Multipinhole single photon SPECT myocardial blood flow absolute quantification method and application
Multipinhole single photon SPECT myocardial blood flow absolute quantification method and application
 CN 105,997,125 B
 Filed: 06/15/2016
 Issued: 09/17/2021
 Est. Priority Date: 06/15/2016
 Status: Active Grant
First Claim
1. A method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow of multipinhole SPECT or SPECT/CT removes interference of physical factors on the dynamic images through quantitative reconstruction of the images to obtain a time activity curve between a blood pool and myocardium, wherein the concentration of radioactivity is expressed in a unit Bq/ml;
 using the blood pool and the myocardial activity curve to perform absolute quantitative calculation of myocardial blood flow, the method comprises the following steps;
a nuclide physical decay correction step, which is carried out according to the starting time point, the acquisition time length and the acquired time of the dynamic SPECT^{99m}Halflife of Tc nuclide, calculating nuclide attenuation correction coefficient of each dynamic time point, thereby recorrecting radioactivity count which should be possessed in the original projection image;
a patient movement correction step in scanning, wherein the dynamic SPECT images of each dynamic time point are used, the heart center is used as an origin, the boundary of a blood pool and cardiac muscle is found out through coordinate conversion, line tracking and geometric shape approximation, and the patient movement in scanning is corrected by obtaining a vector for correcting the patient movement by utilizing the maximum correlation;
a scattering correction step, calculating the scattering component in the image by using a scattering energy window, and subtracting the scattering component image to obtain a scattering correction image;
a geometric distortion correction step, wherein according to the geometric position of the pinhole and the probe corresponding to the center of the reconstructed image, in iterative reconstruction, the translation and coordinate conversion operation is carried out on the two forward rays through a front projection step and a back projection step so as to determine the correct position of the oblique rays on the probe and the reconstructed image, thereby correcting the geometric distortion of the reconstructed image caused by the oblique rays;
a data truncation compensation step, wherein in the iterative image reconstruction process, the truncated area of the original projection image is estimated through the field range expansion and projection steps of the reconstructed image, the truncated area in the projection image of the reconstructed image is used for counting and butting the original image so as to expand the field range of the original image, and through the iterative process, the original image of the expanded field range is used as input to expand the range of the reconstructed image to be converged so as to compensate the artifact caused by data truncation;
a tissue attenuation image generation step, converting the CT image into a tissue attenuation image, calculating an attenuation value of each ray by using a pinhole to irradiate the probe to create a tissue attenuation matrix, and correcting the underestimation of the drug uptake activity and the activity of other parts except the heart of the heart caused by the tissue attenuation by using the tissue attenuation matrix in iterative reconstruction so as to correct the tissue attenuation in the image;
the image spatial resolution recovery step includes calculating the distance between a pixel of a reconstructed image and a pinhole according to a ray track according to rays from a probe penetrating the pinhole to the reconstructed image, establishing a diffusion function matrix according to the pinhole, and recovering the spatial resolution of pinhole imaging again by using the diffusion function matrix in iterative image reconstruction;
a noise removing step, which is used in iterative image reconstruction through a wavelet filter to remove noise in the SPECT image;
a pixel value conversion step of filling the prosthesis into the known one^{99m}Tc activity concentration of^{99m}The Tc decay process is subjected to multiple data acquisition and image reconstruction through the nuclide physical decay correction step, the patient movement correction step in scanning, the scattering correction step, the geometric distortion correction step, the data truncation compensation step, the tissue attenuation image generation step, the image spatial resolution recovery step and the noise removal step, and data analysis to obtain pixel values and absolute values^{99m}The linear relation of Tc activity concentration, and then convert the pixel value to the unit Bq/ml with physical meaning, thus obtain quantitative SPECT image;
a myocardial blood flow quantitative calculation step;
the quantitative multipinhole dynamic SPECT image is used for further carrying out dynamic activity measurement on blood pool and myocardial partObtaining a blood pool activity curve and a myocardial activity curve, and performing linear anastomosis on the curves through a physiological mathematical model with a single chamber to obtain three kinetic parameters of K1, K2 and K3, wherein the unit of K1 is ml/min/g, the unit of K2 is ml/min, the unit of K3 is ml/min, the rate of the drug entering myocardial cells is known from K1, and the rate of the drug entering the myocardial cells is obtained through the linear anastomosis of the curves through a physiological mathematical model with a single chamber^{99m}The uptake fraction of the Tclabeled imaging drug was converted to K1 to obtain the absolute blood flow value, the cardiomyocyte rate of the imaging drug was obtained from K2, and the rate of the interaction of the imaging drug with the cardiomyocytes was known from K3.
Chinese PRB Reexamination
Abstract
The invention relates to a quantitative technology of nuclear medicine heart images, in particular to a technical method for quantitative reconstruction of dynamic images of multipinhole SPECT or SPECT/CT and absolute quantitative measurement of myocardial blood flow, and application of the technical method in myocardial blood flow state evaluation. The specific implementation steps comprise: the method comprises a nuclide physical decay correction step, a patient movement correction step in scanning, a scattering correction step, a geometric distortion correction step, a data truncation compensation step, a tissue attenuation correction step, a noise removal step, a pixel value conversion step, a myocardial blood flow quantitative calculation step and a blood flow state evaluation step. By the technical means of the invention, a quantitative multipinhole dynamic SPECT heart image can be generated, and the absolute quantitative calculation of myocardial blood flow can be carried out through the quantitative multipinhole dynamic image, so that the quantitative measurement of myocardial blood flow is carried out, and meanwhile, a blood flow state diagram is established by three indexes of resting blood flow, loaded blood flow, blood flow reserve and the like, and the method is practically applied to the evaluation of the state of myocardial blood flow, solves the problem of carrying out the quantitative measurement of myocardial blood flow by utilizing multipinhole SPECT and SPECT/CT dynamic imaging, and can be used for the evaluation of the myocardial blood flow state.
8 Claims

