Global radial velocities from the mid slices of three healthy volunteers on both occasions. Volunteer 1 (a) showed similar heart rates on the two occasions and the two curves matchvery closely. However volunteers 2 (b) and 3 (c) showed different heart rates on the two occasions. TTP systole is not affected much by this change in either volunteer, however the TTP diastole is affected in Volunteer 3 but not in Volunteer 2. TTP atrial systole is affected in both volunteers. This inter-volunteer variation in the effects of different heart-rates makes the assessment of reproducibility more difficult.