Radiofrequency ablation of small liver malignancies under magnetic resonance guidance: progress in targeting and preliminary observations with temperature monitoring

Objectives: To evaluate the feasibility and effectiveness of magnetic resonance (MR)-guided radiofrequency (RF) ablation for small liver tumours with poor conspicuity on both contrast-enhanced ultrasonography (US) and computed tomography (CT), using fast navigation and temperature monitoring. Methods: Sixteen malignant liver nodules (long-axis diameter, 0.6-2.4cm) were treated with multipolar RF ablation on a 1.5-T wide-bore MR system in ten patients. Targeting was performed interactively, using a fast steady-state free precession sequence. Real-time MR-based temperature mapping was performed, using gradient echo-echo planar imaging (GRE-EPI) and hardware filtering. MR-specific treatment data were recorded. The mean follow-up time was 19 ± 7months. Results: Correct placement of RF electrodes was obtained in all procedures (image update, <500ms; mean targeting time, 21 ± 11min). MR thermometry was available for 14 of 16 nodules (88%) with an accuracy of 1.6°C in a non-heated region. No correlation was found between the size of the lethal thermal dose and the ablation zone at follow-up imaging. The primary and secondary effectiveness rates were 100% and 91%, respectively. Conclusions: RF ablation of small liver tumours can be planned, targeted, monitored and controlled with MR imaging within acceptable procedure times. Temperature mapping is technically feasible, but the clinical benefit remains to be prove

Heterogeneous cavitation from atomically smooth liquid-liquid interfaces

Pressure reduction in liquids may result in vaporization and bubble formation. This thermodynamic process is termed cavitation. It is commonly observed in hydraulic machinery, ship propellers, and even in medical therapy within the human body. While cavitation may be beneficial for the removal of malign tissue, yet in many cases it is unwanted due to its ability to erode nearly any material in close contact. Current understanding is that the origin of heterogeneous cavitation are nucleation sites where stable gas cavities reside, e.g., on contaminant particles, submerged surfaces or shell stabilized microscopic bubbles. Here, we present the finding of a so far unreported nucleation site, namely the atomically smooth interface between two immiscible liquids. The non-polar liquid of the two has a higher gas solubility and acts upon pressure reduction as a gas reservoir that accumulates at the interface. We describe experiments that clearly reveal the formation of cavitation on non-polar droplets in contact with water and elucidate the working mechanism that leads to the nucleation of gas pockets through simulations.Comment: This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in Nature Physics, and is available online at https://doi.org/10.1038/s41567-022-01764-

Inter-fractional Respiratory Motion Modelling from Abdominal Ultrasound: A Feasibility Study

Motion management strategies are crucial for radiotherapy of mobile tumours in order to ensure proper target coverage, save organs at risk and prevent interplay effects. We present a feasibility study for an inter-fractional, patient-specific motion model targeted at active beam scanning proton therapy. The model is designed to predict dense lung motion information from 2D abdominal ultrasound images. In a pretreatment phase, simultaneous ultrasound and magnetic resonance imaging are used to build a regression model. During dose delivery, abdominal ultrasound imaging serves as a surrogate for lung motion prediction. We investigated the performance of the motion model on five volunteer datasets. In two cases, the ultrasound probe was replaced after the volunteer has stood up between two imaging sessions. The overall mean prediction error is 2.9 mm and 3.4 mm after repositioning and therefore within a clinically acceptable range. These results suggest that the ultrasound-based regression model is a promising approach for inter-fractional motion management in radiotherapy

Test

AbstractThis is a test to show that the uploaded resources are available by anyone onlin

Test yareta

AbstractThis is a test to show that the uploaded resources are available by anyone onlin

Boiling core animation

AbstractDynamic series of segmented EPI GRE magnitude data illustrating the occurrence and development of a macroscopic boiling point at the focus, perfused ex vivo kidney, transverse slice, in plane resolution 1 mm x 1 mm

Acoustic simulations prostate transducer

AbstractSimulations acoustiques du transducteur prostate faites début 2018 par OL pour déterminer rapidement les caractéristiques du futur HIFU prostate. Test rapide de faisabilité avant soumission FNS et discussion avec Fraunhofer IBMT

Computer-Aided Intra-Operatory Positioning of an MRgHIFU Applicator dedicated to Abdominal Thermal Therapy using Particle Swarm Optimization

AbstractThis document presents a novel software tool developed to optimize the positioning of a high intensity focused ultrasound transducer (HIFU) dedicated to abdominal thermal therapy

Computer-Aided Intra-Operatory Positioning

AbstractThis document presents a novel software tool developed to optimize the positioning of a high intensity focused ultrasound transducer (HIFU) dedicated to abdominal thermal therapy