1. Medical Imaging
Imagining Modalities

2. Learning Objectives
By the end of this Lecture the student will be able to:
Understand the origin of electromagnetic radiation .
Identify the different modalities ultrasound, X-ray, CT, MR, and PET scanning.
Understand the basic principles for each imaging modality.
Differentiate between ionizing and non ionizing radiation.
Understand the general concept of using each modality in the demonstration of anatomy and physiology of body parts.

3. Imagining Modalities Radiography (X-Ray)
Fluoroscopy (guided procedures)
Diagnostic / Interventional imaging
Computed Tomography (CT)
Ultrasound (US)
Gray-Scale /Color Doppler
Magnetic Resonance Imaging (MRI)
Nuclear Medicine .

7. Conventional X-ray Imaging.
X-ray Production.
High Electrical Potential
Electrons - +
Exposure Recording Device
Radiation
Penetrate
the Sample
Electrons from cathode
filament are accelerated
towards and impact the
rotating anode.
Rapid deceleration
produces heat ( ~ 98 %)
and x-rays (~ 2%)

8. Table, and cassette holder
Overcouch X-ray Tube and Table
High Tension
Cables
X-ray Tube housing
Controls
Light Beam Diaphragm
Table, and cassette holder

9. Conventional X-ray Image of a Hand
Normal
Arthritic

10. Chest X-ray

11. (for digital screening)
Fluoroscopy
TV CAMERA
(for digital screening)
IMAGE
INTENSIFIER
X-RAY
TUBE
Allows dynamic imaging of
Blood vessels ( angiography )
and ‘interventional’ procedures
CONTROLS

12. (rare-earth doped ceramics
Computed Tomography (CT)
X-ray
tube
Rotation gives
multiple projections
Thin fan beam
of x-rays
Patient
(stationary)
Array of detectors
(rare-earth doped ceramics
with photodiodes)

13. CT Scanner

14. CT Image of Abdomen
Axial image looking up
from the feet.

15. Radioisotope Imaging Nuclear medicine(NM)
Gamma camera head

16. Gamma Camera Scan.

19. Ultrasound Imaging (US)
Ultrasound imaging is a common diagnostic medical procedure that uses high-frequency sound waves to produce images sonograms) of organs, tissues, or blood flow inside the body.
The procedure involves using a transducer, which sends a stream of high-frequency sound waves into the body and detects their echoes from internal structures. The sound waves are then converted to electric impulses, which are processed to form an image displayed on a computer monitor. It is from these images that videos and portraits are made.
Ultrasound probe

20. Ultrasound Image of 19 Week Old Foetus

21. Magnetic Resonance Imaging (MRI)
MRI imaging uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and all other internal body structures. The images can then be examined on a computer monitor, printed or copied to CD. MRI does not use ionizing radiation (x-rays).
Big superconducting
magnet (~ 1.5 tesla).
Gradient coils.
Radiofrequency coils.

22. Magnetic Resonance Imaging (MRI)
Axial Brain Images
T1-weighted
T2-weighted
Proton density
weighted

23. } } Safety Ionising Radiation Non-ionising Radiation Modality
Type
Comments }
X-ray imaging
Radioisotope scanning
Ultrasound Imaging
MRI
Biological effect , need
protection against
unnecessary doses
Ionising
Radiation }
Non-ionising
Radiation
Less harmful effects.
Better for the foetus.

24. What are they good at (or not)?
Summary
What are they good at (or not)?
Imaging Technique
Advantage
Disadvantage
X-ray
Bone-soft tissue interfaces.
High spatial resolution.
Quicker and cheap.
Poor soft tissue contrast.
Planar – except CT.
Ultrasound
Good soft tissue contrast.
Quick and cheap.
Can be 3-dimensional.
Mainly anatomical.
Only ‘reasonable’ spatial resolution.
Nuclear Medicine
Functional rather than anatomical.
PET – very sensitive metabolic tool.
Functional rather than anatomical.
Poor spatial resolution.
PET very expensive.
Long scan times.
Magnetic Resonance
Outstanding soft tissue contrast.
Ability for functional imaging and 3 (or 4) dimensional.