Search

This review explores the applications of contrast-enhanced ultrasound (CEUS) in interventional radiology, focusing on its role in endoleak detection after endovascular abdominal aortic aneurysm repair (EVAR), periprocedural thermal ablation guidance, and transarterial chemoembolization (TACE) for hepatocellular carcinoma (HCC). CEUS offers a dynamic assessment for the detection of endoleak following EVAR, facilitating accurate diagnosis and classification. In periprocedural thermal ablation, CEUS enhances target lesion delineation with the visualization of real-time perfusion changes, optimizing treatment strategies and reducing residual tumor rates. Finally, CEUS has demonstrated efficacy in intraprocedural evaluation and postprocedural follow-up in TACE for HCC, offering early detection of residual tumor enhancement and providing an alternative for patients with contraindications to contrast-enhanced computed tomography or magnetic resonance imaging. Overall, CEUS is a versatile and valuable tool with many applications to offer interventional radiologists enhanced diagnostic capabilities and improved patient management. [ABSTRACT FROM AUTHOR]

To generate an understanding of the physiological significance of MR images of Non-Thermal Irreversible Electroporation (NTIRE) we compared the following MR imaging sequences: T1W, T2W, PD, GE, and T2 SPAIR acquired after NTIRE treatment in a rodent liver model. The parameters that were studied included the presence or absence of a Gd-based contrast agent, and in vivo and ex-vivo NTIRE treatments in the same liver. NTIRE is a new minimally invasive tissue ablation modality in which pulsed electric fields cause molecularly selective cell death while, the extracellular matrix and large blood vessels remain patent. This attribute of NTIRE is of major clinical importance as it allows treatment of undesirable tissues near critical blood vessels. The presented study results suggest that MR images acquired following NTIRE treatment are all directly related to the unique pattern of blood flow after NTIRE treatment and are not produced in the absence of blood flow.

Electroporation, is known to induce cell membrane permeabilization in the reversible (RE) mode and cell death in the irreversible (IRE) mode. Using an experimental system designed to produce a continuum of IRE followed by RE around a single electrode we used MRI to study the effects of electroporation on the brain. Fifty-four rats were injected with Gd-DOTA and treated with a G25 electrode implanted 5.5 mm deep into the striata. MRI was acquired immediately after treatment, 10 min, 20 min, 30 min, and up to three weeks following the treatment using: T1W, T2W, Gradient echo (GE), serial SPGR (DCE-MRI) with flip angles ranging over 5-25°, and diffusion-weighted MRI (DWMRI). Blood brain barrier (BBB) disruption was depicted as clear enhancement on T1W images. The average signal intensity in the regions of T1-enhancement, representing BBB disruption, increased from 1887±83 (arbitrary units) immediately post treatment to 2246±94 20 min post treatment, then reached a plateau towards the 30 min scan where it reached 2289±87. DWMRI at 30 min showed no significant effects. Early treatment effects and late irreversible damage were clearly depicted on T2W. The enhancing volume on T2W has increased by an average of 2.27±0.27 in the first 24-48 hours post treatment, suggesting an inflammatory tissue response. The permanent tissue damage, depicted as an enhancing region on T2W, 3 weeks post treatment, decreased to an average of 50±10% of the T2W enhancing volumes on the day of the treatment which was 33±5% of the BBB disruption volume. Permanent tissue damage was significantly smaller than the volume of BBB disruption, suggesting, that BBB disruption is associated with RE while tissue damage with IRE. These results demonstrate the feasibility of applying reversible and irreversible electroporation for transient BBB disruption or permanent damage, respectively, and applying MRI for planning/monitoring disruption volume/shape by optimizing electrode positions and treatment parameters.

Electroporation-based therapies such as electrochemotherapy (ECT) and irreversible electroporation (IRE) are emerging as promising tools for treatment of tumors. When applied to the brain, electroporation can also induce transient blood-brain-barrier (BBB) disruption in volumes extending beyond IRE, thus enabling efficient drug penetration. The main objective of this study was to develop a statistical model predicting cell death and BBB disruption induced by electroporation. This model can be used for individual treatment planning.

Blaser, Couvillon, and Bitterman (2006) presented data obtained with honeybees that in principle challenged all traditional interpretations of blocking. They administered A + followed by either A + or + alone (where + indicates an unconditioned stimulus) and then tested on X. They observed less responding to X when they administered A + than when + alone was administered, a phenomenon they called 'pseudoblocking'. Here we examined pseudoblocking in a rat fearconditioning preparation. In Experiment 1, using a control procedure that was similar to our usual blocking control, we obtained conventional blocking but failed to observe pseudoblocking in our analogue to Blaser et al.'s procedure. In Experiment 2, we used Blaser et al.'s control procedure and again failed to observe the pseudoblocking effect with rats when we used the experimental context as an analogue to the honeybee feeder used by Blaser et al. After reviewing their protocol and previously published studies from their laboratory., we hypothesized that the feeder that they treated as a training context probably served as a punctate cue. We also tested this possibility in Experiment 2, using a punctate cue as a surrogate feeder, and were now able to reproduce their pseudo-blocking phenomena. Our results are consistent with a simple overshadowing account of pseudoblocking, within the framework of existing theories of associative learning, which is not applicable to the conventional blocking paradigm. Thus, blocking remains a real phenomenon that must be addressed by models of associative learning.

Several developments were made in the GATE simulation platform to allow accurate modeling of the count rate performances of PET scanners over a wide range of activity concentrations. A background noise module, a dead time and limited bandwidth modeling for the coincidences, and a delayed coincidence builder were added in the code. The results obtained for the modeling of the ECAT HRRT and Focus 220 scanners with the newly developed modules are discussed. They show that GATE can be used to accurately simulate the single event, prompt coincidence and delayed coincidence rates, from very low activity levels in the field of view up to levels that saturate the acquisition system. The new developments were committed into the public release of GATE, making them available for the whole community, thanks to the open source license under which GATE is published (LGPL). Index Terms--Bandwidth, dead time, GATE, Geant4, memory buffer, Monte Carlo simulation, positron emission tomography.