JPS6147536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an apparatus for reconstructing an X-ray tomographic image, and in particular to an apparatus for reconstructing an X-ray tomographic image by performing desired arithmetic processing.
The present invention relates to a device capable of reconstructing line tomographic images. In general, in the industrial and medical world, X-ray inspections are widely used to determine the internal structure of products and the human body.
Linear computerized tomography equipment (abbreviated as "CT") is being actively developed. By the way, in this type of conventional X-ray computerized tomography apparatus, first, as shown by the solid line in FIG. The X-ray projection distribution is measured by the X-ray detector c, and then, as shown by the chain line in FIG. 1, the X-ray generator a and the X-ray detector c are rotated by a predetermined angle α (for example, 1°). By irradiating the X-ray beam toward the X-ray inspection object b again from this position, the angle α is
After measuring the X-ray projection distribution when the distribution is moved by Computation processing is performed using the method, and then a tomographic image of the X-ray object b is reconstructed based on the processing results. However, such a conventional X-ray computer tomography apparatus requires a large number of X-ray projection distributions in order to reconstruct a tomographic image of the subject b, which causes the following problems. (1) Since it takes a long time to collect data (several seconds to several minutes), for moving object b,
The tomographic image cannot be reconstructed. (2) Since the amount of X-ray exposure increases, if the subject b is a living body such as a human body, there is a risk of adverse effects on the living body. The present invention aims to solve these problems, and obtains highly accurate reconstructed images by simply using a single X-ray projection distribution as data for reconstructing tomographic images of the examined object. An object of the present invention is to provide a single X-ray projection type tomographic image reconstruction device that can perform the following functions. For this reason, the single X-ray projection type tomographic image reconstruction apparatus of the present invention uses a virtual tomographic plane S that includes the tomographic plane of the X-ray subject B and has m pixels vertically and n pixels horizontally. and , from one end to the other end of a single X-ray projection distribution D obtained by irradiating the plurality of unit X-ray beams from the X-ray generator A toward the X-ray inspection object B. N (=m×n) X-ray densities
It is equipped with an X-ray concentration measuring device E that measures _d1 to _dno and further measures at least m-1 X-ray densities dno ₊₁ to _dno+n-1 near the other end. M (=mn+m-1) obtained with concentration measuring device E
The relationship is determined from the X-ray concentration vector _D , the coefficient matrix L, and the residual vector r consisting of non-negative elements, with the X-ray absorption coefficient vector μ being an unknown quantity after receiving information on the X _- ray concentrations d1 to dno+n-1. Formula Lμ≦r+D, Lμ≧
From −r+D, the X-ray absorption coefficient μ ₁ of each pixel above
A projective transformation device F having an arithmetic device for calculating μ _no is provided, and the N
The above X-ray absorption coefficient μ is applied to the position of each pixel 1 to mn
a reconstruction device H that reconstructs a tomographic image of the X-ray subject B by applying ₁ to μ _no ;
A single X-ray projection type tomographic image reconstruction apparatus, characterized in that a display device J is provided for displaying a tomographic image of the X-ray subject B based on the output from the X-ray projection type tomographic image reconstruction apparatus. however, = (μ ₁ , μ ₂ , μ ₃ , ..., μ _no ) ^T = (d ₁ , d ₂ , d ₃ , ..., d _no+n-1 ) ^T = (mn + m-1) × Band matrix of mn = (r ₁ , r ₂ , r ₃ , ..., r _{no + n-1} ) ^T α: Length of the above X-ray beam passing through the pixel Below, embodiments of the present invention will be explained with reference to the drawings. To explain, FIGS. 2 to 4 show a single X-ray projection type tomographic image reconstruction apparatus as the first embodiment, and FIG. 2 is a schematic diagram showing the means for measuring the X-ray projection distribution. FIG. 3 is a system configuration diagram, and FIG. 4 is a schematic diagram for explaining its operation. As shown in FIG. 3 (a diagram corresponding to the claims), an X-ray inspected object B is positioned between an X-ray generator A and an X-ray detector C. This X-ray inspection object B can be irradiated with X-rays from a predetermined direction, and as a result, the X-rays that have passed through the X-ray inspection object B form a single X-ray projection distribution D (Fig. 4). ). As shown in FIG. 4, this X-ray generating device A has a virtual tomographic plane S having m pixels vertically and n pixels horizontally (this plane S is the tomographic plane of the X-ray subject B). ), a plurality of unit X-ray beams are irradiated toward the X-ray inspection object B from a predetermined direction θ so that the unit X-ray beam passes at least one lower left corner of each pixel 1 to mn. in,
It is designed to generate X-rays with radiation quality (penetrating power) and dose that are suitable for the X-ray inspection object B, which is the object of the inspection, and the wavelength of the generated X-rays is proportional to the applied voltage. Also, the quality of X-rays is determined by their wavelength. The applied voltage varies depending on the application, ranging from 50,000 volts to 120,000 volts when used for medical diagnosis, and from 100,000 volts to 300,000 volts when used for non-destructive testing. Ru. X-ray inspection object B refers to an object that is irradiated with X-rays and whose transmitted dose distribution (X-ray projection distribution) is measured to reconstruct an image in a desired tomographic plane. For example, in the case of medical diagnosis, it is a human body (generally a living body), and in the case of non-destructive testing, it is a so-called industrial product. Further, as the X-ray detector C, an X-ray film, a scintillation detector, a semiconductor detector, a xenon gas detector, or the like is used. By the way, the single X-ray projection distribution data D obtained by the X-ray detector C is measured by an X-ray projection distribution measuring means (X
The above X-ray projection distribution D is measured by the line density measuring device) E.
