KR100952326B1 - Multi-energy X-ray imaging system for quasi-monochromatic X-ray - Google Patents

Abstract

The present invention relates to a quasi-monochrome multi-energy X-ray photographing apparatus, comprising: a light source unit generating and emitting X-rays and moving an X-ray focus in a predetermined direction; and a multicolor X mounted on the light source unit and emitted from the light source unit. An optical filter installed to scan a subject by emitting a ray with multiple energy of a semi-monochromatic color, and a signal detection detector configured to detect X-rays passing through the subject to obtain multi-energy image information; The filter has a plurality of reflectors mounted so that the multi-color X-rays are incident at substantially the same angle, and a shutter for selectively blocking the quasi-monochrome dual energy reflected and emitted from the reflectors, the reflectors reflecting mirrors At least one pair of materials of different thicknesses It has alternately arranged in the configuration.

According to this configuration, since spectral regions of multiple energies are clearly distinguished, a clean image can be obtained at a low exposure amount when adjusted to use an optimal energy value.

X-ray, shooting, double energy, filter, multilayer, reflector

Description

Multi-energy X-ray imaging system for quasi-monochromatic X-ray

The present invention relates to a quasi-monochrome multi-energy X-ray imaging apparatus, and more particularly, by photographing using a quasi-monochrome multi-energy, the spectral region of the multi-energy is clearly distinguished and a clean image can be obtained at a low exposure amount. The present invention relates to a quasi-monochrome multi-energy X-ray imaging apparatus.

X-ray photography is recognized as essential for medical diagnosis in that it provides visual information of the internal structure of the human body, and efforts to obtain clearer images while reducing exposure to patients and lesions Attempts have been made to apply a variety of techniques to better represent the areas present.

Among them, X-ray photographs with monochromatic light are known to have high utilization value because they can increase the absorption contrast of a subject and can reduce the amount of exposure by removing the extra X-rays that are scattered and impair image quality. have. In particular, in the case of a technique using two kinds of image signals photographed with dual energy, the use of quasi-monochrome X-rays is superior to the contrast enhancement due to background disappearance, compared to the use of multi-color X-rays. In addition, having a similar X-ray absorption coefficient, it has been found that it is more effective in distinguishing between materials with low absorption contrast.

For example, in the case of dual energy subtraction of angiography using contrast medium, X-rays of two kinds of energy set in a region lower and higher than the K-edge absorbed energy of the contrast medium as shown in FIG. (101) and (102), the image quality of the image is greatly affected by the shape and energy range of the incident beam spectrum. Here, K-edge absorption refers to the X-ray absorption band according to the electronic structure of the elements, and when light energy above the energy gap between the electron orbitals 1s and 2s2p of any material is supplied, the light is absorbed to ionize the K shell 1s electrons. And action involving photoemission occurs.

The absorption coefficient rapidly increases at the point immediately after exceeding the energy gap, and decreases again as the energy continues to increase beyond that. Since the energy gap is an element-specific value, the K-edge energy varies from element to element, and the K-edge energy of iodine, a commonly used contrast agent, is known to be 33.164 keV. That is, administration of the contrast agent not only increases the X-ray absorption coefficient but also divides the absorption coefficient into a large and a small place according to the X-ray energy to be photographed.

The dual energy subtraction method uses the principle that when a subject image is obtained from two energy regions having a large difference in X-ray attenuation coefficients and subtracted, the portions of the two energy regions that do not have a large difference in absorption disappear. In energy subtraction, two images obtained in the nearest energy region before and after the K-edge energy of the contrast agent are subtracted to have a good background extinction effect, and the contrast of the contrast agent is maximized.

However, in the multi-color X-ray, since the spectrum of the incident beam has a wide width, it is difficult to prevent the two spectra from overlapping while adjoining the energy value before and after the K-edge energy value, thereby satisfying the purpose of the dual energy subtraction method. There is big distance from condition to let. On the other hand, in the case of using monochromatic light, by adjusting two types of X-ray energy before and after the K absorption edge energy of the contrast agent, the difference in absorption coefficient can be widened, thereby maximizing the effect of the dual energy subtraction method.

Monochromatic X-rays can be made using a monochromator that filters only certain wavelengths in polychromatic X-rays. Monochromators include single crystals and multilayer thin films in which Bragg diffraction occurs.

