Radiation dose reduction in direct digital panoramic radiography

(a) To measure the absorbed radiation doses at 16 anatomical sites of a Rando phantom and (b) to calculate the effective doses including and excluding the salivary gland doses in panoramic radiography using a conventional and a digital panoramic device.

Thermoluminescent dosimeters (TLD-100) were placed at 16 sites in a Rando phantom, using a conventional, Planmeca Promax and a digital, Planmeca PM2002CC Proline 2000 (Planmeca Oy, 00880 Helsinki, Finland) panoramic device for panoramic radiography. During conventional radiography the selected exposure settings were 66 kVp, 6 mA and 16s, while during digital radiography two combinations were selected 60 kVp, 4 mA, 18 s and 66 kVp, 8 mA, 18s with and without image processing function. The dosimeters were annealed in a PTW-TLDO Harshaw oven. TLD energy response was studied using RQN beam narrow series at GAEC's Secondary Standard Calibration Laboratory. The reader used was a Harshaw, 4500. Effective dose was estimated according to ICRP(60) report (E(ICRP60)). An additional estimation of the effective dose was accomplished including the doses of the salivary glands (E(SAL)). A Wilcoxon signed ranks test was used for statistical analysis.

The effective dose, according to ICRP report (E(ICRP60)) in conventional panoramic radiography was 17 microSv and E(SAL) was 26 microSv. The respective values in digital panoramic radiography were E(ICRP60)=23 microSv and E(SAL)=38 microSv; while using the lowest possible radiographic settings E(ICRP60) was 8 microSv and E(SAL) was 12 microSv.

The effective dose reduction in digital panoramic radiography can be achieved, if the lowest possible radiographic settings are used.