Magnetic ResonanceImaging

MRI

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

MRI Topic 1

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.

AMBER

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.

LODESTONE

BAPTISTE-JOSEPH FOURIERIntroduced a

complex mathematics that translate raw MR signals into spatial location while serving emperor napoleon of France

Hans Christian Oersted1819 discovered that electricity produces

magnetism when he noted that a compass needle would deflect in the presence of an electric charge.

Michael FaradayStated and

successfully demonstrated that electricity can produce magnetism.

Michael FaradayCalculated the

velocity and propagation of electromagnetic waves and predicted the existence of other waves in addition to the ultraviolet and infrared regions.

Sir James Clerk MaxwellIn 1860 discovered

magnetic lines of force could be mathematically expressed.

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.

Heinrich Hertz of GermanyElectromagnetic

spectrum – the categorical arrangement of the wave energies corresponding to their properties, began to take form.

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.

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.

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’’.

Felix Bloch & Edward Purcell

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.

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.

END…

(BASIC PRINCIPLES) MRI TOPIC 2

MRIOriginally called Nuclear Magnetic Resonance

or NMR.

“Nuclear” indicated that the radioactive atomic nucleus played an important role.

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.

Behavior of a hydrogen nuclei

Advantages of MRI over other Modalities

1. Contrast Resolution2. Multi-Planar Imaging3. No Radiation

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.

MRI HAS HIGH CONTRAST RESOLUTION

Multi-Planar Imaging

Ability to obtain direct transverse, sagittal, coronal and oblique plane images

CORONAL VIEW

SAGITTAL VIEW TRANSVERSE VIEW

TRUE OR FALSE?

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

MRI Hardware

3 main components:

1. Gantry2. Computer3. Operating Console

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

WHERE IS THE GANTRY??

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

RF COILS

BODY COIL HEAD COIL

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

Operating ConsoleMRI patient does not move

MRI console has RF controls rather than kVp, mA and scan time controls

MRI OPERATING CONSOLE

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

END..