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Speckle-free laser illumination for microscopic imaging on a nanosecond timescale
Shedding light on the nanosecond dynamics of microbubble ultrasound contrast agents used as targetable drug carriers requires ultra-fast microscopic imaging techniques and extremely high light intensities. In this project we aim to make use of lasers to create a sufficiently powerful light source.
Microbubble ultrasound contrast agents have been used for more than two decades to enhance contrast in medical ultrasound imaging. Recently, such agents have demonstrated an enormous potential in microbubble-mediated focused ultrasound therapies such as blood-brain barrier opening and sonoporation, which employ the acoustic cavitation of microbubbles to non-invasively deliver drugs to a targeted region. To foster their translation to clinical practice, a full understanding of the bubble dynamics that stimulates drug uptake must be achieved.
Revealing the nanosecond dynamics of such micrometric objects necessitates ultra-fast microscopic imaging techniques and, consequently, extremely high light intensities, motivating the use of lasers as light sources. However, due to their long spatial coherence length, they introduce artifacts in microscopic images, such as subjective speckles, a random granular pattern originating from interference between highly coherent light and its backreflections from rough surfaces. Therefore, to make lasers a suitable light source for imaging, it is necessary to implement speckle reduction methods.
Microbubble ultrasound contrast agents have been used for more than two decades to enhance contrast in medical ultrasound imaging. Recently, such agents have demonstrated an enormous potential in microbubble-mediated focused ultrasound therapies such as blood-brain barrier opening and sonoporation, which employ the acoustic cavitation of microbubbles to non-invasively deliver drugs to a targeted region. To foster their translation to clinical practice, a full understanding of the bubble dynamics that stimulates drug uptake must be achieved.
Revealing the nanosecond dynamics of such micrometric objects necessitates ultra-fast microscopic imaging techniques and, consequently, extremely high light intensities, motivating the use of lasers as light sources. However, due to their long spatial coherence length, they introduce artifacts in microscopic images, such as subjective speckles, a random granular pattern originating from interference between highly coherent light and its backreflections from rough surfaces. Therefore, to make lasers a suitable light source for imaging, it is necessary to implement speckle reduction methods.
The goal of this project is to build a speckle-free laser illumination system without relying on moving fibers, diffusers, screens or other moving components. Our strategy is to deliver laser illumination light to the image plane through a highly multimode optical fiber to perform spatial decoherence. This approach will be validated carrying out high-speed imaging experiments: shock wave velocimetry based on dual-pulse nanosecond laser illumination and microbubble ultrasound-induced displacement measurement based on continuous laser illumination. If the performance assessment is positive and if time allows the system will be scaled up to be used in an ultra-high-speed videomicroscopy setup to study the dynamics of microbubble ultrasound contrast agents.
The goal of this project is to build a speckle-free laser illumination system without relying on moving fibers, diffusers, screens or other moving components. Our strategy is to deliver laser illumination light to the image plane through a highly multimode optical fiber to perform spatial decoherence. This approach will be validated carrying out high-speed imaging experiments: shock wave velocimetry based on dual-pulse nanosecond laser illumination and microbubble ultrasound-induced displacement measurement based on continuous laser illumination. If the performance assessment is positive and if time allows the system will be scaled up to be used in an ultra-high-speed videomicroscopy setup to study the dynamics of microbubble ultrasound contrast agents.
For additional information, the candidates can contact Marco Cattaneo via email (mcattaneo at ethz.ch)
For additional information, the candidates can contact Marco Cattaneo via email (mcattaneo at ethz.ch)