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Purpose: Magnetic resonance imaging (MRI) is capable of providing valuable real-time feedback during medical procedures, partly due to the excellent soft-tissue contrast available. Several technical hurdles still exist to seamless integration of medical devices with MRI due to incompatibility of most conventional devices with this imaging modality. In this study, the effect of local perturbations in the magnetic field caused by the magnetization of medical devices was examined using finite element analysis modeling. As an example, the influence of the geometric and material characteristics of a transurethral high-intensity ultrasound applicator on temperature measurements using proton resonance frequency (PRF)-shift thermometry was investigated.
Methods: The effect of local perturbations in the magnetic field, caused by the magnetization of medical device components, was examined using finite element analysis modeling. The thermometry artifact generated by a transurethral ultrasound applicator was simulated, and these results were validated against analytic models and scans of an applicator in a phantom. Several parameters were then varied to identify which most strongly impacted the level of simulated thermometry artifact, which varies as the applicator moves over the course of an ablative high-intensity ultrasound treatment.
Results: Key design parameters identified as having a strong influence on the magnitude of thermometry artifact included the susceptibility of materials and their volume. The location of components was also important, particularly when positioned to maximize symmetry of the device. Finally, the location of component edges and the inclination of the device relative to the magnetic field were also found to be important factors.
Conclusions: Previous design strategies to minimize thermometry artifact were validated, and novel design strategies were identified that substantially reduce PRF-shift thermometry artifacts for a variety of device orientations. These new strategies are being incorporated into the next generation of applicators. The general strategy described in this study can be applied to the design of other interventional devices intended for use with MRI.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4691251 | PMC |
http://dx.doi.org/10.1118/1.4938099 | DOI Listing |
Nanoscale
October 2024
Phantom-g, CICECO, Departamento de Física, Universidade de Aveiro, Campus Santiago, Aveiro 3810-193, Portugal.
The quest for enhancing the upconversion luminescence (UCL) efficiency of rare-earth doped materials has been a common target in nanophotonics research. Plasmonic nanoarchitectures have proven potential for amplifying UCL signals, prompting investigations into localized enhancement effects within noble metal nanostructures. In this work we investigate the localized enhancement of UCL in silver nanowire (AgNW) networks coated with upconversion nanoparticles (UCNPs) by employing hyperspectral microscopy to unveil distinctive regions of local enhancement.
View Article and Find Full Text PDFEur Radiol Exp
August 2024
Department of Radiology, LMU University Hospital, LMU Munich, Munich, Germany.
Background: Interventional magnetic resonance imaging (MRI) can provide a comprehensive setting for microwave ablation of tumors with real-time monitoring of the energy delivery using MRI-based temperature mapping. The purpose of this study was to quantify the accuracy of three-dimensional (3D) real-time MRI temperature mapping during microwave heating in vitro by comparing MRI thermometry data to reference data measured by fiber-optical thermometry.
Methods: Nine phantom experiments were evaluated in agar-based gel phantoms using an in-room MR-conditional microwave system and MRI thermometry.
Int J Hyperthermia
July 2024
Department of Radiology and Nuclear Medicine, Erasmus MC, University Medical Center Rotterdam, Rotterdam, the Netherlands.
Sensors (Basel)
May 2024
Imaging Science, University of Rochester Medical Center, Rochester, NY 14642, USA.
The accuracy and efficacy of laser ablation procedures depend on the accurate placement of the laser applicator within the diseased tissue, monitoring the real-time temperature during the ablation procedure, and mapping the extent of the ablated region. Ultrasound (US) imaging has been widely used to guide ablation procedures. While US imaging offers significant advantages for guiding ablation procedures, its limitations include low imaging contrast, angular dependency, and limited ability to monitor the temperature.
View Article and Find Full Text PDFPhys Med Biol
May 2024
Department of Radiology, Mayo Clinic, Rochester, MN, United States of America.
. Conventional computed tomography (CT) imaging does not provide quantitative information on local thermal changes during percutaneous ablative therapy of cancerous and benign tumors, aside from few qualitative, visual cues. In this study, we have investigated changes in CT signal across a wide range of temperatures and two physical phases for two different tissue mimicking materials, each.
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