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©© LC 2007LC 2007
Treatment planning systemsTreatment planning systems
PD Dr. L. CozziPD Dr. L. CozziOncology Institute of Southern SwitzerlandOncology Institute of Southern Switzerland
‘‘adaptive’adaptive’
‘‘conventional’conventional’
‘‘conformal’conformal’
‘‘intensity modulated’intensity modulated’
RadiotherapyRadiotherapythe principle is the same now as it was 100 years ago: the principle is the same now as it was 100 years ago:
high dose to the volume of the patient containing tumour cellshigh dose to the volume of the patient containing tumour cellsand and no dose elsewhereno dose elsewhere
all modalities are nowadays used worldwide
all modalities are nowadays used worldwide
timetime1980s1980s 1990s1990s 2000s2000s1970s1970s
©© LC 2007LC 2007
Intensity modulated treatments IMRT (2000s, ..)Imaging:Imaging:33--D imagesD images: : CT, MRI, SPECT, PET.CT, MRI, SPECT, PET. It is possible to generate It is possible to generate both anatomical and functional tumour volumes. (as both anatomical and functional tumour volumes. (as conformal)conformal)
Target definition:Target definition:based on 3based on 3--D images: D images: better (and personalised) better (and personalised) determination of the Planning Target Volumedetermination of the Planning Target Volume (as conformal)(as conformal)
Beam arrangement:Beam arrangement:CTCT--basedbased. N fields, up to 6, with different entrances, even . N fields, up to 6, with different entrances, even not coplanar (beam axis not through an axial slice): BEV not coplanar (beam axis not through an axial slice): BEV (Beam’s Eye View) is used. (Beam’s Eye View) is used.
(Field shaping) Intensity Shaping:(Field shaping) Intensity Shaping:An An optimisationoptimisation process calculates, starting from Dose process calculates, starting from Dose Contstraints on the drawn volumes (PTV, OR or PRV), the fluence Contstraints on the drawn volumes (PTV, OR or PRV), the fluence per each fieldper each field
Dose calculation:Dose calculation:33--DD calculation. calculation. Heterogeneities are accounted for Heterogeneities are accounted for using CT using CT numbers. Doses are often calculated on fluence base.numbers. Doses are often calculated on fluence base.
©© LC 2007LC 2007
Image data Image data (CT, MRI, PET, …)(CT, MRI, PET, …)
Machine data Machine data (beam (beam dosimetrydosimetry, machine geometry), machine geometry)
Patient ModelsPatient Models Beam/Machine ModelsBeam/Machine Models
Segmentation and Segmentation and modelingmodeling Beam fitting and Beam fitting and modelingmodeling
Treatment plan Treatment plan
Treatment designTreatment design
Dose distributionDose distribution
CalculationCalculationEvaluationEvaluation
Treatment delivery aidsTreatment delivery aids
DocumentationDocumentation
©© LC 2007LC 2007
The treatment planning chainThe treatment planning chain
Treatment planningTreatment planningwhat shall be donewhat shall be done
1)1) InputInput CT slicesCT slices2)2) Creation of a Creation of a 3D study3D study from single CT slices from single CT slices 3)3) RegistrationRegistration between CT and MRI, PET, ... between CT and MRI, PET, ... image fusion algorithmsimage fusion algorithms4)4) ContouringContouring: targets and OARs : targets and OARs segmentation segmentation algorithmsalgorithms5)5) PlanningPlanning: define beam arrangement and calculate : define beam arrangement and calculate dose distribution dose distribution dose calculation algorithmsdose calculation algorithms6)6) EvaluationEvaluation: dose distribution visualisation, DVH, : dose distribution visualisation, DVH, dose statistics, TCP/NTCP, ... dose statistics, TCP/NTCP, ...
