Saad Abbasi1, Kevan Bell1,2, Benjamin Ecclestone1, Parsin Haji Reza1. 1. PhotoMedicine Labs, Department of Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada. 2. IllumiSonics, Inc., Department of Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada.
Abstract
BACKGROUND: As photoacoustic (PA) techniques progress towards clinical adoption, providing a high-speed live feedback becomes a high priority. To keep up with the instantaneous optical feedback of conventional light microscopes, PA imaging would need to provide a high-resolution video-rate live feed to the user. However, conventional PA microscopy typically trades resolution, sensitivity and imaging speed when optically scanning due to the difficult opto-acoustic confocal geometry. Here, we employ photoacoustic remote sensing (PARS), an all-optical technique that relies on optical confocal geometry, to provide a high-resolution live display in a reflection-mode PA architecture. METHODS: Employing a conventional x-y galvanometer scanner and a 600 KHz pulse repetition rate laser we implement a system capable of acquiring 2.5 frames per second in 2D. To complement this fast scanning optical system, we implement a computationally inexpensive image reconstruction method that is able to render the frames with minimal overhead, providing a live display. RESULTS: Employing the proposed method, we demonstrate a live feedback with frame rates as high as 2.5 Hz in 2D and also report the first results of 3D imaging with a non-contact label-free reflection-mode technique. The method is validated with phantom studies and in-vivo imaging. Employing a repetition rate of 600 KHz, a live feed of carbon fibers is realized with a C-scan rate of 2.5 Hz. The imaging resolution was measured to be 1.2 µm, the highest reported for a real-time reflection-mode architecture. The mean and peak SNR were measured to be 44 and 62 dB respectively in-vivo. 3D visualizations of carbon fiber phantoms and mouse ear microvasculature structure are also demonstrated. CONCLUSIONS: In summary, we present a method that has a small computational overhead for image rendering, resulting in a live display capable of real-time frame rates. We also report the first 3D imaging with a non-contact label-free reflection-mode PA technique. The all-optical confocal geometry required by PARS is significantly easier to implement and maintain than the opto-acoustic geometry of conventional PA microscopy techniques. This results in a system capable of high resolution and sensitivity, imaging at real-time rates. The authors believe this work represents a vital step towards a clinical high-resolution reflection-mode video-rate PA imaging system. 2021 Quantitative Imaging in Medicine and Surgery. All rights reserved.
BACKGROUND: As photoacoustic (PA) techniques progress towards clinical adoption, providing a high-speed live feedback becomes a high priority. To keep up with the instantaneous optical feedback of conventional light microscopes, PA imaging would need to provide a high-resolution video-rate live feed to the user. However, conventional PA microscopy typically trades resolution, sensitivity and imaging speed when optically scanning due to the difficult opto-acoustic confocal geometry. Here, we employ photoacoustic remote sensing (PARS), an all-optical technique that relies on optical confocal geometry, to provide a high-resolution live display in a reflection-mode PA architecture. METHODS: Employing a conventional x-y galvanometer scanner and a 600 KHz pulse repetition rate laser we implement a system capable of acquiring 2.5 frames per second in 2D. To complement this fast scanning optical system, we implement a computationally inexpensive image reconstruction method that is able to render the frames with minimal overhead, providing a live display. RESULTS: Employing the proposed method, we demonstrate a live feedback with frame rates as high as 2.5 Hz in 2D and also report the first results of 3D imaging with a non-contact label-free reflection-mode technique. The method is validated with phantom studies and in-vivo imaging. Employing a repetition rate of 600 KHz, a live feed of carbon fibers is realized with a C-scan rate of 2.5 Hz. The imaging resolution was measured to be 1.2 µm, the highest reported for a real-time reflection-mode architecture. The mean and peak SNR were measured to be 44 and 62 dB respectively in-vivo. 3D visualizations of carbon fiber phantoms and mouse ear microvasculature structure are also demonstrated. CONCLUSIONS: In summary, we present a method that has a small computational overhead for image rendering, resulting in a live display capable of real-time frame rates. We also report the first 3D imaging with a non-contact label-free reflection-mode PA technique. The all-optical confocal geometry required by PARS is significantly easier to implement and maintain than the opto-acoustic geometry of conventional PA microscopy techniques. This results in a system capable of high resolution and sensitivity, imaging at real-time rates. The authors believe this work represents a vital step towards a clinical high-resolution reflection-mode video-rate PA imaging system. 2021 Quantitative Imaging in Medicine and Surgery. All rights reserved.
Entities:
Keywords:
3D imaging; Photoacoustic (PA); live-feedback; microscopy; remote; sensing