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Implementing RapidArc into clinical routine: A comprehensive program from machine QA to TPS validation and patient QA

Implementing RapidArc into clinical routine: A comprehensive program from machine QA to TPS validation and patient QA. Maria Sj ö lin. Department of Oncology, Division of Radiophysics, Copenhagen University hospital, 2730 Herlev. Specific tests for RA implementation Machine QA TPS QA

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Implementing RapidArc into clinical routine: A comprehensive program from machine QA to TPS validation and patient QA

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  1. Implementing RapidArc into clinical routine: A comprehensive program from machine QA to TPS validation and patient QA Maria Sjölin Department of Oncology, Division of Radiophysics, Copenhagen University hospital, 2730 Herlev

  2. Specific tests for RA implementation • Machine QA • TPS QA • Performance assessment of the RA optimization algorithm (PRO8.9) (artificial cases) • Patient-specific QA (clinical and artificial cases) • Phantom QA: GafChromic EBT film/ Delta4/Seven29+Octavius/ • Portal dosimetry Med Phys;38(9):5146-66, 2011. RapidArc Workshop 2012, Aarhus, Denmark

  3. Machine QA (I.) • Test of the delivery beyond its clinically used limits (at the machine) • A number of tests were developed to focus on angular accuracy Tests were performed with: GafChromic EBT film +solid water +EPSON scanner +VERISOFT FILMSCAN (v2.1) StarCheck + BeamAdjust +inclinometer (+MATLAB) Seven29 + Verisoft + inclinometer (+MATLAB) RapidArc Workshop 2012, Aarhus, Denmark

  4. Examples of machine QA tests • Static /Dynamic MLC Twinkle • 2 deg narrow angular sectors, 1 mm wide static/dynamic central gap → minimal gantry speed • 38 deg dose-less sectors →maximum gantry speed • Different MUs were delivered to check dose delivery during acceleration/deceleration for comparison: Increasing the amount of MU →the gantry will slow down! • The test can also be performed with constant gantry speed • Introduced errors • The dose rays were shifted 1, 2, and 3 deg →simulate a slow response • The rays were broadening by 1,2, and 3 deg RapidArc Workshop 2012, Aarhus, Denmark

  5. Reproduced correct delivery Reference image +introduced error of 3 deg clockwise delay Reference image +2 deg smoothening effect around the actual ctrlpt RapidArc Workshop 2012, Aarhus, Denmark

  6. TPS QA (II.) For RapidArc, the calculation of the dynamic source in the TPS is approximated by summing multiple static gantry, dynamic MLC fields using the AAA algorithm (Anisotropic Analytical Algorithm). RapidArc Workshop 2012, Aarhus, Denmark

  7. The accuracy of the dose calculation is challenged by: • The use of multiple small and off axis openings in relatively large collimator openings… • Leaf-pairs with nearly closed MLC tips commonly… (DLS parameter) • Highly asynchronous leaf movement… (Tongue and groove) An example of a beams-eye-view sequence for four control points, with a gantry spacing of 2 degrees. RapidArc Workshop 2012, Aarhus, Denmark

  8. Static field measurements DLS validation Small and/or off-axis effective opening in large collimator Tongue and groove RapidArc Workshop 2012, Aarhus, Denmark

  9. Examples of line profiles-3 mm leaf-gap • Ionization chamber measurements agree within 2 % with the calculated absolute dose in the center of field opening (4x4 cm) • Satisfactory agreement between dose-peaks under leaf tips • Using a high resolution (0.3 mm) fluence improves the results RapidArc Workshop 2012, Aarhus, Denmark

  10. Thanks for listening! RapidArc Workshop 2012, Aarhus, Denmark

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