patient specific qc in aarhus
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Patient specific QC in Aarhus
Lone HoffmannUlrik 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 Planning criteria: MU < 400 for 1/2 arcs
G(3,3) vs. accelerator
Differences between accelerators
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%)
acc7
80
85
90
95
100
06-07-2009
22-01-2010
10-08-2010
26-02-2011
14-09-2011
01-04-2012
Prost1 250Tonsil1 250Prost2 500Tonsil2 500Prost1 2000Tonsil1 2000 Low/moderate modulation
High modulation
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)
90
91
92
93
94
95
96
97
98
99
100
06-07-2009
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 2
Acc 5
Acc 6
Acc 9
Acc 3
Test_RI_Prost2, 15MV, 500MU, Gamma(3,3)
90
91
92
93
94
95
96
97
98
99
100
06-07-2009
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 1
Acc 4
Acc 7
Acc 10
Acc 8
Acc QC vs. Patient spec QC
Problems with acc QC on acc 5 (spring 2011) Not seen for patient specific QC
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 100 200 300 400 500 600 700
Pixel
No
rm
Leaf 30 Leaf 30 baggrund
Acc5 Gamma(3,3)
90
91
92
93
94
95
96
97
98
99
100
06-07-2009
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
Prost2 500
Tonsil2 500
Prost1 250
Tonsil1 250
Low dose rate
DRMLC test
86
88
90
92
94
96
98
100
0 5 10 15 20 25
Different patients
G(3
,3)
Acc 4 08-04-2010Acc 6 08-09-2010Acc4 08-17-2010Acc 4 08-18-2010Acc 6 08-19-2010Acc 8 08-23-2010Acc 8 08-25-2010Acc10 09-02-2010Acc3 10-14-2010Acc 6 11-11-2010
Real patient plans Reproducibility for each acc Difference between acc – not seen with acc QC
acc3
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
127 Single arcs G(3,3)
80,0
85,0
90,0
95,0
100,0
80,0 85,0 90,0 95,0 100,0
Delta4
PD
I
Single arcs G(3,3) Unity Composite G(3,3)
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
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%
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 ratesTest of reverse gantry direction
Test of gantry position Delta4
Still of measurement of 6 test plans 4xyear each accelerator
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