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

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 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 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 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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