Speaker: Mr. Baptiste Heiles

Time and Date: 9:00-11:00 am, October 26, 2018

Place: Room 423 of Scientific Building, Handan Campus,Fudan University

Abstract:

Ultrasound localization microscopy has first been demonstrated to overcome the penetration/resolution paradigm [Couture et al IEEE IUS 2011]. Inspired by FPALM in optics and exploiting ultrafast ultrasound imaging, it allowed the reconstruction of a full velocity map of the rat brain vasculature with a micrometric resolution (8 μm) [Errico et al. Nature,2015]. Despite additional successes for tumour imaging [Lin et al, Theranostics, 2017], this plane-by-plane technique suffers from minute-long acquisitions, out-of-plane microbubble and tissue motion which cannot be corrected for [Hingot et al. Ultrasonics 2017] and the loss of information due to the projection of a 3D vascular structure into a 2D image. We’ve successfully demonstrated the possibility to use an isotropic matrix array for 3D in vitro superresolution imaging at high frame rates. We present here the first application of this process in vivo. The 2D matrix array with 1024 elements arranged in a 32x32 isotropic plane was controlled by the customised programmable 1024-channel system presented in [Provost et al. 2014]. Sprague Dawley rats underwent craniotomy surgery. Sonovue microbubbles were injected through a catether in boli of 0.2mL while a Ketamine-Domitor solution was perfused. The brain was insonified with 9MHz plane waves inclined at 12 different angles with a compounded frame rate of up to 500 Hz. The 3D ULM process developed in [Heiles et al, submitted] was used to determine the position of the bubbles, track them and measure velocities. After implementation of this technique on 99900 volumes, a volumetric rendering of rat brain microvasculature was obtained. At 9MHz, the conventional resolution with this 2D array is around 250μm. The theoretical resolution obtainable with the technique proposed here is less than 1μm in the axial direction and around 5μm in lateral and elevational directionTrajectories calculated allowed to yield velocity fields in microvessels of a few cm/s. Volumetric ULM allows to surpass the conventional resolution in 3 dimensions in a large volume with only 200s of acquisitions, however, the limited sensitivity of 2D matrix arrays, the data size, computation and transfer times remain major challenges.

Biography:

Baptiste Heiles was born in France in 1990. He received a Master of Science in General and Civil Engineering from Ecole Normale Superieure Paris Saclay in 2013, the agrégation de Sciences Industrielles in 2014, and a Master of Research in Fluid Mechanics and Heat Transfers from Ecole Centrale de Paris in 2015. Following the work of Yann Desailly and Claudia Errico, he works on exploiting contrast agents for imaging. He focuses on implementing Ultrasound Localization Microscopy (uULM) in volumetric imaging as well as improving ULM in conventional 2D imaging.