L1.2 Imaging

• Imaging


  Detects abnormal density/metabolism
• Computerised (Axial) Tomography, CAT or CT

  • Fine streams of X-rays from many angles: visualise anatomical details within "slice"
  • 3D images
  • X-rays damage DNA: mutations

  
• Magnetic Resonance Imaging (MRI)


  • Detects the density of protons (like NMR)
  • Magnetic field aligns the "spins" of protons. When they "relax", protons emit radiation: detected and measured
  • Proton density varies with the type of tissue: contrast
  • Often used to examine soft tissues
  • Can assess blood flow, detect tumours, evaluate infections, and investigate injuries to bones and joints
  • Noisy, confining, expensive ($2m)
  • Probably relatively safe: no ionising radiation
• Positron Emission Tomography (PET)


  • Images tissue function (not density)
  • Sugars (usually) are labelled with radioactive tracers then introduced into the body
  • Cells take up variable amounts of sugar, depending on metabolism. Tumour > normal
  • PET scanner detects radiation given off by the sugar
• PET


  • Lymph node metastases
  • Bone metastases in spine and pelvis
• Combined imaging


  Function and density