Performance characterization of a high-power, compact, low-cost, and high-efficiency VCSEL subsystem for photoacoustic imaging

Photoacoustic imaging (PAI) combines the contrast mechanism of optical imaging with the penetration depth of ultrasound systems. This emerging modality has shown potential to aid in the diagnosis and monitoring of many diseases, but clinical adoption has been limited by the large size, high cost, low wall-plug efficiency, and restrictive laser safety requirements of existing systems—characteristics largely driven by their light sources. We present a photoacoustic handheld probe containing triple-junction, 940-nm VCSELs and laser-driving circuitry. The new VCSEL-based handheld probe is developed from a commercially available probe originally built to be fiber-coupled to an Nd:YAG OPO laser. We demonstrated on both phantoms and healthy volunteers that the VCSEL-based probe provides promising photoacoustic imaging performance after frame averaging, which is possible because of the high laser repetition rate (1 kHz). We also reported the effect of different laser pulse lengths on image signal-to-noise ratio and system resolution. The VCSELs not only mitigate major limitations of current photoacoustic imaging systems but enable the laser source and the electronics to be integrated directly into handheld probes, thus paving the way for point-of-care photoacoustic imaging.