Sound speed correction in ultrasound imaging.

Area of Science:

• Medical Imaging
• Biomedical Engineering
• Acoustics

Background:

• Standard ultrasound systems use a fixed sound speed (1.54 mm/µs) for delay and timing.
• Inhomogeneities in the body's sound speed cause image defocusing and increased clutter.
• This limits the diagnostic quality of ultrasound images.

Purpose of the Study:

• To improve ultrasound image quality by optimizing the sound speed for delay and timing.
• To investigate the impact of variable sound speeds on lateral resolution and clutter.
• To develop an automated method for determining the optimal sound speed.

Main Methods:

• Ultrasound imaging was performed using various trial sound speeds with standard transducers.
• Image quality was assessed in phantoms and in vivo (OB, abdominal, breast) imaging.
• An algorithm was developed to analyze spatial frequency content and identify optimal sound speed based on lateral image quality.

Main Results:

• Improved lateral resolution and reduced clutter were observed with optimized sound speeds.
• Specific optimal speeds were identified: 1.48 mm/µs for OB/abdominal (4 MHz) and 1.44 mm/µs for breast (8 MHz) imaging.
• The developed algorithm accurately predicted the sound speed yielding the best lateral image quality.

Conclusions:

• Adjusting sound speed beyond the standard 1.54 mm/µs significantly enhances ultrasound image quality.
• An automated algorithm can effectively determine and apply optimal sound speeds for improved diagnostic accuracy.
• This technique offers a practical method to enhance standard ultrasound imaging without specialized hardware.