JP7748718B2 - Experimental teaching materials, sequence generation method, and method of using the experimental teaching materials - Google Patents

Description

The present invention relates to experimental teaching materials, array generation methods, and methods for using experimental teaching materials.

A computed tomography (CT) scanning device positions an X-ray source and detector facing each other across the subject and detects the intensity of X-rays passing through the subject. The transmission intensity of X-rays represents the amount of absorption, which is the integrated information of the subject through which the X-rays have passed. For this reason, measurements taken from a single direction cannot obtain an image of the subject from the transmission intensity of X-rays. Therefore, CT scanning devices measure the transmission intensity of X-rays while changing the direction of the X-ray source and detector relative to the subject, and perform image reconstruction based on the transmission intensity of X-rays from different directions to generate an image of the subject's inside the body. This is the principle of image reconstruction in CT scanning devices.

The principles of image reconstruction in CT scan devices such as those described above are difficult for students, especially those without a physics background, to understand. Therefore, in order to understand the principles of image reconstruction, student experiments are being conducted using a radiation source and a GM tube (see Non-Patent Document 1).

Hideo Nitta, Physics Education 52-4 (2004) 311-314 Tokyo Shoseki "Revised Physics", 2020 edition, reviewed in 2017, pp. 458-459

However, the experiments disclosed in the above-mentioned non-patent documents 1 and 2 use sealed radiation sources, which are not suitable for students to use casually. There is a need for experimental teaching materials that allow students to learn the principles of image reconstruction using CT scanning devices in a safer and easier-to-understand manner.

The present invention was made in light of the above-mentioned circumstances, and aims to provide experimental teaching materials, array generation methods, and methods for using the experimental teaching materials that enable students to learn the principles of image reconstruction using a computed tomography device in a safer and easier-to-understand manner.

In order to achieve the above object, the experimental teaching material according to a first aspect of the present invention comprises:
An experimental teaching material for learning the principles of image reconstruction using a computed tomography apparatus,
a block matrix configured by arranging an equal number of blocks formed of a material that transmits light rays having wavelengths longer than the radiation in a plurality of axial directions perpendicular to each other, and causing the light rays incident in the axial directions to travel straight in the axial directions;
a light source that directs the light beam into the block matrix along the axis;
a detection unit that detects the intensity of the light beam that has passed through the block matrix;
a cover that shields the blocks that constitute the block matrix so that they cannot be seen from the outside,
The blocks include a first block and a second block having different attenuation degrees of the transmitted light beam,
The block matrix allows the first blocks and the second blocks to be freely arranged.

a filter for attenuating the transmitted light beam is inserted into the second block;
This may also be the case.

The second block is filled with a liquid that attenuates the light beam passing through it.
This may also be the case.

The light is any one of infrared light, visible light, and ultraviolet light.
This may also be the case.

The block matrix is capable of adjusting the number of blocks in the axial direction.
This may also be the case.

A sequence generation method according to a second aspect of the present invention comprises:
1. An array generation method for generating, by an information processing device, array information of first blocks and second blocks in a two-dimensional square matrix formed by an array of first blocks and second blocks, each having a different transmission intensity for a light beam having a wavelength larger than a radiation beam, the method comprising:
an input step of inputting information indicating N, which is the number of rows and columns of the two-dimensional square matrix, and information indicating M, (M≦N ² ), which is the number of second blocks in the two-dimensional square matrix;
a matrix generation step of generating the two-dimensional square matrix by packing the second blocks into one of four corner areas of the two-dimensional square matrix based on the information input in the input step;
a matrix transformation step of moving an entire block of any row in the two-dimensional square matrix generated in the matrix generation step to a different row, or exchanging it with an entire block of any other row, or moving an entire block of any column in the two-dimensional square matrix to a different column, or exchanging it with an entire block of any other column;
Includes.

A method of using the experiment teaching material according to the third aspect of the present invention comprises:
a block matrix configured by arranging an equal number of blocks formed of a material that transmits light rays having wavelengths larger than that of radiation in a plurality of axial directions perpendicular to each other, the block matrix causing the light rays incident in the axial directions to travel straight in the axial directions; a light source that makes the light rays incident on the block matrix along the axial directions; a detection unit that detects the intensity of the light rays that have transmitted through the block matrix; and a cover that shields the blocks that constitute the block matrix so that they cannot be seen from the outside, the blocks including first blocks and second blocks that have different attenuation rates of the transmitted light rays, the block matrix being capable of being freely arranged,
a reference information generating step of detecting, with the detecting unit, the intensity of the light beam when the light beam is incident on the block matrix from the light source while increasing the number of the second blocks in each of the axial directions of the block matrix, and generating reference information indicating a relationship between the number of the second blocks and the intensity of the light beam detected by the detecting unit;
an arranging step of rearranging the arrangement of the first blocks and the second blocks in the block matrix and shielding them with the cover;
a measuring step of measuring, at least once, the intensity of the light beams transmitted through the block matrix in the axial direction by detecting, with the detecting unit, the intensity of the light beams when the light beams are incident from the light source in each of the axial directions of the block matrix in a state where the block matrix is shielded by the cover;
Includes.

