Answer #46

The correct answer is D: The axial resolution using harmonic imaging is not as good. This is because the transmit pulse uses a narrow bandwidth during harmonic imaging so as to decrease the overlap between fundamental (transmitting) and harmonic (receiving) bandwidths. This is done by putting more cycles within each pulse and thereby increasing the spatial pulse length (number of pulses x length of each pulse). Since axial resolution is spatial pulse length/2 it increases also and hence axial resolution is worse (larger number is worse, smaller is better). Harmonic imaging is used to decrease artifacts so C is not correct. It does not change the frame rate appreciably and it does not change the amount of reflection, neither of which would necessarily cause a valve leaflet to appear thicker in either case. Harmonic imaging does not cause more reverberations.