JP2004294233A - X-ray spectral microscopic analyzing method and photoelectric conversion type x-ray microscopic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an X-ray spectral microscopic analyzing method for precisely calculating the compositional distribution of a specimen, especially a physiological specimen constituted of low atomic weight elements. <P>SOLUTION: A specimen is irradiated with X rays using a photoelectric conversion type X-ray microscopic device while sweeping a wavelength to acquire an X-ray absorbing image at every wavelength and the absorption spectra of the designated part on the specimen at the time of measurement are synthesized to detect elements contained from an absorption terminal structure. A plurality of linear simultaneous equations, which are related to the difference between absorbances at wavelengths on both sides of the absorption terminals of the respective elements detected, the surface densities of the respective elements and the difference between absorption coefficients at respective wavelengths, are solved to calculate the proximity values of the surface densities of the respective elements and residual spectra are formed by subtracting the absorption spectra calculated from the surface density proximity values from absorption spectra at the time of measurement to detect new elements. The same plurality of linear simultaneous equations are formed with respect to all of elements detected and solved. Further, when the new elements can not be detected by calculating the surface density proximity the surface densities of the respective elements are set based on the final surface density proximity values. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an X-ray spectroscopic microanalysis method for measuring a composition distribution by identifying and quantifying constituent elements at various points of a sample using a photoelectric conversion type X-ray microscope apparatus. In particular, it relates to the measurement of trace constituent elements in biological samples and the like.
[0002]
[Prior art]
Conventionally, as a method for measuring trace elements, there is a method of measuring the content of elements using an X-ray absorption edge as disclosed in Patent Document 1, for example, measuring the sulfur content of 1 to several tens ppm. are doing. However, according to this disclosed method, an X-ray detector is arranged at an X-ray spectral angle position corresponding to the X-ray absorption edge of a specified known element such as sulfur, the transmittance before and after the X-ray absorption edge is detected, and the ratio between the two is detected. Is determined by measuring the content rate, and is applied to a predetermined element, and the elemental composition distribution on the sample cannot be measured.
[0003]
As a method for analyzing trace elements, there is a fluorescent X-ray analysis method (for example, see Patent Document 2). In this method, a sample is irradiated with X-rays, and composition analysis is performed by detecting characteristic X-rays that generate contained elements. This method is mainly suitable for the measurement of heavy metal elements. Since relatively light elements such as C, O, and N existing in a living body have low excitation efficiency of fluorescent X-rays, they can satisfy the accuracy required for the measurement. It cannot be done and is not suitable in principle.
[0004]
As a method for measuring the content of an element based on the difference in absorption near the absorption edge of an element, a method using the difference in absorption at wavelengths on both sides of the absorption edge has been proposed (for example, see Non-Patent Document 1). . In this method, the content of an element is calculated from the difference in transmittance at both ends of the absorption edge of the element. Absorbance on the short wavelength side observed for the absorption edge of an element (T_S) And the absorptance (T_L) To T_S  / T_LThen, since this also has the contribution of other constituent elements, it is obtained as follows.
[0005]
T_S  / T_L = Exp [-(μ_CS −μ_CL) ・ Ρ_CX- (μ_{N S} −μ_{N L}) ・ Ρ_NX- (μ_{O S} −μ_{O L}) ・ Ρ_O・ X -...]
Where μ_CS, Μ_CL, Μ_{N S}, Μ_{N L} Are the mass absorption coefficients on the short wavelength side and long wavelength side of carbon and nitrogen, respectively, ρ_C, Ρ_NEtc. represent the density of carbon, nitrogen, etc., respectively, and x represents the thickness of the region.
Here, ρ · x represents the surface density, and this surface density is the content of the element per unit area required.
[0006]
However, in this method, as shown by the above equation, the contribution of absorption by another element contained in the absorption edge portion of a certain element cannot be ignored, and the measurement accuracy is insufficient in measuring the content of the element. there were. In particular, in the measurement of trace elements, there was a problem that even the presence of the absorption edge could not be observed.