Bragg Diffraction Law

Here, E is energy in diffracted keV (kiloelectron Volt) units (other light bands are extinguished), n is an integer greater than or equal to 1, d is a diffraction grating distance in units of ,, θ is an incident beam and an incident plane Incident angle.

As a technique related to the dual energy subtraction method, a monochromatic angioplasty experiment using an electron accelerator and a single crystal monochromator combination is known, but more practically, a HOPG (Highly Oriented Pyrolytic Graphite) monochromator is used. HOPG is a quasi-monochrome X-ray with Gaussian distribution and high reflectivity because the array of gratings in which X-rays are Bragg diffracted is not a perfect arrangement like a single crystal. Combinations can be excellent monochromatic tools.

G. Baldazzi et al. Used HOPG in "IEEE NSS MIC 2001 Conference Record, San Diego (Ca), November (2001)" to produce two types of high and low incident beams with peaks of 31.7 keV and 34.7 keV, respectively. It is revealed. Here, the spectra were narrowed so that they did not overlap each other in the K-edge energy of iodine.As a result of performing double energy subtraction with different iodine contrast concentrations and diameters of tubes containing liquids, the amount of exposure decreased and contrast and It demonstrates the possibility of employing a quasi-monochrome X-ray by showing a very good characteristic with improved sensitivity. However, there is a problem in that the amount of reflected quasi-monochromatic light is increased and the field size of the X-rays exposed to the subject is increased to lower the noise level and reduce the shooting time.

HW Schnopper et al., In "Proc. SPIE (2001), attempted to apply a combination of multilayer thin films and laser-induced plasma X-rays, which were prepared by alternately depositing a pair of materials with low electron density and high electron density. . The multilayer acts as a monochromator by Bragg's law of diffraction, and the thickness of a pair of materials is equal to the lattice constant size of a single crystal. The multilayer can control the size and width of the reflected energy according to the material and the structure, and in the high energy range of several tens of keV, the value is higher than the reflectance of the HOPG. to be. HW Schnopper et al. Wanted to increase the monochromaticity by filtering the characteristic X-ray bands of the anode target material of the X-ray tube using multilayers, and mentioned how to use multiple multilayers simultaneously to reduce the shooting time. The results were not presented.

Another example of radiography using dual energy subtraction is mammography. Because the x-ray absorption coefficient is small, the constituent tissues of the breast typically use an energy near 20 keV that is much smaller than the X-ray energy exposed to other parts of the human body, thereby obtaining contrast-contrast images. In this case, since a large amount of radiation is absorbed by the human body, a method of reducing dose if possible while maintaining contrast is always studied, and a double energy subtraction method using quasi-monochrome X-rays may be the answer. In mammography without contrast, there is no significant change in absorption coefficient due to K-edge absorption, so the reduction of two dual-energy image signals has no effect, the use of appropriate subtraction algorithms and the appropriate X-ray energy bands. The use of is required. M. Marziani et al., "Phys. Med. Biol. 47, 305 (2002)", describe the basic experimental results of dual-energy mammography of semi-monochromatic light using HOPG, and K. Bliznakova et al. 41, 4497 (2006), show the effect of dual energy imaging through computer simulations for dual energy mammography of monochromatic and polychromatic light.

The use of quasi-monochrome x-rays with a narrow energy spectrum is more effective for the dual energy subtraction method than multi-color x-rays. There is a lack of technology for practical use of a method such as to have a light distribution.

SUMMARY OF THE INVENTION An object of the present invention is to provide a quasi-monochrome multi-energy X-ray imaging apparatus capable of generating quasi-monocolor multi-energy from one X-ray source and implementing various scanning techniques.

Another object of the present invention is to provide a quasi-monochrome multi-energy X-ray imaging apparatus capable of clearly distinguishing spectral regions of multi-energy, thereby obtaining a clear image at a low exposure amount.

It is still another object of the present invention to provide a quasi-monochrome multi-energy X-ray imaging apparatus which is capable of shortening the imaging time by performing scanning imaging using a plurality of reflectors and useful for photographing a large-area subject.

According to the present invention, a light source unit which generates and emits X-rays and whose X-ray focus is moved in a predetermined direction, and the multi-color X-rays which are mounted on the light source unit and emitted from the light source unit are discharged as semi-monochromatic multi-objects. And an optical filter installed to scan an optical filter, and a signal detection detector configured to detect X-rays passing through the subject to obtain multi-energy image information. The optical filter includes an angle at which the multi-color X-rays are substantially the same. It has a plurality of reflectors mounted to be incident to the light, and a shutter for selectively blocking the quasi-monochrome dual energy reflected and emitted from the reflectors, the reflectors are formed of a different thickness of the pair of materials constituting the multilayer thin film Quasi-monochrome multi-energy X-ray imaging system characterized in that the arrangement is one or more The ball.

