scholarly journals Dosimetric Feasibility of the Hybrid Magnetic Resonance Imaging (MRI)-Linear Accelerator System for Brain Metastases: The Impact of the Magnetic Field

2016 ◽  
Vol 96 (2) ◽  
pp. E628 ◽  
Author(s):  
C.L. Tseng ◽  
W. Eppinga ◽  
E. Seravalli ◽  
E. Brand ◽  
S. Hackett ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
Brain Metastases ◽  
Linear Accelerator ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
The Impact ◽  
The Magnetic Field ◽  
Accelerator System

A trail of artificial vestibular stimulation: electricity, heat, and magnet

2012 ◽  
Vol 108 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Aasef G. Shaikh
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
Semicircular Canals ◽  
Vestibular Stimulation ◽  
Clinical Neurology ◽  
Ion Currents ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
The Magnetic Field

The interaction between the magnetic field of a magnetic resonance imaging (MRI) machine and ion currents within the inner-ear endolymph results in a Lorentz force. This force produces a pressure that pushes on the cupula within the semicircular canals causing nystagmus and vertigo. Here I discuss several implications of this unique and noninvasive way to stimulate the vestibular system in experimental neurophysiology and clinical neurology.

scholarly journals Influence of Magnetic Field Strength on Magnetic Resonance Imaging Radiomics Features in Brain Imaging, an In Vitro and In Vivo Study

2021 ◽  
Vol 10 ◽  
Author(s):  
Samy Ammari ◽  
Stephanie Pitre-Champagnat ◽  
Laurent Dercle ◽  
Emilie Chouzenoux ◽  
Salma Moalla ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Magnetic Resonance ◽  
Field Strength ◽  
Healthy Volunteers ◽  
Magnetic Field Strength ◽  
Texture Features ◽  
Imaging Biomarkers ◽  
Resonance Imaging ◽  
The Impact

BackgroundThe development and clinical adoption of quantitative imaging biomarkers (radiomics) has established the need for the identification of parameters altering radiomics reproducibility. The aim of this study was to assess the impact of magnetic field strength on magnetic resonance imaging (MRI) radiomics features in neuroradiology clinical practice.MethodsT1 3D SPGR sequence was acquired on two phantoms and 10 healthy volunteers with two clinical MR devices from the same manufacturer using two different magnetic fields (1.5 and 3T). Phantoms varied in terms of gadolinium concentrations and textural heterogeneity. 27 regions of interest were segmented (phantom: 21, volunteers: 6) using the LIFEX software. 34 features were analyzed.ResultsIn the phantom dataset, 10 (67%) out of 15 radiomics features were significantly different when measured at 1.5T or 3T (student’s t-test, p < 0.05). Gray levels resampling, and pixel size also influence part of texture features. These findings were validated in healthy volunteers.ConclusionsAccording to daily used protocols for clinical examinations, radiomic features extracted on 1.5T should not be used interchangeably with 3T when evaluating texture features. Such confounding factor should be adjusted when adapting the results of a study to a different platform, or when designing a multicentric trial.

scholarly journals Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging

2016 ◽  
Vol 2 (1) ◽  
pp. 653-658
Author(s):  
Nicole Hadert ◽  
Qi Liu ◽  
Waldemar Zylka
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Energy Absorption ◽  
Surrounding Tissue ◽  
Small Scale ◽  
Resonance Imaging ◽  
Spine Model ◽  
Implant Size ◽  
Magnetic Resonance Imaging Mri ◽  
The Impact

AbstractMetallic implants in magnetic resonance imaging (MRI) are a potential safety risk since the energy absorption may increase temperature of the surrounding tissue. The temperature rise is highly dependent on implant size. Numerical examinations can be used to calculate the energy absorption in terms of the specific absorption rate (SAR) induced by MRI on orthopaedic implants. This research presents the impact of titanium osteosynthesis spine implants, called spondylodesis, deduced by numerical examinations of energy absorption in simplified spondylodesis models placed in 1.5 T and 3.0 T MRI body coils. The implants are modelled along with a spine model consisting of vertebrae and disci intervertebrales thus extending previous investigations [1], [2]. Increased SAR values are observed at the ends of long implants, while at the center SAR is significantly lower. Sufficiently short implants show increased SAR along the complete length of the implant. A careful data analysis reveals that the particular anatomy, i.e. vertebrae and disci intervertebrales, has a significant effect on SAR. On top of SAR profile due to the implant length, considerable SAR variations at small scale are observed, e.g. SAR values at vertebra are higher than at disc positions.

scholarly journals Optimal orientation for ionization chambers in MRgRT reference dosimetry

2017 ◽  
Vol 3 (2) ◽  
pp. 273-275
Author(s):  
Stefan Pojtinger ◽  
Oliver S. Dohm ◽  
Daniela Thorwarth
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Field ◽  
Linear Accelerator ◽  
Critical Issue ◽  
Resonance Imaging ◽  
Ionization Chambers ◽  
Optimal Orientation ◽  
Magnetic Field Axis ◽  
Medical Linear Accelerator ◽  
The Magnetic Field

AbstractThe interest in hybrid systems combining magnetic resonance imaging and medical linear accelerator (MR-Linac) is rapidly increasing due to the clinical availability of different systems. Reference dosimetry is a critical issue for integrating these devices into clinical practice. However, the response of ionization chambers changes according to the distinct orientation of the chamber with respect to the magnetic field. In this study, we have carried out Monte Carlo simulations to identify an optimal orientation for thimble type chambers in MRgRT reference dosimetry. Our findings suggest that an orientation where the chamber axis is parallel to the magnetic field axis should be preferred.

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