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Ini$alPerformanceTestResultsonanElektaMR-Linac
EricPaulson,PhDDABRRadia$onOncology,Radiology,andBiophysicsFroedtertandMedicalCollegeofWisconsin
Milwaukee,Wisconsin,UnitedStatesApril7,2017
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Disclosures• AdvancingaHealthierWisconsin(5520223/5520231)
• ElektaInstruments,AB
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WhyMRIinRadia$onOncology?• PillarsofsuccessinRT:
– Accuratedelinea$onofdiseaseextent– Op$malalignmentofthetreatment
beamtothetarget
• MRSimula$on:– Consistent,trueGTV– MoreaccurateCTV
• MR-guidedRT:– Reduceinter-,intra-frac$onalvaria$ons– Biologicallyadap$ve,dose-escalatedRT
kVCBCT MRI
Esop
hagus
PlanningCT MRI
Pancreas
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ChallengesFacingMR-guidedRT
• Decouplingthemagne$cfieldfromRTcomponents:– Minimizingmagne$cinterference
• DecouplingtheRTcomponentsfromMRIacquisi$on:– Minimizingradiofrequencyinterference
• BeamtransmissionthroughtheMRI
• InfluenceofLorentzforceonsecondaryelectrons
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MR-gRTImplementa$ons
ViewRay(WashU,UWMadison,UCLA,etc)
Rota$ngBi-Planar(CCI,Alberta)‘MRIonRails’(PMH)
Rota$ngBi-Planar(Australia)
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Elekta/PhilipsMR-Linac• Philips1.5TMRI:
– Ac$veshieldingreducesmagne$cinterference
– Faradaycageintegratedintocryostat– Splitsolenoidwithtransmissionthrough
thecyrostat– Windowsdesignedintogradient,RFcoils
• ElektaLinac:– 7MVFFFbeam(transversetoB0)– Rigidringmountedgantrywithsliprings– 160-leafMLCinS-Iorienta$on– 7mmprojectedleafwidthatisocenter– 142cmSAD– 22cmmaxfieldsizeinalongS-I
• EPIDforportalimaging,QA
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MR-LinacVaultatMCW• Modifiedexis$ng3rdfloorvault
• Floorbuiltup3’toprovidegantryclearance:– “Maze”withramp(MCW)– Ver$callig(MDA)
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Pre-AcceptanceMeasurements• Magnetrampedup:3/4/2017
• PhilipsCalibra$ons:3/5/2017–3/6/2017
• AAPMAbstractDeadline:3/9/2017
• Magnetrampeddown:3/11/2017
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Magne$cFieldvsGantryRota$on
0
2
4
6
8
10
12
14
16
180
60
120
180
240
300
Paulson,etal,AAPM2017(submiked)
• Passiveshimmedatgantry=0deg:4.1HzRMS• Averageofallangles:10HzRMS(gantryposi$oncanaffectmagne$cfieldhomogeneity)
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Magne$cFieldvsGantryRota$on(+Shimming)
0
2
4
6
8
10
12
14
16
180
60
120
180
240
300
Paulson,etal,AAPM2017(submiked)
• Averageofallangles:4.8HzRMS• Conclusion:Performshimmingateachgantryanglepriortobeam-on
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GradientLinearityover50cmFOV
Paulson,etal,AAPM2017(submiked)
• Es$matedwithin1mmat20cmradiusfromisocenter
Axial Sagikal Coronal
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With/WithoutRadia$onRadia$onOff Radia$onOn Difference
Paulson,etal,AAPM2017(submiked)
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ACRMRIPhantomQA
Paulson,etal,AAPM2017(submiked)
• MeetsrequiredtolerancesforACRAccredita$onusingprotocolfromdiagnos$c1.5TPhilipsIngenia
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Mo$onEs$ma$onAccuracy
Paulson,etal,AAPM2017(submiked)
• Matchedprogrammedpeak-to-peakdisplacement,trajectory,andfrequency
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On-BoardEPIDImageQuality
Paulson,etal,AAPM2017(submiked)
• AllrequiredfeaturesonLasVegasphantomwerevisible
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BeamProfiles
Paulson,etal,AAPM2017(submiked)
Magne$cFieldOn Magne$cFieldOff
• Symmetrywithin0.3%(withoutmagne$cfield)
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End-To-EndTest(1/2)CTSim
MIM
Monaco
Mosaiq
TSM
Integrity
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End-To-EndTest(2/2)
...\2017031... ...\MRLINA...
Date: 16/03/2017 ArcCHECK QA of Dose Distribution Hospital Name:
QA File Parameter ArcCHECK Plan
ArcCHECK-Plan
Patient Name : MRLINAC, CIRS
Patient ID : MRLINAC06
Plan Date : 3/16/2017
SSD :
SDD :
Depth :
Energy : 0
Angle :
Relative ComparisonDifference (%)
Distance (mm)
Threshold (%)
Meas Uncertainty : Yes
CAX Offset X=1 Y=-1
Summary (Gamma Analysis)Total Points
Passed
Failed
% Passed
*DTA/Gamma is using 2D Mode
: 3.0
: 3.0
: 5
: 272
: 261
: 11
: 96
Dose Values in cGyDose Values in cGyCAX Norm Sel Max
ArcCHECK 85.35 10.93 85.35
Plan 21.79 125.01 15.01 126.49
ArcCHECK -39.66 -4.08 -41.14
-Plan
% Diff -31.73 -3.27 -32.91
DTA(mm) NA 0.00 NA
0,-0.5Coords(y,x) cm
0,0 1,-21.5
Notes
Reviewed By :
Set1 Set2
X(mm)300250200150100500-50-100-150-200-250-300
%
100
80
60
40
20
0
CTSim
MIM
Monaco
Mosaiq
TSM
Integrity
96%
• ArcCheckresponseaffectedbyconcurrentimagingwhilemeasuring
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Summary• MR-gRTextendstheadvantagesofMRIintotheRTtreatmentroom,facilita$ng
highprecision,biologically-adap$ve,dose-escalatedradiotherapy
• TheElektaMR-Linacisoneofseveralimplementa$onspioneeringMR-gRT,eachuniquelyaddressingthedesignchallengesofintegra$ngMRIandRTdevices
• Basedonpre-acceptancemeasurements:– MRimagequalityandgeometricaccuracydoesnotappeartohavebeencompromised
byintegra$onofalinac– Dosimetryeffectsinthepresenceofamagne$cfieldareasexpected,andcanbe
calculatedandmanagedintreatmentplanning
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Acknowledgements
• NikolaiMickevicius• X.AllenLi,PhD• ErgunAhunbay,PhD• XingfengChen,PhD• SladeKlawikowski,PhD• RayThomas(Elekta)• ScokKotlarz(Philips)