Test object for analyzing and monitoring MR tomograph image quality

Abstract

The invention relates to a phantom for simple calibration and quality assurance in MR tomographs, having a phantom body (2), measurement aids (10, 11, 12, 13) and an intermediate base (14) having an upper side and a lower side, wherein the measurement aids (10, 11, 12, 13) and the intermediate base (14) are arranged in at least four planes (6, 7, 8, 9) in the phantom body (2), a first plane (6) comprising only a measurement liquid (10) as the measurement aid, a second plane (7) comprising a wedge element (11) as the measurement aid, a third plane (8) comprising markings (12) at a known distance from one another as the measurement aid, a fourth plane (9) comprising a comb element (13) as the measurement aid, the measurement aid (11) of the second plane (7) being arranged on one side of the intermediate base (14), the measurement aid (13) of the fourth plane (9) being arranged on the other side of the intermediate base (14), the measurement aid (12) of the third plane (8) being arranged within the intermediate base (14). By virtue of the arrangement of the measurement aids according to the invention, reliable calibration of an MR tomograph in a few steps is possible with the phantom according to the invention.

Description

Technical Field

[0001] This invention relates to a novel test subject, namely a phantom, for calibration, image quality analysis and / or quality assurance in magnetic resonance computed tomography (MRI) scanners. Background Technology

[0002] Magnetic resonance imaging (MRI), also known as nuclear spin computed tomography, is an imaging method used in medical diagnostics. Based on the physical effects of nuclear magnetic resonance, this method allows for three-dimensional visualization of body structures, including tissues. Three-dimensional visualization is achieved by combining multiple virtual cross-sectional images of the body region to be examined.

[0003] In short, to make different tissues visible, and thus to visualize different body structures and organs, MRI ultimately utilizes the fact that certain atomic nuclei, particularly the nuclei of hydrogen atoms, are magnetic and magnetizable due to their inherent rotation (so-called nuclear spin). By applying a high-frequency alternating field, these nuclei, once magnetized, can be "tilted" out of their static equilibrium state. These tilted nuclei then induce a measurable electric current. Once the high-frequency alternating field is removed, the tilted nuclei tend to return to their static equilibrium state, a process known as relaxation. The contrast required for visualizing different structures and tissues is based on the fact that different tissues have different relaxation times.

[0004] Magnetic resonance imaging (MRI) scanners are highly complex instruments used to perform MRI. The resulting images must depict the actual anatomy of the subject as accurately as possible. In particular, artifacts arising from technical reasons during data generation and imaging must be avoided at all costs, as they can lead to misdiagnosis and therefore mistreatment.

[0005] To minimize the risk of such artifacts due to technical reasons, MR tomography scanners must be regularly maintained and selectively calibrated. Currently, the most important standard for this calibration method is IEC 62464-1, which defines essential image quality parameters.

[0006] The six parameters to be determined according to this standard include signal-to-noise ratio, uniformity, layer thickness, ghosting artifacts, geometric distortion, and spatial resolution.

[0007] To test and selectively calibrate these parameters, a test subject, known as a phantom, is introduced into the MR tomography scanner. Such phantoms are known in the prior art.

[0008] Known phantoms typically consist of a hollow cylindrical base body filled with liquid and equipped with multiple measuring aids.

[0009] Known measurement aids include

[0010] - The measurement solution, defined by parameters T1 (longitudinal relaxation time), T2 (lateral relaxation time), and proton density, is used to determine or calibrate parameters, particularly signal-to-noise ratio, uniformity, and ghost artifacts;

[0011] - Wedge-shaped elements are used to determine or calibrate parameters, particularly layer thickness;

[0012] - Markers indicating known distances between each other are used to determine or calibrate the parameter, particularly geometric distortion;

[0013] - Comb elements are used to determine or calibrate parameters, particularly spatial resolution.

[0014] A drawback of existing technologies is that multiple (i.e., up to six) different phantoms are typically required to adequately determine or calibrate the image quality parameters required by the standard. However, for a number of reasons, using as few phantoms as possible is preferable.

[0015] First, compared to multiple mannequins, ideally purchasing and storing only one mannequin can save costs.

[0016] Secondly, for efficiency reasons, because every step that can be saved in calibration reduces the required working time.

