A performance testing phantom and image quality evaluation method for medical magnetic resonance imaging equipment

Abstract

The present invention relates to a performance detection phantom for medical magnetic resonance imaging equipment and an image quality evaluation method, which is a stack of multiple layers of performance detection modules inside a regular cylindrical hollow tube, wherein each module is independent of each other, and a layer thickness module, an image uniformity module, a high contrast resolution module, a low contrast resolution module, and a geometric distortion module are sequentially arranged from top to bottom. The image uniformity module is a uniform water layer between the layer thickness module and the high contrast resolution module, and the geometric distortion module is a grid structure. The image quality evaluation method using the above-mentioned detection phantom includes layer thickness, image uniformity and signal-to-noise ratio, low contrast resolution, and geometric distortion evaluation. The present invention can automatically detect the image of the phantom, and the measurement is simple and the detection is completed quickly. The operation of calibrating and tracing the phantom is simple and fast, and the restoration to the original state is accurate, thereby making the image quality evaluation of the detection phantom rapid and accurate, and more suitable for practical use.

Description

Technical Field

[0001] The present invention relates to a performance detection phantom and an image quality evaluation method for medical magnetic resonance quality in the field of medical machinery, and in particular to a performance detection phantom and an image quality evaluation method for medical magnetic resonance imaging equipment. Background Art

[0002] Medical Magnetic Resonance Imaging (MRI) equipment uses the magnetic resonance signals generated by the Larmor motion of hydrogen nuclei in water molecules in the human body, which are excited by an external radiofrequency field, to reconstruct images. This allows for multi-parameter, multi-planar imaging, providing not only morphological and structural information but also functional information such as biochemistry and perfusion, with superior soft tissue contrast. As a powerful non-invasive imaging method in oncology, MRI has become a mature and widely used imaging method, widely used in clinical medicine and medical research.

[0003] However, after MRI equipment is installed and put into use, factors such as magnet aging and improper routine maintenance can lead to a decline in imaging quality. This can cause problems such as inconsistent grayscales within the same tissue, inability to accurately identify small lesions, lesion image distortion, and noise artifacts. These can mislead imaging technicians in clinical diagnosis and, if quality control is not performed promptly, can even lead to medical accidents. To better realize the superior performance of MRI equipment and reduce equipment operation risks, imaging system quality control and management are essential.

[0004] Research on MRI quality control began internationally in the 1980s and 1990s. The American Association of Physicists in Medicine (AAPM) published the following test standards: AAPM Report No. 28: Quality Assurance Methods and Phantoms for Magnetic Resonance Imaging, AAPM Report No. 34: Acceptance Testing of Magnetic Resonance Imaging Systems, and AAPM Report No. 100: Acceptance Testing and Quality Assurance Procedures for Magnetic Resonance Imaging Facilities. These standards recommended acceptance and quality control methods and corresponding indicators for MRI equipment and analyzed factors influencing image quality parameters. The National Electrical Manufacturers Association (NEMA) published the MS series of standards, which defined a set of key MRI parameters, provided measurement methods for these parameters, and outlined error correction methods for some parameters. The International Electrotechnical Commission (IEC) published IEC 60601-2-33, which outlines basic safety and performance requirements for medical MRI equipment. The American College of Radiology (ACR), referencing NEMA standards and the AAPM report, recommended the ACR phantom and published reports and white papers such as the Phantom Test Guidance for the ACR MRI Accreditation Program and the 2015 ACR Magnetic Resonance Imaging Quality Control Manual for MR device performance evaluation. Compared to the rapid development of MRI technology, research in MRI device performance and image quality evaluation methods by domestic research institutions has lagged behind. Current domestic standards, such as the health industry standard WS / T 263-2006, Image Quality Testing and Evaluation Specifications for Medical Magnetic Resonance Imaging (MRI) Equipment, the industry standard YY / T 0482-2004, Technical Requirements and Test Methods for Magnetic Resonance Equipment for Medical Diagnosis, and the Verification Procedures for Medical Magnetic Resonance Imaging Equipment, all reference relevant AAPM and NEMA standards.

[0005] To meet the requirements for accurate quality assessment of medical MRIs, performance testing phantoms have emerged. They are now widely used for quality control and measurement of parameters such as signal-to-noise ratio, image uniformity, geometric distortion, high-contrast resolution, low-contrast resolution, and slice thickness. Currently, the two most popular phantoms in use both domestically and internationally are the Magphan SMR series phantoms produced by American Phantom Laboratories and the ACR phantom developed by the American College of Radiology. While these two phantoms can measure most key parameters, their relatively simple design and limited internal materials make them unable to meet the increasing testing needs brought about by the rapid development of MRI technology.

[0006] Magphan SMR series phantoms are mainly divided into SMR100 and SMR170 phantoms. The shell of SMR100 consists of two acrylic hemispheres with an inner diameter of 200mm; the shell of SMR170 phantom is a cylinder with an outer diameter of 200mm, an inner diameter of 190mm, and a wall thickness of 5mm. The interior of both phantoms is an acrylic test cube with a side length of 100mm. The cube is made of a slice thickness bevel, a high contrast resolution test plate and a low contrast resolution test plate (such as Figure 1 As shown in the figure), it can measure parameters such as layer thickness accuracy, geometric distortion, high contrast resolution, low contrast resolution, and image uniformity, but it also has many shortcomings:

[0007] 1. The layer thickness measurement slope in the Magphan phantom is designed with a simple principle and does not comply with NEMA standards. It cannot correct the layer thickness measurement error caused by the tilted placement of the phantom, resulting in a large actual measurement error.

[0008] 2. The geometric distortion module consists of two acrylic half-discs, which are inserted between the second and third layer thickness measurement slopes to fix the central test cube. There are 20 through-holes on the discs. Geometric distortion is detected by calculating the difference between the measured value and the nominal value of the hole spacing on the MRI image. However, the diameter of the small holes (3mm) is large. If the center of the circle cannot be accurately located, it will cause a large error. In addition, the position and distance of the small holes are fixed, and only geometric distortion at a fixed position and distance can be detected. Furthermore, gaps and height differences may occur after the two half-discs are spliced, resulting in inaccurate nominal values.

[0009] 3. The 11 line-pair groups in the high-contrast resolution module are distributed in an L-shape. During a single imaging session, only the high-contrast resolution performance at the edge of the MRI area can be detected, but not in the central imaging area.

[0010] 4. There are only 12 low-contrast circular spots in the low-contrast resolution module, and the etching depth is relatively deep, with the shallowest etching depth being 0.5mm. As a result, all currently used medical MRI devices can clearly distinguish all low-contrast circular spots, and it is impossible to effectively distinguish the low-contrast resolution of MRI devices of different grades.

[0011] 5. All modules are between 2 and 3 mm thick. Continuous scanning is not possible during MRI equipment performance testing. Instead, a layered scan is required, requiring each module to be scanned individually. This process is time-consuming for MRI equipment currently in use in hospitals, and prolonged machine occupancy can seriously delay clinical diagnosis.

[0012] 6. As a quality control tool for magnetic resonance imaging, the accuracy of the phantom's measurement is very important. However, due to processing errors, long-term solution immersion and other factors, the actual size of the phantom may not match the nominal size. Therefore, the phantom needs to be calibrated and traced. According to the nominal size of each module of the phantom, high-precision optical projectors and grating micrometers are needed to measure the size of the phantom during traceability. However, all modules of the Magphan phantom are fixed to the central test cube with plastic screws. When using optical projectors and grating micrometers for traceability, they must be disassembled. Due to the small thickness of each module, the disassembly process can easily cause damage to the module. In addition, the phantom needs to be reassembled after calibration. The assembly process will inevitably cause assembly deviation, resulting in a certain amount of deviation between the size of the restored phantom and the initial state phantom.

[0013] The ACR phantom is a hollow acrylic cylinder with a length of 148 mm, an inner diameter of 190 mm, and closed ends. The thickness of each module of the ACR phantom meets the requirements for continuous scanning, effectively reducing testing time. However, the phantom also has the following drawbacks:

[0014] 1. The slice thickness module calculates slice thickness by measuring the length of the high-signal area within two 1mm grooves with opposite slopes. Although this can be used to correct for errors caused by tilted phantom placement, the presence of groove width also introduces a certain degree of error in slice thickness measurement. The larger the groove width, the greater the error. If the groove width is too small, the actual groove signal strength will be too low, making measurement more difficult.

[0015] 2. The high-contrast resolution module uses a dot matrix with different apertures for measurement, similar to the principle of the Magphan phantom. However, the ACR phantom's high-contrast resolution module only has three sets of dot matrices with different apertures, which cannot accurately test the high-contrast resolution performance of MRI equipment.

[0016] 3. Because the magnetic field is most uniform at the center of the MRI device, when an MRI scan is performed on a person, the person is positioned at the center of the device. However, the low-contrast resolution module of the ACR phantom is not positioned at the center of the device, which does not reflect the optimal performance of the MRI device.

