Application of LED-Based Photoacoustic Imaging in Diagnosis of Human Inflammatory Arthritis

Using low cost and small size light emitting diodes (LED) as the alternative illumination source for photoacoustic (PA) imaging has many advantages, and can largely benefit the clinical translation of the emerging PA imaging (PAI) technology. To overcome the challenge of achieving sufficient signal-to-noise ratio by the LED light that is orders of magnitude weaker than lasers, extensive signal averaging over hundreds of pulses is performed. According to our research, the LED-based PAI could be a promising tool for several clinical applications, such as assessment of peripheral microvascular function and dynamic changes, and diagnosis of inflammatory arthritis. In this chapter, we will first introduce a commercially available LED-based PAI system, and then show the ability of this system in identifying inflammatory arthritis in human hand joints. B-mode ultrasound (US), Doppler, and PA images were obtained from 12 joints with clinically active arthritis, five joints with subclinically active arthritis, and 12 normal joints. The quantitative assessment of hyperemia in joints by PAI demonstrated statistically significant differences among the three conditions. The imaging results from the subclinically active arthritis joints also suggested that the LED-based PAI has a higher sensitivity to angiogenic microvasculature compared to US Doppler imaging. This initial clinical study on arthritis patients validates that PAI can be a potential imaging modality for the diagnosis of inflammatory arthritis.