  Acoustic lenses made of acrylic plastic (PMMA) have been used to enlarge the
acceptance angle of sensitive large surface area detectors and improve lateral
resolution. However, PMMA lenses introduce image artifacts due to ultrasound
internal reflections within the lenses. In this work we investigated this issue
proposing a new lens material Stycast 1090SI. We characterized the acoustic
properties of the proposed material in comparison with PMMA. Detector
performance using negative lenses with the two materials, was tested using
finite element simulation and experiment. Further the image quality of a
photoacoustic tomography system was studied using k-Wave simulation and
experiment. Our acoustic characterization showed that Stycast 1090SI has
tissue-like acoustic impedance, high speed of sound and low acoustic
attenuation. Both acoustic lenses show significant enlargement of detector
acceptance angle and lateral resolution improvement. However, image artifacts
induced by acoustic lenses are reduced using the proposed lens compared to PMMA
lens.