The present invention also provides a light source unit which generates and emits X-rays and whose X-ray focus is movable in a predetermined direction, and emits multi-color X-rays which are mounted on the light source unit and emitted from the light source unit as quasi-mono-color multiple energy. And an optical filter installed to scan the subject and a signal detection detector configured to detect X-rays passing through the subject to obtain multi-energy image information. The optical filter includes a material forming a multilayer thin film. And a plurality of reflectors having the same thickness and a shutter for selectively blocking the semi-monochrome dual energy emitted and reflected from the reflectors, wherein the reflectors are mounted with different incidence angles of multi-color X-rays. It provides a semi-monochrome multi-energy X-ray imaging apparatus, characterized in that arranged alternately.

The photographing apparatus of the present invention generates quasi-monochromatic light from a commercial X-ray light source. In particular, the energy and width of the quasi-monochromatic light are approximated before and after the K-edge of the X-ray contrast medium, so that the spectrum does not overlap, and the contrast medium is used. Double energy subtraction angiography has improved contrast and sensitivity effects. And in the dual energy shooting without the contrast agent, you can adjust the energy value and energy width that produce the greatest effect.

When the reflectors are aligned in a predetermined direction, angle, interval, etc., the incident intensity can be increased to shorten the photographing time and improve the uniformity of the incident intensity.

The optical filter has a wall provided to block the multi-color X-rays passing through the reflecting mirrors, and a rear having a groove formed between the walls to pass the quasi-monochrome X-rays reflected and emitted from the reflecting mirrors. You may have more slits. The wall and the groove of the rear slit may be installed to align on a concentric circle having an origin that is substantially the same as the concentric circle on which the reflector is arranged. The wall of the rear slit may be extended to adjust the width of the reflected beam reflected from the reflector.

The apparatus may further include a collimator unit equipped with a collimator having an opening to adjust the size of the X-ray beam emitted from the optical filter and irradiated onto the subject. And the collimator may be installed to be movable so that the distance to the light source unit is adjusted.

In addition, the reflectors may be installed to be rotatable together with a precision of a predetermined angle about a selected point.

In addition, the reflector is installed so that the incident angle of the X-ray is less than 1 degree, the pair of materials constituting the multilayer thin film of the reflector is set to 1.5 nm ~ 8 nm thickness semi-monochrome X- between 10 keV ~ 100 keV It can be configured to reflect the line.

In addition, the moving direction of the X-ray focus may be set in a linear direction or a rotation direction.

In addition, according to the device of the present invention, it is possible to take a picture by the semi-monochrome dual energy, and mount the reflectors in half and half for high energy and low energy, and cover the low energy reflector when shooting high energy, and the high 2 shots can be taken by covering the energy use, or 2 shots are taken with alternating reflectors alternately, and the shots are taken by dividing the detection time of the signal detector (digital detector) into appropriate frames to accumulate the signals, And combine the low energy frame with each other to obtain an image for each of the dual energies, or take two scans with a homogeneous reflector. After one shot, reflect the mirror chamber by rotating the reflector chamber around an axis through the thickness of the reflector. Use the energy adjustment method to retake by changing the energy of monochromatic light, or 1 reflector A variety of recording methods, such as by using the line detectors of the first line corresponding to scanning and recording, the reflecting mirror 2 to be the one dual-energy scanning-up to take a picture using the line detectors of each bar and 2 are possible.

According to the imaging device of the present invention, since the spectral regions of multiple energies are clearly distinguished, a clean image can be obtained at a low exposure amount when adjusted to use an optimal energy value.

In addition, scanning imaging is performed by using a plurality of reflectors, which shortens the shooting time, is useful for photographing a large-area subject, and is effective in eliminating partial nonuniformity of light intensity.

In addition, it is possible to generate multiple monochromatic energies from one X-ray source, enabling the implementation of a variety of scanning techniques at low cost.

Hereinafter, the apparatus of the present invention will be described in more detail with the use of dual energy.

Figure 2 is a conceptual diagram showing an overall monochrome mono-energy X-ray imaging apparatus according to the present invention.

