We would like to start by thanking Dr Molen for his comments on our article. As with any research project, there is always room for improvement and future directions to pursue. Since Dr Molen is an expert in the field of 3-dimensional x-rays, we read his comments with great interest but were disappointed that he missed some important details in our study. For example, at the time of our study, no 10-year-old phantoms were available. Therefore, we used the adult and child phantoms available to conduct this preliminary study, with future directions in mind. Although a 5-year-old phantom is too young for orthodontic diagnostic purposes, the data can be extrapolated to give an idea of the radiation doses at ages in between. It is important to understand that these phantom heads are extremely expensive and not readily available in all shapes and sizes.
Since this study, we have acquired a 10-year-old phantom and have already performed studies on the 5-year and 10-year phantoms, measuring radiation doses from bite-wing x-rays, digital panoramic x-rays, and digital lateral cephalograms; we hope to publish these results soon. Furthermore, we are currently conducting studies on the 10-year-old phantom, measuring radiation doses from cone-beam computed tomography (CBCT) images and hope to provide a standardized comparison of radiation doses from 2-dimensional and 3-dimensional x-ray sources under controlled parameters.
Another key point is that the aim of our study was to compare children’s organ doses with adults’ doses when the same imaging parameters are used. The key finding of the study—that children’s organs receive a higher equivalent dose than do adults’ organs under identical imaging conditions—was observed for all combinations of imaging parameters used in our study. This is likely to be true for other combinations of imaging parameters, including the 4.8-second scan time. Although absolute organ doses are expected to be smaller in the 4.8-second scan than in the 8.9-second scan for both children and adults, the point of the study was not to compare absolute organ doses. Furthermore, the 4.8-second exposure time is available for the 0.4-mm voxel, but not for the 0.2-mm voxel scan on the i-CAT unit we used; we chose the 8.9-second scan for consistency.
On his Web site, Dr Molen acknowledged that with the introduction of CBCT machines and the multitude of third-party DICOM readers, orthodontists today have been left to sort through volumes of information on their own. In our conclusions, it was our intention to provide an evidence-based “recommendation” on the use of CBCT images and to clarify the clinical significance of the overall findings of our study, something that can easily be lost amid all the numbers provided. We acknowledge that this study has inherent flaws but note that flawless research projects exist only on paper. Future directions certainly include the areas mentioned by Dr Molen’s group and beyond. The necessity for standardized guidelines for the use of CBCT is constantly understated. We hope that our articles, along with others in the field, will help to enlighten doctors about this valuable tool, provide guidelines for CBCT use, and eliminate surprise reactions to comments such as CBCT “should not be used for routine diagnosis.”