Diffractive Acoustic Tomography: Theory, Preclinical Applications, and Clinical Translation

Abstract

Three-dimensional photoacoustic (PA) and ultrasound (US) imaging can provide anatomical, physiological, and molecular information deep in biological tissue in a safe and non-invasive way. While several transducer choices exist for three-dimensional PA/US imaging, scanning linear-array transducers are one of the most commonly used approaches due to their low system-cost and the wide availability of commercial linear-arrays. However, these linear-array-based systems suffer from poor elevational resolution and target orientation-dependent sensitivity. These pitfalls are the result of the acoustic lens of the transducers limiting the effective synthetic aperture in beamforming. In this work, we present diffractive acoustic tomography (DAT), with the corresponding fast focal line (FFL) image reconstruction, as a solution to improve elevational resolution and sensitivity in three-dimensional PA and US imaging with a scanning linear-array transducer. DAT uses single-slit diffraction to expand the angular sensitivity of the linear-array transducer along the elevational axis, allowing for 3D beamforming to create a larger effective synthetic aperture and thus improve the elevational resolution. We characterize the performance of DAT with the traditional scanning linear-array-based PA and US imaging and determine the optimal slit width and synthetic aperture width based on the tradeoff in resolution and signal-to-noise ratio (SNR). We then build a preclinical DAT system and demonstrate applications in life sciences, cancer, pregnancy, and obesity research. Finally, we investigate and develop handheld implementations of DAT and demonstrate applications in vascular imaging and needle guidance.