1. A method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow of multipinhole SPECT or SPECT/CT removes interference of physical factors on the dynamic images through quantitative reconstruction of the images to obtain a time activity curve between a blood pool and myocardium, wherein the concentration of radioactivity is expressed in a unit Bq/ml;
 using the blood pool and the myocardial activity curve to perform absolute quantitative calculation of myocardial blood flow, the method comprises the following steps;
a nuclide physical decay correction step, which is carried out according to the starting time point, the acquisition time length and the acquired time of the dynamic SPECT^{99m}Halflife of Tc nuclide, calculating nuclide attenuation correction coefficient of each dynamic time point, thereby recorrecting radioactivity count which should be possessed in the original projection image; a patient movement correction step in scanning, wherein the dynamic SPECT images of each dynamic time point are used, the heart center is used as an origin, the boundary of a blood pool and cardiac muscle is found out through coordinate conversion, line tracking and geometric shape approximation, and the patient movement in scanning is corrected by obtaining a vector for correcting the patient movement by utilizing the maximum correlation; a scattering correction step, calculating the scattering component in the image by using a scattering energy window, and subtracting the scattering component image to obtain a scattering correction image; a geometric distortion correction step, wherein according to the geometric position of the pinhole and the probe corresponding to the center of the reconstructed image, in iterative reconstruction, the translation and coordinate conversion operation is carried out on the two forward rays through a front projection step and a back projection step so as to determine the correct position of the oblique rays on the probe and the reconstructed image, thereby correcting the geometric distortion of the reconstructed image caused by the oblique rays; a data truncation compensation step, wherein in the iterative image reconstruction process, the truncated area of the original projection image is estimated through the field range expansion and projection steps of the reconstructed image, the truncated area in the projection image of the reconstructed image is used for counting and butting the original image so as to expand the field range of the original image, and through the iterative process, the original image of the expanded field range is used as input to expand the range of the reconstructed image to be converged so as to compensate the artifact caused by data truncation; a tissue attenuation image generation step, converting the CT image into a tissue attenuation image, calculating an attenuation value of each ray by using a pinhole to irradiate the probe to create a tissue attenuation matrix, and correcting the underestimation of the drug uptake activity and the activity of other parts except the heart of the heart caused by the tissue attenuation by using the tissue attenuation matrix in iterative reconstruction so as to correct the tissue attenuation in the image; the image spatial resolution recovery step includes calculating the distance between a pixel of a reconstructed image and a pinhole according to a ray track according to rays from a probe penetrating the pinhole to the reconstructed image, establishing a diffusion function matrix according to the pinhole, and recovering the spatial resolution of pinhole imaging again by using the diffusion function matrix in iterative image reconstruction; a noise removing step, which is used in iterative image reconstruction through a wavelet filter to remove noise in the SPECT image; a pixel value conversion step of filling the prosthesis into the known one^{99m}Tc activity concentration of^{99m}The Tc decay process is subjected to multiple data acquisition and image reconstruction through the nuclide physical decay correction step, the patient movement correction step in scanning, the scattering correction step, the geometric distortion correction step, the data truncation compensation step, the tissue attenuation image generation step, the image spatial resolution recovery step and the noise removal step, and data analysis to obtain pixel values and absolute values^{99m}The linear relation of Tc activity concentration, and then convert the pixel value to the unit Bq/ml with physical meaning, thus obtain quantitative SPECT image; a myocardial blood flow quantitative calculation step;
the quantitative multipinhole dynamic SPECT image is used for further carrying out dynamic activity measurement on blood pool and myocardial partObtaining a blood pool activity curve and a myocardial activity curve, and performing linear anastomosis on the curves through a physiological mathematical model with a single chamber to obtain three kinetic parameters of K1, K2 and K3, wherein the unit of K1 is ml/min/g, the unit of K2 is ml/min, the unit of K3 is ml/min, the rate of the drug entering myocardial cells is known from K1, and the rate of the drug entering the myocardial cells is obtained through the linear anastomosis of the curves through a physiological mathematical model with a single chamber^{99m}The uptake fraction of the Tclabeled imaging drug was converted to K1 to obtain the absolute blood flow value, the cardiomyocyte rate of the imaging drug was obtained from K2, and the rate of the interaction of the imaging drug with the cardiomyocytes was known from K3.
 using the blood pool and the myocardial activity curve to perform absolute quantitative calculation of myocardial blood flow, the method comprises the following steps;

