EFFECTS OF THROUGH-PLANE MYOCARDIAL MOTION ON PHASE-DIFFERENCE AND COMPLEX-DIFFERENCE MEASUREMENTS OF ABSOLUTE CORONARY-ARTERY FLOW

We have previously reported on a complex-difference (CD) now measureme nt technique that produces more accurate results than the phase-differ ence (PD) now measurement technique due to the greater immunity of the former method to partial volume effects. We report here on some of th e ways in which through-plane myocardial motion affects the accuracy o f absolute coronary artery now measurements obtained using the PD and CD techniques. We also discuss motion correction schemes that can be a pplied to the PD and CD processing methods to improve their accuracy. Computer simulations have been performed to assess the magnitude of th e errors associated with these now measurement techniques when they ar e applied to small vessels that are attached to a moving background. L aminar and plug now, with and without complete background suppression, have been considered, Experiments with a moving vessel phantom have b een conducted to test the performance of the PD and CD now measurement techniques in circumstances similar to those simulated, The simulatio ns and the experiments showed that, after corrections for through-plan e motion are made, the CD method generally yields more accurate now re sults than the PD method. As shown by the simulations, however, both m ethods yield compromised results due to subtle saturation effects that occur when the direction of myocardial motion is opposite the directi on of blood now, Unvalidated PD and CD measurements of coronary artery now waveforms in human volunteers are presented to illustrate the mag nitude of the proposed through-plane motion effects in vivo.