1. Principles and Practice of Radiation Therapy
Chapter 22
Conventional (Fluoroscopy-Based) Simulation Procedures
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Key Terms
Simulation: The precise mockup of a patient treatment with radiographic documentation of the treatment portals in a one- or two-step process
Localization: Defining the position and the extent of the tumor and anatomic structures by reference of surface marks; sometimes the second step of the simulation process
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3. Radiation Therapy Volumes
Gross tumor volume (GTV): Gross palpable or visible tumor
Clinical target volume (CTV): Gross palpable or visible tumor and surrounding volume of tissue that may contain subclinical or microscopic disease
Planning target volume (PTV): Indicates the CTV plus margins for geometric uncertainties such as patient motion, beam penumbra, and treatment setup differences
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Simulation Acronyms AP
CA, CAX
Film/radiograph
IFD
LAO/LPO
RAO/RPO
POP
Couch/table
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Simulation Acronyms
ODI
SAD
SCD/SDD
SFD
SSD
TSD
TTH
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6. Isocentric Technique Example #1
A patient is treated to midplane on the 6-MV linear acclerator. The source-skin distance (SSD) reads out at 89 cm from the anterior. What is the patient’s innerfield distance (IFD)?
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7. Isocentric Technique Example #2
A patient measures 15 cm through the lateral aspect of his head. What will the SSD be for an isocentric setup using 100-cm SSD?
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8. Isocentric Technique Example #3
An abdominal tumor is located 9 cm from the anterior surface. What are the anterior and posterior SSDs for this isocenter placed in the middle of the tumor (IFD = 20 cm)?
Treatment at 100 cm SSD
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Body Planes
Transverse (axial)
Coronal
Sagittal
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10. Body Plane Radiographic Example
Label the directional terms (anterior, posterior, superior, inferior, right, and left)
Which body plane is represented?
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11. Radiation Oncology Process
Diagnosis
Consultation
Simulation and treatment planning
Treatment
Patient follow-up
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12. Historical Perspective
Radiology related
Treatment planning on treatment unit
Topographic anatomy and physiology
Poor-quality films
Treatment time used
Fluoroscopy related
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13. Four Developments in Radiation Treatment Planning in the 1990s
Virtual simulation was introduced.
CT images on a conventional simulator were improved.
Treatment planning computers were developed that could carry out three-dimensional treatment planning.
Virtual simulator provided the ability to generate high-resolution digital reconstructed radiographs (DRRs).
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14. Simulation and Treatment Planning
Conventional simulation
Beam design/placement
Determination of external contours
CT simulation
Patient marking
Transfer of plan to marks on patient
Treatment verification
Confirmation of shields/multileaf collimator (MLC)
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SSD/SAD Localization
Source-skin distance (SSD)
This approach positions a fixed treatment distance of 80 or 100 cm on the patient’s skin for each field.
Source-axis distance (SAD)
Also called the isocentric technique, it provides tumor localization in three dimensions, using an isocenter placed within the target volume.
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16. Conventional Simulation Procedure
Presimulation plan
Room preparation
Explanation of procedure
Patient positioning and immobilization
Operation of simulator controls
Setting field size parameters
Exposure factors
Radiographic exposure and image processing
Documenting data
Final procedures
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Contour Devices
Definition
Manual methods
Solder wire
Thermoplastic tube
Plaster CT
Examples
Benefits
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18. Treatment Verification
Overview
Verification simulation
“Part B”
Imaging
Changes
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Emergency Procedures
Treatment related
Spinal cord compression
Excessive bleeding
Obstruction
Other
Medical emergencies
Cardiopulmonary resuscitation (CPR)
Obstructed airway
Anaphylactic shock
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