RESUMEN

Significance: Optical-resolution optoacoustic microscopy (OR-OAM) enables label-free imaging of the microvasculature by using optical pulse excitation and acoustic detection, commonly performed by a focused optical beam and an ultrasound transducer. One of the main challenges of OR-OAM is the need to combine the excitation and detection in a coaxial configuration, often leading to a bulky setup that requires physically scanning the ultrasound transducer to achieve a large field of view. Aim: The aim of this work is to develop an OR-OAM configuration that does not require physically scanning the ultrasound transducer or the acoustic beam path. Approach: Our OR-OAM system is based on a non-coaxial configuration in which the detection is performed by a silicon-photonics acoustic detector (SPADE) with a semi-isotropic sensitivity. The system is demonstrated in both epi- and trans-illumination configurations, where in both configurations SPADE remains stationary during the imaging procedure and only the optical excitation beam is scanned. Results: The system is showcased for imaging resolution targets and for the in vivo visualization of the microvasculature in a mouse ear. Optoacoustic imaging with focal spots down to 1.3 µm, lateral resolution of 4 µm, and a field of view higher than 4 mm in both lateral dimensions were demonstrated. Conclusions: We showcase a new OR-OAM design, compatible with epi-illumination configuration. This setup enables relatively large fields of view without scanning the acoustic detector or acoustic beam path. Furthermore, it offers the potential for high-speed imaging within compact, miniature probe and could potentially facilitate the clinical translation of OR-OAM technology.

Asunto(s)

Microscopía , Silicio , Animales , Ratones , Acústica , Frecuencia Cardíaca , Iluminación

RESUMEN

High-resolution optoacoustic imaging at depths beyond the optical diffusion limit is conventionally performed using a microscopy setup where a strongly focused ultrasound transducer samples the image object point-by-point. Although recent advancements in miniaturized ultrasound detectors enables one to achieve microscopic resolution with an unfocused detector in a tomographic configuration, such an approach requires illuminating the entire object, leading to an inefficient use of the optical power, and imposing a trans-illumination configuration that is limited to thin objects. We developed an optoacoustic micro-tomography system in an epi-illumination configuration, in which the illumination is scanned with the detector. The system is demonstrated in phantoms for imaging depths of up to 5 mm and in vivo for imaging the vasculature of a mouse ear. Although image-formation in optoacoustic tomography generally requires static illumination, our numerical simulations and experimental measurements show that this requirement is relaxed in practice due to light diffusion, which homogenizes the fluence in deep tissue layers.