TWI554251B - The technique of quantitative analysis in bone spect imaging and its application in bone evaluation - Google Patents

Description

Quantitative analysis technique of SPECT bone imaging and its use in bone evaluation

The present invention relates to a quantitative analysis technique for bone images, in particular to a single photon emission computed tomography (SPECT) or single photon emission computed tomography/X-ray computed tomography ( SPECT/CT) image processing technology can measure the degree of uptake of nuclear medicine single photon bone imaging drugs in bones, and is represented by quantitative indicators, including: standardized uptake value of bone for imaging drugs. , SUV), standardized uptake lean body mass (SUL) and metabolic volume (MTV), and the use of this technique in bone evaluation.

Preventive medicine is the future development trend of the society and medical profession, especially the rapid increase of the elderly population. According to the statistics of the Ministry of Health and Welfare, the prevalence of knee joint degeneration is about 15%, and it is estimated that 3.5 million people suffer from knee pain. At the same time, people suffering from osteoporosis have also increased significantly year by year. Among the elderly people over 65 years old, 1 out of every 9 people suffer from osteoporosis; 1 out of every 4 women over 65 years old Suffering from osteoporosis; 40% of women over 50 years old have at least one fracture due to osteoporosis, and about 30,000 fractures due to osteoporosis each year, of which 5-25 due to various reasons %. Therefore, effective diagnosis and treatment of bone functional diseases has become an important medical service project to ensure the quality of life of the elderly population. In the clinical application of bone function assessment, positron emission tomography (PET) or positron emission computed tomography/PET/CT, etc. Medical imaging techniques, consistent use of SUV, SUL and MTV and other quantitative indicators for the measurement of the degree of bone target uptake with positron-positive imaging drugs (eg using NaF positron imaging drugs) to accurately assess the functional status of bone . The technique of bone imaging with SPECT has been frequently used to evaluate the functional activity of bone. Compared with PET and PET/CT bone imaging, although the technical method of SPECT has the characteristics of low cost and simple technology, Like the limitation of physical interference, the bone can only be evaluated qualitatively for the intake of imaging drugs, and it is impossible to accurately and quantitatively measure the intake of imaging drugs like PET or PET/CT. Therefore, SPECT bone imaging It is difficult to push into new application fields, which is a serious obstacle to the development of SPECT bone imaging.

In view of this, there is a need to develop an image quantitative analysis technique for bone SPECT and SPECT/CT imaging to achieve measurement of SUV, SUL and MTV quantitative indicators, and to be able to actually use quantitative indicators for bone evaluation.

The object of the present invention is to provide a quantitative analysis method of SUV, SUL and MTV of SPECT or SPECT/CT bone to overcome the defects that traditional SPECT and SPECT/CT techniques can only be qualitatively and cannot be quantitatively analyzed, and apply this new technology. Evaluation of the bone.

The technical means adopted by the present invention is a new technical method for measuring bone SUV, SUL and MTV by SPECT or SPECT/CT, which comprises: (1) image acquisition step, using SPECT or SPECT/CT to collect images of patients with bone diseases (2) radionuclide physical decay correction step, correcting the physical attenuation (isotope decay) of the image according to the rotation time of the SPECT probe and the half-life of the nuclide; (3) the scattering correction step, using the scattering energy window, in the image The scatter component is calculated, and the scatter component image is subtracted to obtain a scatter correction image; (4) the motion correction step includes automatically re-pairing by means of inter-scan patient motion between calibration scans Bit CT and SPECT image; (5) Tissue attenuation correction step, establish a tissue attenuation matrix by converting CT image or radioactive source transmission image, reconstructed by iterative method to remove image due to attenuation of human tissue Like the underestimation of the amount of drug intake; (6) the image spatial resolution recovery step, measuring the distance spread function related to the distance in the projected image by moving the point source to the surface of the collimator. PSF), and the establishment of the point-spread function matrix, and the point spread function matrix for iterative image reconstruction restored spatial resolution; (7) the noise removal step, by analyzing (Analytic) or wavelet (Wavelet) with filter In the iterative image reconstruction, to remove the noise in the image; (8) the bone metabolism volume calculation step, calculate the physical correction according to the linear relationship between the actual measured radioactive concentration and the pixel intensity in the image The bone imaging drug uptake concentration (unit: Bq/ml) of each pixel in the image, and the calculation of the coordinate system and the concentration gradient by the coordinate system, and the threshold value is used to calculate the bone metabolism volume in the “region of interest”; The standard intake value calculation step, based on the patient's weight and height, and the patient's radioactive injection dose, calculate the quantitative intake index of the bone for the drug, including SUV and SUL; (10) the evaluation step, through the quantitative indicator to determine the amount of change Changes that occur before and after bone treatment.

