Microwavephysics and Atmospheric Physics
Biomedizinische Photonik
HS 2018  ·  FS 2018
HS 2017  ·  FS 2017
HS 2016  ·  FS 2016
HS 2015  ·  FS 2015
HS 2014  ·  FS 2014
HS 2013  ·  FS 2013
HS 2012  ·  FS 2012
Ultrafast Science and Technology
Last update: 22.11.2018
HS 2018: Seminare über Biomedizinische Photonik
Wednesday 10-12
Vorträge, die innerhalb der nächsten Tage stattfinden, sind speziell markiert.
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Mittwoch, 26.09.2018

Polarimetric microscopy : Preliminary study with PVDFhfp scaffolds

Zeit: 10:15 Uhr
Hörsaal: A97
 
Arushi Jain
Institute of Applied Physics
University of Bern

Light propagation in fibrous tissue plays a fundamental role in the development of novel and minimally invasive diagnosis techniques. For this purpose, we use a polarimetric microscope that operates in the backscattering geometry. Our apparatus has been thoroughly calibrated and verified with experiments and Monte Carlo simulations on well characterized colloidal suspensions. In this study, we investigate the feasibility of retrieving structural information on multiply scattering, fibrous electrospun scaffolds consisting of PVDFhfp nanofibers. These nanofibers display various degrees of structural alignment and the structural anisotropy manifests itself in optical birefringence. We probed these scaffolds with a focused near-infrared light beam at three pairs of crosspolarized states and recorded images of the Stokes vector elements of the light backscattered at the surfaces of the scaffolds. Our preliminary results demonstrate that it is possible to structurally differentiate the scaffolds by analyzing the spatial variations of the degree of linear polarization. We will additionally show the possibility of retrieving the orientation of the fibers from the Stokes vector elements.

 
Mittwoch, 03.10.2018

Optoacoustic multiple irradiation sensing for the determination of blood oxygen saturation levels in vivo: data analysis and preliminary results

Zeit: 10:15 Uhr
Hörsaal: A97
 
Leonie Ulrich
Institute of Applied Physics
University of Bern

Multi-wavelength optoacoustic (OA) imaging allows for the assessment of blood oxygen saturation (SO2) levels in vessels. However, the wavelength-dependent attenuation of light in tissue leads to a spectral distortion of the OA signals and thus to an erroneous estimation of SO2. To correct the OA spectra, we use multiple irradiation sensing: OA images are acquired with multiple irradiation positions, and a semi-empirical model is applied to estimate the effective attenuation coefficient of the probed tissue. SO2 levels are then determined by pixelwise performing numerical fits of blood spectra to the corrected data, and a statistical analysis is carried out to reduce the uncertainty of the outcomes. This work is a continuation of research that has previously been conducted in our group. Based on the latest in vivo data sets acquired in a forearm of a volunteer, we are revising the analysis of the data and investigating the challenges of a robust quantitative evaluation in an in vivo setting. In this seminar, we will have a closer look at the different steps of the analysis and discuss first preliminary results.

 
Mittwoch, 10.10.2018

Computed Ultrasound Tomography in Echo Mode for Speed of sound imaging towards Arterial Plaque imaging: Progresses and Constraints

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Maju Kuriakose
Institute of Applied Physics
University of Bern

Computed Ultrasound Tomography in Echo Mode (CUTE) has been developed to image speed of sound of the biological tissues using the clinical ultrasound data. CUTE was developed based on transmit beam steering approach. This would make difficulties in flowing (like blood) biological regions. So, a new approach based on receive beam steering is developed in order to tackle these issues. In this seminar I will discuss about the progresses in this new approach and the practical constraints that we face for in vivo situations.

 
Mittwoch, 17.10.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Mittwoch, 24.10.2018

Echo motion tracking in ultrasound imaging

Zeit: 10:15 Uhr
Hörsaal: A97
 
Dr. Michael Jaeger
Institute of Applied Physics
University of Bern

Tracking echo motion is important in various application of medical ultrasonography. The most classical use is maybe for blood flow imaging, but newer applications include elastography and speed-of-sound imaging. In this talk I will introduce various different techniques that have been used for motion tracking in ultrasonography, and discuss their specific properties. This leads to some of my own developments, which recently became important for our Cvent project where the challenge is to track the carotid artery wall for motion compensation of optoacoustic images.

 
Mittwoch, 31.10.2018

Towards stable inversion of the CUTE forward model

Zeit: 10:15 Uhr
Hörsaal: A97
 
Patrick Stähli
Institute of Applied PhysicsUniversity of Bern

Computed ultrasound tomography in echo mode (CUTE) is an imaging modality that allows determining the spatial distribution of speed-of-sound inside tissue using handheld echo ultrasound. When changing the transmit and/or receive beam steering angle, the changing local phase of beamformed echoes are determined. The core of CUTE is the model of how the spatial distribution of SoS is related to the spatial distribution of echo phase shift. The inverse problem of reconstructing the SoS from the echo phase shift is ill-posed. To provide a result that is robust against noise and small model errors, we therefore use a regularized least-squares (RLS) solution for the model inversion. In this seminar, I will focus on how RLS in conventional CUTE stabilizes the least-squares solution. Furthermore, I will introduce a probabilistic interpretation of the regression problem, which potentially leads to a more stable SoS reconstruction in in-vivo situations.

 
Mittwoch, 07.11.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Mittwoch, 14.11.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Mittwoch, 21.11.2018

Methods of Quantifying Image Quality for the Comparison of Optoacoustic Image Reconstruction Algorithms

Zeit: 10:15 Uhr
Hörsaal: A97
 
Florentin Spadin
Institute of Applied Physics
University of Bern

Image reconstruction is important for many biomedical imaging modalities, and so is correctly assessing the quality of images. Methods for the quantification of image quality in terms of resolution, contrast and detectability are explored and evaluated in the context of phantom and in-vivo images obtained with our optoacoustic microscopy setup.

 
Mittwoch, 28.11.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Mittwoch, 05.12.2018

Construction Of A Confocal Fluorescence Microscope

Zeit: 10:15 Uhr
Hörsaal: A97
 
Grace Bramer
Institute of Applied Physics
University of Bern

Fluorescence microscopy provides microscope quality images with quantitive as well as structural information about a sample. A method for the construction and alignment of a confocal fluorescence microscope is presented along with a brief look at the advantages of fluorescence measurement.

 
Mittwoch, 12.12.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97
 

 
Mittwoch, 19.12.2018

No seminar

Zeit: 10:15 Uhr
Hörsaal: A97