The Modified Towne’s View (AP Axial for Zygomatic Arches) is a specialized cranial projection designed to demonstrate both zygomatic arches simultaneously in symmetry.
It serves as the primary non-invasive alternative to the Submentovertex (SMV / “Jug-Handle”) view, especially in trauma patients with cervical spine precautions or severe neck stiffness who cannot hyperextend their neck.
Modified Towne AP Axial Radiograph. Source: mr.suphachai praserdumrongchai / Getty Images
Detailed Indications:
Contraindications & Limitations:
Because the zygomatic arches are thin and superficial, exposure factors are reduced compared to a standard skull base Towne view to prevent burning out the delicate cortical bone.
| Parameter | Recommended Specification | Radiographic Rationale |
|---|---|---|
| Patient Posture | Supine (Trauma standard) or Erect | Erect is comfortable; supine is ideal for trauma with immobilizers |
| Image Receptor (IR) | 24×30 cm (10×12 inches), Landscape/Crosswise | Captures full bilateral lateral spread of the arches |
| SID | 100 to 115 cm (40 to 44 inches) | Standard distance to reduce geometric unsharpness |
| Grid Ratio | 8:1 to 12:1 focused grid | Essential to absorb scatter from the calvarium |
| Tube Potential (kVp) | 70−75 kVp (Reduced from standard Skull Towne) | Prevents burnout of the delicate zygomatic arches |
| mAs Range | 15−25 mAs (Lower than standard Skull Towne) | Balances soft tissue profile and fine cortical bone margins |
| Focal Spot | Small (0.6 mm) | High spatial resolution for subtle hairline fracture lines |
| Breathing | Suspended respiration | Eliminates respiratory and motion blur |
Use 30° caudad when OML is perpendicular; increase to 37° caudad if patient can only tuck chin to IOML perpendicular.
Beam passes through the glabella/hairline level to exit through the foramen magnum and inion base.
Zero head rotation ensures bilateral petrous pyramids and internal auditory canals (IAC) project symmetrically.
Correct caudal angulation projects the dorsum sellae and posterior clinoids directly within the foramen magnum.
| Error Type | Radiographic Sign on Film | Clinical Impact | Correction |
|---|---|---|---|
| Insufficient Caudal Angle (<30∘) | Petrous pyramids and mandibular condyles superimpose over the zygomatic arches. | Obscures the arches completely. | Increase the caudal tube angle to a full 30∘ (or 37∘ for IOML). |
| Excessive Caudal Angle (>30∘) | Mandibular body and alveolar processes superimpose over the inferior margins of the arches. | Causes severe vertical distortion and foreshortening. | Decrease the caudal angle back to 30∘. |
| Head Rotation (MSP not 90°) | One zygomatic arch is projected wider; the opposite arch superimposes over the lateral skull wall. | Mimics unilateral arch displacement or depression. | Realign the Mid-Sagittal Plane (MSP) perpendicular to the IR. |
| Head Tilt (IPL not parallel) | Bilateral zygomatic arches lie at unequal vertical levels. | Causes structural asymmetry. | Realign the IPL parallel to the plane of the IR. |
Projected sharply within the shadow of the foramen magnum without superimposition.
Petrous pyramids are visualized symmetrically across the transverse axis, verifying zero rotation.
Entire squamous portion of the occipital bone is spread out clearly without foreshortening.
Zygomatic arches project laterally to the cranial margins, evaluated for depression fractures.