Focal Trough Magnification — NDEB AFK MCQ

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ModerateRadiology & ImagingFocal Trough MagnificationNDEB AFK

The panoramic radiograph has a focal trough (image layer). Objects positioned lingual/palatal to the focal trough will appear how on the resulting image?

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Correct answer: C — Magnified (wider)

Objects positioned lingual/palatal (closer to the X-ray source) to the focal trough appear magnified (wider and blurred) on the panoramic image. Objects positioned buccal/labial (closer to the image receptor) to the focal trough appear minified (narrower and blurred). Only objects within the focal trough are sharply imaged and accurately sized. This principle is important for interpreting mandibular width, identifying superimpositions, and understanding why patient positioning is critical.

Reference: White & Pharoah – Oral Radiology: Principles and Interpretation, 8th ed., 2019