Phantom and Examination Method

Abstract

To provide a phantom that acquires a desired CT value and an effective atomic number and is adjustable to a desired electron density when performing dual-energy type CT inspection and X-ray inspection.SOLUTION: A phantom is used for any one of the inspection apparatuses selected from a CT examination apparatus and an X-ray inspection apparatus. The phantom includes: a support member; and an elastic body supported by the support member. Changing density or thickness of the elastic body relating to an X-ray irradiation direction from an X-ray irradiation source of the inspection apparatus adjusts at least one of the effective atomic number and electron density.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a phantom and an inspection method. [Background technology]

[0002] In the medical field, image diagnosis and simulation learning are crucial. Phantoms are used as simulators for image diagnosis in the medical field (for example, Non-Patent Documents 1-4).

[0003] The phantom described in Non-Patent Literature 1 simulates the thoracic structure of the human body, including the skeleton and internal lung structure, and captures structures similar to those of the human body in X-ray and CT images. Non-Patent Literature 1 shows simulated lesions with predetermined CT values ​​(equivalent to -800HU, -630HU, and +100HU) corresponding to specific lesions. In Non-Patent Literature 1, by capturing X-ray and CT images with the simulated lesion housed within the thoracic structure, it is possible to simulate how the lesion will appear according to diagnostic conditions (for example, Non-Patent Literature 2).

[0004] Non-patent document 2 reports the results of verifying the visibility of GGO in chest X-ray CT images and chest X-ray tomosynthesis using the phantom described in Non-patent document 1.

[0005] Non-Patent Document 3 describes a phantom for chest CT screening. It is disclosed that performing a CT scan on the phantom of Non-Patent Document 3 produces artifacts similar to those found in the human body. The phantom of Non-Patent Document 3 is equipped with simulated lesions exhibiting ground-glass opacity (GGO) at predetermined CT values, allowing for the simulation of how lesions appear and the amount of radiation exposure according to diagnostic conditions (for example, Patent Document 4). GGO is observed in many imaging findings when pneumonia develops due to respiratory diseases, including COVID-19.

[0006] Non-patent document 4 reports the results of a physical evaluation using "low-dose chest X-ray CT" with reduced radiation exposure, utilizing the phantom described in non-patent document 3.

[0007] Furthermore, in recent years, dual-energy CT and X-ray scanners, which utilize X-rays of multiple wavelengths, have rapidly become widespread. Dual-energy CT and X-ray scanners can calculate the effective atomic number and electron density of tissue from data acquired with X-rays of different energies, making them superior to single-energy CT and X-ray scanners that use only one type of energy. Thus, dual-energy scanners are attracting attention because they can obtain image information with higher diagnostic value compared to single-energy scanners. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] "Chest Phantom N-1 Langman", Kyoto Science Co., Ltd. [Non-Patent Document 2] Kyung Won Doo, et al. “Comparison of chest radiography, chest digital tomosynthesis and low doseMDCT to detect small ground-glass opacity nodules: an anthropomorphic chest phantom study” Eur Radial(2014)24:3269-3276 [Non-Patent Document 3] "LSCT Phantom LSCT-001 Model", Kyoto Science Co., Ltd. [Non-Patent Document 4] Toru Matsumoto, "Development of a Manual for MDCT (multidetector-row CT) Imaging for Lung Cancer Screening: Fiscal Year 2005 Technical Committee Report (Detailed Version)" [Overview of the project] [Problems that the invention aims to solve]

[0009] However, phantoms such as those in Non-Patent Documents 1 and 3 were commercialized before the dual-energy CT inspection apparatus and X-ray inspection apparatus were made public, and they are not compatible with the dual-energy inspection apparatus. Specifically, when an X-ray image or a CT image is taken using a simulated lesion and a phantom such as those in Non-Patent Documents 1 and 3 with a dual-energy inspection apparatus, even if the image luminance (density) and CT value corresponding to a specific lesion are obtained, both the effective atomic number and the electron density cannot be reproduced. In the methods disclosed in Non-Patent Documents 2 and 4, there is no mention of a dual-energy inspection apparatus, and there is no disclosure or suggestion that the above problems will occur when the above phantom is used in a dual-energy inspection apparatus.

