Method and apparatus for absolute quantitative correction of a medical imaging device

Abstract

The application discloses an absolute quantitative correction method and device of a medical imaging equipment, and relates to the technical field of correction of nuclear medical imaging equipment. In the execution of the method, the actual activity concentration of a calibration phantom injected with a first known tracer activity is taken as a first activity concentration; then the activity concentration of the calibration phantom injected with the first known tracer activity in a first image domain acquired and calculated by the medical imaging equipment is taken as a second activity concentration; and finally, a correction factor is calculated based on the first activity concentration and the second activity concentration, and the correction factor is used for correcting the absolute quantification of the medical imaging equipment. In this way, the correction factor is calculated by comparing the activity concentration calculated by the medical imaging equipment with the actual activity concentration of the calibration phantom, so that the medical imaging equipment can accurately adjust the measurement results according to the correction factor when performing subsequent absolute quantitative analysis, and the effect of improving the absolute quantitative accuracy of the medical imaging equipment is achieved.

Description

Technical Field

[0001] This application relates to the field of nuclear medicine imaging equipment calibration technology, and in particular to an absolute quantitative calibration method and apparatus for medical imaging equipment. Background Technology

[0002] In the field of nuclear medicine, medical imaging equipment plays a crucial role. Among them, Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET), as two key CT techniques, are widely used for functional assessment of multiple organs, including the thyroid, kidneys, heart, brain, lungs, and bones, as well as for the diagnosis of related diseases. These two techniques have demonstrated immense value, particularly in the clinical diagnosis and staging of various malignant tumors, providing vital evidence for clinical diagnosis and treatment.

[0003] However, in practical medical imaging equipment applications, there are key technical issues affecting diagnostic accuracy. For example, the detector, as a core component, has unstable gamma photon detection efficiency, exhibiting performance degradation (such as crystal aging) over time, and is susceptible to interference from environmental temperature fluctuations. If the detection efficiency is not calibrated regularly, the conversion between "image signal count" and "actual activity" will deviate, resulting in inaccurate actual activity data obtained based on image signal count, interfering with organ function and disease diagnosis. Furthermore, taking SPECT technology as an example, its spatial resolution is limited. When the target area size is close to or smaller than the detector resolution, a partial volumetric effect occurs where the signal "spills into surrounding normal tissue," causing inaccurate assessment of the radioactivity concentration in the target area and surrounding tissues, reducing diagnostic accuracy.

[0004] Given the problems with absolute quantification in medical imaging equipment, there is an urgent need for a method that can effectively correct the absolute quantification of medical imaging equipment in order to improve the accuracy and reliability of medical imaging diagnosis. Summary of the Invention

[0005] To address the above problems, this application provides an absolute quantitative calibration method for medical imaging equipment, comprising the following:

[0006] In a first aspect, this application provides an absolute quantitative calibration method for medical imaging equipment, the method comprising:

[0007] The actual activity concentration of the calibration phantom injected with the first known tracer activity is taken as the first activity concentration;

[0008] The activity concentration of the calibration phantom with the injected first known tracer activity in the first image domain acquired and calculated by medical imaging equipment is used as the second activity concentration;

[0009] A correction factor is calculated based on the first activity concentration and the second activity concentration, and the correction factor is used to correct the absolute quantification of medical imaging equipment.

[0010] Optionally, after calculating the correction factor, the method further includes:

[0011] A pre-designed measurement phantom is obtained, the structure of which differs from that of the calibration phantom.

[0012] The tracer activity concentration injected into the cavity of the measuring phantom is taken as the third activity concentration, and the tracer activity concentration injected into the sphere of the measuring phantom is taken as the fourth activity concentration; the fourth activity concentration is set based on the third activity concentration at a preset activity concentration ratio;

[0013] The activity concentration of the spheres in the measurement phantom with the injected second known tracer activity is obtained by acquiring and calculating the data using a medical imaging device, and is taken as the fifth activity concentration.

[0014] The fifth activity concentration is corrected based on the correction factor to obtain the corrected fifth activity concentration;

[0015] If the difference between the corrected fifth activity concentration and the fourth activity concentration is less than a preset difference threshold, the correction factor is considered reasonable.

[0016] If the difference between the corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0017] Optionally, the measurement phantom includes multiple spheres, and the step of acquiring and calculating the activity concentration of the spheres in the measurement phantom with the injected second known tracer activity using a medical imaging device as the fifth activity concentration includes:

[0018] The activity concentration of each sphere in the measurement phantom with the injected second known tracer activity is acquired and calculated by a medical imaging device and used as multiple fifth activity concentrations.

[0019] The plurality of fifth activity concentrations are corrected based on the correction factor to obtain a plurality of corrected fifth activity concentrations;

[0020] If the differences between the plurality of corrected fifth activity concentrations and the fourth activity concentration are all less than a preset difference threshold, then the correction factor is considered reasonable.

[0021] If the difference between any corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0022] Optionally, the calculation process for the actual activity concentration of the calibration phantom includes:

[0023] The volume of the calibration phantom is obtained, and the actual activity concentration of the calibration phantom is calculated based on the volume of the calibration phantom and the activity of the first known tracer.

[0024] Optionally, the process of calculating the activity concentration in a first image domain based on a calibration phantom with injected first known tracer activity using medical imaging equipment includes:

[0025] After data acquisition is performed on a calibration phantom injected with a first known tracer activity using the medical imaging device, the first functional image projection data and the first structural image data are obtained.

[0026] A first attenuation correction parameter table is generated based on the first structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the first functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the first attenuation correction parameter table to obtain the three-dimensional volume data of the calibration phantom.

[0027] Set a signal threshold, retain valid signals in the three-dimensional volume data that are greater than the signal threshold, and remove noise signals that are less than or equal to the signal threshold;

[0028] Morphological closing operations are used to perform connected component repair on the effective signal region to obtain a binary mask image that can clearly segment the outline of the calibration phantom.

[0029] Based on the binary mask image, the sum of pixel signals corresponding to the calibrated model is extracted from the three-dimensional volume data and denoted as the total activity in the image domain.

[0030] The activity concentration in the first image domain is calculated using the formula: Activity concentration in the first image domain = Total activity in the image domain / Volume of the calibration phantom.

[0031] Optionally, the calculation of the correction factor based on the first activity concentration and the second activity concentration includes:

[0032] The correction factor is calculated using the formula Correction Factor = Second Activity Concentration / First Activity Concentration; the correction factor is used to characterize the correspondence between the image domain activity concentration and the actual activity concentration of the medical imaging device.

