray transmission picture that is undertaken by plane X-ray detector 4.Shown in Fig. 4 (A), the i of X-ray detector 4, the pixel separation of j direction is represented with Δ d.Wherein, in present embodiment 1, Δ d is 200[μ m].When radioscopy and X ray shooting, at all location of pixels (i, j) the middle X ray that detects.Fig. 4 (B) illustrates an example of the section of detected image.Wherein, Fig. 4 (B) illustrates the section of this direction of propylene model 30.At this moment, if suitably set the specification and the spatial configuration of X ray grid 3, then shown in Fig. 4 (B), can suppress the interference fringe that in the section of i direction, takes place for very little according to method described later.Signal shown in Fig. 4 (B) is the signal that detects the scattered x-ray composition shown in the direct X ray composition shown in Fig. 4 (C) and Fig. 4 (D) simultaneously.The scattered x-ray correcting process is suitable with the processing that extracts the direct X ray composition shown in Fig. 4 (C) from the detection signal shown in Fig. 4 (B).

Fig. 5 is the figure of relation that is used to illustrate the Nyquist frequency of the spatial frequency distribution of direct X ray composition and scattered x-ray composition and plane X-ray detector 4.Directly in the frequency content 500 of X ray, comprise the frequency characteristic of modulation of X-ray 201, see through the information of the frequency response of the frequency characteristic of direct X ray of detected body 6 and plane X-ray detector 4.Usually the frequency response of plane X-ray detector 4 raises with frequency and descends.The frequency characteristic of modulation of X-ray 201 is represented the tectonic information of X ray grid 3, comprises the information in a plurality of cycles about grid.

If grid density is designated as fg[bar/cm], formulate below then the grid density fd of projection uses on the face of plane X-ray detector 4.

[formula 1]

$\mathrm{fd}=\frac{d}{D}\mathrm{fg}$

(formula 1)

According to (formula 1), the value of fd can be by changing fg, d, the value of D and setting arbitrarily.Among Fig. 5, the low slightly example of Nyquist frequency fq that the value of fD is set at ratio sensor is shown.Frequency intensity 502 among the frequency f d reduces along with approaching Nyquist frequency fq.This means fuzzy according to plane X-ray detector 4, the periodic tectonic information of X ray grid 4 (below, be designated as the grizzly bar stricture of vagina) no longer noticeable.Here, the difference of Nyquist frequency fq and projection gate density f d as beat frequency fb, with following formula definition.

[formula 2]

Fb=|fq-fd| ... (formula 2)

That is,, therefore can reduce fd as far as possible owing to be included in grizzly bar stricture of vagina in the X ray transmission picture not eye-catching.On the other hand, the information that in the frequency content 501 of scattered x-ray, only comprises low-frequency component.

Fig. 6 is the figure that is used to illustrate for the interval sampling of detected X ray transmission picture.In addition, Fig. 7 is the Nyquist frequency and the direct figure of the relation of the spatial frequency distribution of X ray composition and scattered x-ray composition when being used to interval sampling is described.As Fig. 4 (A) illustrates, use all pixel detection X ray transmission pictures of plane X-ray detector 4.That is, if (i, the semaphore of j) checking out are designated as f, and (i, j), then X ray transmission picture can be expressed as f (i, j) (i, j=0～N) at location of pixels.Wherein, N is as the i of plane X-ray detector 4, the pixel count of j direction.In present embodiment 1, N=1024.Interval sampling is as Fig. 6 (A) and (C), is that (i goes out pixel value along the i direction every a pixel decimation in j), generates the method for image from f.At this moment, according to the extraction position of pixel, can generate following 2 kinds of abstract images.

[formula 3]

F1 (m, n)=f (2m, and n) (m=0～N/2-1, n=0～N-1) ... (formula 3)

[formula 4]

F2 (m, n)=f (2m+1, and n) (m=0～N/2-1, n=0～N-1) ... (formula 4)

F1 (m, n) and f2 (m, the Nyquist frequency f ' q of m direction n) (=1/ (4 Δ d)) become f (i, half of Nyquist frequency fq j) (=1/ (2 Δ d)).That is, be f ' q=fq/2.As shown in Figure 7, the direct X ray composition 500 during interval sampling is that centrage is folding symmetrically with f ' q, obscures (エ リ ア シ Application グ).Among Fig. 7, the 701st, direct X ray composition 500 obscure the folding composition that causes, in addition, the 701st, the folding composition that causes by obscuring of scattered x-ray composition 501.

Its result, the composition 502 of projection gate density f d becomes the beat composition 702 of frequency f b, is formed on low frequency one side, interferes striped.Thereby, abstract image f1 (m, n) and f2 (m comprises interference fringe (with reference to Fig. 6 (B) and (D)) in the section of m direction n).

As described above, in order to carry out the amplitude that the scattered x-ray correction can instrumentation above-mentioned interference striped.But, abstract image f1 (m, n) and f2 (m, n) in owing to remove beyond each interferometric fringe signal, also comprise the tectonic information of detected body 6, therefore be difficult to correctly extract the amplitude of interference fringe composition.

In order correctly to extract the amplitude of interference fringe composition, by following formula generate f1 (m, n) and f2 (m, difference image s n) (m, n).

[formula 5]

S(m，n)＝f1(m，n)-f2(m，n)(m＝0～N/2-1，n＝0～N-1)

(formula 5)

Shown in (formula 3) and (formula 4), for f1 (m, n) and f2 (m, (i, j) sample position is along i direction 1 pixel that respectively staggers mutually for f n).Therefore, be included in f1 (m, n) and f2 (m, n) interference fringe in along the m direction stagger mutually 180 the degree phase places.Thereby (m n) only comprises interference fringe composition such shown in Fig. 6 (E), therefore can easily obtain the amplitude of interference fringe from s (m, n) owing to difference image s.