The X-ray imaging apparatus of the present invention includes a light source unit 10, a signal detection detector unit 20, and a collimator unit 30.

The light source unit 10 has an optical filter 40 for filtering multi-color X-rays to a semi-monochromatic color, and the quasi-monochrome function of the optical filter 40 is expressed by the multilayer reflector 42.

The multilayer reflector 42 is a structure in which dozens to hundreds of nm thin films 42a and 42b are coated on a glass substrate 43 having a thickness of less than 1 mm and having a very flat surface, as shown in FIG. The energy reflected is determined by the incident angle corresponding to the fasting incident angle and the thickness of the pair of materials constituting the multilayer thin film.

This multilayer reflector 42 reflects only a certain portion of energy in the primary beam incident on the reflector, and the spectrum has some narrow band width. Reflective energy and band width are inherent to the reflector, which is determined by the adjustment of the angle of incidence, the thickness of the material, the pair of materials, the number of layers of the materials, and so on.

Actual commercial X-ray light sources emit beams at a wide angle of several tens of degrees from a focal spot, so the angle of incidence varies depending on the distance of focus and the reflecting mirror that is constantly tilted. As the reflector moves away from the focal point in the same longitudinal direction as the beam propagation direction, the angle of incidence becomes smaller and smaller, and even at the same distance, the angle of incidence does not have a single value but has a range of widths. Therefore, it is necessary to set a multi-color X-ray light source according to the use and to manufacture and use a thin film of the reflector.

In the present invention, the thickness of the pair of materials constituting the multilayer thin film is about several nm, and the energy of the semi-monochromatic light reflected is set to be 10 keV or more at an angle of incidence of less than 1 degree, and the thickness of the pair of materials constituting the multilayer thin film is There is no limit to the constant. More specifically, using a commercially available X-ray light source and optical filter, the thickness of the thin film pair is 1.5 nm or more and 8 nm or less in the case of using iodine contrast agent in angiography, including mammography, and other imaging. With an incident angle of less than 1 degree, the number of layers can be adjusted to a maximum of 200 layers and a minimum of 5 layers to determine the reflected energy value and the width of the spectrum. The energy range of the reflected X-rays controlled in this condition is between about 10 keV and 100 keV.

The multi-layer reflectors 42 are fixed to the reflector chamber 44 by arranging them at predetermined reflection angles and intervals, and the reflector chamber 44 constitutes a frame constituting the light source unit 10 to be aligned with the X-ray light source. 12 is fixedly installed. That is, the X-ray light source, the reflector chamber, and the reflector are integrally formed to form the light source unit 10 of the semi-mono light source device, and the semi-mono light source is along a preset path as shown by the focal point S1 (S2) in FIG. 2. It is configured to scan the subject by performing a linear movement or to rotate the movement around the focus (S1) (S2) as shown in (c) of FIG.

A plurality of multi-layer reflectors 42 are fixed to the reflector chamber 44 so as to be arranged in concentric circles at a predetermined reflection angle and a predetermined interval. In this case, the reflection angle is defined as the origin of the focal spots (S1, S2, etc.) of the multicolor X-ray light source and the multilayer thin film substrates (reflectors) satisfying Bragg diffraction conditions are arranged at right angles on a concentric circle of radius r. The angle between the reflector and the radial line connecting the circumference of the concentric circle with the center and reflectors arranged. At this time, the spacing of the reflectors may be determined according to the intended use. Preferably, the spacing of the reflectors is set to a minimum so as to filter most of the X-rays. In addition, the minimum value of the distance between the reflecting mirrors is influenced by the length of the reflecting mirror and the thickness of the substrate, and it is preferable to set the reflecting beam to pass as much as possible without passing the incident beam between the reflecting mirrors.

The penetration depth through which multi-color X-rays incident on the reflector can pass through without being dissipated by scattering and absorption by the thin film and substrate material is not so great at low angles of incidence of less than 1 degree, When the energy range is up to hundreds of keVs, high-energy regions of tens of keVs or more can pass through thin substrates. Such straight X-rays can be blocked by shielding the back side of the board with a heavy metal material when the reflector is arranged in a large distance or when using a small number of reflectors of 2 or 3 or less, but the reflectors are arranged as closely as possible or In the case of a large number, a separate blocking device should be provided.