[0010] Since the degree of a lesion, such as its size, changes, it is considered that improving the accuracy of the inspection can be achieved by deforming the simulated lesion according to the degree of the lesion.

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide a phantom that can obtain a desired CT value and effective atomic number and can be adjusted to a desired electron density when performing dual-energy CT inspection and X-ray inspection, and an inspection method using the phantom.

Means for Solving the Problems

[0012] (1) The phantom according to the first aspect of the present invention is a phantom used in any inspection apparatus selected from a CT inspection apparatus and an X-ray inspection apparatus, comprising a support member and an elastic body supported by the support member, wherein the electron density is adjusted by changing the density or thickness of the elastic body in the X-ray irradiation direction from the X-ray irradiation source of the inspection apparatus.

[0013] (2) In the phantom of (1) above, the support member may include a first plate portion and a second plate portion that sandwich the elastic body, and a fastening member that fastens the first plate portion and the second plate portion so that the distance between the first plate portion and the second plate portion can be adjusted.

[0014] (3) In the phantom of (1) or (2) above, the density of the elastic body in the X-ray irradiation direction of the inspection device may be changed by the compression ratio of the elastic body.

[0015] (4) In the phantom of any one of (1) to (3) above, the elastic body may contain latex as a main component.

[0016] (5) In the phantom of any one of (1) to (4) above, the elastic body may further contain sulfur.

[0017] (6) The inspection method according to the second aspect of the present invention performs a CT inspection using the phantom according to the first aspect, and inspects the CT value, the effective atomic number, and the electron density of the elastic body.

[0018] (7) In the inspection method of (6) above, after the CT inspection, an X-ray inspection may be performed using the phantom, and the way the image appears in the X-ray inspection of the elastic body may be observed.

Advantages of the Invention

[0019] According to the present invention, when performing dual-energy CT inspection and X-ray inspection, it is possible to obtain a desired CT value and effective atomic number, and to provide a phantom that can be adjusted to a desired electron density and an inspection method using the phantom.

Brief Description of the Drawings

[0020] [Figure 1] A perspective view schematically showing a phantom according to an embodiment of the present invention. [Figure 2] A plan view schematically showing the upper surface of the phantom of FIG. 1. [Figure 3] Figure 1 is a schematic cross-sectional view showing a cross-section of the phantom. [Figure 4] This is a schematic cross-sectional view showing a modified version of the phantom shown in Figure 1. [Figure 5] This is a schematic cross-sectional view showing a modified version of the phantom shown in Figure 1. [Figure 6] This is a schematic perspective view showing a modified version of the phantom shown in Figure 1. [Figure 7] This figure shows CT images taken using a dual-energy CT scan with the phantoms of Examples 1-3, and the CT values. [Figure 8] This figure shows CT images taken using a dual-energy CT scan with the phantoms of Examples 1-3, illustrating the effective atomic number. [Figure 9] This figure shows the electron density in CT images acquired by dual-energy CT scans using the phantoms of Examples 1-3. [Figure 10] This figure shows an example of the arrangement when applying a phantom to an X-ray apparatus. [Figure 11] This is an X-ray image taken using a phantom as a reference example. [Figure 12] The images shown are X-ray images taken of the phantom using a dual-energy X-ray system and X-ray images taken using a single-energy X-ray system. [Figure 13] The images shown are X-ray images taken using a phantom with a dual-energy X-ray system and X-ray images taken using a single-energy X-ray system. [Figure 14] The images shown are X-ray images taken using a phantom with a dual-energy X-ray system and X-ray images taken using a single-energy X-ray system. [Modes for carrying out the invention]

[0021] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. Note that, for convenience, the drawings used in the following description may show enlarged versions of characteristic parts in order to clearly illustrate the features of the present invention. Therefore, the dimensional ratios of each component may differ from those of the actual components.

[0022] [phantom] Figure 1 is a schematic perspective view showing a phantom according to one embodiment of the present invention. Figure 2 is a schematic plan view showing the top surface of the phantom in Figure 1, and Figure 3 is a schematic cross-sectional view showing a cross-section of the phantom in Figure 1.

