SU‐E‐T‐71: Modified Machine Uptime Calculation for a Modern LINAC

Purpose: to calculate uptime for a modern linear accelerator (LINAC). Method and Materials Current Method: LINAC uptime is not only a major factor that influences the cost of running the facility but also influences associated service contracts. LINAC uptime according to LINAC manufacturer e.g. Elekta is: Uptime = (BaseTime — Down Time)/BaseTime This is an age old formula. Maturity of latest LINACs and redundancy of available components significantly reduced downtime. Interesting point to consider is the actual improvements in quality and speed of treatment caused by many new add‐on features. Proposed Method: Delays that are generally not considered as machine downtime but influence the treatment time and costs are: • Improperly tuned dose rate causing control system resets • Artifacts in KV or MV images • Patient Positioning System movements • MLC movements that cause system resets during treatment. Corrections are proposed to the above formula as follows: Uptime = (BaseTime — DownTime — OverAllDelayTime)/BaseTime Where OverallDelaytime = Sigma Di . ‘Di’ is delay due to ith “inconvenience”, such as the one listed above. Cost of such inconveniences in one year: Yearly Operating Loss = Sigma DiL ‘L’ is the cost per minute of therapists operating the accelerator. Other issues not controlled by LINAC vendors and to be factored into the service contracts of appropriate entities: • Chillers that maintain tap water temperature • Humidity levels in the facility • Distilled water levels • Treatment room door and camera operations • Linac sequencer problems, e.g. • communication errors • software issues • hardware issues Results: The proposed method accurately represents LINAC Uptime. Conclusions: Uptime is significantly less than current calculations.