Programmable Real-time Clinical Photoacoustic and Ultrasound Imaging System

Abstract

Photoacoustic imaging has attracted interest for its capacity to capture functional spectral information with high spatial and temporal resolution in biological tissues. Several photoacoustic imaging systems have been commercialized recently, but they are variously limited by non-clinically relevant designs, immobility, single anatomical utility (e.g., breast only), or non-programmable interfaces. Here, we present a real-time clinical photoacoustic and ultrasound imaging system which consists of an FDA-approved clinical ultrasound system integrated with a portable laser. The system is completely programmable, has an intuitive user interface, and can be adapted for different applications by switching handheld imaging probes with various transducer types. The customizable photoacoustic and ultrasound imaging system is intended to meet the diverse needs of medical researchers performing both clinical and preclinical photoacoustic studies.

Figure 1

Photograph (a) and schematic (b) of the developed real-time clinical PAUS imaging system. (c) Photograph of the control panel. (d) Program selection user interface on touch screen pad. (e) Operation sequences of conventional ultrasound and PAUS imaging mode in the programmable US imaging system. PA, photoacoustic; US, ultrasound; TR, ultrasound transducer; FB, fiber bundle; PC, personal computer; OPO, optical parametric oscillator; BF, beamforming; Tx, transmitter; Rx, receiver; IDE, integrated development environment; ADC, analog to digital converter; DC, direct current; TGC, time gain compensation; and GPU, graphics processing unit.

Figure 2. Performance of the real-time clinical PAUS imaging system.

(a) Photograph of the nanonap sample. (b) Overlaid PAUS images at various depths. (c) Overlaid PAUS images for various concentrations. (d) Quantified SNR of the nanonap at various depths and concentrations. (e) Quantified axial resolution at various depths, measured by FWHM. (f) Quantified spectroscopic PA contrast of nanonap. PA, photoacoustic; US, ultrasound; SNR, signal to noise ratio; and FWHM, full width half maximum.

Figure 3. PAUS images of a phantom, using various transducers.

(a) Photograph of the phantom. (b) Photographs, real-time PAUS images, and reconstructed PAUS images acquired with linear array, convex array, phased array, and endocavity transducers. PA, photoacoustic; and US, ultrasound.

Figure 4. PAUS images of a vasculature mimicking phantom.

(a) Photograph of the phantom. The dashed rectangle marks the imaging region. (b) US MAP image of the phantom. (c) PA MAP image of the phantom at an excitation wavelength of 750 nm. (d) Proportional PA MAP image (PA₈₅₀/PA₇₅₀) of the phantom. (e) Overlaid PAUS MAP image of the phantom. PA, photoacoustic; US, ultrasound; PA₇₅₀, PA signal at 750 nm excitation wavelength; PA₈₅₀, PA signal at 850 nm excitation wavelength; and MAP, maximum amplitude projection.

Figure 5. Noninvasive in vivo PAUS imaging of a rat GI tract.

(a) Schematic of experimental setup. (b) Photograph of the rat and imaging region (the red dashed rectangle). (c) In vivo spectroscopic (707 and 900 nm) PA MAP images of rat GI tract before, 1 hour after, and 4 hours after oral administration of nanonaps. (d) Cross sectional overlaid PAUS images at two white dashed lines in c. (e) Depth resolved volumetric PAUS image of the rat 4 hours after oral administration of the nanonap. PA, photoacoustic; US, ultrasound; GI, gastro intestinal; MAP, maximum amplitude projection; H, head; T, tail; FB, fiber bundle; TR, ultrasound transducer; GP, gelatin pad; BVs, blood vessels; S, stomach; I, intestine; and F, feces.

Figure 6. In vivo PA images of a human forearm.

Photograph (a) and PA MAP (b) image of a human right forearm. The red dashed rectangle outlines the imaging region. (c) Cross sectional overlaid PAUS images at the two white dashed lines in b. GP, gelatin pad; UA, ulnar artery; RA, radial artery; T, tendon; PA, photoacoustic; US, ultrasound; and MAP, maximum amplitude projection.