Simultaneous high-frequency ultrasound and optoacoustic imaging of in vivo mouse embryos.

Abstract

An integrated optoacoustic (OA) and high-frequency ultrasound (HFU) system that provides detailed images of anatomical structure and molecular contrast in small animals and transgenic embryos is presented. Volumetric imaging was achieved by raster scanning a vertically oriented imaging probe. The imaging probe was a five-element, 40-MHz, PVDF-TrFE-based annular array. A PBS-filled Petri-dish with a center hole was placed on the abdomen of an anesthetized mouse, and a laparotomy was performed to expose an intact uterus. A bifurcated beam from a 532-nm pulsed laser illuminated the embryos from opposing directions normal to the image plane. The central element of the array was excited with a high-voltage impulse synchronized with the light pulse. The resulting ultrasound echo and OA signals from each scan location were digitized from all five array channels and postprocessed. The anatomy of the embryonic head (HFU image) was coregistered with the embryonic vasculature (OA image). Delay-and-sum beamforming was performed and the resulting HFU and OA images exhibited a notable improvement in the depth of field and signal-to-noise ratio in comparison to the images constructed using signals acquired from the central array element alone. The feasibility of real-time, spatially coregistered, dual-modality in vivo imaging of mouse embryos was demonstrated.