©© LC 2007LC 2007
Image fusion: example CT/MRImage fusion: example CT/MR
MR (purple) andMR (purple) andCT (grey) imagesCT (grey) images
before fusionbefore fusion MR and CTMR and CToverlaidoverlaid
Fused imageFused image
Volumes can be outlined on MRI and automatically overlaid on CTVolumes can be outlined on MRI and automatically overlaid on CT
©© LC 2007LC 2007
CT: the artifacts problemCT: the artifacts problem
©© LC 2007LC 2007
it is generally possibleit is generally possibleto assign fixed HU to to assign fixed HU to a specified region, where a specified region, where the artifacts may stronglythe artifacts may stronglyaffect dose calculationaffect dose calculation
DRR: Digital Reconstructed RadiographDRR: Digital Reconstructed Radiograph
The starting pointThe starting pointis the CTis the CTdatasetdataset
The result is a ’reconstructed’ radiographThe result is a ’reconstructed’ radiograph
©© LC 2007LC 2007
DRR: different filteringDRR: different filtering
©© LC 2007LC 2007
Image Acquisition of Moving Targets
Rietzel et al, Med. Phys., 2005
no gating
gating
©© LC 2007LC 2007
Image Acquisition of Moving Targets
no gating
©© LC 2007LC 2007
Prospective
Patient Immobilized on
CT
RetrospectivePatient Immobilized
on CTX-ray on
RPM Respiratory Gating System
TriggersX-ray on
RPM System Collects Respiration Phase Data
Planning
Standard Geometric Planning
Advantage 4D Synchronizes Image Data With Respiratory
Cycle
4D CT Image Acquisition
©© LC 2007LC 2007
Respiration Waveform from RPM Respiratory Gating System
CT Scan
Axial scan trigger,1st couch position
Axial scan trigger, 2nd couch position
Exhalation
Scan Scan Scan
Inhalation
Axial scan trigger,3rd couch position
Prospective CT Image Acquisition
©© LC 2007LC 2007
X-ray on
Exhalation
Inhalation
“Image acquired”signal to RPM system
1st couch position
Retrospective 4D CT Image AcquisitionRespiration Waveform from RPM Respiratory Gating System
2nd
couch position
3rd couch position
©© LC 2007LC 2007
4D Data and images courtesy VUmc, Amsterdam, The Netherlands
Prospective Gating
Conventional CT Image Gated CT Image
Images Courtesy Medical College of Virginia, Richmond VA
Tumor
©© LC 2007LC 2007
Retrospective gating
4D Data and images courtesy VUmc, Amsterdam, The Netherlands
80% isodose: volume13 vs. 27 cc20% isodose: volume163 vs.471 cc
©© LC 2007LC 2007
4D image registration• Sets of 3D CT scans - corresponding to different phases of breathing
- can be registered according to DICOM coordinates
• Sets of 3D PET scans can be co-registered with the corresponding 3D CT scans (based on scanner coordinates and/or aided by fiducials)
©© LC 2007LC 2007
3D planning:3D planning:Photon dose calculation modelsPhoton dose calculation models
©© LC 2007LC 2007
courtesy A. Ahnesjö
The physics behind photon dose calculationThe physics behind photon dose calculation
Pair production
Compton
Photoelectric
©© LC 2007LC 2007
Machine dataMachine data
Beam profiles, depth doses,Beam profiles, depth doses,Output factors, Wedge factors,Output factors, Wedge factors,Absolute Absolute dosimetrydosimetry for MUfor MUcomputation, … computation, …
MODELING MACHINE DATA:MODELING MACHINE DATA:CONFIGURATION PROCESSCONFIGURATION PROCESS
1)1) Dose calculation algorithm of TPS is able to compute dose distriDose calculation algorithm of TPS is able to compute dose distribution bution under arbitrary conditions from under arbitrary conditions from basidbasid data coming from configurationdata coming from configuration
2)2) Dose calculation algorithm is able to compute any allowed conditDose calculation algorithm is able to compute any allowed condition ion within certain accuracywithin certain accuracy
3)3) Dose calculation algorithm can compute dose distributions in patDose calculation algorithm can compute dose distributions in patient ient datasetdataset©© LC 2007LC 2007
Patient dataPatient data
To compute dose To compute dose distribution, patient distribution, patient data are required:data are required:
1)1) Patient anatomy in Patient anatomy in terms of ‘terms of ‘geometrygeometry’’
2)2) Patient anatomy in Patient anatomy in terms of ‘terms of ‘matter matter compositioncomposition’’
Patients composition: in principle, to use the “whole physics” (Patients composition: in principle, to use the “whole physics” (interactions), the interactions), the medium has to be known in terms of atomic composition medium has to be known in terms of atomic composition NOT POSSIBLENOT POSSIBLESolution: CT data give Solution: CT data give HounsfieldHounsfield NumbersNumbers, that can be related to , that can be related to mass or mass or electron densityelectron density of the mediumof the medium this is a crude approximation of the real this is a crude approximation of the real patient. patient. Cross sections of physical interactions are powers of the electrCross sections of physical interactions are powers of the electron density.on density.
