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Automating AAPM AAPM TG-142 Quality Assurance Tests Using XML and Python Scripts

L LeMerise1*, B Loughery2, (1) Wayne State University, Detroit, MI, (2) Wayne State University, Detroit, MI

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Annual output measurements required by AAPM TG-142 are predominantly performed and recorded manually over many evenings, leading to data entry errors. This work automates annual output QA by compressing four separate tests into one automated method that automatically records results.

Methods: A PTW 23333 ion chamber (PTW, Munich, Germany) was placed in 40x40 cm2 solid water and connected to a PTW UNIDOSwebline electrometer to test our TrueBeam (Varian Medical Systems, Palo Alto, CA). XML scripts were created for TrueBeam Developer Mode using the SAGE application. UNIDOSwebline’s statistics and auto-detection features record and store up to 100 measurements, delayed only by electrometer reset. The minimum time required between electrometer readings was measured, then scripted as a collimator rotation at default rotation speed. Scripts incorporated a chamber warmup and tests of monitor unit linearity, dose rate linearity, photon output factors, enhanced dynamic wedge (EDW) factors, and constancy checks for a single energy without interruption. An in-house Python application was developed to translate raw binary output from the electrometer into a readable spreadsheet. A mock QA was performed for 4 photon and 3 electron energies and timed with a stopwatch.

Results: The mock QA took 2.49 hours. Electrometer resets without lost measurements required a minimum of 2 seconds, which translates to a collimator rotation of 15° for photons and 6° for electrons. Measurements were collected and recorded automatically, removing the need for manual beam control or data entry. Compared to our annual QA process, the mock QA was two times faster and free of data entry errors.

Conclusion: method provides a two-fold efficiency increase in physics resources during annual output QA of a TrueBeam with Developer Mode. It is possible and beneficial to automate the QA process with automatic electrometer detection. Future work will seek the ideal electrometer for this method.

Download ePoster [PDF]

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