[0007]
Further, conventionally, as an attempt to remove the contribution of absorption by another element contained in the absorption edge portion of a certain element, there is molecular analysis using a wavelength in an absorption fine structure (XANES) near the absorption edge region. This method is a method of solving simultaneous equations of X-ray absorption with the element amounts of contained elements obtained at several wavelengths as unknowns.
For example, assuming that the composition of an element of a biological sample composed of oxygen O, nitrogen N, carbon C, and calcium Ca is to be obtained, first, the X-ray absorptivity at wavelengths on both sides of the absorption edge of each element is obtained. The incident and transmitted X-ray doses at a certain wavelength₀ , I, and the transmittance T, the transmittance T and the absorption A can be expressed as follows.
[0008]
T = I / I₀ = Exp [-(μ_Oρ_Ox + μ_Nρ_Nx + μ_Cρ_Cx + μ_Caρ_Cax)
A = -lnT = μ_Oρ_Ox + μ_Nρ_Nx + μ_Cρ_Cx + μ_Caρ_Cax
Here, μ represents the mass absorption coefficient, and ρ represents the density. The subscripts O, N, C, and Ca indicate oxygen, nitrogen, carbon, and calcium, respectively. x represents the thickness of the region, and ρx represents the areal density. Then, since ρx is the element content per unit area, this surface density is the content of the element per unit area to be obtained.
Next, the difference A (dif) of absorption at both ends of the absorption edge of each element is expressed as below.
[0009]
O absorption edge:
A_o(Dif) = (μ₁ ^O−μ₂ ^O) Ρ_Ox + (μ₁ ^N−μ₂ ^N) Ρ_Nx + (μ₁ ^C−μ₂ ^C) Ρ_Cx + (μ₁ ^Ca−μ₂ ^Ca) Ρ_Cax
N absorption edge:
A_N(Dif) = (μ₃ ^O−μ₄ ^O) Ρ_Ox + (μ₃ ^N−μ₄ ^N) Ρ_Nx + (μ₃ ^C−μ₄ ^C) Ρ_Cx + μ₃ ^Ca−μ₄ ^Ca) Ρ_Cax
C absorption edge:
A_o(Dif) = (μ₅ ^O−μ₆ ^O) Ρ_Ox + (μ₅ ^N−μ₆ ^N) Ρ_Nx + (μ₅ ^C−μ₆ ^C) Ρ_Cx + (μ₅ ^Ca−μ₆ ^Ca) Ρ_Cax
Ca absorption edge:
A_o(Dif) = (μ₇ ^O−μ₈ ^O) Ρ_Ox + (μ₇ ^N−μ₈ ^N) Ρ_Nx + (μ₇ ^C−μ₈ ^C) Ρ_Cx + (μ₇ ^Ca−μ₈ ^Ca) Ρ_Cax
Where μ_iIs the wavelength λ before and after the absorption edge of the contained element_iShows the mass absorption coefficient at. For example, the subscript 3 indicates the shorter wavelength of the absorption edge of nitrogen, and the subscript 4 indicates the absorption coefficient at the longer wavelength. Superscripts O, N, C, and Ca indicate oxygen, nitrogen, carbon, and calcium, respectively.
[0010]
From the above four system of equations, ρ_Ox, ρ_Nx, ρ_Cx, ρ_Cax Ask for. In this method, if the target of analysis is known, that is, if the chemical bond species contained in the absorption fine structure is known in the case of molecular analysis, or if the contained element type is known in the case of elemental analysis, the sample is used. The content of the element in can be determined with high accuracy. For example, in the case of a biological sample, the main elements such as carbon, nitrogen, and oxygen can be quantified. However, in the case of elemental analysis, in particular, the purpose is to determine the unknown contained elements in the first place.However, in order to analyze unknown trace elements, it is necessary to analyze all expected elements in advance. For example, it is always necessary to solve a system of equations that are extremely multi-dimensional, and the calculation load becomes extremely large, which is not practical.
