! POSITION FILLED !
Type of internship
Master 2 internship / engineering school end of study internship
Date or duration of the internship
6-month internship between January and September 2023
Context
Photoacoustic [1] (PA) imaging is an emerging modality that combines optical excitation and ultrasonic detection to map optical absorption to a few centimeters’ depth in biological tissues and with unparalleled resolution (~100 μm). The key element is the photoacoustic effect: optically absorbing structures emit ultrasound when illuminated by a laser pulse. The amplitude of the generated ultrasound depends on the optical absorption at the excitation wavelength. From a sequence of images of the same object but acquired with different wavelengths, it is therefore possible to separate molecular and/or nanoparticle absorbers with different spectra. This type of image is called multispectral and allows for example to quantify the oxygenation of hemoglobin in blood vessels, or to map the distribution of a contrast agent (introductory video here).
PA imaging is inherently 3D due to the volumetric scattering of light in the tissue. 3D information also allows a more detailed understanding of pathologies and their follow-up over time. A scanner combining PA and 3D ultrasound imaging has recently been developed in the laboratory. This scanner relies on reference ultrasound sensor arrays for 2D imaging, linear ultrasound arrays, and on an innovative rotation-translation scan to obtain high quality 3D images. A scanning geometry was initially proposed by J. Gateau et al [2] and was transposed and validated for ultrasound imaging [3] in the laboratory in 2020 (see figure below). The scanner currently allows the simultaneous acquisition of a 3D PA image at one wavelength and a 3D ultrasound image (see figure below). These latest advances are the subject of a presentation at the major international ultrasound conference IEEE IUS 2022.
The developed scanner is based on state-of-the-art research instruments: a programmable ultrasound scanner, high precision motorized stages and a tunable nanosecond laser. The laser available in the laboratory allows to change the excitation wavelength at each laser pulse and thus to consider programming a multispectral acquisition during a single scan. We are currently looking to implement multispectral 3D PA image acquisition and reconstruction, by adjusting the parameters of the current scanner. This project has been recognized by the CNRS as being at the forefront of innovation through 80 PRIME funding and will participate in the development of the instrument used in C. Linger’s thesis.
From left to right: A) Photograph of the scanner based on a rotational-translational motion; B) Photograph of a set of black wires in water; C) 3D ultrasound image shown here with a projection image of the maxima; D) 3D photoacoustic image shown here with a projection image of the maxima. Images C and D were acquired simultaneously and are superimposable. E) Combined US (orange) and PA (blue) image of an imaging phantom with complementary US and PA contrasts (composite color scale shown at right).
1. Beard, P. Biomedical Photoacoustic Imaging. Interface Focus 2011, 1 (4), 602–631. https://doi.org/10.1098/rsfs.2011.0028.
2. Gateau, J.; Gesnik, M.; Chassot, J.-M.; Bossy, E. Single-Side Access, Isotropic Resolution, and Multispectral Three-Dimensional Photoacoustic Imaging with Rotate-Translate Scanning of Ultrasonic Detector Array. J. Biomed. Opt. 2015, 20 (05), 1. https://doi.org/10.1117/1.JBO.20.5.056004.
3. Lucas, T.; Quidu, I.; Bridal, S. L.; Gateau, J. High-Contrast and -Resolution 3-D Ultrasonography with a Clinical Linear Transducer Array Scanned in a Rotate-Translate Geometry. Appl. Sci. 2021, 11 (2), 493. https://doi.org/10.3390/app11020493.
Objective
The objective of the internship is to obtain 3D photoacoustic multispectral images, to characterize the performances of the system in terms of image quality and acquisition speed on imaging phantoms.
Tasks
During the internship, the candidate will adapt the scanning motion of the sensor array, the programming of the instruments and the existing data processing algorithms in the laboratory to separate in 3D absorbing structures containing substances with different absorption spectra. She/he will design and print parts on the 3D printer to make the imaging phantom, prepare samples, program the device to retrieve ultrasound data, make experimental acquisitions of signals from a device present in the laboratory. He/she will process the data to form the 3D images (from programs available in the lab), and analyze the resulting images.
Skills
The proposed internship is mainly experimental, but will also use programming, signal processing and image analysis skills. We are mainly looking for a motivated and rigorous student. Experimental skills and a good knowledge of Matlab programming are highly appreciated.
This internship may lead to a thesis.
Contact
- Jérôme GATEAU, jerome.gateau[at]sorbonne-universite.fr tel : 01.44.27.22.65
- Clément LINGER, clement.linger[at]sorbonne-universite.fr
Location of the internship: Laboratoire d’Imagerie Biomédicale – Équipe Imagerie et développement de nouvelles thérapies, 15 rue de l’École de Médecine, 75006 Paris.