[0017] 4. The ACR phantom utilizes a closed design. Since the solution cannot be changed, the release of dissolved oxygen can lead to an increase in bubbles within the phantom, severely impacting MRI evaluation results. Furthermore, the closed design makes the phantom untraceable, and the accuracy of its measurements cannot be guaranteed.

[0018] After acquiring image data from an MRI device using a performance test phantom, image quality evaluation is necessary. Currently, MRI image quality evaluation primarily relies on visual inspection. However, traditional subjective manual inspection relies heavily on the tester's expertise and experience, resulting in low accuracy and poor repeatability, and failing to accurately reflect device performance. With the increasing maturity of medical imaging applications, objectivity in image quality evaluation is gaining increasing attention. Researching programmatic evaluation methods based on phantom-based objective image quality assessment will be an inevitable trend in establishing an objective image quality evaluation system for medical MRI systems.

[0019] In view of the above-mentioned shortcomings of the existing medical MRI quality performance testing phantom and image quality evaluation method, the inventors have repeatedly tried to make samples and make improvements, and finally created the present invention which has real practical value. Summary of the Invention

[0020] The purpose of the present invention is to overcome the defects of existing medical magnetic resonance quality performance detection phantoms and provide a new structure of a medical magnetic resonance imaging equipment performance detection phantom and image quality evaluation method. The technical problem to be solved is to make its measurement accuracy high so that it is more suitable for practical use.

[0021] Another object of the present invention is to overcome the defects of existing medical magnetic resonance quality performance detection phantoms and image quality evaluation methods, and to provide a new medical magnetic resonance imaging equipment performance detection phantom and image quality evaluation method. The technical problem to be solved is to make the measurement simple and the detection completed quickly, thereby making it more suitable for practical use.

[0022] Another object of the present invention is to provide a new medical magnetic resonance imaging equipment performance detection phantom and image quality evaluation method. The technical problem to be solved is to make the phantom calibration and traceability simple and fast, and to restore the original state accurately, so that it is more suitable for practical use.

[0023] Another object of the present invention is to provide an image quality evaluation method for a medical magnetic resonance imaging equipment performance detection phantom. The technical problem to be solved is to enable the image quality evaluation of the detection phantom to be automated, thereby making the image quality evaluation of the detection phantom rapid and accurate, more suitable for practical use, and having industrial utilization value.

[0024] The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. According to the present invention, a medical magnetic resonance imaging equipment performance detection phantom is a right cylindrical tube-type sealed structure, comprising: a right cylindrical hollow tube, an upper top cover and a multi-layer performance detection module, the upper top cover is fixed on the top of the right cylindrical hollow tube, and the inner part of the right cylindrical hollow tube is stacked with multiple layers of performance detection modules, each module is independent of each other, and is sequentially arranged from top to bottom with a layer thickness module, an image uniformity module, a high contrast resolution module, a low contrast resolution module and a geometric distortion module, wherein the layer thickness module, the high contrast resolution module and the low contrast resolution module are all disc structures; the image uniformity module is a uniform water layer between the layer thickness module and the high contrast resolution module; the geometric distortion module is a grid structure, and the geometric distortion module is fixed on the lower bottom inside the right cylindrical hollow tube;

[0025] The upper cover and each module are provided with 4 assembly holes for connecting to other modules, and the distance between the centers of the 4 assembly holes is equal and forms a square;

[0026] The modules are connected by four acrylic rods and sleeves of different lengths. The acrylic rods pass through the assembly holes and are matched with the sleeves to support the modules and control the distance between the modules.

[0027] Furthermore, the four layer thickness module upper surface assembly holes provided on the upper surface of the layer thickness module 2 and the assembly holes on the lower surface of the upper top cover correspond one to one in the vertical direction, and are evenly distributed on the layer thickness module and the upper top cover in a square distribution; the four layer thickness module lower surface assembly holes provided on the lower surface of the layer thickness module, the four high contrast resolution module assembly holes provided on the high contrast resolution module, the four low contrast resolution module assembly holes provided on the low contrast resolution module, and the four lower bottom assembly holes provided on the lower bottom surface correspond one to one in the vertical direction, and are evenly distributed on the lower surface of the layer thickness module, the high contrast resolution module, the low contrast resolution module, and the lower bottom surface, respectively;

[0028] The four assembly holes on the lower surface of the layer thickness module, the four assembly holes for the high-contrast resolution module, the four assembly holes for the low-contrast resolution module, and the four assembly holes on the upper surface of the lower base are respectively located on the midlines of the four connecting lines between the centers of the assembly holes on the upper surface of the four layer thickness modules, that is, the four assembly holes on the lower surface of the layer thickness module, the four assembly holes for the high-contrast resolution module, the four assembly holes for the low-contrast resolution module, and the four assembly holes on the upper surface of the lower base are rotated 45° relative to the assembly holes on the upper surface of the four layer thickness modules and are distributed in a square.

[0029] Furthermore, the upper cover and the layer thickness module are connected through four first sleeves, the layer thickness module and the high contrast resolution module are connected through four second sleeves, the high contrast resolution module and the low contrast resolution module 4 are connected through four third sleeves, and the low contrast resolution module and the lower bottom are connected through four fourth sleeves.

[0030] Furthermore, the high-contrast resolution module and the low-contrast resolution module are provided with positioning holes, and the layer thickness module 2 and the image uniformity module are provided with 4 positioning rods. The positions of the positioning holes or positioning rods correspond one to one up and down. The 4 positioning holes and 4 positioning rods are arranged at the upper left corner, upper right corner, lower left corner and lower right corner of the edge of each module. The overall distribution is rectangular and the center of the rectangle is the center of each module.

[0031] Furthermore, the layer thickness module is composed of a group of cross-placed wedge blocks and a disc-shaped substrate. The wedge blocks are fixed on the substrate, and the long sides of the two wedge blocks are relatively close and in the same line as the diameter of the substrate. Four positioning rods are fixed on the substrate, wherein the positioning rods extend to a height of 20 mm on the upper surface of the layer thickness module 2, and extend to a height of 20 mm on the lower surface of the positioning rods. The upper surface assembly holes of the layer thickness module and the lower surface assembly holes of the upper cover 1 correspond one to one, and are connected by a 30 mm first sleeve. The lower surface assembly holes of the layer thickness module and the high contrast resolution module assembly holes correspond one to one, and are connected by a 25 mm second sleeve.

[0032] Furthermore, the high contrast resolution module is a disk with 24 hollowed-out line pairs. Each line pair group consists of 3 to 5 rectangular through holes, and all line pairs have the same length.

[0033] Within each wire pair group, the width of the rectangular through-hole is the same as the distance between two adjacent rectangular through-holes. There are 12 wire pair groups with different widths, and each width has 2 wire pair groups, totaling 24 wire pair groups. The 24 wire pair groups are arranged in two ways, 12 of which are distributed in an L-shape at the edge of the module, and the other 12 are distributed in the center area of ​​the module.

[0034] The high contrast resolution module assembly hole is connected to the lower surface assembly hole of the layer thickness module through a 25mm second sleeve at the top, and is connected to the low contrast resolution module assembly hole through a 17.5mm third sleeve below the high contrast resolution module assembly hole.

[0035] Furthermore, the low-contrast resolution module is a disk, and four groups of grooves of different depths are etched on the upper surface of the low-contrast resolution module, each groove group includes grooves of four different diameters, with three grooves of each diameter, totaling 12 grooves, and the four groove groups totaling 48 grooves; wherein, the four groove groups are respectively distributed in the upper right, upper left, lower left, and lower right of the disk, and the two adjacent groove groups are arranged symmetrically about the diameter of the disk, the groove group located in the upper left is provided with three columns of grooves, and each column of grooves is provided with four grooves of different diameters, wherein the four grooves of different diameters in the middle column are arranged from small to large in diameter from top to bottom, and the four grooves of different diameters in the other two columns are arranged from large to small in diameter from top to bottom, and the arrangement of the groove group located in the upper right is the same as that of the groove group located in the upper left;

[0036] The groove group at the lower left also has three rows of grooves, each row has four grooves of different diameters. The four grooves of different diameters in the middle row are arranged from largest to smallest from top to bottom, and the four grooves of different diameters in the other two rows are arranged from smallest to largest from top to bottom. The arrangement of the groove group at the lower right is the same as that of the groove group at the lower left.

[0037] The depths of the four groove groups are different and decrease in the range of 1.0 mm to 0.1 mm in the order of the groove group located at the upper right, the groove group located at the upper left, the groove group located at the lower left, and the groove group located at the lower right;

[0038] The low contrast resolution module assembly hole is connected to the high contrast resolution module assembly hole through a 17.5mm third sleeve at the top, and is connected to the lower base through a 27.5mm fourth sleeve below the low contrast resolution module assembly hole.

[0039] Furthermore, the geometric distortion module consists of a grid and inclined slices arranged on the four sides of the grid. The grid has a square structure and contains a total of 100 cells inside the grid, distributed in a 10*10 pattern. The cells are square, and each of the four inclined slices on the outer side of the grid starts from the bottom vertex of one side of the grid and ends at the top vertex of the other side of the grid.

