A quantitative method for a nuclear medicine heart image, adapted for quantitative reconstruction of a multi-pinhole single-photon emission computed tomography (SPECT) or SPECT/CT image and an absolute quantization of myocardial blood flow, the method comprising:
- carrying out an iterative image reconstruction, wherein an original projection image is obtained, and iteration is carried out to obtain an SPECT reconstructed image based on the original projection image, wherein the iterative image reconstruction comprises:
- carrying out a geometry distortion correction, wherein a plurality of normal rays are translated and a first coordinate conversion calculation is performed through a forward projection and a back projection based on a geometric position of a pinhole and a detector corresponding to the center of the SPECT reconstructed image, so as to obtain correct positions of an oblique ray at the detector and the SPECT reconstructed image and correct a geometry distortion in the SPECT reconstructed image resulting from the oblique ray;
- carrying out a data truncation compensation, wherein a truncated area in a field of view of the original projection image is calculated by expanding a field of view of the SPECT reconstructed image and performing another front projection, a count of a truncated area in an image projected from the SPECT reconstructed image is combined with the original projection image to expand a field of view of the original projection image, and iteration is performed with the original projection image having an expanded field of view as an input to expand the field of view of the SPECT reconstructed image until convergence is reached, so as to correct an artifact resulting from a data truncation in the SPECT reconstructed image;
- carrying out a tissue attenuation correction, wherein a tissue attenuation matrix is established by calculating an attenuation value of each ray from the pinhole to the detector based on a tissue attenuation diagram, and underestimation of a marker imaging tracer extraction activity of a heart and marker imaging tracer extraction activities of parts other than the heart caused by tissue attenuation are corrected based on the tissue attenuation matrix, so as to correct the tissue attenuation in the SPECT reconstructed image;
- carrying out an image space resolution recovery, wherein a distance between a pixel of the SPECT reconstructed image and the pinhole is calculated based on a ray passing through the pinhole from the detector to the SPECT reconstructed image and a trajectory of the ray, a spread function matrix is established based on the distance between the pixel and the pinhole, and iteration is carried out based on the spread function matrix to recover a space resolution during imaging of the pinhole;
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- carrying out a noise removal, wherein noises in the SPECT reconstructed image are removed through iteration with a filter;
- carrying out a pixel value conversion, wherein the SPECT reconstructed image is converted based on a linear relation between a pixel value and an absolute activity concentration of the marker imaging tracer, so as to turn each pixel value of the SPECT reconstructed image into a unit with a physical meaning to obtain a quantitative SPECT image;
- carrying out a quantitative myocardial blood flow calculation, wherein activities at a blood pool and a myocardium are measured dynamically based on the quantitative SPECT images, so as to obtain a blood pool time activity curve and a myocardial time activity curve, a first dynamic parameter is obtained through fitting the blood pool time activity curve and the myocardial time activity curve to an one-tissue compartment physiological mathematical model, a first rate of the marker imaging tracer entering a myocardial cell is obtained based on the first dynamic parameter, and an absolute blood flow value of the myocardium is obtained by converting the first dynamic parameter based on an extraction fraction of the marker imaging tracer;
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- carrying out a blood flow condition evaluation, wherein a plurality of indicators are obtained based on the first rate to establish a blood flow condition diagram having a blood flow condition, and an evaluation is carried out based on the blood flow condition diagram to output a blood flow condition evaluation result.