[0017] Of course, for reliability reasons, this is especially important because every step that can be saved in calibration also helps reduce the error rate. Simple determination and calibration of basic image quality parameters leads to fewer errors in the process, resulting in more accurate imaging, diagnosis, and ultimately, better treatment.

[0018] By providing phantoms that are simpler to use and allow for the determination and / or calibration of basic image quality parameters in a time-saving manner, costs can be saved and operational errors and working time reduced, thereby increasing the operating time of MR tomography scanners. Ultimately, the reliability of MR tomography scanners is also improved, and the potential usability of MR tomography scanners is increased.

[0019] Another drawback of existing technology is that known phantoms consist of multiple individual parts, the assembly and calibration of which are complex, costly, time-consuming, and prone to errors during assembly and production.

[0020] Known phantoms allow for the simultaneous determination and / or calibration of multiple parameters, and are typically provided in modular form with corresponding measurement aids, each housed within its own module. Therefore, such known phantoms comprise a specific number of modules, each of which must be manufactured individually, a time-consuming and labor-intensive process that is costly and prone to errors.

[0021] Of particular importance is the correct orientation and placement of the phantom within the MR tomography scanner, a fundamental requirement for successfully determining and / or calibrating essential image quality parameters. Known phantoms correspondingly provide adapters, which are generally universally applicable to different systems. However, such universal adapters typically suffer from the drawback that they fail to provide the ultimately necessary accuracy. This is a compromise that this solution must accept in terms of its universality. Summary of the Invention

[0022] Therefore, one object of the present invention is to provide a phantom that allows basic image parameters to be determined and / or calibrated in a single phantom with as few steps as possible that are easy to perform.

[0023] An additional object of the present invention is to provide a mannequin comprising as few individual components as possible, thereby reducing its cost and minimizing the likelihood of assembly errors even during production.

[0024] Another object of the present invention is to provide a measurement and evaluation method that is easy to use, allows for optimal determination and / or calibration of basic image quality parameters, and is error-proof.

[0025] This objective is achieved by a device according to the invention having the features of claim 1. Advantageous embodiments are the subject of the dependent claims. It should be noted that the features individually mentioned in the claims can also be combined with each other in any desired and technically advantageous manner, thereby demonstrating further embodiments of the invention.

[0026] The phantom according to the invention comprises a phantom body having measuring aids disposed therein. The phantom body is preferably made of a material that allows for rapid visual inspection of material damage to the body and measuring aids. Suitable materials are, for example, acrylic glass. The phantom body preferably comprises a hollow cylindrical base element, with a top plate and a bottom plate respectively disposed at the upper and lower ends of the hollow cylindrical base element, the top plate and bottom plate being at least fluid-tightly sealed to the base element.

[0027] The dimensions of the phantom preferably correspond to relevant specifications, such as IEC 62464-1, which requires, in principle, both low weight and high stability. The dimensions of the phantom body must, of course, be chosen to allow for space within the phantom body for the provision of measurement aids.

[0028] The measurement aids will be placed within the phantom body, so that the phantom only needs to be introduced into the MR tomography scanner once for each axis to be measured. This is advantageous because introducing the phantom body only once for each axis to be measured saves time and minimizes sources of error. Therefore, the time required for determining and / or calibrating basic image quality parameters can be reduced to almost the scan time alone.

[0029] For this purpose, various measuring aids are arranged in multiple separate planes, wherein these planes are preferably arranged within the phantom body parallel to the top plate and the bottom plate.

[0030] The term “plane” should be understood in the context as the longitudinal portion of the phantom body, wherein the phantom body itself is not understood as part of the plane and each plane essentially comprises only one measuring aid.

[0031] The phantom body is filled with a saline solution as the measuring fluid, which, due to its specific composition, simulates the electrical properties of muscle tissue. Preferred saline solutions particularly include copper sulfate and sodium chloride. This solution can be designed for different field strengths, such as 1.5T for MR tomography.

[0032] To introduce, drain, or exchange the measuring fluid, appropriate supply and / or drainage lines can be provided on the phantom body, and particularly on the top plate and / or bottom plate of the phantom body. Suitable valve elements can be installed on these supply and / or drainage lines.