[0040] Furthermore, the depth of all grooves located at the upper right is 1.0 mm, the depth of all grooves located at the upper left is 0.5 mm, the depth of all grooves located at the lower left is 0.25 mm, and the depth of all grooves located at the lower right is 0.1 mm.

[0041] Furthermore, two water injection holes are provided at the edge of the upper cover of the right cylindrical hollow cylinder. The side of the right cylindrical hollow cylinder is the side wall of the right cylindrical hollow cylinder. There are 3 positioning lines for laser positioning on the side wall of the right cylindrical hollow cylinder. Among them, a vertical straight positioning line is provided in front and behind the side wall of the right cylindrical hollow cylinder, passing through the side wall of the right cylindrical hollow cylinder, and a circular positioning line is provided around the center position of the side wall of the right cylindrical hollow cylinder.

[0042] The objectives of the present invention and the technical problems solved therein are also achieved by the following technical solutions. According to the present invention, a method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom is proposed, which mainly includes:

[0043] Slice thickness evaluation: Using the slice thickness module, automatically locate no fewer than five rows of pixels in the imaging area of ​​each wedge. Each row of pixels encompasses the entire imaging area. Based on the position of each pixel on the signal line and the MRI signal intensity, a mean profile line is drawn, one for each of the upper and lower wedge imaging areas.

[0044] According to the mean profile line, the lengths w1 and w2 of the two wedge-shaped block layer thickness measurement areas are automatically measured, where w1 is the smaller length and w2 is the larger length. Based on the measurement results of w1 and w2, the layer thickness measurement value D is calculated using the following formula:

[0045]

[0046] D=w1 tan(α+θ)

[0047] Where ɑ is the angle of the wedge block. For layer thickness module 2, ɑ = 5.711°;

[0048] θ is the tilt angle introduced by the phantom due to improper placement;

[0049] Furthermore, it also includes image uniformity and signal-to-noise ratio evaluation: the image uniformity module is a uniform water layer. When evaluating uniformity, it automatically locates and draws 9 ROIs arranged in a nine-square grid in the uniform water layer image, and each ROI is less than 100mm 2 Or it contains at least 100 pixels. The software automatically reads the magnetic resonance signal intensity in 9 ROIs, calculates the difference between the maximum and minimum signal values, the sum of the maximum and minimum values, and calculates the image uniformity U according to the formula.

[0050]

[0051] Where: S max is the maximum value of the magnetic resonance signal in the 9 ROIs;

[0052] S minis the minimum value of the magnetic resonance signal in the 9 ROIs;

[0053] When evaluating the signal-to-noise ratio, the software automatically locates and draws five ROIs in the uniform water layer image, including one ROI at the center of the image and one ROI at each of the four corners. Each ROI is smaller than 100 mm. 2 Or contain at least 100 pixels. The software automatically reads the magnetic resonance signal intensity and noise of each ROI and calculates the signal-to-noise ratio (SNR) according to the formula:

[0054]

[0055] Where: S c is the signal intensity of the central ROI;

[0056] S b is the signal intensity of the surrounding background area, that is, the average signal intensity of the four corner ROIs:

[0057] S b =(S1+S2+S3+S4) / 4; SD c is the noise of the center ROI.

[0058] Furthermore, it also includes high-contrast resolution evaluation: when evaluating high-contrast resolution performance, all line pair groups in the high-contrast resolution module image are automatically identified and selected, and a profile curve of each line pair group is drawn based on the signal strength. The modulation depth is calculated based on the profile curve. If the modulation depth is greater than or equal to 50%, the line pair group is considered to be resolvable, and if it is less than 50%, the line pair group is considered to be unresolvable. The calculation formula for the modulation depth PM% is:

[0059] PM%=A / 2B×100

[0060] Where A is the difference between the peak and trough amplitudes of the signal;

[0061] B is the average value of the signal;

[0062] After the modulation depth calculation of all line pair groups is completed, a line pair-modulation depth curve is fitted according to the calculation results, and the line pair value corresponding to 50% modulation depth is calculated.

[0063] Furthermore, it also includes low-contrast resolution evaluation: automatically locate all low-contrast circular spots in the low-contrast resolution module image, draw ROIs inside and around the low-contrast circular spots, automatically read the magnetic resonance signal intensity of each ROI, and calculate the contrast LCR of each circular spot according to the formula:

[0064]

[0065] Where: So is the magnetic resonance signal intensity of the ROI within the circular spot;

[0066] S ob is the magnetic resonance signal intensity of the corresponding surrounding ROI.

[0067] Furthermore, it also includes geometric distortion evaluation: after loading the geometric distortion module image, two selection boxes are displayed on the image. The user drags the selection boxes to select two arbitrary intersection points within the grid. After the grid intersection points are selected, the lower right corner points of the grid intersections within the two selection boxes are automatically located and connected. Then, the nominal value of the line segment length is calculated based on the number of grids involved in the connection. The actual length of the line segment is measured, and the geometric distortion rate is calculated according to the formula:

[0068]

[0069] Where: L m is the measured value of the line segment length;

[0070] L n is the nominal value of the line segment length.

[0071] Compared with the prior art, the present invention has obvious advantages and beneficial effects. It has at least the following advantages:

[0072] 1. The layer thickness module of the present invention can correct the layer thickness measurement error caused by the tilted placement of the phantom, and does not introduce the error caused by the groove water film thickness.

[0073] 2. The geometric distortion module of the present invention adopts an integrated grid design to avoid errors caused by assembly and splicing. The grid wall thickness is as thin as 1mm, and the use of grid corner points for more accurate positioning and smaller errors; the tilt plate on the outside of the grid can be used to determine whether the phantom is tilted.

[0074] 3. The high contrast resolution module of the present invention has enough line pair groups, and the high contrast resolution performance of the center and edge imaging areas can be tested simultaneously in one imaging.

[0075] 4. The low-contrast resolution module of the present invention has a sufficient number of low-contrast circular spots of different diameters and etching depths, which can effectively distinguish the low-contrast resolution of MRI equipment of different grades, and can simultaneously detect the low-contrast resolution performance of the central and edge imaging areas in one imaging.

[0076] 5. Because the MRI device scans slices of equal thickness and spacing, all modules in the phantom are at least 5 mm thick. Furthermore, the modules are arranged so that they are precisely centered on the slice positions of each scan layer, ensuring effective imaging of all modules in a single continuous scan and improving MRI device quality control efficiency.

[0077] 6. All modules in the phantom of the present invention can be flexibly disassembled and assembled. All modules are of an integrated design, which will not introduce assembly errors caused by disassembly and assembly. In addition, the independent modules facilitate the traceability of the phantom;

[0078] 7. In order to objectively analyze and evaluate the experimental data, the present invention has developed an image quality evaluation method that can automatically analyze and process the image quality of data collected by MRI equipment of different brands and models.

[0079] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, which can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0080] Figure 1 This is a three-dimensional diagram of the combined structure and appearance of the Magphan SMR series phantom center test cube.

[0081] Figure 2 It is a three-dimensional schematic diagram of the appearance of the present invention.

[0082] Figure 3 It is a schematic diagram of the overall structure of the present invention.

[0083] Figure 4 It is a schematic diagram of the three-dimensional structure of the layer thickness module of the present invention.

[0084] Figure 5 It is a schematic diagram of the upper surface of the layer thickness module of the present invention.

[0085] Figure 6 It is a schematic diagram of the lower surface of the layer thickness module of the present invention.

[0086] Figure 7 It is a schematic diagram of the three-dimensional structure of the high contrast resolution module of the present invention.

[0087] Figure 8 It is a plan view of the high contrast resolution module of the present invention.

[0088] Figure 9 It is a schematic diagram of the three-dimensional structure of the low-contrast resolution module of the present invention.

[0089] Figure 10 It is a plan view of the low contrast resolution module of the present invention.

[0090] Figure 11 It is a schematic diagram of the three-dimensional structure of the geometric distortion module of the present invention.

[0091] Figure 12 This is a diagram of the signal lines of the layer thickness module of the present invention.

[0092] Figure 13 Schematic diagram of the layer thickness evaluation of the phantom of the present invention.

[0093] Figure 14 Schematic diagram of image uniformity evaluation according to the present invention.

[0094] Figure 15 Schematic diagram of signal-to-noise ratio evaluation of the present invention.

[0095] Figure 16 Schematic diagram of the modulation depth calculation method of the present invention.

[0096] Figure 17 It is a schematic diagram of low contrast resolution evaluation of the present invention.

[0097] Figure 18 Schematic diagram of geometric distortion evaluation of the phantom of the present invention.

[0098] Figure 19 It is a schematic diagram of the scanning slice positioning method of the present invention.

[0099] Figure 20 Actual imaging of the Magphan phantom's geometric distortion module. (Left: Normal MRI device, right: Curved distortion MRI device)

[0100] Figure 21 Actual imaging of the geometric distortion module of the present invention. (Left: Normal MRI device, right: Arc-distortion MRI device)

[0101] Figure 22 Actual imaging of the Magphan phantom layer thickness module.