2. A method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow for multipinhole SPECT or SPECT/CT as claimed in claim 1, the scan being a patient movement correction step, a coordinate transformation transforming the cardiac image from rectangular to spherical coordinates and a myocardial boundary from spherical to rectangular coordinates;
 the geometric approximation is approximated by an ellipsoid or other geometric shape similar to the heart;
the maximum correlation is the maximum correlation with the reference myocardial position.
 the geometric approximation is approximated by an ellipsoid or other geometric shape similar to the heart;

3. The method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow for multipinhole SPECT or SPECT/CT as claimed in claim 1, wherein the geometric distortion correction step, the preprojection and the backprojection steps, comprises obtaining forward projection rays facing the reconstructed image and backprojection rays facing the probe in a forward direction through the pinhole, and transforming the forward projection rays and the forward backprojection rays into oblique projection rays and oblique backprojection rays through translation and coordinate transformation operations, thereby determining the correct positions of the oblique projection rays on the probe and the oblique backprojection rays on the reconstructed image.

4. The method for quantitative reconstruction of dynamic images of multipinhole SPECT or SPECT/CT and absolute quantitative measurement of myocardial blood flow according to claim 1, wherein the tissue attenuation image generation step obtains an attenuation coefficient of 140keV for each pixel unit in the SPECT image by using the CT tissue attenuation image, and calculates an attenuation value for each pixel unit corresponding to the probe by an exponential model and a line integral according to the position of the SPECT image corresponding to the pinhole probe, thereby creating an attenuation matrix.

5. The method for quantitative reconstruction of dynamic images for multipinhole SPECT or SPECT/CT and absolute quantitative measurement of myocardial blood flow according to claim 1, wherein the step of recovering the spatial resolution of the image is to consider the pinhole as a geometrically symmetric shape, calculate the distance between the pixel of the reconstructed image and the pinhole according to the ray trajectory based on the center of each ray from the probe penetrating the pinhole to the reconstructed image, and calculate the range and area covered by the distance diffusion according to the solid angle of the pinhole, thereby calculating the diffusion function matrix of each single ray related to the distance between the pinhole and the disk.

6. The method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow for multipinhole SPECT or SPECT/CT as claimed in claim 1, wherein the noise removing step comprises implanting a wavelet filter into the iterative integrated reconstruction to remove noise in the images, filtering the noise by using the wavelet filter in the step of comparing the filtered original images with the preprojection images in the iterative reconstruction, wherein the wavelet filter performs a base expansion on the images in a fixed mode, excludes highfrequency expansion coefficients in fixed window widths in expansion coefficient histograms of different levels, filters the expansion coefficients by using an analysis function, and performs image reconstruction to remove image noise.

7. The method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow of multipinhole SPECT or SPECT/CT according to claim 1, wherein the myocardial blood flow quantitative calculation step requires the use of quantitative multipinhole dynamic SPECT images obtained by physical decay correction of nuclides, patient movement correction during scanning, scatter correction, geometric distortion correction, data truncation compensation, tissue attenuation image generation, image spatial resolution restoration, noise removal and pixel value conversion to measure the dynamic activity of blood pool and myocardial region.

8. The method for quantitative reconstruction of dynamic images and absolute quantitative measurement of myocardial blood flow of multipinhole SPECT or SPECT/CT as claimed in any one of claims 1 to 7, which is applicable to any one of the methods^{99m}Tclabeled cardiac imaging drugs are used for multipinhole SPECT or SPECT/CT dynamic imaging.
Specification(s)