Chapter 1

Chapter 1

1. Avoid "blanket rules"

   • Based on gender and race, and not consistent
   • Doesn't take into account body habitus

2. Importance of palpation

   • Bony landmarks are more reliable than soft tissue landmarks
   • Palpating to localize is more reliable than relying on vision to localize
   • Best landmarks are those adjacent to the area of interest
   • Palpating for landmarks to center ensures correct positioning regardless of body habitus or gender
   • Certain landmarks automatically adjust for the different body habitus'

3. Identifying between upside and downside anatomy

   • Upside anatomy = more blur and magnified (due to distance from IR)

4. Using the hand as a "ruler"

   • Females: Index and middle finger = 2 inches
   • Males: Slightly more than the width of the thumb = 1 inch
   • Male & Female: Width of smallest fingernail = 1 centimeter

5. On certain exams, including important anatomy is more important than centering at a specific location

   • Two points must always be used to define a positioning line

6. Body part movements = anglation of the x-ray bean

   • ::AP:: Flexion = Cephalic; Extension = Caudal
   • ::LAT:: Tilt, Abduction, Adduction = Cephalic or Caudal Angle
   • ::Any:: Rotation = Transverse Angle
   • Centering of the CR must be shifted by 1 inch for every 10° of tube angle, body part rotation, flexion, extension, tilt, abduction, or adduction
   • Repeats are warranted when rotation, tilt, flexion, etc. is more than 3*
   • When obliquing, anatomy most anterior with shift in the direction of obliquity; most posterior will shift opposite of the obliquity
   • The larger the patient, the greater the shift of anatomy from rotation, tilt, etc.

7. Beam divergence

   • In all circumstances, each edge of the collimated field will expand by at least 1 inch after exposure
   • X-ray beam divergence for a 40-inch SID is 2° per inch in any direction from the CR

8. Trauma positioning

   • CR || Anatomy > CR || IR
   • When the part cannot be placed parallel to the IR, angle the CR one-half of the angle formed between the part and the cassette or IR
   • Minimize cut-off or superimposition with an the largest SID possible
   • Recentering (usually lower) so that the cut-off anatomy is closer to the CR

9. Accurate positioning

   • Two points must always be used to define a positioning line
   • Positioning planes must be evaluated from a true end-on viewpoint (align self with patient)
   • Must view positioning lines and planes from the same vertical level that the patient or the anatomy is on
   • At least two different viewpoints, perpendicular from each other are required to assess all positioning planes

10. Good centering rules

    • Make good anatomical sense and use reliable bony landmarks
    • Compensate for larger or smaller patiens
    • Independent of the radiographer's own body size
    • Simple, and applied easily without other special equipment
    • Easy on the patient, quick to use
    • Consistently produce desired results, reducing repeats

11. Repeats warranted when:

    • Amount of off angle, off-rotation, incorrect tilt, flexion, or extension requiring repeat is usually >3 percent

12. Sizing of images in the text

    • Images in the text are smaller than the original radiographs from which they originate