Through the technical means adopted by the present invention, the problem of quantitatively measuring the bone standard uptake value by SPECT and SPECT/CT is solved, and the technique can be used for the evaluation of bone injury.

Illustration one

Figure 5 shows one case of the patient's bone SPECT and CT in patients with left foot orthopedic knee fused image, used in SPECT imaging is ^99m Tc-labeled radionuclide ^99m Tc-MDP bone imaging agent is injected dose 22.0mCi, It weighs 65 kilograms and is 160 centimeters tall. According to the present invention, after the image is physically corrected, the right knee tibia and the left knee tibia can be seen at the end of the measurement, and the SUVmax and SULmax values of the right knee tibia end are 19.01 and 14.02, respectively, SUVmean and SULmean. The SUVmax and SULmax values of the end of the right knee tibia were 17.80 and 13.69, the SUVmean and SULmean values were 11.76 and 9.05, respectively, and the MTV was 9.25 ml, respectively, 11.46 and 8.81 for MTV and 7.12 ml for MTV.

Illustration two

Figure 6 shows a patient with a right ankle joint bone injury, weighing 60 kg, height 171 cm, pre-treatment patients receiving ^99m Tc-MDP SPECT bone imaging, ^99m Tc-MDP injection dose of 24.8mCi, using the present technology, treatment The concentration of ^99m Tc-MDP high uptake was observed in the front right tibia. The MTV was 6.20ml, the SUVmax and SULmax values were 11.75 and 9.97, respectively, and the SUVmean and SULmean values were 8.35 and 5.01, respectively. After four months of treatment with TCM, the patient was again reviewed with ^99m Tc-MDP SPECT bone imaging. The ^99m Tc-MDP injection dose was 20.8mCi. The change of SUVmax and SULmax values were 6.87 and 5.83, respectively. The SUVmean and SULmean values were 7.20 and 4.32, respectively, and the MTV was 3.32 ml. Before and after treatment, the MTV of the bone was reduced by 46.5%, the consistency of SUVmax and SULmax was reduced by 41.5%, the consistency of SUVmean and SULmean was decreased by 13.7%, and the clinical pain assessment was reduced from 6 to 1 point. The degree of pain has been greatly improved, so it is considered that the quantitative indicators before and after the treatment of bone injury are meaningful.

1. Figure 1 shows a flow chart of a scan shift patient movement correction step in accordance with an embodiment of the present invention.

2. Figure 2 shows a schematic diagram of the tissue attenuation matrix of a patient obtained in accordance with the practice of the present invention.

3. Figure 3A shows an image without correction in the practice of the present invention.

4. Figure 3B shows an image removed by noise in the practice of the present invention.

5. Figure 3C shows an image corrected by noise removal and scatter correction in the practice of the present invention.

6. Figure 3D shows an image of noise removal, scatter correction, unscanned patient movement correction, tissue attenuation correction in the practice of the present invention.

7. Figure 3E shows an image of noise removal, scatter correction, inter-scan patient motion correction, tissue attenuation correction in the practice of the present invention.

8. Figure 3F shows an image of noise removal, scatter correction, inter-scan patient motion correction, tissue attenuation correction, spatial resolution correction, and radionuclide physical decay correction in the practice of the present invention.

9. Figure 4 is a flow chart showing the steps of performing a bone metabolism volume calculation in accordance with the present invention.

10. Figure 5 shows that the SUVmax and SULmax values of the right tibia end of the right knee of the patient with a bone injury according to the present invention are 19.01 and 14.02, respectively, and the SUVmean and SULmean values are 11.46 and 8.81, respectively, and MTV is 7.12 ml (ml). The SUVmax and SULmax values of the distal end of the right knee tibia were 17.80 and 13.69, respectively, and the SUVmean and SULmean values were 11.76 and 9.05, respectively, and the MTV was 9.25 ml.

11. Figure 6 shows the results of comparison of quantitative indicators before and after treatment of a right ankle in patients with a bone injury according to the present invention. It can be found that MTV (front: 6.20 ml; after: 3.32 ml) is reduced by 46.5%, SUVmax (pre: 11.75) After: 6.87) and SULmax (pre: 9.97; after: 5.83) consistency reduced by 41.5%, SUVmean (front: 8.35; after: 7.20) and SULmean (front: 5.01; after: 4.32) consistency decreased by 13.7% .

