Bland Altman plots showing the effect of taking the duration of diastole (normalising) into account on the reproducibility of TTP values. (a) and (b) show the effect on TTP DL whereas (c) and (d) show the effect on TTP ASL. In each case each blue diamond represents a single healthy volunteer with its position on the horizontal axis indicating the mean value of the two measurements of TTP and its position on the vertical axis indicating the difference between the two measurements. The blue dotted horizontal lines indicate the mean and ±2 standard deviations of the differences between the two measurements. For the diastolic and atrial systolic peaks the reproducibility is greatly improved by taking the length of diastole into account, showing that it is an effective way of compensating for healthy changes in heart rate between scans.