Chapter 9 Adapting Skull Positions: Routine and Trauma

Chapter 9 Adapting Skull Positions: Routine and Trauma

1. Reversing Positions, Changing Venus

   • Essence of trauma and mobile radiography is to "work around the patient"
     • This is accomplished by moving x-ray tube, moving the equipment rather than the patient
   • For head and some torso procedures, there is a limit on how much the tube can be angled before distortion is unacceptable
     • This limit is around 45 degrees

2. Estimating Degrees of Flexion/Extension

   • Visual landmarks can be used for skull positioning
     • They are the GML, OML, IOML, NML, AML
       • MML varies a great deal between patients, but it is still useful
   • Views that involve angles relative to the OML can use a simple system of estimation:
     • The AML lies about 27 degrees from OML
       • The IOML lies about 7 degrees from OML
         • The NML lies about 17 degrees from OML

3. Turning an Upright Patient's Head Lateral

   • Turning a head all the way lateral without turning the body will result in an unacceptable head tilt
     • To turn lateral have patient in a PA or AP position rotate their head as far as they can without straining.
       • Keep the head, neck, and torso in position so that none of the body or head planes become tilted, rotate entire body toward an oblique position until the head is in true lateral
   • OID gap is often unavoidable, but must be minimized as much as possible
     • Some magnification due to OID gap is unavoidable, but it is more important to keep the position parallel to the IR

4. Adapting Routine Skull Postitons

   • When a patient cannot be placed in perfect alignment with IR, it is critical to align the CR with anatomy
     • Relative tilting of the IR plate is always secondary
   • In the Waters position, extension of the head is 53 degrees not 37 degrees, measured from the normal perpendicular position of the OML
   • To get the tilt out of a lateral head position, keep the elbow off the table, and use sponges or angulation as needed o ensure the CR passes parallel to the interpupillary line

5. Taming the Trauma Skull

   • As a trauma patient lies supine without a pillow, the head naturally falls back to the surface such that the OML is extended
     • A caudal angle of 12 degrees to 15 degrees will compensate for head extension on most patients for the supine, AP skull projection
   • On cross-table lateral skull projections the tendency is to clip the back of the occipital bone at the bottom due to normal beam divergence and the edging of the IR
     • Placing the IR plate below the gurney ensures inclusions of the posterior occipital bone, at the expense of some magnification

6. Infant Skull

   • On average, for an infant, reduce the CR angle for all angled frontal skull positions by about one-third from that used for an adult
   • On all pediatric procedures, remember the importance of proper, tight collimations, safe and secure immobilization, and gonadal shielding