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Principles and Practice of Radiation Therapy

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Presentation on theme: "Principles and Practice of Radiation Therapy"— Presentation transcript:

1 Principles and Practice of Radiation Therapy
Chapter 23 Computed Tomography Simulation Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

2 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Historical Facts Godfrey Hounsfield First computed tomography (CT) unit Alan Cormack Developed math calculations or algorithms Shared the 1979 Nobel Prize Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

3 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
General Information CT simulator specific for therapy High-performance scanner Laser and patient marking system Virtual simulation Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

4 Principles of Operation
Gantry external controls Couch controls Gantry tilt Emergency off buttons Localizer lasers Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

5 Principles of Operation
Gantry internal controls Detector array X-ray tube Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

6 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Hounsfield Units Shades of gray Electron density of tissue Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

7 Benefits of CT Simulation
Outline critical structures Delineate target volume Achieve optimal beam placement Boost fields planned without patient present Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

8 Benefits of CT Simulation
Beam’s eye view Electronic field shaping Construction of digital reconstructed radiographs (DRRs) Calculation of dose distribution Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

9 Considerations and Limitations of CT Simulation
Bore size Width and shape of couch Laser system Acquisition/patient marking time Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

10 Considerations and Limitations of CT Simulation
CT numbers in dose inhomogeneity corrections Setup parameters and treatment accessories unable to be verified Must visualize entire contour Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

11 Simulation Procedures
Presimulation planning Machine limitations Immobilization Patient positioning Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

12 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Contrast Agents Medical history Oral Intravenous Intrathecal Intraarticular Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

13 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
CT Simulation Room preparation Explanation of procedure Patient positioning and immobilization Data acquisition Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

14 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
CT Simulation Target and normal tissue localization Virtual simulation of treatment fields Dose distribution Documenting data Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

15 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Image Quality Spatial resolution Image contrast Noise Dose Artifacts Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

16 CT Image Processing Controls
Window width Window level Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

17 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Quality Assurance AAPM Radiation Therapy Committee Task Group No. 66 Daily Warm-up and QA Monthly QA Yearly QA Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

18 Image Registration and Correlation or Fusion
Two sets of Images Scans overlaid Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.

19 Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.
Respiratory Gating Breathing motion artifacts Four-dimensional scanning Spirometer Maximum intensity projection (MIP) Copyright © 2010 by Mosby, Inc., an affiliate of Elsevier Inc.


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