[0102] Figure 23 Actual imaging of the Magphan phantom's low-contrast resolution module.

[0103] Figure 24 Actual imaging diagram of the low-contrast resolution module of the present invention.

[0104] in:

[0105] 1: Top cover

[0106] 10 bottom

[0107] 11: Side wall of a regular hollow cylinder

[0108] 11-1: Circular positioning line 11-2: Straight positioning line

[0109] 12: Positioning rod 13: Positioning hole

[0110] 2-layer thick module

[0111] 2-1: Wedge block 2-2: Base plate

[0112] 2-3: Assembly holes on the upper surface of the layer thickness module 2-4: Assembly holes on the lower surface of the layer thickness module

[0113] 3 high contrast resolution modules

[0114] 3-1: High contrast resolution module assembly hole

[0115] 4 low contrast resolution modules

[0116] 4-1: Low contrast resolution module assembly hole

[0117] 5: Geometric Distortion Module

[0118] 5-1: Grid 5-2: Inclined sheet

[0119] 6: First casing

[0120] 7: Second sleeve

[0121] 8: The third casing

[0122] 9: The fourth sleeve DETAILED DESCRIPTION

[0123] To further illustrate the technical means and effectiveness of the present invention in achieving its intended objectives, the following, in conjunction with the accompanying drawings and preferred embodiments, describes in detail a medical magnetic resonance imaging equipment performance testing phantom and image quality evaluation method according to the present invention, including its specific implementation, structure, method, steps, features, and effectiveness.

[0124] See also Figure 2-Figure 11 As shown, a medical magnetic resonance imaging equipment performance testing phantom according to a preferred embodiment of the present invention is a right cylindrical sealed structure, comprising: a right cylindrical hollow tube, an upper cover 1, and multiple layers of performance testing modules. The upper cover 1 is fixed to the top of the right cylindrical hollow tube. Multiple layers of performance testing modules are stacked inside the right cylindrical hollow tube. Each module is independent of each other. From top to bottom, a layer thickness module 2, an image uniformity module, a high contrast resolution module 3, a low contrast resolution module 4, and a geometric distortion module 5 are sequentially arranged. The image uniformity module is a uniform water layer between the layer thickness module 2 and the high contrast resolution module 3. The geometric distortion module 5 is a grid structure and is fixed to the lower base 10 inside the right cylindrical hollow tube. The layer thickness module 2, the high contrast resolution module 3, and the low contrast resolution module 4 are all disc structures.

[0125] The top cover 1 and each module are equipped with four assembly holes for connecting to other modules. The connection lines between the centers of the four assembly holes are equal and square. Two water injection holes are set at the edge of the top cover 1 of the cylindrical hollow cylinder. The side of the cylindrical hollow cylinder is the cylindrical hollow cylinder side wall 11. The cylindrical hollow cylinder side wall 11 is equipped with a total of three positioning lines for laser positioning. Among them, a vertical linear positioning line 11-2 is set at the front and back of the cylindrical hollow cylinder side wall 11, running through the cylindrical hollow cylinder side wall 11. A circular positioning line 11-1 is set around the center of the cylindrical hollow cylinder side wall.

[0126] The four layer thickness module upper surface assembly holes 2-3 provided on the upper surface of the layer thickness module 2 correspond one to one with the assembly holes on the lower surface of the upper cover 1, and are evenly distributed on the layer thickness module 2 and the upper cover in a square distribution;

[0127] The four layer thickness module lower surface assembly holes 2-4 provided on the lower surface of the layer thickness module, the four high contrast resolution module assembly holes 3-1 provided on the high contrast resolution module 3, the four low contrast resolution module assembly holes 4-1 provided on the low contrast resolution module 4, and the four lower bottom assembly holes provided on the surface of the lower base 10 correspond one to another, and are evenly distributed on the lower surface of the layer thickness module 2, the high contrast resolution module 3, the low contrast resolution module 4, and the lower base 10 respectively;

[0128] The four assembly holes 2-4 on the lower surface of the layer thickness modules, the four assembly holes 3-1 for the high-contrast resolution modules, the four assembly holes 4-1 for the low-contrast resolution modules, and the four assembly holes on the upper surface of the lower base are respectively located on the midlines of the four lines connecting the centers of the assembly holes 2-3 on the upper surfaces of the four layer thickness modules, that is, the four assembly holes 2-4 on the lower surface of the layer thickness modules, the four assembly holes 3-1 for the high-contrast resolution modules, the four assembly holes 4-1 for the low-contrast resolution modules, and the four assembly holes on the upper surface of the lower base 10 are rotated 45° relative to the assembly holes 2-3 on the upper surfaces of the four layer thickness modules to form a square distribution;

[0129] The modules are connected by four acrylic rods and sleeves of different lengths. The acrylic rods pass through the assembly holes and are matched with the sleeves to support the modules and control the distance between the modules. The upper cover 1 and the layer thickness module 2 are connected by four 30mm first sleeves 6, the layer thickness module 2 and the high contrast resolution module 3 are connected by four 25mm second sleeves 7, the high contrast resolution module 3 and the low contrast resolution module 4 are connected by four 17.5mm third sleeves 8, and the low contrast resolution module 4 and the lower base 10 are connected by four 27.5mm fourth sleeves 9.

[0130] The high-contrast resolution module 3 and the low-contrast resolution module 4 are provided with positioning holes 13, and the layer thickness module 2 and the image uniformity module are provided with four positioning rods 12. The positions of the positioning holes or positioning rods correspond one to another. The four positioning holes 13 and the four positioning rods 12 are arranged at the upper left corner, upper right corner, lower left corner and lower right corner of the edge of each module. The overall distribution is rectangular and the center of the rectangle is the center of each module.

[0131] The layer thickness module 2 consists of a group of cross-placed wedge blocks 2-1 and a disc-shaped substrate 2-2. The wedge blocks 2-1 are fixed on the substrate 2-2. The long sides of the two wedge blocks 2-1 are relatively close and are in the same line as the diameter of the substrate 2-2. Four positioning rods 12 are fixed on the substrate 2-2, wherein the positioning rods 12 extend 20 mm from the upper surface of the layer thickness module 2 and extend 20 mm from the lower surface. The upper surface assembly holes 2-3 of the layer thickness module and the lower surface assembly holes of the upper cover 1 correspond one to one, and are connected by a 30 mm sleeve 6. The lower surface assembly holes 2-4 of the layer thickness module and the high contrast resolution module assembly holes 3-1 correspond one to one, and are connected by a 25 mm sleeve 7.

[0132] The high-contrast resolution module 3 is a disk with 24 hollowed-out line pairs. Each line pair consists of 3 to 5 rectangular through-holes, and all line pairs have the same length.

[0133] Within each wire pair group, the width of the rectangular through-hole is the same as the distance between two adjacent rectangular through-holes. There are 12 wire pair groups with different widths, and each width has 2 wire pair groups, totaling 24 wire pair groups. The 24 wire pair groups are arranged in two ways, 12 of which are distributed in an L-shape at the edge of the module, and the other 12 are distributed in the center area of ​​the module.

[0134] The high-contrast resolution module assembly hole 3-1 is connected to the layer thickness module lower surface assembly hole 2-4 through a 25mm second sleeve 7 at the top, and is connected to the low-contrast resolution module assembly hole 4-1 through a 17.5mm third sleeve 8 below the high-contrast resolution module assembly hole 3-1.

[0135] The low-contrast resolution module 4 is a circular disk. Four groups of grooves of different depths are etched on the upper surface of the low-contrast resolution module 4. Each groove group includes grooves of four different diameters, with three grooves of each diameter, for a total of 12 grooves. The four groove groups have a total of 48 grooves. The four groove groups are respectively distributed in the upper right, upper left, lower left, and lower right of the disk, and two adjacent groove groups are arranged symmetrically about the diameter of the disk. The groove group located in the upper left has three columns of grooves, and each column has four grooves of different diameters. The four grooves of different diameters in the middle column are arranged from small to large diameter from top to bottom, and the four grooves of different diameters in the other two columns are arranged from large to small diameter from top to bottom. The arrangement of the groove group located in the upper right is the same as that of the groove group located in the upper left.

[0136] The groove group at the lower left also has three rows of grooves, each row has four grooves of different diameters. The four grooves of different diameters in the middle row are arranged from largest to smallest from top to bottom, and the four grooves of different diameters in the other two rows are arranged from smallest to largest from top to bottom. The arrangement of the groove group at the lower right is the same as that of the groove group at the lower left.

[0137] The depths of the four groove groups are different and decrease in the order of the groove group located at the upper right, the groove group located at the upper left, the groove group located at the lower left, and the groove group located at the lower right, ranging from 1.0 mm to 0.1 mm. The depth of all grooves located at the upper right is 1.0 mm, the depth of all grooves located at the upper left is 0.5 mm, the depth of all grooves located at the lower left is 0.25 mm, and the depth of all grooves located at the lower right is 0.1 mm.