[0033] Optionally, the method for calculating the activity concentration of the spheres in the second image domain of the measurement phantom is as follows:

[0034] The second functional image projection data and the second structural image data of the measurement phantom are obtained by performing data acquisition on a measurement phantom injected with a second known tracer activity through the medical imaging equipment.

[0035] A second attenuation correction parameter table is generated based on the second structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the second functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the second attenuation correction parameter table to obtain the three-dimensional volume data of the measurement phantom.

[0036] A first signal threshold is set, and valid signals in the three-dimensional volume data that are greater than the first signal threshold are retained, while noise signals that are less than or equal to the first signal threshold are removed.

[0037] The point spread function of the three-dimensional volume data is calculated along the preset coordinate axis direction. The layer corresponding to the peak position of the point spread function is taken as the center layer of the sphere in the measurement model. A preset number of adjacent layers on both sides of the center layer are selected to jointly constitute the volume of interest of the sphere.

[0038] A second signal threshold is set, and regions in the volume of interest that are greater than the second signal threshold are retained to segment the contours of the sphere and the measurement phantom cavity. Morphological closing operation is used to perform connected component repair on the segmented contours to obtain a binary mask image of the sphere.

[0039] The image coordinates of each sphere in the binary mask image are calculated based on the centroid localization algorithm, and the image coordinates are converted into physical coordinates.

[0040] Based on the preset size parameters of the spheres, the sum of pixel signals corresponding to each sphere is extracted from the three-dimensional volume data; the image domain activity concentration of the spheres in the measurement phantom is calculated by the formula: image domain activity concentration of the spheres in the measurement phantom = sum of pixel signals corresponding to the spheres / volume of the spheres.

[0041] Optionally, the calibration model is a cylinder with a radius of 100 mm and a height of 100 mm.

[0042] Optionally, the measuring phantom includes: a main body, which is a three-quarter sphere structure, made of polytetrafluoroethylene, the interior of the main body is hollow, and the wall thickness of the sphere is 2mm;

[0043] The cover is fitted and installed at one-quarter of the opening of the main body to achieve a seal of the hollow cavity of the main body;

[0044] The connecting structure is a cylinder, one end of which is fixedly connected to the side of the cover facing the interior of the main body and extends along the spherical center of the main body;

[0045] Four spheres, each with a spherical structure, have diameters of 17mm, 20mm, 28mm, and 30mm, respectively. Each of the four spheres is fixed to the end of the cylinder away from the cover, and the distance between the center of each of the four spheres and the center of the main body is 28mm.

[0046] Secondly, this application provides an absolute quantitative correction device for medical imaging equipment, the device comprising:

[0047] The first acquisition unit is used to take the actual activity concentration of the calibration phantom injected with the first known tracer activity as the first activity concentration;

[0048] The second acquisition unit is used to take the activity concentration of the calibration phantom with the injected first known tracer activity in the first image domain acquired and calculated by the medical imaging equipment as the second activity concentration.

[0049] The calculation unit is used to calculate a correction factor based on the first activity concentration and the second activity concentration, the correction factor being used to correct the absolute quantification of the medical imaging equipment.

[0050] Optionally, the device further includes a verification unit, which is used to obtain a pre-designed measurement phantom after calculating the correction factor, wherein the structure of the measurement phantom is different from the structure of the calibration phantom;

[0051] The tracer activity concentration injected into the cavity of the measuring phantom is taken as the third activity concentration, and the tracer activity concentration injected into the sphere of the measuring phantom is taken as the fourth activity concentration; the fourth activity concentration is set based on the third activity concentration at a preset activity concentration ratio;

[0052] The activity concentration of the spheres in the measurement phantom with the injected second known tracer activity is obtained by acquiring and calculating the data using a medical imaging device, and is taken as the fifth activity concentration.

[0053] The fifth activity concentration is corrected based on the correction factor to obtain the corrected fifth activity concentration;

[0054] If the difference between the corrected fifth activity concentration and the fourth activity concentration is less than a preset difference threshold, the correction factor is considered reasonable.

[0055] If the difference between the corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0056] Optionally, the measurement phantom includes multiple spheres, and the verification unit uses the measurement phantom with injected second known tracer activity to acquire and calculate the activity concentration of the spheres in the measurement phantom in the second image domain of the measurement phantom as the fifth activity concentration, which includes:

[0057] The activity concentration of each sphere in the measurement phantom with the injected second known tracer activity is acquired and calculated by a medical imaging device and used as multiple fifth activity concentrations.

[0058] The plurality of fifth activity concentrations are corrected based on the correction factor to obtain a plurality of corrected fifth activity concentrations;

[0059] If the differences between the plurality of corrected fifth activity concentrations and the fourth activity concentration are all less than a preset difference threshold, then the correction factor is considered reasonable.

[0060] If the difference between any corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0061] Optionally, the device further includes a calculation unit for the actual activity concentration of the calibration phantom, used to calculate the actual activity concentration of the calibration phantom, the calculation process being as follows:

[0062] The volume of the calibration phantom is obtained, and the actual activity concentration of the calibration phantom is calculated based on the volume of the calibration phantom and the activity of the first known tracer.

[0063] Optionally, the device further includes an activity concentration calculation unit in the first image domain, used to acquire first functional image projection data and first structural image data after data acquisition is performed on a calibration phantom injected with a first known tracer activity by the medical imaging device.

[0064] A first attenuation correction parameter table is generated based on the first structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the first functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the first attenuation correction parameter table to obtain the three-dimensional volume data of the calibration phantom.

[0065] Set a signal threshold, retain valid signals in the three-dimensional volume data that are greater than the signal threshold, and remove noise signals that are less than or equal to the signal threshold;

[0066] Morphological closing operations are used to perform connected component repair on the effective signal region to obtain a binary mask image that can clearly segment the outline of the calibration phantom.

[0067] Based on the binary mask image, the sum of pixel signals corresponding to the calibrated model is extracted from the three-dimensional volume data and denoted as the total activity in the image domain.

[0068] The activity concentration in the first image domain is calculated using the formula: Activity concentration in the first image domain = Total activity in the image domain / Volume of the calibration phantom.

[0069] Optionally, the calculation unit is specifically used to calculate the correction factor using the formula correction factor = second activity concentration / first activity concentration; the correction factor is used to characterize the correspondence between the image domain activity concentration and the actual activity concentration of the medical imaging device.

