## 6 Evaluation of PAN Examination
### Exposure Parameters and Radiation Dose  
There are three main factors that can affect the quality of a PAN examination, namely kilovoltage setting, incorrect program selection, and incomplete acquisition [33, 34, 35].  
Errors in tube voltage or current settings are the most common errors. Generally, PAN requires tube voltages of 70-80 kV and current intensity ranges from 8 to 12 mA. Overexpression images are characterized by a blackening of PAN due to an excessively high tube voltage or current intensity, along with prolonged exposure time. Conversely, low kilovoltage or current intensity and insufficient exposure time produce underexposed images [25]. Digital panoramic dental units enable automatic modulations of X-ray beam energy, ensuring an optimal exposure control for maximizing image quality and limiting both technical errors of over/underexposure and radiation dose. Digital radiography image detectors have a higher dynamic range than conventional analogue films, which means that digital image detectors respond to X-ray beams and produce data in a wider range of X-ray exposure values [27]. In cases of overexposure, image post-processing with contrast and/ or brightness corrections can help to increase the quality of a digital image which, in an analogue variety, would have been diagnostically unacceptable. On the contrary, underexposed images often do not show significant improvement by image post-processing; therefore, in some cases, images need to be retaken [33, 34]. The effective dose for conventional analogue PAN ranges from 15 to 40 uSv depending on the machine, whereas it is around half for digital PAN when the lowest possible radiographic settings are used [11, 36]. The advantages and disadvantages of digital radiography compared to analogue radiography are summarized in Table 1.  
During the movement of the X-ray tube detection system, rotation velocity decreases when the X-ray tube is located behind a patient's head due to the presence of bone structures that absorb X-rays, such as the cervical spine and occup. This feature ensures the correct exposure of the anterior area. However, even if tube voltage, current intensity, and exposure time are perfectly selected, an insufficient coverage of structures of interest can be found when the selected program in a panoramic dental unit is incorrect [33, 34, 35].  
Finally, a partial image is obtained in cases of early release of the exposure button prior to the completion of the entire exposure cycle [25, 35]. At a time when the X-ray tube stops, a sharp image of the only part of the dental arches crossed by X-rays up to that time  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Digital Panoramic Radiography** \\ \hline _Advantages_ & _Disadvantages_ \\ \hline \hline Ease of execution & One-time high cost of implementation of the digital system \\ \hline Significant reduction in time between exposure and & \\ ready radiograph & Need for knowledge of computing technology by operators \\ \hline Image post-processing options & Lack of control over radiographs with too many \\  & retaking examinations \\ \hline Long-lasting archive of images with the easy retrieval of & Need to protect sensitive patient data \\ multiple copies & \\ \hline Teleradiology. Image transfer and reporting via internet & Possibility of tampering with images \\ \hline Wide dynamic range of X-ray exposures & \\ \hline Automatic modulation of X-ray beam energy & \\ \hline Decrease in radiation dose & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Advantages and disadvantages of digital panoramic radiography.  
is generated. The image that comes out is the same when the X-ray tube stops against the back or shoulders of larger or kyphotic patients (Figure 9).