DEVELOPMENT OF MRI

1
DEVELOPMENT OF MRI

• PREPARED BY
• ZAINAL AHMAD KEU 97020
• SAKINAH HASHIM KEU 97015

2
Content

• What is MRI?
• Basic Theory Of MRI
• The Development Of MRI
• MRI Instrumentation
• MRI Safety Consideration
• Advantages Limitation Of MRI
• Application Of MRI
• How Does MRI Altered The Diagnostic Method?

3
What is MRI????

• is a scanning method that makes use of the
  resonance property found in some of the nucleus
  present in the human body, especially the
  hydrogen nucleus (i.e the proton).
• This is of interest due to its large presence in
  water and body molecules.

4
Basic Theory of MRI

• To obtain an image, patient is placed in a highly
  uniform and static magnetic field
• Magnetized proton within the patient align like a
  small magnet
• A radio frequency(RF) pulses is then utilized to
  create oscillating magnetic field perpendicular
  to the main field from which the nuclei absorb
  energy and move out of the alignment in a state
  of excitation

5
Cont

• As the nuclei return from excitation to
  equilibrium state, a signal is induced in the
  receiver coil.
• The signal is then transformed by a series of
  algorithms into diagnostic images.
• Images based on different tissue characteristics
  can then be obtained by varying the number and
  sequence of pulsed RF fields in order to take
  advantage of magnetic relaxation properties of
  the tissues.

6
The development of MRI -The conception of ideas

• Before the World War II Paul Lauterburs
  conception of ideas.
• Initial experiments on existing NMR machine.
• 1967 - Raymond Damadian proposed the idea of
  detecting cancer using NMR method which is
  utilized in the MRI.

7
The invention process

• April 1969 meeting of the Federation of American
  Societies in Experimental Biology Damadian and
  Freeman Cope succeeded in conducting an
  experiment to detect potassium in bacteria from
  the dead sea.
• Damadian obtained a grant from the national
  Cancer institute that enable him to buy an NMR
  spectrometer and develop a research team.
• 1972 Damadian filed a patent claim for an
  apparatus and method for detecting cancer in
  tissue.

8
Cont

• 1976- a prototype machine of MRI
• July 1977- Damadian accomplished in creating
  crude image of the human chest
• Damadian set up FONAR corporation to produce a
  permanent-magnet MRI machine and introduce it at
  the meeting of American Roentgen Ray Society and
  later that year at the annual meeting of the
  Radiological Society of North America.

9
The MRI instrumentation

• A large, powerful cylindrical magnet with a bore
• A set of electrically conducting gradient coils
• An RF transmitter and receiver
• A computer to control the entire process.
• A cathode ray tube.

10
As the technology evolved

• As the technology of MRI emerged, all
  researchers in biomedical sciences, clinical
  investigators, practicing physicians and
  consumers gather to make a scientific assessment
  of technologies and to seek agreement on their
  safety and effectiveness.

11
QUESTIONS?????

• Are there any contraindications to or risks of
  MRI?
• What are the technological advantages and
  limitations of MRI?

• What are the clinical indications for MRI, and
  how does it alter the diagnostic methods and its
  applications effectiveness?

12
Answers!!!! 1st question.

• Risks related to the static and oscillating
  magnet fields used in MRI
• Adverse biologic effects at high exposure
• Major effect Projectile effect forceful
  attraction of ferromagnetic objects to the magnet
• Endanger the patient with ferromagnetic objects
  embedded in their body i.e. shrapnel, pacemaker
  wires or aneurysm clips

13
Cont..

• Biologic effects ECG changes in T wave
  amplitude and magnetohydrodynamic flow effects
• Appear to be hazardous at fields strength above
  2 tesla
• Electric current induced in conductive tissues
  by rapidly changing gradient fields

14
Cont

• Heating effects in tissues due to circulating
  currents from radio frequency coils
• Care to the patient whose heat loss mechanisms
  are impaired and with hyperpyrexic individuals
• Adjustable pulse sequence prevent excessive
  heat buildup especially in warm and humid
  environments.

15
Cont.

• Caution to the infants, patients requiring
  monitoring and life-support systems and patients
  who are pregnant
• In vitro studies raise the questions of whether
  exposure might pose risks to the developing
  embryo and fetus

16
Answers!!!!!2nd question

• Advantages
• Capability in characterizing and discriminate
  among tissues according to their physical and
  biochemical properties
• Both physiologic and pathologic can be evaluated
• Calcium emits no signal on spin echo images, thus
  tissues surrounded by bone can be imaged
• Beam hardening artifacts are avoided

17
Cont..

• Sectional images of equivalent resolution in any
  projection without moving the patient
• Excellent delineation of anatomic structure
• Para- and super paramagnetic contrast agents
  relatively nontoxic
• Little patient preparation and is noninvasive

18
Disadvantages

• Slow scan acquisition produce an artifacts due to
  biological motion i.e. cardiac, vascular
  respiratory excursion, etc
• Patient experience claustrophobia due to small
  bore of the magnet
• Strong static magnetic field interferes the
  proper function of the usual life-support
  equipment

19
Cont..

• Patients with pacemakers and ferromagnetic
  appliances cannot be studied
• Limitation of the ability in detecting
  pathological calcification in soft tissue and
  tumors
• Greater technological expertise is required for
  MRI utilization

20
Commercial Model Of MRI
Brain scans are acquired from a Magnetic
Resonance Imaging scanner like this.
21
Commercial Model Of MRI
Airis II Open MRI Scanner
22
MRI Application

• Flow imaging (MRI Angiography)
• Diffusion Imaging
• Chemical Shift Imaging (Fat Suppression)
• Echo Planar Imaging (Functional MRI)
• Magnetization Transfer Contrast
• Variable Bandwidth Imaging
• Tissue Classification
• Volume imaging (3-D Imaging)

23
These slices can be rendered into a 3D volume and
then viewed from any plane. From these images the
measurement of the brain volume regions which
play a role in the pathophysiology of disease can
be done.
24
Example hippocampus The measurement of the
volume of a structure by manually tracing it's
outline (using specialised computer software) on
all slices in which it appears. Volumes are
calculated by summing across all slices.
25
How Does MRI Altered The Diagnostic Method??

• Enhanced the diagnosis ability
• Enhanced the study on basic biological processes
  in vivo
• Widely used in central nervous system diagnosing
  since 1980s
• - high quality spatial resolution
• - does not use radiation
• - clear from the attenuation spectrum of
• human body

26
Conclusion

• After being introduced in 1980s, MRI has become
  the major choice of diagnostic imaging technique
  since it is
• Noninvasive
• Appears to be relatively innocuous in clinical
  application
• Involves no exposure to ionizing radiation

27
Conclusion.cont

• However, the full potential of MRI has not been
  reached yet. It requires continuing refinement of
  equipment, contrast agents and software may be
  anticipated. Further study of the long-term
  biologic effects of magnetic fields is required.

28
Thank you