[0070] Optionally, the device further includes: an image domain activity concentration calculation unit for spheres in the measurement phantom, specifically used to: acquire second functional image projection data and second structural image data of the measurement phantom obtained by performing data acquisition on the measurement phantom injected with a second known tracer activity through the medical imaging device;

[0071] A second attenuation correction parameter table is generated based on the second structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the second functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the second attenuation correction parameter table to obtain the three-dimensional volume data of the measurement phantom.

[0072] A first signal threshold is set, and valid signals in the three-dimensional volume data that are greater than the first signal threshold are retained, while noise signals that are less than or equal to the first signal threshold are removed.

[0073] The point spread function of the three-dimensional volume data is calculated along the preset coordinate axis direction. The layer corresponding to the peak position of the point spread function is taken as the center layer of the sphere in the measurement model. A preset number of adjacent layers on both sides of the center layer are selected to jointly constitute the volume of interest of the sphere.

[0074] A second signal threshold is set, and regions in the volume of interest that are greater than the second signal threshold are retained to segment the contours of the sphere and the measurement phantom cavity. Morphological closing operation is used to perform connected component repair on the segmented contours to obtain a binary mask image of the sphere.

[0075] The image coordinates of each sphere in the binary mask image are calculated based on the centroid localization algorithm, and the image coordinates are converted into physical coordinates.

[0076] Based on the preset size parameters of the spheres, the sum of pixel signals corresponding to each sphere is extracted from the three-dimensional volume data;

[0077] The image domain activity concentration of the sphere in the measurement phantom is calculated using the formula: Image domain activity concentration of the sphere = Sum of pixel signals corresponding to the sphere / Volume of the sphere.

[0078] Thirdly, this application provides an apparatus comprising a memory and a processor, the memory for storing instructions or code, and the processor for executing the instructions or code to cause the apparatus to perform the absolute quantitative correction method for medical imaging equipment described in any of the implementations of the first aspect.

[0079] Fourthly, this application provides a computer-readable storage medium storing code, wherein when the code is executed, a device executing the code implements the absolute quantitative calibration method for medical imaging equipment described in any of the implementations of the first aspect.

[0080] This application provides a method for absolute quantification calibration of medical imaging equipment. In performing the method, the actual activity concentration of a calibration phantom injected with a first known tracer activity is firstly taken as the first activity concentration; then, the activity concentration of the calibration phantom injected with the first known tracer activity in a first image domain acquired and calculated by the medical imaging equipment is taken as the second activity concentration; finally, a correction factor is calculated based on the first and second activity concentrations, and the correction factor is used to correct the absolute quantification of the medical imaging equipment.

[0081] In this way, by comparing the activity concentration calculated by the medical imaging equipment with the actual activity concentration of the calibration phantom, a correction factor is calculated. This allows the medical imaging equipment to accurately adjust the measurement results based on the correction factor when performing absolute quantitative analysis in the future, thereby improving the absolute quantitative accuracy of the medical imaging equipment. Attached Figure Description

[0082] To more clearly illustrate the technical solutions in this embodiment or the prior art, the drawings used in the description of the embodiment or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0083] Figure 1A flowchart of an absolute quantitative calibration method for medical imaging equipment provided in this application embodiment;

[0084] Figure 2 This is a schematic diagram of the structure of a calibration phantom provided in an embodiment of this application;

[0085] Figure 3 This is a schematic diagram of the structure of a measuring phantom provided in an embodiment of this application;

[0086] Figure 4 This is a schematic diagram of the structure of an absolute quantitative correction device for a medical imaging equipment provided in an embodiment of this application. Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0088] This application provides an absolute quantitative calibration method for medical imaging equipment, wherein the medical imaging equipment may include SPECT / CT and SPECT.

[0089] The following is a description of some relevant terms used in this application:

[0090] SPECT: Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) are two CT techniques in nuclear medicine. Since they both image gamma rays emitted from the patient's body, they are collectively referred to as emission computed tomography (ECT).

[0091] CT (Computed Tomography): This scan uses X-rays to generate high-resolution images of the human anatomy, clearly showing the shape, size, location, and density characteristics of lesions.

[0092] Figure 1 This is a flowchart illustrating an absolute quantitative calibration method for medical imaging equipment provided in an embodiment of this application. (In conjunction with...) Figure 1 As shown, the absolute quantitative correction method for medical imaging equipment provided in this application embodiment may include:

[0093] S101. The actual activity concentration of the calibration phantom with the first known tracer activity is taken as the first activity concentration.

[0094] The calibration phantom is used to calibrate the accuracy of activity concentration measurements in medical imaging equipment, providing a benchmark for the accuracy of subsequent clinical testing data from medical imaging equipment. The structure of the calibration phantom is as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of the structure of a calibration mold provided in an embodiment of this application. The calibration mold is a cylinder with a radius of 100 mm and a height of 100 mm. The volume of the cylinder is denoted as V1.

[0095] The first known tracer activity refers to a preset tracer, such as Tc-99m labeled tracer for SPECT equipment. After injecting the preset tracer into the calibration phantom of the above-mentioned cylindrical structure, the total activity of the injected tracer is recorded as A1, which is the first known tracer activity.

[0096] The calculation process of the actual activity concentration of the calibration phantom includes: obtaining the volume of the calibration phantom, and calculating the actual activity concentration of the calibration phantom based on the volume of the calibration phantom and the activity of the first known tracer. Specifically, it is obtained through the following formula: Con1-1=(A1 / V1), where Con1-1 is the actual activity concentration of the calibration phantom, A1 is the activity of the first known tracer, and V1 is the volume of the calibration phantom. After the calculation is completed, the calculated actual activity concentration of the calibration phantom is taken as the first activity concentration.

[0097] S102. The activity concentration of the calibration phantom with the first known tracer activity is acquired and calculated by a medical imaging device in the first image domain as the second activity concentration.

[0098] In this embodiment, the medical imaging equipment specifically refers to a SPECT device and a CT device. Firstly, the activity concentration of a calibration phantom with a known tracer activity needs to be measured and calculated in the first image domain by the medical imaging equipment. This process includes:

[0099] The calibration phantom is scanned using a SPECT device to acquire a SPECT rotational projection image, denoted as T1. T1 is the first functional image projection data. Simultaneously with acquiring the SPECT rotational projection image, the calibration phantom is scanned using a matching CT device to acquire a CT image of the calibration phantom. This CT image is the first structural image data.

