SUBMENTOVERTEX (SMV) PROJECTION : ZYGOMATIC ARCHES

Monday, August 18, 2014


X-ray of ZYGOMATIC ARCHES - SUBMENTOVERTEX (SMV) PROJECTION

Pathology Demonstrated:

  • Fractures of the zygomatic arch and neoplastic or inflammation processes are shown.

Technical Factors:

submentovertex - smv
SMV - Patient Erect
  • Image receptor size - 18 x 24 cm ( 8 x 10 inches), crosswise
  • 60 to 70 kV range (soft tissue technique)
  • Small focal spot
  • Automatic Electronic Control (AEC) not recommended
  • mAs 6

Patient Position:

  • Be sure to remove all metallic or plastic objects from patients head and neck.
  • This projection maybe taken with the patient erect or supine.
  • The erect position maybe easier for the patient.

Part Position:

smv
SMV - Patient Supine
  • Raise chin, Hyperextend neck until Intra Orbital Meatal Line (IOML) is parallel to image receptor. (see note)
  • Rest head on vertex of skull
  • Align Mid-sagital Plane to midline of the grid or the table or upright Bucky surface, avoiding all tilt and / or rotation.

Central Ray:

  • Align central ray (CR) perpendicular to image receptor (IR) see notes.
  • Center Image Receptor (IR) to CR, with plane of image receptor parallel to IOML.
  • Minimum SID is 40 inches (100 cm)

Collimation:

  • Collimate to outer margins of zygoma.

Respiration:

  • Suspend respiration during exposure.

Notes:
If patient is unable to extend neck adequately, angle CR perpendicular to IOML. If equipment allows, the image receptor (IR) should be angled to maintain the CR / IR perpendicular relationship.
This projection is very uncomfortable for the patients; complete the projection as quickly as possible.

Radiographic Criteria:


Structure Shown:

  • Zygomatic arches are demonstrated laterally from each mandibular ramus.

Position:

  • Correct IOML / CR relationship, as indicated by superimposition of mandibular symphisis on frontal bone. No patient rotation, as indicated by zygomatic arches visualized symmetrically.

Collimation and CR:

  • Zygomatic arches should be centered to collimated field, which is limited to zygomatic arches.

Exposure Criteria:

  • Sufficient contrast and density to visualize zygomatic arches.
  • Sharp bony margins indicate no motion.

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