[0023] The phantom 100A shown in Figures 1-3 is a phantom used in a CT scanner, comprising a support member 20 and an elastic body 10 supported by the support member 20, and the electron density is controlled by changing the density of the elastic body 10 in relation to the X-ray irradiation direction from the X-ray irradiation source of the scanner.

[0024] (Elastic body) The elastic body 10 is, for example, a laminate in which at least one elastic layer 1 made of an elastic material is stacked. Figures 1 to 3 show how three elastic layers 1 are stacked. Each of the elastic layers 1 has, for example, the same shape. In the elastic body 10, by making each elastic layer 1 have a uniform shape, the compressibility of the elastic layers 1 can be made uniform. The elastic layers 1 are, for example, detachably provided. As described above, in the elastic body 10, each of the elastic layers 1 is compressed uniformly. In the example shown in Figures 1 to 3, each elastic layer 1 is compressed to 1 / 3 of its thickness compared to when no external pressure is applied.

[0025] The elastic layer 1 is substantially composed of an elastic material. This elastic material is deformable by compression. Preferably, the elastic layer 1 is composed of a material with a high bulk modulus, such as those exemplified below. By composing the elastic layer 1 of such an elastic material, the CT value and effective atomic number of phantom 100A can be maintained and the electron density can be controlled by compression.

[0026] The elastic material constituting the elastic layer 1 mainly consists of latex, synthetic rubber, etc. When the elastic material mainly consists of latex, the elastic material is, for example, vulcanized. The sulfur content in the elastic body 10 can be appropriately selected, but for example, it is 5-8 wt%. Since the atomic number of sulfur is larger than the effective atomic number of latex (approximately 8), increasing the sulfur content increases the effective atomic number of the elastic body. The elastic body contains sulfur, and the effective atomic number may be controlled by the sulfur content.

[0027] The elastic body 10 is supported, for example, on both sides in the stacking direction (z-direction in Figures 1-3) by the first plate portion 21a and the second plate portion 21b of the support member 20. The thickness of the elastic body 10 and the volume of the elastic body 10 are adjusted by adjusting the distance between the first plate portion 21a and the second plate portion 21b, as will be described later. When the volume of the elastic body 10 and the elastic body 10 itself decrease, the electron density of the elastic body 10 increases.

[0028] The elastic body 10 is, for example, a sponge material. The porosity of the elastic body 10 is, for example, 85% or less.

[0029] (Support member) The support member 20 supports the elastic body 10. The support member 20 includes, for example, a first plate portion 21a and a second plate portion 21b that sandwich the elastic body 10, and a fastening member 22 that fastens the first plate portion 21a and the second plate portion 21b together so that the distance between the first plate portion 21a and the second plate portion 21b can be adjusted.

[0030] The support member 20 is made of a material such as polypropylene, nylon, or polycarbonate, and is preferably made of polypropylene, nylon, or polycarbonate. Because such materials have low X-ray absorption, the generation of artifacts can be suppressed, and more reliable data can be obtained in terms of CT value, effective atomic number, and electron density. The X-ray mass attenuation coefficient of the materials constituting the first plate portion 21a and the second plate portion 21b is, for example, 1.6 × 10⁻¹⁰ when the effective energy of continuous X-rays at a tube voltage of 120 kV is 60 keV.-1 ~2.6×10 -1 cm 2 / g, and preferably 1.7×10 -1 ~2.4×10 -1 cm 2 / g, and more preferably 1.8×10 -1 ~2.1×10 -1 cm 2 / g. Further, when the effective energy of the continuous X-ray at a tube voltage of 120 kV is 60 keV, the mass attenuation coefficient of the X-ray of the material constituting the first plate portion 21a and the second plate portion 21b is 1.4×10 -1 ~2.5×10 -1 cm 2 / g, and preferably 1.5×10 -1 ~2.2×10 -1 cm 2 / g, and more preferably 1.6×10 -1 ~2.0×10 -1 cm 2 / g. In addition, the mass attenuation coefficient of cartilage is 2.042×10 -1 cm 2 / g at an effective energy of 60 keV of the continuous X-ray at a tube voltage of 120 kV, and 1.823×10 -1 cm 2 / g at 80 keV. Further, by forming the support member 20 with these materials, the strength to adjust the elastic body 10 to a desired thickness is ensured.