[0011]
When using a scanning X-ray microscope using a zone plate as a method for measuring constituent elements in a living body, it is necessary to perform a wavelength sweep in a two-dimensional range in order to measure the composition of all the main elements in the living body. is there. However, in a zone plate type X-ray microscope apparatus, since the focal length differs for each wavelength, measuring in a two-dimensional range requires a long time to adjust the position of the zone plate and scan the two-dimensional range. It was necessary and difficult.
[0012]
[Patent Document 1]
JP 2002-214162 A
[Patent Document 2]
JP-A-8-122281
[Non-patent document 1]
Ito, Shinohara et al. "Measurement of soft X-ray absorption spectroscopy and elemental analysis analysis in soft x-ray absorption spectrum using an electronic zoom tube and elemental analysis in radiation analysis tube) ", Journal of Microscopy, Vol. . 181, Pt 1, January 1966, pp. 54-60
[0013]
[Problems to be solved by the invention]
Therefore, the problem to be solved by the present invention is to provide a simple X-ray spectroscopy for efficiently and accurately calculating the composition distribution of a sample, particularly a biological sample composed of low atomic weight elements, even when the contained element contains an unknown element. An object of the present invention is to provide a microscopic analysis method and a photoelectric conversion type X-ray microscope device.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an X-ray spectroscopic microscopic analysis method of the present invention uses a photoelectric conversion type X-ray microscope apparatus to sweep and irradiate a sample with X-rays at a wavelength to acquire and store an X-ray absorption image for each wavelength. An absorption spectrum is synthesized at a predetermined position on the sample from the obtained X-ray absorption image, the presence or absence of an absorption edge structure of an element is detected based on the absorption spectrum, and the absorption edge of the detected absorption edge structure of each element is detected. A multi-dimensional linear simultaneous equation is established in which the difference between the absorptivity at both wavelengths is the left side, the areal density of each detected element is the independent variable on the right side, and the difference between the mass absorption coefficients at each wavelength is the coefficient of each independent variable. An approximate value of the areal density of each element is obtained by solving the system of linear equations, and the contribution of the absorption spectrum of each element is calculated using the approximate value of the areal density. Subtract to form a residual spectrum, and from this residual spectrum, detect the presence or absence of the absorption edge structure of a new element.If a new element can be detected, the above is applied to all the elements detected so far. A similar multi-dimensional linear simultaneous equation is set up and solved to calculate an approximate value of the areal density of each element. When a new element cannot be detected, the approximate density of the previously obtained area density is used on the sample. It is characterized by the areal density of each element at a predetermined position.
[0015]
In the X-ray spectroscopic microscopic analysis method of the present invention, a photoelectric conversion type X-ray microscope is used. The photoelectric conversion type X-ray microscope converts an X-ray absorption image into an electron beam, enlarges the image at a large magnification, detects the image with a CCD detection element or the like, and forms an image. In the analysis method of the present invention, an X-ray image formed by irradiating a sample by X-ray wavelength sweeping is stored, and a predetermined portion is designated using these to read out the absorption data at each wavelength to absorb the X-ray. Generate a spectrum. Therefore, according to the analysis method of the present invention, a specific portion on a sample can be accurately specified and analyzed based on a greatly enlarged image. Since the designation of the position is simple, it is easy to obtain the composition distribution on the sample.
[0016]
According to the X-ray spectroscopic microscopic analysis method of the present invention, an absorption edge peculiar to an element is found from a shape of an absorption spectrum at a designated portion in a sample, elements contained in the portion are identified, and each identified element is identified. The surface density of each element as an independent variable, the coefficient of absorption at the wavelength on both sides of the absorption edge of each element is used as a coefficient, and a multi-dimensional linear simultaneous equation with independent variables is established for the number of detected elements. Quantified each element.
Using the quantitative value of each element, calculate the absorption spectrum of each element, and calculate the remaining absorption spectrum subtracted from the initial absorption spectrum, the remaining absorption spectrum is the remaining element that has not been identified yet When the scale is enlarged, the structure of the absorption spectrum of the minutely contained element becomes visible.
[0017]
Therefore, the presence or absence of an absorption edge structure is examined by observing the remaining absorption spectrum, and if an absorption edge exists, an element corresponding to the absorption edge is newly identified. The identification of each element is re-established by setting up and solving a multiple simultaneous equation using the data of the first absorption spectrum for all the elements thus identified.