The invention provides an image quantitative analysis technology for bone imaging, which can obtain quantitative indicators of bone drug intake for ^99m Tc-HDP or ^99m Tc-MDP imaging, including SUV, SUL and MTV. These quantitative indicators can only be used in PET. Obtained in PET/CT bone imaging (for example using NaF positron imaging drugs), but also in SPECT or SPECT/CT by the new technique of the invention.

First, in the image acquisition step, the bone image of the patient is acquired using SPECT or SPECT/CT. About 4 hours after the patient was injected with ^99m Tc-labeled ^99m Tc-HDP or ^99m Tc-MDP bone imaging drug, the dual probes that started SPECT or SPECT/CT were rotated 180 degrees each to collect image data. During rotation, the original image data is represented by space coordinates and rotation angle. The probe can be rotated from the right front oblique position to the left rear oblique position, the front position to the rear position, the left front oblique position to the right rear oblique position, and the rear position to the front position. The acquisition step further includes using a common 128×128 matrix or a high-definition 256×256 matrix, rotating the 180° angle, circular or non-circular rotating orbit, dual-energy window (main peak + scattering energy window), and collecting the total time to 20 -30 minutes. The collected data can be saved or transmitted using standard digital imaging and communications in medicine (DICOM) formats for subsequent image processing.

The physical decay correction step corrects the physical decay of the image based on the rotation time of the probe and the half-life of the nuclide. When the SPECT rack is wrapped around the patient, the calculation is performed at the time point corresponding to the rotation angle to indicate The exponential decay model calculates the correction factor to re-adjust the counts of the radioactivity in the original projected image.

The patient moves the calibration step to correct the inter-scan patient motion. Patient movement between scans is the SPECT and CT misalignment caused by the patient's movement of the body position between SPECT and CT image acquisition, thus affecting the accuracy of subsequent tissue attenuation corrections. Inter-scan patient motion correction uses the patient's CT image to map the image to the bone and non-bone regions with multiple thresholds using Hournsfield Unit's high degree of difference between bone and other tissues, and from the CT map. In the image, the non-bone area is removed and only the bone area is preserved. The reconstructed SPECT image is automatically overlapped with the CT image by automatic movement and rotation, and the SPECT and CT images are automatically aligned to correct the patient between the scans. Movement, wherein the correction includes using a displacement direction (x, y, z) and an angular direction (σ, δ, θ) of a total of 6 dimensions. Figure 1 shows a flow chart for automatically correcting patient movement between scans.

The scatter correction step uses a scattering image of the original image and the scattering energy window (118 ± 12% keV or 110-125 keV) with an independent peak energy window (140 ± 10% kev or 126-154 keV), through the scattering component and the main peak The triangular approximation of the energy window estimates the scattered component in the original image and subtracts the scattered component from the original image for scatter correction.

The tissue attenuation correction step calculates the 140 keV attenuation coefficient of each primitive unit in the image by converting the CT image or the radioactive source transmission image, and adopts an exponential model and a line integral through the position of the image corresponding to the probe. (linear integration) calculating an attenuation matrix for each primitive unit corresponding to the attenuation value of the probe, The attenuation matrix is used to correct the tissue attenuation in the iterative reconstruction. The attenuation matrix records the amplitude of the photon attenuation of each corresponding line with four parameters (x, y, z, Θ) (Fig. 2). As described above, the patient movement between the SPECT and the CT scan is completed before the tissue attenuation correction, and the correct alignment of the two images is performed to improve the accuracy of the tissue attenuation correction.

The image spatial resolution recovery step establishes a point spread function (PSF) related to the distance of the collimator by using a full width of half max of the moving point source in the original projection data. The point spread function matrix is used and the point spread function matrix is used for iterative reconstruction to restore the spatial resolution of the image. For configuring different models of SPECT and SPECT/CT, a set of PSF matrices can be measured separately. The PSF can be modeled by means of analytical functions. The PSF matrix can then be used in the pre-projection step in the iterative reconstruction to recover the spatial resolution of the image by iterative.