[0031] The first plate portion 21a and the second plate portion 21b extend in a direction perpendicular to the lamination direction of the elastic body 10, for example. The first plate portion 21a and the second plate portion 21b are provided with through holes at positions where fastening members 22, described later, are provided. The first plate portion 21a and the second plate portion 21b are formed of, for example, polypropylene, and are preferably made of polypropylene. The thickness of the first plate portion 21a and the second plate portion 21b is, for example, 1 mm or more and 10 mm or less. From the viewpoint of suppressing the influence on measurement results in X-ray inspection, it is preferable that the thickness of the first plate portion 21a and the second plate portion 21b be small, and by keeping it within the above range, excessive influence can be suppressed. Furthermore, from the viewpoint of ensuring strength that can deform the thickness of the elastic body 10, it is preferable that the thickness be large, and by keeping it within the above range, the reliability of the strength can be increased even when the elastic body 10 is greatly compressed.

[0032] The fastening member 22 includes, for example, a member that extends in a direction intersecting the expanding surfaces of the first plate portion 21a and the second plate portion 21b, and connects the first plate portion 21a and the second plate portion 21b in a manner that allows for adjustment of the distance between them. The fastening member 22 is composed of, for example, a bolt 22a and a nut 22b. The bolt 22a is made of, for example, a base material such as nylon, and is preferably made of nylon. The fastening member 22 is provided at two locations in the plane, as shown in Figure 2.

[0033] The nut 22b is made of a base material such as polycarbonate, and is preferably made of polycarbonate. By making the fastening member 22 of the above material, the X-ray absorption coefficient can be reduced and sufficient strength can be ensured to deform the elastic body 10.

[0034] The threaded top of the bolt 22a is located on the side of the first plate portion 21a opposite to the elastic body 10 in the z-direction. The shaft of the bolt 22a penetrates, for example, the first plate portion 21a and the second plate portion 21b. The in-plane spacing between the shafts of the bolts 22a can be, for example, the same as the in-plane width of the elastic body 10. The nut 22b is provided on the side of the second plate portion 21b opposite to the elastic body 10 and is screwed onto the portion of the bolt 22a that extends from the second plate portion 21b.

[0035] In the phantom 100A, the distance between the first plate portion 21a and the second plate portion 21b can be adjusted by tightening a nut, thereby adjusting the compressibility of the elastic body 10. Here, even if the compressibility of the elastic body 10 in the phantom 100A is adjusted by the distance between the first plate portion 21a and the second plate portion 21b, there is no change in the CT value and effective atomic number in the CT examination. On the other hand, as described above, when the compressibility of the elastic body 10 in the phantom 100A is adjusted, the density of the elastic body 10 changes, and the electron density of the elastic body 10 changes. In other words, according to the phantom 100A of this embodiment, it is possible to obtain a desired CT value and effective atomic number, and to provide a phantom that can be adjusted to a desired electron density. The CT value and effective atomic number can be adjusted by selecting a substrate for the elastic body, and by selecting a substrate corresponding to a predetermined lesion and adjusting the electron density by adjusting the density of the elastic body in the X-ray irradiation direction from the X-ray irradiation source, it is possible to provide a phantom that can correspond to a predetermined lesion.

[0036] (modified version) The present invention is not limited to the phantom 100A according to the above embodiment, and can be modified as appropriate within the scope of the gist described in the claims. For example, phantoms 100B and 100C may be as shown in Figures 4 and 5. In the modified phantom 100D, components similar to those in phantom 100A are denoted by the same reference numerals and their descriptions are omitted.