The light source unit 10 of the present invention is configured to block the straight beam passing through the reflector without being absorbed or scattered by installing a slit-shaped structure behind the reflector fixed to the reflector chamber 44 as shown in FIG. . The structure is placed on a concentric circle having the same origin as the concentric circle on which the reflecting mirrors 42 are arranged to function to open or block a part of the space on the circumferential line of the concentric circle, hereinafter referred to as the rear slit 46.

The rear slit 46 is formed to have a groove 47 that is open to allow light to move, and a wall 48 that blocks the path of light between the grooves 47, and a gap or wall between these grooves 47. The gap between the 48 can be determined to have an appropriate value depending on the spacing of the reflector and the substrate thickness. In other words, the gap between the groove 47 or the wall 48 is determined by the width and spacing of the reflection beam of the reflector chamber geometry shown in FIG. 2.

The wall 48, which is a blocked portion of the rear slit 46, is set so that its size (width) is obscured by the end thickness portion of the reflector adjacent thereto, and the width of the wall 48 passes through the groove 47. The preset extra length may be added to adjust the width of the reflected beam. The portion 48a added in the reflection direction of the X-ray of the added portion blocks the reflected beam reflected from the reflector portion far away from the light source, and the portion 48b added in the opposite direction is the reflected beam reflected from the portion close to the light source. It functions to block. In this way, when the width of the reflected beam passing through the rear slit 46 is adjusted, the width of the reflected beam reflected by each of the plurality of reflectors can be the same, so as to act as a uniform light source when capturing an image including scanning. can do.

A structure for generating a semi-monochrome dual energy using an optical filter installed in the photographing apparatus of the present invention and a method for performing imaging using the dual energy are as follows.

Since the energy of the X-rays filtered by the optical filter 40 depends on the thickness of a pair of materials constituting the multilayer thin film of the reflector and the incident angle of the reflector chamber, the dual energy is adjusted in one optical filter by adjusting two factors. Can be implemented.

As a form of structure, the reflector chamber is manufactured to suit two kinds of angles of incidence. That is, the reflector chamber has a structure in which the reflectors can be mounted so that the incident angles of the X-rays incident on the reflectors can be two kinds, and when the reflectors having the same pair of thicknesses are mounted in the reflector chamber, The reflector installed reflects the low energy band X-rays, and the reflector installed in the small incident angle reflects the high energy band X-rays. The reflector chamber may have a structure in which reflectors are alternately arranged to have different incidence angles as shown in (a) of FIG. 8, and have the same incidence angle in two pairs as shown in (b) of FIG. Each pair may have a structure in which the pairs are alternately arranged to have different incidence angles, or three or more reflectors may have a structure in which the pairs are alternately arranged to have different incidence angles. . Alternatively, as shown in (c) of FIG. 8, the reflectors may be arranged to have different incidence angles on both sides with respect to the center of the reflector chamber. In this case, the ratios of the reflectors having different incidence angles need not be the same as 50%, and the ratio can be appropriately determined in consideration of the adjustment of the amount of light and the convenience of the scanning imaging method.

As a different form of the structure, reflectors having different thicknesses of pairs of materials can be installed in reflector chambers made to have the same angle of incidence.As in the case of the previous case, reflectors are alternately arranged one by one, alternately tied by two or more sheets, or right and left Can be placed in half, and the ratio of the two reflectors is not limited.

As another form of the structure, a combination of the above structures, that is, a structure using reflectors of different thicknesses at different incidence angles is possible.

In addition, a form using the energy tunable function of the optical filter in a manner of generating double energy may be used. When the same reflector is installed in the reflector chamber to have the same angle of incidence, it is possible to change the quasi-monochrome energy band in a certain range by finely adjusting the value of the angle of incidence. That is, when the plurality of reflectors are aligned in a state of being inclined at a constant angle on the concentric circle centered on the X-ray light source focal point and the radius line of the concentric circle, a selected point positioned at the reflector disposed at the center of the arranged reflectors When the reflectors are rotated together, the incident angles of all the reflectors change.

In this case, the angles of incidence of all the reflectors are the same in the state before the reflectors are rotated together, i.e., aligned in a preset position. However, when the reflectors are rotated together about the selected point, the angles of incidence of the reflectors differ slightly. It appears large between the reflectors disposed in the center and the reflectors disposed in both distant directions and becomes larger as the angle of rotation of the reflectors increases. Therefore, this method is preferably used within a range of minute rotation angle, the angle of incidence of the reflecting mirrors is insignificant at a rotation angle of 0.5 degrees or less, a distance of several tens of centimeters from the center of the concentric circle, and a beam divergence angle of 30 degrees. In the case of blocking the reflected beam by the wall, it is useful to reduce the angle of incidence, so it is useful within the angle of incidence and quasi-monochrome energy to be used in the present invention.

