What are double images in panoramic imaging?

• A. Objects in front of the focal trough
• B. Objects posterior to the center of rotation that are intercepted twice by the x-ray beam, forming a type of real image
• C. Objects inside the focal trough that are blurred
• D. Ghost images formed twice

Answer: (B)

Double images come from the way panoramic imaging uses a rotating x-ray beam around a fixed focal trough. When an object lies behind the center of rotation, the beam crosses that object more than once as it moves around the head. Each crossing projects the object onto the film, so you end up with two projections of the same object on the final image. This second projection can appear on the opposite side and may look like a duplicated structure because the geometry creates a second, real image of the object on the radiograph. Objects inside the focal trough stay in focus, while those outside can produce ghosting or other distortions, but the specific duplication described here is due to being posterior to the center of rotation and intersecting the beam twice.