This invention uses light rays with wavelengths longer than radiation instead of X-rays, allowing students to easily understand the configuration of the X-ray tube and detector in a computed tomography device, and the relationship between the detection results and the image. This allows students to learn the principles of image reconstruction in a computed tomography device in a safer and easier-to-understand manner.

1 is a perspective view of an experiment teaching material according to an embodiment of the present invention; FIG. 2 is a top view showing the configuration of the optical system of the experimental teaching material in FIG. 1. 1A is a perspective view of a first block, and FIG. 1B is a perspective view of a second block. FIG. 2 is a schematic diagram showing an example of the arrangement of first blocks and second blocks. 1A is a semi-logarithmic graph showing the relationship between the number of substances passing through and the intensity of transmitted light, and FIG. 1B is a flowchart showing how to use the experimental teaching material of FIG. FIG. 10 is a schematic diagram for determining block placement conditions. (A) to (D) are schematic diagrams showing the simplest block arrangement. 1A to 1C are schematic diagrams showing basic block arrangements. 10A to 10F are schematic diagrams showing an example of a placement operation procedure. 10 is a flowchart of an array generation process executed by the information processing device. 10A and 10B are top views showing modified examples of the experimental teaching material of FIG. 1. FIG. 10 is a perspective view of another example of a block structure constituting the experimental teaching material according to the embodiment of the present invention.

Embodiments of the present invention will now be described in detail with reference to the drawings. In each drawing, the same or equivalent parts are designated by the same reference numerals.

[Overall configuration]
1 is an experimental device used for learning the principles of image reconstruction in a computed tomography apparatus. The experimental device 1 includes a rectangular parallelepiped housing 2 and a lid 3 as covers, a block matrix body 4 housed in the housing 2 and the lid 3, and an optical probe 5 for inputting and outputting light rays.

As shown in Figure 1, the experimental teaching material 1 is used by placing it on a table (not shown) with the lid 3 facing up. In this embodiment, the up-down direction is defined as the Z-axis direction, and the normal directions to the side of the housing 2 are defined as the X-axis and Y-axis directions, and the explanation will be given with reference to these three-axis Cartesian coordinate system. The shape of the housing 2 and lid 3 is square when viewed from above.

A gap is provided between the housing 2 and the lid 3, through which a portion of the side of the block matrix 4 is exposed to the outside. The optical probe 5 is positioned so as to straddle the lid 3, with both ends of the optical probe 5 extending to the exposed portion of the block matrix 4.

[Optical probe]
The optical probe 5 emits a light beam from one end into the block matrix 4. The incident light beam travels straight through the block matrix 4, passes through it, and is received at the other end of the optical probe 5. Here, the light beam refers to an electromagnetic wave whose wavelength is in the range from the far ultraviolet region to the far infrared region. The wavelength of the light beam is longer than that of radiation such as X-rays, so there is no risk of radiation exposure. In this embodiment, the light beam is infrared.

The optical probe 5 can slide on the lid 3 in the Y-axis direction relative to the housing 2, lid 3, and block matrix 4. The optical probe 5 can also be installed so that it straddles the lid 3 in the Y-axis direction. In this case, the optical probe 5 can slide on the lid 3 in the X-axis direction. This allows the optical probe 5 to transmit infrared light in the Y-axis direction at any X position on the block matrix 4, and to transmit infrared light in the X-axis direction at any Y position.

The optical system of experimental teaching material 1 has the configuration shown in Figure 2. This optical system is centered around a block matrix element 4.

[Block matrix field]
The block matrix 4 is composed of a two-dimensional square matrix of blocks 10 made of a material that transmits infrared light IL. That is, the block matrix 4 is composed of an equal number of blocks 10 arranged in the X-axis and Y-axis directions that are orthogonal to each other. In this embodiment, the block matrix 4 has 5 rows and 5 columns.