[0100] Then, a first attenuation correction parameter table is generated. Specifically, the CT images (first structural image data) acquired in the aforementioned steps are converted and processed to obtain an attenuation correction table, denoted as u1. This u1 is the first attenuation correction parameter table. Then, an iterative tomographic reconstruction algorithm is used, specifically the OSEM tomographic reconstruction algorithm in this embodiment, to perform tomographic reconstruction on the SPECT rotational projection image T1 acquired in the aforementioned steps. During the reconstruction process, according to the attenuation correction table u1, exponential attenuation correction is performed on the projection data to finally obtain the three-dimensional volume data of the calibration phantom, denoted as R1. The matrix size of the three-dimensional volume data R1 is usually a cube of 256×256×256 or 128×128×128, which can be determined according to the imaging accuracy and data processing capability of the medical imaging equipment.

[0101] After completing the above steps, further three-dimensional volume data signal processing is required. Specifically, a signal threshold is set, and data with pixel values ​​greater than the signal threshold in the three-dimensional volume data R1 are determined to be valid signals, while data with pixel values ​​less than or equal to the signal threshold are determined to be noise outliers, i.e., noise signals. These noise outliers are then removed to complete the noise removal operation. For the valid signal regions retained after noise removal, morphological closing operations are used to repair connected components, filling in small holes and repairing broken contours within the valid signal regions. Finally, a binary image that can clearly segment the contour of the calibration phantom is obtained. This binary image is the binarized mask image, denoted as Mask1.

[0102] Based on the binarized mask image Mask1, the signal values ​​of all pixels within the defined calibrated phantom contour are extracted from the three-dimensional volume data R1, and the sum of these pixel signal values ​​is calculated. This sum is denoted as the total activity in the image domain, denoted as ImgA1.

[0103] Based on the calibration phantom volume V1 determined in step S101, the activity concentration in the first image domain is calculated using the following formula:

[0104] The activity concentration in the first image domain = total activity in the image domain / volume of the calibration phantom; that is, the specific expression is: Con1-2 = (ImgA1 / V1), where Con1-2 is the activity concentration in the first image domain, and this concentration value is the second activity concentration.

[0105] S103. A correction factor is calculated based on the first activity concentration and the second activity concentration. The correction factor is used to correct the absolute quantification of medical imaging equipment.

[0106] The calculation of the correction factor based on the first activity concentration and the second activity concentration includes: calculating the correction factor using the formula Correction Factor = Second Activity Concentration / First Activity Concentration; the correction factor is used to characterize the correspondence between the image domain activity concentration and the actual activity concentration of the medical imaging device. Specifically, the formula can also be expressed as: Calib = Con1-2 / Con1-1, where Calib represents the correction factor.

[0107] In practical applications, the correction factor, through preset configuration and automatic invocation, enables real-time correction of device measurement data. The specific operation process and application effects are as follows:

[0108] ① Real-time correction mechanism: The correction factor is written into the system software's configuration file. During SPECT absolute quantitative analysis, the system software automatically calls the correction factor to convert the original count data: Corrected radioactivity concentration = original count rate × correction factor. After correction, accurate conversion from image counts to actual radioactivity is ensured, providing a basis for absolute quantification.

[0109] ② Multi-scenario adaptation: For different imaging conditions (such as different radionuclides, probe models, collimator types, and energy window settings), multiple sets of calibration parameters can be preset, and the system will adjust the calibration parameters according to the current scanning protocol (such as using...). 99 The system automatically matches the optimal correction factor (ᵐTc or ¹²³I, low-energy high-resolution collimator or low-energy universal collimator) to ensure the consistency of quantitative results under different conditions.

[0110] ③ Periodic Validation: Long-term use of the equipment may lead to sensitivity drift (e.g., detector crystal aging, changes in electronic performance, and the influence of environmental temperature and humidity). Regular calibration using a calibration model is necessary (e.g., monthly) to update the correction factors and ensure the long-term stability of absolute quantitative accuracy. Failure to update the correction factors over a long period will cause hardware drift, leading to a gradual increase in the deviation of quantitative results (e.g., the error may exceed 10% after 6 months), which can affect physician judgment (e.g., misdiagnosing low-activity lesions as high-activity lesions). Periodic validation and factor updates allow for real-time tracking of equipment performance changes, ensuring that the correction factors remain "effective," maintaining the long-term stability of the equipment's absolute quantitative accuracy, and providing continuous assurance for the reliability of clinical diagnosis.

[0111] The above embodiments detail the entire process of calibrating medical imaging equipment (such as SPECT equipment) using a calibration phantom and then calculating the correction factor. This correction factor can initially ensure the quantitative accuracy of the equipment through mechanisms such as real-time calibration and multi-scenario adaptation. However, to further verify the applicability of the correction factor in complex structural measurement scenarios and ensure that it can not only adapt to the regular cylindrical structure of the calibration phantom but also play a role in scenarios that are closer to the clinical lesion morphology (such as irregular, multi-sized lesions), the calibration method of this application needs to introduce a measurement phantom for subsequent verification or application after calculating the correction factor. The specific steps and measurement phantom structure are as follows.

[0112] After calculating the correction factor, a pre-designed measurement phantom needs to be obtained. The structural parameters and material selection of the measurement phantom are specifically designed to simulate common lesion distributions and tissue environments in clinical practice. Furthermore, the structure of the measurement phantom differs from that of the calibration phantom. Specifically, the calibration phantom is a regular cylindrical structure (100mm radius, 100mm height), primarily used to establish a basic correspondence between the measured values ​​and actual values. The measurement phantom, however, has a more complex structure and is closer to clinical reality, primarily used to verify the correction effect of the correction factor in irregular structure measurement scenarios, or to further optimize the quantitative accuracy of the equipment for multi-size, specifically distributed targets.

[0113] The detailed structural composition of the measuring phantom is described below, such as... Figure 3 As shown, Figure 3 This is a schematic diagram of a measuring phantom provided in an embodiment of this application. The measuring phantom is a composite structure with multiple components working together. The whole includes a main body, a cover, a connecting structure, and four spheres. The structural form, material selection, and parameter specifications of each component are as follows:

[0114] The main body of the measurement phantom is a three-quarter sphere structure. This design differs from the cylindrical shape of the calibration phantom, and the combination of open and closed features of the three-quarter sphere facilitates subsequent tracer injection and the installation and adjustment of the internal spheres. The phantom is made of polytetrafluoroethylene (PTFE), which has excellent chemical stability and low radioactive absorption characteristics. This avoids excessive attenuation of tracer photons by the material itself, ensuring that the measurement data accurately reflects the activity concentration of the spheres and more closely resembles the photon attenuation pattern of human tissue in clinical settings. Furthermore, the phantom is hollow inside, with the hollow cavity used to fill the tracer. The sphere wall thickness is 2mm, ensuring structural strength to support the internal components while avoiding photon attenuation interference caused by excessively thick sphere walls, thus ensuring measurement accuracy.