The noise removal step applies an analytic or wavelet filter to the iterative integrated reconstruction to remove noise from the image. The image noise is filtered by the equivalent analytic filter in the step of comparing the filtered original image and the front projected image in the iterative reconstruction. As an alternative, the noise of the original image and the front projected image may also use a wavelet filter in the iterative reconstruction process, as well as in the iterative reconstruction in comparing the filtered original image and the front projected image. In the step, the noise is filtered, wherein the wavelet filter performs the base expansion of the image in a stationary mode, and the high-frequency expansion coefficient is excluded by the fixed window width in the expansion coefficient bar graph of different levels. And use analytic functions to expand The coefficients are filtered and then image recombined. 3A to 3F respectively show images of the patient without physical correction (Fig. 3A); images removed by noise (Fig. 3B), showing effective removal of image noise; noise removal, scatter correction image ( Figure 3C) shows an image that further enhances image contrast; images that are corrected by noise removal, scatter correction, tissue attenuation correction, but not corrected by patient movement (Fig. 3D), showing left and right asymmetry and artifacts of the image generated by patient movement Image with noise removal, scatter correction image, tissue attenuation correction, and patient motion correction (Fig. 3E), showing that the left and right bones of the image are symmetrical and uniform; noise removal, scatter correction, tissue attenuation Correction, patient motion corrected images, spatial resolution recovery, and complete physical correction of the radionuclide physical decay (Fig. 3F) show improved image contrast and resolution, with significant improvements in quality.

In the bone metabolism volume calculation step, in order to calculate the uptake value and range of the bone imaging agent in the patient using the physically corrected image, a linear relationship between the actual radioactive concentration and the pixel intensity in the image is obtained according to the prosthesis model experiment. The unit of radioactive concentration is (Bq/ml). This experiment is obtained by injecting a radionuclide solution of known ^99m Tc radioactivity concentration into the prosthesis model and comparing it with the reconstructed model image to obtain this linear relationship. For measurement, the experiment was performed using a model of a prosthetic structure. The bone metabolism volume is calculated by using the pixel with the maximum ingestion concentration in the "region of interest" as the reference point, and the image region is converted from the general Cartesian coordinate system to the spherical coordinate, and the image is in the r (radius) direction. The gradient of the concentration change is calculated, and the region representing the metabolic volume in the "region of interest" is delineated by the threshold range of the gradient, and the region of the metabolic volume is converted to the Cartesian coordinates via the spherical coordinates to calculate the bone metabolism in the "region of interest". Volume, volume units are expressed in ml (ml), and Figure 4 shows the calculation flow of bone metabolism volume.

The calculation step of the bone uptake value, the calculation of the bone standard uptake value is based on the above linear relationship and the bone metabolism volume to calculate the maximum and average drug intake concentration corresponding to the "region of interest" in the physically corrected image, and according to the patient Body weight, height, and dose of imaging agent (in Bq or mCi), calculate the patient's bone SUV and SUL, SUV is defined as the "region of interest" bone radioactivity concentration (Bq / ml) × patient weight ( g) / injection dose (Bq); SUL is defined as the "region of interest" bone radioactivity concentration (Bq / ml) × patient lean body weight (g) / injection dose (Bq), which lean body weight in Boer (Boer ) Formula, based on height, weight and gender. Of course, the present invention is not limited thereto, and the bone uptake value may be adjusted according to other physiological parameters of the patient, for example, using the osteoporosis of the patient to adjust the standard uptake value of the bone.

The evaluation step calculates the MTV, SUVmax, average SUV (SUVmean), SULmax, average SUL (SULmean), etc. based on the physically corrected image, the patient's weight, the lean body weight, and the intravenous dose of the imaging agent. A quantitative indicator. Before the treatment of the bone injury, draw an appropriate volume of the "region of interest" (this sensitive region must include the maximum standard uptake value), and then calculate the MTV, SUVmax, SUVmean, SULmax and SULmean. After treatment, if the SUVmax and SULmax, SUVmean and SULmean and MTV decreased more than a certain proportion, it is considered that the changes before and after the treatment of bone injury are meaningful.

Claims (9)