Equal intervals w from one end to the other
mn (=N) X-ray density values d ₁ to _{d no}
is measured, and further m-1 X-ray density values d near the other end with an equal interval w are measured.
_no+1 to d _no+n-1 are measured, total mn+m-1 (=
Each value d _k at M) positions k is measured (see FIG. 4). When the X-ray detector C is an X-ray film, the X-ray projection distribution measuring means E may be used to measure a plurality of X-ray density distributions (so-called X-ray photographs) obtained as shading of the degree of blackening on the film. A microdensitometer is used that can measure the value of . In this way, from one end of the X-ray projection distribution D to the other end, there are multiple positions k spaced at equal intervals w.
In addition to the above-mentioned example, as a means for measuring each value d _k in In the case of a scintillation detector, one scintillation detector may be combined with a mechanism that can move it from one end of the X-ray projection distribution D to the other, or a number of scintillation detectors may be The arrangement may be performed over the entire width of the line projection distribution D. In addition, if the X-ray detector C is a semiconductor detector that also receives X-rays transmitted through the X-ray inspection object B and outputs a signal corresponding to the X-ray concentration, the above-mentioned scintillation detection can be used as the above-mentioned means. As in the case of detectors, one semiconductor detector and a mechanism for moving it may be combined, or a large number of semiconductor detectors may be arranged. Furthermore, when the X-ray detector C is a xenon gas detector, the above means includes one xenon gas detector and a mechanism for moving it, as in the case of the scintillation detector or semiconductor detector described above. Combinations and the arrangement of multiple xenon gas detectors may be used. The signals obtained in this way by the microdensitometer, scintillation detector, and semiconductor detector are analog signals, so in order to input them to a digital computer, this signal is converted to an analog-to-digital converter E' ( Below, “A/D
called a converter. ) is converted into a digital signal and then stored on a disk or the like. Next, data output d from this A/D converter
_k (digital signal) is input to the projective transformation device F. This projective transformation device F uses M (=mn+m−1) X-ray densities _d1 to d1 obtained by the X-ray density measuring device E.
After receiving the information of d _no+n-1 and using the X-ray absorption coefficient vector μ as an unknown quantity, the relational expression Lμ≦r+D, Lμ≧− is determined from the X-ray concentration vector D, the coefficient matrix L, and the residual vector r consisting of non-negative elements. It has an arithmetic device that calculates the X-ray absorption coefficients μ ₁ to μ _no of each pixel from r+D, and a specific example thereof is a digital computer with a built-in desired program. Here, from M values d _k (one-dimensional data) on a single X-ray projection distribution D, N values are calculated as constituent elements of a virtual tomographic plane S including the tomographic plane of the X-ray subject B. A method for determining each X-ray absorption coefficient μ _t (two-dimensional data) of each pixel will be explained. First, a virtual tomographic plane S as a tomographic image reproduction surface of the X-ray subject B is considered to consist of mn (=N) pixels divided into small sections, as shown in FIG. 4, and the center of the plane S is Take it as the origin of the x-y coordinates. Note that it is assumed that each pixel has the same X-ray absorption coefficient, and for convenience of explanation, m and n are assumed to be even numbers, and the size of one pixel is assumed to be a square of △×△. In addition, the X-ray beam passing through this virtual plane S shall be irradiated in parallel from the direction θ that satisfies θ = tan ^-1 m, and the beam diameter of each unit X-ray beam shall be sufficiently small compared to each pixel. do. Now, number each pixel according to the order shown in Figure 4, express it by its absorption coefficient μ _t , and calculate the unit X that is irradiated from the θ direction and passes through the x-y coordinate point (x _j , y _i ). If the projected density obtained by the line beam is _dk , then the following equation is obtained. Here, x _j = (-n/2+j-1)・△, y _i = (m/2-i)・△, t=(j-1)・m+i (i=1, 2,..., m ;j=1,2,...,
n) k=(j-1)・m+i, where=k≠mn+m (i=1,2,...,m; j=1,2,...,n
+1), where i represents a row and j represents a column. 〓〓＝〓 ……(1) However Note that = (μ ₁ , μ ₂ , μ ₃ ..., μ _no ) ^T = (d ₁ , d ₂ , d ₃ ..., d _{no + n-1} ) ^T L is (mn + m-1) × mn is the band matrix of Also, α is the length of the X-ray beam that passes through the pixel,
a=△√1+ ² , and the symbol ^T represents transposition. By the way, in equation (1), X as an unknown quantity
Since the number M of equations is greater than the number N of linear absorption coefficients μ _t , we need to find the most probable value of this unknown quantity, the X-ray absorption coefficient μ _t.In order to achieve this, , there is a method called the least squares method. Therefore, applying the least squares method to equation (1), we get
That is, by multiplying the transposed matrix of L from the left side of both sides of equation (1), the following equation is obtained. ^{T _} Tomographic two-dimensional data μ _t of line inspection object B
can be calculated. Note that the residual vector (correction value vector) r[=(r ₁ , r ₂ , r ₃ , ..., r
_M ) ^T ] and generalize it, formula (1) becomes as follows.

[Table] One method for calculating the X-ray absorption coefficient vector μ from equation (1)′ is the least squares method _. When we find the most probable value, the solution is the same as that obtained by equation (3). However, in the actual X-ray inspection object B, it is difficult to assume that μ _t is constant;
Generally, measurement errors are also included. Therefore, even if the above assumptions are slightly violated or a small amount of measurement error is introduced, the 2
It is difficult to expect that dimensional data μ _t will give good results. Therefore, using mathematical programming as another method for determining the X-ray absorption coefficient μ _t from Lμ≦r+D and Lμ≦−rD, the non-negative correction value (residual) value r ₁ ,
Introduce r ₂ , r ₃ , ..., r _M. Furthermore, since the absorption coefficient of an X-ray beam transmitted through an object is generally non-negative and does not exceed a certain positive upper limit U, equation (1) can be expressed as follows by adding these constraints.

[Table] Furthermore, non-negative slack variables s ₁ , s ₂ , s ₃ ,...
..., s _3M , the simultaneous linear inequalities in equation (4) become the simultaneous linear equations in the following equation.

[Table] Objective function based on the constraint condition equation (5) above. Using mathematical programming, we find a solution that minimizes
After a finite number of calculations, the optimal 2
Dimensional data μ _t is calculated. In the above example, the two-dimensional data μ _t was calculated based on the objective function that minimizes the sum of the absolute values of the correction values in the constraint equation, but on the other hand, the following constraint equation (7) is also calculated. There is also a method of minimizing the objective function in equation (8).

[Table] By solving the above equation, the tomographic two-dimensional data μ _t of the X-ray subject B can be calculated under the condition that the maximum correction value of the absolute value in the constraint condition equation is the minimum. Furthermore, the objective function is It is also possible to carry out the method by minimizing the objective function F=r ² . . . (10) under the constraint expression (7). As described above, M represents mn+m-1 and N represents mn. According to the mathematical programming method described above, as is clear from what has already been stated, the following relational expression holds true, but
In this relational expression, the sum of squares of the non-negative elements r ₁ to r _M of the residual vector (correction value vector) r r _k ² [Formula
(9)] or the sum of absolute values r _k [see equation (6)], an optimal solution for the X-ray absorption coefficients μ ₁ to _{μ no} is found. Here, the relational expression is from equation (4),

【table】 i.e.

[Table] becomes. And, 〓=(μ ₁ , μ ₂ , ..., μ _no ) ^T 〓=(r ₁ , r ₂ , ..., r _M ) ^T 〓=(p ₁ , p ₂ , ..., p _M ) ^T =〓/α〓=(d ₁ , d ₂ , ..., d _M ) ^T Further, L is an M×N band matrix. The two-dimensional data μ _t obtained in this way is
It is transferred to the three-dimensional internal structure storage device G. This three-dimensional internal structure storage device G stores in time series the two-dimensional data μ _t for tomographic image construction transferred from the projective transformation device F, and also stores the three-dimensional internal structure data of the X-ray inspected object B. The memory for calculating By the way, the two-dimensional data μ _t initially sent from the projective transformation device F is about a certain cross section of the X-ray inspection object B, but it can be changed by changing the measurement location with the X-ray projection distribution measuring means E. Then, another X-ray projection distribution D' is obtained, and from this, two-dimensional data μ' _t for other cross sections can be easily obtained, so two-dimensional data μ _t for several different cross sections,
By integrating μ′ _t , μ″ _t , ..., it becomes possible to memorize the three-dimensional internal structure of the X-ray inspection object B, but in order to construct a complete three-dimensional internal structure, Since it is necessary to perform interpolation between each cross-sectional data, this memory G is used as a memory device that has a calculation function for this purpose. H is connected, and this arbitrary tomographic image construction device H calculates a specified arbitrary cross section of the X-ray inspected object B from the three-dimensional internal structure data of the X-ray inspected object B stored in the memory G. This is an apparatus that constructs a tomographic image by selectively extracting two-dimensional data of the X-ray object B. The arbitrary tomogram here refers to a cross section of the X-ray subject B in a horizontal, vertical, or diagonal direction. In this way, the two-dimensional data of an arbitrary tomographic image obtained by this arbitrary tomographic image constructing device H is consistently mathematically calculated based on the X-ray projection distribution obtained by the X-ray projection distribution measuring means E. Since the calculations have been made without contradiction, this is an appropriate digital-to-analog converter F' (hereinafter referred to as "D/A converter").
If the tomographic image is sent to an arbitrary tomographic image display device J for display via the Therefore, there is no guarantee that a suitable image will be obtained. Therefore, in order to correct the data from this optional tomographic image construction device H, this data is sent to the optional tomographic image quality improvement device I. This arbitrary tomographic image quality improvement device I improves the image quality by removing noise, smoothing, and emphasizing the sharpness of arbitrary tomographic image data sent from the arbitrary tomographic image construction device H. , a digital filter is used to remove noise,
A smoothing circuit is used for smoothing, and a differentiation circuit is used for emphasizing sharpness. The signal whose image quality has been improved in this way is D/A
It is sent to the arbitrary tomographic image display device J via the converter F'. This arbitrary tomographic image display device J receives a signal sent from the arbitrary tomographic image quality improvement device I and displays an arbitrary tomographic image of the X-ray subject B on a color or black and white cathode ray tube (braun tube) monitor. A device that displays images, and as mentioned above, cathode ray tubes are generally used. With the above configuration, in order to reconstruct a tomographic image of the X-ray subject B, first the X-ray generator A irradiates the X-ray subject B with X-rays from a predetermined direction, and then the X-ray detector C Single X-ray projection distribution D obtained with
, using the X-ray projection distribution measuring means E, calculate each value d _k at M positions k spaced at equal mutual intervals w from one end of the X-ray projection distribution D to the other end of the X-ray projection distribution D. By measuring until 1
Dimensional data d _k is obtained. Next, these one-dimensional data d _k are suitably analog-digital converted, and then each X-ray of N (<M) pixels on the virtual tomographic plane S is Absorption coefficient μ _t
(two-dimensional data) is required. After that, this two-dimensional data μ _t is stored in the memory G,
Via the arbitrary tomographic image construction device H, the arbitrary tomographic image quality improvement device I, and the D/A converter F', it is reconstructed and displayed as a tomographic image of the X-ray subject B on the arbitrary tomographic image display device J. It is. FIG. 5 is a schematic diagram for explaining the operation of a single X-ray projection type tomographic image reconstruction apparatus as a second embodiment of the present invention. In the case of this second embodiment, the X-ray generator A and
When the object B to be inspected is close to the X-ray beam, that is, when the X-ray beam is a Fan beam, in this case, the tomographic two-dimensional data μ _t is composed of pixels with modified polar coordinates as shown in Fig. 5. Then, formula (1) is obtained and the above theory can be applied as is. In FIG. 5, the X-ray source is the origin 0, the inner radius of the polar coordinate pixel is _R1 , the outer radius is _R0 , and the pixels are composed of m×n. The pixels are numbered as shown in FIG. 5, and the straight line passing through 00' is used as the standard for angle. The radii R ₁ , R ₂ and angles ₁ , ₂ , ₃ , and ₄ are expressed as follows.