[0115] The cap is fitted into the quarter-opening of the main body to seal the hollow cavity. Specifically, the three-quarter spherical structure of the main body forms a quarter-spherical opening, and the shape of the cap perfectly matches this opening. This ensures no leakage after the hollow cavity is filled with tracer, preventing concentration changes due to tracer loss and providing a seal to guarantee the accuracy of subsequent measurement data. The connecting structure is a cylindrical structure designed to stably fix the four spheres in specific positions inside the main body. One end of the cylinder is fixedly connected to the side of the cap facing inwards from the main body, and after connection, it must extend along the center of the spheres in the main body. This installation direction ensures that the spheres subsequently fixed to the connecting structure can be symmetrically or at specific distances with the center of the spheres in the main body as a reference, simulating the distribution pattern of lesions relative to the center of organs in clinical practice. The specific diameter and length of the cylinder need to be determined according to the radius of the spheres in the main body and the installation requirements of the spheres to ensure that the spheres will not collide with the spherical wall of the main body after fixing, and can be located in the central area of ​​the hollow cavity of the main body, ensuring that the tracer can uniformly coat the spheres.

[0116] The four spheres are key components of the measurement phantom, simulating lesions of different sizes in clinical practice. Each sphere is designed as a spherical structure to simulate round or near-round lesions, such as pulmonary nodules and liver metastases. The diameters of the four spheres differ, measuring 17mm, 20mm, 28mm, and 30mm respectively. This size range covers common small to medium-sized lesions in clinical practice, allowing verification of the quantitative correction effect of the correction factor on lesions of different sizes. Furthermore, all four spheres are fixed at the end of the connecting structure furthest from the cover, with a key positional parameter of 28mm between the center of each sphere and the center of the main body. This design ensures that the four spheres are evenly distributed within the main body, avoiding measurement interference caused by overly concentrated sphere positions. This more realistically simulates the scenario of multiple lesions distributed in clinical settings, providing diverse measurement targets for subsequent verification of the universality of the correction factor.

[0117] The detailed structure of the measurement phantom has been described above. Based on this, after obtaining the measurement phantom, further follow-up procedures are needed to verify the effectiveness of the correction factor. The specific follow-up steps are as follows:

[0118] The tracer is injected into the hollow cavity of the main body of the measurement phantom. After the tracer is evenly distributed in the cavity, the actual activity concentration of the tracer in the cavity is defined as the third activity concentration, denoted as Con2-1. The fourth activity concentration is set for the four spheres of the measurement phantom, and its core is determined based on the preset ratio of the third activity concentration. The specific definition and calculation are as follows:

[0119] The actual activity concentration of the tracer injected into the four spheres of the measurement phantom is uniformly defined as the fourth activity concentration, denoted as Con2-2. This fourth activity concentration is not independently and randomly set, but is determined based on the third activity concentration within a preset activity concentration ratio. In one implementation of this application, the tracer is injected at an activity concentration ratio of 8:1 between the cavity and the spheres. The purpose of this setting logic is to simulate the real-world scenario where there is a difference in activity concentration between the lesion (sphere) and the surrounding tissue (main cavity) in clinical practice, and to more comprehensively verify the correction effect of the correction factor on different concentration regions.

[0120] Then, data is acquired and calculated from the measurement phantom using medical imaging equipment to obtain the activity concentration of the spheres in the second image domain of the measurement phantom. The specific process is as follows:

[0121] Data acquisition is performed on a measurement phantom injected with a second known tracer activity using the medical imaging equipment. The second known tracer activity represents the activity of the tracer injected into the measurement phantom. After acquisition by the medical imaging equipment, the second functional image projection data of the measurement phantom, i.e., the SPECT rotational projection map, denoted as T2, is obtained. This data reflects the radioactive distribution information of the tracer in the sphere. It is also combined with the second structural image data, i.e., the CT tomographic image, denoted as CT2, to reflect the geometric structure and tissue attenuation characteristics of the measurement phantom, providing a basis for subsequent attenuation correction.

[0122] Then, the second structural image data CT2 acquired in the above steps is imported into the image processing system of the device. Based on the correspondence between the gray value of the CT image and the material attenuation coefficient (such as the attenuation coefficient library of soft tissue and phantom material), CT2 is converted into a second attenuation correction parameter table for functional image reconstruction, denoted as u2.

[0123] An iterative tomographic reconstruction algorithm is adopted. In this embodiment, the OSEM algorithm is preferred. To ensure technical continuity, it is consistent with step S102. Tomographic reconstruction is performed on the second functional image projection data T2. During the reconstruction process, the second attenuation correction parameter table u2 is called in real time to perform exponential attenuation correction. Finally, the three-dimensional volume data of the measurement phantom containing complete information of the sphere is obtained and denoted as R2. Its matrix size can be set to 256×256×256 to ensure that the details of the sphere are clearly presented.

[0124] Then, a first signal threshold is set, and signal filtering is performed on the three-dimensional volume data R2. Specifically, the portion of R2 with pixel values ​​greater than the first signal threshold is retained and determined as a valid signal, i.e., a signal region that may contain the sphere; the portion of R2 with pixel values ​​less than or equal to the first signal threshold is removed and determined as noise signals, such as equipment electronic noise or ambient background noise. This operation initially eliminates the interference of noise on the positioning of the sphere region.

[0125] To accurately locate the area where the sphere is located and avoid interference from the cavity background signal, the volume of interest (VOI) of the sphere needs to be determined using a point spread function. First, the point spread function needs to be calculated. Along a preset coordinate axis (usually the Z-axis of the 3D volume data, i.e., the tomographic direction of the device scan), the point spread function (PSF) is calculated on the 3D volume data R² after noise reduction. This function reflects the spatial distribution of the sphere signal, with its peak position corresponding to the layer where the sphere signal is strongest. Next, the central layer and adjacent layers are selected: the tomographic layer corresponding to the peak position of the point spread function is defined as the central layer of the sphere in the measurement phantom. Then, a preset number of adjacent layers are selected on both sides of this central layer, such as 3 layers above and below the central layer, for a total of 7 layers. The specific number can be adjusted according to the diameter of the sphere to ensure complete coverage. The 3D region formed by these layers is defined as the volume of interest (VOI) of the sphere.