[0138] The low contrast resolution module assembly hole 4-1 is connected to the high contrast resolution module assembly hole 3-1 at the top through a 17.5 mm third sleeve 8, and is connected to the bottom 10 at the bottom through a 27.5 mm fourth sleeve 9.

[0139] The geometric distortion module 5 consists of a grid 5-1 and inclined slices 5-2 arranged on the four sides of the grid 5-1. The grid 5-1 has a square structure and contains a total of 100 cells inside the grid 5-1, which are distributed in a 10*10 pattern. The cells are square, and each of the four inclined slices on the outer side of the grid 5-1 starts from the bottom vertex of one side of the grid 5-1 and ends at the top vertex of the other side of the grid 5-1.

[0140] Another preferred embodiment of the present invention is a phantom embodiment for testing the performance of medical magnetic resonance imaging equipment.

[0141] like Figure 2As shown, it is a right cylindrical sealing structure, including: a right cylindrical hollow cylinder, an upper cover 1, and a multi-layer performance testing module. The right cylindrical hollow cylinder is 140mm high, with an outer diameter of 200mm, an inner diameter of 180mm, a sidewall thickness of 10mm, and a thickness of 10mm on both the upper and lower bases. The upper cover is fixed on the top of the right cylindrical hollow cylinder, and the edge of the upper cover 1 has two water injection holes.

[0142] There are a total of 3 positioning lines on the right cylindrical hollow cylinder for laser positioning, among which the side of the right cylindrical hollow cylinder is the right cylindrical hollow cylinder side wall 11, and there are a total of 3 positioning lines for laser positioning on the right cylindrical hollow cylinder side wall 11, among which, a vertical straight line positioning line 11-2 is set in front of and behind the right cylindrical hollow cylinder side wall 11, passing through the right cylindrical hollow cylinder side wall 11, and a circular positioning line 11-1 is set around the center position of the right cylindrical hollow cylinder side wall.

[0143] like Figure 3 As shown, multiple layers of performance detection modules are stacked inside the right cylindrical hollow tube. Each module is independent of each other. From top to bottom, a layer thickness module 2, an image uniformity module, a high contrast resolution module 3, a low contrast resolution module 4, and a geometric distortion module 5 are sequentially arranged. Among them, the image uniformity module is a uniform water layer between the layer thickness module 2 and the high contrast resolution module 3. The geometric distortion module 5 is a grid structure and is fixed to the lower base 10 inside the right cylindrical hollow tube. The layer thickness module 2, the high contrast resolution module 3, and the low contrast resolution module 4 are all disc structures.

[0144] Each module has four positioning holes 13 or positioning rods 12 with a diameter of 2 mm for positioning the image quality evaluation software. Among them, the high-contrast resolution module and the low-contrast resolution module are positioning holes 13, and the layer thickness module and the image uniformity module are positioning rods 12. The positions of the positioning holes or positioning rods correspond one to one. The four positioning holes 13 and the four positioning rods 12 are set at the upper left corner, upper right corner, lower left corner and lower right corner of the edge of each module, distributed in a rectangular shape, and the center of the rectangle is the center of the circle of each module.

[0145] See Figure 4-Figure 5 As shown, there are 4 assembly holes on the upper cover and each module 1 for connecting other modules. The diameter of the assembly hole is 10mm. The assembly holes on the upper surface of the layer thickness module 2 and the lower surface of the upper cover 1 correspond to each other one by one and are evenly distributed on a circle with a diameter of 70mm in a square distribution.

[0146] See Figure 6As shown, the layer thickness module lower surface assembly holes 2-4 arranged on the lower surface of the four layer thickness modules, the four high contrast resolution module assembly holes 3-1 arranged on the high contrast resolution module 3, the four low contrast resolution module assembly holes 4-1 arranged on the low contrast resolution module 4 and the four lower bottom assembly holes arranged on the surface of the lower base 10 correspond one to another, and are evenly distributed on the lower surface of the layer thickness module 2, the high contrast resolution module 3, the low contrast resolution module 4 and the lower base 10 respectively; the four layer thickness modules The assembly holes 2-4 on the lower surface of the block, the four assembly holes 3-1 of the high-contrast resolution module, the four assembly holes 4-1 of the low-contrast resolution module and the four assembly holes on the upper surface of the lower base are respectively located on the midlines of the four connecting lines between the centers of the assembly holes 2-3 on the upper surfaces of the four layer thickness modules 2, that is, the assembly holes 2-4 on the lower surface of the four layer thickness modules, the four assembly holes 3-1 of the high-contrast resolution module, the four assembly holes 4-1 of the low-contrast resolution module and the four assembly holes on the upper surface of the lower base 10 are rotated 45° relative to the assembly holes 2-3 on the upper surfaces of the four layer thickness modules and are distributed in a square.

[0147] The modules are connected by four acrylic rods with a diameter of 10 mm and sleeves of different lengths. The acrylic rods pass through the assembly holes and are matched with the sleeves to support the modules and control the distance between the modules. The upper cover 1 and the layer thickness module 2 are connected by four 30 mm sleeves 6, the layer thickness module 2 and the high contrast resolution module 3 are connected by four 25 mm sleeves 7, the high contrast resolution module 3 and the low contrast resolution module 4 are connected by four 17.5 mm sleeves 8, and the low contrast resolution module 4 and the bottom are connected by four 27.5 mm sleeves 9.

[0148] The layer thickness module 2 consists of a set of cross-placed wedge blocks 2-1 and a disc-shaped base plate 2-2. The wedge blocks 2-1 are 15mm high and 150mm long, and each wedge block is 10mm wide. They are fixed to the base plate 2-2 with a diameter of 160mm and a thickness of 5mm. The long sides of the two wedge blocks are relatively close to each other and are aligned with the diameter of the disc-shaped base plate 2-2. Four positioning rods 12 are fixed to the disc-shaped base plate 2-2. The positioning rods 12 extend 20mm from the upper surface of the layer thickness module 2 and 20mm from the lower surface of the layer thickness module 2. Figure 4 shown.

[0149] The assembly holes 2-3 on the upper surface of the layer thickness module and the assembly holes on the lower surface of the upper cover correspond one to another and are connected through a 30mm sleeve 6, such as Figure 5 shown.

[0150] The assembly holes 2 - 4 on the lower surface of the layer thickness module and the assembly holes 3 - 1 of the high contrast resolution module correspond one to one and are connected via a 25 mm sleeve 7 .

[0151] The overall structure of the high contrast resolution module (3) is a disk with a diameter of 160mm and a thickness of 5mm. 24 line pair groups are hollowed out on the disk. Each line pair group consists of 3 to 5 rectangular through-holes. The length of all line pairs is 12mm. In each line pair group, the width of the rectangular through-hole is the same as the distance between two adjacent rectangular through-holes. Taking a 5mm line pair group as an example, it consists of 3 rectangular through-holes with a length of 12mm and a width of 5mm. The interval between each rectangular through-hole is 5mm. The number of through-holes and the corresponding line width and line spacing of all line pair groups are shown in Table 1. There are 12 types of line pair groups with different widths. Each width has 2 line pair groups, for a total of 24 line pair groups. The 24 line pair groups are arranged in two ways. Among them, 12 line pair groups are distributed in an L-shaped manner at the edge of the module, and the other 12 line pair groups are distributed in the center area of ​​the module. Figure 7-Figure 8 shown.

[0152] The high contrast resolution module assembly hole 3-1 is connected to the layer thickness module lower surface assembly hole 2-4 through a 25mm second sleeve 7 at the top, and is connected to the low contrast resolution module assembly hole 4-1 through a 17.5mm third sleeve 8 at the bottom.

[0153] Table 1 Number of through holes in line pair groups and corresponding line width and line spacing

[0154]

[0155]

[0156] For the 12 line pair groups with L-shaped distribution, the 5mm, 2.5mm, 1.5mm, 1.2mm, and 1.1mm line pair groups are arranged horizontally, with the lower right vertex of the 5mm line pair group 46mm to the right of the center of the circle and 35mm above it, and the 2.5mm, 1.5mm, 1.2mm, and 1.1mm line pair groups are located to the left of the 5mm line pair group, with intervals of 5mm in sequence; the 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, and 1.0mm line pair groups are arranged vertically, with the lower right vertex of the 0.4mm line pair group 30mm to the left of the center of the circle and 46mm below it, and the 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, and 1.0mm line pair groups are located above the 0.4mm line pair group, with intervals of 5mm in sequence.

[0157] For the 12 line-pair groups in the center area, the 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, and 1.0mm line-pair groups are arranged horizontally. The upper right vertex of the 1.0mm line-pair group is located 5mm below and 5mm to the left of the center of the circle. The 0.9mm line-pair group is 10mm above the 1.0mm line-pair group. The 0.8mm, 0.7mm, 0.6mm, 0.5mm, and 0.4mm line-pair groups are located to the right of the 0.9mm line-pair group, with intervals of 5mm in sequence. The 5mm, 2.5mm, 1.5mm, 1.2mm, and 1.1mm line pair groups are arranged vertically, with the upper left vertex of the 1.1mm line pair group located 5mm below the center of the circle. The 1.2mm and 5mm line pair groups are to the right of the 1.1mm line pair group, with intervals of 5mm in sequence. The 1.5mm line pair group is 5mm below the 1.1mm line pair group, and the 2.5mm line pair group is 5mm to the right of the 1.5mm line pair group.

