Imaging Methods in Monitoring and Diagnosis

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Imaging Methods in Monitoring and Diagnosis
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Imaging Modalities

• X-Rays
• Nuclear Medicine
• Medical Ultrasound
• Magnetic Resonance Imaging

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X-Rays
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X-Rays

• Discovered in 1895 by Roentgen
• An ionising radiation at a higher level on EM
  spectrum
• Higher frequency or shorter wavelength

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X-Ray Production
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Plain Digital Radiography
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Computerised Tomography
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CT X-ray Beam
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Helical CT
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Computerised Tomography
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X Rays Pros and Cons

• 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

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Nuclear Medicine

• 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

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Nuclear Medicine Images
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PET-CT
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Nuc Med Pros and Cons

• 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

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Magnetic Resonance Imaging

• 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

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MRI Principle

• 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

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MRI Advantages

• Does not use ionising radiation
• Excellent at demonstrating soft tissue
• Non Invasive
• Good at cancer diagnosis

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MR Imaging
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Using Data Manipulation
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Image Manipulation
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Pros and Cons

• 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

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Medical Ultrasound

• 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

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MU Imaging
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Image Manipulation
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Doppler Imaging
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Pros and Cons

• 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

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Which do we use?

• 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?

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QUESTIONS?