1. A magnetic resonance imaging (MRI) system comprising: an MRI gantry including a static magnet, gradient magnet coils and at least one radio frequency (RF) coil defining a patient imaging volume into which the chest region of a patient can be located; RF receiver and transmitter circuits coupled to said at least one RF coil; control circuits connected to said gantry and to said RF receiver and transmitter circuits, said control circuits having an operator display and an operator control input port for configuring and operating said MRI system to acquire and process MRI data from said patient, said control circuits being configured to acquire MRI data within one patient breath-hold sufficient to generate (a) at least one tag-off first type non-contrast cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR (inversion recovery) pulse and (b) at least one tag-on second type non-contrast cardiac perfusion image using a data acquisition sub-sequence including a non-selective IR pulse and a spatially selective IR pulse; and image processing circuits configured to generate a processed cardiac perfusion image by differentially combining tag-on and tag-off images.