@article{KirchnerVillringerLaufer2023, author = {Kirchner, Thomas and Villringer, Claus and Laufer, Jan}, title = {Evaluation of ultrasound sensors for transcranial photoacoustic sensing and imaging}, series = {Photoacoustics}, volume = {33}, journal = {Photoacoustics}, publisher = {Elsevier}, issn = {2213-5979}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17993}, year = {2023}, abstract = {Photoacoustic imaging through skull bone causes strong attenuation and distortion of the acoustic wavefront, which diminishes image contrast and resolution. As a result, transcranial photoacoustic measurements in humans have been challenging to demonstrate. In this study, we investigated the acoustic transmission through the human skull to design an ultrasound sensor suitable for transcranial PA imaging and sensing. We measured the frequency dependent losses of human cranial bones ex vivo, compared the performance of a range of piezoelectric and optical ultrasound sensors, and imaged skull phantoms using a PA tomograph based on a planar Fabry-Perot sensor. All transcranial photoacoustic measurements show the typical effects of frequency and thickness dependent attenuation and aberration associated with acoustic propagation through bone. The performance of plano-concave optical resonator ultrasound sensors was found to be highly suitable for transcranial photoacoustic measurements.}, language = {en} } @inproceedings{KirchnerVillringerGutkeetal.2023, author = {Kirchner, Thomas and Villringer, Claus and Gutke, Marko and Laufer, Jan}, title = {Plano-concave optical sensor for transcranial photoacoustic measurements}, series = {Opto-Acoustic Methods and Applications in Biophotonics VI}, booktitle = {Opto-Acoustic Methods and Applications in Biophotonics VI}, publisher = {Society of Photo-Optical Instrumentation Engineers (SPIE)}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:526-opus4-17840}, year = {2023}, abstract = {Biomedical photoacoustics is usually used to image absorption-based contrast in soft tissues up to depths of several centimeters and with sub-millimeter resolution. By contrast, measuring Photoacoustic (PA) signals through hard bone tissue shows severe signal degradation due to aberration and high attenuation of high frequency acoustic signal components. This is particularly noticeable when measuring through thicker, human, skull bone. Which is the main reason why transcranial PA imaging in humans has so far proved challenging to implement. To tackle this challenge, we developed an optical resonator sensor based on a previous planar-concave design. This sensor was found to be highly suitable for measuring the low-pressure amplitude and low acoustic frequency signals that are transmitted through human cranial bone. A plano-concave optical resonator sensor was fabricated to provide high sensitivity in the acoustic frequency range of DC to around 2 MHz, a low noise equivalent pressure and a small active element size enabling it to significantly outperform conventional piezoelectric transducers when measuring PA waves transmitted through ex vivo human cranial bones.}, language = {en} }