©© LC 2007LC 2007
Algorithms have limitations that shall be knownAlgorithms have limitations that shall be known
Grade 1:Grade 1:
2D2D--planningplanning
Grade 2:Grade 2:
3D3D--planningplanning
In practice:In practice:
Grade 0:Grade 0:
CTVOI on slicedose on slice CT
VOI on patient volumedose on patient volume
©© LC 2007LC 2007
No electron transport Electron transport(local energy deposition, TERMA) (non-local energy deposition, DOSE)
- Linear attenuation - Superposition/Convolution: 1-D - Ratio of TAR: EPL, (Pencil Beam)
eff SSD, isodose shift - FFT techniques- Power law (Batho)
- EqTAR - Superposition/Convolution3-D - dSAR (Collapsed Cone, MGS, AAA)
- DVOL - Monte Carlo- 3D Beam Subtraction
Electron transport
Leve
l of
anat
omy
sam
pled
©© LC, AFC,GN 2007LC, AFC,GN 2007©© LC, AFC,GN 2007LC, AFC,GN 2007
AAPM report 85, 2004
Dose calculation algorithm Dose calculation algorithm classificationsclassifications
Lung
inse
rt
Lung
inse
rt
ρρ =0.
2 g/
cm=0
.2 g
/cm
33
Large field 13x13 cmLarge field 13x13 cm22 Small field 3x13 cmSmall field 3x13 cm22
©© LC, AFC,GN 2007LC, AFC,GN 2007
©© LC, AFC,GN 2007LC, AFC,GN 2007
Energy fluencedose dep. kernel absorbed dose
Superposition
Pencil beam is a convolution/superpos.PB calculates in homogeneous mediaCorrective methods are necessaryVarian: Matho, Mod. batho, ETAR
TMS, OMP: EPL type
these approximations are used to generate Pencil Beams
Absorbed dose is given by superposition of pencil beams
TERMA
dose dep. kernel absorbed dose
Too time consuming!
Phase Space ModelPhase Space Model
•• Initial Phase SpaceInitial Phase Space–– Source to bottom of jawsSource to bottom of jaws–– Models accelerator headModels accelerator head
•• Modified Phase SpaceModified Phase Space–– Bottom of jaws to patient Bottom of jaws to patient
surfacesurface–– Models beam modifiersModels beam modifiers
IPS
MPS
©© LC 2007LC 2007
Phase Space ModelPhase Space Model
•• MultipleMultiple--Source ModelSource Model–– Photon SourcesPhoton Sources
•• Primary sourcePrimary source–– TargetTarget
•• ExtraExtra--focal (secondary) sourcefocal (secondary) source–– Flattening filter, beam limiting Flattening filter, beam limiting
devicesdevices–– Electron ContaminationElectron Contamination
•• Flattening filter, beam limiting Flattening filter, beam limiting devicesdevices
•• Beam modifiersBeam modifiers•• Source parametersSource parameters
–– Initial energy spectrumInitial energy spectrum–– Mean radial energyMean radial energy–– Fluence intensityFluence intensity
©© LC 2007LC 2007
Beam Modifiers
• Beam modifiers affect– Fluence
• Block, MLC, DW, IMRT– Fluence and Spectral Characteristics
• Hard wedges
• Head scatter changes– Secondary source modifications– Electron source modifications
©© LC 2007LC 2007
Beam ModelBeam Model
•• BeamletsBeamlets–– Field divided into beamletsField divided into beamlets–– Beamlet size corresponds to Beamlet size corresponds to
calculation gridcalculation grid–– Beamlets diverge along Beamlets diverge along
fanlinesfanlines–– Uniform fluence within Uniform fluence within
beamletbeamlet–– Dose calculated along the Dose calculated along the
beamletbeamlet–– Beamlet kernel convolution Beamlet kernel convolution
performed for each sourceperformed for each source
©© LC 2007LC 2007
Patient Model
• Voxels– Patient divided into 3D voxels– Voxels have divergent geometry– Mean electron density
computed for each voxel• Based on patient CT data
