OnOn--Board Imaging System: Board Imaging System: · PDF fileOnOn--Board Imaging System: Board...

OnOn--Board Imaging System: Board Imaging System: Implementation and Quality Implementation and Quality p Q yp Q yAssurance ProceduresAssurance Procedures

Rabih Hammoud MSRabih Hammoud MSRabih Hammoud, MSRabih Hammoud, MS

Henry Ford Health SystemHenry Ford Health Systemy yy yDetroit Michigan Detroit Michigan

Josephine Ford Cancer CenterJosephine Ford Cancer Center--Downriver Downriver B t Mi hiB t Mi hiBrownstown MichiganBrownstown Michigan

ContributorsContributorsContributorsContributors

Sua Yoo, PhD Sua Yoo, PhD Duke University Medical Duke University Medical CCCenterCenterHarrison Guan, PhD Harrison Guan, PhD Henry Ford HospitalHenry Ford HospitalJi k Ki MSJi k Ki MS H F d H it lH F d H it lJinkoo Kim, MS Jinkoo Kim, MS Henry Ford HospitalHenry Ford HospitalNing Wen, MS Ning Wen, MS Wayne State UniversityWayne State UniversityHang Dong MSHang Dong MS Wayne State UniversityWayne State UniversityHang Dong, MS Hang Dong, MS Wayne State UniversityWayne State UniversityPhysicians, residents, therapists, and Physicians, residents, therapists, and physicists atphysicists at Henry Ford health SystemHenry Ford health Systemphysicists at physicists at Henry Ford health SystemHenry Ford health System

Presentation OutlinePresentation OutlinePresentation OutlinePresentation Outline

OnOn--Board Imaging (OBI) System as Board Imaging (OBI) System as IGRT ToolIGRT Tool

Clinical Implementation of OBIClinical Implementation of OBI

Suggested QA Procedures for OBI and Suggested QA Procedures for OBI and Cone Beam CT (CBCT)Cone Beam CT (CBCT)Cone Beam CT (CBCT)Cone Beam CT (CBCT)

Summary Summary Summary Summary

IGRT and IMRTIGRT and IMRTIGRT and IMRTIGRT and IMRT

Clinical use of IMRT requires precise localization of Clinical use of IMRT requires precise localization of both target and normal tissues at the planning and both target and normal tissues at the planning and treatment stagestreatment stagestreatment stagestreatment stages

Image Guided RT (IGRT) is targeting the tumor Image Guided RT (IGRT) is targeting the tumor sing images ith patient in t eatment positionsing images ith patient in t eatment positionusing images with patient in treatment position using images with patient in treatment position

immediately prior to or during treatment immediately prior to or during treatment

Goal of IGRT is to manage interGoal of IGRT is to manage inter-- and intraand intra-- fraction fraction motion to reduce margins and optimize treatment motion to reduce margins and optimize treatment designsdesignsdesignsdesigns

Benefit of Image guided Benefit of Image guided radiation therapy (IGRT)radiation therapy (IGRT)

Interfractional motion:Interfractional motion:–– The change in target position from oneThe change in target position from oneThe change in target position from one The change in target position from one

fraction to another ( setup error, and fraction to another ( setup error, and target motiontarget motion

Intrafractional motion:Intrafractional motion:–– The change in target position duringThe change in target position duringThe change in target position during The change in target position during

treatment ( target motion, and patient treatment ( target motion, and patient motion)motion)

IGRT StrategiesIGRT StrategiesIGRT StrategiesIGRT Strategies

OnOn--line approachline approachmaking adjustment to the treatment making adjustment to the treatment g jg jparameters or position based on data within parameters or position based on data within the current txt sessionthe current txt session

OffOff--line approachline approachIntervention is the result of accumulation of Intervention is the result of accumulation of data drawn from txt sessionsdata drawn from txt sessions

IGRT ApproachesIGRT ApproachesIGRT ApproachesIGRT Approaches

Film imaging acquired using conventional port filmsFilm imaging acquired using conventional port filmsElectronic Imaging using EPIDElectronic Imaging using EPIDVideo & surface GuidedVideo & surface GuidedVideo & surface Guided Video & surface Guided Digital Projection Imaging (Radiographic and Digital Projection Imaging (Radiographic and fluoroscopic)fluoroscopic)CT Guided ( Cone Beam CT, CTCT Guided ( Cone Beam CT, CT--on rails, MV CT)on rails, MV CT)4D (gating, tracking, breath hold)4D (gating, tracking, breath hold)Marker localization and marker Tracking (seedsMarker localization and marker Tracking (seedsMarker localization and marker Tracking (seeds, Marker localization and marker Tracking (seeds, coils, infrared, clips, electromagnetic beacons)coils, infrared, clips, electromagnetic beacons)

IGRT Tools at Henry IGRT Tools at Henry Ford Health SystemFord Health System

Picture shown a 3D video system, BrainLAB infrared Tracking, and Resonant US-sim in CT room

Identification of a suitable Identification of a suitable imaging IGRT toolimaging IGRT tool

Compromise of clinical objectives, product Compromise of clinical objectives, product availability, existing infrastructure, and manpoweravailability, existing infrastructure, and manpower

–– Clinical objectives ( dose escalation/normal tissue Clinical objectives ( dose escalation/normal tissue sparing)sparing)

–– Structures of interest ( target/surrogates)Structures of interest ( target/surrogates)–– Desired level of precisionDesired level of precisionDesired level of precisionDesired level of precision–– Method of intervention/correctionMethod of intervention/correction–– Available treatment capacityAvailable treatment capacity–– Application for all or some patientsApplication for all or some patients

f f ff f f–– Identification of individuals responsible for Identification of individuals responsible for commissioning, QA, procedurescommissioning, QA, procedures

–– Structure development for responsibility delegation with Structure development for responsibility delegation with respect to measurement, analysis, decision, and respect to measurement, analysis, decision, and o e tiono e tioncorrectioncorrection

