Transcript Patient specific QC in Aarhus - Ra
Patient specific QC in Aarhus
Lone Hoffmann
Ulrik Vindelev Elstrøm, Mai-Britt Kyed Jørgensen
VMAT introduction
Introduced in May 2009 First patient: June the 17th, 2009 Treated approx. 800 patients Primarily pelvic cancers Prostate, cervix, bladder, anal, rectum,..
Other types: Brain, sarcomas, abdominal
Patient specific QA
Perform Delta4 verification for all patients Normalization to daily output Gamma(3,3) > 95 % Most patients: G(3,3) > 97 %
Test/learning plans
10 prostate plans (15MV)were created with: 250MU, 500MU, 750Mu, 1000MU, 2000MU In 1 or 2 arcs 10 H&N plans (6MV) were created with: 250MU, 500MU, 750Mu, 1000MU, 2000MU In 1 or 2 arcs 2 Gy/fx
G(3,3) vs. #MUs
G(3,3) decreases as a function of MUs 100 98 96 94 92 90 88 86 0 prost1arc prost2arc tonsil1arc tonsil2arc 500 1000
# MU
1500 2000
G(3,3) vs. accelerator
Differences between accelerators 100 98 96 94 92 90 88 86 0 Acc1 Acc2 Acc4 Acc5 Acc6 Acc7 Acc8 Acc9 Acc10 500 1000
Prost 1arc
1500 2000
Test plans used for QA
6 of the test plans are use for QA 4 times a year each acc.
Plans with high G(3,3) are very stable (within 2-4%) 100
acc7
Prost1 250 Tonsil1 250 Prost2 500 Tonsil2 500 Prost1 2000 Tonsil1 2000 Low/moderate modulation 95 90 High modulation 85 80 06-07 2009 22-01 2010 10-08 2010 26-02 2011 14-09 2011 01-04 2012
Test plans used for QA
Some accelerators are more stable than others Acc1 performs bad in autumn 2011 – no problems with mashine QC
Test_RI_Prost2, 15MV, 500MU, Gamma(3,3)
96 95 94 93 100 99 98 97 92 91 90 06-07 2009 Acc 2 Acc 5 Acc 6 Acc 9 Acc 3 14-10 2009 22-01 2010 02-05 2010 10-08 2010 18-11 2010 26-02 2011 06-06 2011 14-09 2011 23-12 2011 01-04 2012
Test_RI_Prost2, 15MV, 500MU, Gamma(3,3)
100 99 98 97 96 95 94 93 92 91 90 06-07 2009 Acc 1 Acc 4 Acc 7 Acc 10 Acc 8 14-10 2009 22-01 2010 02-05 2010 10-08 2010 18-11 2010 26-02 2011 06-06 2011 14-09 2011 23-12 2011 01-04 2012
Acc QC vs. Patient spec QC
Problems with acc QC on acc 5 (spring 2011) Not seen for patient specific QC Low dose rate 1.6
1.4
0.6
0.4
0.2
1.2
1 0.8
0 0 -0.2
100 200 DRMLC test 300 400
Pixel
Leaf 30 Leaf 30 baggrund 500 600 700
Acc5 Gamma(3,3)
100 99 98 97 96 95 94 93 92 91 90 06-07 2009 Prost2 500 Tonsil2 500 Prost1 250 Tonsil1 250 14-10 2009 22-01 2010 02-05 2010 10-08 2010 18-11 2010 26-02 2011 06-06 2011 14-09 2011 23-12 2011
98 96 94 92 90 88 86 0
Real patient plans
100 Reproducibility for each acc Difference between acc – not seen with acc QC Acc 4 08-04-2010 Acc 6 08-09-2010 Acc4 08-17-2010 Acc 4 08-18-2010 Acc 6 08-19-2010 Acc 8 08-23-2010 Acc 8 08-25-2010 Acc10 09-02-2010 Acc3 10-14-2010 Acc 6 11-11-2010 20 25 5 acc3 10 15 Different patients
True beam
5 patients treated at Clinac and True beam G(3,3) does not depend on Clinac/True beam?
MeanG(Clinac)=98.4% MeanG(TrueBeam)=99.0%
Portal dosimetry
Use EPID/MVD for patient specific QC Fast measurement Ideal for routine measurements
Delta4 vs. PDI
Perform Delta4 and PDI measurement consecutively at same accelerator Preliminary results, Oct-Dec 2011: 68 plans (1,2, ..6 arcs) 127 single arcs Single arcs G(3,3)D4: 1.7% higher than G(3,3)PDI 100,0 95,0 Plans G(3,3)D4: 1.0% higher than G(3,3)PDI Pass criteria: G(3,3)D4: 95% G(3,3)PDI: 94% 90,0 85,0 80,0 80,0
127 Single arcs G(3,3)
85,0 90,0
Delta4
95,0 Single arcs G(3,3) Unity Composite G(3,3) 100,0
Work in Progress
Measurement of D4 and PDI for same plan at different accelerators Analysis of data (approx 100 plans and 10 new plans pr week) Workflow today: Daily PDI; used for accept/reject Weekly D4; used for check Future: Only PDI New/additional machine QC program
Machine QC program
MV imager:
Test of ”clinical” dose rates Test of reverse gantry direction
Test of gantry position
Delta4
Still of measurement of 6 test plans 4xyear each accelerator