Dosimetry of Newly Introduced Digital Volumetric Tomographic System

Objectives: New digital volumetric tomographic system using advanced volumetric tomosynthesis algorithm, PaX-500 ECT(Vatech Co., Ltd., Yongin, Korea), was introduced in 2007. This diagnostic system is a panoramic unit providing localized dental 3D and multiplanar imaging with 40 x 30mm field-of-view. It occupies less space and is provided at more affordable price, compared to dedicated dental 3D system. The objective of this study was to evaluate the absorbed and effective doses of PaX-500 ECT and compare them with those of panoramic radiography.

Methods: For dosimetry, thermoluminescent dosimeter (TLD) chips (Harshaw Chemical Co., USA) were placed at 31 sites throughout the layers of Female ART Head and Neck Phantom. PaX-500 ECT and Planmeca Proline EC panoramic unit (Planmeca Co., Helsinki, Finland) were used for radiation exposures. Parameters of radiographic examinations were 85kVp, 5.2mA and 8.3 seconds for 3D and multiplanar imaging at maxillary and mandibular molar area by Pax-500 ECT unit. Those were 68kVp, 6mA and 18 seconds for panoramic imaging by Planmeca panoramic unit. Average tissue absorbed, radiation weighted and effective doses were measured and calculated using 2005 ICRP tissue weighting factors.

Results: The highest radiation weighted dose was observed at salivary glands for all examinations. Effective doses in µSv were 46.6 for PaX-500 ECT at maxillary molar area, 79.6 for PaX-500 ECT at mandibular molar area and 19.7 for panoramic radiography.

Conclusion: Effective doses for PaX-500 ECT at maxillary molar and at mandibular molar area were about 2.4 and 4 times greater than that for panoramic radiography, respectively. (This study was supported by Vatech Co., Ltd..)