L6- Principles of Isodose Planning (Simulation)

Simulation

Radiographic images acquisition

Simulation

Involves computer tomography scans or other imaging studies to help the radiation oncologist plan how to direct the radiation.

Simulation

Assist the physician and other members of the radiation therapy team in the treatment planning process by establishing the appropriate volume to be treated and identifying the normal structures within or adjacent to this volume.

Patient positioning and immobilization

are very significant parts of simulation

Simulation

Patient positioning and immobilization are very significant parts of this process as these will help with the treatment set-up and ensure that the radiation is directed properly each day. This process involves the radiation therapist

Positioning and Immobilization

Tattoo and Marker Placement

Imaging Studies

3 steps of Simulation

Conventional Simulators

Designed to simulate the mechanical, geometric and optical conditions of a variety of units

Conventional Simulators

During ___, patient data are obtained using fluoroscopy, radiography and physical measurements of the patient. This information is then entered into the treatment planning computer

Gantry, treatment couch and controls.

Conventional Simulators Mechanical components:

Gantry

Conventional Simulators: Parts

Rigid C-shaped structure which provides support for both the x-ray tube and film holder system/image intensifier

Isocenter

Conventional Simulators: Parts

✓ The gantry rotates around a fixed point known as the ___

Isocenter

It should be considered as the reference point in space

Isocenter

Generally, it is located 80 to 100 cm from the focal spot and between 100 and 130 cm above the floor

80-100cm

Isocenter is located ____ to ____ from the focal spot

100-130cm

Isocenter is located 80 to 100 cm from the focal spot and between ___ and ___ above the floor

Gantry

Conventional Simulators: Parts

provides stability for the different components of the gantry head.

Collimator assembly

Directs the path of the x-ray beam toward the patient after it emerges from the x-ray tube.

Optical Distance Indicator

Also called as optical range finder (ORF)

Optical Distance Indicator

Also called as range finder

Optical Distance Indicator

-Mounted near the collimator

Optical Distance Indicator

Projects a scale onto the patient’s skin which corresponds to the source skin distance (SSD)

Field Defining Wires

Also known as delineators

Field Defining Wires

Located in the collimator assembly

Field Defining Wires

-Made up of tungsten, Represents the edge of the treatment field

Beam Restricting Diaphragms

Also known as the x-ray shutters, blades or collimators

Beam Restricting Diaphragms

Also located within the collimator assembly

Beam Restricting Diaphragms

-Define both the size and the axis of the x-ray beam through restricting the coverage of the x-ray field

Beam Restricting Diaphragms

Indicate the coverage of the x-ray field.

Beam Restricting Diaphragms

Located at the opposite end of the gantry arm

Imaging/Image intensifier system

Receives and processes the created image

Film holder, Image intensifier, Television camera, Video monitor

Imaging/Image intensifier system four major components

Couchtop

Also known as patient tabletop.

Couchtop

The device in which a patient is positioned during treatment or simulation.

Couchtop

It is essential that the patient tabletop on the simulator provides support identical to that of the patient tabletop on the treatment unit to maintain reproducibility

Couchtop

The surface of the tabletopmust be a hard flat surface that minimally attenuates the x-ray beam

CT Simulators

provides the most useful information for treatment planning purposes because the scans can produce a 3D representation of the patient and external structures

CT Simulators

this simulator outlines the target volume and critical structures, projects treatment beams on to the patient and establishing external reference marks used for treatment setup purposes

gantry, couch and computer control system

major components of CT simulator

X-ray tubes, Detector array, High voltage generator, Mechanical support devices

CT Simulators: Parts

Gantry: The gantry includes the following components:

Treatment Couch

a flat, radiolucent, and often indexable tabletop attachment (usually carbon fiber) placed on a CT scanner couch to match the contour and indexing of a linear accelerator (LINAC) treatment table

Patient Positioning

it is one of the weakest link in treatment planning process

Stable, Comfortable, Minimizes movements, Reproducible

Good patient position is ALWAYS:

Immobilization devices

are medical tools used to stabilize, support, or restrict movement of a specific body part, ensuring precision during radiotherapy