EDAP TMS (France)

Therapeutic ultrasound has been the focus of numerous recent investigations. Recent developments such as histotripsy techniques have led to greater electrical solicitation of ultrasound setup with high intensity and short bursts, which can induce potential risks for patients and operators, as well as suboptimal performances. Neither acoustic nor electrical engineering standards are designed for analyzing such signals. Ultrasound setups are usually characterized by voltage-only and wattmeter power measurements under long duration (> 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</i>) and low power (< 100 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i>) conditions. We propose a method based on combined current–voltage (CCV) measurements performed at high temporal resolution to evaluate performance, stability and consistency under short duration (< 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ms</i>) and high power (100 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</i>) conditions. The average power, envelope variation coefficient and overshoot factor were computed under various input signal conditions with precise automatic windowing of the active part of the pulse. CCV measurements were validated against wattmeter measurements for long duration and high-power signals. The instability of a prototype histotripsy setup was characterized to optimize the hardware. Three other ultrasound setups used for histotripsy, HIFU, and cavitation were evaluated and showed stable behavior. This method can be used to characterize electrical signals across a wide range of ultrasound setups, including setups in which traditional techniques are inapplicable. In addition, this method provides quantitative information about RF signal instability and is simple to implement. Electrical measurements are less time-consuming than acoustic measurements, so they are essential for optimizing reproducibility in laboratory settings under rigorous conditions.

High Intensity Focused Ultrasound (HIFU) uses the energy of an ultrasonic beam to cause localized heating to alter or destroy the targeted tissues. Due to its limited collateral effects, this minimally invasive therapy is, in its field of application, an alternative to surgical treatments and is rapidly expanding in terms of both clinical research and industrial development. In this context, the use of simulation is a crucial element to reduce both the development time and prototype costs, as well as the number of preclinical and clinical experiments. To this aim, CEA-LIST has been developing the simulation platform, CIVA HealthCare in partnership with INSERM for several years, which uses optimized and validated modules for the simulation of a whole HIFU therapy protocol. However, multi-parametric studies for treatment optimisation (probe design, protocol definition, etc.), sensitivity analysis, and tissue characterisation are very time-consuming, since they involve many simulations. We propose an alternative solution of replacing the computationally expensive direct solver with a surrogate model built from a database of simulation results. The procedure breaks down into two stages First, the database is adaptively constructed to maximise the fidelity of the associated interpolator computed from the pairs (Input/Output) of the database. Then in the second step, the interpolator, also called surrogate model or metamodel, enables the generation of results in near real time for configurations covered by the range of the database. This procedure and its related tools have been implemented in CIVA-HealthCare. To highlight the potential offered by such intensive HIFU simulation based on surrogate models strategy, two applications are presented: The first concerns real-time pressure field computation, and the second is based on thermal simulations and deals with sensitivity analyses according to uncertainties in tissues parameters. Work supported by French Nation Research Agency (ANR SATURN -15-CE19-0016)

The new family of IR transmitting glasses, the TeX glasses, based on the association of tellurium and halide (Cl, Br, or I) are characterized by a wide optical window extending from 2 to 18 micrometers and a strong stability towards devitrification. Optical fibers drawn from these glasses exhibit low losses in the 7 - 10 micrometers range (less than 1 dB/m for single index fibers, 1 - 2 dB/m for fibers having a core-clad structure). The TeX glass fibers have been used in a remote analysis set-up which is mainly composed of a FTIR spectrometer coupled with a HgCdTe detector. This prototype system permits qualitative and quantitative analysis in a wide wavelength region lying from 3 to 13 micrometers , covering the fundamental absorption of more organic species. The evolution of a lactic and an alcoholic fermentation has been monitored by means of this set-up.

Diamond-like amorphous carbon films on germanium are prepared by plasma decomposition of methane. The optical absorption coefficient dependance in the 8 to 13 &mu;m range with the hydrogen and impurities contents as well as the interface quality are studied by infrared spectroscopy, quantitative microprobe analysis, T.E.M. cross section and ESCA experiments. The film behaviour in severe environmental tests is also reported.