iCAT CBCT data

Assessment of phantom dosimetry and image quality of i-CAT FLX cone-beam computed tomography CBCT

Results Child phantom doses were on average 36% greater than adult phantom doses. QuickScan+ protocols resulted in significantly lower doses than standard protocols.

Conclusions QuickScan+ effective doses are comparable with conventional panoramic examinations. Significant dose reductions are accompanied by significant reductions in image quality. However, this trade-off might be acceptable for certain diagnostic tasks such as interim assessment of treatment results. One potential means of reducing patient risk from CBCT examinations is to limit the area of exposure using variable FOVs that are sized for the location of the anatomy of interest. However, voxel size is linked to FOV in many CBCT units, and smaller voxel sizes associated with smaller FOVs can actually increase the dose because of increases in exposure that are needed to maintain an adequate contrast-to-noise ratio. Another approach is to reduce exposure for diagnostic tasks that theoretically require lower contrast-to-noise ratios or lower signal modulation transfer functions.

Effective doses (μSv) for the adult phantom by exposure protocol and FOV (ANOVA P value and Tukey HSD)

icat CBCT

Effective doses (μSv) for the child phantom by exposure protocol and FOV (ANOVA P value and Tukey HSD)

icat CBCT data patient

Relevant to this issue, the results of our study demonstrate that effective doses were an average of 36% greater in the child phantom than in the adult phantom. Not only is the effective dose one third higher, but also, due to the increased radiosensitivity of tissues, the risk is an additional 2 to 5 times higher to a pediatric patient.  This is important information to consider when determining what type of diagnostic imaging might be best for a patient.We have shown that the QuickScan+ protocol provided a substantial 87% reduction in dose compared with the standard exposure protocols in both child and adult phantoms. Thus, when QuickScan+ protocols can be used, they will provide a clinically meaningful reduction in dose. The largest Quick Scan+ dose recorded in this study (18 μSv) was for the 13 × 16-cm child cephalometric scan. This dose is little more than 2 days of per capita background radiation in the United States. The full FOV QuickScan+ protocols are also less than the combined doses of representative modern digital 2-dimensional panoramic and cephalometric radiographs (14-24 and 4 μSv, respectively).SureSmile scan protocol requires a high-resolution, 0.2-mm voxel scan.  We did not conduct high-resolution imaging of the pediatric phantom; however, we found that pediatric phantom doses were on average 36% greater than adult phantom doses. Hence, the estimated high-resolution SureSmile dose for the average orthodontic patient most likely is between 148 and 198 μSv. In May 2012, OraMetrix announced that they will now accept a “14.7”-second scan instead of the high-resolution “26.9”-second scan, dropping the estimated dose for a 16 × 8-cm SureSmile scan to between 97 μSv and 132 μSv for the average patient.

Bryan Bauer, DDS, FAGD      630-665-5550                                                           

Tags: , ,