Zygomatic Arches
Submentovertical IR Size: 8x10 LW SID: 40"" Page #'s: 2:338,300	Positioning:   • Pt seated or supine   • Neck hyperextended to rest vertex of skull on grid	CR Entrance & Angle:   • CR _|_ to IOML 1"" posterior to outer canthi (towards floor)   • Collimation:   • Close Respiration:   • Suspend Best to Determine:   • Bilateral zygomatic arches	Eval Criteria:   • NR by symmetric arches w/o foreshortening
Tangential IR Size: 8x10 LW SID: 40"" Page #'s: 2:340,302	Positioning:   • Pt seated or supine   • Neck hyperextended to rest vertex of skull on grid   • MSP rotated 15° toward affected side   • Vertex of head tilted 15° away from the side examined	CR Entrance & Angle:   • CR _|_ to IOML through zygomatic arch ~1.5"" posterior to outer canthus   • Collimation:   • Close Respiration:   • Suspend Best to Determine:   • Used for pt's with depressed fractures or flat cheekbones   • Unilateral zygomatic arches	Eval Criteria:   • No overexposure of the arches
AP axial (Modified Towne) IR Size: 8x10 LW SID: 40"" Page #'s: 2:342,304	Positioning:   • Pt seated or supine   • Neck flexed	CR Entrance & Angle:   • CR to glabella (1"" superior to nasion) & exits the level of the mandibular angles   • If pt Can flex neck (use OML _|_) CR 30° caudad, if pt Can't (use IOML _|_) CR 37° caudad Collimation:   • Close Respiration:   • Suspend Best to Determine:   • Bilateral zygomatic arches	Anatomy to IR:   • OML & MSP _|_ to IR Eval Criteria:   • NR by symmetric arches   • Arches should be projected laterally to the mandibular ramus   • Arches not overlapped by mandible