Comparison of fundamental, second harmonic, and superharmonic imaging: a simulation study.

Area of Science:

• Medical Ultrasound Imaging
• Acoustics and Wave Propagation

Background:

• Fundamental imaging (FI) uses emitted pulse frequencies, balancing penetration depth and spatial resolution.
• Tissue harmonic imaging (THI) uses second harmonics, while superharmonic imaging (SHI) utilizes third to fifth harmonics.
• Optimal transmission frequencies for THI and SHI differ due to competing nonlinear propagation and frequency-dependent attenuation.

Purpose of the Study:

• To quantitatively compare fundamental, second harmonic, and superharmonic echocardiography.
• To evaluate imaging performance at their respective optimal transmission frequencies.

Main Methods:

• Modeled forward propagation using a 3D-KZK implementation and the iterative nonlinear contrast source (INCS) method.
• Assumed linear backpropagation for all imaging modes.

Main Results:

• Fundamental imaging (FI) exhibits the narrowest lateral beamwidth at focus; superharmonic imaging (SHI) is narrower outside the focus.
• SHI demonstrates superior axial resolution compared to FI and THI.
• SHI has lower far-field pulse-echo pressure and increased lateral roll-off compared to FI and THI.

Conclusions:

• Superharmonic imaging (SHI) is suitable for echocardiography, potentially enhancing image quality.
• SHI offers improved axial resolution but may result in a slight reduction in the depth-of-field.