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Machine-specific QC in Aarhus using EPID

Machine-specific QC in Aarhus using EPID. Mai-Britt K. Jørgensen , Lone Hoffmann, L.P. Muren, Lars H. Præstegaard, Rune Hansen, Jørgen B.B. Pedersen, Maria F. Jensen Aarhus University Hospital Department of Medical Physics. Rutine QC. Picket fence, PF. For every MLC and gab… Position:

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Machine-specific QC in Aarhus using EPID

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  1. Machine-specific QC in Aarhus using EPID Mai-Britt K. Jørgensen, Lone Hoffmann, L.P. Muren, Lars H. Præstegaard, Rune Hansen, Jørgen B.B. Pedersen, Maria F. Jensen Aarhus University Hospital Department of Medical Physics www.regionmidtjylland.dk

  2. Rutine QC 2 ▪ www.regionmidtjylland.dk

  3. Picket fence, PF For every MLC and gab… Position: Relative rotation of EPID and collimator Intensity (”width”): 3 ▪ www.regionmidtjylland.dk

  4. PF: ex. ”Eye test”

  5. PF: ex. Deviation in position,tolerance ±0.3mm 5 ▪ www.regionmidtjylland.dk

  6. PF: ex.Deviation in intensity, tolerance ±300

  7. PF: ex. ”Eye test version 2”

  8. PF: In total~30 test on each accelerator, one every month

  9. Dose rate vs. gantry speed, DRGS 9 ▪ www.regionmidtjylland.dk

  10. DRGS: ex. typical deviation

  11. DRGS: ex. cable issue 11 ▪ www.regionmidtjylland.dk

  12. DRGS: In total~30 test on each accelerator, one every month

  13. Dose rate vs. MLC speed, DRMLC 13 ▪ www.regionmidtjylland.dk

  14. DRMLC: ex. segment 4 DR120, 0.4cm/s 14 ▪ www.regionmidtjylland.dk

  15. DRMLC: ex. segment 2 DR600, 2.4cm/s

  16. DRMLC: ex. segment 4 DR120, 0.4cm/s segment 1 DR480, 1.6cm/s

  17. DRMLC: In total~30 test on each accelerator, one every month

  18. Time consumption • Measurements: ~10 min • Analysis (home-made software): ~1 min • Total: ~11 min 18 ▪ www.regionmidtjylland.dk

  19. Effect of chain adjustments on the DRGS and DRMLC tests • Mehtod • 3 DRGS and 3 DRMLC test with a loose chain • 3 DRGS and 3 DRMLC test with a thight chain • Result, comparing loose and thight chain • DRGS: Standard deviation was unchanged • DRMLC: Std 0.6 (loose) -> 0.2 (tight) 19 ▪ www.regionmidtjylland.dk

  20. Loose chain: unstable characteristic

  21. Tight chain: Stable characteristic

  22. Discussion • Deviations in PF are covered in next, next session • Deviations in DRGS and DRMLC • Chain adjustments have an effect on DRGS and DRMLC test, but it does not solve everything • Cable issues • Beam adjustments? • For more information on the calculations and tolerances: Med. Phys. 38, 1425 (2011); 22 ▪ www.regionmidtjylland.dk

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