Flowchart for Flowchart for Initiating IGRT Initiating IGRT

Purchase

Acceptance andCommissioning QA Procedures

Procedures

Clinical Evaluation

AnalysisImage acquisition

Implementation

Intervention

OnOn--Board Imager Board Imager

Downriver Center forDownriver Center forDownriver Center for Downriver Center for OncologyOncology

HFH Downriver Cancer HFH Downriver Cancer CenterCenter

Treat 60 patients/day70% IMRT~70% IMRT

2 Varian LINACs; 2100C with EPID & 21EX with OBI Integrated solution with Varis 7, Eclipse , pTPS, and LINACsPhilips single slice AcQSim large bore CTAcQSim large bore CT

Varian On Board Varian On Board ImagerImagerTM TM (OBI)(OBI)

Two robotic arms Two robotic arms consisting of consisting of kilovoltage Xraykilovoltage Xraykilovoltage Xray kilovoltage Xray source and detectorsource and detectorCan obtain plainCan obtain plainCan obtain plain Can obtain plain radiographs/ radiographs/ fluroscopic or with fluroscopic or with

t ti bt it ti bt irotation can obtain rotation can obtain cone beam CT cone beam CT images.images.images.images.

Varian OBI/CBCT System Varian OBI/CBCT System –– Downriver CenterDownriver Center

LinacConsoleConsole

4DTC

KVS

OBI/CBCT

RPMMVD KVD

OBI Workstation OBI Workstation featuresfeatures

Acquisition of KV images (radio and fluoro mode)Acquisition of KV images (radio and fluoro mode)2D/2D automatic and manual matching of reference 2D/2D automatic and manual matching of reference images to pair acquired imagesimages to pair acquired imagesimages to pair acquired imagesimages to pair acquired images2D/2D automatic and manual matching of reference 2D/2D automatic and manual matching of reference images to pair of KV/MV images with implanted images to pair of KV/MV images with implanted ma ke sma ke smarkersmarkersQualitative verification of RPM gating using Qualitative verification of RPM gating using fluoroscopyfluoroscopyCBCT Acquisition CBCT Acquisition 3D/3D automatic and manual images fusion of 3D/3D automatic and manual images fusion of CBCT to reference 3D imagesCBCT to reference 3D imagesCBCT to reference 3D imagesCBCT to reference 3D images

D FlD FlData FlowData FlowLINAC ConsoleConsole

LVI

HFH Main Campus VARIS/VISION

VARIS Treatment

Network

Servers

CT Station

Eclipse Station

Commissioning and Commissioning and Acceptance TestingAcceptance Testing

Shielding and room design Shielding and room design considerationsconsiderationsSafety and mechanical aspectsSafety and mechanical aspectsGeometric calibration of systemsGeometric calibration of systemsyyRadiographic and fluoroscopic imaging Radiographic and fluoroscopic imaging system performancesystem performancey py pCT image qualityCT image qualityDatabase and data transfer integrityDatabase and data transfer integrityDatabase and data transfer integrityDatabase and data transfer integrity

TrainingTrainingTrainingTraining

Just like any other new modality IGRT Just like any other new modality IGRT requires trainingrequires trainingrequires trainingrequires trainingTraining of therapists to use OBI Training of therapists to use OBI properly is the key to a successfulproperly is the key to a successfulproperly is the key to a successful properly is the key to a successful launch of an IGRT programlaunch of an IGRT program

OBIOBI--IGRT CapabilitiesIGRT CapabilitiesOBIOBI--IGRT CapabilitiesIGRT Capabilities

Film imaging acquired using conventional port filmsFilm imaging acquired using conventional port filmsElectronic Imaging using EPIDElectronic Imaging using EPIDVideo GuidedVideo GuidedVideo Guided Video Guided Digital Projection Imaging (Radiographic and Digital Projection Imaging (Radiographic and fluoroscopic)fluoroscopic)CT GuidedCT Guided ( ( Cone Beam CTCone Beam CT, CT, CT--on rails, MV CT)on rails, MV CT)4D4D ((gatinggating, tracking, , tracking, breath holdbreath hold))Marker localizationMarker localization and marker Tracking (seedsand marker Tracking (seedsMarker localizationMarker localization and marker Tracking (seeds, and marker Tracking (seeds, coils, infrared, clips, electromagnetic beacons)coils, infrared, clips, electromagnetic beacons)

How IGRTHow IGRTHow IGRTHow IGRT

RPM RPM –– Respiratory Gating SystemRespiratory Gating System

OBI OBI –– On Board ImagerOn Board Imager

CBCT CBCT –– Cone Beam CT Cone Beam CT

RPMRPMRPMRPM

Track patientsTrack patients’’respiratory motion with respiratory motion with external infraredexternal infrared--

fl ti k bl kfl ti k bl kreflective marker block. reflective marker block. Control intraControl intra--fraction fraction motion. motion. Co elation of inte nalCo elation of inte nalCorrelation of internal Correlation of internal motion and external motion and external motionmotionTreatment time is alsoTreatment time is alsoTreatment time is also Treatment time is also a considerationa considerationTime delayTime delay

CT time delayCT time delayCT time delayCT time delay

ITV Delineation with 4 phases gated CTITV Delineation with 4 phases gated CT

Coronal Sagittal( )Coronal S itt l Coronal Sagittal(c)Coronal Sagittal(a)

Coronal S itt l Coronal Sagittal(d)Coronal Sagittal(b)

(a) Exhale, (b) Midphase, (c) Inhale, (d) SpiralITV encompassing all the visible targets in different phases

OBIOBIOrthogonal portal imagesOrthogonal portal images –– MVMV

OBIOBIOrthogonal portal images Orthogonal portal images –– MV MV and kV image can be acquired and kV image can be acquired without gantry rotation for AP and without gantry rotation for AP and Lat online patient setup or KV/KVLat online patient setup or KV/KVLat online patient setup or KV/KV Lat online patient setup or KV/KV image pairimage pair

