RADIOLOGY

X rays
- high density tissues
  - absorb x rays
    - radio-opaque
      - cast a white shadow
  - like
    - bone
    - calcium rich tissues
- low density tissues
  - transmit x rays without absorption
    - radio-lucent or radio translucent
      - depending on the gray scale of absorption of different materials
        
        black shadows
        
        grey shadows
  - like soft tissues which contain
    - fibers and cells
      - examples
        
        muscles
        
        fascia, tendons , ligaments
        
        vessels
        
        nerves
      - Grey shadow
    - water or fluid ( LESS )
    - fat ( LESSER ABSORPTION )
      - total black shadow
    - air ( LEAST ABSORPTION )
      - lungs
      - Total black shadow
- Formation of Human X ray image
  - Parts present behind bone
    - gets minimal exposure to x rays
- Properties of X rays
  - Penetration
    - lower atomic weight
      - transmit x rays
    - higher atomic weight
      - absorb the x rays
  - photographic property
    - bromium salt
      - applied as an emulsion on x ray film
    - film
      - procedure is called radiography
      - photo or film is called skiagram( shadow writing) or radiogram
  - fluorescence property
    - light waves are produced when x rays strike
      - phosphorous salts
  - biological properties
    - can destroy abnormal cells
      - without destroying normal cells to a certain degree
- Radiographic views of a photo
  - anteroposterior view
    - X ray tube placed anteriorly
    - X ray film placed posteriorly
      - uses
        
        in abdomen kidneys and lumbar vertebra are more posteriorly
        
        AP view used
  - posteroanterior view
    - X ray tube placed posteriorly
    - X ray film placed anteriorly
    - uses
      - in heart is more anteriorly hence
        
        PA view is used
  - Lateral view
    - Right lateral or left lateral x ray tube
    - X ray film lateral
  - Oblique view
- Radiological appearances
  - Bones
    - white shadow
      - homogenous
        
        compact bone
        
        inner and outer tables of skull
      - irregular
        
        represent lamellae
        
        spongy bone
        
        middle table of skull
        
        cancellous bone
    - grey shadow
      - medullary cavity
  - CONTRAST RADIOGRAPHY
    - for digestive system
      - barium swallow
        
        esophagus
      - barium meal
        
        stomach
      - barium meal follow
        
        small intestine
      - barium enema
        
        large intestine
    - for salivary ducts
      - sialography
    - for extrahepatic bilary apparatus
      - cholecystography
    - for tracheobronchial tree
      - bronchography
    - for urinary system
      - descending and ascending pyelography
    - for female reproductive system
      - hysterosalpingography
    - for subarchnoid space around spinal cord
      - myelography
    - for ventricles of brain
      - ventriculography
    - for vessels
      - angiography
        
        arteriography
        
        aortography
        
        cerebral angiography
        
        carotid angiography
        
        coronary angiography
        
        pulmonary angiography
        
        renal angiography
        
        ophthalmic
        
        fluorescent angiography
        
        venography
        
        lymphangiography
        
        CRITERIA
        
        PRE PROTOCOL
        
        allergy to medicines
    - CONTRAST MEDIUM
      - criteria for selection
        
        easily available
        
        non toxic
      - types
        
        air
        
        barium sulfate
        
        sodium iodide
- fluoroscopy
- mammography
  - types
    - positron emission mammography
      - principle
        
        gamma radiation
  - types based on photo
    - screening mammogram
    - diagnostic mammogram
- ultrasound
  - principle
    - form of energy in the for of waves
      - not audible are called ultrasound waves
    - types
      - doppler ultrasonography
        
        types
        
        transcranial doppler
        
        doppler echocardiography
        
        uses
        
        non functional valves of veins
        
        varicose veins
        
        saphenofemoral junction reflux
        
        decreased blood flow
        
        blood clots
        
        deep vein thrombosis
        
        stenosis
        
        peripheral arterial disease
        
        aneurysm
      - 3D and 4D ultrasound
  - instrument
    - wave producer or ultrasound transducer
      - types
        
        surface
        
        internal
  - process
    - wave produced by transducer
      - penetrate soft tissues
    - reflected back as echoes
      - received by transducer
      - recorded
      - displayed as
        
        sonogram

NEW IMAGING TECHNIQUES
- TOMOGRAPHY
  - COMPUTED AXIAL TOMOGRAPHY
  - OPTICAL COHERENCE TOMOGRAPHY
  - CONTRAST COMPUTED TOMOGRAPHY
  - POSITRON EMISSION TOMOGRAPHY
- MAGNETIC RESONANCE IMAGING OR NUCLEAR MAGNETIC RESONANCE
  - principles
    - magnetic bars
      - internal magnetic bars
        
        atoms inside body
        
        absorb radio waves
        
        protons get excited
        
        protons are the hydrogen ions of water present in tissues of body
      - external magnets
        
        MRI machine
        
        very large magnet
        
        create a magnetic field roughly 25000 times stronger than earths magnetic field
  - Appearance
    - fat , subcutaneous tissue appears as
      - white shadows
    - bone appears as
      - dark shadows or black shadow
    - soft tissues appearance
      - vary depending upon procedure
    - based on procedure
      - T1 and T2 weighted MRI
  - advantages
    - edema or hemorrhage
      - cannot be seen with CT , can be seen with MRI
      - Investigation of choice in Multiple sclerosis
  - CONTRAST MRI
  - MAGNETIC RESONANCE ANGIOGRAPHY
  - FUNCTIONAL MAGNETIC RESONANCE IMAGING