By using this method, starting with a small number of elements, such as carbon, oxygen, and nitrogen, which are always included, detecting other elements one by one, and solving a simultaneous equation, all possible elements can be found from the beginning. It is not necessary to target multiple simultaneous equations having independent variables as many as the number of elements, and it is sufficient to solve a multiple linear simultaneous equation with a relatively small number of elements having only independent variables as many as the detected elements. Therefore, the calculation load is small enough to be practically appropriate.
[0018]
In addition, select the elements that may be contained, specify the wavelengths on both sides of the absorption edge of those elements, select and store the X-ray absorption data at those specified wavelengths, and use the intermittent data to absorb the data. The analysis calculation may be performed on behalf of the spectrum.
The X-ray absorption data used for the analysis is only the X-ray absorption on both sides of the absorption edge of the contained element. Therefore, there is no inconvenience in the analysis if the stored absorption data includes X-ray absorption at the wavelengths on both sides of the absorption edge of the element contained in the sample. Therefore, by selecting elements that may be contained in the sample and recording only data at the wavelengths before and after the absorption edge of those elements, the storage capacity can be reduced and the analysis can be performed in The amount of calculation can be remarkably reduced.
[0019]
Further, in order to solve the above-mentioned problems, the photoelectric conversion type X-ray microscope apparatus of the present invention includes an arithmetic processing unit for spectroscopic analysis, and the X-rays wavelength-swept from behind a sample placed in close contact with the photoelectric conversion surface. The electronic image formed by irradiating the image is magnified by an electronic image magnifying device to form an image on an image detecting unit, and the arithmetic processing unit stores an X-ray absorption image from the image detecting unit in an image memory for each sweep wavelength, When an arbitrary position in the line image is designated, an image signal corresponding to the designated position is extracted for a necessary wavelength and synthesized as a measured X-ray absorption spectrum of the designated portion.
[0020]
The arithmetic processing unit further detects the presence or absence of an absorption edge structure of the element based on the measured X-ray absorption spectrum, and detects the difference between the absorptance at the wavelength on both sides of the absorption edge of the detected absorption edge structure of each element as the left side. The approximate value of the areal density of each element was obtained by solving a multiple simultaneous equation using the areal density of each element as a variable on the right-hand side and the difference of the mass absorption coefficient at both wavelengths as the coefficient of each right-hand side variable. The contribution of the absorption spectrum of each element is calculated using the density approximation, and the remaining spectrum is formed by subtracting the contribution from the measured absorption spectrum, and the shape of the residual spectrum is used to check for the presence or absence of a new element absorption edge structure.
When a new element can be detected, a new approximate value of the areal density of each element is calculated by solving the same multiple-element simultaneous equation for all the elements detected so far, and the new element can be detected. When there is no, the last area density approximate value is used as the area density of each element at the designated position.
[0021]
By using the photoelectric conversion type X-ray microscope apparatus of the present invention, a specific portion on a sample can be accurately specified and analyzed based on a greatly enlarged image. Since the designation of the position is simple, it is easy to obtain the composition distribution on the sample. In addition, the calculation load is not large, and the calculation processing device can use a personal computer. Furthermore, the identification and quantification of elements can be easily performed on a biological sample composed of low atomic weight elements.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
The X-ray spectroscopic microscopic analysis method of the present invention will be described in detail based on the illustrated embodiment.
The method of this embodiment detects the content of an element based on the absorption edge structure appearing in an absorption spectrum obtained by measuring a sample, and solves a multiple linear system of equations relating to the detected element based on the measured absorption spectrum. Estimate the content of the element, calculate the absorption spectrum of the substance with the estimated value of the content, subtract from the measured absorption spectrum to obtain a residual spectrum, and further elements contained by the absorption edge structure appearing in this residual spectrum Find out.
[0023]
Furthermore, based on the measured absorption spectrum, a multiple simultaneous equation for the elements detected so far is established and solved, thereby estimating the content of the contained elements, generating a residual spectrum in the same manner as above, and further generating a residual spectrum. Find the absorption edge structure of another element.
