scholarly journals RF Exposure Assessment for Various Poses of Patient Assistant in Open MRI Environment

2021 ◽  
Vol 11 (11) ◽  
pp. 4967
Author(s):  
Seon-Eui Hong ◽  
Sukhoon Oh ◽  
Hyung-Do Choi
Keyword(s):  
Rf Coils ◽  
Rf Coil ◽  
Open Mri ◽  
Rf Exposure ◽  
Open Magnetic Resonance Imaging ◽  
Mri Environment ◽  
Rf Energy ◽  
Magnetic Resonance Imaging Mri ◽  
High Level ◽  
Difference Time

In this study, the radio-frequency (RF) energy exposure of patient assistants was assessed for an open magnetic resonance imaging (MRI) system based on numerical computations of the head and body RF coil. Various poses of the patient assistants were defined to see how poorly they affected the RF energy exposure. For the assessments, the peak spatial-averaged specific absorption rate (SAR) levels were carefully compared with each patient assistant pose based on the finite-difference time domain calculations of RF coil models when the patient was placed in such coils in a 0.3 Tesla open MRI system. Overall, the SAR levels of the patient assistant were much lower than those of the patient. However, significantly increased SAR levels were observed under specific conditions, including a larger loop size of the patient assistants’ arms and a closer distance to the RF coils. A comparably high level of SAR to the patient’s body was also found. More careful investigations are needed to prevent the increase of SAR in patient assistants for open MRI systems at higher field strengths.

scholarly journals Reducing RF-induced Heating near Implanted Leads through High-Dielectric Capacitive Bleeding of Current (CBLOC)

2018 ◽  
Author(s):  
Laleh Golestanirad ◽  
Leonardo M Angelone ◽  
John Kirsch ◽  
Sean Downs ◽  
Boris Keil ◽  
...  
Keyword(s):  
Electrically Conductive ◽  
Tissue Heating ◽  
Rf Exposure ◽  
Fold Reduction ◽  
Implanted Medical Devices ◽  
Rf Energy ◽  
Magnetic Resonance Imaging Mri ◽  
Novel Concept ◽  
High Dielectric ◽  
To Receive

AbstractPatients with implanted medical devices such as deep brain stimulation or spinal cord stimulation are often unable to receive magnetic resonance imaging (MRI). This is because once the device is within the radiofrequency (RF) field of the MRI scanner, electrically conductive leads act as antenna, amplifying the RF energy deposition in the tissue and causing possible excessive tissue heating. Here we propose a novel concept in lead design in which 40cm lead wires are coated with a ~1.2mm layer of high dielectric constant material (155 < εr < 250) embedded in a weakly conductive insulation (σ = 20 S/m). The technique called High-Dielectric Capacitive Bleeding of Current, or CBLOC, works by forming a distributed capacitance along the lengths of the lead, efficiently dissipating RF energy before it reaches the exposed tip. Measurements during RF exposure at 64 MHz and 123 MHz demonstrated that CBLOC leads generated 20-fold less heating at 1.5 T, and 40-fold less heating at 3 T compared to control leads. Numerical simulations of RF exposure at 297 MHz (7T) predicted a 15-fold reduction in specific absorption rate (SAR) of RF energy around the tip of CBLOC leads compared to control leads.

Top-Ten Tips for Imaging the Brachial Plexus with Ultrasound and MRI

2019 ◽  
Vol 23 (04) ◽  
pp. 405-418 ◽  
Author(s):  
James F. Griffith ◽  
Radhesh Krishna Lalam
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Brachial Plexus ◽  
Muscle Denervation ◽  
Resonance Imaging ◽  
Neural Injury ◽  
Clinical Indications ◽  
Magnetic Resonance Imaging Mri ◽  
High Level ◽  
Extensive Involvement

AbstractWhen it comes to examining the brachial plexus, ultrasound (US) and magnetic resonance imaging (MRI) are complementary investigations. US is well placed for screening most extraforaminal pathologies, whereas MRI is more sensitive and accurate for specific clinical indications. For example, MRI is probably the preferred technique for assessment of trauma because it enables a thorough evaluation of both the intraspinal and extraspinal elements, although US can depict extraforaminal neural injury with a high level of accuracy. Conversely, US is probably the preferred technique for examination of neurologic amyotrophy because a more extensive involvement beyond the brachial plexus is the norm, although MRI is more sensitive than US for evaluating muscle denervation associated with this entity. With this synergy in mind, this review highlights the tips for examining the brachial plexus with US and MRI.

scholarly journals Complete heart block in cardiac sarcoidosis reversed by corticosteroid therapy: time course of resolution

