Handheld Real-Time LED-Based Photoacoustic and Ultrasound Imaging System for Accurate Visualization of Clinical Metal Needles and Superficial Vasculature to Guide Minimally Invasive Procedures

Abstract

Ultrasound imaging is widely used to guide minimally invasive procedures, but the visualization of the invasive medical device and the procedure’s target is often challenging. Photoacoustic imaging has shown great promise for guiding minimally invasive procedures, but clinical translation of this technology has often been limited by bulky and expensive excitation sources. In this work, we demonstrate the feasibility of guiding minimally invasive procedures using a dual-mode photoacoustic and ultrasound imaging system with excitation from compact arrays of light-emitting diodes (LEDs) at 850 nm. Three validation experiments were performed. First, clinical metal needles inserted into biological tissue were imaged. Second, the imaging depth of the system was characterized using a blood-vessel-mimicking phantom. Third, the superficial vasculature in human volunteers was imaged. It was found that photoacoustic imaging enabled needle visualization with signal-to-noise ratios that were 1.2 to 2.2 times higher than those obtained with ultrasound imaging, over insertion angles of 26 to 51 degrees. With the blood vessel mimicking phantom, the maximum imaging depth was 38 mm. The superficial vasculature of a human middle finger and a human wrist were clearly visualized in real-time. We conclude that the LED-based system is promising for guiding minimally invasive procedures with peripheral tissue targets.

Photoacoustic imaging depth comparison at 532-, 800-, and 1064-nm wavelengths: Monte Carlo simulation and experimental validation

“…Therefore, first near-infrared window (NIR-I) (700 to 900 nm) is widely used for sample illumination in PAI rather than visible (400 to 600 nm) region for deep tissue imaging. [23][24][25][26] Although imaging depth is increased in NIR-I, it comes with a cost of a bulky, inefficient, expensive two-stage [Ti:sapphire, dye, or optical parametric oscillator (OPO)] laser needed to generate the light in this window. Recently, a second window of near-infrared region (NIR-II, 900 to 1200 nm) has been used for PAI.…”

Imaging of human peripheral blood vessels during cuff occlusion with a compact LED-based photoacoustic and ultrasound system

“…The dual modality imaging system (AcousticX, CYBERDYNE Inc, Tokyo, Japan) [10] was based on a linear-array US probe for ultrasound detection with LED arrays as excitation light source. The US imaging probe was similar to a clinical linear array US probe (128 transducer elements, 9 MHz central frequency, 0.3 mm inter-element spacing).…”

Photoacoustic imaging in the second near-infrared window: a review

“…This had made the laser system expensive, bulky, and very inefficient (20% to 30% efficiency is the best we can achieve in terms of the final laser output). Recently, pulsed laser diodes 57,[90][91][92][93][94] and light-emitting diodes [95][96][97][98][99][100] were reported as alternative sources for PAT in the NIR-I window; however, they provide low-energy pulses compared to traditional lasers (few mJ per pulse versus hundreds of mJ) and hence were not ideal for deep-tissue imaging. Another drawback of NIR-I window imaging was the low maximum permissible exposure (MPE), which was directly related to the penetration depth.…”