Phase contrast magnetic resonance imaging (PC-MRI) is a specific type of magnetic resonance imaging used primarily to determine flow velocities. PC-MRI can be considered a method of Magnetic Resonance Velocimetry. Since modern PC-MRI is typically time-resolved, it can also be referred to as 4D imaging (three spatial dimensions plus time).
If you add up all the letter "m"s that comprise the full spelling of the acronym "PC-MRI" - phase contrast magnetic resonance imaging - the total sum of "m"s is two.