[0037] Phantom 100B and 100C differ in the number of elastic layers 1 contained in the elastic body 10 and their compressibility. The elastic body 10 in Phantom 100B has two elastic layers 1. By reducing the number of layers in the elastic body 10 in Phantom 100B to 2 / 3 times that of Phantom 100A and aligning the height of the elastic body 10 in the stacking direction, the compressibility of the elastic body 10 can be reduced to 2 / 3 times, and the electron density of the elastic body 10 can be adjusted to 2 / 3 times. The elastic body 10 in Phantom 100C consists of only one elastic layer 1. By reducing the number of layers in the elastic body 10 in Phantom 100C to 1 / 3 times that of Phantom 100A and aligning the height of the elastic body, the compressibility of the elastic body 10 can be reduced to 1 / 3 times, and the electron density of the elastic body 10 can be adjusted to 1 / 3 times.

[0038] Here, in phantoms 100B and 100C, there is no change in the configuration of the elastic layer 1 forming the elastic body 10, other than the compressibility, compared to phantom 100A. Therefore, even if the number of layers and compressibility of the elastic body 10 are adjusted, there is no change in the CT value and effective atomic number of the elastic body 10. Thus, it is possible to obtain the desired CT value and effective atomic number, and to adjust to the desired electron density.

[0039] Figure 6 is a schematic perspective view showing a phantom 100D relating to another modification of Figure 1. Phantom 100D differs from phantom 100A in that the lamination direction of the elastic layer 1D in the elastic body 10D intersects with the direction perpendicular to the planes of the first plate portion 21a and the second plate portion 21b, and the thickness of the elastic layer 1D when no pressure is applied. As shown in Figure 6, in phantom 100D, the elastic body 10D may be compressed in a direction intersecting the lamination direction. Even in such a case, the CT value and effective atomic number of the elastic body 10D can be set to desired values ​​because they are inherited from those of the elastic material forming the elastic body 10D, and the electron density can be adjusted to a desired value by the density of the elastic body.

[0040] Figures 1-6 show phantoms in which the elastic layers 1 and 1D forming the elastic bodies 10 and 10D have the same shape. However, the elastic layers 1 forming the elastic bodies 10 and 10D may each have different shapes. Also, Figures 1-6 show an example in which the fastening member 22 consists of a bolt 22a and a nut 22b. However, other fastening materials may be used as long as they are capable of fastening the first plate portion 21a and the second plate portion 21b while the elastic bodies 10 and 10D are compressed, that is, fastening them in a way that allows adjustment of the distance between the first plate portion 21a and the second plate portion 21b.

[0041] The above embodiment describes a phantom used in a CT scanner, but the present invention is considered applicable to X-ray inspection equipment by selecting the material type of the support member 20. Specifically, it is considered usable in X-ray inspection equipment by selecting the material type of the support member 20. Furthermore, as shown in Figure 10, which will be described later, it is possible to use them stacked without using a support member and apply this to measuring the apparent effective density change.

[0042] These materials have an X-ray absorption coefficient close to that of air in X-ray images, and also possess the strength to compress and support the elastic body 10. In the phantom of an X-ray inspection device, the electron density of the elastic body 10 is adjusted by changing the thickness of the elastic body 10 in relation to the direction of X-ray irradiation from the X-ray irradiation source. Therefore, in a phantom for an X-ray inspection device, for example, the direction of stacking of the elastic body 10 is approximately the same as the direction of X-ray irradiation from the X-ray irradiation source.

[0043] An inspection method according to one aspect of the present invention involves performing a CT inspection using phantoms 100A, 100B, 100C, and 100D according to the above aspect, to inspect the CT value, effective atomic number, and electron density of the elastic body 10 (CT inspection step). In the CT inspection step, it is preferable that phantom 100A captures a cross-section between two fastening members 22 so that the fastening members 22 do not appear in the CT image. By capturing such a cross-section, it is easier to suppress the influence of members other than the elastic body 10 being inspected on the measurement results of the CT value, effective atomic number, and electron density.

[0044] An inspection method according to one aspect of the present invention further involves performing an X-ray inspection using phantoms 100A, 100B, 100C, and 100D after the CT scan, and observing how the image of the elastic body 10 appears in the X-ray inspection (X-ray inspection step).