In the explanation of using Fig. 4～Fig. 6, projection gate density f d is set at value than the little beat frequency fb of Nyquist frequency fq degree (below, be called the non-setting of obscuring).At this moment, be formed on the X ray transmission as f (i, j) the frequency f d=(fq-fb) of the grizzly bar stricture of vagina in, be formed on abstract image f1 (m, n) and f2 (m, n) frequency of the interference fringe in is fb.As mentioned above, not eye-catching in order to make the grizzly bar stricture of vagina, need reduce fb as far as possible.But at this moment the frequency f b of interference fringe reduces simultaneously, and its position resolution reduces.Like this, fb can not be excessive, can not be too small.Usually, fb preferably is set at 2～5[bar/cm] about.

Fig. 8 is the figure that is used to illustrate other establishing method of projection gate density.Obscure in the setting non-, projection gate density f d is set at the value of hanging down beat frequency fb degree than Nyquist frequency fq.Different therewith, below, illustrate projection gate density f d is set at value than the high beat frequency fb of Nyquist frequency fq degree (below, be called and obscure setting).When obscuring setting, in all pixels sampling, also obscure.At this moment, the frequency content 502 of projection gate density f d can be observed (with reference to Fig. 8 (A)) after obscuring the composition 702 that becomes frequency (fq-fd).

The value right and wrong of frequency f q-fd is obscured value identical when setting, and is obscuring under the situation of setting, as the folding composition that with fq is the center, can observe the grizzly bar stricture of vagina, therefore compares with the situation of Fig. 5, and spectrum intensity reduces.Promptly obscure setting by employing, comparing with the non-situation of obscuring setting to make the grizzly bar stricture of vagina not eye-catching.

On the other hand, when interval sampling, the frequency content 502 among the projection gate density f d is observed by folding interference fringe composition as frequency f b.Wherein, the spectrum intensity of this interference fringe composition is compared with the non-situation of obscuring setting and is also reduced, and therefore also exists the problem of the mensuration precision reduction of interference fringe amplitude.As described above, the setting of projection gate density is according to preferential suppressor striped, the still preferential mensuration precision that improves the interference fringe amplitude, and selecting to obscure setting also is the non-setting of obscuring.

In addition, in the present embodiment 1, because grid density fg is taken as 70[bar/cm], X ray origination point-pitch is taken as 40[cm from d], X ray origination point-monitor distance D is taken as 100[cm], therefore according to formula 1, projection gate density f d becomes 28[bar/cm].On the other hand, because pixel separation Δ d is 200[μ m], so Nyquist frequency fq is 25[bar/cm].Thereby, obscure in advance and set projection gate density, its beat frequency is 3[bar/cm].In addition, for non-obscure set projection gate density f b, for example, in above-mentioned setting, can be taken as 31.4[cm to d].At this moment projection gate density f d becomes 22[bar/cm], beat frequency 3[bar/cm will take place equally] interference fringe.

Fig. 9 is used to illustrate the method that derives the distribution of interference fringe amplitude according to interference fringe image.(m, n) (m=0～N/2-1, n=0～N-1) is the interference fringe image 90 ((a) among Fig. 9) that only comprises the interference fringe composition to the difference image s that obtains according to (formula 5).Interference fringe distribution of amplitudes arithmetic unit 1104 is devices of asking the distribution of amplitudes image 95 of interference fringe according to interference fringe image 90, is made of following order of operation.

At first, interference fringe peak detector 91 detects peak (maximum and the minimum ((b) among Fig. 9) of interference fringe 99 for the section of the m direction of interference fringe image 90.(carry out=0～N-1) position for all n in the peak value detection of above-mentioned m direction.Then, pixel interpolating apparatus 92 handles are made the upper limit envelope 96 and the lower limit envelope 97 ((c) among Fig. 9) of interference fringe 99 along connecting with straight line between the maximum of the adjacency of m direction and between the minimum between peak value.

In addition, above-mentioned interpolate value is not only at the location of pixels m (point on=0～N/2-1), and also obtaining along the centre position of m direction pixel adjacent.Ask interpolate value by centre position, after interval sampling, can turn back to N to the pixel count of the m direction that becomes N/2 once more in pixel.(carry out by=0～N-1) position for whole n for above-mentioned interpolation.The position of n direction since with the position consistency of the j direction of complete sampled images, therefore when interpolation finishes, can turn back to picture element matrix once more (i, j) (i, j=0～N-1).The difference image 98 of upper limit envelope 96 and lower limit envelope 97 is equivalent to the amplitude of interference fringe 99.

Thereby then (i, j) (i, j=0～N-1) ask difference image 98 make the interference fringe distribution of amplitudes ((b) among Fig. 9) of each position to amplitude arithmetic unit 93 in all positions.Wherein, the above-mentioned interference striped distributes owing to comprise the radio-frequency component that produces by above-mentioned straight-line interpolation, therefore uses two-dimentional LPF (low pass filter) 94 to remove radio-frequency component, obtains final distribution of amplitudes image A (i, j) ((e) among Fig. 9).As the example of two-dimentional LPF94, can enumerate known rolling average and handle (the pixel region of acquisition rolling average: 2 * 2 pixel counts～5 * 5 pixel counts) etc.

Figure 10 is other the figure of sampling approach that is used for illustrating interval sampling.In Fig. 6, as interval sampling, illustrate, and also can expand to generally as extraction at interval every k pixel (k≤1) along the method for i direction every a pixel decimation pixel.As an example, shown in Figure 10 every the example of 2 pixel decimations.In this case, have 3 kinds of abstracting methods shown in Figure 10 (A)～(C), sample position whenever moves a pixel along the i direction, change in displacement 120 degree of the interference fringe that takes place according to interval sampling.

That is, Figure 10 (A) and (B) between and Figure 10 (B) and (C) between the phase shift of interference fringe become 120 degree.In addition, Figure 10 (A) and (C) between the phase shift of interference fringe be 240 degree.Under each situation,, then can both remove the tectonic information of the body that is taken in the signal and only extract interference fringe if generate the difference image of 2 pixels.

