A compact dynamic phantom to assess the effect of motion in cardiac PET and SPECT studies

Purpose: Cardiac PET and SPECT images are known to suffer from degradation due to cardiac and respiratory motion. In this work we describe a dynamic heart phantom, that we designed and built, to simulate both these movements. The phantom can be used: (i) to study the degradation effects due to the heart motion on PET/SPECT images and (ii) to evaluate and optimize motion corrections/compensation techniques for PET/SPECT heart studies. Methods: The phantom consists of two main parts. The first one simulates the left ventricle and its contraction while the second one (a moving platform) simulate the respiratory motion. The phantom has been tested in a number of different acquisition configurations (no motion, with only respiratory or cardiac motion, with both cardiac and respiratory motion) to study the effects of heart motion on the reconstructed PET images. On the same set of data we tested the capability of single and double gated, acquisition and reconstruction techniques, to account and compensate for the heart motion. Results: The phantom was able to simulate well both cardiac and/or respiratory motion. In the PET studies we were able to assess the effects of motion on the image quality as well as on the quantitative accuracy of PET data. We found that double gated PET acquisition and reconstructions techniques were effective in recovering the true radioactivity distribution compared to that of the reference static condition (no motion). Conclusions: We have successfully designed and built a compact heart dynamic phantom capable of cardiac and respiratory motion. The phantom can be useful in the assessment of motion degradation on cardiac PET/SPECT images. Furthermore, the phantom can also be used in the evaluation and optimization of gating acquisition and reconstruction techniques as well as in the evaluation of corrections techniques aiming to account and compensate for heart motion.