[0158] The high contrast resolution module assembly hole 3-1 is connected to the layer thickness module lower surface assembly hole 2-4 through a 25mm sleeve 7 at the top, and is connected to the low contrast resolution module assembly hole 4-1 through a 17.5mm sleeve 8 at the bottom.

[0159] The overall structure of the low-contrast resolution module 4 is a disc with a diameter of 160mm and a thickness of 10mm. Four groups of grooves of different depths are etched on the upper surface of the low-contrast resolution module 4; each groove group contains grooves of four diameters, namely 2mm, 4mm, 6mm and 8mm, with three grooves of each diameter, for a total of 12 grooves; the four groups have a total of 48 grooves. Among them, the four groove groups are respectively distributed in the upper right, upper left, lower left and lower right of the disc, and the two adjacent groove groups are arranged symmetrically about the diameter of the disc. The groove group located in the upper left is provided with three columns of grooves, and each column of grooves is provided with four grooves of different diameters. Among them, the four grooves of different diameters in the middle column are arranged from small to large in diameter from top to bottom, and the four grooves of different diameters in the other two columns are arranged from large to small in diameter from top to bottom. The arrangement of the groove group located in the upper right is the same as that of the groove group located in the upper left.

[0160] The groove group at the lower left also has 3 rows of grooves, each row has 4 grooves of different diameters. The 4 grooves of different diameters in the middle row are arranged from top to bottom in descending order of diameter, and the 4 grooves of different diameters in the other two rows are arranged from top to bottom in descending order of diameter. The arrangement of the groove group at the lower right is the same as that of the groove group at the lower left. Figure 9-10 shown.

[0161] The depths of the four groove groups are different and decrease in the range of 1.0mm to 0.1mm in the order of the groove group located at the upper right, the groove group located at the upper left, the groove group located at the lower left and the groove group located at the lower right, among which: the depth of all grooves located at the upper right is 1.0mm, the depth of all grooves located at the upper left is 0.5mm, the depth of all grooves located at the lower left is 0.25mm, and the depth of all grooves located at the lower right is 0.1mm.

[0162] The low contrast resolution module assembly hole 4 - 1 is connected to the high contrast resolution module assembly hole 3 - 1 at the top through a 17.5 mm sleeve 8 , and is connected to the bottom base 10 at the bottom through a 27.5 mm sleeve 9 .

[0163] The geometric distortion module consists of a grid 5-1 and inclined plates 5-2 on the four sides of the grid 5-1. The grid is a square structure with a thickness of 10mm and contains 100 cells in a 10*10 distribution. The cells are square with a side length of 10mm and a wall thickness of 1mm. There are four 1mm thick and 5mm wide inclined plates on the outside of the grid. The four inclined plates are located on the four outermost sides of the grid. Each inclined plate starts from the vertex of the bottom edge and ends at the vertex of the upper edge on the other side. The geometric distortion module is fixed to the inner surface of the bottom bottom of the phantom, as shown in the figure. Figure 11 shown.

[0164] See also Figures 12-18 As shown, in order to reduce subjective factors in the evaluation process and make the evaluation process objective, the present invention abandons the traditional subjective visual evaluation method, refers to the MRI equipment performance evaluation method in the international standard and improves it, and programs the evaluation method to form an image quality evaluation method, which can automatically analyze and process the image quality of data collected by MRI equipment of different brands and models.

[0165] The image quality evaluation method of a preferred embodiment of the present invention mainly includes:

[0166] 1. Layer thickness evaluation method: For the layer thickness phantom 2 of the present invention, automatically locate at least 5 rows of pixels in the imaging area of ​​the two wedge blocks 2-1, and each row of pixels covers the entire imaging area (150mm). Figure 12 As shown. Based on the position and MRI signal intensity of each pixel on the signal line, a mean profile line is drawn. One line is drawn for each of the upper and lower wedge blocks 2-1 imaging areas.

[0167] According to the mean profile line, the lengths w1 and w2 of the thickness measurement areas of the two wedge blocks 2-1 are automatically measured. Where w1 is the smaller length and w2 is the larger length, such as Figure 13 .

[0168] Based on the measurement results of w1 and w2, the layer thickness measurement value D is calculated using the following formula:

[0169]

[0170] D=w1 tan(α+θ)

[0171] Wherein, ɑ is the angle of the wedge block. For the layer thickness module of the present invention, ɑ=5.711°; θ is the tilt angle introduced by the layer thickness module due to improper placement.

[0172] Image uniformity and signal-to-noise ratio evaluation: The uniformity module 3 of this image is a uniform water layer. When evaluating the uniformity, the software automatically locates and draws 9 ROIs arranged in a nine-square grid in the uniform water layer image. Each ROI is less than 100mm 2 Or contain at least 100 pixels, such as Figure 14 The software automatically reads the magnetic resonance signal intensity within 9 ROIs, calculates the difference between the maximum and minimum signal values, the sum of the maximum and minimum values, and calculates the image uniformity U according to the formula.

[0173]

[0174] Where: S max is the maximum value of the magnetic resonance signal in the 9 ROIs; S min It is the minimum value of the magnetic resonance signal in the 9 ROIs.

[0175] When evaluating the signal-to-noise ratio, the software automatically locates and draws five ROIs in the uniform water layer image, including one ROI at the center of the image and one ROI at each of the four corners. Each ROI is smaller than 100 mm. 2 Or contain at least 100 pixels, such as Figure 15 The software automatically reads the magnetic resonance signal intensity and noise of each ROI and calculates the signal-to-noise ratio (SNR) according to the formula:

[0176]

[0177] Where: S c is the signal intensity of the central ROI; S b is the signal intensity of the surrounding background area, that is, the average signal intensity of the four corner ROIs: S b =(S1+S2+S3+S4) / 4; SD c The noise of the center ROI

[0178] 2. High-contrast resolution evaluation method: When evaluating high-contrast resolution performance, the software automatically identifies and selects all line pair groups in the high-contrast resolution module image, and draws a profile curve for each line pair group based on the signal strength. The modulation depth is calculated based on the profile curve. If the modulation depth is greater than or equal to 50%, the line pair group is considered resolvable, and if it is less than 50%, the line pair group is considered unresolvable. The calculation formula for the modulation depth PM% is:

[0179] PM%=A / 2B×100

[0180] Where A is the difference between the peak and trough amplitudes of the signal, and B is the average value of the signal. Figure 16 .

[0181] After the modulation depth calculation of all line pair groups is completed, the software fits the line pair-modulation depth curve based on the calculation results and calculates the line pair value corresponding to 50% modulation depth.

[0182] Low contrast resolution evaluation: The software automatically locates all low contrast circular spots in the low contrast resolution module image and draws ROI inside and around the low contrast circular spots, such as Figure 17 As shown (taking one of the low contrast circular spots as an example). The software automatically reads the magnetic resonance signal intensity of each ROI and calculates the contrast LCR of each circular spot according to the formula:

[0183]

[0184] Where: S o is the magnetic resonance signal intensity of the ROI within the circular spot, S ob is the magnetic resonance signal intensity of the corresponding surrounding ROI.

[0185] 3 Geometric distortion evaluation method: For the phantom of the present invention, after loading the geometric distortion module image, two selection boxes are displayed on the image. The user drags the selection box to select two intersection points within the grid, such as Figure 18 After the grid intersection is selected, the software automatically locates the lower right corner of the grid intersection within the two selection boxes and connects them. It then calculates the nominal value of the line segment length based on the number of grids involved in the connection, measures the actual length of the line segment, and calculates the geometric distortion rate according to the formula:

[0186]

[0187] Where: L m is the measured value of the line segment length; L n is the nominal value of the line segment length.

[0188] Here’s how to use it:

[0189] According to the provisions of the current standard method for detecting the performance of magnetic resonance imaging in traditional Chinese medicine, the phantom of the present invention is perfused with a copper sulfate solution and subjected to a degassing treatment, and it is necessary to ensure that there are no bubbles attached to the inner wall of the phantom and the surface of each module. When using the present invention to perform a performance test on an MRI device, the phantom is first placed axially on the scanning bed, the laser positioning light of the MRI device is turned on, and the position of the phantom is adjusted so that the cross laser positioning line of the MRI device coincides with the straight positioning line 11-2 and the circular positioning line 11-1 on the phantom shell. The phantom is scanned using a commonly used clinical scanning sequence, with a total of 10 slices set, the slice thickness set to 5 mm, and the center of the first slice position set at the center of the layer thickness module, which can ensure that all modules are at the center of the slice position. Figure 19 After the scanning parameters are set, the phantom of the present invention can be continuously scanned. After the scanning is completed, the MRI image of the phantom of the present invention is imported into the image quality evaluation software of the present invention for automatic analysis and processing and an evaluation result is given.