Couch position and Couch position and Couc pos t o a dCouc pos t o a dangle can be angle can be corrected based on corrected based on the 2Dthe 2D 2D matching2D matchingthe 2Dthe 2D--2D matching 2D matching between the portal between the portal images and DRRimages and DRR

2D/2D Image 2D/2D Image RegistrationRegistration

Patient Shifts DataPatient Shifts DataPatient Shifts DataPatient Shifts Data

49

115

0 200.250.300.350.400.45

11 Prostate Patients Data (~2000 OBI data)

A l i l

1

2 3

5 6

8

10

4 6 10

2

46

78

9

10-0.10-0.050.000.050.100.150.20

h S

hifts

(cm

)

Couch VertCouch Lng

• Average translational

shifts:

Vert: 0.07±0.65 cm 1

12 3

57

89

11

1

310

11

-0.40-0.35-0.30-0.25-0.20-0.150 0

Couc

hCouch Lat

Lng: 0.20±0.27 cm

Lat: 0.02±0.43 cm7

-0.55-0.50-0.45

0 1 2 3 4 5 6 7 8 9 10 11 12

Patients

CBCTCBCTCBCTCBCT

CBCT is capable of acquiring and CBCT is capable of acquiring and reconstructing 3D volumetric data in reconstructing 3D volumetric data in one gantry rotation with the patient in one gantry rotation with the patient in treatment position.treatment position.Verification of target position now can Verification of target position now can be achieved efficiently and accurately be achieved efficiently and accurately using CT imagesusing CT imagesusing CT images. using CT images.

CBCTCBCT T h iT h iCBCT CBCT –– TechniquesTechniques

650650--700 projections700 projections370370°°gantry rotationgantry rotationg yg y65 sec acquisition 65 sec acquisition timetime~2.5 mins total for ~2.5 mins total for acquisition and acquisition and reconstructionreconstructionBeam angle of 14Beam angle of 14°°

CBCT AcquisitionCBCT AcquisitionCBCT AcquisitionCBCT Acquisition

CBCT: 4-Degree of Freedom

3D/3D 3D/3D

MatchMatch

SIM CT

CBCT

Shift data}}

CBCT AcquisitionCBCT Acquisition--ProstateProstate

CBCT Clinical CBCT Clinical ApplicationsApplications

Spine CBCTSpine CBCTH&N CBCTH&N CBCTBreath hold Breath hold lung CBCTlung CBCTProstate CBCTProstate CBCT

Modes of CBCT AcquisitionsModes of CBCT AcquisitionsModes of CBCT AcquisitionsModes of CBCT Acquisitions

(A) Full Fan: detector (A) Full Fan: detector centered 30x40, centered 30x40, reconstructed FOV ofreconstructed FOV ofreconstructed FOV of reconstructed FOV of 24 cm in diameter, 15 24 cm in diameter, 15 cm in Ccm in C--C extentC extent

(B) Half Fan: detector (B) Half Fan: detector shifted by 14 8 cmshifted by 14 8 cmshifted by 14.8 cm, shifted by 14.8 cm, FOV=45 cm diameter, FOV=45 cm diameter, 14 cm cm c14 cm cm c--c extentc extent

Acquisition Modes and Acquisition Modes and BowBow--Tie FiltersTie FiltersBowBow Tie FiltersTie Filters

Clinical Protocol for Prostate Clinical Protocol for Prostate CancerCancerCancerCancer

Treatment PlanningTreatment Planning TreatmentTreatmentCBCTCBCT

SIM CT ScanSIM CT Scan CBCTCBCT--SIMCTSIMCT Patient SetupPatient Setup

CBCT for Patient CBCT for Patient SetupSetup

Sim-CT 1st CBCT 2nd CBCT

CBCT for Patient SetupCBCT for Patient SetupCBCT for Patient SetupCBCT for Patient Setup

Si CT 1st CBCT 2nd CBCTSim- CT 1st CBCT 2nd CBCT

What about dose What about dose from CBCTfrom CBCT

42 fractions for prostate treatment42 fractions for prostate treatment

It is essential to quantify the dose from It is essential to quantify the dose from daily CBCTdaily CBCT

Our work is to measure dose from CBCTOur work is to measure dose from CBCT

Accepted for Oral Presentation at the 49Accepted for Oral Presentation at the 49thth AAPM annual Meeting Orlando, FLAAPM annual Meeting Orlando, FL

Dose Measurement Dose Measurement for CBCTfor CBCT

Surface and body dose for Rando Surface and body dose for Rando pelvic phantom and IMRT QA phantom.pelvic phantom and IMRT QA phantom.p p Q pp p Q pInIn--vivo skin dose of prostate cancer vivo skin dose of prostate cancer patients acquiring CBCT using TLDspatients acquiring CBCT using TLDspatients acquiring CBCT using TLDspatients acquiring CBCT using TLDsData from TGData from TG--61 Protocol61 Protocol

Phantom dose Phantom dose distribution distribution –– APAP

Phantom dose Phantom dose distribution distribution –– RLRL

Phantom Dose Phantom Dose DistributionDistribution

DiscussionDiscussionDiscussion Discussion

Lt Lat dose is always Lt Lat dose is always higher than Rt Lat dose higher than Rt Lat dose

The reason is that KVS The reason is that KVS always starts from always starts from patientpatient’’s left and ends at s left and ends at patientpatient’’s lefts left

There is overlapping for There is overlapping for pp gpp glast 10 acquisition and last 10 acquisition and gantry rotation gets gantry rotation gets slower at the end but slower at the end but dose rate (i.e., pulse rate) dose rate (i.e., pulse rate) keeps the same keeps the same

