Modified multi-element synthetic transmit aperture method for ultrasound imaging: A tissue phantom study

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Acoustic Engineering

Background:

• Synthetic aperture imaging techniques are crucial for enhancing ultrasound resolution and image quality.
• Previous work established the modified synthetic transmit aperture (STA) method, necessitating further development for multi-element arrays.
• Accurate modeling of transducer arrays and their acoustic properties is essential for advanced imaging algorithms.

Purpose of the Study:

• To present and verify the modified multi-element synthetic transmit aperture (MSTA) method for ultrasound imaging.
• To extend previous research on modified STA by incorporating multi-element transmit and receive capabilities.
• To evaluate the performance of the MSTA method in terms of noise reduction, visualization depth, and lateral resolution.

Main Methods:

• Developed a modified multi-element synthetic transmit aperture (MSTA) algorithm incorporating apodization weights.
• Calculated apodization weights using angular directivity functions (ADFs) derived from the exact solution of a boundary-value problem for a periodic baffle system.
• Validated the MSTA method using Field II simulated data and experimental data from a tissue-mimicking phantom with a 4MHz linear transducer array.

Main Results:

• The modified MSTA method demonstrated a 15dB improvement in noise reduction near the transducer surface (1mm depth).
• Visualization depth was significantly increased, showing an 86% augmentation in scattered amplitude at 90mm depth.
• A minor degradation in lateral resolution was observed: approximately 8% at 50mm and 5% at 90mm depth.

Conclusions:

• The modified MSTA method offers substantial improvements in ultrasound image quality, particularly in noise reduction and extended visualization depth.
• The method effectively accounts for the finite size of transmit subapertures and receive elements through precise apodization.
• While achieving enhanced imaging performance, the modified MSTA method presents a minor trade-off in lateral resolution, which is acceptable for many clinical applications.