[0045] In the X-ray examination process, for example, the phantoms 100A, 100B, 100C, and 100D used in the CT examination process can be used as is. In the X-ray examination process, the phantoms 100A, 100B, 100C, and 100D are arranged so that the stacking direction of the elastic body 10 is the same as the X-ray irradiation direction from the X-ray irradiation source. According to this embodiment, since parameters specific to the elastic body 10, such as the CT value, effective atomic number, and electron density of the elastic body 10, have already been obtained in the CT examination process, it is possible to observe how lesions appear in X-ray images corresponding to these parameters. Although it is not possible to perform either the CT examination process or the subsequent X-ray examination process on the human body as in this examination method, by using the phantoms 100A, 100B, 100C, and 100D according to the above embodiment, for example, in the X-ray examination process, it is possible to examine how a predetermined lesion appears in an X-ray image when a predetermined X-ray examination is performed on it. In other words, it is possible to estimate the minimum X-ray dose required to confirm a specific lesion in an X-ray image, and it may also be possible to objectively evaluate the diagnostic capabilities of different X-ray examination methods. Compared to chest X-ray CT, chest X-ray has advantages such as lower radiation exposure, smaller equipment size, and higher examination throughput. Even lesions that are difficult to detect with single-energy X-ray examinations such as GGO can be improved in this dual-energy X-ray examination by suppressing the effect of bone shadows. [Examples]

[0046] The following describes embodiments of the present invention. The present invention is not limited to the following embodiments.

[0047] [Example 1] As Example 1, a phantom with an arrangement similar to phantom 100A, as shown in Figure 1, was manufactured, and the CT value, effective atomic number, and electron density of the elastic body were examined by CT inspection. The manufacturing method of the phantom in Example 1 is described below.

[0048] <The creation of the Phantom> First, as an elastic body, one piece of latex (manufactured by TONY'S COLLECTION INC., product name: Natural Latex Sponge) was prepared. The elastic body used had dimensions of width: 2 cm, depth: 2.5 cm, and thickness: 2 cm in an environment where no external pressure was applied.

[0049] Next, two plate sections and two fastening members were prepared to constitute the support member. For the plate section, a 2mm thick polypropylene plate (product number: 4549131311358, PP sheet (milky white, double-sided glossy)) was used. For the fastening members, a bolt (Hirosugi Keiki Co., Ltd., model number: PCBT-0840W) and a nut (Hirosugi Keiki Co., Ltd., model number: PCNT-08) made of polycarbonate were used.

[0050] Each of the two plate sections has two through-holes formed in positions that overlap when viewed from a plane perpendicular to the surface. The spacing between the through-holes in the plate sections in the width direction corresponds to the width of the elastic body.

[0051] Next, the elastic body was placed between the two plate sections, and the fastening member was tightened to adjust the distance between the plate sections to 2 cm, thereby preparing the phantom. In Example 1, the two plate sections are in contact with the elastic body.

[0052] [Example 2] A phantom was fabricated in the same manner as in Example 1, except that the number of elastic bodies installed in the phantom was changed to two. As the elastic bodies, those having the same dimensions in an environment where no external pressure was applied were used. The elastic bodies were stacked along the plane normal direction of the plate portion to form a laminate, and the phantom was formed by adjusting the total thickness of the laminate to be the same as that in Example 1 (2 cm) when the fastening member was tightened. That is, in Example 2, the density per unit volume of the elastic body was twice that of Example 1.

[0053] Next, for this phantom, in the same manner as in Example 1, a CT image was taken in a direction intersecting the depth direction of the elastic body, and the CT value, effective atomic number, and electron density of the elastic body provided in the phantom were examined.

[0054] [Example 3] A phantom was fabricated in the same manner as in Example 1, except that the number of elastic bodies installed in the phantom was changed to three and the plate portion was changed to a thicker one so as to ensure the strength for compressing more elastic bodies. The elastic bodies were stacked along the plane normal direction of the plate portion to form a laminate as in Example 2, and by tightening the fastening member, the total thickness of the laminate was adjusted to be the same as that in Example 1 (2 cm). That is, in Example 3, the density per unit volume of the elastic body was three times that of Example 1. The thickness of the plate portion was 4 mm by stacking two 2-mm-thick plates.