As shown in Figures 3(A) and 3(B), the shape of the block 10 is a rectangular parallelepiped. The block 10 is made entirely of a material that transmits infrared light IL, such as plastic such as acrylic, or glass. For example, a plastic cell for a spectrophotometer can be used as the block 10.

Returning to Figure 2, the block matrix 4 has a frame member 4a into which the blocks 10 are inserted. The frame member 4a can be manufactured using a 3D printer or the like. The frame member 4a has insertion sections into which the blocks 10 are inserted, formed in a two-dimensional square matrix. The blocks 10 are inserted into the insertion sections of the frame member 4a to form the block matrix 4. The frame member 4a is made of the same material as the blocks 10. This allows the block matrix 4 to direct infrared light IL incident in the X-axis and Y-axis directions (row and column directions) of the two-dimensional matrix of the blocks 10 in a straight line.

[block]
In this embodiment, the block 10 includes a first block 10a and a second block 10b, as shown in Figures 3(A) and 3(B). The side surfaces of the first block 10a shown in Figure 3(A) do not have infrared cut filters attached to them that attenuate the infrared rays IL that pass through them. On the other hand, the second block 10b shown in Figure 3(B) has filters attached to it that absorb the infrared rays IL. Specifically, filters are attached to the +x-side and -y-side sides of the second block 10b. This results in different degrees of attenuation of the infrared rays IL that pass through the side surfaces of the first block 10a and the second block 10b.

The first block 10a indicates that there is no substance that absorbs the transmitted light, and the second block 10b indicates that there is a substance that absorbs the transmitted light. Therefore, hereinafter, the first block 10a will also be referred to as an empty cell, and the second block 10b will also be referred to as an absorbing cell.

Returning to Figure 2, the first blocks 10a and second blocks 10b can be freely arranged in the block matrix 4. In the experiment conducted with this experimental teaching material 1, the question setter first decides the arrangement of the first blocks 10a and second blocks 10b in the block matrix 4. The student conducting the experiment then measures the intensity of the infrared light IL that passes through each row and each column of the block matrix 4, and, based on the measurement results, estimates the arrangement of the first blocks 10a and second blocks 10b in the block matrix 4. This is the main content of the experiment.

[light source]
A light source 11 is provided at one end of the optical probe 5. The light source 11 emits infrared rays IL along the X-axis direction and the Y-axis direction into the block matrix 4. In this embodiment, the light source 11 includes a light-emitting diode that emits infrared rays IL. The infrared rays IL emitted from this light-emitting diode are incident on the block matrix 4. External power is supplied to the light source 11 via an AC adapter and a coaxial cable, and the light-emitting diode emits light using that power.

The electrical circuit within light source 11 is configured so that a constant intensity of infrared light IL is generated by flowing a current, adjusted to a constant level by a constant current diode, through the light-emitting diode using a voltage stepped down by a variable three-terminal regulator. Light source 11 may be equipped with several constant current diodes, making it possible to adjust the current flowing through the light-emitting diode. Light source 11 is also provided with a heat sink to dissipate heat generated by the light-emitting diode to the outside, thereby maintaining a constant internal temperature. In light source 11, light emitted from the photodiode is emitted only in the +X direction through a through hole so that it travels in the +X direction. The through hole serves to narrow the infrared light IL.

[Detection unit]
The detection unit 12 detects the intensity of the infrared light IL that has passed through the block matrix 4. The detection unit 12 includes a photodiode that outputs a signal corresponding to the intensity of the received infrared light IL, and a signal amplifier circuit connected to the photodiode. The infrared light IL that has passed through the block matrix 4 is received by the photodiode through the through-hole. The through-hole is provided so that the photodiode receives only the infrared light IL that has traveled straight through the block matrix 4. It is also desirable to use a photodiode that blocks visible light so as not to be affected by visible light.

The signal detected by the photodiode is amplified by a signal amplifier circuit including an operational amplifier and output from the detection unit 12. The signal amplifier circuit's amplification factor is adjustable using a variable resistor. The detection unit 12 is connected to a tester via a coaxial cable, and the tester displays the detection results of the transmitted light intensity of the detected infrared light IL. In the experiment, the arrangement of the first block 10a and the second block 10b is estimated based on the detection results of the tester. The light source 11 and detection unit 12 are stored in a drawer for easy viewing by students, and their circuit configuration may be confirmed by pulling out the drawer.

[Connection part]
In the optical probe 5, the light source 11 and the detection unit 12 are connected by a connection unit 13. This fixes the relative positional relationship between the light source 11 and the detection unit 12.