DiscussionDiscussionDiscussion Discussion

Daily CBCT provides better patient Daily CBCT provides better patient setup but it increases skin and body setup but it increases skin and body p yp ydose. The dose can range from 150 dose. The dose can range from 150 ––250 cGy for skin and 130250 cGy for skin and 130–– 180 cGy 180 cGy yy yyfor body during the 42 daily fractions for body during the 42 daily fractions delivered for IMRT prostate patients.delivered for IMRT prostate patients.p pp pShould we consider the CBCT dose as Should we consider the CBCT dose as treatment dosetreatment dosetreatment dosetreatment dose

HU V ifi tiHU V ifi tiHU VerificationHU Verification

The accuracy of Hounsfield UnitsThe accuracy of Hounsfield Units (HU)(HU) in in CBCTCBCT not only affect the accuracy of not only affect the accuracy of i t hi f ti t t b t li t hi f ti t t b t limage matching for patient setup, but also image matching for patient setup, but also the accuracy of actual dose delivered to the accuracy of actual dose delivered to patient for two reasons:patient for two reasons:patient for two reasons: patient for two reasons:

(a)(a) the accuracy of delineating the structures the accuracy of delineating the structures in CBCT andin CBCT andin CBCT andin CBCT and

(b)(b) the accuracy of inhomgeneous dose the accuracy of inhomgeneous dose calculationcalculationcalculation calculation

Accepted for the 49Accepted for the 49thth AAPM Annual Meeting 2006 Orlando, FLAAPM Annual Meeting 2006 Orlando, FL

To evaluate the HU accuracy of Varian’s To evaluate the HU accuracy of Varian’s CBCT in HalfCBCT in Half--Fan mode (half bowtie) andFan mode (half bowtie) andCBCT in HalfCBCT in Half Fan mode (half bowtie) and Fan mode (half bowtie) and its effect to the accuracy of inhomogenous its effect to the accuracy of inhomogenous calculation for dosimetric verification ofcalculation for dosimetric verification ofcalculation for dosimetric verification of calculation for dosimetric verification of body sitesbody sites

PhantomsPhantoms

IMRT QA Phantom(fixed view)

IMRT QA + CTQC phantom(open view)

Sim-CT Morning QA phantom

The measured HU for each insert in the combined phantom

Demonstration of HU profiles Demonstration of HU profiles o a o o U p oo a o o U p ofor beam hardening for beam hardening

Sim CT CBCT

The HU between CBCT andThe HU between CBCT andThe HU between CBCT and The HU between CBCT and SimSim--CTCT

-- The average HU difference between The average HU difference between CBCT and SIMCBCT and SIM CT is within 20CT is within 20CBCT and SIMCBCT and SIM--CT is within 20. CT is within 20.

-- The standard deviation of HU in CBCT is The standard deviation of HU in CBCT is 2 times higher than that in Sim2 times higher than that in Sim CTCT2 times higher than that in Sim2 times higher than that in Sim--CT. CT.

-- Due to higher beam hardening effect in Due to higher beam hardening effect in CBCT the HU at phantom center is 20CBCT the HU at phantom center is 20CBCT, the HU at phantom center is 20 CBCT, the HU at phantom center is 20 higher than that at edges. higher than that at edges.

With inhomgeneity correctionWith inhomgeneity correction--g yg yPhantom StudyPhantom Study

The DVH difference is from the HU difference The DVH difference is from the HU difference alonealonealonealoneThe min dose, max dose, mean dose etc. The min dose, max dose, mean dose etc. generally agrees to ~3%generally agrees to ~3%

Dose statistics for the 9Dose statistics for the 9--beambeamDose statistics for the 9Dose statistics for the 9--beam beam IMRT planIMRT plan

For IMRT plans, the dosimetric difference with For IMRT plans, the dosimetric difference with inhomogeneity correction is also relatively smallinhomogeneity correction is also relatively smallinhomogeneity correction is also relatively smallinhomogeneity correction is also relatively small

The minimum dose, maximum dose, means dose The minimum dose, maximum dose, means dose , ,, ,and median dose for any structure agrees and median dose for any structure agrees generally within ~2generally within ~2--5%5%

Dose distribution comparison of original Sim-CT plan with a CBCT plan of 0 22cm average SSD differencewith a CBCT plan of 0.22cm average SSD difference, dose is 4.4% higher at reference point.

ProstateProstate--Margin Margin Red tio ?Red tio ?Reduction?Reduction?

11 tt P i Wi f h R id MSTRO C i i 2006P i Wi f h R id MSTRO C i i 200611stst Prize Winner of the Residents MSTRO Competition 2006Prize Winner of the Residents MSTRO Competition 2006

Favorable Risk Favorable Risk Prostate CancerProstate Cancer

78 Gy, usually prescribed to the 95% 78 Gy, usually prescribed to the 95% isodose line, to the prostate and isodose line, to the prostate and , p, pproximal 1 cm seminal vesicles using proximal 1 cm seminal vesicles using an IMRT technique.an IMRT technique.qq

PTV consists of CTV + 10 mmPTV consists of CTV + 10 mmPTV consists of CTV + 10 mm PTV consists of CTV + 10 mm expansion except 6 mm posteriorlyexpansion except 6 mm posteriorly

Zelefsky et al 1999Zelefsky et al 1999Zelefsky et al. 1999Zelefsky et al. 199950 patients, 4 CT scans each50 patients, 4 CT scans each50 patients, 4 CT scans each50 patients, 4 CT scans each

PatientsPatientsPatientsPatients

Five patients with localized prostate Five patients with localized prostate cancer were simulated with CT sim cancer were simulated with CT sim and treated to the prostate and and treated to the prostate and proximal 1 cm seminal vesicles to a proximal 1 cm seminal vesicles to a ppdose of 78 Gy.dose of 78 Gy.Educated regarding empty bladder andEducated regarding empty bladder andEducated regarding empty bladder and Educated regarding empty bladder and empty rectum.empty rectum.

