Jan 16, 2016
X-Rays Nuclear Medicine Medical Ultrasound Magnetic Resonance Imaging
Discovered in 1895 by Roentgen
An ionising radiation at a higher level on EM spectrum
Higher frequency or shorter wavelength
Non-Invasive Well established
technology Still evolving Flexible Readily available
and therefore relatively cheap
Ionising Radiation Not good at
imaging soft tissue on its own
Use of unsealed radioisotopes Attached to pharmaceuticals Drugs absorbed preferentially by target
organ(s) Gamma emitter so can be detected Images digitally produced from data
gathered
Can image wide variety of tissue types
Easy to target specific tissue
Can image function Utilises by-products
of other processes so cost effective
Uses ionising radiation
Could be described as invasive
Has many radiation protection issues associated with it
Better applications are expensive
Manipulation of natural magnetic field Magnetic resonance is detectable and
measurable Data detected can be digitally converted
to an image Utilises tomographic techniques of CT
Atoms have magnetic moments They spin in a magnetic field – Precession Spin frequency depends on the type of
atom or molecule – Larmor Frequency Examine the spin of hydrogen atoms Hydrogen atoms in different tissues have
different Larmor Frequencies
Does not use ionising radiation
Excellent at demonstrating soft tissue
Non Invasive
Good at cancer diagnosis
Non-Invasive Does not use
ionising radiation Excellent for soft
tissue imaging Can image function
Very Expensive Has its own health
and safety issues Has “acceptability”
issues with some patients
Utilises sound waves at ultrasonic frequency
Above 20KHz is ultrasound but usually 3 - 10 MHz for medical imaging purposes
Echoes from tissue can be detected and data interpreted digitally to produce image
Position and depth of the echoes builds up a complete picture
Non-Invasive No ionising
radiation Dynamic technique Can image soft
tissue effectively Flexible equipment Relatively cheap
Limited in what can be imaged
VERY user dependant
What information do we require? Do we wish to see function or structure? What can the patient tolerate? What would the clinician prefer? What is available for use? Is there a safer/cheaper alternative? Can potential risks be justified?