A novel phase assignment protocol and driving system for a high-density focused ultrasound array

Area of Science:

• Medical Imaging and Therapy
• Acoustic Engineering
• Array Signal Processing

Background:

• Current phased-array systems for therapy are often 1-D or limited 2-D, with element counts ranging from tens to hundreds.
• Achieving complete 3-D beam steering necessitates lambda/2 interelement spacing, demanding a high density of elements (0.15-3 mm).
• The cost and complexity of cable assemblies for such dense arrays present a significant challenge.

Purpose of the Study:

• To investigate the feasibility of phase quantization as a solution to reduce the number of input lines in phased-array systems.
• To maintain focusing and beam steering capabilities while simplifying array control.
• To assess the impact of this technique on the practical implementation and performance of ultrasound devices.

Main Methods:

• Computer simulations were employed to explore the approach using a 100-element linear array.
• Experimental validation was conducted with a test circuit driving the array.
• Phase quantization involved connecting elements with similar phases to a single wire.

Main Results:

• Simulations confirmed adequate focusing with only four phase signals, without significant increases in grating lobes or focus dimensions.
• Experiments demonstrated practical implementation, achieving adequate focusing with four phase signals.
• A 20% reduction in peak pressure amplitude squared was observed compared to infinite-phase resolution.

Conclusions:

• Phase quantization is a feasible technique for simplifying phased-array control.
• This method allows for the driving of over 10,000 elements using only 33 input lines.
• The technique holds potential for significant advancements in ultrasound therapy and diagnostic devices.