Multipurpose CT image quality evaluation die body

Abstract

The utility model provides a multipurpose CT (Computed Tomography) image quality evaluation die body, which belongs to the technical field of CT imaging and comprises an inner die body and an outer die body which are detachable, the cross section of the inner die body is circular, the cross section of the outer die body is elliptical, the inner die body and the outer die body are respectively provided with a plurality of holes, each hole comprises more than one inner diameter, and the inner diameter of each hole is smaller than that of the outer die body. The die body is provided with a hole, sub-cylinders made of different materials are arranged in the hole, the outer diameter of each sub-cylinder is matched with the inner diameter of the hole, the inner diameter of the hole ranges from 5mm to 200mm, and the sub-cylinders are made of but not limited to water, bone, aluminum, titanium and stainless steel. Simulation of artifacts between substances of different sizes and different materials can be achieved by means of the method, the size coverage range is wide, in addition, size selection is conducted on sub-cylinders of different materials according to actual needs, the sizes without practical significance are removed, and the production and test cost can be effectively reduced.

Description

Technical Field

[0001] The utility model belongs to the technical field of CT imaging, in particular to a multi-purpose CT image quality evaluation phantom. Background Art

[0002] Patients requiring computed tomography (CT) imaging often have metallic implants that cause well-known imaging artifacts. When severe, these artifacts not only degrade diagnostic image quality but also complicate the delivery of radiotherapy treatments. In radiotherapy planning, CT images are used to delineate targets and critical organs, define treatment geometry, and assign density for nonuniform dose calculations. For treatment planning, CT imaging artifacts make it difficult for physicians to confidently delineate tumors and surrounding organs and lead to errors in CT numbers (expressed in Hounsfield units [HU]), which can propagate into errors in density assignment and subsequent dose calculations (Chu et al. 2000, Kilby et al. 2002, Papanikolaou et al. 2004).

[0003] Metal artifacts are a major artifact in clinical CT, degrading image quality. They can be caused by beam hardening, photon starvation, or scattering. For conventional CT, various methods are currently available to mitigate beam hardening, including increasing the scanning field voltage. Algorithms, based on iterative algorithms, can be broadly categorized as projection-domain or image-domain interpolation.

[0004] Virtual monoenergetic images from dual-energy CT are another method for reducing metal artifacts. Several dual-energy CT systems currently on the market include Siemens' dual-source dual-detector, Philips' dual-layer detector, and General Electric's (GE) fast-voltage switching models. Numerous studies have shown that each of these three dual-energy CT technologies has its own advantages and disadvantages. Clinically, high-energy virtual monoenergetic images are recommended for metal artifact removal. Current clinical studies of dual-energy CT from all manufacturers have shown that high-energy virtual monoenergetic images are far more effective at removing metal artifacts than low-energy images. In other words, high-energy virtual monoenergetic images are more effective at removing metal artifacts, while low-energy images are not. Utility Model Content

[0005] In order to solve the defects of the existing technology, the utility model provides a multi-purpose CT image quality evaluation phantom, which can simulate artifacts between substances of different sizes and materials with one set of phantoms.

[0006] The present invention adopts the following technical solutions to solve the above problems:

[0007] A multi-purpose CT image quality assessment phantom includes a detachable inner phantom and an outer phantom. Both the inner phantom and the outer phantom are provided with a plurality of holes, each of the holes having more than one inner diameter size. Sub-cylinders made of different materials are provided in the holes, and the outer diameters of the sub-cylinders match the inner diameters of the holes.

[0008] Furthermore, the inner diameter of the hole ranges from 5mm to 200mm.

[0009] Furthermore, the material of the sub-cylinder includes but is not limited to water, bone, aluminum, titanium, and stainless steel.

[0010] Furthermore, the outer diameter of the sub-cylinder made of water ranges from 5 mm to 200 mm.

[0011] Furthermore, the outer diameter of the sub-cylinder made of bone ranges from 20 mm to 35 mm.

[0012] Furthermore, the outer diameter of the sub-cylinder made of aluminum and stainless steel ranges from 5 mm to 35 mm.

[0013] Furthermore, the outer diameter of the sub-cylinder made of titanium ranges from 5 mm to 28.5 mm.

[0014] Furthermore, the cross-sectional shape of the inner mold body is circular, the cross-sectional shape of the outer mold body is elliptical, and both the inner mold body and the outer mold body are equipped with a base for stably placing them.

[0015] The beneficial effects of the present invention are:

[0016] 1. This utility model uses a set of phantoms, combined with sub-cylinders of different sizes and materials, to simulate artifacts between materials of different sizes and materials, achieving a wide range of size coverage. In addition, the sizes of sub-cylinders of different materials can be selected according to actual needs, eliminating sizes that are not practical, which can effectively reduce production and testing costs.