[0055] [CT Examination] The phantoms of Examples 1 to 3 were placed in a CT scanner (Canon, model: Aquilion ONE SPECTRAL Edition TSX-306A), and CT scan images were taken of cross-sections in a direction intersecting the depth direction of the elastic material provided in the phantom. The CT value, effective atomic number, and electron density were analyzed by analyzing the position corresponding to the elastic material contained in the phantom. Dual-energy CT scanning of the CT scan images was performed with the above CT scanner, and the obtained image data was analyzed using the analysis software Vitrea (Canon). Figures 7 to 9 show CT images taken by dual-energy CT scanning using the phantoms of Examples 1 to 3. Figures 7, 8, and 9 show the CT value, effective atomic number, and electron density of the elastic material provided in the phantom, respectively. In Figures 7 to 9, the CT scan images of Example 1(a), Example 2(b), and Example 3(c) are shown from left to right. In Figures 7 to 9, the areas where analysis was performed are indicated by circles. Tube voltage: 135 kVp, 80 kVp (dual energy system) Tube current: 350mA Scanning method: Helical scan Image slice thickness: 0.5 mm Number of rows for shooting: 80 rows Beam pitch: 1.4

[0056] (CT value) The CT values ​​of the elastic bodies provided in the phantoms of Examples 1, 2, and 3 were -826.60HU, -744.93HU, and -606.04HU, respectively, and were confirmed to be approximately equivalent in Examples 1 to 3.

[0057] (Effective atomic number) The average effective atomic numbers of the elastic bodies in the phantoms of Examples 1, 2, and 3 were 8.46, 8.22, and 7.52, respectively. In the phantoms of Examples 1 to 3, the number and density of the elastic bodies were changed, but different materials were not used, so it was confirmed that there was no change in the effective atomic number. Furthermore, the effective atomic number of the lesion GGO disclosed in the literature "Classification of X-ray attenuation coefficients and medical images, Shinichiro Iwamoto" is approximately 7.60, and it was confirmed that Examples 1 to 3, which were intended to simulate this lesion, were able to adjust to the desired effective atomic number. Note that in Example 3, the effective atomic number is slightly smaller compared to Examples 1 and 2, which is thought to be due to the effect of changing the thickness of the plate, for example, the effective energy of continuous energy X-rays has changed, i.e., the penetrating power has changed.

[0058] (electron density) The electron density of the elastic material provided in the phantoms of Examples 1, 2, and 3 was 0.42 × 10⁻¹⁴, respectively. 23 [cm -3 ],0.81×10 23 [cm -3 ], 1.30 × 10 23 [cm -3 ] In Examples 2 and 3, it was confirmed that the electron density was adjusted to twice and three times the original density by changing the density of the elastic material to twice and three times the original density, respectively, compared to Example 1. By comparing Examples 1 to 3, it was confirmed that when performing a dual-energy CT scan, the desired CT value and effective atomic number can be obtained, and a phantom that can be adjusted to the desired electron density can be provided.

[0059] [Reference examples 1~3] In Reference Examples 1-3, the elastic bodies used in Examples 1-3 were used as phantoms without applying external pressure. In Reference Examples 1-3, the elastic bodies used in Examples 1-3 were arranged on the back of a chest phantom N-1 Langman (manufactured by Kyoto Kagaku Co., Ltd.) that simulates the chest of a human body, and X-ray images were taken using a dual-energy X-ray inspection method. Figure 10 shows an example of the arrangement when the phantoms of the Reference Examples are applied to an X-ray apparatus. The phantoms were arranged on an angle-adjustable base 30 so that the image-forming surface was perpendicular to the X-rays emitted from the X-ray source. The angle-adjustable base 30 was made of expanded polystyrene with a high air content and a low X-ray absorption coefficient. The angle of the angle-adjustable base 30 was adjusted appropriately for each position where the phantoms were arranged.

[0060] In Reference Example 1, the single elastic body used in Example 1 was used without applying external pressure. That is, in Reference Example 1, the thickness of the elastic body was 2 cm. In Reference Example 1, the phantom was positioned so as to overlap with the clavicle and ribs in the direction of X-ray irradiation from the X-ray irradiation source.

