VATECH EzRay Air Wall Manuel D'utilisation page 37

3. Operation
To ensure proper alignment between the imaging sensor and the X-ray beam, it is
recommended to use a PID (Position Indicating Device).
When using the PID, the exit pattern of the X-ray device should be aligned
perpendicular to the target receptor.
Once the PID is properly aligned, instruct the patient not to move.
EzRay Air Wall (VEX-S300W) User Manual 29