Ultra-broadband axicon transducer for optoacoustic endoscopy

Abstract

Image performance in optoacoustic endoscopy depends markedly on the design of the transducer employed. Ideally, high-resolution performance is required over an expanded depth of focus. Current optoacoustic focused transducers achieve lateral resolutions in the range of tens of microns in the mesoscopic regime, but their depth of focus is limited to hundreds of microns by the nature of their spherical geometry. We designed an ultra-broadband axicon detector with a 2 mm central aperture and investigated whether the imaging characteristics exceeded those of a spherical detector of similar size. We show a previously undocumented ability to achieve a broadband elongated pencil-beam optoacoustic sensitivity with an axicon detection geometry, providing approximately 40 μm-lateral resolution maintained over a depth of focus of 950 μm—3.8 times that of the reference spherical detector. This performance could potentially lead to optoacoustic endoscopes that can visualize optical absorption deeper and with higher resolution than any other optical endoscope today.

360º optoacoustic capsule endoscopy at 50 Hz for esophageal imaging

“…To further increase the sensitivity and imaging depth, a transducer pre-amplification stage can be integrated inside the capsule [21] while focusing the transducer sensitivity towards the surface of the capsule, thereby increasing the SNR for imaging in high scattering media. To increase the resolution of the optoacoustic images, we anticipate that a transducer with higher central frequency and reduced focal length, as currently employed in raster scanning optoacoustic mesoscopy, could be incorporated [10] , [30] . Furthermore, image post-processing techniques can be explored to compensate for motor instability during scans.…”

Photoacoustic Neuroimaging - Perspectives on a Maturing Imaging Technique and its Applications in Neuroscience

“…Furthermore, label-free PA microscopy could accelerate safe diagnosis of the margin of resection during brain surgery. There are currently intense efforts to miniaturize endoscopic PA imaging probes for gastrointestinal indications (Ali et al, 2021) that can likely be extended to lumbar puncture or needlebased biopsies. Image-assistance could thus be provided to these procedures, which may also be augmented by spectroscopy or FDA-approved imaging agents such as ICG.…”

In Vivo Three-Dimensional Raster Scan Optoacoustic Mesoscopy Using Frequency Domain Inversion

“…Here we incorporate the PSF correction factor in the reconstruction problem in the Fourier domain to avoid sacrificing computational time. Note, however, that each position in a defined 3D space has an associated temporal acoustic signal, resulting in a 4D function describing the complete transducer spatial response in the system 50 . Here we obtained the spatial transfer function at a single depth position, reducing it to a 3D function, and show that this simplification holds as a good approximation for locations relatively close to the depth position at which the PSF is measured.…”