[Membranous occlusion of the inferior vena cava a rare cause of Budd-Chiari syndrome]. / L'occlusion membraneuse de la veine cave inférieure : Une étiologie rare du syndrome de Budd-Chiari.

Rarely encountered in the Western countries, membranous occlusion of the inferior vena cava results from a fibrous thickening of the intima and is commonly located at the orifices of the hepatic veins. To date, two etiopathogenic hypotheses have been formulated: the first, dealing with the embryological aspect, the second, arguing for a thrombotic origin. Nevertheless, several studies are still underway to understand the exact physiopathological mechanism of this obstruction. Among these studies, some suspect the predisposing role of anatomical and infectious factors. On average, it takes 6 years between the beginning of the symptoms and the diagnosis. The later the diagnosis is settled, the higher is the risk of encountering a hepatocellular carcinoma. The most relevant additional examinations to visualize the membrane are the abdominal ultrasound and the cavography. Computed tomography allows to highlight the effects of obstruction on the hepatic parenchyma. Concerning the treatment, many studies showed that angioplasty has an excellent immediate and late efficacy. A few surgical techniques also exist but those are less exploited because of the non invasive aspect and lower morbidity-mortality of the endovascular treatment.

Rarement retrouvée en Occident, l'occlusion membraneuse de la veine cave inférieure résulte d'un épaississement fibreux de l'intima, préférentiellement situé en regard de l'abouchement des veines sus-hépatiques. Jusqu'à ce jour, deux hypothèses étiopathogéniques ont été formulées : l'une considérant plutôt le versant embryologique, l'autre plaidant pour une origine thrombotique. Néanmoins, plusieurs études sont toujours en cours afin de comprendre le mécanisme physiopathologique exact de cette obstruction. Certaines suspectent, notamment le rôle prédisposant de facteurs anatomiques et infectieux. La durée d'évolution des symptômes avant la pose du diagnostic est de 6 ans en moyenne. Plus ce dernier sera tardif, plus la probabilité de se retrouver face à un carcinome hépatocellulaire est importante. Les examens complémentaires de choix afin de visualiser la membrane sont l'échographie abdominale et la cavographie. La tomodensitométrie permet de mettre en évidence les répercussions de l'obstruction sur le parenchyme hépatique. D'un point de vue thérapeutique, plusieurs études ont démontré que l'angioplastie possédait une excellente efficacité immédiate et tardive. Certaines techniques chirurgicales existent également, mais sont peu exploitées en raison du caractère non invasif et de la moindre morbi-mortalité du traitement endovasculaire.

Ultra-fast prompt gamma detection in single proton counting regime for range monitoring in particle therapy.

In order to fully exploit the ballistic potential of particle therapy, we propose an online range monitoring concept based on time-of-flight (TOF)-resolved prompt gamma (PG) detection in a single proton counting regime. In a proof of principle experiment, different types of monolithic scintillating gamma detectors are read in time coincidence with a diamond-based beam hodoscope, in order to build TOF spectra of PG generated in a target presenting an air cavity of variable thickness. Since the measurement was carried out at low beam currents (< 1 proton/bunch) it was possible to reach excellent coincidence time resolutions, of the order of 100 ps (σ). Our goal is to detect possible deviations of the proton range with respect to treatment planning within a few intense irradiation spots at the beginning of the session and then carry on the treatment at standard beam currents. The measurements were limited to 10 mm proton range shift. A Monte Carlo simulation study reproducing the experiment has shown that a 3 mm shift can be detected at 2σ by a single detector of ∼1.4 × 10-3 absolute detection efficiency within a single irradiation spot (∼108 protons) and an optimised experimental set-up.