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

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

Rutine QC

2 ▪ www.regionmidtjylland.dk


Picket fence pf

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. ”Eye test”


Pf ex deviation in position tolerance 0 3mm

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

5 ▪ www.regionmidtjylland.dk


Pf ex deviation in intensity tolerance 300

PF: ex.Deviation in intensity, tolerance ±300


Pf ex eye test version 2

PF: ex. ”Eye test version 2”


Pf in total 30 test on each accelerator one every month

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


Dose rate vs gantry speed drgs

Dose rate vs. gantry speed, DRGS

9 ▪ www.regionmidtjylland.dk


Drgs ex typical deviation

DRGS: ex. typical deviation


Drgs ex cable issue

DRGS: ex. cable issue

11 ▪ www.regionmidtjylland.dk


Drgs in total 30 test on each accelerator one every month

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


Dose rate vs mlc speed drmlc

Dose rate vs. MLC speed, DRMLC

13 ▪ www.regionmidtjylland.dk


Drmlc ex segment 4 dr120 0 4cm s

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

14 ▪ www.regionmidtjylland.dk


Drmlc ex segment 2 dr600 2 4cm s

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


Drmlc ex segment 4 dr120 0 4cm s segment 1 dr480 1 6cm 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

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


Time consumption

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

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

Loose chain: unstable characteristic


Tight chain stable characteristic

Tight chain: Stable characteristic


Discussion

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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