PVDF-TrFE ring-shaped piezopolymer detector for optical-resolution optoacoustic microscopy with extended imaging depth and enhanced sensitivity
Alexey A. Kurnikov1, Maxim B. Prudnikov1, Daria A. Voitovich1, Anna M. Glyavina1, Anna G. Orlova1, Marina A. Sirotkina2, Wei Liu3, Daniel Razansky4,5, Pavel V. Subochev1,2;
1Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603005, Russia; 2Institute of Experimental Oncology and Biomedical Technologies, Privolzhsky Research Medical University, Nizhny Novgorod 603005, Russia; 3Optical Imaging Laboratory, Harbin Institute of Technology, Shenzhen 518055, China; 4Institute for Biomedical Engineering and Institute of Pharmacology and Toxicology, Faculty of Medicine, UZH Zurich, Rämistrasse 71, Zurich 8006, Switzerland; 5Institute for Biomedical Engineering, Department of Information Technology and Electrical Engineering, ETH Zurich, Gloriastrasse 35, Zurich 8092, Switzerland
Abstract
Microvascular analysis enables early diagnosis of vascular disorders like Raynaud's syndrome, diabetes, venous and arterial insufficiency, revealing underlying cardiovascular risks. To assess the state of the vascular network of biological tissues, the optical resolution optoacoustic (or photoacoustic) microscopy (OR-OAM) is increasingly being used. This technology is based on the optoacoustic effect: when tissue is irradiated with short (nanosecond) laser pulses in the visible or near infrared range, broadband ultrasound waves are generated by the transient light absorption, which are recorded by ultrasound detectors. However, clinical translation of OR-OAM typically faces a trade-off between achieving high contrast and resolution versus maintaining an extended depth-of-field at safe laser exposure levels. Gradient refractive index (GRIN) fiber lenses can provide an elongated optical focus preserved over a millimeter-scale length. However, developing coaxially aligned wideband acoustic detectors with high sensitivity remains challenging. Here, we introduce a piezopolymer PVDF-TrFE detector featuring a spherically-focused thin (100 μm) ring geometry with a 4.6 mm aperture and 1.5 mm working distance (NA = 0.84). Numerical modeling reveals not only an extended depth of field, but also an improvement in sensitivity compared to conventional full-aperture detectors. In vitro experiments using whole human blood demonstrated a 14 dB signal-to-noise ratio at a safe laser irradiance of 20 mJ/cm². In vivo angiographic imaging of neonatal mouse cerebral vasculature and human cuticle confirmed the detector's capability to achieve a depth-of-field exceeding 1 mm, highlighting its potential for a broad range of biomedical applications.
Speaker
Alexey Kurnikov
Institute of Applied Physics, Russian Academy of Sciences
Russia
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