Chapter #5

Chapter #5

1. Two points used to define a positioning line

   • In most body parts, pairs of landmarks can be identified in order to visualize true lines for rotation.

2. Positioning planes evaluated from a true end-on viewpoint

   • Rotation can only be seen from an axial viewpoint.
   • Tilt from a frontal viewpoint.
   • Flexion/extension from a lateral viewpoint.
   • Important to view patient from all angles to rule out rotation, tilt, flexion, and extension.
   • Radiographer must be willing to do whatever it takes to position themselves such that the viewpoint can be achieved.

3. Positioning planes and lines viewed from same vertical level

   • Depending on the patient position, the radiographer may be required to squat, kneel, bend over, or sit/kneel on a stool to observe at the same level of the patient or anatomy.

4. Two different viewpoints required in order to properly evaluate all positioning planes.

   • All radiographic positions require at least two viewpoints be evaluated.
   • Side-to-side, superior-to-inferior, anterior-to-posterior.
   • For every position, it will be necessary at some point to go to the head of the table.

5. Adapting Centering for Changes in Part Position

   • In torso or head positioning, for every 10° of rotation, tilt, flexion, or extension, adjust the centering of the CR by 1 inch. Shift the centering toward the upside.
   • Adjusting for patient size: From the average 22 cm torso thickness in AP, for every additional 5 cm of thickness, add 1 inch to the centering shift rule-of-thumb.
   • In most positions, downside centering landmarks cannot be clearly seen.
   • Shift the CR upside less for organs that lie more anterior.
   • The “1 inch for every 10°” rule-of-thumb applies only to “deep” anatomy, that is, anatomy in the midline or toward the downside of the body.
   • For organs close to the upside surface, centering should be shifted upside less than usual, depending on how deep the organ of interest lies, when the body is rotated.
   • Sectional anatomy plays a big role in part position, especially understanding deep, superficial anatomy

6. Value of Sectional Anatomy Training for Routine Centering

   • Important to have basic knowledge of anatomical relationships from a cross-sectional frame of reference.
   • The “1 inch for every 10°” rule-of-thumb applies only to “deep” anatomy, that is, anatomy in the midline or toward the downside of the body.
   • For organs close to the upside surface, centering should be shifted upside less than usual, depending on how deep the organ of interest lies, when the body is rotated.