In addition, the phase shift of the interference fringe that extracts according to the phase shift amount between the image that obtains difference changes, but its distribution of amplitudes does not change.That is, even generate difference image, in that (i does not produce very big difference in j) according to the 1104 final distribution of amplitudes image A that obtain of the interference fringe distribution of amplitudes arithmetic unit among Figure 11 described later for the arbitrary combination of above-mentioned Figure 10 (A)～(C).Wherein, in order to remove the tectonic information of the body that is taken accurately according to difference, preferably as far as possible near the pixel decimation position between the difference image.That is, preferably use 2 abstract images of pixel decimation position adjacency to carry out difference.Generally, if carry out interval sampling every k pixel, the following formulate of phase shift amount q between 2 of pixel decimation position adjacency abstract images then.

[formula 6]

Q=360/ (K+1) (degree) ... (formula 6)

Sometimes the quantum noise that comprises X ray in difference image worsens the mensuration precision of interference fringe amplitude.Therefore, before carrying out interval sampling, can (i, j) (i, j=0～N-1) carry out rolling average to be handled and alleviates quantum noise for original image f.Along i, the pixel count that the j direction obtains rolling average is designated as 2I+1 respectively, 2J+1 (I, J=0,1,2 ...), then (i j) calculates with following formula the image fm after the rolling average.

[formula 7]

$\mathrm{fm}(i,j)=\frac{1}{(2I+1)(2J+1)}\underset{k=i-I}{\overset{i+I}{\mathrm{\Σ}}}\underset{l=j-J}{\overset{j+J}{\mathrm{\Σ}}}f(k,l)$

(formula 7)

But if carry out the rolling average of i direction then radio-frequency component reduces, the interference fringe length in the partition image reduces.Therefore, generally do not carry out the rolling average of i direction.On the other hand, carrying out rolling average in the scope about i=5～10 usually along the j direction.

The situation of the slit direction of the X ray grid 3 that above-mentioned rolling average processing, interval sampling processing, the derivation of distribution of amplitudes image are handled perpendicular to the j direction has been described.Different therewith, under the situation of the slit direction of i direction configuration X ray grid 3, also can in above-mentioned whole processing, exchange i direction and j direction.In addition, using under the situation of grid, also can carry out above-mentioned whole processing for i direction and these 2 directions of j direction with latticed slit as X ray grid 3.

More than, use interval sampling shows the distribution of amplitudes image of interference fringe, below, the method for using the distribution of amplitudes image to carry out the scattered x-ray correction is described.

If be included in certain pixel value f in the X ray transmission picture (i, j) (the direct X ray of i=0～N-1) become component be designated as fd (i, j), then fd (i, j) with the amplitude A of the interference fringe of same position (i, j) proportional.Thereby the amplitude by asking interference fringe in advance becomes the ratio (calibration than) of component with direct X ray, can ask direct X ray distributed image fd (i, j).

Calibration is than obtaining by the usage space image.Generally, calibration is than owing to according to the detection position on the plane X-ray detector 4 and what are different, therefore ask its distribution as the calibration image.If (then (i j) obtains with following formula r for i, j) expression calibration image with r.

[formula 8]

R (i, j)=fair (i, j)/Aair (i, j) ... (formula 8)

In the formula, (i is a spatial image of not placing instrumentation under the state of detected body 6 j) to fair, and (i is for fair (i, the distribution of amplitudes image of j) obtaining j) to Aair.

At this moment, (i, j), the formula below energy is enough roughly calculates its direct X ray and becomes component as f for X ray transmission arbitrarily.

[formula 9]

F ' d (i, j)=r (i, j) A (i, j) ... (formula 9)

Here, as the direct estimate of X ray composition, be the result of calculation of (formula 9) because (i lacks radio-frequency component in j) at f ' d.In addition, the lacking of above-mentioned radio-frequency component, result from the distribution of amplitudes image A ((i, j) lacking of the radio-frequency component in resulted from the interpolation of being undertaken by pixel interpolating apparatus between peak value 92 and handled A i, j) lacking of the radio-frequency component in.For from direct X ray composition estimate f ' d (i, j) obtain correct direct X ray distributed image fd (i, j), can at first ask scattered x-ray distributed image fs (i, j), then from original image f (i, j) (i, j), the scattered x-ray distributed image is obtained with following formula to deduct fs.

[formula 10]

Fs (i, j)=f (i, j)-f ' d (i, j) } ^*G (i, j) ... (formula 10)

In the formula, (i j) is two-dimentional LPF (low pass filter), computing to g ^*It is the expression two-dimensional convolution.In (formula 10), the result of calculation in the right { } comprises the radio-frequency component of scattered x-ray composition and direct X ray.Therefore, use LPF to remove radio-frequency component (directly X ray composition) and only extract the scattered x-ray composition.As LPF, use common digital filter or rolling average processing etc.If (i, j), (i j) can obtain by enough following formula then direct X ray distributed image fd to ask scattered x-ray distributed image fs.

[formula 11]

Fd (i, j)=f (i, j)-fs (i, j) ... (formula 11).

More than, the method for using the calibration image to carry out the scattered x-ray correction has been described.In addition, under the smaller situation of the variation of the calibration ratio of calibration in the image, also can be approximated to be r (i, j)=ro.In this case, in ro, for example use r (i, meansigma methods j) etc.In addition, r (i, j) or the value of ro how much change along with the tube voltage of X-ray tube 1.Thereby, can for the tube voltage of predetermined number kind measure in advance r (i, j) or ro, according to taking or tube voltage during perspective is selected them.

Figure 11 is the block diagram that is used to illustrate the order of asking the calibration image.The generation of calibration image is at first carried out from the shooting of spatial image.By the shooting of spatial image, in image storage 100, guarantee spatial image fair (i, j).Then, use rolling average arithmetic unit 1100 to carry out i, the rolling average of j direction.In addition, in the calculating of rolling average, use (formula 7).

