Подводные камни" на пути количественной оценки тяжести онкологических поражений в диагностической ядерной медицине

Abstract

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.