Machine specific qc in aarhus using epid
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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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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


Rutine QC

2 ▪ www.regionmidtjylland.dk


Picket fence, PF

For every MLC and gab…

Position:

Relative rotation of EPID and collimator

Intensity (”width”):

3 ▪ www.regionmidtjylland.dk


PF: ex. ”Eye test”


PF: ex. Deviation in position,tolerance ±0.3mm

5 ▪ www.regionmidtjylland.dk


PF: ex.Deviation in intensity, tolerance ±300


PF: ex. ”Eye test version 2”


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


Dose rate vs. gantry speed, DRGS

9 ▪ www.regionmidtjylland.dk


DRGS: ex. typical deviation


DRGS: ex. cable issue

11 ▪ www.regionmidtjylland.dk


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


Dose rate vs. MLC speed, DRMLC

13 ▪ www.regionmidtjylland.dk


DRMLC: ex. segment 4 DR120, 0.4cm/s

14 ▪ www.regionmidtjylland.dk


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


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


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


Time consumption

  • Measurements:~10 min

  • Analysis (home-made software):~1 min

  • Total:~11 min

18 ▪ www.regionmidtjylland.dk


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


Loose chain: unstable characteristic


Tight chain: Stable characteristic


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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