[Housing and Lid]
As shown in FIG. 1, the housing 2 and the lid 3 shield the arrangement of the blocks 10 that make up the block matrix 4 so that it cannot be seen from the outside.

[Principles of image reconstruction]
A computed tomography apparatus places an X-ray source and a detector facing an object, detects the intensity of transmitted X-rays from multiple directions, and performs computer processing based on the transmitted X-ray intensities in multiple directions to reconstruct an image showing the spatial distribution of the object. In contrast, in the experimental teaching material 1 according to this embodiment, a block matrix 4 is used as the detection target, and measurements are taken one baseline at a time from only two directions, "vertical" and "horizontal" (X-axis direction and Y-axis direction), with the aim of having students think about the internal structure of the object without using a computer. Naturally, there are cases where the information required for reconstruction from only two directions is insufficient and the internal structure of the object cannot be determined. However, in the experimental teaching material 1 according to this embodiment, prioritizing easy understanding of the principles of image reconstruction, the infrared IL is irradiated in two directions.

The transmitted light intensity of X-rays passing through a uniform medium decreases exponentially with the thickness x of the medium, according to the following equation (1) which represents Lambert's law.
I=I ₀ e ^-μx ...(1)
Here, _I0 is the incident light intensity, I is the transmitted light intensity, and μ is the absorption coefficient. I is the transmitted light intensity of the infrared IL measured by the tester. This Lambert's law also applies to infrared IL. If infrared IL passes through two materials, each with a thickness of d, the transmitted light intensity is as follows:
I = I ₀ e ^{-2 μd}

In Figure 4, the first block 10a is shown as a white square, and the second block 10b is shown as a hatched square. The width of each square on the X and Y axes is d. As mentioned above, the first block 10a does not have a filter that attenuates infrared IL, while the second block 10b has a filter that attenuates infrared IL. Therefore, here, it is assumed that the first block 10a does not contain any material, while the second block 10b does contain material. It is assumed that students performing the experiment are unaware of this internal structure. The numbers to the right and below the block matrix 4 in Figure 4 represent the total number of materials (total thickness) arranged in the corresponding row and column.

When infrared light IL passes through the block matrix 4 from left to right in the +X direction, where d is the width of each square, absorption occurs for a thickness of 3d in the first row, and absorption occurs for a thickness of 1d in the fifth row. Since the absorption coefficient μ of materials is the same, simply by measuring the transmitted light intensity I for a material with a known thickness, the number of materials on the path of the infrared light IL (total thickness) can be determined based on equation (1) above.

Once the number of substances on the path is determined, we next consider the internal structure of the specimen (block matrix body 4). In the arrangement shown in Figure 4, the number of substances in the second row and fourth column is 0, so it is immediately clear that the transmitted light intensity is equal to the incident light intensity and that no substances are present there. Next, considering the second column, the number of substances is 4, but since we know that there is nothing in the second row, we can see that there is substance everywhere else in the second column. Next, looking at the fifth row, we see that there is only one substance in the fifth row, but since we know that it is in the second column, we can see that there is no substance in the remaining locations. By considering this in this way, we can estimate which position in the five rows and five columns the substance is located.

[Experimental Procedure]
The specific experimental procedure performed by students using the experimental teaching material 1 will now be described.
1) In one row or one column, the transmitted light intensity of the infrared IL is measured while increasing the number of second blocks 10b, i.e., absorption cells 10b, from 0 to 5.
2) Plot the relationship between I/ _I0 and the number n of absorption cells 10b on a semi-logarithmic graph, where the axis of transmitted light intensity I/ _I0 is logarithmic (see FIG. 5A).
3) A block matrix 4 is generated that has an array of empty cells 10a and absorbing cells 10b to be estimated.
4) The lid 3 is placed over the sample, which is a 5-row, 5-column sample to be estimated and whose arrangement is unknown. The transmitted light intensity of infrared light IL is measured 10 times for each of the 5 rows in the row direction (X-axis direction) and the 5 columns in the column direction (Y-axis direction) for each of the 5 rows and the 5 columns, and the number of absorption cells 10b in each of the rows and columns is estimated based on the results of step 1).
5) The arrangement of the empty cells 10a and the absorption cells 10b in the block matrix 4 is estimated.
6) After the estimation, remove the lid 3 and check the contents.

Note that some older digital cameras do not have infrared blocking features. With the display of such a digital camera, it is possible to visually confirm that infrared light IL is being emitted from the light source 11.