ImagingImagingImagingImaging

Prior to 30 treatment fractions, a cone Prior to 30 treatment fractions, a cone beam CT was obtained followed by an beam CT was obtained followed by an yyorthogonal set of radiographs using orthogonal set of radiographs using the OBI.the OBI.Patients were shifted according to Patients were shifted according to image registration betweenimage registration betweenimage registration between image registration between radiographs and simulation DRRs. radiographs and simulation DRRs. (Patients were initially aligned to skin(Patients were initially aligned to skin(Patients were initially aligned to skin (Patients were initially aligned to skin marks)marks)

PlansPlansPlans Plans

All organs of interest were contoured All organs of interest were contoured on each cone beam CT scan.on each cone beam CT scan.Using each cone beam CT scan, a Using each cone beam CT scan, a coplanar nine field IMRT plan was coplanar nine field IMRT plan was created using the patient’s treatment created using the patient’s treatment position coordinates as isocenter.position coordinates as isocenter.Two separate plans were created one Two separate plans were created one with a 10/6 mm expansion and a 5/3 with a 10/6 mm expansion and a 5/3 mm expansionmm expansionmm expansionmm expansion

Treatment PlansTreatment PlansTreatment PlansTreatment Plans

10/6 Pl 5/3 Pl10/6 Plan 5/3 Plan

Data AnalysisData AnalysisData AnalysisData Analysis

Prostate

97.20% 97.40% 96.40%96.70% 97.40%100.00%

an

92.00%

85.00%

90.00%

95.00%

the

sim

ulat

ion

pla

70.00%

75.00%

80.00%

ered

com

pare

d to

t

10/65/3

55 00%

60.00%

65.00%

nt o

f dos

e de

lieve

50.00%

55.00%

D98 D95 Min

Perc

en


Seminal Vesicles (proximal 1cm)

110.00%

an

99.60% 100.40%98.00%

95.80%97.50%

91.10%90 00%

100.00%

the

sim

ulat

ion

pla

80.00%

90.00%

red

com

pare

d to

t

10/65/3

60.00%

70.00%

nt o

f dos

e de

lieve

r

50.00%D98 D95 Min

Perc

en

Margin ReductionMargin Reduction--ResultsResults

Our data indicates a 5/3 margin Our data indicates a 5/3 margin results in a fairly close dose results in a fairly close dose yydistribution to the 10/6 margin. distribution to the 10/6 margin. 5/3 margin reduced high dose bladder5/3 margin reduced high dose bladder5/3 margin reduced high dose bladder 5/3 margin reduced high dose bladder and rectum volumes by 30and rectum volumes by 30--50%50%

Interobserver Variability StudyInterobserver Variability Study3D/3D Image Fusion3D/3D Image Fusion

Interobserver Variability Interobserver Variability StudyStudy--ResultsResults

Mean shifts (mm) and SDs wereMean shifts (mm) and SDs were--0.40.4±±4.2 (A4.2 (A--P) P) 1.41.4±±2.4 (C2.4 (C--C)C) --0.70.7±±2.3 (R2.3 (R--L) L)

Comparing different observersComparing different observers69% (C69% (C--C), C), 83% (A83% (A--P) P) 100% (R100% (R--L)L)

Of the observations fall within 1 mm SD for ROI matching Of the observations fall within 1 mm SD for ROI matching

69% (C69% (C--C) C) 75% (A75% (A--P) P) 90% (R90% (R--L)L)

of the observations fall within 1 mm SD for OOof the observations fall within 1 mm SD for OOI matching I matching

Averages (mm) and SDs of the differences between Manual and Automatic Fusion

A-P C-C R-L

ROI 0.5±1.0 1.3±1.0 0.5±0.6

OOI 0.6±1.0 0.3±1.5 0.8±0.7

Intensity based 3D/3D FusionIntensity based 3D/3D FusionIntensity based 3D/3D FusionIntensity based 3D/3D Fusion

ROIROI–– Rectangular and irregular mask ROIRectangular and irregular mask ROI

Similarity MeasureSimilarity Measure–– MI MI –– Mutual InformationMutual Information–– NCC NCC –– Normalize Cross CorrelationNormalize Cross Correlation–– EOD EOD –– Entropy of DifferenceEntropy of Difference–– GC GC –– Gradient Correlation Gradient Correlation –– GD GD –– Gradient DifferenceGradient Difference

PIPI Pattern IntensityPattern Intensity–– PI PI –– Pattern IntensityPattern Intensity–– CR CR –– Correlation RatioCorrelation Ratio

TransformationTransformation–– Rigid Body TransformationsRigid Body Transformations

Translation (3D)Translation (3D)Translation (3D) + Table RotationTranslation (3D) + Table RotationTranslation (3D) + Rotation(3D)Translation (3D) + Rotation(3D)

–– Affine TransformationsAffine TransformationsShearing + Rotation + TranslationShearing + Rotation + TranslationScaling + Shearing + Rotation + Scaling + Shearing + Rotation + TranslationTranslationTranslationTranslation

OptimizationOptimization–– Downhill SimplexDownhill Simplex

Prostate LocalizationProstate LocalizationProstate LocalizationProstate Localization

Pelvic bone matchingPelvic bone matching–– A rectangular ROI is defined around pelvic bone ( excluding A rectangular ROI is defined around pelvic bone ( excluding

femur bones) on either sim or cbctfemur bones) on either sim or cbctfemur bones) on either sim or cbct.femur bones) on either sim or cbct.–– Similarity measure MI works very well for bone matching.Similarity measure MI works very well for bone matching.–– Typically 100 iterations is enough ( less than 5 sec on 3GHz CPU)Typically 100 iterations is enough ( less than 5 sec on 3GHz CPU)

Prostate matchingProstate matching–– An irregular mask ROI is defined around prostate and seminal An irregular mask ROI is defined around prostate and seminal

vesicles on the sim CT.vesicles on the sim CT.–– Similarity measure GC works the best from experiments.Similarity measure GC works the best from experiments.S a ty easu e GC o s t e best o e pe e tsS a ty easu e GC o s t e best o e pe e ts–– Typically 100 iterations is enough ( less than 5 sec on 3GHz CPU)Typically 100 iterations is enough ( less than 5 sec on 3GHz CPU)–– If the prostate boundary is blurry or if there is prominent rectum If the prostate boundary is blurry or if there is prominent rectum

gas pockets, registration may fail.gas pockets, registration may fail.

