Which statement correctly pairs a scallop designation with its region?

• A. A1/P1 -> medial third
• B. A2/P2 -> lateral third
• C. A3/P3 -> middle third
• D. A2/P2 -> middle third

Answer: (C)

In this labeling system, the area is divided into three equal regions along the relevant axis, and each designation combines an orientation (anterior or posterior) with a numeral that points to a specific zone. The crucial idea is that the numeral 3 corresponds to the central portion when paired with either the anterior or posterior orientation. Therefore, the combination where the third index aligns with the middle (central) region is the correct pairing. This convention helps precisely locate findings in ultrasound by using consistent zone references rather than vague terms. Other numerals point to the outer thirds, which is why those pairings don’t describe the middle third.