Dr. Janek Gröhl Profile

Dr. Janek Gröhl

Research Associate at Cancer Research UK Cambridge Institute

SPIE Involvement:

Author

Publications (27)

Proceedings Article | 13 March 2024 Presentation

Open-source implementation and systematic comparison of image reconstruction algorithms for linear array transducers

Wonseok Choi, Ben Cox, Janek Gröhl, Mengjie Shi

Proceedings Volume PC12842, PC128421B (2024) https://doi.org/10.1117/12.3001124

KEYWORDS: Reconstruction algorithms, Image restoration, Photoacoustic spectroscopy, Algorithm development, Transducers, Photoacoustic imaging, Computer simulations, Opacity, Inverse problems, Detection and tracking algorithms

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Proceedings Article | 13 March 2024 Presentation

Systematically minimizing error sources in double-integrating-sphere measurements

Ran Tao, Janek Gröhl, Sarah Bohndiek

Proceedings Volume PC12833, PC1283301 (2024) https://doi.org/10.1117/12.3002983

KEYWORDS: Distributed interactive simulations, Error analysis, Optical properties, Integrating spheres, Biological samples, Reflectivity, Optical spheres, Monte Carlo methods, Calibration, Absorption

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Proceedings Article | 13 March 2024 Presentation

Bridging the simulation gap in photoacoustic imaging by calibration with tissue-mimicking phantoms

Janek Gröhl, Sandeep Kumar Kalva, Berkan Lafci, Francesca Di Cecio, Daniel Razansky, Sarah Bohndiek

Proceedings Volume PC12842, PC1284218 (2024) https://doi.org/10.1117/12.3001377

KEYWORDS: Calibration, Photoacoustic imaging, Photoacoustic spectroscopy, Optoacoustics, Computer simulations, Photoacoustic tomography, Ultrasonography, Tissues, Modeling, Medical imaging

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Proceedings Article | 13 March 2024 Presentation

Enabling longitudinal quantitative photoacoustic mesoscopy of vascular networks through image co-registration

Thierry Lefebvre, Paul Sweeney, Janek Gröhl, Lina Hacker, Emma Brown, Thomas Else, Mariam-Eleni Oraiopoulou, Algernon Bloom, David Lewis, Sarah Bohndiek

Proceedings Volume PC12842, PC128421G (2024) https://doi.org/10.1117/12.3002744

KEYWORDS: Image segmentation, Photoacoustic spectroscopy, Photoacoustic imaging, Mathematical optimization, Image processing algorithms and systems, Deformation, Image resolution, Education and training, Ear, Deep learning

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SPIE Journal Paper | 20 December 2023 Open Access

Effects of skin tone on photoacoustic imaging and oximetry

Thomas R. Else, Lina Hacker, Janek Gröhl, Ellie V. Bunce, Ran Tao, Sarah E. Bohndiek

JBO, Vol. 29, Issue S1, S11506, (December 2023) https://doi.org/10.1117/12.10.1117/1.JBO.29.S1.S11506

KEYWORDS: Skin, Blood, Photoacoustic spectroscopy, Oxygenation, Monte Carlo methods, Tissue optics, Photoacoustic imaging, Oximetry, Image restoration, Reflectivity

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SignificancePhotoacoustic imaging (PAI) provides contrast based on the concentration of optical absorbers in tissue, enabling the assessment of functional physiological parameters such as blood oxygen saturation (sO2). Recent evidence suggests that variation in melanin levels in the epidermis leads to measurement biases in optical technologies, which could potentially limit the application of these biomarkers in diverse populations.AimTo examine the effects of skin melanin pigmentation on PAI and oximetry.ApproachWe evaluated the effects of skin tone in PAI using a computational skin model, two-layer melanin-containing tissue-mimicking phantoms, and mice of a consistent genetic background with varying pigmentations. The computational skin model was validated by simulating the diffuse reflectance spectrum using the adding-doubling method, allowing us to assign our simulation parameters to approximate Fitzpatrick skin types. Monte Carlo simulations and acoustic simulations were run to obtain idealized photoacoustic images of our skin model. Photoacoustic images of the phantoms and mice were acquired using a commercial instrument. Reconstructed images were processed with linear spectral unmixing to estimate blood oxygenation. Linear unmixing results were compared with a learned unmixing approach based on gradient-boosted regression.ResultsOur computational skin model was consistent with representative literature for in vivo skin reflectance measurements. We observed consistent spectral coloring effects across all model systems, with an overestimation of sO2 and more image artifacts observed with increasing melanin concentration. The learned unmixing approach reduced the measurement bias, but predictions made at lower blood sO2 still suffered from a skin tone-dependent effect.ConclusionPAI demonstrates measurement bias, including an overestimation of blood sO2, in higher Fitzpatrick skin types. Future research should aim to characterize this effect in humans to ensure equitable application of the technology.

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Proceedings Article | 27 March 2023 Poster

Photoacoustic image synthesis with SIMPA: updates and future directions

Kris Dreher, Janek Groehl, Tom Rix, Melanie Schellenberg, Niklas Holzwarth, Jan-Hinrich Noelke, Leonardo Ayala, Lena Maier-Hein, Alexander Seitel

Proceedings Volume PC12379, PC1237931 (2023) https://doi.org/10.1117/12.2649935

KEYWORDS: Photoacoustic spectroscopy, Tissue optics, Acoustics, Photonics, Inverse optics, Visualization, Tissues, Reconstruction algorithms, Optical imaging, Inverse problems

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