In tissue harmonic imaging, the frequency used is:

• A. Four times the fundamental frequency
• B. Double the fundamental frequency
• C. Equal to the fundamental frequency
• D. One half the fundamental frequency

Answer: (B)

In tissue harmonic imaging, the frequency utilized is indeed double the fundamental frequency. This imaging technique harnesses the nonlinear propagation of ultrasound waves within the tissue, where the original frequency (the fundamental frequency) generates harmonics as it travels through the medium. These harmonics have frequencies that are multiples of the fundamental frequency due to this non-linear behavior, with the second harmonic specifically being double the original frequency. This is particularly effective in enhancing image resolution and contrast, as the harmonic signals can minimize interference from superficial structures and improve the clarity of deeper tissues.