[0190] The present invention can perform all the tests performed by existing medical MRI performance testing phantoms, such as ACR and Magphan SMR. Furthermore, the slice thickness module 2 corrects for slice thickness measurement errors caused by tilted phantom placement and eliminates errors caused by water film thickness in the grooves. The slope of the wedge 2-1 in the slice thickness module 2 is 0.1, which ensures a sufficiently large measurement area during actual imaging, facilitates length measurement, and reduces measurement errors. The high-contrast resolution module 3 can measure from 1 Lp / cm to 12.5 Lp / cm, exceeding the measurement range and accuracy of all existing phantoms. It can also simultaneously detect high-contrast resolution in both the center and periphery of the imaging area in a single imaging session. The low-contrast resolution module 4 features four groove diameters: 2 mm, 4 mm, 6 mm, and 8 mm. Each groove diameter has four depths: 1.0 mm, 0.5 mm, 0.25 mm, and 0.1 mm, for a total of 48 low-contrast circular spots. This effectively differentiates the low-contrast resolution capabilities of different MRI equipment grades and allows for simultaneous detection of low-contrast resolution in both the center and periphery of the imaging area in a single imaging session. The geometric distortion module 5 adopts an integrated grid design to avoid errors caused by assembly and splicing. The grid wall thickness is as thin as 1mm, and the positioning using the grid corner points is more accurate and the error is smaller. The grid can be used to detect the geometric distortion rate at any position, in any direction, and at any length within the grid imaging area. The arrangement of each module makes each module exactly located at the slice position center of each layer of scanning slice, which can ensure that effective imaging of all modules is completed in one continuous scan, significantly improving the quality control efficiency of MRI equipment. All modules in the phantom can be flexibly disassembled and assembled, and all modules are of an integrated design, which will not introduce assembly errors caused by disassembly and assembly. In order to ensure the accuracy of the measurement value of the performance test phantom used to evaluate the performance of medical magnetic resonance equipment, it is necessary to trace the measurement value of the performance test phantom, and a high-precision optical projector and grating micrometer are required for tracing. The phantom of the present invention is a multi-module integrated phantom, and each module is independent of each other and easy to disassemble. The module can be directly placed on the measuring platform of the optical projector or grating micrometer for calibration and traceability. The image quality assessment software can evaluate parameters such as slice thickness, image uniformity, signal-to-noise ratio, high-contrast resolution, low-contrast resolution, and geometric distortion. In addition to the existing line pair set of the phantom's high-contrast resolution module, the software can also calculate the theoretical high-contrast resolution performance achievable by the MRI device based on the evaluation results. Furthermore, the software can calculate the minimum contrast that can be recognized by the MRI device based on actual scanned images of the phantom's low-contrast resolution module. The software can automatically analyze and process image quality data collected by different brands and models of MRI devices.

[0191] Experimental verification:

[0192] The performance of the same medical MRI device was tested using both the present invention and the Magphan phantom. The phantoms used the same imaging solution, and all scanning parameters of the medical MRI device were set to the same values, with a slice thickness of 5 mm. The test results are shown in Table 2.

[0193] Table 2 Comparison of detection results of the present invention and Magphan phantom

[0194]

[0195] The test results show that for the parameters measured using the uniformity module, signal-to-noise ratio and image uniformity, the test results are relatively consistent due to the same imaging solution used.

[0196] For the geometric distortion test project, since the Magphan phantom geometric distortion module is composed of two acrylic semi-circular discs, gaps and height differences are generated after splicing, such as Figure 20 , and this error cannot be accurately measured, resulting in inaccurate nominal values ​​of the geometric distortion module, so the detection result has a large error; In addition, in addition to geometric distortion, medical magnetic resonance equipment may also produce arc distortion, but this phenomenon cannot be observed when using the Magphan phantom to detect geometric distortion, such as Figure 20 When using the present invention for geometric distortion detection, the integrated grid design avoids errors caused by assembly and splicing. The grid wall thickness is as thin as 1mm, and the grid corner positioning is more accurate and has smaller errors. It can also effectively observe arc distortion phenomena, such as Figure 21 .

[0197] For layer thickness detection projects, due to the incorrect placement of the Magphan phantom, such as Figure 22 , and the phantom cannot correct the deflection angle error introduced by improper placement, resulting in large errors in the layer thickness measurement results. When using the present invention for layer thickness detection, the layer thickness measurement error caused by the tilted placement of the phantom can be corrected, and the deflection angle caused by the tilted placement of the phantom can be calculated, resulting in more accurate detection results.

[0198] For the high contrast resolution test item, the test results of the two phantoms are similar, but the measurement accuracy of the high contrast resolution module of the present invention is higher, reaching 0.5Lp / cm, which is higher than the 1Lp / cm of the Magphan phantom.

[0199] For low contrast resolution detection projects, there are only 12 low contrast circular spots in the low contrast resolution module of the Magphan phantom, and the etching depth is deep, with the shallowest etching depth being 0.5mm. As a result, the medical magnetic resonance equipment can clearly distinguish all low contrast circular spots, such as Figure 23When the phantom was used to detect medical magnetic resonance equipment, the minimum contrast measured was 57.94%, which contradicts the significance of low contrast resolution detection. The low contrast resolution module of the present invention has 48 low contrast circular spots with a minimum etching depth of 0.1 mm. It has a certain degree of discrimination for the low contrast resolution performance of medical magnetic resonance equipment, such as Figure 24 The measured minimum contrast is 8.4%, which can effectively reflect the ability of medical magnetic resonance equipment to distinguish low-contrast materials.

[0200] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make slight changes or modifications to equivalent embodiments using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A phantom for testing the performance of medical magnetic resonance imaging equipment, characterized by: The invention is a cylindrical sealed structure, comprising: a cylindrical hollow cylinder, an upper cover (1) and a multi-layer performance detection module, wherein the upper cover (1) is fixed on the upper surface of the cylindrical hollow cylinder, and the multi-layer performance detection module is stacked inside the cylindrical hollow cylinder, and each module is independent of each other. From top to bottom, a layer thickness module (2), an image uniformity module, a high contrast resolution module (3), a low contrast resolution module (4) and a geometric distortion module (5) are sequentially arranged at intervals, wherein the layer thickness module (2), the high contrast resolution module (3) and the low contrast resolution module (4) are all disk structures; the image uniformity module is a uniform water layer between the layer thickness module (2) and the high contrast resolution module (3); the geometric distortion module (5) is a grid structure, and the geometric distortion module (5) is fixed on the lower bottom (10) inside the cylindrical hollow cylinder; The upper cover (1) and each module are provided with four assembly holes for connecting to other modules, and the distances between the centers of the four assembly holes are equal to form a square; Each module is connected by 4 acrylic rods and sleeves of different lengths. The acrylic rods pass through the assembly holes and are matched with the sleeves to support each module and control the distance between modules. The layer thickness module (2) is composed of a group of cross-placed wedge blocks (2-1) and a disc-shaped base plate (2-2), the wedge blocks (2-1) are fixed on the base plate (2-2), the long sides of the two wedge blocks (2-1) are relatively close to each other and are in the same straight line with the diameter of the base plate (2-2), four positioning rods (12) are fixed on the base plate (2-2), wherein the positioning rods (12) extend to a height of 20 mm on the upper surface of the layer thickness module 2, and extend to a height of 20 mm on the lower surface of the positioning rods (12), the upper surface assembly holes (2-3) of the layer thickness module and the lower surface assembly holes of the upper cover (1) correspond one to one, and are connected by a 30 mm first sleeve (6), the lower surface assembly holes (2-4) of the layer thickness module and the high contrast resolution module assembly holes (3-1) correspond one to one, and are connected by a 25 mm second sleeve (7); The high contrast resolution module (3) is a disk with 24 hollowed-out line pair groups, each line pair group is composed of 3 to 5 rectangular through holes, and all line pairs have the same length; Within each line pair group, the width of the rectangular through-hole is the same as the distance between two adjacent rectangular through-holes. There are 12 line pair groups with different widths, each with two line pair groups, for a total of 24 line pair groups. The 24 line pair groups are arranged in two ways: 12 line pair groups are distributed in an L-shape at the edge of the module, and the other 12 line pair groups are distributed in the center of the module. The high-contrast resolution detection range is 1Lp / cm to 12.5Lp / cm. The high contrast resolution module assembly hole (3-1) is connected to the layer thickness module lower surface assembly hole (2-4) through a 25mm second sleeve (7) at the top, and is connected to the low contrast resolution module assembly hole (4-1) through a 17.5mm third sleeve (8) at the bottom of the high contrast resolution module assembly hole (3-1); The low-contrast resolution module (4) is a disk. Four groups of grooves of different depths are etched on the upper surface of the low-contrast resolution module (4). Each groove group includes grooves of four different diameters, and there are three grooves of each diameter, totaling 12 grooves. The four groove groups have a total of 48 grooves. The four groove groups are respectively distributed on the upper right, upper left, lower left, and lower right of the disk, and two adjacent groove groups are symmetrically arranged about the diameter of the disk. The groove group located on the upper left is provided with three rows of grooves, and each row of grooves is provided with four grooves of different diameters. The four grooves of different diameters in the middle row are arranged from small to large in diameter from top to bottom, and the four grooves of different diameters in the other two rows are arranged from large to small in diameter from top to bottom. The arrangement of the groove group located on the upper right is the same as that of the groove group located on the upper left. The groove group at the lower left also has three rows of grooves, each row has four grooves of different diameters. The four grooves of different diameters in the middle row are arranged from largest to smallest from top to bottom, and the four grooves of different diameters in the other two rows are arranged from smallest to largest from top to bottom. The arrangement of the groove group at the lower right is the same as that of the groove group at the lower left. The depths of the four groove groups are different and decrease in the range of 1.0 mm to 0.1 mm in the order of the groove group located at the upper right, the groove group located at the upper left, the groove group located at the lower left, and the groove group located at the lower right; The depth of all grooves located at the upper right is 1.0 mm, the depth of all grooves located at the upper left is 0.5 mm, the depth of all grooves located at the lower left is 0.25 mm, and the depth of all grooves located at the lower right is 0.1 mm; The low contrast resolution module assembly hole (4-1) is connected to the high contrast resolution module assembly hole (3-1) at the top through a 17.5 mm third sleeve (8), and is connected to the bottom (10) at the bottom through a 27.5 mm fourth sleeve (9); The geometric distortion module (5) is composed of a grid (5-1) and inclined pieces (5-2) arranged on the four sides of the grid (5-1). The grid (5-1) is a square structure. The grid (5-1) contains a total of 100 cells distributed in a 10*10 pattern. The cells are square. Each of the four inclined pieces on the outer side of the grid (5-1) starts from the bottom vertex of one side of the grid (5-1) and ends at the top vertex of the other side of the grid (5-1).