In step 1), a block matrix of 2 rows and 5 columns to 6 rows and 5 columns may be prepared separately. By inserting the absorption cells 10b and empty cells 10a into this block matrix and shifting the optical probe 5, it is possible to simultaneously obtain multiple patterns of infrared IL transmitted light intensity. For example, if a block matrix of 6 rows and 5 columns is used, it is possible to obtain infrared IL transmitted light intensity for 0 to 5 absorption cells at a time.

In conducting this experiment, the relationship between the number n of material fibers and the normalized transmitted light intensity I/ _I0 must be linear, as shown by the solid line in the semi-logarithmic graph of Figure 5(A). If the sensitivity of the normalized transmitted light intensity I/ _I0 to changes in the number n of material fibers is low, as shown by the dotted line, or if the normalized transmitted light intensity I/ _I0 changes nonlinearly with changes in the number n of material fibers, as shown by the dash-dot line, it is necessary to adjust the filter of the second block 10b or the intensity of the infrared light IL emitted from the light source 11 so that the normalized transmitted light intensity I/ _I0 changes along the solid line with changes in the number n of material fibers.

The method of using the experimental teaching material 1 exemplified by the experimental procedure described above can be generalized, for example, as shown in the flowchart in Figure 5(B).

First, while increasing the number of second blocks 10b in one row or one column of the block matrix 4, the detection unit 12 detects the transmitted light intensity of infrared IL when infrared IL is incident on the block matrix 4 from the light source 11, and generates reference information indicating the relationship between the number of second blocks 10b and the transmitted light intensity of infrared IL detected by the detection unit 12 (step S1; reference information generation step). This step corresponds to the experimental procedures 1) and 2) described above.

Next, the arrangement of the first blocks 10a and second blocks 10b in the block matrix 4 is rearranged and shielded with the housing 2 and lid 3 (step S2; arrangement step). This step corresponds to the experimental procedure 3) described above.

Next, with the block matrix 4 shielded by the housing 2 and lid 3, the intensity of the infrared light IL incident on each row and column of the block matrix 4 from the light source 11 is detected by the detector 12, thereby measuring the intensity of the infrared light IL passing through each row and column of the block matrix 4 at least once (step S3; measurement step). This step corresponds to the above-mentioned experimental procedure 4). In experimental procedure 4), measurements are taken 10 times for each row and column, but this number is not limited.

Then, using the reference information generated in step S1 and the measurement results from step S3, the students estimate the arrangement of the first blocks 10a and second blocks 10b in the block matrix body 4, and then remove the lid 3 to confirm the arrangement. This corresponds to experimental procedure 5).

[Arrangement of empty cells and absorption cells]
The arrangement conditions of the first block 10a (empty cells) and the second block 10b (absorbing cells) will be described below. Here, the matrix of the blocks 10 in the block matrix field 4 is generalized to have n rows and n columns (n is a natural number).

Generally, when blocks 10 having an arbitrary absorption coefficient are inserted into a block matrix 4 having n rows and n columns, and infrared light IL is irradiated onto each row and each column for measurement, 2n pieces of data are obtained: n pieces of data I _m (m = 1 to n) corresponding to the transmitted light intensity of each row, and n pieces of data I _k (k = 1 to n) corresponding to the transmitted light intensity of each column. Data I _m corresponds to the number of second blocks 10 b in each row, and data I _n corresponds to the number of second blocks 10 b in each column.

In the experiment, these 2n pieces of data I _m and I _k are obtained. As shown in Fig. 6, if the element a _ij is set to 0 when it is in the first block 10a and set to 1 when it is in the second block 10b, it is possible to estimate whether each element a _ij is 0 or 1 by conditionally solving simultaneous equations based on the obtained data I _m and I _k . This condition means that the sum of the elements a _ij in each row or column is between 0 and n _, inclusive, since the element a _ij is either 0 or 1.

For example, if I _m =0 for a certain m, then for a _mi , a _m1 , a _m2 , a _m3 , ..., a _mn are all 0. Also, if I _m =n for a certain m, then for a _mi , a _m1 , a _m2 , a _m3 , ..., a _mn are all 1.

However, even if all elements are 0 or 1 and the number of measurable rows and columns is the same as the number of unknowns, a solution may not be found if the equations include non-independent equations. For example, even when n = 2, i.e., two rows and two columns, it is not possible to distinguish between the cases in Figure 7(A) and Figure 7(B) when measuring from two directions. This is because in both the cases in Figure 7(A) and Figure 7(B), the measurement result shows that the total amount of infrared light IL absorbed by the rows and columns is equal to one beam.

