11.06: Zone P4 – Superior Lateral Chin
YOUR ASSIGNMENT FOR THIS LESSON
✅ Step #1: Review all content below.
✅ Step #2: Image the P4 zone on your own with your ultrasound, and using the checklist provided on this page, check off all key structures to be identified in this location.
TRANSDUCER POSITION AT P4
STANDARD P4 ORIENTATION:
TRANSVERSE
Intersection of horizontal line from labial mental crease to the vertical line from the alar wing of the nose is the location of P4.
- Identify a hyperechoic linear band deeply which is the mandible or teeth (if individual hyperechoic teeth seen). Adjust your depth of penetration to position these structures at the bottom of your screen.
- The hypoechoic linear band directly above the mandible is an accessory muscle to the orbicularis oris muscle called the incisivus labii inferioris (ILI) muscle.
- The DLI muscle is a hypoechoic region just deep to the subcutaneous tissue. Beneath the DAO muscle it is the ILI muscle mentioned previously.
- Medially is a larger deep hypoechoic region, this is the lateral edge of the mentalis muscle.
EXAMPLE OF TRANSVERSE IMAGE ACQUIRED AT P4
ANATOMICAL LEGEND FOR P4 LOCATION IN TRANSVERSE
DOPPLER IMAGES ACQUIRED AT P4 OF KEY VESSELS
- The main vessel to be seen here is the inferior labial artery it is seen here continuing its course above the DLI muscle moving towards the lips more superficially.
- Angulating your probe slightly can help you visualize more of the artery simultaneously.