[0017] 2. The design of this utility model also refers to actual clinical applications. The phantom is applied to machines from different manufacturers, which makes it easier to compare the metal artifact removal effects of dual-energy CT from different manufacturers and provide a reference for subsequent research to fundamentally solve the problem that low-energy virtual monoenergetic images cannot effectively remove metal artifacts.

[0018] 3. The phantom provided by this utility model can also be used in the development and research of MAR algorithms for manufacturers' own machines. It is flexible and has wide applicability.

[0019] 4. This utility model provides a multifunctional phantom. If all the embedded cylinders in the phantom are replaced with water, it can be used as an ordinary quality control phantom, with various uses.

[0020] 5. Due to the varying sizes of metals used in clinical practice, we have designed apertures of varying sizes to accommodate metals of varying materials and diameters. These are then embedded in head or abdomen phantoms to assess metal artifacts. This allows for both instrument performance evaluation and MAR algorithm development and validation. In summary, a single phantom can assess metal artifacts of varying materials and sizes, and the materials and sizes are consistent with actual clinical conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention, the following will briefly introduce the drawings required for use in the description of the specific implementation methods. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 This is a schematic structural diagram of the phantom of the utility model;

[0023] Figure 2 Schematic diagram of the phantom of the present invention;

[0024] Figure 3 This is the CT imaging diagram of the phantom of the utility model;

[0025] Figure 4 Virtual monoenergetic images of aluminum head phantoms with different diameters at different energies;

[0026] Figure 5 Virtual monoenergetic images of titanium and stainless steel head phantoms of different diameters at different energies;

[0027] Figure 6 These are virtual monoenergetic images of abdominal phantoms of different diameters and materials at different energies.

[0028] In the figure, 1-inner mold body; 2-outer mold body; 3-hole; 4-sub-cylinder. DETAILED DESCRIPTION

[0029] In the description of the present invention, unless otherwise specified, the terms "upper", "lower", "top", "bottom", "longitudinal", etc. indicate orientations or state relationships based on the orientations or state relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the mechanism or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0030] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meaning of the above terms in the present invention can be understood according to specific circumstances.

[0031] Example 1:

[0032] like Figure 1 As shown, a multi-purpose CT image quality evaluation phantom includes a detachable inner phantom 1 and an outer phantom 2. Both the inner phantom 1 and the outer phantom 2 are provided with multiple holes 3. The holes 3 include more than one inner diameter size. Sub-cylinders 4 of different materials are provided in the holes 3. The outer diameter of the sub-cylinder 4 matches the inner diameter of the hole 3.

[0033] like Figure 2 As shown, the cross-sectional shape of the inner mold body 1 is circular with a cross-sectional diameter of 200 mm, which is used to simulate the size of a human skull; the cross-sectional shape of the outer mold body 2 is a hollow elliptical shape, with an overall major axis dimension of 400 mm and a minor axis dimension of 300 mm, which is used to simulate the cross-sectional structure of a human body; both the inner mold body 1 and the outer mold body 2 are equipped with a base for stable placement, the bottom surface of the base is flat, and the upper surface is provided with grooves that match the inner mold body 1 and the outer mold body 2.

[0034] The inner diameter of the hole 3 ranges from 5 mm to 200 mm. The materials of the sub-cylinders 4 of different sizes include but are not limited to water, bone, aluminum, titanium, and stainless steel. The outer diameter of the sub-cylinder 4 made of bone ranges from 20 mm to 35 mm, the outer diameter of the sub-cylinder 4 made of aluminum and stainless steel ranges from 5 mm to 35 mm, and the outer diameter of the sub-cylinder 4 made of titanium ranges from 5 mm to 28.5 mm. Taking into account the characteristics of the torso and the head, the size of other materials placed on the torso is larger. Therefore, in this embodiment, the inner diameter of the six holes 3 on the outer mold body 2 is 28.5 mm. The inner diameter of the holes 3 on the inner mold body 1 includes 2 holes of 35 mm, 3 holes of 28.5 mm, 4 holes of 20 mm, 2 holes of 10 mm, and 2 holes of 5 mm, totaling 13 holes. The centers of the holes 3 are evenly distributed, and the inner diameter sizes are arranged from large to small from the center to the edge of the inner mold body 1.

[0035] In this embodiment, in order to match the material and number of the sub-cylinders 4, the number of holes 3 is 19, and 19 sub-cylinders 4 are matched one to one. Considering the structure of human bones, small-diameter bone-made cylinders are not designed. Correspondingly, considering the high attenuation of titanium and stainless steel, oversized X-rays cannot penetrate and have no clinical significance. Therefore, large-sized metal-made cylinders are not designed. The outer diameters of the sub-cylinders of various materials are shown in Table 1:

[0036] Table 1 Comparison table of outer diameters of sub-cylinders

[0037]

[0038] The internal phantom was placed in CT machines from Siemens, Philips, and General Electric (GE) for testing. To ensure comparability, the phantom was placed in the absolute center of the machine. Under 80 and 140 kV conditions, dual-energy CT machines from the three major CT manufacturers, Siemens, Philips, and General Electric (GE), were used to scan the phantom we designed. The images are shown in the figure below. Figure 3 As shown in the figure, the results show that there are significant differences in the metal artifact removal effects of virtual monoenergetic images from different manufacturers on the same material. The common point is that the artifact removal effect of low-energy virtual monoenergetic images is significantly poorer, while the high-energy monoenergetic images have relatively better effects.