A quantitative detection technique method for bone images, in particular, a technical method for quantitatively measuring bone uptake by SPECT or SPECT/CT, the quantitative indicators including standard uptake value, standard body lean value and bone metabolism volume, and the technical method in bone For the purpose of evaluation, the technical method comprises: an image acquisition step, using the SPECT or SPECT/CT to collect an image of a patient with a bone injury; a radionuclide physical decay correction step, correcting the rotation time according to the SPECT probe and the half life of the nuclide a physical attenuation of the SPECT image; a scatter correction step of calculating a scatter component in the SPECT image using a scatter energy window, and subtracting the scatter component image to obtain a scatter correction image; and a motion correction step including a calibration scan Inter-patient movement to automatically re-align the CT and SPECT images; tissue attenuation correction step, establish a tissue attenuation matrix by converting the CT image or radioactive source transmission image, and reconstruct the SPECT image by iterative reconstruction Underestimation of bone imaging drug intake due to attenuation of human tissue; image spatial resolution recovery step, by moving point source distance A change from the surface of the collimator, a point spread function related to the distance is measured in the projected image, and a point spread function matrix is established, and the point spread function matrix is used for the iterative image reconstruction to restore the spatial resolution; The noise removal step is used in the iterative image reconstruction by analysis or wavelet filter to remove the noise in the SPECT image; the bone metabolism volume calculation step is based on the measured actual radioactive concentration and the pixel intensity in the image. The linear relationship between the two is calculated to physically correct the bone imaging drug uptake concentration of each pixel in the SPECT image, and the coordinates in the "region of interest" are calculated using the threshold value by calculating the coordinate system conversion and the concentration change gradient. Metabolic volume; standard uptake value calculation step, based on the patient's weight and height, and the patient's radioactive injection dose, calculate the quantitative intake index of the drug for the drug, including standard intake value and lean body standard Intake value; an evaluation step by which the amount of change in the quantitative intake index is used to evaluate changes occurring before and after bone treatment. For example, the method for quantitatively detecting bone images in claim 1 of the patent application scope, wherein the step of moving the patient between the scans further comprises using the CT image to utilize a high degree of difference between the bone and other tissues of the Heinz unit, to a plurality of The threshold divides the image into two regions, bone and non-bone, and removes the non-bone region and only the bone region from the CT image, and the reconstructed SPECT image is automatically moved and rotated. The CT image produces a maximum overlap fit, re-automatically aligning the SPECT and CT images to correct patient movement between the scans, wherein the correction includes using a plurality of dimensions of displacement and angular orientation. The method for quantitative detection of a bone image according to the first aspect of the patent application, wherein the tissue attenuation correction step calculates a 140 keV attenuation of each pixel unit in the image by converting the CT image or the radiation source transmission image Coefficient, through the image corresponding to the position of the probe, the attenuation model of each probe unit corresponding to the probe is calculated by exponential model and line integral to create an attenuation matrix, and the attenuation matrix is used to correct the tissue attenuation in the iterative reconstruction, wherein the attenuation matrix The magnitude of photon attenuation for each corresponding line is recorded in multiple parameters. For example, the quantitative detection technology method of the bone image in the first application of the patent scope, wherein the image spatial resolution recovery step uses the half-height width variation of the moving point source in the original projection data to obtain the distance related to the collimator. The point spread function matrix is established by the point spread function, and the point spread function matrix is used for iterative reconstruction to restore the spatial resolution of the image. The point spread function is modeled by means of an analysis function, and the point spread function matrix is subsequently used. In the pre-projection step in the iterative reconstruction, the spatial resolution of the SPECT image is restored by iterative. For example, in the method for quantitative detection of bone images in claim 1, wherein the noise removal step is performed by implanting an analysis or wavelet filter into an iterative integrated reconstruction to remove noise in the SPECT image. The equivalent analysis filter filters the noise in the step of comparing the filtered original image and the front projected image in the iterative reconstruction, wherein the wavelet filter performs the base expansion of the SPECT image in a fixed pattern, in different In the expansion coefficient bar graph of the hierarchy, the high-frequency expansion coefficient is excluded by the fixed window width, and the expansion coefficient is filtered by the analysis function, and then the image recombination is performed to remove the SPECT image noise. For example, in the quantitative detection technology method of the bone image in the first application of the patent scope, wherein the bone metabolism volume calculation step takes the pixel having the maximum ingestion concentration in the “region of interest” as a reference point, and the image region is from a normal right angle. The coordinate system is converted to the spherical coordinates, and the gradient of the concentration change in the radial direction is calculated in the image, and the region representing the metabolic volume of the bone in the region of interest is delineated by the threshold range of the gradient, and the region of the bone metabolic volume is then passed through the spherical coordinates. Convert to Cartesian coordinates to calculate the bone metabolism volume within the "region of interest". As described in any of claims 1-5, the quantitative detection technique of the bone image is suitable for SPECT or SPECT/CT imaging using a SPECT bone imaging drug to measure the standard uptake value of bone for the drug. The standard intake value of lean body and the volume of bone metabolism. As in the sixth paragraph of the patent application, the quantitative detection technique of the bone image measures the degree of change in the standard uptake value of the bone, the standard uptake value of the lean body, and the volume of the bone metabolism measured before and after the treatment, and can be used to evaluate the bone. Whether the changes before and after treatment are meaningful. As in any of claims 1-6, the quantitative detection technique of the bone image is more applicable to any SPECT or SPECT/CT imaging using a ^99m Tc-labeled bone imaging drug.