On the other hand, even if the number of absorption cells 10b and empty cells 10a is the same as in Figure 7(A), if their arrangement is as shown in Figure 7(C) or Figure 7(D), the arrangement of the empty cells 10a and absorption cells 10b can be uniquely determined. For example, in the arrangement shown in Figure 7(C), the following four equations are
a ₁₁ +a ₁₂ =2
a ₂₁ +a ₂₂ =0
a ₁₁ +a ₂₁ =1
a ₁₂ + a ₂₂ = 1
and it is possible to obtain a ₁₁ = 1, a ₁₂ = 1, a ₂₁ = 0, and a ₂₂ = 0. In an actual CT scanning device, X-rays are transmitted from oblique directions as well to measure their intensity, so the arrangement of the absorption cell 10b and empty cell 10a can be determined even if the arrangement is as shown in Figures 7(A) and 7(B). However, in experiments conducted from two directions, care must be taken in advance to avoid the arrangement shown in Figure 7(A) or 7(B).

Technically, whether the internal structure can be uniquely determined from the arrangement of blocks 10 in an n-by-n block matrix body 4 can be determined by exchanging rows or columns to see if it is possible to swap the entire row or column with the largest number of columns, moving to the top left, and then justifying the top left, bottom left, top right, or bottom right. In other words, for a two-dimensional square matrix of block 10 in the block matrix body 4, where empty cells 10a are set to 0 and absorbing cells 10b are set to 1, perform an exchange in a left (or right) elementary transformation to standardize it, and check whether the submatrix shown in Figure 7(A) or 7(B) is contained within. This confirmation is related to the operation of arranging 2n linear equations, creating a coefficient matrix, and performing elementary transformations.

[Placement Recipe]
Basically, by following the steps below, you can create an arrangement that will give you one answer.
1. As a basic model, first arrange the absorption cells 10b starting from the top left. As shown in Figures 8(A) to 8(C), if the number of absorption cells 10b decreases in the +X direction (right) and then in the -Y direction (left), the solution can be found by removing rows and columns that are all 0s or all 1s from the side.
2. The basic type cannot be solved by exchanging the entire column or the entire row. Taking advantage of this, examples of various derivations of the basic type are shown in Figure 9.

The operation is as follows:
Figure 9(A) to Figure 9(B): Swap row 3 and row 5. Figure 9(B) to Figure 9(C): Swap column 2 and column 5. Figure 9(C) to Figure 9(D): Move row 4 to the top. Figure 9(D) to Figure 9(E): Move column 4 to the left. Figure 9(E) to Figure 9(F): Insert column 4 after column 1.

The internal structure can be uniquely determined for any of the layouts shown in Figures 9(A) to 9(F). Of course, the entire layout may be rotated 90 degrees or inverted. Individual empty cells 10a and absorption cells 10b cannot be swapped. An example of 5 rows and 5 columns is given here, but this also applies to other numbers of rows and columns. In this way, by swapping or moving entire blocks in each column or entire blocks in each row with other rows, various internal structure layout examples can be created, and a block matrix body 4 can be generated that allows students to guess the interior from measurements.

In general, the smaller the matrix, the easier it is to derive the answer in your head, and the easier it is to solve if the layout is fixed. If there are columns or rows that contain only empty cells 10a, or columns or rows that are all absorbing cells 10b, the matrix can be made smaller immediately, making it easier for students to consider the layout.

Also, if the properties of the machine or film make it difficult to distinguish between five and four absorption cells 10b, the maximum number of absorption cells 10b in a row or column can be limited to four, and blank rows or columns can be used to fill the gaps. Conversely, if the amount of infrared IL light overflows and it is difficult to distinguish between zero and one, the number of absorption cells 10b can be increased.

The above-mentioned arrangement of empty cells 10a and absorption cells 10b can be generated by an information processing device. The information processing device generates the arrangement of empty cells 10a and absorption cells 10b to be estimated by having a computer execute a software program.

The information processing device includes a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), and a display. The CPU is a central processing unit, such as a microprocessor, that performs various processes and calculations. The information processing device reads a program stored in the ROM and executes the program on the CPU while using the RAM as work memory, thereby performing a process to generate an array pattern (array information) of the empty cells 10a and absorption cells 10b to be estimated, i.e., an array generation process.

