@article{BaumannPohleZhangetal.2021, author = {Baumann, Elisabeth and Pohle, Ulrike and Zhang, Edward and Allen, Thomas and Villringer, Claus and Pulwer, Silvio and Gerhardt, Holger and Laufer, Jan}, title = {A backward-mode optical-resolution photoacoustic microscope for 3D imaging using a planar Fabry-P{\´e}rot sensor}, series = {Photoacoustics}, volume = {24}, journal = {Photoacoustics}, publisher = {Elsevier}, issn = {2213-5979}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-14701}, pages = {100293}, year = {2021}, abstract = {Optical-resolution photoacoustic microscopy (OR-PAM) combines high spatial resolution and strong absorption-based contrast in tissue, which has enabled structural and spectroscopic imaging of endogenous chromophores, primarily hemoglobin. Conventional piezoelectric ultrasound transducers are typically placed far away from the photoacoustic source due to their opacity, which reduces acoustic sensitivity. Optical ultrasound sensors are an alternative as their transparency allows them to be positioned close to the sample with minimal source-detector distances. In this work, a backward-mode OR-PAM system based on a planar Fabry-P{\´e}rot ultrasound sensor and coaxially aligned excitation and interrogation beams was developed. Two 3D imaging modes, using raster-scanning for enhanced image quality and continuous-scanning for fast imaging, were implemented and tested on a leaf skeleton phantom. In fast imaging mode, a scan-rate of 100,000 A-lines/s was achieved. 3D images of a zebrafish embryo were acquired in vivo in raster-scanning mode. The transparency of the FP sensor in the visible and near-infrared wavelength region makes it suitable for combined functional and molecular imaging applications using OR-PAM and multi-photon fluorescence microscopy.}, language = {en} } @inproceedings{PohleBaumannPulweretal.2019, author = {Pohle, Ulrike and Baumann, Elisabeth and Pulwer, Silvio and Villringer, Claus and Zhang, Edward and Gerhardt, Holger and Laufer, Jan}, title = {Development of a backward-mode photoacoustic microscope using a Fabry-P{\´e}rot sensor}, publisher = {SPIE}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-15349}, pages = {594 -- 598}, year = {2019}, abstract = {Optical-resolution photoacoustic microscopy (PAM) has been shown to enable the acquisition of high resolution (μm) functional and anatomical images. For backward-mode operation, conventional piezoelectric ultrasound transducers need to be placed far away from the signal source due to their opacity and size. This can result in reduced acoustic sensitivity. Planar Fabry-Perot polymer film interferometer (FPI) sensors have the potential to overcome this limitation since they are transparent to the excitation wavelength, can be placed immediately adjacent to the signal source for high acoustic sensitivity, and offer a broadband frequency response (0 -50 MHz). In this study, we present a high frame rate, backward-mode OR-PAM system based on a planar FPI ultrasound sensor. A ns-pulsed laser provides excitation pulses (<200 nJ, maximum pulse repetition frequency = 200 kHz, 532 nm) to generate photoacoustic waves that are detected using a planar FPI sensor interrogated at 765-781 nm. For backwardmode operation and highest acoustic sensitivity, the excitation and interrogation beams are coaxially aligned and rasterscanned. The optical transfer function of the sensor, the spatial resolution and the detection sensitivity were determined to characterise the set-up. Images of a leaf phantom and first in vivo images of zebrafish larvae were acquired. This approach will enable fast 3D OR-PAM with high resolution and high sensitivity for functional and molecular imaging applications. FPI-based ultrasound detection also has the potential to enable dual-mode optical- and acousticresolution PAM and the integration of photoacoustic imaging with purely optical modalities such as multi-photon microscopy.}, language = {en} }