Pre-final topic 3: Imaging Accessories

by **Joshua** Thu Sep 17, 2009 11:45 am

RT 200 Pre-Final

Introduction to Radiologic Technology
with Science, Technology and Society

Topic 3: Imaging accessories

Accessory – accomplice, partner, additional, extra,

Introduction:

The primary purpose of diagnostic radiologic apparatus is to transfer
information from an x-ray beam to the eye/brain complex of the radiologist.
The x-ray beam (exit beam- scattered and x-ray forming rays) that
emerges from the x-ray tube is distributed uniformly in space, after
the interaction with the patient, the x-ray beam varies in intensity
according to the characteristic of tissues which passed.
Exit beam (diagnostically useful information) must be transferred to a
medium that is intelligible to the radiologist – x-ray film.
Other media: fluoroscopic image intensifier, TV monitor, laser imaging
system, detectors

Imaging accessories
1. Photographic Film (X-ray film)
  1. R.L. Maddox – A film with gelatin silver bromide emulsion – basic element of x-ray film
  2. Image Receptor – The medium that converts the x-ray beam into a visible image.
  3. The most common IR is the photographic film.
  4. The construction and characteristics of radiographic film are similar to photographic film.
    1. Spectral response (spectrum matching – screen and film emulsion light absorption characteristics are matched)
  5. Film construction (150-300um)
    1. 2 basic parts:
      1. Base – foundation of RF; made of polyester (1960)
      2. Emulsion – heart of RF; x-ray photons from Intensifying screen interact with and transfer information to the emulsion; made of gelatin
        and silver halide crystals.
        
        2 types of x-ray film base on emulsion coating:
        
        Single Emulsion
        Double Emulsion
        
        Overcoat – Protective coating of emulsion from scratches, pressure and contamination.
      3. Adhesive layer – between the base and emulsion; to maintain proper contact

Cassettes – also a part of an image receptor; its function is a protective holder of the x-ray film and the intensifying screen.
Intensifying screens – Sensitive phosphors that (purpose) converts x-rays to (visible) light (process – luminescence; type is Fluorescence – phosphor will emit light when stimulated being hit by an x-ray) to shorten exposure time and reduce patient dose. Permanently placed within the radiographic cassette.
1. 4 Layers
  1. Protective coating – protection, screen resistant
  2. Phosphor Layer - active layer, Fluorescence occur, conversion of x-ray to light energy.
  3. Reflective Layer – between the phosphor and the base; Doubles the amount of light photons reach the film.
  4. Base - Mechanical support of the active phosphor layer; Made of Polyester.