The construction of photoacoustic tomography (PAT) systems that combine tunable laser sources and ultrasound systems
for bimodal imaging and spectroscopic applications such as oximetry presents novel challenges to the biophotonics
researcher. We address some of the design issues, including system synchronization, cross-platform integration, and
image reconstruction algorithms, and present techniques for device performance validation. Our system comprises a
pulsed Nd:YAG laser-pumped optical parametric oscillator for near-infrared tunability and a research-grade ultrasound
acquisition system compatible with multiple clinical transducers to enable wide variation in operating parameters.
Considerations such as pulse energy variability, ultrasound transducer properties, and spectral energy compensation, and
their impact on measurements are presented. Spectral imaging was performed on tissue-simulating phantoms made of a
custom polyvinyl chloride (PVC) plastisol gel designed to mimic both the optical properties (absorption, scattering) and
acoustic properties (sound velocity, attenuation) of human breast tissue. Phantoms contained fluid channels at various
depths which were injected with either oxyhemoglobin or organic dye solutions as absorptive targets. Spectral analysis
of these solutions was performed for channel depths from 0.5 to 3 cm and at radiant exposures up to the ANSI maximum
permissible exposure. Recovered photoacoustic spectra are compared with absorption spectra measured using
spectrophotometry. Results provide insight into the influence of factors that impact the quality of spectroscopic
measurements and reconstructed images in ultrasound-PAT systems.