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Principles and Practice of Principles and Practice of Radiation TherapyRadiation Therapy
Chapter 23Chapter 23
Computed Tomography Computed Tomography SimulationSimulation
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 22
Historical FactsHistorical Facts
Godfrey HounsfieldGodfrey Hounsfield First computed tomography (CT) unit First computed tomography (CT) unit
Alan Cormack Alan Cormack Developed math calculations or algorithmsDeveloped math calculations or algorithms
Shared the 1979 Nobel PrizeShared the 1979 Nobel Prize
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 33
General InformationGeneral Information
CT simulator specific for therapyCT simulator specific for therapy High-performance scannerHigh-performance scanner Laser and patient marking systemLaser and patient marking system Virtual simulationVirtual simulation
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 44
Principles of OperationPrinciples of Operation
Gantry external controlsGantry external controls Couch controlsCouch controls Gantry tiltGantry tilt Emergency off buttonsEmergency off buttons Localizer lasersLocalizer lasers
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 55
Principles of OperationPrinciples of Operation
Gantry internal Gantry internal controlscontrols Detector arrayDetector array X-ray tubeX-ray tube
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 66
Hounsfield UnitsHounsfield Units
Shades of grayShades of gray Electron density of Electron density of
tissuetissue
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 77
Benefits of CT SimulationBenefits of CT Simulation
Outline critical structuresOutline critical structures Delineate target volumeDelineate target volume Achieve optimal beam placementAchieve optimal beam placement Boost fields planned without patient present Boost fields planned without patient present
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 88
Benefits of CT SimulationBenefits of CT Simulation
Beam’s eye viewBeam’s eye view Electronic field shapingElectronic field shaping Construction of digital reconstructed Construction of digital reconstructed
radiographs (DRRs)radiographs (DRRs) Calculation of dose distributionCalculation of dose distribution
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 99
Considerations and Limitations of Considerations and Limitations of CT SimulationCT Simulation
Bore sizeBore size Width and shape of couchWidth and shape of couch Laser systemLaser system Acquisition/patient marking timeAcquisition/patient marking time
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1010
Considerations and Limitations of Considerations and Limitations of CT SimulationCT Simulation
CT numbers in dose inhomogeneity CT numbers in dose inhomogeneity correctionscorrections
Setup parameters and treatment accessories Setup parameters and treatment accessories unable to be verifiedunable to be verified
Must visualize entire contourMust visualize entire contour
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1111
Simulation ProceduresSimulation Procedures
Presimulation planningPresimulation planning Machine limitationsMachine limitations
• ImmobilizationImmobilization
• Patient positioningPatient positioning
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1212
Contrast AgentsContrast Agents
Medical historyMedical history Oral Oral IntravenousIntravenous IntrathecalIntrathecal IntraarticularIntraarticular
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1313
CT SimulationCT Simulation
Room preparationRoom preparation Explanation of Explanation of
procedureprocedure Patient positioning Patient positioning
and immobilizationand immobilization Data acquisitionData acquisition
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1414
CT SimulationCT Simulation
Target and Target and normal tissue normal tissue localizationlocalization
Virtual simulation Virtual simulation of treatment of treatment fieldsfields
Dose distributionDose distribution Documenting Documenting
datadata
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1515
Image QualityImage Quality
Spatial Spatial resolutionresolution
Image Image contrastcontrast
NoiseNoise DoseDose ArtifactsArtifacts
Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc. 1616
CT Image Processing Controls CT Image Processing Controls
Window widthWindow width Window levelWindow level
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Quality AssuranceQuality Assurance
AAPM Radiation Therapy Committee Task AAPM Radiation Therapy Committee Task Group No. 66Group No. 66
Daily Warm-up and QADaily Warm-up and QA Monthly QAMonthly QA Yearly QAYearly QA
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Image Registration and Correlation Image Registration and Correlation or Fusionor Fusion
Two sets of ImagesTwo sets of Images Scans overlaidScans overlaid
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Respiratory GatingRespiratory Gating
Breathing motion Breathing motion artifactsartifacts
Four-dimensional Four-dimensional scanningscanning
SpirometerSpirometer Maximum intensity Maximum intensity
projection (MIP)projection (MIP)