When examining patients by single-photon emission computed tomography, the distribution of a radiopharmaceutical drug in biological tissues is evaluated. An active fast-growing tumor has an increased uptake of the drug compared to healthy tissues. In recent years, there has been considerable interest in the level of activity of a radiopharmaceutical in tumor lesions, since it can be useful for monitoring the effectiveness of prescribed therapy. To obtain quantitative results, it is necessary that the applied reconstruction algorithms include the main effects that contribute to the formation of images. One of these factors is the geometric resolution of the collimator. It was expected that taking into account this effect would improve the quantitative assessment of tumor lesions in reconstructed images. However, there were "pitfalls" in the way of obtaining quantitative images. In the diagnostic images obtained taking into account the "geometric resolution of the collimator", so-called edge artifacts were observed, which manifested themselves in the form of a sharp increase in intensity of radiopharmaceutical accumulation in small tumors and as oscillations in the intensity of radiopharmaceutical accumulation at the edges in large tumors. The problem of edge artifacts casts doubt on the correctness of quantitative assessment the level of intensity of drug accumulation in tumor lesions. In this paper, the problem of edge artifacts is investigated using the method of mathematical modeling. In numerical experiments, the dependence of the quantitative estimate of the intensity of RPD accumulation on the parameters of the reconstruction algorithm was investigated for the first time. Keywords: Nuclear medicine, mathematical modeling, single-photon emission computed tomography, edge artifacts.

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When examining patients by single-photon emission computed tomography, the distribution of a radiopharmaceutical drug in biological tissues is evaluated. An active fast-growing tumor has an increased uptake of the drug compared to healthy tissues. In recent years, there has been considerable interest in quantifying the level of activity of a radiopharmaceutical in tumor lesions, since it can be useful for monitoring the effectiveness of prescribed therapy. To obtain quantitative results, it is necessary that the applied reconstruction algorithms include the main effects that contribute to the formation of images. One of these effects is the "blurring" of the image of a point source in the form of a spot. It was expected that taking into account this effect would improve estimates. However, there were "pitfalls" in the way of obtaining quantitative images. In the clinical images obtained taking into account the "blurring effect", so-called edge artifacts were observed, which manifested themselves in the form of a sharp increase in intensity in small tumors and a surge in intensity at the edges in large tumors. The problem of edge artifacts casts doubt on the correctness of quantifying the level of drug activity in tumor lesions. In this paper, the problem of edge artifacts is investigated using the method of mathematical modeling. In numerical experiments, the dependence of the quantitative assessment of activity on the parameters of the reconstruction algorithm was investigated for the first time.