[0033] The phantom according to the invention also includes a central bottom having an upper side and a lower side, on or inside which are arranged all fixed measuring aids, i.e., all fixed measuring aids that are not measuring fluids. These are wedge-shaped elements for determining or calibrating, in particular, the parameter of layer thickness; markers with known distances between them for determining or calibrating, in particular, the parameter of geometric distortion; and comb-shaped elements for determining or calibrating, in particular, the parameter of spatial resolution.

[0034] According to the invention, wedge-shaped elements are disposed on one side of the intermediate bottom, and comb-shaped elements are disposed on the other side of the intermediate bottom. Markers indicating known distances between them are disposed within the intermediate bottom, particularly in the form of holes perpendicular to the plane of the intermediate bottom.

[0035] The middle bottom is arranged inside the main body of the phantom, preferably parallel to the top and bottom plates. In particular, the middle bottom with measuring aids is additionally arranged inside the main body of the phantom, such that at least in one plane of the phantom, there is only measuring fluid and no fixed measuring aids.

[0036] Based on the above definition of a plane, the phantom according to the present invention correspondingly includes a phantom body having at least four planes.

[0037] The first plane includes a defined measurement solution, wherein, in particular, the parameters T1 (longitudinal relaxation time), T2 (lateral relaxation time), and proton density are known. The measurement solution is preferably a salt solution containing copper sulfate and sodium chloride, which must be adapted to the specific field strength of the test environment. This first plane is specifically used to determine or calibrate the signal-to-noise ratio, uniformity, and ghosting artifacts.

[0038] The second plane includes wedge-shaped elements for determining or calibrating the layer thickness. Preferably, the wedge-shaped elements are arranged in pairs, wherein the individual wedges in a pair are arranged parallel to each other in all cases, and the tip of one wedge points towards the base of the other wedge, and vice versa. If two or more pairs of wedge-shaped elements are provided, at least two of these pairs are arranged perpendicular to each other.

[0039] The third plane includes markers at known distances from each other, used to determine or calibrate geometric distortion. The markers are preferably provided as holes, particularly holes within or through the middle bottom.

[0040] The fourth plane includes at least two comb elements for determining or calibrating spatial resolution. Each comb element essentially comprises a base with fins vertically erected on the base and oriented parallel to each other. The at least two comb elements are oriented relative to each other such that the fins of the two elements are perpendicular to each other.

[0041] According to the invention, the measuring aids for the second, third, and fourth planes, as described above, are arranged above or in the middle of the intermediate bottom, or connected to the intermediate bottom. Therefore, the third plane substantially corresponds to the intermediate bottom, which has markings with known distances between them.

[0042] All surfaces, including fixed measuring aids, are of course filled with the measuring fluid.

[0043] In a particularly preferred embodiment, the phantom comprises exactly four planes, wherein the first plane comprises only a measuring liquid of known density (preferably a salt solution containing copper sulfate and sodium chloride) as a measuring aid for determining or calibrating the signal-to-noise ratio, uniformity, and ghost artifacts.

[0044] Besides the measuring liquid, the second plane includes only wedge-shaped elements for determining or calibrating the layer thickness. Preferably, the wedge-shaped elements are arranged in pairs, wherein the individual wedges in a pair are arranged parallel to each other in all cases, and the tip of one wedge points towards the base of the other wedge, and vice versa. Preferably, two pairs of wedge-shaped elements are provided that are arranged perpendicular to each other.

[0045] In addition to the measuring fluid, the third plane consists only of a central bottom with markers at known distances from each other, used for determining or calibrating geometric distortion. The markers are set to pass through holes in the central bottom.

[0046] Besides the measuring fluid, the fourth plane comprises only comb elements for determining or calibrating spatial resolution. Each comb element essentially comprises a base having fins that are vertically erected on the base and oriented parallel to each other. Preferably, two comb elements are oriented relative to each other such that the fins of the two elements are perpendicular to each other.

[0047] Similarly, in this embodiment, all planes, including the fixed measuring aids, are also filled with the measuring fluid.