This procedure is repeated, and when a new element can no longer be found, the final estimate is the content of the element contained in the substance.
Therefore, the number of terms in the system of equations is the same as the number of element types discovered so far, and the number of terms gradually increases with repetitive operations. Does not become large.
[0024]
FIG. 1 is a conceptual configuration diagram showing an X-ray microscope device used in the present embodiment. The X-ray microscope device of FIG. 1 includes an X-ray generation device 1, a photoelectric conversion surface 2, an electronic image enlargement device 3, an image detection unit 4, and an arithmetic processing device 5.
The X-ray generator 1 emits X-rays while sweeping the wavelength within an appropriate range using a grating, a total reflection mirror, or the like. Synchrotron radiation may be used. X-rays emitted from the X-ray generator 1 irradiate the photoelectric conversion surface 2.
In the photoelectric conversion surface 2, a photoelectric conversion film having a photoelectric conversion function such as a two-layer structure thin film of a gold thin film and a film of cesium iodide or antimony cesium is disposed behind the support film. A sample to be measured is closely adhered to the surface of the support film, and an X-ray image is formed on the photoelectric conversion surface 2 with a portion where the sample is blocked being shaded. The photoelectric conversion surface 2 emits an amount of photoelectrons corresponding to the intensity of the incident X-ray to the surface at the position where the X-ray is incident, and forms an electron image corresponding to the X-ray image.
[0025]
The electronic image enlargement device 3 extracts photoelectrons from an electron image generated on the surface of the photoelectric conversion surface 2 by an anode, enlarges the image by an objective lens and a projection lens, and enlarges the image to a planar image detection unit 4 at a predetermined distance. Project as an electronic image.
The image detecting section 4 is a functional element for visualizing an electronic image, and is constituted by, for example, a microchannel plate (MCP) and a fluorescent screen provided behind the microchannel plate (MCP) to provide a visible image that can be observed by a person. An electrical signal can be generated by an optical system having a built-in relay lens provided behind the fluorescent screen and a CCD camera.
[0026]
The image signal converted into an electric signal by the image detection unit 4 is displayed on a monitor as an image suitable for the purpose of measurement by performing appropriate image processing, and is also sent to the arithmetic processing unit 5, where the analysis processing is performed. Is
The arithmetic processing unit 5 includes a large number of image memories corresponding to the pixels of the X-ray absorption image formed by the image detection unit 4, and can store the X-ray absorption image for each wavelength as a grayscale image.
[0027]
The X-ray absorption image stored in the image memory has a larger amount of information as the wavelength increment is smaller, and thus has a greater degree of freedom in subsequent calculations, but requires a large memory capacity. For identification and quantification of contained elements by the analysis method of the present invention, data at wavelengths before and after the absorption edge of contained elements are used, and the others are not used.
Therefore, when elements that may be contained in the sample are determined, it is sufficient to store absorption images at predetermined wavelengths before and after the absorption edge of those elements. Therefore, in an actual analyzer, by storing only an X-ray absorption image at a wavelength relating to an element that can be detected, simplification of the apparatus and simplification of calculation can be achieved.
[0028]
FIG. 2 is a table listing examples of wavelengths at the absorption edge and wavelengths used for analysis on both sides of the absorption edge for main elements constituting the living body. For example, nitrogen has an absorption edge at a position of 3.099 nm, and the difference between the absorption rates at 3.0 nm and 3.15 nm before and after the absorption edge can be used for analysis. In addition, carbon has an absorption edge at 4.368 nm. For example, the absorption rates at 4.25 nm and 4.45 nm may be used for analysis.
[0029]
FIG. 3 is a flowchart illustrating an analysis procedure performed by the arithmetic processing unit 5.
When performing X-ray spectroscopic microscopic analysis, first, a parameter i representing the number of loop calculations is reset (S1). Next, when the operator specifies a portion to be analyzed via the monitor, data of a pixel position on the image memory corresponding to the specified portion is read, and a zero-order absorption spectrum having wavelength as an independent variable is generated. (S2). The 0th order spectrum is the original X-ray absorption spectrum observed for the sample.
The absorption spectrum may be generated by taking wavelengths at appropriately dense intervals, or, as described above, may be a spectrum that focuses only on the wavelength used for analysis and ignores other wavelengths. .
[0030]
FIG. 4 is a 0th-order absorption spectrum diagram created for the simplified model substance. The absorption spectrum of FIG. 4 shows that the sample contains only carbon, oxygen, nitrogen, calcium, and iron, and the areal densities of carbon, oxygen, and nitrogen are both 1 × 10^-6g / cm², Calcium is 1 × 10^-7g / cm²1 × 10 iron^-8g / cm²Indicates when. The absorption spectrum shows only the absorptance at the wavelength on both sides of the absorption edge of each element. The arrows indicate the wavelength positions of the respective absorption edges, and the black dots in the graph indicate the absorption at the wavelength used for the analysis calculation.
[0031]
By observing such a zero-order absorption spectrum, the presence or absence of an absorption edge structure is determined (S3). In FIG. 4, only oxygen O, nitrogen N, and carbon C show an obvious absorption edge structure. Therefore, the number i of loop operations is incremented to 1 (S4), the newly identified element type (initially O, N, C) is added, and the number of elements identified so far is Ni (here, 3). (S5).
[0032]
Then, using the data of the 0th-order absorption spectrum, the difference A of the X-ray absorption by the entire sample at the wavelengths on both sides of the absorption edge of each element identified._a(Dif) (a represents the identified element) is calculated and placed on the left side, and on the right side is the mass absorption coefficient μ of each element j at the wavelength k on both sides of the absorption edge._k ^jArea difference ρ using the difference between the absorption edges on both sides as a coefficient_jNi primary linear equations with x as a variable are generated as Ni linear simultaneous equations, and the simultaneous equations are solved to obtain the areal density of each element (S6).
[0033]
In the example of FIG. 4, since three elements O, N, and C have been identified, the following three-dimensional linear simultaneous equation is obtained.
O absorption edge both sides:
A_o(Dif) = (μ₁ ^O−μ₂ ^O) Ρ_Ox + (μ₁ ^N−μ₂ ^N) Ρ_Nx + (μ₁ ^C−μ₂ ^C) Ρ_Cx
N absorption edge both sides:
A_N(Dif) = (μ₃ ^O−μ₄ ^O) Ρ_Ox + (μ₃ ^N−μ₄ ^N) Ρ_Nx + (μ₃ ^C−μ₄ ^C) Ρ_Cx
Both sides of C absorption end:
A_o(Dif) = (μ₅ ^O−μ₆ ^O) Ρ_Ox + (μ₅ ^N−μ₆ ^N) Ρ_Nx + (μ₅ ^C−μ₆ ^C) Ρ_Cx
The ternary simultaneous equation can be solved relatively easily, and the areal density of each element is obtained as a first approximate value.
[0034]
Next, an X-ray absorption spectrum that should be exhibited when these identified elements have the areal density determined as the i-th approximate value is calculated, and is set as the i-th absorption spectrum (S7).
A difference spectrum is generated by subtracting the i-th absorption spectrum from the zero-order absorption spectrum obtained in the experiment (S8).
FIG. 5 shows a difference spectrum generated by subtracting the first-order absorption spectrum from the zero-order absorption spectrum in the example of FIG. The scale of the vertical axis is magnified 10 times.
[0035]
The existence ratio of the absorption edge structure is determined from the pattern of the difference spectrum (S3). Since the shape of the absorption edge is remarkable, it can be determined mechanically by pattern recognition. The difference spectrum may be displayed on a monitor, and the operator may observe and determine the difference spectrum.
FIG. 5 clearly shows the absorption edge structure of calcium, and can be easily identified.
[0036]
When there is an element that can be newly identified, data of each element is acquired for the wavelengths on both sides of the absorption edge of the newly identified element, and the steps from S4 to S8 are performed in the same manner as above, and the identification has been performed so far. A simultaneous equation composed of Ni elemental equations for all elements of Ni is set up and solved, an i-th approximate value of the areal density of each element is obtained, and finally the process returns to S3.
[0037]
In the example of FIG. 4, since the presence of calcium has been clarified from the difference spectrum of FIG. 5, the following quaternary linear simultaneous equation is established based on the 0th-order absorption spectrum. O absorption edge both sides:
A_o(Dif) = (μ₁ ^O−μ₂ ^O) Ρ_Ox + (μ₁ ^N−μ₂ ^N) Ρ_Nx + (μ₁ ^C−μ₂ ^C) Ρ_Cx + (μ₁ ^Ca−μ₂ ^Ca) Ρ_Cax
N absorption edge both sides:
A_N(Dif) = (μ₃ ^O−μ₄ ^O) Ρ_Ox + (μ₃ ^N−μ₄ ^N) Ρ_Nx + (μ₃ ^C−μ₄ ^C) Ρ_Cx + (μ₃ ^Ca−μ₄ ^Ca) Ρ_Cax
Both sides of C absorption end:
A_o(Dif) = (μ₅ ^O−μ₆ ^O) Ρ_Ox + (μ₅ ^N−μ₆ ^N) Ρ_Nx + (μ₅ ^C−μ₆ ^C) Ρ_Cx + (μ₅ ^Ca−μ₆ ^Ca) Ρ_Cax
Ca absorption edge both sides:
A_Ca(Dif) = (μ₇ ^O−μ₈ ^O) Ρ_Ox + (μ₇ ^N−μ₈ ^N) Ρ_Nx + (μ₇ ^C−μ₈ ^C) Ρ_Cx + (μ₇ ^Ca−μ₈ ^Ca) Ρ_Cax
By solving this quaternary simultaneous equation, a second approximate value of the areal density is obtained for the four elements.
[0038]
Further, since the last absorption edge structure of iron is found from the difference spectrum obtained by subtracting the secondary absorption spectrum obtained using the second approximation from the zeroth absorption spectrum, the iron absorption edge structure is obtained based on the zeroth absorption spectrum. A five-element linear simultaneous equation is generated and solved for the five elements, and a third approximate value of the areal density is calculated for the five elements.
This procedure is repeated until no absorption edge is observed in the difference spectrum.
[0039]
When the absorption edge structure cannot be observed in the difference spectrum, it is determined that no remarkable element is contained other than the already identified element, and the i-th approximate value obtained last is used as the measured value of each area density ( S9).
Since the areal density obtained by this method corresponds to the amount of the element, the relative weight ratio of each element can be known. If the thickness of the sample can be obtained by another method, the density can be obtained by dividing the surface density by the thickness.
By using the method of this embodiment, the elements contained in the unknown sample can be accurately detected by solving a multiple simultaneous equation having a minimum number of terms, and the element amount can be obtained as the areal density. Therefore, the relative weight ratio of each element contained in the sample can be known.
[0040]
Since this method uses a photoelectric conversion type X-ray microscope apparatus that generates an X-ray absorption image with a high magnification, it is possible to accurately specify a sample portion and perform component analysis. Further, by selecting and analyzing an arbitrary position in the X-ray absorption image, the two-dimensional distribution of elements contained in the unknown sample can be clarified.
Since the photoelectric conversion type X-ray microscope can also handle a biological sample, a relatively light element can be quantified particularly by specifying a target portion of the biological sample. The technique of the present invention is particularly useful because there is no other suitable technique for detecting trace light elements.
[0041]
Further, according to the method of the present embodiment, once the X-ray image is generated, the part to be analyzed can be arbitrarily specified again and again to obtain a result.
In the above description, in order to explain the technical concept in an easy-to-understand manner, the absorption spectrum is synthesized based on the data read from the image memory. However, in an actual configuration, only the data necessary for each operation is extracted. Needless to say, it is not necessary to treat it as a continuous spectrum.
[0042]
【The invention's effect】
As described above, the composition distribution of a sample, particularly a biological sample composed of a low atomic weight element, even when an unknown element is contained, by the X-ray spectroscopic microscopic analysis method and the photoelectric conversion type X-ray microscope apparatus of the present invention. Can be calculated efficiently and accurately.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram showing an X-ray microscope device used in one embodiment of the present invention.
