# Quality Control in Dental Cone-Beam Computed Tomography
## 3 Results  
Unlike conventional CT, CBCT emits an open conical radiation beam to scan the object [29; 30]. The KAP meterwas chosen to evaluate the CBCT performance. The determination results of KAP are shown in Table 1. The experimental results of the image metric parameters are presented in Table 2. Objective quantitative methods were applied to evaluate CBCT images instead of subjective evaluation methods. The purpose was to achieve higher standardization and precision.  
The KAP, spatial resolution, CNRI, and uniformity index calculated by our method should satisfy the following requirements (not up to the action level) when used as performance metrics of CBCT:  
1. The KAP normalized to the FOV 16 cm\({}^{2}\) (the FOV was 4 cm \(\times\) 4 cm) should not be larger than 250 mGy\(\cdot\)cm\({}^{2}\).
2. The spatial resolution defined by the 10% point of MTF should not be lower than 1 Lp/mm.
3. CNRI should be less than 20%.
4. The uniformity index should be larger than five.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Site**} & \multirow{2}{*}{**Manufacturer**} & \multirow{2}{*}{**Model**} & \multicolumn{2}{c}{**Settings**} & \multirow{2}{*}{**Measurements/mGy\(\cdot\)cm\({}^{2}\)**} \\ \cline{5-6}  & & & & **kV** & & **mAs** & \\ \hline \multirow{2}{*}{1} & Shenyang Shenhe & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{30.89} & \multirow{2}{*}{54.9} \\  & Dental Clinic & & & & & \\ \hline \multirow{2}{*}{2} & Stomatological Hospital, & \multirow{2}{*}{Carestream} & \multirow{2}{*}{CS9300} & \multirow{2}{*}{90} & \multirow{2}{*}{56.5} & \multirow{2}{*}{105.3} \\  & Jilin University & & & & & \\ \hline \multirow{3}{*}{3} & Heilongjiang Oral Disease & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{37.07} & \multirow{2}{*}{77.4} \\  & Prevention and & & & & & \\ \cline{1-1} \cline{5-6}  & Treatment Institute & & & & & \\ \hline \multirow{2}{*}{4} & Shanghai Xinhua Hospital & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{30.89} & \multirow{2}{*}{65.5} \\ \cline{1-1} \cline{5-6}  & Shanghai Huashan Hospital & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{110} & \multirow{2}{*}{30.5} & \multirow{2}{*}{78.9} \\ \cline{1-1} \cline{5-6}  & Beijing Jinsong Dental Clinic & & & & & \\ \hline \multirow{2}{*}{7} & Nanjing Stomatological & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{36.07} & \multirow{2}{*}{75.3} \\  & Hospital & & & & & \\ \hline \multirow{2}{*}{8} & Jiangsu Provincial & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{36.12} & \multirow{2}{*}{75.5} \\  & Stomatological Hospital & & & & & \\ \hline \multirow{2}{*}{9} & Shenyang Stomatological & \multirow{2}{*}{Kavo} & \multirow{2}{*}{Kavo3 Dexam} & \multirow{2}{*}{120} & \multirow{2}{*}{30.76} & \multirow{2}{*}{54.6} \\  & Hospital & & & & & \\ \hline \multirow{2}{*}{10} & China Medical University & \multirow{2}{*}{Newtom} & \multirow{2}{*}{NewTom VG} & \multirow{2}{*}{
\begin{tabular}{} \end{tabular} } & \multirow{2}{*}{/} & \multirow{2}{*}{Not applicable} \\  & School\& Hospital & & & & \\ \cline{1-1} \cline{5-6}  & & & & & & \\ \cline{1-1} \cline{5-6}  & & & & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Determination results of KAP.  
Figure 4: Delineation of the region of interest.  
The action level refers to the limit specified in the quality control of dental CBCT; if the indicator exceeds the limit, corrective action must be taken. The experimental data showed that the image quality control methods proposed in this study were applicable to all CBCT units. The dosimetry proposed in this study was applicable to most units, except for the unit with automatic exposure control, because the new method did not use attenuation phantom. This equipment with automatic exposure control is rarely used in hospitals at present.