– Voxel dose obtained by superposition of beamlet contributions
©© LC 2007LC 2007
Dose CalculationDose Calculation
Focal and extra focal photonsFocal and extra focal photons
©© LC 2007LC 2007
Beamlet ParametersBeamlet Parameters
•• Photon fluencePhoton fluence ΦΦββ–– Describes beam radial eDescribes beam radial energy spectrumnergy spectrum–– Assumed to be uniform within beamletAssumed to be uniform within beamlet ββ
•• Energy deposition density functionEnergy deposition density function IIββ((z,z,ρρ))–– Polyenergetic function: Based on energy Polyenergetic function: Based on energy
spectrum, superposition of prespectrum, superposition of pre--calculated calculated monoenergetic energy deposition density monoenergetic energy deposition density functions functions
•• Scatter kernelScatter kernel KKββ(x,y,z,(x,y,z,ρρ))–– Models lateral energy scatteringModels lateral energy scattering
©© LC 2007LC 2007
Energy Distribution due to PhotonsEnergy Distribution due to Photons
Energy deposited in a point for each beamlet Energy deposited in a point for each beamlet ββ is obtained by is obtained by convolutionconvolution
ΦΦββ fluence intensity of the pencil beamfluence intensity of the pencil beamIIββ(z,(z,ρρ)) energy deposition density functionenergy deposition density functionKKββ(x,y,z,(x,y,z,ρρ)) lateral scatter kernellateral scatter kernel
Applies to homogeneous mediumApplies to homogeneous medium
∫∫∈
−−××Φ=)(Area)v,u(
,ph dudv),z,yv,xu(K),z(I)z~,y~,x~(Eβββββ ρρ
©© LC 2007LC 2007
Depth Density ScalingDepth Density Scaling
Energy deposition density functionEnergy deposition density function–– Accounts for tissue heterogeneity by Accounts for tissue heterogeneity by
employing the concept of radiological scalingemploying the concept of radiological scaling–– New calculation depth determinedNew calculation depth determined–– Depth scaled according to heterogeneityDepth scaled according to heterogeneity
( )water
zzIzIρ
ρρ ββ,0,0)(),( ′=
dttzz
water∫=′0
),0,0(ρ
ρwhere ρ electron density
©© LC 2007LC 2007
Scatter Kernel ModelScatter Kernel Model
•• Monoenergetic scatter kernelsMonoenergetic scatter kernels–– Monte Carlo precalculated data for differentMonte Carlo precalculated data for different
•• EnergiesEnergies•• MaterialsMaterials
•• Polyenergetic scatter kernelsPolyenergetic scatter kernels–– Weighted sum of monoenergetic kernelsWeighted sum of monoenergetic kernels–– Scaled according to the densityScaled according to the density–– Used for the beamlet convolutionUsed for the beamlet convolution
©© LC 2007LC 2007
Lateral Density Scaling ofLateral Density Scaling ofPhoton Scatter KernelsPhoton Scatter Kernels
Energy scaling at each location by the average density between Energy scaling at each location by the average density between the calculation point and the origin of the pencil beamthe calculation point and the origin of the pencil beam
∑=
−=5
0
),,(1)'(),,(),,(k
yxrk
water
dker
zczyxzyxK ρμβ ρ
ρ
WhereWhere rrdd = = RadiologicalRadiological distance distance fromfrom kernelkernel originorigin (0,0,z) to (0,0,z) to ((x,y,zx,y,z) ) alongalong rayray R R thatthat passespasses throughthrough ((x,yx,y))
td)t(),y,x(rR water
d
rr
∫= ρρρ
©© LC 2007LC 2007
Dose CalculationDose Calculation
Contaminating Electron DoseContaminating Electron Dose
©© LC 2007LC 2007
Electron Contamination
• Electrons produced in– Flattening filter– Ionization chamber– Collimator jaws– Beam modifiers– Air