As shown in FIG. 10 , in the array generation process, first, the information processing device inputs N (N is a natural number), which is information indicating the number of rows and columns of the two-dimensional square matrix, and M (M≦N ² ), which is the number of absorption cells 10b in the two-dimensional square matrix (step S11; input step).

Next, the information processing device generates a two-dimensional square matrix in which second blocks 10b are packed and arranged in one of the four corner areas of the two-dimensional square matrix based on N (N is a natural number), which is information indicating the number of rows and columns of the two-dimensional square matrix input in step S11, and M (M≦N ² ), which is the number of absorption cells 10b in the two-dimensional square matrix (step S12; matrix generation step). Here, for example, an arrangement of first blocks 10a and second blocks 10b as shown in FIG. 8(A) is generated as a basic pattern. There are multiple basic patterns to be generated, and the information processing device selects one from the multiple basic patterns using a random number. In these arrangements, the second blocks 10b are packed and arranged in the upper left. Alternatively, the second blocks 10b may be packed and arranged in the upper right, lower left, or lower right.

The information processing device then moves all of the blocks 10 in any row of the two-dimensional square matrix generated in step S11 to a different row, exchanges them with all of the blocks 10 in another row, or moves all of the blocks 10 in any column of the two-dimensional square matrix to a different column, or exchanges them with all of the blocks 10 in another column (step S13; matrix transformation step). For example, all of the blocks 10 in a row or all of the blocks 10 in a column are moved or exchanged according to the flow shown in Figures 9(A) to 9(F). Which rows and columns are moved or exchanged can be determined by random numbers. This generates arrangement information for the empty cells 10a and absorption cells 10b.

After completing step S12, the information processing device displays the arrangement information of the empty cells 10a and absorption cells 10b on the display (step S14; arrangement information output step). The empty cells 10a and absorption cells 10b are arranged according to the displayed arrangement information to generate a block matrix 4. Students use this block matrix 4 to conduct an experiment to estimate the arrangement from the transmitted light intensity of infrared light IL.

After step S14 is completed, the information processing device terminates the array generation process.

As explained in detail above, the experimental teaching material 1 according to the above embodiment uses light rays (infrared rays IL) with wavelengths longer than radiation in place of X-rays, making it possible to show students in an easy-to-understand manner the configuration of the X-ray tube and detector in a computed tomography device, and the relationship between the detection results and the image. As a result, students can learn the principles of image reconstruction in a computed tomography device in a safer and easier-to-understand manner.

Experiments using the experimental teaching material 1 according to the above embodiment are interesting cases with puzzle-like elements, which can motivate students to participate. Furthermore, since it does not require complex mathematical formulas, is simple to operate, and is visually easy to understand, even students with no mathematical background can conduct experiments that incorporate a physical perspective. Another advantage is that the simplified structure allows the experiment to be completed in a relatively short time.

In the experimental teaching material 1 according to the above embodiment, infrared light IL is used as the light beam. However, the present invention is not limited to this. Visible light or ultraviolet light may also be used as the light beam. Furthermore, while ultraviolet light does not expose or affect the human body as much as radiation such as X-rays, it is believed to be light that causes chemical changes in the human body, so it is preferable to use visible light or infrared light IL.

It is also possible to use light containing different wavelengths. For example, it is possible to use visible light such as red and green, and modify the method to study differences in absorption due to different colors.

In the experimental teaching material 1 according to the above embodiment, the second block 10b may be filled with a liquid that attenuates the light beam. In this way, it is possible to realize a second block 10b that attenuates the intensity of the light beam.

In the experimental teaching material 1 according to the above embodiment, the block matrix 4 is configured by inserting blocks 10 into frame members 4a. However, the present invention is not limited to this. The block matrix 4 may also be configured so that the sides of the blocks 10 are in direct contact with each other.

The number of blocks 10 in the row direction and the number of blocks 10 in the column direction of the block matrix 4 may be adjustable. As shown in Figures 11(A) and 11(B), the number of blocks 10 in the row direction and column direction may be arbitrary, and the length of the connecting portion 13 connecting the light source 11 and the detection portion 12 may be adjustable so that it can be adjusted according to the number of rows and columns of the blocks 10. In this case, different housings 2 and lids 3 may be provided depending on the number of rows and columns, or the housings 2 and lids 3 may be adjustable in size.

In addition, the light absorption rate in the blocks 10 may be set to three or more levels instead of two. For example, if a third block with a different absorption rate is added to the arrangement relative to the second block 10b, it becomes possible to estimate block arrangements in more complex situations. Blocks with such different absorption rates can be created by attaching film to four surfaces or by attaching multiple sheets on top of each other. Furthermore, if the light is visible light, they can be created by attaching films that absorb different colors.