[Table] Now, let us draw a straight line passing through points R ₁ , ₁ and R ₂ , ₃ .
If L ₂ is a straight line passing through L 1 , points R ₁ , ₂ and R ₂ , ₄ , pixel t has an area _surrounded by radii R ₁ , R ₂ and two straight lines L ₁ , L ₂ . However, t=i+(j-1)·m, θ' is the apex angle far inside (radius R ₁ ) of the polar coordinate pixel. In this way, even when the X-ray beam is a Fan beam, the two-dimensional data μ _t can be obtained from the one-dimensional data d _k in the same way as in the case of a parallel beam as in the first embodiment, and thereby a single The tomographic image of the X-ray subject B can be reconstructed from the X-ray projection distribution D. Note that k=(j-1)・m+i, k≠m(n+
1) (i = 1, 2, ..., m; j = 1, 2, ...
..., n+1). As detailed above, according to the single X-ray projection type tomographic image reconstruction apparatus of the present invention, it is possible to reconstruct a tomographic image of the X-ray subject B from a single X-ray projection distribution D. Therefore, the following effects or advantages can be obtained. (1) Since the data acquisition time is very short (30 milliseconds or less), it is possible to clearly reconstruct a tomographic image of a moving X-ray object B (for example, a heart). (2) Since the amount of X-ray exposure is very small (several tenths to several hundredths of that of conventional means), there will be no adverse effects even if the X-ray subject B is a living body. (3) Since the X-ray tomographic image is reconstructed based on M measurement values, which is larger than the number N of pixels t constituting the tomographic plane S including the X-ray subject B, the reconstruction The accuracy of configuration can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram for explaining a conventional X-ray tomographic image reconstruction means, and FIGS. 2 to 4 are a single X-ray projection type tomographic image reconstruction apparatus as a first embodiment of the present invention. Fig. 2 is a schematic diagram showing the means for measuring the X-ray projection distribution, Fig. 3 is a system configuration diagram, Fig. 4 is a schematic diagram for explaining its operation, and Fig. 5 is a schematic diagram showing the means for measuring the X-ray projection distribution. FIG. 2 is a schematic diagram for explaining the operation of a single X-ray projection type tomographic image reconstruction apparatus as a second embodiment of the present invention. A...X-ray generator, B...X-ray inspected object, C
...X-ray detector, D...X-ray projection distribution, E...X
Line projection distribution measuring means (X-ray density measuring device), E'...
...A/D converter, F...Projective conversion device, F'...
D/A converter, G... Three-dimensional internal structure storage device as memory, H... Arbitrary tomographic image construction device (reconstruction device), I... Arbitrary tomographic image quality improvement device, J...
...Arbitrary tomographic image display device, S...Virtual tomographic plane.

Claims (1)

[Claims] 1. Regarding a virtual tomographic plane S that includes the tomographic plane of the X-ray inspected object B and has m pixels vertically and n pixels horizontally, the unit X-ray beam is located at the corner of each pixel 1 to mn. The above X should pass through at least one part of the
A plurality of units X from a predetermined direction toward the object B to be inspected
An X-ray generator A that irradiates a ray beam, and a single X-ray obtained by irradiating the plurality of unit X-ray beams from the X-ray generator A toward the X-ray inspection object B. N (=m×n) X-ray densities d ₁ to d from one end to the other end of the projection distribution D
The X-ray concentration measuring device E is equipped with an X-ray concentration measuring device E for measuring _no and further measuring at least m-1 X-ray concentrations d _no+1 to d _no+n-1 near the other end. M (=mn+m-1) X obtained by
In response to the information on the linear densities _d1 to _dno+n-1, the X-ray absorption coefficient vector μ is an unknown quantity, and the relational expression Lμ≦ is determined from the X-ray concentration vector D, the coefficient matrix L, and the residual vector r consisting of non-negative elements. r+D, Lμ≧−r+
A projective transformation device F having an arithmetic device for calculating the X-ray absorption coefficients μ ₁ to μ _no of each pixel is provided from D, and the virtual tomographic plane S is constructed by receiving signals from the projection transformation device F. The above-mentioned X-ray absorption coefficient μ ₁ -μ _n is set at the position of each of the above-mentioned N pixels 1-mn.