Accepted for Oral Presentation at AAPM 48Accepted for Oral Presentation at AAPM 48thth Annual Meeting 2006 Orlando, FLAnnual Meeting 2006 Orlando, FL

Rectaangular R

OI

Irreegular RO

I

F

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Bon

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animation

Uphill

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to start an l Simpl

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lxnimation

Fuusion Veerification: Coloor C

hannnel Vieww

IS OBI sufficient for Prostate IS OBI sufficient for Prostate localization?localization?OBI and margin reduction?OBI and margin reduction?

Accepted for Oral Presentation at AAPM 49th Annual Meeting 2006 Orlando, FLAccepted for Oral Presentation at AAPM 49th Annual Meeting 2006 Orlando, FL

Automatic pelvic bone matching Automatic pelvic bone matching p gp gvs. prostate matchingvs. prostate matching

100Bone Fz

6080

Bone FzProstate Fz

2040

0

20

0~1 1~2 2~3 3~4 4~5 5~6 6~7 7~8 8~9 9~

Bone Fz 13 66 44 33 17 2 4 8 4 5Prostate Fz 33 85 46 27 2 0 0 0 0 3

Comments on the three failuresComments on the three failuresComments on the three failuresComments on the three failures

Case 1: I forgot identifying the calcification points Case 1: I forgot identifying the calcification points by mistake. Registration was successful ( visual by mistake. Registration was successful ( visual confirmation )confirmation )confirmation )confirmation )Case 2: the patient was large and the prostate Case 2: the patient was large and the prostate boundary was not clear. Registration failed.boundary was not clear. Registration failed.Case 3 the e as a ect m gas pocket nea theCase 3 the e as a ect m gas pocket nea theCase 3: there was a rectum gas pocket near the Case 3: there was a rectum gas pocket near the target. Registration failed.target. Registration failed.

IGRT/OBI QA IGRT/OBI QA ProceduresProcedures

QA program to maintain and monitor system QA program to maintain and monitor system performance characteristics established at the performance characteristics established at the time of commissioningtime of commissioningtime of commissioningtime of commissioning

QA Program should includeQA Program should includeQA Program should includeQA Program should include1.1. Safety and functionality of the systemSafety and functionality of the system2.2. GeometryGeometry33 Image qualityImage quality3.3. Image quality Image quality 4.4. Database and data transfer integrityDatabase and data transfer integrity

OBI QAOBI QA-- ToolsTools

OBI: Daily QAOBI: Daily QAOBI: Daily QAOBI: Daily QA

Daily QA procedure checks the geometric Daily QA procedure checks the geometric accuracy of the OBI system by performing accuracy of the OBI system by performing the following tests:the following tests:Test 1Test 1: Tube/detector positioning accuracy: Tube/detector positioning accuracy

Assures that the imagers (MVD &KVS/KVD) isocenter Assures that the imagers (MVD &KVS/KVD) isocenter matches the LINAC isocentermatches the LINAC isocenter

Test 2Test 2: Matching and couch motion: Matching and couch motionTest 2Test 2: Matching and couch motion : Matching and couch motion accuracyaccuracy

Positional differences detected by the OBI workstation Positional differences detected by the OBI workstation b li bl t f d t h tib li bl t f d t h tican be reliably transferred to couch motion can be reliably transferred to couch motion


The Cube Isocenter Phantom provided by The Cube Isocenter Phantom provided by VarianVarian was was used for this daily QA procedureused for this daily QA procedureTwo sets of 1 5Two sets of 1 5 mm lead shots (bbs) were used tomm lead shots (bbs) were used toTwo sets of 1.5Two sets of 1.5--mm lead shots (bbs) were used to mm lead shots (bbs) were used to define 2 separate spatial locations (points.)define 2 separate spatial locations (points.)In each set, one bb is on the anterior side (AP bb) In each set, one bb is on the anterior side (AP bb) , ( ), ( )and the other (Lat bb) is on the lateral side of the and the other (Lat bb) is on the lateral side of the phantomphantomThe first set defines the isocenter (at the phantomThe first set defines the isocenter (at the phantomThe first set defines the isocenter (at the phantom The first set defines the isocenter (at the phantom center) and the second set defines a point 1.5 cm center) and the second set defines a point 1.5 cm anterior, inferior, and lateral from the isocenteranterior, inferior, and lateral from the isocenter


The OBI daily QA procedure starts with setting up the Cube phantom center (central bb set) at the mechanical isocenter of the linac by using the cross hairs projections anteriroly and laterally

OBI: Daily QAOBI: Daily QA

Lat DRR Lat KV ImageV ge

Using the plan created from Eclipse, AP MV (or KV) and Lat KV images were acquired (shown only Lat image)

OBI: Daily QAOBI: Daily QA--Test 1Test 1OBI: Daily QAOBI: Daily QA--Test 1Test 1

L t DRR AP DRRKV L t Im MV AP ImLat DRR AP DRRKV Lat Image MV AP Image

The alignment of the central bbs with the digital graticule (representing the imager isocenter) will be checked from both AP and Lat images


Long: __ mm OK ≤ 1.5 mm Long: __ mm OK ≤ 1.5 mm

Lat: __ mm OK ≤ 1.5 mm Vert: __ mm OK ≤ 1.5 mm

3 translational shifts between the center of the graticule and the center of the bbs were measured and tabulated


MV Isocenter Check

11.21.41.6

mat

ch

(mm

)

S/I

0 20.40.60.8

1

Dai

ly m

ism

dist

ance

( S/IR/L

00.2

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31Daily measurement (days)