[0048] Furthermore, the phantom according to the invention preferably includes a support that is specifically adapted for use with the MR tomography scanner employing the phantom. This separately adapted support is advantageous because it saves the user from the time-consuming and error-prone task of phantom positioning and alignment. Instead, the separately adapted support not only ensures rapid and error-free phantom positioning and alignment but also ensures the reproducibility of measurements. Attached Figure Description

[0049] In the attached diagram:

[0050] Figure 1 This is a side view of the phantom according to the present invention;

[0051] Figure 2 This is a perspective view of the wedge-shaped measuring elements, below which is a schematic top view of the arrangement of these elements in a plane;

[0052] Figure 3 It is a perspective view of the third plane with distance markers, below which is a schematic top view of the arrangement of the markers in the plane;

[0053] Figure 4 It is a perspective view of the fourth plane with comb-shaped measuring elements, below which is a schematic top view of the arrangement of these elements in the plane;

[0054] Figure 5 This is a perspective view of the support structure, below which is the arrangement of the phantom with the support structure inside the tube of the MR tomography scanner. Detailed Implementation

[0055] The invention and technical background will now be explained in more detail with reference to the accompanying drawings. It should be noted that the drawings illustrate particularly preferred embodiments of the invention. However, the invention is not limited to the illustrated embodiments. In particular, where technically advantageous, the invention includes any desired combination of technical features related to the invention, as mentioned in the claims or described in the specification.

[0056] Figure 1 A phantom 1 according to the present invention is shown. The phantom 1 has a phantom body 2, measuring aids 10, 11, 12, 13, and a central bottom 14. The phantom body 2 includes a hollow cylindrical base body 3, a top plate 4, and a bottom plate 5, the top plate 4 and the bottom plate 5 being arranged at both ends of the hollow cylindrical base body 3. The top plate 4 and the bottom plate 5 are parallel to each other and perpendicular to the longitudinal central axis of the hollow cylindrical base body 3.

[0057] The top plate 4 and the bottom plate 5 at least liquid-tightly seal the hollow cylindrical base body 3. The hollow cylindrical base body 3 is preferably made of an optically transparent material, such as acrylic glass, so that damage to the phantom 1 is visually perceptible.

[0058] The measuring aids 10, 11, 12, 13 and the intermediate bottom 14 are arranged inside the phantom body 2. The measuring fluid 10 almost completely fills the phantom body 2. The other measuring aids 11, 12, 13 are arranged on or within the intermediate bottom 14.

[0059] In general, the measuring aids are arranged in four planes 6, 7, 8, and 9, which are arranged parallel to each other along the central longitudinal axis of the phantom body. The measuring fluid 10 penetrates all four planes 6, 7, 8, and 9.

[0060] The first plane 6 includes only the measuring liquid 10 as a measuring aid. The second plane 7 includes a wedge-shaped element 11 as a measuring aid. The third plane 8 includes a mark 12 as a measuring aid, preferably disposed in or above the intermediate bottom 14. The fourth plane 9 includes a comb-shaped element 13 as a measuring aid. According to the invention, the wedge-shaped element 11, the mark 12, and the comb-shaped element 13 are disposed in or above the intermediate bottom 14.

[0061] To allow for the replacement of the measuring fluid 10, openings 15 may be optionally provided in the top plate 4 and / or the bottom plate 5 through which the measuring fluid 10 can be supplied or discharged. Optionally, valve elements 16 may be provided at these points to increase the airtightness of the phantom 1.

[0062] Figure 2The wedge-shaped elements 11 of the second plane 7 are shown in detail. Preferably, the wedge-shaped elements 11, arranged in pairs and of the same size, comprise a first wedge-shaped element 11A and a second wedge-shaped element 11B. The individual wedges 11A and 11B of a pair of wedge-shaped elements 11 are arranged parallel to each other in all cases, wherein the tip of one wedge 11A points towards the base of the other wedge 11B, and vice versa. In particular, the tip of one wedge 11A terminates at the base of the other wedge 11B, and vice versa. If two pairs of wedge-shaped elements 11 are provided, they are preferably arranged perpendicular to each other. The wedge-shaped elements 11 are used for determining or calibrating layer thickness.

[0063] Figure 3 A third plane 8 is shown in detail, having a central bottom 14 and markings 12 arranged on it. Preferably, the markings 12 are configured as vertical holes passing through the central bottom 14. The markings 12, spaced at known distances from each other, are used for determining or calibrating geometric distortion. Figure 3 The distribution patterns of these markers 12 shown as examples can be applied to the specification requirements of specific situations.