• Depends strongly on – Photon energy spectrum– Field size
©© LC 2007LC 2007
Energy Distribution due to Energy Distribution due to ElectronsElectrons
Energy deposited in a point for each beamletEnergy deposited in a point for each beamlet ββ is obtained by is obtained by convolutionconvolution
∫∫∈
−−××Φ=)(Area)v,u(
,cont,cont,cont,cont dudv),z,yv,xu(K),z(I)z~,y~,x~(Eβ
ββββ ρρ
ΦΦcontcont,,ββ Fluence of cont. electrons is determined by convolving the Fluence of cont. electrons is determined by convolving the photon fluence with a ’sum of Gaussians’photon fluence with a ’sum of Gaussians’--kernelkernel KKfl,efl,e
IIcont,cont,ββ((z,z,ρρ)) Determined from measured data and tabulatedDetermined from measured data and tabulated
KKcont,cont,ββ((x,y,zx,y,z,,ρρ)) lateral scatter kernellateral scatter kernel
⎥⎦
⎤⎢⎣
⎡ +−= 2
22
2 221
EE,cont
yxexpKσπσβ
©© LC 2007LC 2007
Dose CalculationDose Calculation
Superposition / Conversion to DoseSuperposition / Conversion to Dose
©© LC 2007LC 2007
Absorbed energy is obtained by superposition ofAbsorbed energy is obtained by superposition ofthe separate energy contributions from all sourcesthe separate energy contributions from all sources
–– Primary photonsPrimary photons
–– ExtraExtra--focal photonsfocal photons
–– Contaminating electronsContaminating electrons
( )∑ ++=β
βββ )z~,y~,x~(E)z~,y~,x~(E)z~,y~,x~(E)z~,y~,x~(E ,cont,ph,ph 21
SuperpositionSuperposition
©© LC 2007LC 2007
Convolution/SuperpositionConvolution/Superposition
•• ConvolutionConvolution
–– Primary photon beamPrimary photon beam
–– ExtraExtra--focal photon beamfocal photon beam
–– Contaminating electronsContaminating electrons
•• SuperpositionSuperposition
–– Sums convolution resultsSums convolution results
–– Produces final energy Produces final energy depositiondeposition
©© LC 2007LC 2007
ConversionConversion to Doseto Dose
AssumptionAssumption::Different Different heterogeneitiesheterogeneities cancan bebe modifiedmodified as as scaledscaledwaterwater
)z~,y~,x~()z~,y~,x~(E)z~,y~,x~(D water
ρρ
=
©© LC 2007LC 2007
CT: electron density calibrationCT: electron density calibrationcalibration curve:calibration curve:
CT number CT number vsvs electron densityelectron density
the calibration curve is used tothe calibration curve is used tohave tissue density corrections in have tissue density corrections in
dose calculationdose calculation
Rel. electron density vs HURel. electron density vs HU
ρρee=1 @ HU=0=1 @ HU=0
Mass density vs HUMass density vs HU
ρρ=1 @ HU=0=1 @ HU=0
©© LC 2007LC 2007
Dose CalculationDose Calculation
MU CalculationMU Calculation
©© LC 2007LC 2007
MU Calculation
• Based on– Output factor measurements– Calibration calculations made for the reference field size– Collimator back-scatter factor
• Final MUs calculated from– Prescribed Dose– Plan Normalization– Field weight– Field normalization
©© LC 2007LC 2007
PracticalPractical demosdemos::
•• SupportiveSupportive toolstools ((e.ge.g. DRR, BEV). DRR, BEV)•• BeamBeam modifiersmodifiers ((wedgeswedges and MLC)and MLC)•• DensityDensity on/offon/off•• Standard Standard vsvs advanceadvance plansplans•• System System configurationconfiguration
©© LC 2007LC 2007
3D view of the drawn STRUCTURES3D view of the drawn STRUCTURES + BEAMS+ BEAMSThe BEV: Beam’sThe BEV: Beam’s--EyeEye--ViewView
The
Room
’s-Ey
e-Vi
ewTh
e Be
am’s-
Eye-
View
©© LC 2007LC 2007
Open beamOpen beam ... BEV with organs at risk ...... BEV with organs at risk ...
