Noninvasive functional imaging of cardiac motion via dynamic SPECT

Objectives Noninvasive cardiac imaging using PET and SPECT has been a useful tool for both diagnostic and prognostic assessment of patients suffering from coronary syndromes including ischemia and myocardial dysfunction. However, despite their widespread applications, images are often degraded by involuntary motion of the heart leading to blurring, and sometimes to erroneous diagnosis. The main objective of this study was to simultaneously model the motion of the human heart and the dynamics of the radiopharmaceutical distribution for SPECT myocardial perfusion imaging.

Methods Time activity curves for the vital organs including heart, lungs, and liver were generated for 99mTc-tetrofosmin from patient of our ongoing continuous acquisition SPECT studies. The projection data were simulated using the MCAT phantom for the geometry of a commercially available SPECT/CT system. The activity distribution was parameterized in terms of the tensor product of the spatiotemporal basis functions of the radiotracer distribution and the basis functions of the deformation state of the heart, and solved using ML-EM algorithm.

Results Our results showed that the method of multiparametric optimization can support 4D quantitative visualization of the changes in the deformation of the heart as well as changes in the signal intensity caused by dynamic uptake and washout of the radiopharmaceutical from the myocardium and other organs. The reconstructed images in our model showed a faithful reflection of the actual object.

Conclusions The study demonstrated the technique for obtaining dynamic perfusion images of the radiopharmaceutical when myocardium is in motion. Our results demonstrate the feasibility of simultaneous assessment of the geometrical and functional behavior of the radiopharmaceutical in the heart.

Research Support This work was supported by NIH (5R01HL050663-15).