Skin entrance dose with and without lead apron in digital panoramic radiography for selected sensitive body regions.
OBJECTIVE
The aim of this study was to compare the dose at skin level at five significant anatomical regions for panoramic radiography devices with and without lead apron by means of a highly sensitive dosimeter.


METHODS
A female RANDO-phantom was exposed in five different digital panoramic radiography systems, and the dose at skin level was assessed tenfold for each measurement region by means of a highly sensitive solid-state-dosimeter. The five measurement regions selected were the thyroid, both female breasts, the gonads, and a central region in the back of the phantom. For each panoramic machine, the measurements were performed in two modes: with and without a commercial lead apron specifically designed for panoramic radiography. Reproducibility of the measurements was expressed by absolute differences and the coefficient of variation. Values between shielded and unshielded doses were pooled for each region and compared by means of the paired Wilcoxon tests (p ≤ 0.05).


RESULTS
Reproducibility as represented by the mean CV was 22 ± 52 % (median 2.3 %) with larger variations for small dose values. Doses at skin level ranged between 0.00 μGy at the gonads and 85.39 μGy at the unshielded thyroid (mean ± SD 15 ± 24 μGy). Except for the gonads, the dose in all the other regions was significantly lower (p < 0.001) when a lead apron was applied. Unshielded doses were between 1.02-fold (thyroid) and 112-fold (at the right breast) higher than those with lead apron shielding (mean: 14-fold ± 18-fold).


CONCLUSIONS
Although the doses were entirely very low, we observed a significant increase in dose in the radiation-sensitive female breast region when no lead apron was used. Future discussions on shielding requirements for panoramic radiography should focus on these differences in the light of the linear non-threshold (LNT) theory which is generally adopted in medical imaging.
Department of Oral Surgery (and Oral Radiology), University Medical Center of the Johannes Gutenberg-University, Augustusplatz 2, 55131, Mainz, Germany. rschulze@mail.uni-mainz.de.
Ralf Kurt Willy
RKW
Schulze
Department of Oral Surgery (and Oral Radiology), University Medical Center of the Johannes Gutenberg-University, Augustusplatz 2, 55131, Mainz, Germany.
Catrin
C
Cremers
Department of Radiation Oncology and Radiation Therapy, University Medical Center of the Johannes Gutenberg-University, Mainz, Germany.
Heiko
H
Karle
QUART GmbH, Zorneding, Germany.
Hugo
H
de Las Heras Gala
D001415:Back / Q000528:radiation effects; D001940:Breast / Q000528:radiation effects; D005260:Female; D006066:Gonads / Q000528:radiation effects; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008953:Models, Anatomic; D011829:Radiation Dosage; D011835:Radiation Protection / Q000295:instrumentation*; D011862:Radiography, Panoramic; D015203:Reproducibility of Results; D012867:Skin / Q000528:radiation effects*; D013961:Thyroid Gland / Q000528:radiation effects
Dose measurement; Lead apron; Panoramic radiography; Radiation protection; Shielding