Also, as shown in Figure 12, the block matrix body 4 composed of cubes can be made into a three-dimensional matrix body, and light can be incident on the block matrix body 4 from the X-axis, Y-axis, and Z-axis directions instead of just the X-axis and Y-axis directions, making it even closer to the structure of a computed tomography apparatus.

This invention allows for various embodiments and modifications without departing from the broad spirit and scope of the invention. Furthermore, the above-described embodiments are intended to explain the invention and do not limit the scope of the invention. In other words, the scope of the invention is defined by the claims, not the embodiments. Various modifications made within the scope of the claims and the meaning of the invention equivalent thereto are deemed to be within the scope of the invention.

It can be used as an experimental teaching material to understand the principles of image reconstruction using a computed tomography device.

1. Experimental material, 2. Housing, 3. Lid, 4. Block matrix, 4a. Frame member, 5. Optical probe, 10. Block, 10a. First block (empty cell), 10b. Second block (absorption cell), 11. Light source, 12. Detector, 13. Connection, IL. Infrared

Claims (7)

An experimental teaching material for learning the principles of image reconstruction using a computed tomography apparatus,
a block matrix configured by arranging an equal number of blocks formed of a material that transmits light rays having wavelengths longer than the radiation in a plurality of axial directions perpendicular to each other, and causing the light rays incident in the axial directions to travel straight in the axial directions;
a light source that directs the light beam into the block matrix along the axis;
a detection unit that detects the intensity of the light beam that has passed through the block matrix;
a cover that shields the blocks that constitute the block matrix so that they cannot be seen from the outside,
The blocks include a first block and a second block having different attenuation degrees of the transmitted light beam,
The block matrix allows the first blocks and the second blocks to be freely arranged.
Experimental teaching materials. a filter for attenuating the transmitted light beam is inserted into the second block;
The experiment teaching material according to claim 1. The second block is filled with a liquid that attenuates the light beam passing through it.
The experiment teaching material according to claim 1. The light is any one of infrared light, visible light, and ultraviolet light.
The experiment teaching material according to any one of claims 1 to 3. The block matrix is capable of adjusting the number of blocks in the axial direction.
The experiment teaching material according to any one of claims 1 to 4. 1. An array generation method for generating, by an information processing device, array information of first blocks and second blocks in a two-dimensional square matrix formed by an array of first blocks and second blocks, each having a different transmission intensity for a light beam having a wavelength longer than a radiation beam, the method comprising:
an input step of inputting information indicating N, which is the number of rows and columns of the two-dimensional square matrix, and information indicating M, (M≦N ² ), which is the number of second blocks in the two-dimensional square matrix;
a matrix generation step of generating the two-dimensional square matrix by packing the second blocks into any one of four corner areas of the two-dimensional square matrix based on the information input in the input step;
a matrix transformation step of moving an entire block of any row in the two-dimensional square matrix generated in the matrix generation step to a different row, or exchanging it with an entire block of any other row, or moving an entire block of any column in the two-dimensional square matrix to a different column, or exchanging it with an entire block of any other column;
Array generation methods including: a block matrix configured by arranging an equal number of blocks formed of a material that transmits light rays having wavelengths larger than that of radiation in a plurality of axial directions perpendicular to each other, the block matrix causing the light rays incident in the axial directions to travel straight in the axial directions; a light source that makes the light rays incident on the block matrix along the axial directions; a detection unit that detects the intensity of the light rays that have transmitted through the block matrix; and a cover that shields the blocks that constitute the block matrix so that they cannot be seen from the outside, the blocks including first blocks and second blocks that have different attenuation rates of the transmitted light rays, the block matrix being capable of being freely arranged,
a reference information generating step of detecting, with the detecting unit, the intensity of the light beam when the light beam is incident on the block matrix from the light source while increasing the number of the second blocks in each of the axial directions of the block matrix, and generating reference information indicating a relationship between the number of the second blocks and the intensity of the light beam detected by the detecting unit;
an arranging step of rearranging the arrangement of the first blocks and the second blocks in the block matrix and shielding them with the cover;
a measuring step of measuring, at least once, the intensity of the light beams transmitted through the block matrix in the axial direction by detecting, with the detecting unit, the intensity of the light beams when the light beams are incident from the light source in each of the axial directions of the block matrix in a state where the block matrix is shielded by the cover;
How to use the experimental materials, including: