F-number optimization for synthetic aperture delay-multiply-and-sum reconstruction

Area of Science:

• Medical Imaging
• Ultrasound Technology
• Signal Processing

Background:

• Transmit and receive f-numbers influence ultrasound image contrast and spatial resolution.
• Previous research focused on receive f-number effects in delay-and-sum (DAS) plane wave imaging.
• A systematic investigation of f-numbers in DAS and delay-multiply-and-sum (DMAS) synthetic aperture (SA) imaging is lacking.

Purpose of the Study:

• To systematically evaluate the impact of varying transmit and receive f-numbers on DAS and DMAS SA imaging.
• To quantify effects on main lobe to side lobe energy ratio (MSER), generalized contrast-to-noise ratio (gCNR), and spatial resolution.
• To provide guidance for f-number selection in SA imaging algorithms.

Main Methods:

• Measurements were performed using a wire target in a water tank and a standard imaging phantom.
• Transmit and receive f-numbers were varied from 1 to 5 in 0.2 increments.
• Key metrics including MSER, gCNR, and spatial resolution were analyzed for DAS and DMAS reconstructions.

Main Results:

• Higher MSER was achieved with mid-range transmit f-numbers (2-4) and high receive f-numbers (>4) for both DAS and DMAS.
• DAS achieved high gCNR with high transmit/receive f-numbers (>4) but reduced spatial resolution.
• DMAS achieved high gCNR with low transmit (<3) and high receive f-numbers (>4) with less spatial resolution tradeoff, though overall gCNR was lower than DAS. High spatial resolution was observed with low receive f-numbers (<2) for both methods. DMAS generally offered higher spatial resolution than DAS.

Conclusions:

• F-number selection critically impacts performance trade-offs between contrast and resolution in DAS and DMAS SA imaging.
• DMAS offers a potentially better balance between contrast and resolution compared to DAS.
• Findings can inform optimal f-number choices for specific ultrasound imaging applications using SA techniques.