RESUMO
The hardware and software faults in the image guidance system may cause ring-shaped artifacts,which is more commonly induced by the aging of the hardware.During troubleshooting,the first step should be checking whether there are obvious faults in the basic hardware.Subsequently,OBI background image is collected to confirm the bad point status.If the bad point is not shielded,it can be compensated by updating the image processing bad point.The invoked Pixel Correction Maps are adopted compensate for the bad point and calibrate the image.If it is still unable to repair,replacing the detection board can be considered.Cone-beam CT (CBCT) image guidance system is an important approach to verify the position orientation and positioning accuracy in modem radiotherapy,which effectively guarantees for the safety and accuracy of radiotherapy.We should fully understand its law of aging,maintain the equipment on a regular basis and verify the image quality to ensure the normal operation of the equipment.