Then, use partition image generating apparatus 1101 and 1102, generate respectively abstract image f1 (m, n) and f2 (m, n).In addition, in the generation of abstract image, use (formula 3) and (formula 4).Then, by subtractor 1103 obtain abstract image f1 (m, n) and f2 (m, difference n), generate difference image s (m, n).Then, with interference fringe distribution of amplitudes arithmetic unit 1104, generate distribution of amplitudes image A air for spatial image (i, j).In addition,, used Fig. 9 that details has been described, therefore omitted explanation here about the computing of being undertaken by interference fringe distribution of amplitudes arithmetic unit 1104.

Then, by divider 1105 calculate distribution of amplitudes image A air (i, j) with fair (i, ratio j), generate calibration image r (i, j).At last, (i, j) information with the tube voltage of importing from control station 10 is kept at the calibration image preservation memorizer 102 calibration image r.

Figure 12 is the order of scattered x-ray distributed image is asked in explanation according to the calibration image a block diagram.At first, (i j) guarantees in image storage 100 as f for X ray transmission picture or shooting.The process from rolling average arithmetic unit 1100 to interference fringe distribution of amplitudes arithmetic unit 1104 of then carrying out, since identical with the generating apparatus of above-mentioned calibration image shown in Figure 11, explanation therefore omitted.By said process generate the distribution of amplitudes image A (i, i).

Then, accumulator 1200 the distribution of amplitudes image A (i, j) with the calibration image preserve the calibration image r that preserves in the memorizer 102 (i j) adds up, generate direct X ray composition drawing for estimate as fd (i, j).In addition, this adds up and is equivalent to the computing of above-mentioned (formula 9).In addition in above-mentioned adding up, select to use with generate original image f (i, the calibration image r that the immediate tube voltage of the tube voltage in the time of j) generates (i, j).Then, subtractor 1201 from original image f (i, j) deduct direct X ray composition drawing for estimate as f ' d (i, j), then, LPF 1202 is by the radio-frequency component of above-mentioned subtraction image, generate the scattered x-ray component-part diagram as fs (i, j).In addition, a series of operation of being undertaken by above-mentioned subtractor 1201 and LPF 1202 is equivalent to (formula 10).At last, the scattered x-ray component-part diagram is kept in the scattered x-ray image preservation memorizer 103 as fs (i, j).

As shown above, in present embodiment 1,, carry out the scattered x-ray correction according to the distribution of amplitudes of 2 abstract image instrumentation interference fringes that generate by interval sampling.Owing to can correctly obtain interference fringe from 1 X ray transmission picture, therefore can carry out high speed and high-precision scattered x-ray correction.

Embodiment 2

Figure 13 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 2nd embodiment.

Below, if the difference of explanation and the X ray checking device of embodiment 1 only is then in embodiment 1, in X ray checking device, configuration X-ray tube 1 on detected body 6, collimator 2 and X ray grid 3 (below, as last tubular construction), and different therewith, in the X ray checking device of present embodiment 2, X-ray tube 1, collimator 2 and X ray grid 3 all are configured in following (below, as down tubular construction) of bed board 7.

Under the situation of last tubular construction, because the distance between X ray grid 3 and the detected body 6 is narrow, therefore exist detected body 6 misconnections and touch the high such problem of probability of X ray grid 3, and by making down tubular construction, the danger that can avoid 3 misconnections of X ray grid to touch detected body 6.

Embodiment 3

Figure 14 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 3rd embodiment.In present embodiment 3, do not use interval sampling and the distribution of instrumentation interference fringe.Below, the difference of explanation and the X ray checking device of embodiment 1 only.

The X ray checking device of embodiment 3 has grid positioner 1400.Grid positioner 1400 can use not shown shift in position mechanism to change the position of X ray grid 3 at high speed along the x direction of principal axis.The grid ratio of X ray grid 3 is 12: 1, and grid density is 117.5[bar/cm], the thickness of lead foil is 40[μ m].In addition, above-mentioned shift in position mechanism uses realizations such as piezoelectric.

When X ray is taken, separate interval Δ t, radiate the X ray of 2 subpulse shapes.In addition, with the radiation synchronised of above-mentioned 2 subpulse X ray, plane X-ray detector 4 detects 2 X ray and takes picture.On the other hand, when radioscopy,, continue the radiation pulsed X-ray every the ETAD expected time of arrival and departure interval of delta t.In addition, with the radiation synchronised of above-mentioned pulsed X-ray, carry out the detection of the radioscopy picture that undertaken by plane X-ray detector 4 continuously.The representation example of X ray pulse spacing Δ t when above-mentioned shooting and perspective is 33.3[ms], and also can be taken as 66.6[ms].

The radiation synchronised of the grid positioner 1400 above-mentioned pulsed X-ray when taking and during perspective, the axial position of x of change X ray grid 3.In addition, narrate in the back about amount of change at this moment.

Figure 15 is used for explanation at embodiments of the invention 3, the figure of the relation of the Nyquist frequency of projection gate density and plane X-ray detector 4.In the X ray checking device of present embodiment 3, make X ray transmission picture itself interfere striped.Therefore, be set at 2 times the value that makes projection gate density f d approach Nyquist frequency fq.The difference of supposing 2fq and fd is f ' b, then produces frequency f by obscuring in X ray transmission picture ' the interference fringe composition 702 of b.

In addition, in present embodiment 3, the grid density of X ray grid 3 is obtained 117.5[bar/cm], X ray origination point-pitch is taken as 40[cm from d], X ray origination point-detector distance D is taken as 100[cm].Thereby according to (formula 1), projection gate density f d becomes 47[bar/cm].On the other hand, because pixel separation Δ d is 200[μ m], so Nyquist frequency fq is 25[bar/cm].According to above-mentioned, the frequency f of the interference fringe that in X ray transmission picture, takes place ' b becomes 3[bar/cm].

Figure 16 is the figure that is used for illustrating in the small variations of the X ray grid of the embodiment of the invention 3.As mentioned above, in the X ray checking device of present embodiment 3, between X ray pulse spacing Δ t, make X ray grid 3 minute movement along the x direction of principal axis.And its amount of movement is by the cycle Δ h regulation of the X ray absorbent material 21 that constitutes X ray grid 3.

