TIS                         
Chapter 3
Radiography


RADIOGRAPHY - A BRIEF OVERVIEW

Basic mechanism of radiographic image production - mechanical production of x-rays by passing high voltage through a cathode ray tube, traversing a patient and being partially absorbed. The x-ray photons that exit the patient are intercepted by an image receptor and produce a photographic image on radiographic film or other recording medium.

Primary radiation - beam of photons exiting the tube before interaction with the patientís body.

Remnant radiation - resulting beam that is able to exit from the patient and produce the photographic image on radiographic film.

Secondary Scatter Radiation - radiation produced when x-ray photons interact with body matter and photon travels in a different direction.

Attenuation - process of body matter absorbing primary radiation. The x-ray beam is attenuated differently depending on the body tissue irradiated. It is the difference in attenuation that allows for the formation of radiographic images.

Radiolucent - allows x-ray photons to pass through matter easily and appear as dark structures on a radiograph (e.g air or bowel gas).

Radiopaque - not easily traversed by x-ray photons and appear as white or chalky substance on radiographs (e.g bone).

Radiographic Quality - directly controlled by the radiographer. Selection of exposure factors controls the quantify of radiation produced to form the image.

Quality factors include: Radiation Safety - the cardinal principles of protection are time, distance and shielding. Minimize the time spent in the room when ionizing radiation is produced. Use the greatest possible distance from the source and always wear lead protection or utilize a shield between you and the radiation source.

Modalities in Radiography Special Radiographic Procedures Cardinal Rules of Any Examination
  1. Right patient/Right examination
  2. Include Proper Identification
  3. View Whole Radiograph not just area of Interest
  4. Take two views
  5. Include one joint
  6. Provide best quality possible
When viewing radiographs you may hear the terms view, projection and position.

Position refers to the patient and projection refers to the radiograph. It is very easy to interchange these two words incorrectly. When you hang a radiograph, always place the right side of the patient on your left as if they were facing you. If the exam is a unilateral extremity, hang the radiograph so that it is anatomically correct if the patient were facing you. Typically hands and fingers are hung with digits up as are toes and feet.

Features to observe in evaluating a radiograph of a bone are listed below:
  1. loss of bone density


  2. alteration of bone texture


  3. The epiphysis


  4. The zone of calcification


  5. The cortex


  6. The endosteum and the periosteum


  7. Shortening of a bone


  8. Lengthening of a bone


  9. Changes or deformities in a bone


  10. Destruction of bone


  11. Resorption of bone


  12. Erosion of bone


  13. Sclerosis of bone


  14. Calcification of bone


  15. Origin of a solitary lesion


  16. Bone maturation


  17. Fractures


  18. The soft tissues


  19. The joint
Types of Bone Diseases

The general etiological classification of diseases of bone is summarized below. In evaluating the differential diagnosis of a bone lesion, these entities should be considered: The most commonly demonstrated radiographically are:
  1. Congenital Anomalies
    1. Extra sesmoid bones

    2. Transitional vertebrae
      1. Cervical ribs
      2. Sacralization

    3. Osteogenesis Imperfecta


    4. Osteopetrosis


    5. Achondroplasia

  2. Nonneoplastic bone Changes

    1. Osteopetrosis


    2. Osteomalacia
      1. Rickets

    3. Renal Osteodystrophy


    4. Osteomyelitis


    5. Osteitis Deformans (Paget Disease)

  3. Neoplastic Bone Changes

    1. Benign

      1. Fibrous dysplasia


      2. Bone cyst


      3. Chondroma


      4. Osteoclastoma


      5. Osteoid Osteoma

    2. Malignant

      1. Chondrosarcoma


      2. Ewing Sarcoma


      3. Multiple Myeloma


      4. Osteogenic Sarcoma


  4. Fractures


  5. Joint Pathology

    1. Arthritis

      1. Gout


      2. Osteoarthritis


      3. Rheumatoid


      4. Tuberculosis


      5. Ankylosing Spondylitis

    2. Bursitis


    3. Spondylolisthesis


    4. Disc Herniation


    5. Dislocations

      1. Shoulder


      2. Hip
The path and attenuation of a beam of x-radiation. (1) The primary beam exits the x-ray tube. (2) The beam enters the patient, where the individual x-ray photons' energies are altered (attenuated) by their passage through body tissues of varying characteristics. (3) The attenuated, or remnant, beam exits the patient, carrying with it an energy representation of the body tissues traversed. (4) The x-ray photons in the remnant beam strike the phosphor crystals of the intensifying screens, causing them to emit many light photons for each incident x-ray photon. (5) The light photons photographically expose the film emulsion, resulting in an invisible latent image.


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