Presentation on theme: "RapidArc plan verification using ArcCHECK™"— Presentation transcript:
1 RapidArc plan verification using ArcCHECK™ Dr Craig EdwardsUniversity Hospital of North StaffordshireThe Cancer Centre,Stoke-on-Trent,Staffordshire,ST4 6QG.England
2 The University Hospital of North Staffordshire (UHNS) Radiotherapy Physics;Moved to the new Cancer Centre in June 2009Cancer Centre features;Eclipse treatment planning system4 Varian iX linear acceleratorsHDR Brachytherapy UnitAn Acuity simulatorGE lightspeed CT scanner
3 IMRT and RapidArc at UHNS Dynamic IMRT 2005Commissioned on 600C & 2100C Varian linacs~ 15 patients per year (2:1 H&N:prostate)Dynamic IMRT 20104 matched 2100iX Varian linacs~ 175 patients per year (8:1 prostate:H&N)have treated uterus, cordoma, breastRapidArc 2011Attended Varian training courseMSc ProjectCommissioned patient QA systemFirst clinical patient summer 2011
5 Arc Therapy - RapidArc An advanced form of IMRT Uses 177 control pointsGantry arm rotates 358°Three forms of modulationGantry speed: 0.5 – 4.8 °/sLeaf speed: cm/sDose rate: MU/min
6 Patient QA measurements IMRT patientEvery field’s dose fluence measured and comparedGamma analysis used to evaluate (3mm/3%)Point dose measurement compared with expected (+/- 5%)Arc TherapyReplicate conventional IMRT ?
7 System Choice Several available Selection – ArcCheck ArcCheck Delta4 MatriXX / cubeOctaviusSelection – ArcCheckLightSingle cable set-upAbsolute dosePotentially 3D DVH mappinglooked right - cylindrical!!
8 Rotation QA system ArcCheck Cylindrical with diameter of 26.6 cm Water equivalent1386 diode detectorsDiodes at a depth of 2.9 cmDiodes 1 cm apartArranged helicallyCentral cavity insert
9 Performance Tests Response reproducibility Response linearity with doseDose rate dependenceConsistency of chamber response with orientationStability of calibration with time
10 Calibration Varian 2100iX linear accelerator Operating energies of 6 and 10 MVDose rate 600 MU.min-1Field size 10 x 10 cm2ArcCheck centre positioned at isocentre (SSD 86.7cm)200 MU deliveredDose at detectors6 MV – 2.47 Gy (1.32 Gy at isocentre)10 MV – 2.60 Gy (1.54 Gy at isocentre)
11 Response reproducibility MethodIrradiated central diode100 MU, 10 x 10 cm2 field5 irradiationsRecord response & compare with planning systemDetermine coefficient of variation (CV)ResultsMean reading cGyComparison with Eclipse %Standard deviation: cGyCV: %
12 Response linearity with dose MethodIrradiated central diodeVaried delivered dose from 10 to 500 MU10x10 cm2 fieldRecord response & compare with planning systemDetermine CV
13 Response linearity with dose ResultsComparison with Eclipse: max diff 0.3% MU)above 100 MU, diff -0.1%When normalised against 100 MU response;Standard deviation: cGyCV: %
14 Dose Rate Dependence Method Irradiated central diode 100 MU, 10 x 10 cm2 field100 to 600 MU.min-1Record response & compare with planning systemDetermine coefficient of variation (CV)
15 Dose Rate Dependence Results Standard deviation: 0.70 cGy CV: 0.54 % Comparison with Eclipse;Maximum difference % MU.min-1)Difference at 600MU.min %Standard deviation: cGyCV: %
16 Dependence upon irradiated angle MethodIrradiated central diode100 MU, 10 x 10 cm2 fieldArcCheck rotated to each angleRecord responseDetermine coefficient of variation (CV)ResultsMean reading cGyStandard deviation: cGyCV: %
17 Stability of calibration MethodIrradiated central diode100 MU, 10 x 10 cm2 fieldResponse recorded every 20 mins for 2 hoursDetermine coefficient of variation (CV)ResultsMean reading cGyStandard deviation: cGyCV: %
18 Clinical tests Verification of IMRT treatment Verification of RapidArc treatment
19 Verification of IMRT Method ArcCheck CT scanned Image used as template for verification planExport the treatment plan to ArcCheck imageExport re-calculated fluences MapCheckExpected dose fluence compared to measured for every field and the sum of all fieldsFields evaluated using gamma calculation with setting of 3mm/3%
20 Verification of IMRT Results Gamma evaluation pass rate 98.5 % Point dose evaluation measured -0.2 %
21 Verification of RapidArc MethodSame as IMRT except there is only 1 field!!
23 Conclusions The ArcCheck dosimetry system; is simple and quick to set-uphas a quick and efficient software solution to calibrate diodes in absolute dosedetectors demonstrated response characteristic which would make it a suitable dosimetry toolis an excellent solution for the verification of both IMRT and RapidArc treatment
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