Analysis of flow estimates. (A) With a dedicated software (dFlow, JUV, Catholic University Leuven), single cells of the vector matrix were selected. The example shows a human right ventricle with the sample volume at the tips of the tricuspid valve. The blue curve in the middle panel shows the true inflow velocity profile as it was imported from a PW-Doppler trace from exactly the same position. The green curve shows the tracking derived velocity estimate in the selected matrix cell of the flow vector field. The red curve in the lower panel shows the tracking derived direction estimate (in this case, zero is defined as direction towards the transducer). (B) Examples of tracking results of the same tricuspid inflow profile, acquired at frame rates of 44, 93 and 178 frames per second. The yellow dots indicate the highest correct velocity estimate (cut-off velocity). (C) Relation of measured cut-off velocities vs. acquisition frame rates in tricuspid and mitral valves. Note the high frame-rate dependence of tracking results.