Integrating spectroscopic photoacoustic (PA) imaging into a clinical ultrasound (US) scanner can add a molecular dimension to US, potentially enabling many new clinical applications. Although both modalities can share the same detectors, interleaved spectroscopic PAUS systems are limited because of their high cost, shallow penetration depth, limited view/bandwidth artifacts, challenges in motion and laser fluence correction, and huge clutter signals generated by light absorption in skin that are superimposed on PA signals. Here we demonstrate a fast-sweep approach for hand-held spectroscopic PAUS imaging that solves most integration problems and successfully implements it with a high-end GE VE95 scanner. The core is a unique, compact, tunable (700–900 nm) diode-pumped ns-laser with pulse-to-pulse wavelength switching and external triggering at variable repetition rates up to 1 kHz delivering about 1 mJ energy per pulse. A unique fiber-optic delivery system sequentially (fiber-by-fiber) couples laser pulses into 20 fibers surrounding the PAUS probe using a rotational motor system operating at 3000 rpm. This fast-sweep approach enables robust and direct regional fluence compensation, motion correction and clutter removal. Spectroscopic PAUS operation is achieved by switching wavelengths in a sequence without additional delays and interleaving PA with B-mode US modalities at a 50-Hz overall frame rate.
Pelivanov et al. (Wed,) studied this question.