Increasing use of CBCT in many aspects of dental treatment has been associated with an elevated concern for the long-term risks of x-ray exposure, especially in adolescent patients. An industry response to this has been to offer lower-exposure and collimated field scanning options.
Method:
Effective doses resulting from various combinations of field size/location (FOV), number of image frames, and mAs settings were calculated for ATOM child and adult anthropomorphic phantom exposures using the Galileos Comfort Plus CBCT unit. Optical Stimulated Dosimetry was used with a previously validated protocol.1Image quality data was acquired with the Quart DVT CBCT phantom.
Result:
Table: Effective dose and image quality parameters for child and adult phantoms by exposure protocol and field of view.
Child Phantom |
||||||
HD |
OFF |
ON |
||||
mAs |
6 |
8 |
10 |
15 |
20 |
25 |
Full |
39 |
52 |
72 |
122 |
160 |
202 |
Man |
29 |
44 |
55 |
99 |
136 |
159 |
Max |
21 |
32 |
42 |
72 |
98 |
115 |
Adult Phantom |
||||||
HD |
OFF |
ON |
||||
mAs |
8 |
10 |
12 |
20 |
25 |
30 |
Full |
36 |
47 |
61 |
112 |
140 |
168 |
Man |
31 |
40 |
48 |
97 |
122 |
143 |
Max |
28 |
36 |
43 |
86 |
111 |
133 |
ON = 500 frames; OFF = 200 frames
For the same exposures, child doses averaged 32% greater than adult (p=0.0004). Full field doses were greater than mandibular followed by maxillary (p=0.0002). Dose increased with increasing mAs (p>0.0001). Increasing Contrast Noise Ratio was associated with increasing mAs (p=0.0106) and frames (p=0.0423), while Modulation Transfer Function was not (p>0.05).
Conclusion:
An average of 66% reduction in dose can be achieved when using standard exposure parameters (HD-Off) in comparison with HD exposures. CNR was correlated with increasing dose; however, the clinical implication of this requires further study.