[0126] More refined signal processing is performed on the volume of interest (VOI) to clearly segment the contours of the sphere and cavity: Based on the grayscale difference between the sphere signal and the cavity background signal within the VOI, a second signal threshold is set, and regions in the VOI with pixel values ​​greater than the second signal threshold are retained. These regions are the initially segmented sphere regions. Morphological closing operations are used to perform connected component repair on the segmented sphere regions, filling in tiny holes and connecting broken edges within the sphere regions. Finally, a binary mask image of the sphere (Mask2) containing only the sphere contour is obtained. In this image, the sphere region is 1 and the background region is 0, which can accurately define the position of the sphere in the 3D volume data.

[0127] Based on the centroid localization algorithm, the image coordinates of each sphere in the binary mask image (Mask2) are calculated, that is, the center point coordinates in the pixel coordinate system. Then, combined with the image-physical coordinate transformation parameters of the medical imaging equipment, such as the actual physical size corresponding to each pixel, the image coordinates are converted into physical coordinates to ensure that the subsequently extracted signals correspond to the real spherical regions.

[0128] Extracting the pixel signal sum: Based on the preset size parameters of the spheres in the measurement phantom (e.g., diameter 17mm, 20mm, etc.), and combined with the transformed physical coordinates, accurately extract all pixels corresponding to each sphere in the 3D volume data R2, and calculate the sum of the signal values ​​of these pixels, denoted as the pixel signal sum Img(i) corresponding to the sphere, where i represents the i-th sphere, i=1,2,3,4. Combining the preset volume parameters of the spheres, calculate the activity concentration in the second image domain of the spheres using the following formula: First, calculate the volume V(i) of a single sphere based on the sphere diameter, where i represents the i-th sphere, i=1,2,3,4; then calculate using the following formula: Image domain activity concentration of the spheres in the measurement phantom = Sum of pixel signals corresponding to the sphere / Sphere volume, i.e., the specific expression is: Con2-3 i=Img(i) / V(i), where Con2-3 i Let be the activity concentration in the second image domain of the i-th sphere.

[0129] Since the cavity of the measuring phantom contains multiple spheres (four in this embodiment), the rationality of the correction factor needs to be comprehensively judged based on the measurement results of multiple spheres. The specific rules are as follows:

[0130] The activity concentrations in the second image domain of each sphere, which are injected with a second known tracer activity, are acquired and calculated on a medical imaging device and defined as multiple fifth activity concentrations, denoted as Con2-31, Con2-32, Con2-33, and Con2-34, corresponding to four different spheres.

[0131] Correct multiple fifth activity concentrations separately, using the correction factor Calib calculated in step S103, and apply the correction formula Con2-3. i -new=Con2-3 i / Calib, Con2-3 i -new represents the corrected i-th fifth activity concentration. Each fifth activity concentration is corrected according to the above formula to obtain multiple corrected fifth activity concentrations, denoted as Con2-31-new, Con2-32-new, Con2-33-new, and Con2-34-new.

[0132] A preset difference threshold is set to verify the difference between the corrected fifth activity concentration and the uncorrected fifth activity concentration. This preset difference threshold, such as 5%, is set based on clinical requirements for quantitative accuracy of lesions of various sizes, ensuring that the measurement error of spheres with different diameters is within an acceptable range. When the differences between all corrected fifth activity concentrations Con2-31-new, Con2-32-new, Con2-33-new, and Con2-34-new and the fourth activity concentration (Con2-2), and the preset actual activity concentrations of all spheres, all satisfy Con2-3... i When −Con2-2 < 5%, it indicates that the correction factor can not only adapt to spheres of a single size, but also achieve accurate correction for spheres of different diameters. Therefore, the correction factor is considered reasonable and can be used for absolute quantitative correction of lesions of multiple sizes in clinical practice. If there exists a difference between any corrected fifth activity concentration and fourth activity concentration that satisfies Con2-3... iIf −Con2-2≥5%, it indicates that the current correction factor cannot be adapted to all sizes of spheres. This may be due to the weaker signal of small-sized spheres and the difference in attenuation of large-sized spheres, which may lead to correction deviation. In this case, the correction factor needs to be reset and steps S101-S103 need to be re-executed. The structure of the calibration phantom can be adjusted, such as by adding multi-sized sub-body or optimizing the reconstruction parameters. A new correction factor can be calculated until the corrected concentration of all spheres meets the difference threshold requirement.

[0133] This implementation method ensures the accuracy of activity concentration calculation in the spherical image domain through refined steps such as two signal screenings, point spread function localization, and centroid coordinate transformation. At the same time, the verification rules for multi-sphere scenarios avoid the randomness that may exist in single-sphere verification, ensuring that the correction factor has universal applicability in the measurement of lesions of multiple sizes in clinical practice, and further enhancing the reliability of absolute quantitative correction of medical imaging equipment.

[0134] The above are some specific implementations of an absolute quantitative correction method for medical imaging equipment provided in the embodiments of this application. Based on this, this application also provides a corresponding device. The device provided in the embodiments of this application will be described below from the perspective of functional modularity.

[0135] Figure 4 This is a schematic diagram of the structure of an absolute quantitative correction device for a medical imaging equipment provided in an embodiment of this application. (Combined with...) Figure 4 As shown in the embodiment of this application, the absolute quantitative correction device 400 for medical imaging equipment includes:

[0136] The first acquisition unit 410 is used to take the actual activity concentration of the calibration phantom injected with the first known tracer activity as the first activity concentration;

[0137] The second acquisition unit 420 is used to take the activity concentration of the calibration phantom with the injected first known tracer activity in the first image domain acquired and calculated by the medical imaging equipment as the second activity concentration.

[0138] The calculation unit 430 is used to calculate a correction factor based on the first activity concentration and the second activity concentration, the correction factor being used to correct the absolute quantification of the medical imaging equipment.

[0139] In one implementation of this application, the apparatus further includes a verification unit, which is used to calculate the correction factor and then obtain a pre-designed measurement phantom, the structure of which is different from that of the calibration phantom.

[0140] The tracer activity concentration injected into the cavity of the measuring phantom is taken as the third activity concentration, and the tracer activity concentration injected into the sphere of the measuring phantom is taken as the fourth activity concentration; the fourth activity concentration is set based on the third activity concentration at a preset activity concentration ratio;

[0141] The activity concentration of the spheres in the measurement phantom with the injected second known tracer activity is obtained by acquiring and calculating the data using a medical imaging device, and is taken as the fifth activity concentration.

