Rectangular Collimation — NDEB AFK MCQ

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ModerateRadiology & ImagingRectangular CollimationNDEB AFK

Rectangular collimation of the X-ray beam compared to round collimation reduces patient radiation dose by approximately what percentage?

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Correct answer: C — 60%

Rectangular collimation reduces the irradiated tissue volume by limiting the X-ray beam to approximately the size of the image receptor (size 2 film/sensor: approximately 30 × 40 mm). This reduces patient exposure by approximately 60% compared to a round 2.75-inch (70 mm) diameter collimator. Rectangular collimation is one of the most effective dose-reduction strategies and is recommended by all major dental radiology organisations.

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