For example, in angiography, the angle of rotation of the reflector to adjust the reflection energy within the range of 30 to 35 keV, before and after the K-edge energy of the iodine contrast agent, has a thickness of a pair of materials that make up the multilayer film of the reflector. When it is nm or less, it is 0.05 degrees or less. If the distance between the light source focal point and the reflector is very close to 25 cm or less, more effectively 15 cm or less, a similar effect can be achieved by adjusting the distance between the light source focal point and the reflector.

Although various methods for generating quasi-monochrome dual energy have been presented above, the energy values are not limited to two, and these methods may be used to adjust the energy values to three or more, or may be configured to use only one energy.

The incident angle of the multilayer thin film monochromator for filtering X-rays in the 10 to 150 keV region, which is effective for obtaining a general X-ray image, is very small (less than 1 degree), so the reflected beam is considered even when considering the wide divergence angle of the light source and the distance to the detector. The width of is only a few millimeters, and the quasi-monochromatic light to be filtered varies in some cases but corresponds to a part of the incident multi-color light source, so that the amount of light decreases unless the X-ray generating power of the multi-color light source is greatly increased. have.

Therefore, there is an urgent need for a method for acquiring an image suitable for large-area imaging and a signal-to-noise ratio. The present invention proposes a scanning solution of an optical filter using a plurality of reflectors and an integrated light source equipped therewith as a unique solution. In the present invention, a method of acquiring an image of each of the dual energies is also possible, and in this case, the photographing time is shortened.

In the scanning imaging method of the present invention, when the X-ray light source unit performs linear constant velocity motion in the x direction of FIG. Various types of shooting are possible, and a method suitable for the state of the subject and the shooting purpose can be selected and used.

In the case where three or more reflectors are installed in the reflector chamber, scanning imaging starts at one end 34 of the opening of the collimator 32 in which the bundle of quasi-monochrome light forms the collimator part 30, and then continues to the constant end to the opposite end 35. And / or a rotational motion, or a linear and / or rotational motion in a state where the semi-monochromatic light is exposed to the entire opening of the collimator 32 from the beginning. In addition, the signal detection detector 20 in which the X-ray signal detection is performed in scanning is used in principle as a digital detector having a two-dimensional pixel array of a flat plate. However, when two or less reflectors are used, a line is formed in a single line. It is advantageous to match the detector to the reflected beam. However, this does not mean limiting the use of other types of detectors in each case.

When the focal origin of the multicolor light source is S2, light is emitted at the divergence angle θ1, and one reflector constituting the optical filter reflects the light by the angle φ which is a part of the divergence angle. The plurality of reflectors change the divergence direction of the light by the incident angle, and as a result, the reflected X-rays are emitted from the second virtual light source having the divergence angle of θ2 and the focal point of S1. θ2 varies depending on the number of reflectors, the distance from the origin, and the angle of incidence. Since the reflectors have a thickness, the angle φ by the number of reflectors is always smaller than θ2. And since the thickness portion of the reflector blocks the multi-color incident light, the side intensity shape of the quasi-monochrome light emitted from the optical filter is formed like a wave shown in FIG. In Fig. 4, A represents the intensity profile in the scanning direction of the reflected beam obtained from one reflector, B represents the profile of the reflected beam in a rectangle, and C represents the distance between the reflected beams.

The aperture distance d3 of the collimator 32 allows the semi-monochromatic light to be exposed only to a desired photographing part of the subject, and the aperture distance d3 is the divergence angle θ2, the distance d1 between the light source focus and the collimator 32, the collimator 32 and the subject ( 50) is determined by the geometry, such as the distance d2.

Considering the range that satisfies the practically required effect and practical use range in the present invention, d1 + d2 is about 1 m, the quasi-monochromatic light energy range is 10 to 100 keV, the incident angle is 0.2 to 0.8 degrees, commercial X-ray source Θ1 is 30 degrees or less. Moreover, the reflection angle (phi) which one reflector occupies is about 0.1-0.3 degree. In addition, the width of the reflected beam emitted from the single reflector to the subject is about several millimeters to several tens of millimeters, and if the left and right lengths of the subject are Lo, a maximum of Lo should be scanned with one reflector.