2021 ◽  
Vol 14 (3) ◽  
pp. e240834
Author(s):  
Anna Tomdio ◽  
Huzaefah Syed ◽  
Kenneth Ellenbogen ◽  
Jordana Kron
Keyword(s):  
Heart Block ◽  
Time Course ◽  
Cardiac Sarcoidosis ◽  
Complete Heart Block ◽  
Positron Emission ◽  
Av Conduction ◽  
Magnetic Resonance Imaging Mri ◽  
High Level ◽  
Active Inflammation ◽  
Lateral Walls

A 53-year-old man was admitted for recurrent syncope and found to have complete heart block (CHB). Cardiac magnetic resonance imaging MRI) showed extensive patchy late gadolinium enhancement in the apical and lateral walls, consistent with cardiac sarcoidosis (CS) but no scar in the septum. A fluorodeoxyglucose (FDG)–positron emission tomography showed FDG uptake in the septum and basal lateral walls. Imaging suggested active inflammation in the septum affecting atrioventricular (AV) conduction but no irreversible fibrosis. Diagnosis of isolated CS requires a high level of suspicion and multidisciplinary teamwork involving heart failure specialists, electrophysiologists and rheumatologists. After specialist and patient discussion, treatment of the disease was initiated with prednisone 40 mg daily, 11 months after presenting with CHB. Three weeks later, ECG with pacing inhibited showed second-degree AV block Mobitz type II and 4 weeks later, AV conduction recovery. This highlights the importance of immediate therapy in reversing AV conduction abnormalities in CS.

scholarly journals Model forB1Imaging in MRI Using the Rotating RF Field

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Adnan Trakic ◽  
Jin Jin ◽  
Ewald Weber ◽  
Stuart Crozier
Keyword(s):  
Degrees Of Freedom ◽  
Acoustic Noise ◽  
Bloch Equation ◽  
Gradient Coil ◽  
Imaging Method ◽  
Nonuniform Field ◽  
Rf Coil ◽  
Image Encoding ◽  
Magnetic Resonance Imaging Mri ◽  
Space Requirements

Conventionally, magnetic resonance imaging (MRI) is performed by pulsing gradient coils, which invariably leads to strong acoustic noise, patient safety concerns due to induced currents, and costly power/space requirements. This modeling study investigates a new silent, gradient coil-free MR imaging method, in which a radiofrequency (RF) coil and its nonuniform field (B1+) are mechanically rotated about the patient. The advantage of the rotatingB1+field is that, for the first time, it provides a large number of degrees of freedom to aid a successfulB1+image encoding process. The mathematical modeling was performed using flip angle modulation as part of a finite-difference-based Bloch equation solver. Preliminary results suggest that representative MR images with intensity deviations of <5% from the original image can be obtained using rotating RF field approach. This method may open up new avenues towards anatomical and functional imaging in medicine.

scholarly journals An Antenna-Theory Method for Modeling High-Frequency RF Coils: A Segmented Birdcage Example

2008 ◽  
Vol 2008 ◽  
pp. 1-10 ◽  
Author(s):  
Xin Chen ◽  
Victor Taracila ◽  
Timothy Eagan ◽  
Hiroyuki Fujita ◽  
Xingxian Shou ◽  
...  
Keyword(s):  
High Frequency ◽  
Dipole Antenna ◽  
Rf Coils ◽  
Optimized Design ◽  
Theory Method ◽  
Rf Coil ◽  
Field Approach ◽  
Antenna Theory ◽  
Target Field ◽  
Tem Mode

We suggest that center-fed dipole antenna analytics can be employed in the optimized design of high-frequency MRI RF coil applications. The method is illustrated in the design of a single-segmented birdcage model and a short multisegmented birdcage model. As a byproduct, it is shown that for a long single-segmented birdcage model, the RF field within it is essentially a TEM mode and has excellent planar uniformity. For a short shielded multisegmented birdcage model, the RF field is optimized with a target-field approach with an average SAR functional. The planar homogeneity of the optimized RF field is significantly improved compared with that of a single-segmented birdcage model with the same geometry. The accuracy of the antenna formulae is also verified with numerical simulations performed via commercial software. The model discussed herein provides evidence for the effectiveness of antenna methods in future RF coil analysis.