D d

OBI: Daily QAOBI: Daily QA-- Test 1Test 1OBI: Daily QAOBI: Daily QA-- Test 1Test 1

KV Isocenter Check

0 81

1.21.4

ism

atch

e (m

m)

0.20.40.60.8

Dai

ly m

idi

stan

c S/IA/P

01 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31

Daily Measurement (days)

OBI Isocenter Accuracy OBI Isocenter Accuracy QAQA

OBI: Daily QAOBI: Daily QA--Test 2Test 2OBI: Daily QAOBI: Daily QA--Test 2Test 2Move the center of the DRR to overlay on the o ove y o eoff axis bb of the image

If test 1 is acceptable, the DRRs (AP & Lat) were moved to overlay on the off-axis bbs of the images


|A-B|Final CouchCouch Vert

New couch11.9

Shift1.6

A≤0.2

B

Couch VertCouch LngCouch Lat

11.9

116.4

3.7

1.6

1.6

1.5

The shifts obtained will be applied to remotely move the couch. The shifts and the new couch positions will be recorded

OBI: Daily QAOBI: Daily QA--Test 2Test 2OBI: Daily QAOBI: Daily QA Test 2Test 2

Linac Cross hairs

B|A-B|

0 1≤0.2OK

Final Couch11 8Couch Vert

New couch11 9

Shift1 6

A

0.10.10

OKOKOK

11.8116.53.7

Couch VertCouch LngCouch Lat

11.9116.43.7

1.61.61.5

Cross hairs projected from the linac should cross the off- axis bb set on the phantom

Manual couch motion might be needed to assure the overlay of the cross hairs and h f h ff i bbthe center of the off-axis bb set

Final couch positions will be recorded. The difference between the final and new couch positions should be within 2 mm

Results:2D/2D matchResults:2D/2D matchResults:2D/2D matchResults:2D/2D match

SummarySummary--Daily QADaily QASummarySummary--Daily QADaily QA

The suggested QA tests assure reliable portal The suggested QA tests assure reliable portal images for verification of daily patient positioningimages for verification of daily patient positioningThe procedure is simple and easy to implement. It The procedure is simple and easy to implement. It takes about 10 minutes to do the QAtakes about 10 minutes to do the QAAccuracy the procedure can detect is better thanAccuracy the procedure can detect is better thanAccuracy the procedure can detect is better than Accuracy the procedure can detect is better than 2mm2mm

Monthly QAMonthly QAMonthly QAMonthly QA

The monthly QA procedure includes isocenteraccuracy over gantry rotation, checking collisioninterlock, mechanical center check, centerreproducibility, digital measurement, and imageq lit f MVD KVS nd KVDquality of MVD, KVS and KVD

OBI isocenter accuracy OBI isocenter accuracy over gantry rotationover gantry rotationover gantry rotationover gantry rotation

Acquiring KV Acquiring KV images over multi images over multi gantry rotationsgantry rotationsShown @ 4 gantry Shown @ 4 gantry

llanglesangles

ResultsResults--Gantry Gantry ISocentrictyISocentricty

Safety QASafety QA--Collision InterlocksCollision Interlocksy Qy Q

OBI Safety and OBI Safety and functionality QAfunctionality QA

Tube warm upTube warm upDoor interlockDoor interlockDoor interlockDoor interlockWarning lightsWarning lightsSt il bilitSt il bilitStorage space availabilityStorage space availabilityDatabase integrityDatabase integrity

Mechanical QA (MVD)Mechanical QA (MVD)Mechanical QA (MVD)Mechanical QA (MVD)

1. Mechanical Center Check:Measure distance between MVD cover @ (0 0 150) and isocenter@ (0,0,150) and isocenterMeasure offset between the mark and the crosshairs projected from Linac

Run-out during arm vertical travel with MVD @ (0,0,130)Measure offset between the mark and the crosshair projected from Linac

Mechanical QA (MVD)Mechanical QA (MVD)Mechanical QA (MVD)Mechanical QA (MVD)

. Digital Measurement Accuracy:

l bl d l bPlace blade calibration tool @ isocenter, acquire MV image UsingMV image Using measuring tool from OBI to measure S/I R/L l h f 10 10length of 10cm x 10cm square

Mechanical QA (KVD)Mechanical QA (KVD)Mechanical QA (KVD)Mechanical QA (KVD)

Mechanical Center Check:Rotate gantry @ 90◦ so that KVD @ (0,0,150) is on the Floor

Measure distance between grid surface and IsocentergMeasure offset between the mark and laser projected from ceiling

Run-out during arm vertical travel with KVD @ (0,0,130)M ff b h k d l j d f iliMeasure offset between the mark and laser projected from ceiling

Mechanical QA (KVD)Mechanical QA (KVD)Mechanical QA (KVD)Mechanical QA (KVD)

1. Mechanical Center Check:Rotate gantry @ 270◦ so thatRotate gantry @ 270 so thatKVS @ (0,0,100) is on the floor• Measure distance between KVS plate and isocenter• Measure offset between the

k d l j d fmark and laser projected from ceiling

ResultsResultsResultsResults

KVD & KVS mechanical displacement over 1 yearKVD & KVS mechanical displacement over 1 year period

Image Quality QAImage Quality QAImage Quality QAImage Quality QA

To establish baseline for image quality To establish baseline for image quality parameters and to monitor these parameters and to monitor these ppparameters over timeparameters over timeAdopted tests from conventional QAAdopted tests from conventional QAAdopted tests from conventional QA Adopted tests from conventional QA programs for radiographic unitsprograms for radiographic units

Image Quality (MVD)Image Quality (MVD)Image Quality (MVD)Image Quality (MVD)

Set MVD @ (0,0,150) and place th V Ph t th t p fthe Vegas Phantom on the top of MVD .

