Conventional photoacoustic imaging (PAI) systems use bulky and high-cost laser sources to derive functional and molecular information of the tissue. Recently, light emitting diodes (LED) have emerged as an affordable and compact alternative illumination source for PAI. Despite their low energies, LEDs have provided sufficient photoacoustic contrast for in vivo imaging of mice and for certain clinical applications. This is largely due to PA signal averaging allowed by higher repetition rates of the LEDs without compromising on video frame rate photoacoustic imaging. In this work, using multiple in vivo and phantom experiments, we demonstrate the potential of LED-based photoacoustic and ultrasound imaging (2-D and 3-D) for real-time functional, molecular and structural characterization of tissue. This includes photoacoustic derived functional oxygen saturation information and mapping molecules such as melanin, methylene blue and indocyanine green, and ultrasound derived anatomical information of tissue. These results demonstrate that LED-based PA and US imaging hold strong potential for accelerating several pre-clinical and clinical applications, especially in resource-poor settings.
Photoacoustic computed tomography (PACT) has been widely explored for studying human diseases as well as response to therapies. Most PACT systems employ a large footprint, bulky, and high-cost lasers. Light emitting diodes (LEDs) based B-mode photoacoustic imaging systems have emerged as a low cost and compact alternative, offering a unique opportunity to expedite the widespread adoption of photoacoustic imaging in clinical and resource-poor settings. The high pulse repetition rate of LEDs facilitates signal-to-noise ratio improvements through averaging in spite of lower pulse energy. Here, we present the development of first low-cost LED-based PACT system that uses multiple LED arrays and a linear ultrasound transducer to generate three-dimensional structural, functional and molecular images of the object. Similar to OPO based lasers, our LED-PACT system allows for the multi-wavelength photoacoustic imaging vital for mapping functional and molecular information. Our experiments demonstrate that this study will enable clinical and pre-clinical applications such as imaging human arthritis and whole body mouse imaging.
Photoacoustic imaging (PAI) maps functional and molecular optical contrasts of tissue at ultrasonic spatial resolution and imaging depth. To generate detectable PA signals from deeper regions, expensive, bulky and high-energy class IV lasers are conventionally employed. Light emitting diodes (LED) have recently emerged as an alternative excitation source for PA imaging offering many advantages including portability, affordability, speed, multi-wavelength excitation, and eye/skin safety. Although the output energy of LED’s is far lower than lasers, high pulse repetition rate offers possibility to average more frames and thus improve the SNR. In this work, we performed controlled experiments on tissue-mimicking phantoms to compare the PAI performance of laser and LED light sources comprehensively. Our studies demonstrate that the LED based PA systems are ideal for low resource and point-of-care settings where the required depth of penetration is within 2-3 cms., whereas a high-energy laser is found to be more effective for higher penetration depths (<3 cm). In addition, it is clear from our results that LED-based PA imaging offers higher frame rate with similar spatial resolution and decent signal to noise ratio, which is comparable to conventional laser-based photoacoustic imaging.