Ring-array photoacoustic tomography for imaging human finger vasculature

Abstract

For early diagnosis of rheumatoid arthritis (RA), it is important to visualize its potential marker, vascularization in the synovial membrane of the finger joints. Photoacoustic (PA) imaging, which can image blood vessels at high contrast and resolution, is expected to be a potential modality for earlier diagnosis of RA. In previous studies of PA finger imaging, different acoustic schemes, such as linear-shaped arrays, have been utilized, but these have limited detection views, rendering inaccurate reconstruction, and most of them require rotational detection. We are developing a PA system for finger vascular imaging using a ring-shaped array ultrasound (US) transducer. By designing the ring-array sensor based on simulations, using phantom experiments, it was demonstrated that we have created a system that can image small objects around 0.1 to 0.5 mm in diameter. The full width at half maximum of the slice direction of the system was within 2 mm and corresponded to that of the simulation. Moreover, we could clearly visualize healthy index finger vasculature and the location of the distal interphalangeal and proximal interphalangeal joints by PA and US echo images. In the future, this system could be used as a method for visualizing the three-dimensional vascularization of RA patients' fingers.

Progress of clinical translation of handheld and semi-handheld photoacoustic imaging

“…By using transducer arrays, PACT can capture PA signals in different views for each single laser pulse with a cost of detection bandwidth (single element transducer: up to hundreds of MHz; transducer array: tens of MHz), leading to a higher temporal resolution (10−200 Hz, or frames per second) and a lower spatial resolution. Full-ring-array-based PACT can receive PA signals over a view of 360° to eliminate artifacts and improve SNR, which has been extensively applied in detecting breast cancerous lesions [ 35 , 53 ], evaluating human joint diseases [ 52 , 54 , 55 ], and visualizing vasculatures in human extremities [ 56 ]. However, due to the configuration of full-ring transducer arrays, it is hard to design handheld or semi-handheld devices.…”

LED-based photoacoustic imaging for early detection of joint inflammation in rodents: towards achieving 3Rs in rheumatoid arthritis research

“…7 Initial results have shown promise of using PA for RA imaging. [8][9][10][11] In this work, we have used an LED-based hand-held PA imaging system for pre-clinical RA imaging on rodent models. We have developed a multicenter 3Rs (Replace, Refine and Reduce) strategy to refine and reduce animal use in RA-related research.…”

Monte Carlo simulations and photoacoustic experiments to compare imaging depth at 532 nm, 800 nm, and 1064 nm

“…Raster scanning of the confocally aligned optical illumination and acoustic detection gives 3-dimensional volumetric image of the target sample [17]. On the other hand, in PAT the sample is homogeneously illuminated by laser pulses and single or multiple USTs are used to acquire photoacoustic (PA) waves from different angles around the sample [18,19]. Reconstruction algorithms are used to process the collected PA waves and form cross-sectional images of the target.…”