Numerical Evaluation of Heating of the Human Head Due to Magnetic Resonance Imaging

2004 ◽  
Vol 51 (8) ◽  
pp. 1301-1309 ◽  
Author(s):  
U.D. Nguyen ◽  
J.S. Brown ◽  
I.A. Chang ◽  
J. Krycia ◽  
M.S. Mirotznik
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Numerical Evaluation ◽  
Human Head ◽  
Resonance Imaging

scholarly journals A numerical study of pre-polarisation switching in ultra-low field magnetic resonance imaging using dynamic permanent magnet arrays

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ruben Pellicer-Guridi ◽  
Michael W. Vogel ◽  
Viktor Vegh ◽  
Jiasheng Su ◽  
Matthew S. Rosen ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Permanent Magnet ◽  
Structural Integrity ◽  
Numerical Study ◽  
Human Head ◽  
Von Mises Stress ◽  
Resonance Imaging ◽  
Polarisation Field ◽  
Low Field

Abstract Dynamically adjustable permanent magnet arrays have been proposed to generate switchable magnetic fields for pre-polarisation in Ultra-Low Field magnetic resonance imaging. However, the optimal switching dynamics of the pre-polarisation magnetic field as well as the energy requirements, mechanical forces and stresses during switching of the pre-polarisation field have not been evaluated. We analysed these requirements numerically and estimated the magnetic resonance signal strength and image quality for two practical switching modes in an instrument suitable for scanning the human head. Von Mises stress analysis showed that although magnetic forces were significantly higher for two specific rungs, the structural integrity of magnet rungs would not be compromised. Our simulations suggest that a significantly higher signal yield is obtained by switching off the pre-polarisation field with the angular velocity in each rung dependent on its location.

scholarly journals Eyes as Gateways for Environmental Light to the Substantia Nigra: Relevance in Parkinson’s Disease

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Stefania Romeo ◽  
Daniela Di Camillo ◽  
Alessandra Splendiani ◽  
Marta Capannolo ◽  
Cristina Rocchi ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Computed Tomography ◽  
Magnetic Resonance ◽  
Light Intensity ◽  
Substantia Nigra ◽  
Light Exposure ◽  
Bright Light ◽  
Human Head ◽  
Resonance Imaging ◽  
Environmental Light

Recent data indicates that prolonged bright light exposure of rats induces production of neuromelanin and reduction of tyrosine hydroxylase positive neurons in thesubstantia nigra. This effect was the result of direct light reaching thesubstantia nigraand not due to alteration of circadian rhythms. Here, we measured the spectrum of light reaching thesubstantia nigrain rats and analysed the pathway that light may take to reach this deep brain structure in humans. Wavelength range and light intensity, emitted from a fluorescent tube, were measured, using a stereotaxically implanted optical fibre in the rat mesencephalon. The hypothetical path of environmental light from the eye to thesubstantia nigrain humans was investigated by computed tomography and magnetic resonance imaging. Light with wavelengths greater than 600 nm reached the ratsubstantia nigra, with a peak at 709 nm. Eyes appear to be the gateway for light to the mesencephalon since covering the eyes with aluminum foil reduced light intensity by half. Using computed tomography and magnetic resonance imaging of a human head, we identified the eye and the superior orbital fissure as possible gateways for environmental light to reach the mesencephalon.

Energy Update Restricted Chan–Vese Model for Tumor Extraction from MRI of Human Head Scans

2017 ◽  
Vol 15 (01) ◽  
pp. 1750081
Author(s):  
T. Kalaiselvi ◽  
S. Karthigai Selvi
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Active Contour ◽  
Active Contour Model ◽  
Human Head ◽  
Multiphase Model ◽  
Resonance Imaging ◽  
Qualitative And Quantitative ◽  
Contour Model ◽  
Tumor Extraction

This research paper proposed a newer strategic method for the extraction of tumor from magnetic resonance imaging scans by employing a region-based active contour model (ACM). The earlier methods have applied the process of contour initialization randomly and updating the energy of the contour at every iteration. The proposed method used wavelet-based feature set to initiate the contour and restricts the energy update procedure. The efficiency of the presented technique in terms of tumor extraction is measured through qualitative and quantitative measures further compared with its counterparts Vese–Chan multiphase model, ACM and Selective binary. Gaussian filtering regularized level set and non active contour based models.

Gadolinium-DTPA Enhanced Magnetic Resonance Imaging in Human Head Injury

1990 ◽  
pp. 293-295
Author(s):  
D. A. Lang ◽  
D. M. Hadley ◽  
G. M. Teasdale ◽  
P. Macpherson ◽  
E. Teasdale
Keyword(s):  
Magnetic Resonance Imaging ◽  
Head Injury ◽  
Magnetic Resonance ◽  
Human Head ◽  
Resonance Imaging ◽  
Gadolinium Dtpa
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