Improvement of B-scan spatial resolution by pulse-echo ultrasound transit time spectroscopy

Abstract

The ability of pulse-echo ultrasound transit time spectroscopy (PE-UTTS) to improve the axial and lateral spatial resolution of an ultrasound B-scan image was investigated in this study. An acrylic step-wedge sample was used, consisting of 6 axial steps of both 0.2 and 0.1 mm height, at lateral separations ranging from 0.75 mm to 24 mm. The sample was immersed in water and conventional B-scan images obtained using an industrial Olympus Omniscan system with 2.25, 5 and 10 MHz transducers along with a clinical GE Voluson scanner with a 12 MHz transducer. PE-UTTS B-scan images were also created utilising the Omniscan RF data. From a qualitative perspective, the PE-UTTS B-scan images, at all three frequencies, demonstrated significantly greater axial and lateral spatial resolution than the corresponding conventional B-scan images. Quantitative analysis was performed by comparing the actual depth and length of the acrylic step surfaces with those measured from the conventional and PE-UTTS B-scan images. Of particular note, the depth accuracy for PE-UTTS at 10 MHz was greater than the conventional clinical B-scan at 12 MHz, being 99.90–99.94% compared to 95.95–97.77%. Lateral accuracy was also higher for PE-UTTS at 10 MHz, ranging from 86.67% to 96.67%, compared to 40.00% to 84.58% for the conventional scanner at a frequency of 12 MHz. This scientific study suggests that PE-UTTS has potential to improve clinical ultrasound B-scan image fidelity.