[0039] Figures 4 to 6 The results were based on the same model (Philips) and compared the effects of removing artifacts from virtual monoenergetic images at different energies.

[0040] like Figure 4 As shown, aluminum sub-cylinders 4 with diameters of 35 mm, 28.5 mm, 20 mm, 10 mm, and 5 mm are placed in the corresponding holes 3 of the inner phantom 1, respectively. The inner phantom 1 is then placed in a CT machine for detection. The window width and window position are all [0, 200], and virtual monoenergetic images are obtained at two different energies of 70 keV and 140 keV.

[0041] like Figure 5 As shown, sub-cylinders 4 made of aluminum and stainless steel with diameters of 10 mm and 5 mm are placed in the corresponding holes 3 of the inner phantom 1, respectively. The inner phantom 1 is then placed in a CT machine for detection. The window width and window position are both [0, 200], and virtual monoenergetic images are obtained at two different energies of 70 keV and 140 keV.

[0042] like Figure 6 As shown, sub-cylinders 4 made of bone, stainless steel, titanium, and aluminum with a diameter of 28.5 mm are placed in the corresponding holes 3 of the outer phantom 2, respectively. The outer phantom 2 is then placed in a CT machine for detection. The window width and window position are all [0, 200], and virtual monoenergetic images are obtained at two different energies of 70 keV and 140 keV.

[0043] Figures 4 to 6The experimental results show that the performance of metal artifacts is closely related to the metal material. The density of aluminum is lower than that of stainless steel and titanium. Therefore, the artifacts caused by aluminum of the same diameter are smaller than those caused by the latter two materials. Secondly, high-energy virtual monoenergetic images are significantly better than low-energy images in removing metal artifacts. When the scanned material is too attenuated or too thick, it will cause photon starvation, and even high-energy monoenergetic images cannot effectively remove artifacts (such as Figure 6 (Scan of the 28.5mm stainless steel and titanium inserts in the image).

[0044] Example 2:

[0045] All sub-cylinders 4 in this mold are made of water, and the outer diameter of the sub-cylinders 4 ranges from 5 mm to 200 mm. Other technical features are the same as those in Example 1.

[0046] In order to match the material and number of the sub-cylinders 4, the number of holes 3 is 19, and 19 one-to-one matched solid water cylinders 4 are equipped. When there is no need to study metal artifacts, it can be used as an ordinary water model. If all the embedded cylinders of the model are replaced with water, it can be used as an ordinary quality control model and can be used for CT machine detection.

[0047] The above examples are used to describe the present invention in detail. However, the above contents are only preferred embodiments of the present invention and should not be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent application of the present invention.

Claims

1. A multi-purpose CT image quality assessment phantom, characterized by: The invention comprises a detachable inner mold body (1) and an outer mold body (2), wherein the inner mold body (1) and the outer mold body (2) are both provided with a plurality of holes (3), wherein the holes (3) have more than one inner diameter size, and sub-cylinders (4) made of different materials are provided in the holes (3), wherein the outer diameter of the sub-cylinders (4) matches the inner diameter of the holes (3).

2. The multi-purpose CT image quality assessment phantom according to claim 1, characterized in that: The inner diameter of the hole (3) ranges from 5 mm to 200 mm.

3. The multi-purpose CT image quality assessment phantom according to claim 1, characterized in that: The material of the sub-cylinder (4) includes water, bone, aluminum, titanium, and stainless steel.

4. The multi-purpose CT image quality assessment phantom according to claim 3, characterized in that: The outer diameter of the sub-cylinder (4) made of water is in the range of 5 mm to 200 mm.

5. The multi-purpose CT image quality assessment phantom according to claim 3, characterized in that: The outer diameter of the sub-cylinder (4) made of bone is in the range of 20mm-35mm.

6. The multi-purpose CT image quality assessment phantom according to claim 3, characterized in that: The outer diameter of the sub-cylinder (4) made of aluminum or stainless steel ranges from 5 mm to 35 mm.

7. The multi-purpose CT image quality assessment phantom according to claim 3, characterized in that: The outer diameter of the sub-cylinder (4) made of titanium is in the range of 5 mm to 28.5 mm.

8. The multi-purpose CT image quality assessment phantom according to any one of claims 1 to 7, characterized in that: The cross-sectional shape of the inner mold body (1) is circular, and the cross-sectional shape of the outer mold body (2) is elliptical. Both the inner mold body (1) and the outer mold body (2) are equipped with a base for stably placing them.

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