Dose Reduction Using the dexshield™ Rectangular Collimator in Dental Radiography

Background: Rectangular collimation has been recommended by both the ADA and the NCRP to significantly reduce patient exposure to ionizing radiation. Various types of rectangular collimation devices have been devised, but the dose reduction to various organs of the head and neck and overall total dose reduction has not been evaluated. Objective: To provide dosimetric data on four bitewing X-ray exposures to head and neck organs of a female CIRS anthropomorphic phantom using round and rectangular (DEXshield™) collimation for digital imaging. Materials and methods: Dose measurements were obtained using Optically Stimulated Luminescent (OSL) dosimeters placed in premanufactured slots of an anthropomorphic female CIRS phantom. The phantom had removable cutouts for bilateral placement of a digital sensor at the bitewing level. Four bitewing radiographs were acquired using a Gendex 765 X-ray machine at three settings using round and rectangular (DEXshield™) collimation. All exposures were repeated 15 times for each of the four bitewing exposures. The organ fractions irradiated were determined from ICRP-89 reference phantoms according to age. kVp factors and ICRP-103 tissue weighting factors were also applied. Results: Overall, an average of between 28-47.5% dose reductions when using the shield. The highest reductions for all exposures were for the eyes, cranium and brain. The 0.08 second exposure yielded the highest dose reduction and the 0.80 second exposure the least reduction. Conclusion: Our data indicated that the DEXshield™ significantly reduced unnecessary radiation dose to organs of the head and neck.