FIG. 2 is a table listing absorption edges and wavelengths used for analysis of main elements constituting the living body.
FIG. 3 is a flowchart showing an analysis calculation process in the embodiment.
FIG. 4 is a simplified absorption spectrum diagram of a model substance.
FIG. 5 is a diagram illustrating an example of a difference spectrum used in the present embodiment.
[Explanation of symbols]
1 X-ray generator
2 Photoelectric conversion surface
3 Electronic image magnifier
4 Image detector
5 Arithmetic processing unit

Claims (5)

In a photoelectric conversion type X-ray microscope apparatus, a sample is irradiated with X-rays by sweeping the wavelength, X-ray absorption images are acquired and stored for each wavelength, and the obtained X-ray absorption images are absorbed at a predetermined position on the sample. The spectra are synthesized, and the presence or absence of the absorption edge structure of the element is detected based on the synthesized absorption spectrum, and the difference between the absorptances at the wavelengths on both sides of the absorption edge structure of the detected absorption edge structure of each element is defined as the left side. The surface density of the element is a variable on the right-hand side, and a difference equation between the mass absorption coefficients at each wavelength is set as a coefficient of each variable on the right-hand side. Is calculated, the contribution of the absorption spectrum of each element is calculated using the approximate surface density, and the remaining absorption spectrum is subtracted from the combined absorption spectrum to form a residual spectrum. Inspect the presence or absence of the absorption edge structure of any element, and if a new element can be detected, establish the same simultaneous multiple-element equation for all elements detected so far and solve this to solve the surface of each element. An X-ray spectroscopic microanalysis method, wherein an approximate value of density is calculated, and when a new element cannot be detected, the approximate surface density value is used as the areal density of each element at the predetermined position. 2. The X-ray spectroscopic microscopic analysis method according to claim 1, wherein said absorption spectrum comprises data at a wavelength position required for calculation. 3. The X-ray spectroscopic microanalysis method according to claim 1, wherein X-ray absorption image data at wavelengths around an absorption edge of an element which may be contained in the sample is selected and stored. What is claimed is: 1. A photoelectric conversion type X-ray microscope device comprising an X-ray generator, a photoelectric conversion surface, an electronic image magnifying device, an image detection unit, and an arithmetic processing device, wherein a sample is placed in close contact with the photoelectric conversion surface, and When X-rays generated by the X-ray generator are swept from behind and irradiated, the transmitted X-rays form an electron image on the photoelectric conversion surface, and the electron image magnifying device emits electrons emitted from the electron image. The image processing unit is provided with an image memory, acquires an image signal of an X-ray absorption image from the image detection unit, and stores the image signal in the image memory for each sweep wavelength. Then, when a predetermined position in the X-ray image is designated, an image signal corresponding to the position in the image is taken out from the image memory for a necessary wavelength in the sweep wavelength, and the measurement X of the designated portion is measured. Line absorption spectrum Then, the presence or absence of an absorption edge structure of the element was detected based on the measured X-ray absorption spectrum, and the difference between the absorptance at the wavelength on both sides of the absorption edge of the detected absorption edge structure of each element was determined as the left side. The surface density of each element is a variable on the right side, and the difference of the mass absorption coefficient at each wavelength is set as a coefficient of each variable on the right side. Determine the value, calculate the contribution of the absorption spectrum of each element using the approximate surface density value, subtract from the measured absorption spectrum to form a residual spectrum, and further determine the absorption edge structure of a new element from the residual spectrum. If a new element can be detected, the same multidimensional simultaneous equation as described above is established for all the elements detected so far, and this is solved to determine the near surface density of each element. Calculating a value, when a new element is not detected, the photoelectric conversion type X-ray microscope apparatus characterized by having the surface density approximation and surface density of each element in the predetermined position. 5. The photoelectric conversion type X-ray microscope apparatus according to claim 4, wherein said image memory selects and stores X-ray absorption image data at wavelengths around an absorption edge of an element which may be contained in said sample.

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