At first, when taking, the pulse of 2 irradiation X ray, 2 photographic images of instrumentation.At this moment the position of grid positioner 1400 control X ray grid 3 makes between 2 shootings, makes the position of X ray grid 3 move Δ h/2 along the x direction of principal axis.That is, if the position of the X ray grid when the 1st time taken is taken as Figure 16 (A), the position of the X ray grid when then taking for the 2nd time is Figure 16 (B).

On the other hand, when perspective, the X ray pulse takes place continuously.Therefore grid positioner 1400 makes the vibration of X ray grid, make each when the X ray pulse takes place, the position of X ray grid 3 become Figure 16 (A) → (B) → (A) → (B) → ...

Be accompanied by the shift in position of above-mentioned X ray grid 3, the phase place of the interference fringe that takes place in X ray transmission picture moves 180 degree along the x direction.Thereby, can access 2 X ray transmission pictures of interference fringe with phase place mutual deviation 180 degree.Use the difference image of these 2 X ray transmission pictures to extract the method that interference fringe is carried out the scattered x-ray correction, because so omission explanation identical with the method that in embodiment 1, illustrated.In addition, in order to remove the interference fringe composition in the X ray transmission picture, can generate the addition image of above-mentioned 2 X ray transmission pictures.According to this additive operation, can make the interference fringe that is included in the X ray transmission picture repeal by implication and be removed.The scattered x-ray correction is carried out for above-mentioned addition image.

Embodiment 4

Figure 17 is the figure of structure that is used to illustrate the X ray checking device of the present invention the 4th embodiment.Present embodiment 4 is to have used the scattered x-ray modification method based on interval sampling that illustrated in embodiment 1 in X ray CT.Therefore, because the scattered x-ray correcting process after the acquisition of X ray transmission picture is identical with the method shown in the embodiment 1 so omit explanation, the difference in apparatus structure and the image pickup method only is described.

The X ray checking device of present embodiment 4 is by X-ray tube 1, X ray wave filter 12, collimator 2, X ray grid 3, X-ray detector 4, detected body 6, bed board 7, swivel plate 1701, frame 1700, monitor 9, control station 10, image storage 100, image processing apparatus 101, the calibration image is preserved memorizer 102, and the scattered x-ray image is preserved memorizer 103, and image reconstructs device 1702 formations such as grade.In addition, above-mentioned each device and mechanism use well-known device and mechanism.

Below, by X-ray tube 1, X ray wave filter 12, collimator 2, the system that X ray grid 3 and X-ray detector 4 constitute is called camera system.Camera system is fixed on the swivel plate 1701, by not shown known CD-ROM drive motor rotation.In addition, below, the rotating shaft of swivel plate 1701 as the Z axle.In addition, with center of rotation O be the coordinate axes of the level of initial point and vertical direction respectively as X-axis, Y-axis.Swivel plate 1701 is totally supported by frame 1700.

In Figure 17, X ray origination point 20 is 69[cm with the distance of the center of rotation O of swivel plate 1701], X ray origination point 20 is 32[cm with the distance of the input face of X ray grid 3], X ray origination point 20 is 107[cm with the distance of the input face of X-ray detector 4], with the center of rotation O of X-ray detector 4 is that the effective field of view at center is diameter 48[cm], the diameter of opening portion 1703 is 70[cm].The once typical example of the needed time of scanning of rotation of swivel plate 1701 is 0.6 second.X-ray detector 4 is the solid-state detectors that are made of the ceramic flashing element, and the pixel count of XY in-plane is 896 pixels, and the pixel count of Z-direction is 64 pixels.The size of above-mentioned each interelement XY face direction and Z-direction is 1[mm].In addition, each arrangements of components is at distance X ray origination point S about equally on the circular arc of distance.The typical example of the film stock number that swivel plate 1701 once rotates is 900, once takes when swivel plate 1701 each rotations 0.4 are spent.

When taking, the photographic images of taking with X-ray detector 4 is by not shown known collecting ring mechanism, and order is kept in the image storage 100.The X ray transmission picture that is recorded in the image storage 100 uses the method identical with the method that illustrated in embodiment 1, carried out after the scattered x-ray correction, is input to image and reconstructs in the device 1702.Image reconstructs device 1702 and uses well-known image to reconstruct algorithm, generates the CT layer image of detected body 6, shows on monitor 9.

Figure 18 is the figure that is used to illustrate the position relation of the X ray grid 3 of X ray checking device of the embodiment of the invention 4 and X-ray detector 4.X ray grid 3 alternatively dispose X ray absorbing material and X ray transmission material on the circular arc that with X ray origination point 20 is the center, form the slit.In addition, above-mentioned slot arrangement is in the direction parallel with the Z axle.In the X ray absorbing material of this X ray grid 3, use lead, in the X ray transmission material, use paper, but be not limited to these materials, for example also can use replacements such as tungsten and aluminum.The grid ratio of X ray grid 3 is 14: 1, and grid density is 27[bar/cm], the thickness of lead foil is 100[μ m].In addition, X ray grid 3 have focus, and this focal length is 40[cm].It is i that the pixel arrangement of X-ray detector becomes the position with surfaces of revolution direction, is the rectangular of j with the position of rotating shaft (Z axle) direction.The slit of X ray grid 3 projects to the j direction, produces the axial interference fringe of i.

In present embodiment 4, because grid density fg is taken as 70[bar/cm], X ray origination point-pitch is taken as 32[cm from d], X ray origination point-detector distance D is taken as 107[cm], therefore according to (formula 1), projection gate density f d becomes 8[bar/cm].On the other hand, because pixel separation Δ d is 1[mm], so Nyquist frequency fq is 5[bar/cm].Thereby, obscure and set projection gate density, its beat frequency is 3[bar/cm].Use this interference fringe composition waveform, use the interval sampling that in embodiment 1, illustrated to carry out the scattered x-ray correction.

