title: Nonconfocal all-optical laser-ultrasound and photoacoustic imaging system for angle-dependent deep tissue imaging.
abstract: Biomedical imaging systems incorporating both photoacoustic (PA) and ultrasound capabilities are of interest for obtaining optical and acoustic properties deep in tissue. While most dual-modality systems utilize piezoelectric transducers, all-optical systems can obtain broadband high-resolution data with hands-free operation. Previously described reflection-mode all-optical laser-ultrasound (LUS) systems use a confocal source and detector; however, angle-dependent raypaths are lost in this configuration. As a result, the overall imaging aperture is reduced, which becomes increasingly problematic with depth. We present a reflection-mode nonconfocal LUS and PA imaging system that uses signals recorded on all-optical hardware to create angle-dependent images. We use reverse-time migration and time reversal to reconstruct the LUS and PA images. We demonstrate this methodology with both a numerical model and tissue phantom experiment to image a steep-curvature vessel with a limited aperture 2-cm beneath the surface. Nonconfocal imaging demonstrates improved focusing by 30% and 15% compared to images acquired with a single LUS source in the numerical and experimental LUS images, respectively. The appearance of artifacts is also reduced. Complementary PA images are straightforward to acquire with the nonconfocal system by tuning the source wavelength and can be further developed for quantitative multiview PA imaging.
authors.affiliation: University of Auckland, Faculty of Science, The Dodd-Walls Centre for Photonic and Quantum Technologies and Department of Physics, Private Bag 92019, Auckland 1010, New Zealand.
authors.forename: Jami L
authors.initials: JL
authors.lastname: Johnson
authors.affiliation: The University of Western Australia, Faculty of Science, School of Physics and School of Earth Sciences, M004 35 Stirling Highway, Crawley, Western Australia 6009, Australia.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Shragge
authors.affiliation: University of Auckland, Faculty of Science, The Dodd-Walls Centre for Photonic and Quantum Technologies and Department of Physics, Private Bag 92019, Auckland 1010, New Zealand.
authors.forename: Kasper
authors.initials: K
authors.lastname: van Wijk
mesh_terms: D016477:Artifacts; D003952:Diagnostic Imaging / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007834:Lasers; D061088:Photoacoustic Techniques; D014465:Ultrasonics