MLC shieldingMLC shielding Block shieldingBlock shielding
Beam shapingBeam shaping
©© LC 2007LC 2007
MLC optionsMLC options
0.6 cm marginInside
0.6 cm marginOutside
0.6 cm marginMiddle
©© LC 2007LC 2007
0.6 cm marginMiddle
0.6 cm marginMiddleOptim coll rot
MLC optionsMLC options
©© LC 2007LC 2007
MLC optionsMLC options
©© LC 2007LC 2007
Block optionsBlock options
ApertureAperture
ShieldingShielding
ApertureAperture
©© LC 2007LC 2007
3D target volume3D target volume Box Box –– open fieldsopen fields
Box Box -- MLCMLC Box Box -- BlocksBlocks
Case: Prostate, 4field box. The 90% isodoseCase: Prostate, 4field box. The 90% isodose
©© LC 2007LC 2007
©© LC 2007LC 2007
Open beam Wedged beam
Dose Profile shape
Wedge material absorbepart of the dose:
Transmission factor WF:D(wedge)D(open)
for specified MU
Inhomogeneous dose in the beam
Standard hard wedgesStandard hard wedges
©© LC 2007LC 2007
Standard hard wedgesStandard hard wedges
1515°° 3030°°
4545°° 6060°°
WF=0.770WF=0.770 WF=0.625WF=0.625
WF=0.493WF=0.493 WF=0.405WF=0.405
105%105%93%93%
115%115%
85%85%
125%125%
80%80%
160%160%
70%70%
©© LC 2007LC 2007
Standard hard wedgesStandard hard wedges
1515°° 3030°°
4545°° 6060°°
WF=0.770WF=0.770 WF=0.625WF=0.625
WF=0.493WF=0.493 WF=0.405WF=0.405
105%105%93%93%
115%115%
85%85%
125%125%
80%80%
160%160%
70%70%
80%80%
©© LC 2007LC 2007
Standard hard wedgesStandard hard wedges
WF=0.770WF=0.770 WF=0.625WF=0.625
WF=0.493WF=0.493 WF=0.405WF=0.405
105%105%93%93%
115%115%
85%85%
125%125% 160%160%
70%70%
1515°° 3030°°
4545°° 6060°°
©© LC 2007LC 2007
Dynamic (virtual) wedgesDynamic (virtual) wedges
Wedge profile using openWedge profile using openfields with dynamic movementfields with dynamic movement
of the jaws.of the jaws.Mechanical hard wedge absent.Mechanical hard wedge absent.Generally only for one of the Generally only for one of the
two couple of jaws two couple of jaws (overtravel)(overtravel)
open AP field open lat field sum AP + lat fields
wedge AP fieldwedge AP field wedge lat fieldwedge lat field sum AP + lat wedge fieldssum AP + lat wedge fields
100%
95%
105%
100%
120%
80%
The usage of wedgesThe usage of wedges
©© LC 2007LC 2007
Configuration of a TPSConfiguration of a TPS
©© LC 2007LC 2007
Measurements characterising Linac beams, modifiers Measurements characterising Linac beams, modifiers and accessoriesand accessories
Processing tools to generate phase space and Processing tools to generate phase space and parametersparameters
QA tools to guarantee at commissioning and over QA tools to guarantee at commissioning and over time the quality of TPS datatime the quality of TPS data
ExampleExample of of MeasurementMeasurement RequirementsRequirementsOpen Open FieldField
•• DepthDepth DoseDose–– AlongAlong CAXCAX–– Mandatory:Mandatory: 4x4cm4x4cm22, 6x6cm, 6x6cm22, 10x10cm, 10x10cm22, 20x20cm, 20x20cm22, , LargestLargest
FieldField SizeSize–– RecommendedRecommended:: SmallestSmallest FieldField SizeSize, 8x8cm, 8x8cm22, 30x30cm, 30x30cm22
•• ProfilesProfiles–– ddmaxmax, 5cm, 10cm, 20cm, 30cm, 5cm, 10cm, 20cm, 30cm–– Same Same FieldField SizesSizes as as forfor DepthDepth DoseDose–– MeasureMeasure at least 35mm at least 35mm pastpast thethe 50% of 50% of thethe dose on CAXdose on CAX
•• Diagonal Diagonal ProfilesProfiles–– Same Same depthsdepths as as ProfilesProfiles; ; LargestLargest FieldField SizeSize
•• Output Output FactorsFactors–– 5cm 5cm depthdepth ((notnot at at ddmaxmax))
•• Absolute Absolute DosimetryDosimetry–– ReferenceReference Dose [Gy] at Dose [Gy] at CalibrationCalibration DepthDepth forfor
•• ReferenceReference MU (MU (usuallyusually 100MU)100MU)•• ReferenceReference FieldField SizeSize ((usuallyusually 10x10)10x10)