[0142] The fifth activity concentration is corrected based on the correction factor to obtain the corrected fifth activity concentration;

[0143] If the difference between the corrected fifth activity concentration and the fourth activity concentration is less than a preset difference threshold, the correction factor is considered reasonable.

[0144] If the difference between the corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0145] In one implementation of this application, the measurement phantom includes multiple spheres. The verification unit uses the measurement phantom with injected second known tracer activity to acquire and calculate the activity concentration of the spheres in the measurement phantom in the second image domain of the measurement phantom as the fifth activity concentration, which includes:

[0146] The activity concentration of each sphere in the measurement phantom with the injected second known tracer activity is acquired and calculated by a medical imaging device and used as multiple fifth activity concentrations.

[0147] The plurality of fifth activity concentrations are corrected based on the correction factor to obtain a plurality of corrected fifth activity concentrations;

[0148] If the differences between the plurality of corrected fifth activity concentrations and the fourth activity concentration are all less than a preset difference threshold, then the correction factor is considered reasonable.

[0149] If the difference between any corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

[0150] In one implementation of this application, the device further includes a calculation unit for the actual activity concentration of the calibration phantom, used to calculate the actual activity concentration of the calibration phantom. The calculation process is as follows:

[0151] The volume of the calibration phantom is obtained, and the actual activity concentration of the calibration phantom is calculated based on the volume of the calibration phantom and the activity of the first known tracer.

[0152] In one implementation of this application, the device further includes an activity concentration calculation unit in the first image domain, used to acquire first functional image projection data and first structural image data obtained after data acquisition is performed on a calibration phantom injected with a first known tracer activity by the medical imaging device;

[0153] A first attenuation correction parameter table is generated based on the first structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the first functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the first attenuation correction parameter table to obtain the three-dimensional volume data of the calibration phantom.

[0154] Set a signal threshold, retain valid signals in the three-dimensional volume data that are greater than the signal threshold, and remove noise signals that are less than or equal to the signal threshold;

[0155] Morphological closing operations are used to perform connected component repair on the effective signal region to obtain a binary mask image that can clearly segment the outline of the calibration phantom.

[0156] Based on the binary mask image, the sum of pixel signals corresponding to the calibrated model is extracted from the three-dimensional volume data and denoted as the total activity in the image domain.

[0157] The activity concentration in the first image domain is calculated using the formula: Activity concentration in the first image domain = Total activity in the image domain / Volume of the calibration phantom.

[0158] In one implementation of this application, the calculation unit is specifically used to calculate the correction factor using the formula correction factor = second activity concentration / first activity concentration; the correction factor is used to characterize the correspondence between the image domain activity concentration and the actual activity concentration of the medical imaging device.

[0159] In one implementation of this application, the device further includes: an image domain activity concentration calculation unit for spheres in a measurement phantom, specifically used to: acquire second functional image projection data and second structural image data of the measurement phantom obtained by performing data acquisition on a measurement phantom injected with a second known tracer activity through the medical imaging device;

[0160] A second attenuation correction parameter table is generated based on the second structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the second functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the second attenuation correction parameter table to obtain the three-dimensional volume data of the measurement phantom.

[0161] A first signal threshold is set, and valid signals in the three-dimensional volume data that are greater than the first signal threshold are retained, while noise signals that are less than or equal to the first signal threshold are removed.

[0162] The point spread function of the three-dimensional volume data is calculated along the preset coordinate axis direction. The layer corresponding to the peak position of the point spread function is taken as the center layer of the sphere in the measurement model. A preset number of adjacent layers on both sides of the center layer are selected to jointly constitute the volume of interest of the sphere.

[0163] A second signal threshold is set, and regions in the volume of interest that are greater than the second signal threshold are retained to segment the contours of the sphere and the measurement phantom cavity. Morphological closing operation is used to perform connected component repair on the segmented contours to obtain a binary mask image of the sphere.

[0164] The image coordinates of each sphere in the binary mask image are calculated based on the centroid localization algorithm, and the image coordinates are converted into physical coordinates.

[0165] Based on the preset size parameters of the spheres, the sum of pixel signals corresponding to each sphere is extracted from the three-dimensional volume data;

[0166] The image domain activity concentration of the sphere in the measurement phantom is calculated using the formula: Image domain activity concentration of the sphere = Sum of pixel signals corresponding to the sphere / Volume of the sphere.

[0167] This application also provides corresponding devices and computer storage media for implementing the solutions provided in this application.

[0168] The device includes a memory and a processor. The memory stores instructions or code, and the processor executes the instructions or code to enable the device to perform the absolute quantitative correction method for medical imaging equipment according to any embodiment of this application.

[0169] The computer storage medium stores code, and when the code is run, the device running the code implements the absolute quantitative correction method for medical imaging equipment described in any embodiment of this application.

[0170] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that all or part of the steps in the methods of the above embodiments can be implemented by means of software plus a general-purpose hardware platform. Based on this understanding, the technical solution of this application can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as a read-only memory (ROM) / RAM, magnetic disk, optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, a server, or a network communication device such as a router) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0171] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0172] It should also be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for the device and apparatus embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments. The device and apparatus embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components indicated as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0173] The above description is merely one specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An absolute quantitative calibration method for medical imaging equipment, characterized in that, The method includes: The actual activity concentration of the calibration phantom injected with the first known tracer activity is taken as the first activity concentration; The activity concentration of the calibration phantom with the injected first known tracer activity in the first image domain acquired and calculated by medical imaging equipment is used as the second activity concentration; A correction factor is calculated based on the first activity concentration and the second activity concentration, and the correction factor is used to correct the absolute quantification of medical imaging equipment. After the correction factor is calculated, the method further includes: A pre-designed measurement phantom is obtained, the structure of which differs from that of the calibration phantom. The tracer activity concentration injected into the cavity of the measuring phantom is taken as the third activity concentration, and the tracer activity concentration injected into the sphere of the measuring phantom is taken as the fourth activity concentration; the fourth activity concentration is set based on the third activity concentration at a preset activity concentration ratio; The activity concentration of the spheres in the measurement phantom with the second known tracer activity is acquired and calculated by a medical imaging device and used as the fifth activity concentration. The fifth activity concentration is corrected based on the correction factor to obtain the corrected fifth activity concentration; If the difference between the corrected fifth activity concentration and the fourth activity concentration is less than a preset difference threshold, the correction factor is considered reasonable. If the difference between the corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

