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Dosimetry of digital panoramic imaging. Part II: occupational exposure

¹ Oral Imaging Centre, Katholieke Universiteit Leuven, Belgium; ² Unit of Person Dosimetry, Radiation Protection, Katholieke Universiteit Leuven, Belgium; ³ Oral Radiology, ACTA, Amsterdam, The Netherlands

*Correspondence to: Reinhilde Jacobs, Oral Imaging Centre, School of Dentistry, Oral Pathology and Maxillofacial Surgery, Katholieke Universiteit Leuven, Kapucijnenvoer 7, 3000 Leuven, Belgium; E-mail: reinhilde.jacobs{at}med.kuleuven.ac.be

Received 17 November 2004; revised 27 January 2005; accepted 16 February 2005

Objectives: To measure occupational radiation dose during panoramic exposure from five digital panoramic X-ray units.

Methods: Exposures were made with five different digital panoramic units, of which four were equipped with a direct digital CCD (charge coupled device, "direct digital" technique), and one used storage phosphor plates ("indirect digital" technique). An anthropomorphic phantom served as the patient. An ionization chamber recorded the scattered radiation at 1 m from the phantom at five different locations around the panoramic units, both at the level of the thyroid gland and the level of the gonads, and effective organ doses were calculated. Exposure parameters were set as recommended by the manufacturers for the particular image and patient size: tube potential settings ranged between 64 kV and 74 kV, exposure times between 8.2 s and 19.0 s, tube current values between 4 mA and 7 mA.

Results: The maximum organ equivalent dose at 1 m from the panoramic unit was 0.60 µGy, the maximum organ effective dose was 0.10 µSv. Organ equivalent doses varied between 0.18 µGy and 0.30 µGy and organ effective doses between 0.01 µSv and 0.05 µSv for the different positions around the units (average for the different panoramic units). The variations in organ doses for the various machines were 0.04–0.53 µGy organ equivalent dose and 0.01–0.08 µSv organ effective dose.

Conclusions: Assuming that 500 panoramic radiographs per year are taken by a dental practitioner at 1 m distance from the panoramic unit, he or she will receive an annual additional organ effective dose between 5 µSv and 15 µSv for the thyroid gland and between 5 µSv and 40 µSv for the gonads, depending on the type of digital panoramic unit.

Keywords: dental radiography; panoramic radiography; digital imaging; radiation dose