• Acquire MV high quality image• The max R visible in C1

determines contrast, and the max C visible in R1 determines resolution

Image Quality (KVS/KVD)Image Quality (KVS/KVD)Image Quality (KVS/KVD)Image Quality (KVS/KVD)

Set KVD @ (0,0,150) and place the Leeds Phantom TOR 18FGon the top of KVD

18 disks of 8 mm diameter each with contrast ranging between 16.7% and 0.9% and central 21 bar patterns ranging between 0.5 to 5 lp/mm

– Contrast: Acquire single high quality image and fluoroscopic mode ~(70 kVp, 25 mA, 6 ms) with 1

l t KVSmm copper plate over KVS The number of visible disks along the rim determines the contrast11 (3.2%) or 12 (2.7%) contrast disks or more should b di blbe discernable

– Spatial Resolution: Take a KV radiographic and fluoroscopic exposure ~( 50 kVp, 80 mA, 32 ms)Select the smallest visible group of line pairs11th group of bars, equivalent to 1.6 lp/mm should be visible

CBCT QACBCT QACBCT QACBCT QA

Didn’t include a separate geometric Didn’t include a separate geometric measurement for CBCT imagesmeasurement for CBCT imagesggGeometry of KV radiographs and CBCT Geometry of KV radiographs and CBCT images depend upon the position ofimages depend upon the position ofimages depend upon the position of images depend upon the position of the OBI armsthe OBI arms

CBCT Image qualityCBCT Image qualityCBCT Image qualityCBCT Image quality

QA tests adopted from QA tests adopted from diagnostic CT scannersdiagnostic CT scanners

Alternate check of fullAlternate check of full--fan and fan and halfhalf--fan modesfan modes

Use the Catphan 504 phantomUse the Catphan 504 phantom

Scan acquired 125 kVp, 80 Scan acquired 125 kVp, 80 A 25 150 SID ithA 25 150 SID ithmA, 25 ms 150 SID with mA, 25 ms 150 SID with

512x512 reconstruction matrix 512x512 reconstruction matrix and 2.5 mm slice thicknessand 2.5 mm slice thickness

HU AccuracyHU AccuracyHU AccuracyHU Accuracy

CTP 404 inserts contains 7 materials of CTP 404 inserts contains 7 materials of different densitiesdifferent densitiesUsing ROI 0.7x0.7 cm Using ROI 0.7x0.7 cm HU values should be within 40 HUHU values should be within 40 HUHU values should be within 40 HUHU values should be within 40 HU

HU AccuracyHU Accuracy--OBI 1 3OBI 1 3HU AccuracyHU Accuracy--OBI 1.3OBI 1.3

Low Contrast Low Contrast ResolutionResolution

CTP 515 insert 3 CTP 515 insert 3 groups of supragroups of supra--slice disks withslice disks withslice disks with slice disks with diameters ranging diameters ranging from 2from 2--15 mm and 15 mm and subject contrasts of subject contrasts of 1%, 0.5%, and 1%, 0.5%, and 0 3%0 3%0.3%0.3%Recommendation Recommendation 1%, 7 mm disk1%, 7 mm disk1%, 7 mm disk 1%, 7 mm disk

Spatial ResolutionSpatial ResolutionSpatial ResolutionSpatial Resolution

CTP 528 insert CTP 528 insert contains a spatial contains a spatial resolution rule with resolution rule with bar patterns bar patterns between 1 to 21between 1 to 21between 1 to 21 between 1 to 21 lp/cmlp/cmRecommendationRecommendationRecommendation Recommendation 6lp/cm6lp/cm

HU UniformityHU UniformityHU UniformityHU Uniformity

CTP 486 insert is a uniform disk of 20 CTP 486 insert is a uniform disk of 20 cm diameter cm diameter Area profile used 5 ROIs Area profile used 5 ROIs Within 40 HUsWithin 40 HUsWithin 40 HUsWithin 40 HUs

SummarySummarySummarySummary

The complex nature of the radiation therapy The complex nature of the radiation therapy process and the need to produce a patient specific process and the need to produce a patient specific treatment that maximizes the therapeutic ratiotreatment that maximizes the therapeutic ratiotreatment that maximizes the therapeutic ratio treatment that maximizes the therapeutic ratio requires “proper” integration of IGRT systems into requires “proper” integration of IGRT systems into the processthe process

This requires significant effort to implement and to This requires significant effort to implement and to employemployemploy employ


OBI is one of these systems designed to correct for OBI is one of these systems designed to correct for motion and setup errors of patientsmotion and setup errors of patients

We presented a QA program to monitor the We presented a QA program to monitor the mechanical and image quality of the system mechanical and image quality of the system

The tests use tools and phantoms provided with the The tests use tools and phantoms provided with the OBI systemOBI system

Since OBI is a device to improve geometric Since OBI is a device to improve geometric accuracy of patient treatments, the most critical accuracy of patient treatments, the most critical tests are those of its mechanical stability/accuracytests are those of its mechanical stability/accuracytests are those of its mechanical stability/accuracytests are those of its mechanical stability/accuracy


Measurements show that mechanical stability of the Measurements show that mechanical stability of the OBI system is quite high with SD of 0.3 to 0.4 mm OBI system is quite high with SD of 0.3 to 0.4 mm over 1 year period monitored by the geometricover 1 year period monitored by the geometricover 1 year period monitored by the geometric over 1 year period monitored by the geometric positioning of the armspositioning of the arms

Tests were useful in detecting performance deficits Tests were useful in detecting performance deficits

Implementation of QA tests, methods, frequency, Implementation of QA tests, methods, frequency, and tolerances could vary. However, it s important and tolerances could vary. However, it s important to establish a guidelineto establish a guidelineto establish a guidelineto establish a guideline


More work should be done on More work should be done on improving image qualityimproving image qualityp g g q yp g g q ySmooth flow of data Smooth flow of data More work on automatic fusionMore work on automatic fusionMore work on automatic fusionMore work on automatic fusion

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