a reconstruction device H that reconstructs a tomographic image of the X-ray subject B by applying _o ; and a display device that displays the tomographic image of the X-ray subject B based on the output from the reconstruction device H. 1. A single X-ray projection type tomographic image reconstruction device, characterized in that it is provided with: J. however, = (μ ₁ , μ ₂ , μ ₃ , ..., μ _no ) ^T = (d ₁ , d ₂ , d ₃ , ..., μ _no+n-1 ) ^T = (mn+m-1)× Band matrix of mn = (r ₁ , r ₂ , r ₃ , ..., r _{no + n-1} ) ^T α: Length of the X-ray beam passing through the pixel 2 The X-ray density measuring device E is A microdensitometer that can measure multiple X-ray concentration values on an X-ray concentration distribution obtained on an X-ray film, and an analog signal that can convert an analog signal from this microdensitometer into a digital signal. A single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising a digital converter. 3. The X-ray concentration measuring device E includes a scintillation detector with a moving mechanism that receives X-rays passing through the X-ray inspection object B and outputs a signal corresponding to the X-ray concentration, and scintillation detection of the same. 2. The single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising an analog-to-digital converter capable of converting an analog signal from a device into a digital signal. 4 The X-ray concentration measuring device E includes a number of scintillation detectors that receive X-rays transmitted through the X-ray inspection object B and output signals corresponding to the X-ray concentration, and these scintillation detectors. 2. The single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising an analog-to-digital converter capable of converting an analog signal from a device into a digital signal. 5 The X-ray concentration measuring device E includes a semiconductor detector with a moving mechanism that receives X-rays passing through the X-ray inspection object B and outputs a signal corresponding to the X-ray concentration, and a semiconductor detector from the semiconductor detector. 2. A single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising an analog-to-digital converter capable of converting an analog signal into a digital signal. 6 The X-ray concentration measuring device E includes a large number of semiconductor detectors that receive X-rays transmitted through the X-ray inspection object B and outputs signals corresponding to the X-ray concentration, and from these semiconductor detectors. 2. A single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising an analog-to-digital converter capable of converting an analog signal into a digital signal. 7 The X-ray concentration measuring device E includes a xenon gas detector with a moving mechanism that receives X-rays passing through the X-ray inspection object B and outputs a signal corresponding to the X-ray concentration, and a xenon gas detector. Claim 1 comprising an analog-to-digital converter capable of converting an analog signal from a device into a digital signal.
The single X-ray projection type tomographic image reconstruction device described in 2. 8 The X-ray concentration measuring device E includes a large number of xenon gas detectors that receive X-rays passing through the X-ray inspection object B and output signals corresponding to the X-ray concentration, and these xenon gas detectors. 2. The single X-ray projection type tomographic image reconstruction apparatus according to claim 1, comprising an analog-to-digital converter capable of converting an analog signal from a device into a digital signal. 9. Claims 1 to 8, wherein the projective transformation device F includes a digital computer that calculates and outputs a digital signal corresponding to the X-ray absorption coefficient of each pixel based on the data output. The single X-ray projection type tomographic image reconstruction device according to any one of the items. 10 The projective transformation is carried out between the projective transformation device F and the reconstruction device H in order to store a plurality of tomographic image information of the X-ray inspected object B and display any tomographic image on the display device J. A single X-ray projection type tomographic image reconstruction device according to any one of claims 1 to 9, wherein a memory capable of storing signals from the device F is interposed. 11 Claims 1 to 10, wherein a digital filter is interposed between the reconstruction device H and the display device J in order to improve the quality of the image displayed on the display device J. The single X-ray projection type tomographic image reconstruction device according to any one of the above. 12 Claims 1 to 10, wherein a smoothing circuit is interposed between the reconstruction device H and the display device J in order to improve the quality of the image displayed on the display device J. The single X-ray projection type tomographic image reconstruction device according to any one of the items. 13 Claims 1 to 10, wherein a differentiation circuit is interposed between the reconstruction device H and the display device J in order to improve the quality of the image displayed on the display device J. The single X-ray projection type tomographic image reconstruction device according to any one of the above.