©© LC 2007LC 2007
ExampleExample of of MachineMachine ParametersParameters
•• Parameters Parameters havehave a a significantsignificant effecteffect on on thethe optimizationoptimizationof of machinemachine parametersparameters
•• ContainsContains initialinitial guessesguesses forfor somesome treatmenttreatment unitunitparametersparameters::–– Photon Photon energyenergy spectrumspectrum–– Radial Radial energyenergy–– LocationLocation of of virtualvirtual secondarysecondary sourcesource and and thethe last last collimatingcollimating
devicedevice–– IntensityIntensity, , energyenergy and and sizesize of of thethe virtualvirtual secondarysecondary sourcesource–– Material of Material of thethe flatteningflattening filterfilter–– Initial Initial guessguess forfor thethe intensityintensity profileprofile
•• AutomaticallyAutomatically usedused as as inputinput in in thethe configurationconfiguration•• PossiblePossible to to modifymodify themthem
©© LC 2007LC 2007
ManufacturerManufacturer TPSTPS DOSE CALCULATION ALGORITHMDOSE CALCULATION ALGORITHM
3D3D--LineLine Ergo++Ergo++ PB + EPL inhomog {EqTAR under test} {MC (Tuebingen) wip}PB + EPL inhomog {EqTAR under test} {MC (Tuebingen) wip}
BrainLABBrainLAB iPlaniPlan PB + EPL inhomogPB + EPL inhomog
CMSCMS XiO, MonacoXiO, Monaco XiO: FFTC Clarkson or MGS ; Monaco: MC (Tuebingen)XiO: FFTC Clarkson or MGS ; Monaco: MC (Tuebingen)
DosisoftDosisoft ISOgrayISOgray Point kernel superp + voxelic inhomogPoint kernel superp + voxelic inhomog
IMPAC IMPAC ((Elekta)Elekta) MOSAIQMOSAIQ ’’Dose engine’:Dose engine’: MC (Tuebingen)MC (Tuebingen)
RaySearchRaySearch RayDoseRayDose ’’Dose engine’:Dose engine’: CC or PB (SingularValueDecomposition) + EPL inhCC or PB (SingularValueDecomposition) + EPL inh
ElektaElekta PrecisePlanPrecisePlan TAR/SAR (preTAR/SAR (pre--PB) {MC wip}PB) {MC wip}
MultidataMultidata RTSuiteRTSuite 3D prism PL, Clarkson3D prism PL, Clarkson
NOMOSNOMOS CORVUSCORVUS PB or MC (Peregrine)PB or MC (Peregrine)
NucletronNucletron OncentraOncentraMPMP PB + EPL inhomog or Collapsed ConePB + EPL inhomog or Collapsed Cone
PerMedicsPerMedics OdysseyOdyssey PB + EPL inhomogPB + EPL inhomog
PhilipsPhilips Pinnacle3Pinnacle3 Collapsed ConeCollapsed Cone
ProwessProwess PantherPanther Collapsed Cone or TMR + EPL inhomogCollapsed Cone or TMR + EPL inhomog
RadionicsRadionics XknifeXknife TMRTMR
SiemensSiemens KonRadKonRad [IMRT only] PB (+FFT) + EPL inhomog[IMRT only] PB (+FFT) + EPL inhomog
TomoTherapyTomoTherapy HiHi--ArtArt Convol/superpos + inhomog correct.Convol/superpos + inhomog correct.
VarianVarian EclipseEclipse PB + EPL, EqTAR inhomog or AAA {MC wip}PB + EPL, EqTAR inhomog or AAA {MC wip}©© LC 2007LC 2007
From conventional radiotherapy to From conventional radiotherapy to conformation and to intensity modulationconformation and to intensity modulation. .
The Head & Neck caseThe Head & Neck case
©© LC 2007LC 2007
Conventional treatment of head and neck cancer
Field displacement was found geometrically.Field matching is always difficult and risky: hot and cold spots are present at the level of field junction.
NO!NO! YESYES
but...but...
©© LC 2007LC 2007
Beam matchingBeam matching: : adjacent fields can cause dosimetric problems!!adjacent fields can cause dosimetric problems!!
Two matched photon fields
Dos
e in
tens
ity
with a gap with an overlap
©© LC 2007LC 2007
Beam matchingBeam matching: : adjacent fields can cause dosimetric problems!!adjacent fields can cause dosimetric problems!!
Cold spotCold spot
Hot spotHot spot
Best matching photons+electronsBest matching photons+electrons
Beam penumbrae are physics: no way to change them....Beam penumbrae are physics: no way to change them....