[0061] [Reference example 2] In Reference Example 2, the two elastic bodies used in Example 2 were arranged so as to overlap in the direction of X-ray irradiation from the X-ray irradiation source, and were used without applying external pressure. That is, in Reference Example 2, the total thickness of the elastic bodies was 4 cm. Similar to Reference Example 1, the phantom in Reference Example 2 was arranged so as to overlap with the clavicle and ribs in the direction of X-ray irradiation from the X-ray irradiation source.

[0062] [Reference example 3] In Reference Example 3, the three elastic bodies used in Example 3 were arranged so as to overlap in the direction of X-ray irradiation from the X-ray irradiation source, and were used without applying external pressure. That is, in Reference Example 3, the total thickness of the elastic bodies was 6 cm. Similar to Reference Example 1, the phantom in Reference Example 3 was arranged so as to overlap with the clavicle and ribs in the direction of X-ray irradiation from the X-ray irradiation source.

[0063] [Comparative Examples 1-3] For Comparative Examples 1, 2, and 3, X-ray images were taken in the same manner as in Reference Examples 1, 2, and 3, except that single-energy X-ray examinations were performed.

[0064] Figure 11 shows an X-ray image taken using the reference example phantom. Reference Examples 1-3 and Comparative Examples 1-3 all use experimental data where the phantom was positioned at position "3" in the X-ray image of Figure 11.

[0065] Figure 12(a) shows an X-ray image taken using a phantom in a dual-energy X-ray inspection in Reference Example 1, and Figure 12(b) shows an X-ray image taken using a phantom in a single-energy X-ray inspection in Comparative Example 1. Similarly, Figures 13(a) and 14(a) show X-ray images taken using a phantom in a dual-energy X-ray examination in Reference Example 2 and Reference Example 3, respectively, while Figures 13(b) and 14(b) show X-ray images taken using a phantom in a single-energy X-ray examination in Reference Example 2 and Reference Example 3, respectively.

[0066] In Figures 12-14, comparing the X-ray images taken using the dual-energy X-ray method with those taken using the single-energy X-ray method, the single-energy X-ray images in Figures 12(b), 13(b), and 14(b) were difficult to distinguish between bone shadows and phantom shadows due to the presence of bone shadows in the clavicle and ribs, resulting in poor visibility of phantom shadows simulating lesions. On the other hand, the dual-energy X-ray images in Figures 12(a), 13(a), and 14(a) showed high visibility of phantom shadows, even for information in the body thickness direction, which is inherently difficult to read, because the bone shadows were removed. [Industrial applicability]

[0067] This is useful for the development of dual-energy inspection methods and for realizing X-ray inspection methods with low X-ray exposure. [Explanation of symbols]

[0068] 1: Elastic layer, 10, 10D: Elastic body, 20: Support member, 21a: First plate section, 21b: Second plate section, 22: Fastening member, 22a: Bolt, 22b: Nut, 100A, 100B, 100C, 100D: Phantom

Claims

1. A phantom used in either a CT scanner or an X-ray scanner, The device comprises a support member and an elastic body containing latex as its main component, which is supported by the support member. A phantom in which the electron density is adjusted by changing the density or thickness of the elastic body in relation to the X-ray irradiation direction from the X-ray irradiation source of the inspection apparatus.

2. The phantom according to claim 1, wherein the support member comprises a first plate portion and a second plate portion that sandwich the elastic body, and a fastening member that fastens the first plate portion and the second plate portion so as to be able to adjust the distance between the first plate portion and the second plate portion.

3. The phantom according to claim 1 or 2, wherein the density of the elastic body with respect to the X-ray irradiation direction of the inspection apparatus is changed by the compressibility of the elastic body.

4. The phantom according to claim 1, wherein the elastic body further contains sulfur.

5. A method for performing a CT scan using the phantom described in claim 1, and for examining the CT value, effective atomic number, and electron density of the elastic body.

6. The inspection method according to claim 5, wherein, after the CT scan, an X-ray inspection is performed using the phantom, and the appearance of the image in the X-ray inspection of the elastic body is observed.

Images