MRI uses magnetism and radio waves to produce detailed images of soft tissues in the body. It was developed based on principles of nuclear magnetic resonance and the first MRI exam took 5 hours to produce one image. Key components of an MRI scanner include powerful magnets to align hydrogen nuclei in tissues, gradient coils to localize images, and radiofrequency coils to transmit signals and receive returning signals used to construct images. MRI provides advantages over other imaging techniques by using no ionizing radiation and allowing cross-sectional imaging in any plane with good contrast resolution.
This presentation discusees a brief history of the MRI, it's mechanism of action, applications in dentistry and recent advancements in its technology. Also it's advantages and disadvantages in comparison with the CT scan
This presentation discusees a brief history of the MRI, it's mechanism of action, applications in dentistry and recent advancements in its technology. Also it's advantages and disadvantages in comparison with the CT scan
Brief explanation of what is PET, the main components for a PET system along with their basic functions. The principle behind PET inclusive of positron emission and emission detection. Acquisition and reconstruction of the collected data to produce the final image. Finally the pros and cons of Positron emission tomography.
Computed tomography (CT scan) is a medical imaging procedure that uses computer-processed X-rays to produce tomographic images or 'slices' of specific areas of the body. These cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.
Brief explanation of what is PET, the main components for a PET system along with their basic functions. The principle behind PET inclusive of positron emission and emission detection. Acquisition and reconstruction of the collected data to produce the final image. Finally the pros and cons of Positron emission tomography.
Computed tomography (CT scan) is a medical imaging procedure that uses computer-processed X-rays to produce tomographic images or 'slices' of specific areas of the body. These cross-sectional images are used for diagnostic and therapeutic purposes in various medical disciplines.
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Magnetic Resonance Imaging ( MRI ) PresentationReduan Ahmad
MRI :
Big magnet and radio waves take picture inside our body , no radiation involved.
Super clear body pictures, helps doctors see problems with out hunting us .
Secret sauce of MRI , makes detailed pictures possible .
Magnetic resonance imaging (MRI) is a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body
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MRI
• MRI is a radiology technique
• That uses magnetism, radio waves, and a computer to
produce images of body structures.
• MRI is based on the principles of NMR
• In1997 the first MRI exam was performed on a human
being.
• It took 5 hours to produce one image.
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HISTORY
1924 - Pauli
suggests that
nuclear particles
may have
angular
momentum
(spin).
1937 – Rabi
measures magnetic
moment of nucleus.
Coins “magnetic
resonance”.
1985 – Insurance
reimbursements
for MRI exams
NMR renamed
MRI
1920 1930 1940 1950 1960 1970 1980 1990 2000
1946 – Purcell
shows that matter
absorbs energy at a
resonant frequency.
1946 – Bloch
demonstrates that
nuclear precession can
be measured in detector
coils.
1972 –
Damadian
patents idea for
large NMR
scanner to detect
malignant tissue.
1959 – Singer
measures blood
flow using NMR
(in mice).
1973 – Lauterbur
publishes method
for generating
images using
NMR gradients.
1973 –
Mansfield
independently
publishes
gradient
approach t1o9 M75R –. Ernst
develops 2D-Fourier
transform for
MR.
MRI scanners
become clinically
prevalent.
1990 – Ogawa and
colleagues create
functional images
using endogenous,
blood-oxygenation
contrast.
begin.
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NOBAL PRIZES FOR MRI
• 1944: Rabi
Physics (Measured magnetic moment of nucleus)
• 1952: Felix Bloch and Edward Mills Purcell
Physics (Basic science of NMR phenomenon)
• 1991: Richard Ernst
Chemistry (High-resolution pulsed FT-NMR)
• 2002: Kurt Wuthrich
Chemistry (3D molecular structure in solution by NMR)
• 2003: Paul Lauterbur & Peter Mansfield
Physiology or Medicine (MRI technology)
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WHAT CAN BE DIAGNOSED BY AN MRI
SCAN?
• Most ailments of the brain, including tumours
• Sport injuries
• Musculoskeletal problems
• Most spinal conditions/injuries
• Vascular abnormalities
• Female pelvic problems
• Prostate problems
• Some gastrointestinal tract conditions
• Certain ear, nose and throat (ENT) conditions
• Soft tissue and bone pathology/conditions
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WHO CAN’T HAVE AN MRI SCAN?
• A cardiac pacemaker
• Certain clips in your head from brain operations
• A cochlear implant
• A metallic foreign body in your eye
• Had surgery in the last 8 weeks
• If you are pregnant
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PRINCIPLE
• MRI makes use of the magnetic properties of certain
atomic nuclei.
• Hydrogen nucleus (single proton) present in water
molecules, and therefore in all body tissues.
• The hydrogen nuclei partially aligned by a strong
magnetic field in the scanner.
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CONTI..
• The nuclei can be rotated using radio waves, and they
subsequently oscillate in the magnetic field while returning
to equilibrium.
• Simultaneously they emit a radio signal.
• This is detected using antennas (coils)
• Very detailed images can be made of soft tissues.
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Randomly arranged
hydrogen atom
After the strong magnetic
field applied
14. MAIN COMPONENTS OF MRI
• Scanner
• Computers
• Recording hardware
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SCANNER
• An MRI scanner is a large tube that contains powerful
magnets.
• Main components of scanner
– Static magnetic field coils
– Gradient coils
– RF (radiofrequency) coils
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Static Magnetic Field Coils
• Three methods to generate magnetic field
1. Fixed magnet
2. Resistive magnet
3. Super conducting magnet
• Fixed magnets and resistive magnets are generally
restricted to field strengths below 0.4t
• High-resolution imaging systems use super conducting
magnets.
• The super-conducting magnets are large and complex
• They need the coils to be soaked in liquid helium to reduce
their temperature to a value close to absolute zero.
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GRADIENT COILS
• Gradient coils are used to produce deliberate variations in
the main magnetic field
• There are usually three sets of gradient coils, one for each
direction.
• The variation in the magnetic field permits localization of
image slices as well as phase encoding and frequency
encoding.
• The set of gradient coils for the z axis are helmholtz pairs,
and for the x and y axis paired saddle coils.
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RADIOFREQUENCY COIL
• RF coils act as transmitter and receiver
• RF coils are the "antenna" of the MRI system
• That transmit the RF signal and receives the return signal.
• They are simply a loop of wire either circular or
rectangular
• Helmholtz pair coils consist of two circular coils parallel
to each other.
• They are used as the z gradient coils in MRI scanners
• Paired saddle coils are also used for the x and y gradient
coils.
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ADVANTAGES OF MRI
• No ionizing radiation
• Variable thickness in any plane
• Better contrast resolution
• Many details without iv contrast
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DISADVANTAGES OF MRI
• Very expensive
• Dangerous for patients with metallic devices placed within
the body
• Difficult to be performed on claustrophobic patients
• Movement during scanning may cause blurry images
• RF transmitters can cause severe burns if mishandled
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FUNCTIONAL MRI
• Since the early 1990s, FMRI has come
• FMRI is based on the same technology as MRI
• FMRI looks at blood flow
• It is a technique for measuring brain activity
• It works by detecting the changes in blood oxygenation and
flow that occur in response to neural activity
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DIFFERENCE BETWEEN MRI AND FMRI
MRI
• Views anatomical
structure
• Focuses on protons in
hydrogen nuclei
• High spatial resolution
• Utilized for
experimental purposes
FMRI
• Views metabolic
function
• Calculates oxygen
levels
• Long-distance
resolution
• Utilized for diagnostic
purposes