ImPhys Seminar

22 May 2017 | 12:45 - 13:30
location: Lecture Room E
by webmaster ImPhys

Lecturers: Hamidreza Heydarian and Verya Daeichin.

Hamidreza Heydarian, TU Delft, Applied science, Imaging physics, PhD student at Quantitative Imaging group


Λ/100 resolution by template-free 2d particle fusion in localization microscopy

Low density labeling and limited photon count of emitters are among the factors that limit the achievable resolution in localization microscopy. This problem can be mitigated if instances of the same structure are fused (combined) properly. Typically, these particles have arbitrary pose, are degraded by low photon count, false localizations and missing labels. If the structure to be imaged is known a priori, one approach is to register all particles on a template. However, it introduces the so-called template bias which can occur if too strong prior knowledge is imposed on the data. To address this issue, two novel template-free data fusion methods are proposed which assume no prior knowledge about the sample. The methods are evaluated on experimental and simulated datasets. Experimental samples consist of logos shaped by DNA-origami and imaged with DNA-PAINT. Using the proposed methods, we achieved FRC resolution of ~4.0 nm while the initial particles have FRC values in the range of 10-30 nm.


Verya Daeichin, TU Delft, Applied science, Imaging Physics, Post-doc at Acoustic Wavefield Imaging  group


From Micro-bubbles to Micro-transducers

This presentation contains the work I have done during my PhD (Micro-ultrasound molecular imaging) and a one year Postdoc (Intravascular photoacoustic imaging) at Erasmus MC as well as a brief overview of the projects I am working on currently at the department of acoustic wavefield imaging since August 2016.

Micro-ultrasound molecular imaging is a technique utilizing high frequency ultrasound imaging and gas filled microbubbles which are capable of targeting particular type of diseased cells within the vascular system. Such a combination allows imaging disease at the molecular level. During my PhD we developed such a technique for visualization and quantification of neovascularization of the carotid atherosclerotic plaque in mice. Neovascularization are known as one of the important risk factors for plaque rupture. One other critical predictor of plaque vulnerability is the fat content within the plaque. The identification of plaque lipid using intravascular photoacoustic imaging was the goal of my one-year Postdoc after my PhD. Photoacoustic imaging can visualize the atherosclerotic plaque composition on the basis of the optical absorption contrast. Most of the photoacoustic energy of human coronary plaque lipids was found to lie in the frequency band between 2 and 15 MHz requiring a very broadband transducer, especially if a combination with intravascular ultrasound is desired. We developed a broadband polyvinylidene difluoride (PVDF) transducer with integrated electronics to match the low capacitance of such a small PVDF element with the high capacitive load of the long cable.

Since august 2016 that I have joined the AWI group, my main research is development of ultrasound matrix transducer for 3D ultrasound imaging. Development of such a technology usually requires fascinating integrated electronics and is extremely challenging from both scientific (design, simulation, characterization and imaging protocols) and engineering (manufacturing and miniaturizing) point of view. Currently we are working on prototyping of 3 variations of such matrixes: Miniaturized transoesophageal matrix probe for monitoring the beating heart in 3D;  Tiling of multiple matrix probes for 3D imaging of carotid artery; and an spiral array without integrated electronics.  








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