What are double images in panoramic imaging?

• A. Objects near the center of rotation intercepted once
• B. Objects posterior to the center of rotation intercepted twice by the x-ray beam during rotation
• C. Objects anterior to the center of rotation captured twice
• D. Artifacts due to patient movement

Answer: (B)

Double images show up in panoramic imaging because of the way the x‑ray beam and detector rotate around the patient. The system follows a center of rotation, sweeping the beam around the head. If an object sits behind that center (posterior to it), the beam passes through it on two separate occasions during the rotation—first as it comes around, then again as it continues past the opposite side. Each pass creates a separate projection of the same object, so two images of that object appear on the final panoramic image. This isn’t due to movement; it’s a geometric effect of the rotation. Objects near the center are intercepted only once, and objects in front (anterior) don’t produce this duplicate projection in the same way.