Large-Pitch Synthetic Transmit Aperture Imaging: A Feasibility Study

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Signal Processing

Background:

• Synthetic Transmit Aperture (STA) ultrasound systems offer high image quality but suffer from hardware complexity and cost due to individually controlled array elements.
• Reducing the number of controlled channels in STA systems is crucial for practical implementation, especially for large-aperture 2D or 3D imaging.

Purpose of the Study:

• To propose and validate a large-pitch synthetic transmit aperture (LPSTA) imaging method to decrease hardware complexity and improve image quality in ultrasound systems.
• To investigate the effectiveness of integrating a spatial response function (SRF) with LPSTA for reducing grating lobes and enhancing image reconstruction.

Main Methods:

• Developed an LPSTA method by combining adjacent transducer elements into subapertures (SAPs) for both transmission and reception, using coprime integers (L, K) to suppress grating lobes.
• Derived the beam pattern of LPSTA using far-field approximation and analyzed the reduction in grating lobes level (GLL) with coprime selection and SRF.
• Validated the imaging performance of LPSTA using Field II simulations and experimental data, comparing it against standard STA and B-mode imaging.

Main Results:

• Beam pattern analysis demonstrated that coprime selection and SRF significantly reduce GLL, enabling LPSTA to achieve a similar beam pattern to full arrays under specific conditions.
• Simulations showed LPSTA with (N/3, N/5) achieved ~25% better lateral resolution and improved contrast-to-noise ratio (CNR) and contrast ratio (CR) compared to a large-pitch receiver system.
• LPSTA achieved comparable image contrast to standard STA with a full array, albeit with a reduced field of view, and demonstrated superior computational efficiency.

Conclusions:

• The proposed LPSTA method effectively reduces hardware complexity and computational cost in ultrasound imaging systems.
• LPSTA with SRF significantly improves image quality metrics such as lateral resolution and contrast, making it a viable alternative to conventional STA.
• This method holds promise for enabling real-time 2D and 3D ultrasound imaging applications utilizing large transducer arrays.