In terms of image quality, it is necessary to obtain a signal-to-noise ratio above a certain level, which means that the amount of light passing through the subject should be above a certain level. When a plurality of reflecting mirrors with the same length are moved, time reduction is achieved by a plurality of times to obtain the same amount of light. The scanning speed can be expressed as the linear motion speed of the light source, but the aperture distance d3 of the collimator set to the size of the subject is divided by the time t taken for all the bundles of the reflecting beams to pass through once, or the left and right distance Lo of the subject. Can also be expressed by dividing by t.

When exposing the same amount of light to a subject, using an optical filter equipped with n reflectors can increase the scanning speed by n times compared to using an optical filter equipped with one reflector, and the restriction on the large area is alleviated. do.

When the structure of the reflector chamber of the optical filter is properly designed, or when the pair of materials constituting the thin film material of the reflector are different in thickness and the dual energy generating zones are divided to the left and right, two or more times to obtain a dual energy image. One shot is taken.

In the case of two shots, first, the optical filter completely blocks the area emitting one type of energy and emits quasi-monochrome light of only one type of energy while moving the light source to acquire scanning information. When it's done, return the light source back to the starting point and reverse the area that emits energy, taking a second scan with a quasi-monochrome light with a different energy to get the image. The method of blocking one area is to block the incident light incident to the reflector chamber with a metal plate shutter (movable cover) which is difficult for X-rays to pass through, or the metal plate shutter 60 blocks the emission of the opposite reflected beam as shown in FIG. You may be provided so that it may have a structure. In the case of using the method of changing the energy by slightly changing the angle of incidence of the reflector, after taking one shot without using the shutter, the angle of incidence of the reflector can be adjusted again to the original state. In other cases, the point where the subject is formed in the detector may be different, which may cause an error when the two images are subtracted, and thus correction is necessary.

Since the two kinds of dual energy emitted from the optical filter are clearly distinguished along the axis orthogonal to the scanning direction (see FIG. 4), the X-ray of any of the dual energies is detected for each detector pixel line in the direction orthogonal to the scanning direction. Because you can see if you are incident, you can take a double energy shot in one shot. However, since one kind of energy does not continue to be incident on a predetermined pixel line because the light source is moving, the signal should be detected by dividing the exposure time by a time frame.

The quasi-monochromatic light passing through the plurality of reflectors has a sawtooth beam intensity profile A as shown in FIG. 4 due to the shadow of the reflector. The profile of the reflected beam is suitably assumed to be one rectangle B, preferably corresponding to the half width of the intensity, and the time frame is designated L / v at the scanning speed v and the distance L between the rectangles. If the width of a pixel line is p, there are as many as L / p lines in L, and the whole pixel line is classified into two kinds of dual energy in one time frame. In the next time frame, the entire pixel is again classified as dual energy, but the pixel position of the dual energy is changed. The pixel position and width corresponding to each of the dual energies are always constant unless they change the emission position of the light source and the distance between the detector and the light source. Will be. If the distance to be scanned is Ld based on the detector length, the number of frames is Ld / L. This number is the minimum number of reflectors required.

The same time frame can be applied to the case where the dual energies are alternately arranged. In this case, scanning imaging can be performed even when the quasi-monochrome X-rays are exposed to the entire subject as shown in FIG. 6. In this case, the minimum number of time frames may be one from the time L / v moved by L and the next time L / v to two.

When the amount of light and the shooting time are limited, one or two numbers of reflectors may be used. In this case, it is preferable to use a linear line detector in which the pixel line of the detector corresponds to the reflected beam. In this case, a large-area subject can be scanned and photographed by simultaneously moving the corresponding line detector together with the light source.

In order to examine the effect of the present invention, it was tested as follows.

After adjusting the concentration of aqueous iodine contrast agent to 11.6 mgI / ml, 23.1 mgI / ml, and 92.5 mgI / ml in acrylic phantom with a square hole of 5 mm width and 30 mm length, the distance between light source and reflector 250 mm , The incident angle of 0.25 degrees, reflector light source focal size 0.3 mm, reflector length 100 mm, reflector thickness 0.5 mm, rear slit and light source distance 355 mm, two scans with semi-monochrome dual energy. Spectrum of the dual energy used for the imaging is shown in Figure 9, each of the central energy values are 30.5 keV, 35.7 keV before and after close to the iodine K-edge energy. (A) is a portion of iodine solution of three concentrations taken with 30.5 keV quasi-monochromatic light, and (b) is a portion of iodine solution of three concentrations taken with 35.7 keV quasi-monochromatic light. The sharper images were obtained because of the large X-ray absorption effect. (c) is a post-subtraction image obtained by the signal subtraction of (a) and (b), in which the gray scale was inverted and shown. The effect of disappearing the background of the acrylic part except the contrast agent part was seen.

