Abstract
Photoacoustic tomography systems that uses Q-switched Nd:YAG/OPO pulsed lasers are expensive, bulky, and hence limits its use in clinical applications. The low pulse repetition rate of these lasers makes it unsuitable for real-time imaging when used with single-element ultrasound detector. In this work, we present a pulsed laser diode photoacoustic tomography (PLD-PAT) system that integrates a compact PLD inside a single-detector circular scanning geometry. We compared its performance against the traditional Nd:YAG/OPO based PAT system in terms of imaging depth, resolution, imaging time etc. The PLD provides near-infrared pulses at ~803 nm wavelength with pulse energy ~1.4 mJ/pulse at 7 kHz repetition rate. The PLD-PAT system is capable of providing 2D image in scan time as small as 3 sec with a signal-to-noise ratio ~30. High-speed and deep-tissue imaging is demonstrated on phantoms and biological samples. The PLD-PAT system is inexpensive, portable, allows high-speed PAT imaging, and its performance is as good as traditional expensive OPO based PAT system. Therefore, it holds promises for future translational biomedical imaging applications.
Highlights
Photoacoustic tomography (PAT) is a promising non-ionizing hybrid imaging modality combining high optical contrast and ultrasonic resolution for various clinical applications, such as, breast imaging, brain imaging, molecular imaging, vasculature imaging in small animals etc [1,2,3,4,5,6,7,8]
The pulsed laser diode (PLD) is controlled by the laser driver unit (LDU) which consists of a temperature controller (LaridTech, MTTC1410), a 12 V power supply (Voltcraft, PPS-11810), a variable power supply, and a function generator
The images of hair phantom obtained by collecting PA signals in 30, 20, 10, 5 and 3 sec scan time using pulsed laser diode photoacoustic tomography (PLD-PAT) are shown in Figs. 2(b)-2(f) with a single 2.25 MHz ultrasound transducer (UST)
Summary
Photoacoustic tomography (PAT) is a promising non-ionizing hybrid imaging modality combining high optical contrast and ultrasonic resolution for various clinical applications, such as, breast imaging, brain imaging, molecular imaging, vasculature imaging in small animals etc [1,2,3,4,5,6,7,8]. Since in the NIR window the optical absorption is weak, it has been widely used for deep-tissue imaging These (Nd:YAG/ OPO or dye-based) lasers are expensive, bulky, and are not suitable for high-speed imaging with single-detector due to the low-repetition rate (~10 Hz for ~100 mJ per pulse energy) [7, 13,14,15]. PAT systems based on linear [16,17,18], semicircular [19, 20], circular array [21, 22] of USTs have been used for high speed imaging They do not require scanning and can improve imaging speed (still limited to maximum imaging speed of 10 frames per second as the laser is operating at that frequency). We compare the resolution, imaging-speed, imaging-depth, image-quality of PLD-PAT system with a traditional Nd:YAG/OPO based PAT (OPO-PAT) system
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