Dual-/tri-apodization techniques for high frequency ultrasound imaging: a simulation study

Area of Science:

• Medical Imaging
• Acoustic Engineering
• Signal Processing

Background:

• High side-lobe levels in ultrasound B-mode imaging degrade contrast-to-noise ratio (CNR).
• Linear apodization suppresses side lobes but broadens the main lobe, reducing lateral resolution.
• Non-linear apodization methods offer a solution to reduce side lobes without compromising main-lobe width.

Purpose of the Study:

• To computationally evaluate non-linear apodization methods (dual-/tri-apodization) for high-frequency ultrasound.
• To compare their performance against traditional linear apodization (rectangular window).
• To assess the impact on side-lobe levels and main-lobe widths.

Main Methods:

• Simulated dual-/tri-apodization using rectangular, Dolph-Chebyshev, and Kaiser window functions.
• Conducted point and cyst target simulations using Field-II software.
• Utilized a 40 MHz linear array transducer with 128 elements.
• Compared performance metrics including side-lobe level and main-lobe widths (-6 dB and -35 dB).

Main Results:

• Dual-/tri-apodization showed main-lobe widths comparable to the rectangular window.
• Side-lobe levels were suppressed by 9-10 dB with non-linear apodization.
• Contrast-to-noise ratio (CNR) improved by 41% (dual) and 51% (tri) in cyst simulations.

Conclusions:

• Non-linear apodization (dual-/tri-apodization) effectively reduces side-lobe levels.
• This method maintains main-lobe width, unlike linear apodization.
• Non-linear apodization is a promising technique for enhancing CNR in high-frequency ultrasound imaging.