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(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To compare the absolute MLC leaf position tests of SNC Machine™ Hancock and AutoCAL™.
Methods: The procedure for SNC Machine™ Version 1.4.5 Hancock and AutoCAL™ v2.4 tests were performed as outlined by the vendor on an Elekta Synergy with MLCi2 MLCs. The SNC Machine™ Hancock test is comprised of three 1 cm pickets with 10.5 cm between the center of each picket while the AutoCAL™ is a picket fence test with six 3.5 cm abutting pickets that cover 23.5 cm and AutoCAL analyzes the five abutments. Initially these tests were performed with two MLC leaves out of calibration by 1.5 mm. Those leaves were then corrected and the SNC Machine™ Hancock and AutoCAL™ tests were performed again.
Results: Between the first tests, which had MLC errors, and the second tests, SNC Machine™ detected the MLC errors while AutoCAL™ did not. SNC Machine™ Hancock test gives absolute leaf position for each MLC in each of the three pickets while AutoCAL™ gives the distance between the measured position and the expected position of the peak or trough for each MLC in the picket fence pattern. Because of this, the root mean square (RMS) of the positional differences was compared. The mean RMS for each test was calculated to be 0.33 mm and 0.22 mm for SNC Machine™ Hancock and AutoCAL™ respectively with the MLC error and 0.31 mm and 0.23 mm respectively without the MLC error. The differences between these mean errors were determined to be statistically significant with a 95% confidence interval with P < 0.0001 for both trials.
Conclusion: It can be concluded both statically and for best clinical use that the SNC Machine™ Hancock test is a more reliable and robust test than AutoCAL™ for absolute MLC position tests.
Keywords
MLC, Quality Assurance, Linear Accelerator
Taxonomy
TH- External beam- photons: Quality Assurance - Linear accelerator
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