An Overview of CSUVTH Imaging for Radiotherapy

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An Overview of CSU/VTH Imaging for Radiotherapy

• J. Fred Harmon, Ph.D. DABR
• January 28, 2008

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The Problem

• Escalate dose to tumor
• Limit dose to critical structures

Tumor
Cord
Set-up Error Margin
Axial CT Slice
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Solution
?

• Target Identification characterization
• CT
• MRI PET
• Generate and custom 3-D absorbed dose
  distribution
• Radiation Mode (Photons Vs Electrons)
• Radiation Energy
• Fields Field Orientation
• Field Shaping
• Field Intensity Modulation
• Accurate Dose calculation
• Accurate precise targeting
• Patient Immobilization
• On-board Imaging

OAR
Fusion often helpful
CT HUs
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Typical Clinical LINAC Design

• ? 3000 MHz
• 10 cm
• P 5 MWPeak

Karzmark and Morton, A primer on Theory and
Operation of Linear Accelerators in Radiation
Therapy
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Varian Trilogy Radiation Beam Characteristics

• Wide range of treatment energies
• Photon (6 10 MV)
• Electron (4, 6, 9, 12, 15, 18 MeV)
• Multi-leaf collimator system
• Field shaping
• Intensity Modulated Radiation Therapy
• Radiosurgery

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Sliding Window IMRT Example (DMLC)
June 2003 AAPM IMRT Summer School
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Trilogy Radiation Beam Targeting

• Improved mechanical isocenter accuracy
• Improved patient positioning (indexing)
• Digital planar imaging
• Megavoltage (MV)
• Kilovoltage (kV)
• Cone beam CT
• Kilovoltage (kV)

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Design Evaluation of Patient Immobilization
Devices
Derek Van Uffelen Freshman Scholar
Mr Gator
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Examples of Patient Immobilization
Simulation
Treatment
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Megavoltage Imaging (6 MV)

• AS1000 Imager (Indirect Technology)
• 30 cm x 40 cm imaging area
• 768 x 1024 pixel (0.39 mm pixel size)

Copper Plate
(Gadolinium Oxysulfide)
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Kilovoltage Imaging Planar

• PaxScan 4030CB Imager (Indirect Technology)
• 30 cm x 40 cm imaging area
• 1536 x 2048 pixel (0.20 mm pixel size)
• CsI scintillator
• 101 scatter grid

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• Planar kV Imager Features
• Pulsed fluoro w/ABC
• Single exposure
• Double exposure w/ two technique factors

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Kilovoltage Imaging Cone Beam CT
Traditional Fan Beam CT

• Matrix 128x128, 256x256, 512x512
• FOV
• 24 cm dia x 15 cm length
• 45 cm dia x 14 cm length
• Slice thickness 1 10 mm
• One rotation about patient

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Example of CBCT
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Investigation of Tumor Interfraction Response
Utilizing Cone beam CT

• Dynamic Adaptive Radiotherapy (DART) permits
  modification of Tx plan as needed DURING course
  of treatment
• What tumor types are most suitable?
• How frequent will the changes need to be made?
• How can we make the changes efficiently?

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Investigation of Tumor Interfraction Response
Utilizing Cone beam CT

• Variety of patients will be selected for study
• Each patient will have multiple CBCTs throughout
  course of treatment
• Tumor will be contoured on each CBCT
• Tumor volume will be tracked
• Comparison of original plan Vs impact of
  interfraction plan changes

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Soon to be ImplementedRespiratory Gating
PET/CT Fusion

• Gating system tracks breathing cycle
• Irradiates target only during selected portion
  (phase) of breathing cycle
• Correlation between tumor motion and box obtained
  during gated CT simulation
• Permits reduction in volume of healthy tissue
  irradiated
• Requires multi-slice CT w/gating software (PET/CT
  purchase pending)