Mathematical Simulation in Nuclear Medicine for Optimization Diagnostic Accuracy of SPECT/CT

Abstract

Purpose: To develop the method of mathematical simulation in the field of nuclear medicine and its
 practical application in research aimed at improving the diagnostic accuracy of the SPECT/CT method.
 The basic principles of the method of mathematical simulation in nuclear medicine and the main modules of the software package “Virtual Platform for Simulation Tests of the SPECT/CT Method”, created
 at the laboratory for simulation in nuclear medicine of Novosibirsk State University and the Institute of
 Theoretical and Applied Mechanics.
 Material and methods: The main principles of the developed software package are the realism of the ‘virtual patient’ mathematical model, the accuracy in modeling of physical processes in visualization, as
 well as simulation conducting close to clinical practice. All studies were carried out in collaboration
 with clinicians. The software complex was verified by comparison with clinical data. Numerical experiments have shown a close correspondence between the results of clinical and virtual studies. In simulation tests, the same errors were obtained on images that were observed on clinical images. Simulation
 computer tests were carried out using the software package “Virtual Platform...” in the field of nuclear
 oncology, cardiology and neurology, aimed at studying the accuracy of images of pathological foci to assess the possibility of switching to quantitative SPECT, as well as optimizing the protocol for examining
 patients.
 Results: Simulation tests have shown that in order to move to quantitative SPECT, it is not enough to be
 limited to the development of a methodology for calibrating SPECT systems for a particular radionuclide. There are problems without understanding and solving which it is impossible to talk about the diagnostic accuracy of the quantitative SPECT method. Such problems are edge artifacts that appear on
 the images of pathological foci, and the rule of stopping the iterative algorithm when the values of activity in the area of interest (pathological focus) that are closest to the true values are reached. A stopping
 criterion based on Pearson's modified chi-square test of goodness of fit is proposed. There is a significantly good correlation between the proposed stop criterion and the minimum RMS error of the image
 reconstruction. The results of simulation modeling with the aim of optimizing SPECT examinations of
 brain perfusion demonstrated the possibility of reducing the data recording time compared to the standard protocol by at least two times.
 Conclusion: The computer simulation method presented in this paper is a practical technology that
 contributes to the optimization and development of a quantitative SPECT method to achieve the best
 possible results in the imaging of pathological foci. Further development of the software package is focused on applications in radionuclide therapy and theranostics.