Robot-assisted MRI-guided prostatic interventions

Robotica ◽  
2009 ◽  
Vol 28 (2) ◽  
pp. 215-234 ◽  
Author(s):  
Andrew A. Goldenberg ◽  
John Trachtenberg ◽  
Yang Yi ◽  
Robert Weersink ◽  
Marshall S. Sussman ◽  
...  
Keyword(s):  
Thermal Ablation ◽  
Pulse Sequences ◽  
Robot Assisted ◽  
Surgical Ablation ◽  
Image Guided ◽  
Surgical Tool ◽  
Mri Environment ◽  
Focal Ablation ◽  
Mri Guided ◽  
Magnetic Resonance Imaging Mri

SUMMARYThis paper reports on recent progress made toward the development of a new magnetic resonance imaging (MRI)-compatible robot-assisted surgical system for closed-bore image-guided prostatic interventions: thermal ablation, radioactive seed implants (brachytherapy), and biopsy. Each type of intervention will be performed with a different image-guided, robot-based surgical tool mounted on the same MRI-guided robot through a modular trocar. The first stage of this development addresses only laser-based focal ablation. The robot mechanical structure, modular surgical trocar, control architecture, and current stage of performance evaluation in the MRI environment are presented. The robot actuators are ultrasonic motors. A methodology of using such motors in the MRI environment is presented. The robot prototype with surgical ablation tool is undergoing tests on phantoms in the MRI bore. The tests cover MRI compatibility, image visualization, robot accuracy, and thermal mapping. To date, (i) the images are artifact- and noise-free for certain scanning pulse sequences; (ii) the robot tip positioning error is less than 1.2 mm even at positions closer than 0.3 m from the MRI isocenter; (iii) penetration toward the target is image-monitored in near-real time; and (iv) thermal ablation and temperature mapping are achieved using a laser delivered on an optical fiber and MRI, respectively.

Biomedical Image Processing Overview

2016 ◽  
pp. 1-12 ◽  
Author(s):  
Monia Mannai Mannai ◽  
Wahiba Ben Abdessalem Karâa
Keyword(s):  
Image Processing ◽  
Medical Imaging ◽  
Medical Image Processing ◽  
Main Process ◽  
Nuclear Medicine Imaging ◽  
Biomedical Image Processing ◽  
Biomedical Image ◽  
X Ray Computed ◽  
Magnetic Resonance Imaging Mri ◽  
High Level

Over the years, there are different sorts of medical imaging have been developed. Where the most known are: X-ray, computed tomography (CT), nuclear medicine imaging (PET, SPECT), ultrasound and magnetic resonance imaging (MRI), each one has its different utilities. Various studies in biomedical informatics present a process to analyze images for extracting the hidden information which can be used after that. Image analysis combines several fields that are classified into two categories; the process of low-level, that requires very little information about the content image and the process of high-level, which may need information about the image content. The topic of this chapter is to introduce the different techniques for medical image processing and to present many research studies in this domain. It includes four stages, firstly, we introduce the most important medical imaging modalities and secondly, we outline the main process of biomedical image.

Radial magnetic resonance imaging (MRI) using a rotating radiofrequency (RF) coil at 9.4 T

2017 ◽  
Vol 31 (2) ◽  
pp. e3860 ◽  
Author(s):  
Mingyan Li ◽  
Ewald Weber ◽  
Jin Jin ◽  
Thimo Hugger ◽  
Yasvir Tesiram ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Rf Coil ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri

Precision of a Novel Vertebral Motion Analysis System: Preliminary Results

2012 ◽  
Author(s):  
Matthew S. Yeager ◽  
Daniel J. Cook ◽  
Boyle C. Cheng
Keyword(s):  
Muscle Activation ◽  
X Rays ◽  
Current Standard ◽  
Body Depth ◽  
Standard Of Practice ◽  
Static Images ◽  
Magnetic Resonance Imaging Mri ◽  
Analysis System ◽  
High Level ◽  
Relative Change

Imaging modalities such as X-Ray, computerized tomography (CT), magnetic resonance imaging (MRI), and bone scan have all become essential to the evaluation of bone and soft tissue in patients with back pain. All techniques provide valuable static images of the spine, yet lack the capability of providing detailed information about spinal motion. Dynamic end-range x-rays, the standard in assessment of range of motion and vertebral translation, are taken at the patient’s maximum voluntary bending angle in flexion and extension (FE) and/or lateral bending (LB). The current standard of practice is to measure, with ruler and protractor, the relative change between adjacent vertebrae at each bending extreme. The resulting rotational or translational values are then expressed as the intervertebral angle (IVA) or as a percentage of vertebral body depth, respectively. This method, however, is subject to a high level of patient, imaging site, and observer related variability, in the form of uncontrolled bending angles, disparities in equipment and practices, and manual image analysis. An additional limitation of static imagery is the inability to assess motion in the spine as it traverses between end ranges. This information may expose motion abnormalities that occur mid-range that might otherwise be missed by clinicians. Lastly, motion of the spine may present differently in weighted and un-weighted positions. Effects of muscle activation and gravitational forces are not accounted for by current standards.

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