Abstract:
:Delivery of pencil beam scanning (PBS) requires the on-line measurement of several beam parameters. If the measurement is outside of specified tolerances and a binary threshold algorithm is used, the beam will be paused. Given instrumentation and statistical noise such a system can lead to many pauses which could increase the treatment time. Statistical quality control methods are typically used on manufacturing lines to monitor a process and give early detection of a gradual problem and stop the process if a deviation is statistically significant. These methods can be used to develop a more intuitive algorithm for (PBS) delivery systems that is robust and safe and leads to decreased treatment times. The Exponentially Weighted Moving Average (EWMA) control scheme monitors deviations in beam properties which are averaged over a specified number of measurements with greater weight applied to the more recent ones. Simulation of an EWMA-style algorithm safely detected shifts in random and systematic delivery errors without false alarms. Binary and EWMA methods can be combined for improved reliability without sacrificing patient safety. In the EWMA method, the mean of a beam property can be related to systematic uncertainties and the standard deviation can be related to random uncertainties. This method allows one to have separate interlock levels for each type of uncertainty and to detect systematic trends.
journal_name
Phys Med Bioljournal_title
Physics in medicine and biologyauthors
Clasie BM,Kooy HM,Flanz JBdoi
10.1088/0031-9155/61/1/400subject
Has Abstractpub_date
2016-01-07 00:00:00pages
400-12issue
1eissn
0031-9155issn
1361-6560journal_volume
61pub_type
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