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Home > About us > Media > Archived news > 2022 > Henri Decauchy defended his PhD "Physics of cold plasma jets - Fundamental study of guided streamers and applications to oncology"
Henri Decauchy defended his PhD "Physics of cold plasma jets - Fundamental study of guided streamers and applications to oncology"
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On Friday September 30, 2022, Henri Decauchy defended his PhD "Physics of cold plasma jets - Fundamental study of guided streamers and applications to oncology".
Abstract:
Cold plasma jet sources are of major interest for medical applications, especially in oncology. Due to their chemical (production of reactive nitrogen and oxygen species), radiative (UV/visible radiations), thermal and electrical (electric field, current pulses) properties, cold plasma jets constitute an innovative therapeutic tool. Prior to clinical use, it is necessary to understand the fundamental physics mechanisms that govern their operation but also to create /ad hoc/ sources to obtain significant anti-tumour efficacy from tumour models with a poor prognosis. This thesis is therefore positioned at the interface of two parts: on the one hand, a part dedicated to the physics of streamers and cold plasma jet sources carried out at the LPP (Laboratoire de Physique des Plasmas, Paris) and on the other hand, a part dedicated to oncology carried out at the CRSA (Centre de Recherche Saint-Antoine, Paris) and the CRC (Centre de Recherche des Cordeliers, Paris). Firstly, this thesis focuses on a fundamental study dedicated to the physics of propagation and counter-propagation of streamers generated in plasma jets, interacting with 3 types of metallic targets: grounded ring electrode, grounded plane electrode and floating potential grid electrode. These targets correspond to elements that can be integrated into cold plasma jet sources for therapeutic use, in order to guarantee the absence of electrical and thermal risks. Using spectroscopic, electrical and rapid imaging diagnostics, it was possible to identify the existence of negative streamers counter-propagating at higher speeds than the incident streamers.A theoretical model of counter-propagation was thus developed. The addition of a floating potential grid electrode between the tube outlet (plasma source) and the grounded plane electrode allowed the identification of a streamer periodization phenomenon that appears for specific voltage and distance conditions: N streamers reaching the grid (with N between 1 and 6) lead to a single transmitted streamer reaching the target. Based on electrical and optical measurements, a model is proposed to analyse the parameters governing this periodization. This in-depth understanding of streamer-target interactions leads to the possibility of creating cold plasma jet sources for oncological applications, in particular plasma catheters that can be used in endoscopy. Two solid tumour models with a poor prognosis were studied: cholangiocarcinoma (biliary tract cancer) and non-small cell bronchial cancer (lung cancer). In the case of cholangiocarcinoma, in vitro experiments have demonstrated high anti-tumour efficacy, while at the same time offering advantages in terms of biological selectivity. Based on in vivo studies in mouse models and with a view to human applicability, a cold plasma catheter was used in two preclinical models: an ERCP trainer and a porcine post-mortem anatomical model. It was thus possible to demonstrate the absence of electrical and thermal risks. In parallel, the analysis of the effects of cold plasma on non-small cell lung cancer was the subject of 9 in vivo campaigns conducted on murine models during this thesis. Two plasma sources with different electrode configurations were compared, both of which consistently resulted in significant tumour growth inflections (p-value < 10-4). An abscopal effect was also demonstrated on ectopic tumour models.
Jury :
Nofel MERBAHI, Professeur, rapporteur
Philippe GUILLOT, Professeur, rapporteur
Farzaneh AREFI, Professeure, Examinatrice
Augusto STANCAMPIANO, Chargé de recherche, Examinateur
Laura FOUASSIER, Chargée de recherche, Invitée
Isabelle CREMER, Professeure, Invitée
Thierry DUFOUR, Maître de conférences, Directeur de thèse
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