More than, specifically understand the present invention according to embodiment 1～4.As the penetrating in the grid ratio method of existing scattered x-ray modification method,, therefore can not remove scattered x-ray fully owing to be difficult to make physically grid than (grid than) big X ray grid.As an example, using grid density 60[bar/cm], grid were than 10: 1, the thickness 50[μ m of lead foil] the X ray grid, carried out thickness 30[cm] the X ray of tank when taking (tube voltage 120[kV]), the ratio (scattered x-ray composition than) that detected scattered x-ray composition accounts for the X ray signal approximately is 50%.

Different therewith, if use the present invention, then can be suppressed to scattered x-ray composition ratio approximately about 5%, therefore can improve the image quality of X ray transmission picture significantly.In addition, in existing X ray grid method,, therefore exist the problem of the invalid exposure that produces detected body owing between X-ray detector and detected body, dispose the X ray grid.Different therewith, in the present invention,, therefore can eliminate above-mentioned invalid exposure owing between x-ray source and detected body, dispose the X ray grid, compare with above-mentioned X ray grid method, can reduce 30～40% to the light exposure of detected body.

The present invention is not limited to the foregoing description 1～4, can carry out all changes in the scope that does not break away from its aim, and this is self-evident.

For example, used X-ray tube as x-ray source in the present embodiment, however also can be with replacements such as radiating lights.In addition, the lonizing radiation beyond X ray, visible light, ultraviolet also can be used this method in the infrared ray etc.And then the present invention removes X ray CT device, beyond the radioscopy filming apparatus, can also be useful in the X ray non-destructive testing apparatus, in the X ray baggage check device etc.

At last, illustrate as follows based on X-ray examination method of the present invention.

(1) X-ray examination method of the present invention has following process: configuration X ray grid between x-ray source that produces X ray and inspection object, shine above-mentioned X ray to above-mentioned inspection object, detect the process of the transmission picture of above-mentioned inspection object with two-dimensional x-ray detector; Sampling frequency with the interval of the pixel that separates predetermined number, on the direction of the X ray absorber grid of arranging above-mentioned X ray grid, from the image of above-mentioned transmission picture, extract pixel, obtain respectively and to form the process that only has by 2 abstract images of the interference fringe of the different phase place of predetermined angular degree; Obtain the process of the distribution of amplitudes image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 abstract images; Use above-mentioned distribution of amplitudes image to obtain the process of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the image of above-mentioned transmission picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image from the pixel value of the image of above-mentioned transmission picture, remove the process of above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture.

(2) in the X-ray examination method of (1), has following process: from the pixel value of the image of above-mentioned transmission picture, the pixel value that deducts the pixel value of the above-mentioned deduction image of reading from above-mentioned memorizer and above-mentioned distribution of amplitudes image is long-pending, obtain the process of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the image of above-mentioned transmission picture, wherein, above-mentioned memory stores the deduction image of obtaining in advance for the distribution of inferring the direct X ray composition in the image that is included in above-mentioned transmission picture; And deduct the process of the pixel value of above-mentioned scattered x-ray distributed image, and remove above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture from the pixel value of the image of above-mentioned transmission picture.

(3) in the X-ray examination method of (2), use X-ray tube as above-mentioned x-ray source, from above-mentioned memorizer read and detect above-mentioned transmission as the time the tube voltage of above-mentioned X-ray tube and the pairing above-mentioned deduction image of combination of above-mentioned X ray grid, and remove above-mentioned scattered x-ray composition.

(4) in the X-ray examination method of (2), has following process: with the above-mentioned sampling frequency at the interval of the pixel that separates above-mentioned predetermined number, on the direction of arranging above-mentioned X ray absorber grid, under the state of not placing above-mentioned inspection object, extract pixel from detected spatial image, obtain and form the process that only has by 2 space abstract images of the interference fringe of the different phase place of above-mentioned predetermined angular degree respectively; Obtain the process of the spatial amplitude distributed image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 space abstract images; Obtain above-mentioned spatial image has been passed through in expression the pixel value of spatial distribution image of distribution of direct X ray composition of above-mentioned X ray grid for the process that likens the above-mentioned deduction image that possesses for pixel value to of the pixel value of above-mentioned spatial amplitude distributed image, and above-mentioned deduction image is stored in the above-mentioned memorizer.

(5) in the X-ray examination method of (2), has following process: use X-ray tube as x-ray source, combination according to one or more tube voltages above-mentioned X ray grid different with one or more scattered x-ray clearances, for detected one or more spatial images under the state of not placing above-mentioned inspection object, above-mentioned sampling frequency with the interval of the pixel that separates above-mentioned predetermined number, on the direction of arranging above-mentioned X ray absorber grid, from above-mentioned spatial image, extract pixel, obtain respectively and to form the process that only has by 2 space abstract images of the interference fringe of the different phase place of above-mentioned predetermined angular degree; Obtain the process of the spatial amplitude distributed image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 space abstract images; Obtain the process that liken the above-mentioned deduction image that for pixel value possess of the pixel value of the spatial distribution image of the distribution of the direct X ray composition that has passed through above-mentioned X ray grid of the above-mentioned spatial image of expression for the pixel value of above-mentioned spatial amplitude distributed image, storage is for the above-mentioned deduction image of above-mentioned each spatial image.

(6) in the X-ray examination method of (2), above-mentioned predetermined number is 1,2, some in 3.

(7) in the X-ray examination method of (2), above-mentioned predetermined angle be 90 the degree, 120 the degree, 180 the degree, 240 the degree, 270 the degree in some.

(8) in the X-ray examination method of (2), use the identical above-mentioned deduction image of obtaining in advance, remove above-mentioned scattered x-ray composition from the image of a plurality of above-mentioned transmission pictures.

(9) in the X-ray examination method of (2), the spatial frequency of the above-mentioned X ray absorber of the arrangement in the detection faces of above-mentioned two-dimensional x-ray detector grid and the difference of above-mentioned sampling frequency are less than sampling frequency.

