Diagnostic Imaging

Cards (18)

  • Diagnostic imaging is tests performed to create images of the inside of the body to diagnose disease
  • radiography
    x-ray
    electromagnetic radiation
    ionising radiation - separates electrons from ions
  • how an x-ray works
    produced in an x-ray tune by the rapid deceleration of fast moving electrons
    radiographic image is created by the pattern of x-rays that reach the film
    x-rays pass or absorb depending on the density of the structure
  • x-ray colours
    black = radiolucent
    white = radiopaque
    air, fat, soft tissue, bone, metal
  • x-rays are 2D images of 3D structures
  • CT scans
    rotating x-ray machine and detector
    uses x-rays
    2D cross sectional imaging
    3D reconstruction is possible
    avoids superimposition that occurs on x-rays
  • CT scan colours
    black = hypoattenuating
    white = hyperattenuating
  • CT scans
    advantages
    • detailed anatomical reconstructions
    • increasing availability
    disadvantages
    • higher dose of radiation
    • time consuming
  • Ultrasound
    cross sectional imaging
    high frequency sound waves
    movement is in real time
  • ultrasound how it works
    transducer emits ultrasound waves
    waves are reflected back to transducer when boundary between tissues is hit
    returning echoes become electrical signals
    computer analyses data and displays it as an image
  • an ultrasound image is a series of dots
    the brightness is dependent on the echo strength
    the position is dependent on the time it takes for each echo to reach the transducer
  • ultrasound allows differentiation of fluid from soft tissue, and can assess the internal architecture of soft tissue organs
    this is less useful for a bone or gas as waves are immediately absorbed (bone) or immediately bounce back (gas)
  • ultrasound colours
    black Anechoic, e.g. fluid
    white = echogenic, e.g. fat
    hypoechoic and hyperechoic are used as comparative terms
  • ultrasound
    Advantages
    • cheap
    • non-invasive
    • can see movement in real time
    disadvantages
    • gas or bone hinders examination
    • expensive
  • MRI - magnetic resonance imaging
    use of strong magnet
    radiowaves are pulsed through patient
    detection and analysis of returned signals provide information on tissue composition
  • MRI colours
    black = hypointense
    white = hyperintense
  • MRI
    advantages
    • 2D cross sectional images can be stacked
    • different sequences can be run based on tissue type
    • no ionising radiation
    disadvantages
    • expensive
    • not widely available
    • lengthy process
  • nuclear scintigraphy
    small amounts of radioactive isotope are administered to a patient
    isotope collects in tissue of interest
    emits gamma rays, detected by a gamma camera
    safety issue, ionising radiation