1 shows dual energy spectra of quasi-monochromatic and polychromatic light;

2 is a conceptual view showing the photographing apparatus of the present invention as a whole;

3 is a cross-sectional view of a multilayer thin film reflector used in the apparatus of the present invention;

4 shows a scanning direction beam profile of a quasi-monochromatic light used in the present invention;

5 (a) to 5 (c) are schematic diagrams of dual energy scanning imaging using the apparatus of the present invention;

6 is a conceptual diagram of dual energy scanning at a short scan distance using the apparatus of the present invention;

7 shows a rear slit constituting the device of the present invention;

8 (a) to 8 (c) show the arrangement of the reflector used in the apparatus of the present invention;

9 shows a quasi-monochrome dual energy spectrum of the present invention;

10 is a quasi-monochrome dual energy X-ray image and a subtraction method effect image according to the present invention.

[Description of Reference Numerals]

10: light source

12: frame

20: signal detection detector

30: collimator part

32: collimator

40: optical filter

42: reflector

44: reflector chamber

S1, S2: Focus

50: subject

60: shutter

Claims (11)

A light source unit which generates and emits X-rays and which moves the X-ray focus in a predetermined direction; An optical filter mounted on the light source unit and installed to emit multi-color X-rays emitted from the light source unit as quasi-mono-color multiple energy to scan the subject; A signal detection detector configured to detect X-rays passing through the subject to obtain multi-energy image information, The optical filter, A plurality of reflectors mounted so that the multi-color X-rays are incident at substantially the same angle, It has a shutter for selectively blocking the quasi-monochrome dual energy reflected and emitted from the reflectors, The reflectors, A quasi-monochromatic multi-energy X-ray imaging apparatus, characterized in that one or more different thicknesses of a pair of materials constituting the multilayer thin film of the reflector are alternately arranged. A light source unit which generates and emits X-rays and which moves the X-ray focus in a predetermined direction; An optical filter mounted on the light source unit and installed to emit multi-color X-rays emitted from the light source unit as quasi-mono-color multiple energy to scan the subject; A signal detection detector configured to detect X-rays passing through the subject to obtain multi-energy image information, The optical filter, A plurality of reflectors having the same thickness of the pair of materials constituting the multilayer thin film, It has a shutter for selectively blocking the quasi-monochrome dual energy reflected and emitted from the reflectors, The reflectors, A quasi-monochromatic multi-energy X-ray imaging apparatus, characterized in that one or more of the multi-color X-rays are mounted in alternating angles. The method according to claim 1 or 2, The optical filter, And a rear slit having a wall installed to block the multi-color X-rays passing through the reflectors and a groove formed between the walls to pass the quasi-monochrome X-rays reflected and emitted from the reflector. Semi-monochrome multi-energy X-ray imaging apparatus characterized by. The method according to claim 3, The wall and groove of the rear slit, And the reflector is arranged to align on a concentric circle having substantially the same origin as the concentric circle on which the reflector is arranged. The method according to claim 3, And the wall of the rear slit extends to adjust the width of the reflected beam reflected from the reflector. The method according to claim 1 or 2, And a collimator having a collimator having an opening to adjust the size of the X-ray beam emitted from the optical filter to the subject. The method according to claim 6, The collimator is a semi-monochromatic multiplex X-ray imaging apparatus, characterized in that installed so as to be moved so that the distance to the light source. The method according to claim 1 or 2, And the reflectors are installed to be rotatable together with a precision of a predetermined angle about a selected point. The method according to claim 1 or 2, The reflector is installed so that the incident angle of the X-ray is less than 1 degree, and the pair of materials constituting the multilayer thin film of the reflector is set to 1.5 nm to 8 nm in thickness to provide a quasi-monochrome X-ray between 10 keV and 100 keV. Semi-monochrome x-ray apparatus characterized in that the reflection. The method according to claim 1 or 2, And the moving direction of the X-ray focal point is a linear direction. The method according to claim 1 or 2, And a direction of movement of the X-ray focal point is a rotational direction.

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