[0064] Figure 4 The comb element 13 of the fourth plane 9 is shown in detail, and a preferred arrangement is illustrated in the plan view. The comb element 13 includes a base 13A and fins 13B arranged vertically on the base and oriented parallel to each other. The comb element 13 is used to determine or calibrate spatial resolution. If two comb elements 13 are provided in the fourth plane 9, they are oriented relative to each other such that the fins 13B of the two elements 13 are arranged perpendicular to each other.

[0065] Figure 5 A schematic diagram of the support 17 for holding the phantom 1 is shown. Besides ensuring the phantom 1 is securely held, the support 17 also ensures the reproducibility of the maintenance work to be performed. In particular, the assembly accuracy of the support 17 must be ensured so that for each new maintenance operation to be performed, i.e., the calibration or determination of basic image quality parameters, the phantom 1 will be positioned in the MR tomography scanner in exactly the same location as the previous maintenance operation.

[0066] Reference list of numbers

[0067] 1. Phantom

[0068] 2. Main body of the phantom

[0069] 3. Base components

[0070] 4. Top plate

[0071] 5. Base plate

[0072] 6 First plane

[0073] 7 Second plane

[0074] 8 Third plane

[0075] 9. Fourth plane

[0076] 10 Measuring liquid

[0077] 11. Wedge-shaped elements (A and B, separate wedges)

[0078] 12 Marks

[0079] 13 Comb-shaped elements (13A base, 13B fins)

[0080] 14 Middle bottom

[0081] 15. Supply or discharge pipelines

[0082] 16 Valve Components

[0083] 17. Bracket

Claims

1. A phantom for an MR tomograph, having a phantom main body, a measurement aid and an intermediate base with an upper side and a lower side, wherein, The measuring aids and the intermediate bottom are arranged in at least four planes in the phantom body, wherein - a first plane comprises only a measuring liquid as the measuring aid; - a second plane comprises a wedge element as the measuring aid; - a third plane comprises markings at a known distance from one another as the measuring aid; and - a fourth plane comprises a comb element as the measuring aid, characterized in that the measuring aids of the second plane are arranged on one side of the intermediate bottom, the measuring aids of the fourth plane are arranged on the other side of the intermediate bottom, and the measuring aids of the third plane are arranged within the intermediate bottom. The phantom body comprises a hollow-cylindrical base element, the upper and lower ends of which are closed by at least a top plate and a bottom plate.

2. A phantom according to claim 1, wherein, The intermediate bottom is arranged parallel to the top plate and the bottom plate.

3. A phantom according to claim 2, wherein, The wedge elements of the second plane provided as the measuring aid are arranged in pairs, wherein the individual wedges in a pair are arranged parallel to one another in each case, and the tip of one wedge points towards the base of the other wedge, and vice versa.

4. A phantom according to any one of claims 1-3, characterized in that The markings of the third plane provided as the measuring aid are provided as holes in the intermediate bottom.

5. A phantom according to any one of claims 1-3, characterized in that The comb elements comprise a base and fins which are vertically upright on the base and are oriented parallel to one another, and at least two of the comb elements of the fourth plane are oriented relative to one another as measuring aids such that the fins of the two comb elements are oriented perpendicular to one another.

6. A phantom according to any one of claims 1-3, characterized in that The measuring liquid comprises a salt solution comprising copper sulfate and sodium chloride.

7. A phantom according to any one of claims 1-3, characterized in that The phantom body is made of acrylic glass.

8. A phantom according to any one of claims 1-3, characterized in that A supply and / or discharge line for the measuring liquid is provided on the phantom body.

9. A phantom according to any one of claims 1-3, characterized in that A supply and / or discharge line for the measuring liquid is provided on the top plate and / or the bottom plate.

10. A phantom according to claim 2 or 3, wherein, A valve element is provided on the supply and / or discharge line.

11. A phantom according to claim 9, wherein, The phantom comprises a stand which is individually suitable for MR tomographs.

12. A phantom according to any one of claims 1-3 and 11, characterized in that ​

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