Real-time optoacoustic monitoring and three-dimensional mapping of a human arm vasculature

Abstract

We present our findings from a real-time laser optoacoustic imaging system (LOIS). The system utilizes a Q-switched Nd:YAG laser; a standard 128-channel ultrasonic linear array probe; custom electronics and custom software to collect, process, and display optoacoustic (OA) images at 10 Hz. We propose that this system be used during preoperative mapping of forearm vessels for hemodialysis treatment. To demonstrate the real-time imaging capabilities of the system, we show OA images of forearm vessels in a volunteer and compare our results to ultrasound images of the same region. Our OA images show blood vessels in high contrast. Manipulations with the probe enable us to locate and track arteries and veins of a forearm in real time. We also demonstrate the ability to combine a series of OA image slices into a volume for spatial representation of the vascular network. Finally, we use frame-by-frame analysis of the recorded OA video to measure dynamic changes of the crossection of the ulnar artery.

Figure 1

OA probe of the LOIS.

Figure 2

Schematic showing the scanning locations for the two experiments. (a) Regions scanned for the first test. The first test involved visualizing the vessels of the wrist while sliding the probe from the ulnar artery to the radial artery. The letters a to d indicate location of images shown in Figs. 34. (b) Region investigated during the second test. The second test was performed to track the path of the cephalic vein by connecting the probe to a translational stage and scanning in the proximal direction of the forearm for a distance of 76 mm starting at the wrist.

Figure 3

OA images of the wrist vessels acquired in real-time during test 1: the ulnar artery in (a) a cross axis view and (b) a long axis view, (c) a vein near the surface, and (d) the radial artery.

Figure 4

US images acquired using probe manipulations identical to those yielding OA images shown in Fig. 3: (a) cross axis and (b) long axis views of the ulnar artery, (c) view of a vein in the midwrist region, and (d) the radial artery in cross axis view.

Figure 5

(a) OA 3-D volume that showing spatial orientation of the branches of the cephalic vein. The images used to generate the volume were obtained during test 2, and the resulting volume corresponds to the area depicted in the Fig. 2b. (b) A single slice of the 3-D volume taken at the position indicated by the dashed line in (a). The slice clarifies location of the veins under the skin.

Figure 6

Analysis of the cross section of the ulnar artery using real-time OA imaging: (a) frame 59 of Video 4, showing a small cross section of the ulnar artery; (b) frame 60 (100 ms later) of Video 4 showing a large cross section of the ulnar artery; and (c) intensity profiles measured from the images shown in (a), solid blue line, and (b), dashed red line. The profiles explain the positions of the front (closer to the skin) and rear (farther from the skin) boundaries of the ulnar artery at those time moments. (d) Size of the ulnar artery measured as a function of time orthogonally to the skin using real-time OA imaging; the dashed red line shows median value. (Color online only.)

Video 1

Real-time tracking of the wrist vessels using optoacoustic imaging (QuickTime 4.1 MB)..

Video 2

Real-time tracking of the wrist vessels using ultrasonic imaging (QuickTime 4.8 MB)..

Video 3

Three-dimensional optoacoustic image showing superficial vascular network of a human forearm (QuickTime 1.2 MB). .

Video 4

Cross section of a beating ulnar artery (QuickTime 616 KB). .