A nonparametric temperature controller with nonlinear negative reaction for multi-point rapid MR-guided HIFU ablation.

Magnetic resonance-guided high intensity focused ultrasound (MRgHIFU) is a noninvasive method for thermal ablation, which exploits the capabilities of magnetic resonance imaging (MRI) for excellent visualization of the target and for near real-time thermometry. Oncological quality of ablation may be obtained by volumetric sonication under automatic feedback control of the temperature. For this purpose, a new nonparametric (i.

An experimental model to investigate the targeting accuracy of MR-guided focused ultrasound ablation in liver.

Background: Magnetic Resonance-guided High Intensity Focused Ultrasound (MRgHIFU) is a hybrid technology that aims to offer non-invasive thermal ablation of targeted tumors or other pathological tissues. Acoustic aberrations and non-linear wave propagating effects may shift the focal point significantly away from the prescribed (or, theoretical) position. It is therefore mandatory to evaluate the spatial accuracy of ablation for a given HIFU protocol and/or device.

Experimental methods for improved spatial control of thermal lesions in magnetic resonance-guided focused ultrasound ablation.

Magnetic resonance-guided high-intensity focused ultrasound (MRgHIFU, or MRgFUS) is a hybrid technology that was developed to provide efficient and tolerable thermal ablation of targeted tumors or other pathologic tissues, while preserving the normal surrounding structures. Fast 3-D ablation strategies are feasible with the newly available phased-array HIFU transducers. However, unlike fixed heating sources for interstitial ablation (radiofrequency electrode, microwave applicator, infra-red laser applicator), HIFU uses propagating waves.

Magnetic resonance-guided shielding of prefocal acoustic obstacles in focused ultrasound therapy: application to intercostal ablation in liver.

Objectives: The treatment of liver cancer is a major public health issue because the liver is a frequent site for both primary and secondary tumors. Rib heating represents a major obstacle for the application of extracorporeal focused ultrasound to liver ablation. Magnetic resonance (MR)-guided external shielding of acoustic obstacles (eg, the ribs) was investigated here to avoid unwanted prefocal energy deposition in the pathway of the focused ultrasound beam.

Ultrasonography-based 2D motion-compensated HIFU sonication integrated with reference-free MR temperature monitoring: a feasibility study ex vivo.

Magnetic resonance imaging (MRI) and ultrasonography have been used simultaneously in this ex vivo study for the image-guidance of high intensity focused ultrasound (HIFU) treatment in moving tissue. A ventilator-driven balloon produced periodic and non-rigid (i.e.

ARFI-prepared MRgHIFU in liver: simultaneous mapping of ARFI-displacement and temperature elevation, using a fast GRE-EPI sequence.

MR acoustic radiation force imaging (ARFI) is an elegant adjunct to MR-guided high intensity focused ultrasound for treatment planning and optimization, permitting in situ assessment of the focusing and targeting quality. The thermal effect of high intensity focused ultrasound pulses associated with ARFI measurements is recommended to be monitored on line, in particular when the beam crosses highly absorbent structures or interfaces (e.g.

Reference-free PRFS MR-thermometry using near-harmonic 2-D reconstruction of the background phase.

Proton resonance frequency shift (PRFS) MR thermometry (MRT) is the generally preferred method for monitoring thermal ablation, typically implemented with gradient-echo (GRE) sequences. Standard PRFS MRT is based on the subtraction of a temporal reference phase map and is, therefore, intrinsically sensitive to tissue motion (including deformation) and to external perturbation of the magnetic field. Reference-free (or reference-less) PRFS MRT has been previously described by Rieke and was based on a 2-D polynomial fit performed on phase data from outside the heated region, to estimate the background phase inside the region of interest.