MRI
description
Transcript of MRI
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Magnetic ResonanceImaging
MRI
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Objectives:Discuss the MRI historical development, and to
know the significant person who discovered MRI.MRI discovery time linePersons involvedWhat are their Contributions
Overview of the basic principle of MRIAdvantages of MRI over other ModalitiesDifferent Components of MRI
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MRI Topic 1
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Democritus In early 400B.C
First to theorize that all matter consist of both invisible and indivisible particles
Greeks Also noted and observed that a piece of
amber, when rubbed by fur, would attract specific particles or object.
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AMBER
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MAGNESIA TURKEY
City of Magnesia is the origin of the term magnetism.
Observed that when certain rock formation were spun on their axes, they always and immediately returned to their original orientation. These magnetize structure, which are called lodestone.
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LODESTONE
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BAPTISTE-JOSEPH FOURIERIntroduced a
complex mathematics that translate raw MR signals into spatial location while serving emperor napoleon of France
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Hans Christian Oersted1819 discovered that electricity produces
magnetism when he noted that a compass needle would deflect in the presence of an electric charge.
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Michael FaradayStated and
successfully demonstrated that electricity can produce magnetism.
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Michael FaradayCalculated the
velocity and propagation of electromagnetic waves and predicted the existence of other waves in addition to the ultraviolet and infrared regions.
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Sir James Clerk MaxwellIn 1860 discovered
magnetic lines of force could be mathematically expressed.
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Heinrich Hertz of GermanyIn 1868 discovered
that invisible electromagnetic wave do exist and that all electromagnetic waves are identifiable by their characteristic wave frequency values.
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Heinrich Hertz of GermanyElectromagnetic
spectrum – the categorical arrangement of the wave energies corresponding to their properties, began to take form.
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Wilhelm Conrad RoentgenNov. 8, 1895 discovered the x-ray
Marie CurieIn 1896 discovered the gamma rays by experimenting on radioactive phosphors.
Their discoveries soon demonstrated that high frequency wave energies were identifiable, detectable, measurable and often biologically damaging.
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Post WORLD WAR IISome of the technology advances associated
with the world war 2 laid the groundwork for utilizing sonograpghy (submarine detection) and nuclear medicine (atomic energy) for human.
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Felix Bloch & Edward Purcell1946
Explore the mystery of atom.
They noted that when a test tube sample of a pure substance was magnetically energized and RF bombarded the excited atoms themselves would respond by singing their own atomic ‘’tune’’.
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Felix Bloch & Edward Purcell
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Felix bloch & edward purcellThese tune signal were detected and
recorded into spectroscopic images, corresponding to their frequency values.
Virtually overnight Nuclear Magnetic Resonance (NMR). The prelude to MRI, was about to be born.
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Felix bloch & edward purcellBloch and Purcell were recipients of the Novel
Price in 1952 for their major contribution in uniquely discovering and implementing the use of atomic energy for analytical purposes.
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(BASIC PRINCIPLES) MRI TOPIC 2
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MRIOriginally called Nuclear Magnetic Resonance
or NMR.
“Nuclear” indicated that the radioactive atomic nucleus played an important role.
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Basic Principle of MR
A certain atomic nuclei, if placed in a magnetic field, can be stimulated by (absorb energy from) radio waves of the correct frequency.
Following this stimulation, the nuclei release the extra absorbed energy by transmitting radiowaves (the MR) signal, which can be received by an antenna and analyzed.
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Behavior of a hydrogen nuclei
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Advantages of MRI over other Modalities
1. Contrast Resolution2. Multi-Planar Imaging3. No Radiation
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CONTRAST RESOLUTIONPrincipal advantage of MRI
Allows visualization of low- density objects with similar soft tissue characteristics, such as liver- spleen or white matter – gray matter
It is a function of several intrinsic properties of the tissue being imaged.
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MRI HAS HIGH CONTRAST RESOLUTION
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Multi-Planar Imaging
Ability to obtain direct transverse, sagittal, coronal and oblique plane images
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CORONAL VIEW
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SAGITTAL VIEW TRANSVERSE VIEW
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TRUE OR FALSE?
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NO RadiationMRI does not use Ionizing radiation
MRI uses RF electromagnetic radiation and magnetic fields, which do not cause ionization and therefore do not have associated potentially harmful effects of ionizing radiation
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MRI Hardware
3 main components:
1. Gantry2. Computer3. Operating Console
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GantryIs the large, usually cylindrical device that
accommodates the patient during imaging
MRI gantry does not have moving parts- everything is electronically controlled
The patient aperture is usually 50- 60 cm in diameter
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WHERE IS THE GANTRY??
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RF COILS RF coils which is called the RF probe,
surrounds the patient in this aperture
Gradient coils, shim coils, and in the case of an electromagnetic, primary coils all surrounds the RF probe to produce the static magnetic field
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RF COILS
BODY COIL HEAD COIL
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ComputerSimilar to CT, only faster and bigger
During MRI examination, more data are collected and the computations required are longer and more difficult than the CT
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Operating ConsoleMRI patient does not move
MRI console has RF controls rather than kVp, mA and scan time controls
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MRI OPERATING CONSOLE
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MRI Overview The hydrogen nuclei in the Patient- protons-
behave like tiny magnets
Hydrogen makes up 80 % of all atoms found in the human body, making hydrogen extremely useful for MRI.
Because Hydrogen is a single- charge spinning nucleons, the hydrogen nucleus exhibit relatively strong magnetism
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