2. The method according to claim 1, characterized in that, The measurement phantom includes multiple spheres, and the step of injecting a measurement phantom with a second known tracer activity into a medical imaging device and calculating the activity concentration of the spheres in the measurement phantom as a fifth activity concentration includes: The activity concentration of each sphere in the measurement phantom with the injected second known tracer activity is acquired and calculated by a medical imaging device and used as multiple fifth activity concentrations. The plurality of fifth activity concentrations are corrected based on the correction factor to obtain a plurality of corrected fifth activity concentrations; If the differences between the plurality of corrected fifth activity concentrations and the fourth activity concentration are all less than a preset difference threshold, then the correction factor is considered reasonable. If the difference between any corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

3. The method according to claim 1, characterized in that, The calculation process for the actual activity concentration of the calibration phantom includes: The volume of the calibration phantom is obtained, and the actual activity concentration of the calibration phantom is calculated based on the volume of the calibration phantom and the activity of the first known tracer.

4. The method according to claim 1, characterized in that, The process of calculating the activity concentration of a calibration phantom with injected first known tracer activity in the first image domain acquired by medical imaging equipment includes: After data acquisition is performed on a calibration phantom injected with a first known tracer activity using the medical imaging device, the first functional image projection data and the first structural image data are obtained. A first attenuation correction parameter table is generated based on the first structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the first functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the first attenuation correction parameter table to obtain the three-dimensional volume data of the calibration phantom. Set a signal threshold, retain valid signals in the three-dimensional volume data that are greater than the signal threshold, and remove noise signals that are less than or equal to the signal threshold; Morphological closing operations are used to perform connected component repair on the effective signal region to obtain a binary mask image that can clearly segment the outline of the calibration phantom. Based on the binary mask image, the sum of pixel signals corresponding to the calibrated model is extracted from the three-dimensional volume data and denoted as the total activity in the image domain. The activity concentration in the first image domain is calculated using the formula: Activity concentration in the first image domain = Total activity in the image domain / Volume of the calibration phantom.

5. The method according to claim 1, characterized in that, The correction factor calculated based on the first activity concentration and the second activity concentration includes: The correction factor is calculated using the formula Correction Factor = Second Activity Concentration / First Activity Concentration; the correction factor is used to characterize the correspondence between the image domain activity concentration and the actual activity concentration of the medical imaging device.

6. The method according to any one of claims 1 or 2, characterized in that, The method for calculating the activity concentration of the spheres in the measurement phantom in the second image domain is as follows: The second functional image projection data and the second structural image data of the measurement phantom are obtained by performing data acquisition on a measurement phantom injected with a second known tracer activity through the medical imaging equipment. A second attenuation correction parameter table is generated based on the second structural image data. An iterative tomographic reconstruction algorithm is used to perform tomographic reconstruction on the second functional image projection data. During the reconstruction process, exponential attenuation correction is performed based on the second attenuation correction parameter table to obtain the three-dimensional volume data of the measurement phantom. A first signal threshold is set, and valid signals in the three-dimensional volume data that are greater than the first signal threshold are retained, while noise signals that are less than or equal to the first signal threshold are removed. The point spread function of the three-dimensional volume data is calculated along the preset coordinate axis direction. The layer corresponding to the peak position of the point spread function is taken as the center layer of the sphere in the measurement model. A preset number of adjacent layers on both sides of the center layer are selected to jointly constitute the volume of interest of the sphere. A second signal threshold is set, and regions in the volume of interest that are greater than the second signal threshold are retained to segment the contours of the sphere and the measurement phantom cavity. Morphological closing operation is used to perform connected component repair on the segmented contours to obtain a binarized mask image of the sphere. The image coordinates of each sphere in the binary mask image are calculated based on the centroid localization algorithm, and the image coordinates are converted into physical coordinates. Based on the preset size parameters of the spheres, the sum of pixel signals corresponding to each sphere is extracted from the three-dimensional volume data; The image domain activity concentration of the sphere in the measurement phantom is calculated using the formula: Image domain activity concentration of the sphere = Sum of pixel signals corresponding to the sphere / Volume of the sphere.

7. The method according to claim 1, characterized in that, The calibration model is a cylinder with a radius of 100 mm and a height of 100 mm.

8. The method according to claim 1, characterized in that, The measuring phantom includes: a main body, which is a three-quarter spherical structure, made of polytetrafluoroethylene, and the interior of the main body is hollow with a spherical wall thickness of 2mm; The cover is fitted and installed at one-quarter of the opening of the main body to achieve a seal of the hollow cavity of the main body; The connecting structure is a cylinder, one end of which is fixedly connected to the side of the cover facing the interior of the main body and extends along the spherical center of the main body; Four spheres, each with a spherical structure, have diameters of 17mm, 20mm, 28mm, and 30mm, respectively. Each of the four spheres is fixed to the end of the cylinder away from the cover, and the distance between the center of each of the four spheres and the center of the main body is 28mm.

9. An absolute quantitative correction device for medical imaging equipment, characterized in that, The device includes: The first acquisition unit is used to take the actual activity concentration of the calibration phantom injected with the first known tracer activity as the first activity concentration; The second acquisition unit is used to take the activity concentration of the calibration phantom with the injected first known tracer activity in the first image domain acquired and calculated by the medical imaging equipment as the second activity concentration. A calculation unit is used to calculate a correction factor based on the first activity concentration and the second activity concentration, the correction factor being used to correct the absolute quantification of medical imaging equipment; The device further includes a verification unit, which is used to calculate the correction factor and then obtain a pre-designed measurement phantom, the structure of which is different from that of the calibration phantom. The tracer activity concentration injected into the cavity of the measuring phantom is taken as the third activity concentration, and the tracer activity concentration injected into the sphere of the measuring phantom is taken as the fourth activity concentration; the fourth activity concentration is set based on the third activity concentration at a preset activity concentration ratio; The activity concentration of the spheres in the measurement phantom with the second known tracer activity is acquired and calculated by a medical imaging device and used as the fifth activity concentration. The fifth activity concentration is corrected based on the correction factor to obtain the corrected fifth activity concentration; If the difference between the corrected fifth activity concentration and the fourth activity concentration is less than a preset difference threshold, the correction factor is considered reasonable. If the difference between the corrected fifth activity concentration and the fourth activity concentration is not less than a preset difference threshold, then the correction factor needs to be reset.

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