title: High-frequency annular array with coaxial illumination for dual-modality ultrasonic and photoacoustic imaging.
abstract: This paper presents a combined ultrasound and photoacoustic (PA) imaging (PAI) system used to obtain high-quality, co-registered images of mouse-embryo anatomy and vasculature. High-frequency ultrasound (HFU, >20 MHz) is utilized to obtain high-resolution anatomical images of small animals while PAI provides high-contrast images of the vascular network. The imaging system is based on a 40 MHz, 5-element, 6 mm aperture annular-array transducer with a 800 μm diameter hole through its central element. The transducer was integrated in a cage-plate assembly allowing for a collimated laser beam to pass through the hole so that the optical and acoustic beams were collinear. The assembly was mounted on a two-axis, motorized stage to enable the simultaneous acquisition of co-registered HFU and PA volumetric data. Data were collected from all five elements in receive and a synthetic-focusing algorithm was applied in post-processing to beamform the data and increase the spatial resolution and depth-of-field (DOF) of the HFU and PA images. Phantom measurements showed that the system could achieve high-resolution images (down to 90 μm for HFU and 150 μm for PAI) and a large DOF of >8 mm. Volume renderings of a mouse embryo showed that the scanner allowed for visualizing morphologically precise anatomy of the entire embryo along with corresponding co-registered vasculature. Major head vessels, such as the superior sagittal sinus or rostral vein, were clearly identified as well as limb bud vasculature.
authors.affiliation: Lizzi Center for Biomedical Engineering, Riverside Research, New York, New York 10038, USA.
authors.forename: Erwan
authors.initials: E
authors.lastname: Filoux
authors.forename: Ashwin
authors.initials: A
authors.lastname: Sampathkumar
authors.forename: Parag V
authors.initials: PV
authors.lastname: Chitnis
authors.forename: Orlando
authors.initials: O
authors.lastname: Aristizábal
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Ketterling
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology; D004622:Embryo, Mammalian / Q000098:blood supply; D051379:Mice; D018919:Neovascularization, Physiologic; D061088:Photoacoustic Techniques / Q000295:instrumentation*; D014159:Transducers; D014465:Ultrasonics / Q000295:instrumentation*