Answer to Question #10936 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Dental

The following question was answered by an expert in the appropriate field:

Q

Do you have doses from digital imaging in dental radiology?

A

The radiation dose for photostimulable storage phosphor (PSP) digital images is about the same as for F-speed film. F-speed film is the fastest film on the market, meaning that it requires the least amount of radiation to produce a diagnostic image. The PSP digital system uses an imaging plate that is the same size and shape as film. After exposure, the plate is placed in a special scanner unique to the system and the digital image is produced. The imaging plates are not connected to the computer (or the scanner) by a wire. The plates are repackaged in infection-control Baggies and then are available for reuse.

The other type of digital imaging uses a CCD (charge-coupled device) or similar sensor that is typically attached to the computer, although there are some wireless systems out there. The sensor is thick and rigid and usually has an attached cord. The image appears on the computer screen in a few seconds without having the additional scanning step. It is estimated that the radiation dose from CCD digital imaging is about half of that from PSP or film. However, because of the size and inflexibility of the sensor, the retake rate is frequently high, reducing the lower radiation dose advantage.

That said, the numbers listed below are published in the 7th edition of the textbook Oral Radiology Principles and Interpretation (White, SC and Pharoah, MJ. Elsevier, St. Louis, 2014). This is probably the most widely used oral radiology book in the country. The data are from Table 3-3, page 32 of this book. All effective doses are in µSv (microsieverts).

Round collimation (the most commonly used in dental offices):
Full-mouth series, D-speed film, 388 µSv
Full-mouth series, PSP or F-speed film, 171 µSv
Full-mouth series, CCD sensor (estimated), 85 µSv

Rectangular collimation (not used very often):
Posterior bitewings, PSP or F-speed film, 5 µSv
Full-mouth series, PSP or F-speed film, 35 µSv
Full-mouth series, CCD sensor (estimated), 17 µSv

As you can see, in addition to the film speed or type of digital imaging system used, the collimation (size and shape of the x-ray beam) plays a very great role in the amount of radiation needed to produce a diagnostic image.

Sharon L. Brooks, DDS, MS
Professor Emerita
Dip., American Board of Oral and Maxillofacial Radiology

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