ONCOR Avante Garde #5863472, ONCOR Expression #7360717, ONCOR Impression #5857920, ONCOR Impression Plus #5857912 with Digital LINAC Systems Control Console Software Versions 6, 7, 9, 13

Potential safety issue with the dose monitoring system safety interlocks which could result in a 10-20% overdose of radiation therapy.

A Customer Safety Advisory Notice was sent to all affected consignees on 2/18/2020 via Adobe Mega Sign or USPS certified mail. The notice describes the interlock scenarios, provides user instructions, and warns the user of potential risks. The interlock scenarios are as follows: MONITOR 2: Monitor 2 total dose coincidence. Intent: This interlock is intended to prevent overdose when the primary dose monitory system fails to complete the treatment. TREATMENT TIME: Preset treatment time coincidence with actual treatment time. Intent: This interlock is intended to prevent overdose if preset treatment time is exceeded. MONITOR SYNC (SW): Excessive accumulated dose deviation detected between the primary and the secondary dose monitoring systems. Intent: This interlock is intended to prevent patient mistreatment due to the inaccurate monitoring of delivered dose. When one or more of the above described interlocks occur, it may be assumed that there is an error in the dose monitor system.The Consumer Safety Advisory Notice states that the Operator's Manual Instructions Update document should be added to the product's manual and all users should be informed of the issues.