There are different imaging techniques in nuclear medicine for cardio-
logic diagnostics, the specific statement of each determines the position in the indication spectrum. Moreover the burden for the
patient and the methodic expence affect their use.
Properly speaking medical imaging of the heart is a
three spatial dimensions and
time as the fourth.
"Parametric analysis of ECG-triggered emission-computed tomograms", Proc. SPIE 1357, Medtech '89: Medical Imaging, (1 November 1990); doi: 10.1117/12.23919; https://doi.org/10.1117/12.23919