©© LC 2007LC 2007
Conformal treatmentConformal treatment in head and neck:in head and neck:the possibility to the possibility to avoid beam matchingavoid beam matching
Acute Mucositisat end RT
Conformal(5-field)
Conventional(phot+elec)
Grade 1 17% 7%Grade 2 48% 36%Grade 3 34% 57%
Acute Dermitisat end RT
Conformal(5-field)
Conventional(phot+elec)
Grade 1 26% 14%Grade 2 59% 65%Grade 3 15% 21%
Late MucositisConformal
(5-field)Conventional(phot+elec)
Grade 0 68% 58%Grade 1 21% 27%Grade 2 11% 12%Grade 3 0% 3%
Late DermitisConformal
(5-field)Conventional(phot+elec)
Grade 0 82% 54%Grade 1 14% 34%Grade 2 4% 11%Grade 3 0% 0%
©© LC 2007LC 2007
IMRT 5 IMRT 5 fldfld ConformalConformal 5 5 fldfld
PTVIIPTVII
©© LC 2007LC 2007
IMRT 5 IMRT 5 fldfld ConformalConformal 5 5 fldfld
PTVIIPTVII
©© LC 2007LC 2007
IMRT 5 IMRT 5 fldfld ConformalConformal 5 5 fldfld
PTVIIPTVII
©© LC 2007LC 2007
IMRT 5 IMRT 5 fldfld ConformalConformal 5 5 fldfld
PTVIIPTVII
©© LC 2007LC 2007
From conventional radiotherapy to From conventional radiotherapy to conformation and to intensity modulationconformation and to intensity modulation. .
The Breast caseThe Breast case
©© LC 2007LC 2007
THE THE CONVENTIONALCONVENTIONAL TREATMENTTREATMENT
RT in RT in BreastBreast Cancer: Cancer: thethe techniquestechniques
AdvancedAdvanced--stagestage: : breastbreast + + supraclavicularsupraclavicular nodesnodes
• 2 tangential fields• 1-2 opposed ap fields
Two Two tangentstangents
AnteroAntero--posteriorposterior
FieldField matchingmatching!!!!
Problems:- field matching- high dose to
apex of lung
2 mm gap2 mm overlap
The The tangentstangents
The The AnteroAntero--posteriorposterior
©© LC 2007LC 2007
FieldFieldmatchingmatching!!!!
PhotonsPhotons//photons
photons
FieldField matchingmatching!!!!
PhotonsPhotons//ele
ctrons
electrons
THE THE CONVENTIONALCONVENTIONAL TREATMENTTREATMENT
RT in RT in BreastBreast Cancer: Cancer: thethe techniquestechniques
• 2 tangential
• 1-2 supraclav+axilla
• 1 electron IMN
AdvancedAdvanced--stagestage: : breast+supraclavicularbreast+supraclavicular nodes+internalnodes+internal mammarymammary nodesnodes
coldtriangle
The electron
The electron fieldfield
The The tangentstangents
The The AnteroAntero--posteriorposterior
Problems:- field matching(especiallyphotons/electrons- high dose heartand lung- geographycal miss in an internal quadrant where you likely have/had disease
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60º 200º200º 180º180º
A A conformalconformal exampleexample
A three field technique without matchingA three field technique without matching
EarlyEarly--stagestage: whole breast only: whole breast only
60º 200º200º 180º180º
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Another Another conformalconformal exampleexample
A two nonA two non--coplanar field technique without matchingcoplanar field technique without matching
EarlyEarly--stagestage: whole breast only: whole breast only
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2F-NC
ComparingComparing conformalconformal examplesexamples EarlyEarly--stagestage: : wholewhole breastbreast onlyonly
2F
3F-C
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2F-NC 3F-C 2F
ResultsResults: : comparison 2F (conv), 3F, 2Fcomparison 2F (conv), 3F, 2F--NCNC
50%50%70%90%100%
©© LC 2007LC 2007
Why IMRTWhy IMRT? examples for chest wall or IMC? examples for chest wall or IMCMore than conventional: 3 fields IMRTConventional: 2 tangential fields
50%70%90%120%
Electrons Gantry 0 shif/overlap
Electrons Gantry matched with photons IMRT
Electrons Gantry 0
Electrons Gantry “half” matched
AdvancedAdvanced--stagestage: breast + nodal areas: breast + nodal areas
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