Open ended lined cones reduce:

 # Open ended lined cones reduce:

A. Intensity of scattered radiation

B. Intensity of primary radiation

C. Level of scattered radiation

D. All of the above

The correct answer is C. Level of scattered radiation.

The position-indicating device (PID), or cone, appears as an extension of the x-ray tubehead and is used to direct the x-ray beam. Three basic types of PIDs are currently used: (1) conical, (2) rectangular, and (3) round.

The conical PID appears as a closed, pointed plastic cone. When x-rays exit from the pointed cone, they penetrate the plastic and produce scatter radiation. To eliminate cone-produced scatter radiation, the conical PID is no longer used in dentistry. Open-ended, lead-lined rectangular or round PIDs limit the occurrence of scatter radiation.

Both rectangular and round PIDs are typically available in two lengths: short (8-inch) long (16-inch). The long PID is preferred because less divergence of the x-ray beam occurs.

Of the three types of PID, the rectangular type is most effective in reducing patient exposure.

Reference: Dental Radiography Principles and Technique, Fourth Edition, Iannucci and Howerton Page NO 48

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