(10) in the X-ray examination method of (2), set above-mentioned spatial frequency, perhaps/and, set the position of the above-mentioned X ray grid of configuration, make the difference of Nyquist frequency of the spatial frequency of the above-mentioned X ray absorber of the arrangement grid in the detection faces of above-mentioned two-dimensional x-ray detector and above-mentioned two-dimensional x-ray detector less than half value of above-mentioned Nyquist frequency.

(11) in the X-ray examination method of (2), have on the direction of arranging above-mentioned X ray absorber grid arrangement, from the addition image that the pixel value addition of the adjacent a plurality of pixels of the pixel of above-mentioned transmission picture is obtained, above-mentioned sampling frequency with the interval of the pixel that separates above-mentioned predetermined number extracts pixel, obtains the process of above-mentioned abstract image.

(12) X-ray examination method of the present invention has following process: configuration X ray grid between x-ray source that produces X ray and inspection object, to checking that object shines above-mentioned X ray, detect the process of the transmission picture of above-mentioned inspection object with two-dimensional x-ray detector; On the direction of the X ray absorber grid of arranging above-mentioned X ray grid, from above-mentioned transmission image pattern picture, extract pixel, obtain and form the process that only has by 2 abstract images of the interference fringe of the different phase place of predetermined angular degree respectively; Use the distribution of amplitudes image of the distribution of amplitudes of the interference fringe that expression obtains according to above-mentioned 2 abstract images, obtain the process of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the above-mentioned transmission image pattern picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image from the pixel value of the image of above-mentioned transmission picture, remove the process of above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture.

(13) X-ray examination method of the present invention has following process: configuration X ray grid between x-ray source that produces X ray and inspection object, to checking that object shines above-mentioned X ray, detect the process of the transmission picture of above-mentioned inspection object with two-dimensional x-ray detector; With n is integer, and with the space sampling frequency of (1/n) of the above-mentioned space sampling frequency of above-mentioned two-dimensional x-ray detector, the pixel data of the image of above-mentioned transmission picture is sampled, obtain the process that forms 2 abstract images of interference fringe respectively with predetermined inverted phase; Obtain the process of the distribution of amplitudes image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 abstract images; Use above-mentioned distribution of amplitudes image to obtain the process of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the image of above-mentioned transmission picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image from the pixel value of the image of above-mentioned transmission picture, remove the process of above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture.

(14) in the X-ray examination method of (13), n is 2,3, some in 4.

(15) X-ray examination method feature of the present invention is to have following process: by at the X ray grid that dispose between the x-ray source that X ray takes place and the inspection object, and the process of shining above-mentioned X ray to above-mentioned inspection object; Detect the process of the transmission picture of the above-mentioned inspection object that obtains by above-mentioned x-ray bombardment by X-ray detector; According to the amplitude of the interference fringe that in the transmission picture of above-mentioned inspection object, takes place, extract scattered x-ray composition that is included in the above-mentioned transmission picture and the process of removing.

In addition, above X-ray examination method can be applicable to certainly checks that object is the medical X-ray examination method of human body, and to remove beyond the human body with general inspection object be the non-destructive detection method of the baggage check method etc. of object.

If according to the present invention, then, therefore can carry out high-precision scattered x-ray correction owing to remove later on according to the direct scattered x-ray composition that is included in the X ray transmission picture that extracts of the amplitude of interference fringe.In addition,, therefore can eliminate the invalid exposure of detected body, can suppress the amount of being exposed because the X ray grid are configured between x-ray source and the detected body.

Claims (13)

1. an X ray checking device is characterized in that, comprising:

Produce the x-ray source of X ray;

To checking that object shines above-mentioned X ray, detect the two-dimensional x-ray detector of the transmission picture of above-mentioned inspection object;

Be configured in the X ray grid between above-mentioned x-ray source and the above-mentioned inspection object;

The arithmetic processing apparatus of calculation process is carried out in the output of above-mentioned two-dimensional x-ray detector,

Above-mentioned arithmetic processing apparatus carries out following computing, promptly, sampling frequency with the interval of the pixel that separates predetermined number, in the grid orientation of above-mentioned X ray grid, from the image of above-mentioned transmission picture, extract pixel, obtain the computing of 2 abstract images that occur interference fringe respectively, described interference fringe has the only different phase place of predetermined angular; Obtain the computing of the distribution of amplitudes image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 abstract images; Use above-mentioned distribution of amplitudes image to obtain the computing of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the image of above-mentioned transmission picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image, the computing of removing above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture from the pixel value of the image of above-mentioned transmission picture.

2. X ray checking device according to claim 1 is characterized in that, comprising:

Memorizer is used for storing for the distribution of the direct X ray composition that extracts the image that is included in above-mentioned transmission picture and the calibration image of obtaining in advance,

Above-mentioned arithmetic processing apparatus carries out following computing, promptly, from the pixel value of the image of above-mentioned transmission picture, the pixel value that deducts the pixel value of the above-mentioned calibration image of reading from above-mentioned memorizer and above-mentioned distribution of amplitudes image is long-pending, obtains the computing of scattered x-ray distributed image of the distribution of the scattered x-ray composition in the image that expression is included in above-mentioned transmission picture; Deduct the computing of the pixel value of above-mentioned scattered x-ray distributed image from the pixel value of the image of above-mentioned transmission picture, and remove above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture.

3. X ray checking device according to claim 2 is characterized in that:

Use X-ray tube as above-mentioned x-ray source, above-mentioned arithmetic processing apparatus carries out following computing, promptly from above-mentioned memorizer read and detect above-mentioned transmission as the time the tube voltage of above-mentioned X-ray tube and the pairing above-mentioned calibration image of combination of above-mentioned X ray grid, and the computing of removing above-mentioned scattered x-ray composition.

