ini$al performance test results on an elekta...

Ini$alPerformanceTestResultsonanElektaMR-Linac

EricPaulson,PhDDABRRadia$onOncology,Radiology,andBiophysicsFroedtertandMedicalCollegeofWisconsin

Milwaukee,Wisconsin,UnitedStatesApril7,2017

Disclosures•  AdvancingaHealthierWisconsin(5520223/5520231)

•  ElektaInstruments,AB

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

ChallengesFacingMR-guidedRT

•  Decouplingthemagne$cfieldfromRTcomponents:–  Minimizingmagne$cinterference

•  DecouplingtheRTcomponentsfromMRIacquisi$on:–  Minimizingradiofrequencyinterference

•  BeamtransmissionthroughtheMRI

•  InfluenceofLorentzforceonsecondaryelectrons

MR-gRTImplementa$ons

ViewRay(WashU,UWMadison,UCLA,etc)

Rota$ngBi-Planar(CCI,Alberta)‘MRIonRails’(PMH)

Rota$ngBi-Planar(Australia)

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

MR-LinacVaultatMCW•  Modifiedexis$ng3rdfloorvault

•  Floorbuiltup3’toprovidegantryclearance:–  “Maze”withramp(MCW)–  Ver$callig(MDA)

Pre-AcceptanceMeasurements•  Magnetrampedup:3/4/2017

•  PhilipsCalibra$ons:3/5/2017–3/6/2017

•  AAPMAbstractDeadline:3/9/2017

•  Magnetrampeddown:3/11/2017

Magne$cFieldvsGantryRota$on

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300

Paulson,etal,AAPM2017(submiked)

•  Passiveshimmedatgantry=0deg:4.1HzRMS•  Averageofallangles:10HzRMS(gantryposi$oncanaffectmagne$cfieldhomogeneity)

Magne$cFieldvsGantryRota$on(+Shimming)

0

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180

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120

180

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•  Averageofallangles:4.8HzRMS•  Conclusion:Performshimmingateachgantryanglepriortobeam-on

GradientLinearityover50cmFOV


•  Es$matedwithin1mmat20cmradiusfromisocenter

Axial Sagikal Coronal

With/WithoutRadia$onRadia$onOff Radia$onOn Difference


ACRMRIPhantomQA


•  MeetsrequiredtolerancesforACRAccredita$onusingprotocolfromdiagnos$c1.5TPhilipsIngenia

Mo$onEs$ma$onAccuracy


•  Matchedprogrammedpeak-to-peakdisplacement,trajectory,andfrequency

On-BoardEPIDImageQuality


•  AllrequiredfeaturesonLasVegasphantomwerevisible

BeamProfiles


Magne$cFieldOn Magne$cFieldOff

•  Symmetrywithin0.3%(withoutmagne$cfield)

End-To-EndTest(1/2)CTSim

MIM

Monaco

Mosaiq

TSM

Integrity

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

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

Acknowledgements

•  NikolaiMickevicius•  X.AllenLi,PhD•  ErgunAhunbay,PhD•  XingfengChen,PhD•  SladeKlawikowski,PhD•  RayThomas(Elekta)•  ScokKotlarz(Philips)

ini$al performance test results on an elekta...

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