2. The medical magnetic resonance imaging equipment performance testing phantom according to claim 1, characterized in that: The four layer thickness module upper surface assembly holes (2-3) arranged on the upper surface of the layer thickness module 2 and the assembly holes on the lower surface of the upper cover (1) correspond one to one, and are evenly distributed on the layer thickness module (2) and the upper cover (1) in a square distribution; the four layer thickness module lower surface assembly holes (2-4) arranged on the layer thickness module lower surface, the four high contrast resolution module assembly holes (3-1) arranged on the high contrast resolution module (3), the four low contrast resolution module assembly holes (4-1) arranged on the low contrast resolution module (4), and the four lower bottom assembly holes arranged on the surface of the lower bottom (10) correspond one to one, and are evenly distributed on the lower surface of the layer thickness module (2), the high contrast resolution module (3), the low contrast resolution module (4), and the lower bottom (10) respectively; The four assembly holes (2-4) on the lower surface of the layer thickness modules, the four assembly holes 3-1 for the high contrast resolution modules, the four assembly holes (4-1) for the low contrast resolution modules, and the four assembly holes on the upper surface of the lower base are respectively located on the midlines of the four connecting lines between the centers of the assembly holes (2-3) on the upper surface of the four layer thickness modules, that is, the four assembly holes (2-4) on the lower surface of the layer thickness modules, the four assembly holes (3-1) for the high contrast resolution modules, the four assembly holes (4-1) for the low contrast resolution modules, and the four assembly holes on the upper surface of the lower base (10) are rotated 45 degrees relative to the assembly holes (2-3) on the upper surface of the four layer thickness modules to form a square distribution.

3. The medical magnetic resonance imaging equipment performance testing phantom according to claim 1, characterized in that: The upper cover (1) and the layer thickness module (2) are connected via four first sleeves (6), the layer thickness module (2) and the high contrast resolution module (3) are connected via four second sleeves (7), the high contrast resolution module (3) and the low contrast resolution module (4) are connected via four third sleeves (8), and the low contrast resolution module (4) and the lower base (10) are connected via four fourth sleeves (9).

4. The medical magnetic resonance imaging equipment performance testing phantom according to claim 1, characterized in that: The high contrast resolution module (3) and the low contrast resolution module 4 are provided with positioning holes (13), the layer thickness module 2 and the image uniformity module are provided with four positioning rods (12), the positions of the positioning holes or positioning rods correspond one to another, the four positioning holes (13) and the four positioning rods (12) are arranged at the upper left corner, upper right corner, lower left corner and lower right corner of the edge of each module, and the overall distribution is rectangular, and the center of the rectangle is the center of each module.

5. The medical magnetic resonance imaging equipment performance testing phantom according to claim 1, characterized in that: Two water injection holes are provided at the edge of the upper cover (1) of the cylindrical hollow cylinder. The side of the cylindrical hollow cylinder is the cylindrical hollow cylinder side wall (11). Three positioning lines for laser positioning are provided on the cylindrical hollow cylinder side wall (11), wherein a vertical straight positioning line (11-2) is provided in front of and behind the cylindrical hollow cylinder side wall (11) and passes through the cylindrical hollow cylinder side wall (11), and a circular positioning line (11-1) is provided around the center of the cylindrical hollow cylinder side wall.

6. A method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom according to any one of claims 1 to 5, characterized in that It includes Slice thickness evaluation: using the slice thickness module (2), automatically locate no less than 5 rows of pixels in the imaging area of ​​the two wedge blocks (2-1), each row of pixels covers the entire imaging area, and draw a mean profile line based on the position of each pixel point on the signal line and the magnetic resonance signal intensity, one for each of the upper and lower wedge block imaging areas; According to the mean profile line, the lengths w1 and w2 of the two wedge-shaped block layer thickness measurement areas are automatically measured, where w1 is the smaller length and w2 is the larger length. Based on the measurement results of w1 and w2, the layer thickness measurement value D is calculated using the following formula: D=w1 tan(α+θ) Where ɑ is the angle of the wedge block. For layer thickness module 2, ɑ = 5.711°; θ is the tilt angle introduced by the phantom due to improper placement.

7. The method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom according to claim 6, characterized in that It also includes image uniformity and signal-to-noise ratio evaluation: the image uniformity module is a uniform water layer. When evaluating uniformity, it automatically locates and draws 9 ROIs arranged in a nine-square grid in the uniform water layer image, and each ROI is less than 100mm 2 Or contain at least 100 pixels. The software automatically reads the magnetic resonance signal intensity within 9 ROIs, calculates the difference between the maximum and minimum signal values, the sum of the maximum and minimum values, and calculates the image uniformity U according to the formula; Where: S max is the maximum value of the magnetic resonance signal in the 9 ROIs; S min is the minimum value of the magnetic resonance signal in the 9 ROIs; When evaluating the signal-to-noise ratio, the software automatically locates and draws five ROIs in the uniform water layer image, including one ROI at the center of the image and one ROI at each of the four corners. Each ROI is smaller than 100 mm. 2 Or contain at least 100 pixels. The software automatically reads the magnetic resonance signal intensity and noise of each ROI and calculates the signal-to-noise ratio (SNR) according to the formula: Where: S c is the signal intensity of the central ROI; S b is the signal intensity of the surrounding background area, that is, the average signal intensity of the four corner ROIs: S b =(S1+S2+S3+S4) / 4; SD c is the noise of the center ROI.

8. The method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom according to claim 6, characterized in that It also includes high-contrast resolution evaluation: When evaluating high-contrast resolution performance, all line pair groups in the high-contrast resolution module image are automatically identified and selected, and a profile curve of each line pair group is drawn according to the signal strength. The modulation depth is calculated based on the profile curve. If the modulation depth is greater than or equal to 50%, the line pair group is considered to be resolvable, and if it is less than 50%, the line pair group is considered to be unresolvable. The calculation formula for the modulation depth PM% is: PM%=A / 2B×100 Where A is the difference between the peak and trough amplitudes of the signal; B is the average value of the signal; After the modulation depth calculation of all line pair groups is completed, a line pair-modulation depth curve is fitted according to the calculation results, and the line pair value corresponding to 50% modulation depth is calculated.

9. The method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom according to claim 6, characterized in that It also includes low contrast resolution evaluation: automatically locate all low contrast spots in the low contrast resolution module (4) image, draw ROIs inside and around the low contrast spots, automatically read the magnetic resonance signal intensity of each ROI, and calculate the contrast LCR of each spot according to the formula: Where: S o is the magnetic resonance signal intensity of the ROI within the circular spot; S ob is the magnetic resonance signal intensity of the corresponding surrounding ROI.

10. The method for evaluating image quality after collecting image data from an MRI device using a medical magnetic resonance imaging device performance testing phantom according to claim 6, wherein It also includes geometric distortion evaluation: after loading the geometric distortion module (5) image, two selection boxes are displayed on the image. The user drags the selection box to select two intersection points inside the grid. After the grid intersection points are selected, the lower right corner points of the grid intersection points in the two selection boxes are automatically located and connected. Then, the nominal value of the line segment length is calculated based on the number of grids involved in the connection. The actual length of the line segment is measured and the geometric distortion rate is calculated according to the formula: Where: L m is the measured value of the line segment length; L n is the nominal value of the line segment length.

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