4. X ray checking device according to claim 2 is characterized in that:

Above-mentioned arithmetic processing apparatus carries out following computing, promptly, above-mentioned sampling frequency with the interval of the pixel that separates above-mentioned predetermined number, in the grid orientation of above-mentioned X ray grid, never place in the spatial image detected under the state of above-mentioned inspection object and extract pixel, obtain the computing of 2 space abstract images that occur interference fringe respectively, described interference clause has the different phase place of only above-mentioned predetermined angular; Obtain the computing of the spatial amplitude distributed image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 space abstract images; Obtain the computing of above-mentioned calibration image, above-mentioned calibration image be expression passed through the pixel value of spatial distribution image of distribution of direct X ray composition of above-mentioned X ray grid of above-mentioned spatial image and above-mentioned spatial amplitude distributed image pixel value liken the calibration image that has for pixel value to

Above-mentioned arithmetic processing apparatus is stored in above-mentioned calibration image in the above-mentioned memorizer.

5. X ray checking device according to claim 2 is characterized in that:

Above-mentioned arithmetic processing apparatus carries out following computing for above-mentioned each spatial image, promptly, use X-ray tube as x-ray source, combination according to one or more tube voltages above-mentioned X ray grid different with one or more scattered x-ray clearances, for detected one or more spatial images under the state of not placing above-mentioned inspection object, above-mentioned sampling frequency with the interval of the pixel that separates above-mentioned predetermined number, in the grid orientation of above-mentioned X ray grid, from above-mentioned spatial image, extract pixel, obtain the computing of 2 space abstract images that occur interference fringe respectively, described interference fringe has the different phase place of only above-mentioned predetermined angular; Obtain the computing of the spatial amplitude distributed image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 space abstract images; Obtain the computing of above-mentioned calibration image, above-mentioned calibration image be expression passed through the pixel value of spatial distribution image of distribution of direct X ray composition of above-mentioned X ray grid of above-mentioned spatial image and above-mentioned spatial amplitude distributed image pixel value liken the calibration image that has for pixel value to

Above-mentioned arithmetic processing apparatus has the memorizer of storage for the above-mentioned calibration image of above-mentioned each spatial image.

6. X ray checking device according to claim 2 is characterized in that:

Above-mentioned arithmetic processing apparatus uses the identical above-mentioned scattered x-ray distributed image of obtaining in advance, carries out removing from the image of a plurality of above-mentioned transmission pictures the computing of above-mentioned scattered x-ray composition.

7. X ray checking device according to claim 2 is characterized in that:

The difference of the spatial frequency of the above-mentioned X ray absorber of the arrangement in the detection faces of above-mentioned two-dimensional x-ray detector grid and the Nyquist frequency of above-mentioned two-dimensional x-ray detector is less than half value of above-mentioned Nyquist frequency.

8. X ray checking device according to claim 2 is characterized in that:

Set above-mentioned spatial frequency or/and set the position of the above-mentioned X ray grid of configuration, make the difference of Nyquist frequency of the spatial frequency of the above-mentioned X ray absorber of the arrangement grid in the detection faces of above-mentioned two-dimensional x-ray detector and above-mentioned two-dimensional x-ray detector less than half value of above-mentioned Nyquist frequency.

9. X ray checking device according to claim 2 is characterized in that:

Above-mentioned arithmetic processing apparatus carries out following computing, promptly, on the direction of arranging above-mentioned X ray absorber grid, from the addition image that the pixel value addition of adjacent a plurality of pixels of the pixel of above-mentioned transmission picture is obtained, above-mentioned sampling frequency with the interval of the pixel that separates above-mentioned predetermined number extracts pixel, obtains the computing of above-mentioned abstract image.

10. X ray checking device according to claim 1 is characterized in that:

Above-mentioned arithmetic processing apparatus carries out following computing, that is, in the grid orientation of above-mentioned X ray grid, from above-mentioned transmission image pattern picture, extract pixel, obtain the computing of 2 abstract images that occur interference fringe respectively, described interference fringe has the only different phase place of predetermined angular; Use the distribution of amplitudes image of the distribution of amplitudes of the interference fringe that expression obtains according to above-mentioned 2 abstract images, obtain the computing of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the above-mentioned transmission image pattern picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image, the computing of removing above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture from the pixel value of the image of above-mentioned transmission picture.

11. an X ray checking device is characterized in that, comprising:

Produce the x-ray source of X ray;

To checking that object shines above-mentioned X ray, detect the two-dimensional x-ray detector of the transmission picture of above-mentioned inspection object with predefined space sampling frequency;

Be configured in the X ray grid between above-mentioned x-ray source and the above-mentioned inspection object;

The arithmetic processing apparatus of calculation process is carried out in the output of above-mentioned two-dimensional x-ray detector,

Above-mentioned arithmetic processing apparatus carries out following computing, promptly, with n is integer, and with the space sampling frequency of the 1/n of the above-mentioned space sampling frequency of above-mentioned two-dimensional x-ray detector, the pixel data of the image of above-mentioned transmission picture is sampled, obtain the computing of 2 abstract images that occur interference fringe respectively, described interference fringe has predetermined inverted phase; Obtain the computing of the distribution of amplitudes image of the distribution of amplitudes of representing interference fringe according to the difference of the pixel value between above-mentioned 2 abstract images; Use above-mentioned distribution of amplitudes image to obtain the computing of scattered x-ray distributed image that expression is included in the distribution of the scattered x-ray composition in the image of above-mentioned transmission picture; Deduct the pixel value of above-mentioned scattered x-ray distributed image, the computing of removing above-mentioned scattered x-ray composition from the image of above-mentioned transmission picture from the pixel value of the image of above-mentioned transmission picture.

12. X ray checking device according to claim 11 is characterized in that:

N is some in 2,3,4.

13. an X ray checking device is characterized in that, comprising:

The x-ray source of X ray takes place;

To checking that object shines above-mentioned X ray, detect the X-ray detector of the transmission picture of above-mentioned inspection object;

Be configured in the X ray grid between above-mentioned x-ray source and the above-mentioned inspection object,

Based on the amplitude of the interference fringe that in the transmission picture of above-mentioned inspection object, produces, extract the scattered x-ray composition be included in the above-mentioned transmission picture and with its removal.

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