This document provides an overview of magnetic resonance imaging (MRI). It discusses the timeline of MRI development, how an MRI machine works, MRI principles regarding proton spin and magnetic fields, T1- and T2-weighted images, and common indications, advantages, disadvantages, and contraindications of MRI. MRI utilizes proton spin and magnetic fields to generate detailed images of internal structures without using ionizing radiation.

2. MAGNENIC RESONANCE IMAGE
( MRI )
DR. MD. SHALEH MAHMUD ASAD
RESIDENT, UROLOGY
PHASE A

3. CONTENTS
• Timeline
• Events in MRI machine
• MRI Principles
• MRI Physics
• T1 & T2 Definition
• Image Contrast
• Indications
• Advantages
• Disadvantages
• Contraindications

4. TIMELINE
 Raymond Vahan Damadian is an Armenian-American
physician inventor of the first MR Scanning Machine.
 Paul Lauterbur , american chemist of the University
of Illinois at Urbana-Champaign
 Sir Peter Mansfield, english physicist of the University
of Nottingham

5.  Patient bathed in a magnetic field
 Field causes some of the body’s nuclei to behave like tiny compasses and
line up
 The nuclei are hit by pulsing radio waves
 Once the pulses stop the nuclei go back to their state induced by the magnet
 Energy now released by the nuclei acts like miniature radio stations giving
out a signal
 Radio waves are picked up by a computer where they are translated into an
image.
EVENTS ON MRI SCANNER

6. MRI Principles
 MRI is based on the principle of nuclear magnetic resonance (NMR)
 Two basic principles of NMR
1. Atoms with an odd number of protons or neutrons have spin
2. A moving electric charge, be it positive or negative, produces a
magnetic field
 MRI utilizes this magnetic spin property of protons of hydrogen to
elicit images

7. WHY HYDROGEN ?
 Has an unpaired proton which is positively charged
 Act as tiny magnet which produces small but noticeable
magnetic field
 Only major species in the body that is MR sensitive
 Abundant in the body in the form of water and fat
So, Essentially all MRI is hydrogen (proton) imaging

8. MRI Physics

9. But why we can’t act like magnets?
 The protons (i.e. Hydrogen ions) in
body are spinning in a haphazard
fashion, and cancel all the
magnetism. That is our natural state!
 We need to discipline them first, how?
 Magnetic field strength : 0.3 – 7 T
(2500 times more than earth’s
magnetic field). Average field
strength – 1.5 T

10. MODERN MRI MACHINE

12. LONGITUDINAL & TRANSVERSE MAGNETIZATION

13. RADIO FREQUENCY IMPULSE

15. T1 Weighted Image :
 Scanning parameters are set ( short TR/short TE ) to minimize T2
relaxation effects.
 Short TR,TE = High signal = Brighter Image
 Long TR,TE = Low Signal = Darker Image
 Tissues with high fat content appear bright and compartments filled with
water appears dark.
 Good for demonstrating anatomy used to differentiate anatomical
structures mainly on the basis of T1 values.

16. T2-weighted image :
 the scanning parameters are set ( long TR/long TE ) to minimize T1
relaxation effects.
 Long TR/TE = High Signal = Brighter Image
 Short TR/TE = Low Signal = Darker Image
 Compartments filled with water appear bright and tissues with high fat
content appear dark.
 Good for demonstrating pathology since most lesions are associated with an
increase in water content.

17. PD-weighted imaging
 used to differentiate anatomical
structures based on their proton
density;
the scanning parameters are set ( long
TR/short TE ) to minimize T1 and T2
relaxation effects
FLAIR images
Inversion recovery sequence with long
T1 to remove the effects of fluid from the
resulting images.

18. IMAGING
CT SCAN CSF Edema White
Matter
Gray
Matter
Blood Bone
MRI T1 CSF Edema Gray
Matter
White
Matter
Cartilage Fat
MRI T2 Cartilage Fat White
Matter
Gray
Matter
Edema CSF
IMAGE GRADATION

19.  Shorten T1 relaxation time
 Almost no side effects
No allergy ( as with Iodine)
Can be used in renal impairment
MR contrast (Gadolinium)

20.  Anatomy
 Congenital anomalies
 Hereditary and metabolic diseases
 Infections
 Demyelination
 Vascular event
 Tumours
 Trauma
 Dementia
 Hydrocephalus
 Cranial nerves
 Arteriograms
 Venograms
 Skull base
 Pituitary gland
Indications

21.  Diagnosing: MS; strokes; infections of the brain/spine/CNS;
tendonitis
 Visualising: Injuries; torn ligaments – especially in areas
difficult to see like the wrist, ankle or knee
 Evaluating: Masses in soft tissue; cysts; bone tumours or
disc problems.
Uses

22.  Problem solving tool in liver, pancreatic, renal and adrenal
lesions
 Primary modality in local staging of rectal ca, endometrial ca,
cervical ca, prostate ca, vaginal ca
 Non-invasive modality in evaluating pancreaticobiliary tract –
MRCP
 Scrotal and penile imaging
 Uterus and ovary imaging
Abdominal MRI

23.  No ionizing radiation & no short/long-term effects
demonstrated
 Better contrast resolution & tissue discrimination
 Many details without I.V contrast
 Contrast dye has a very low chance of side effects
 ‘Slice’ images can be taken on many planes and
thickness
 Non invasive way of diagnosing diseases and
conditions
Advantages

24.  Claustrophobia : Patients are in a very enclosed space.
 Weight and size : Limitations to how big a patient can be.
 Noise : The scanner is very noisy.
 Keeping still : Have to keep very still . So children need
sedation.
 Cost : Expensive, therefore scanning is also costly.
 Time consuming: take 15 to 45 minutes.
Disadvantages

25. Contraindications
Implanted electric and electronic devices:
1) heart pacemakers (especially older types)
2) insulin pumps.
3) implanted hearing aids.
4) neurostimulators.
Intracranial metal clips.
Metallic bodies in the eye.
Pregnancy: relative contraindication. Better to avoid in first 4
months.

27. MRCP Ca Rectum