Treatment Delivery Equipment Flashcards
What does Linac stand for?
Linac stands for Linear Accelerator, which is used to deliver external beam radiation therapy (EBRT).
How is radiation generated in a Linac?
Radiation is generated artificially through electricity, and no radioactive material is involved.
What types of radiation can a Linac deliver?
A Linac can deliver both electrons and photons for cancer treatment.
What is the most common treatment energy used in Linac for IMRT and MLCs?
The most common energy for treatment is 6 MV.
What are MLCs, and what do they do?
MLCs (Multi-Leaf Collimators) are used to shape radiation fields, allowing for both static and dynamic field shaping.
52-160 leaves
located below secondary collimation.
The computer driven, heavy, metal collimator rods slide into place to form field shape.
MLCs can move during treatment.
What are the three common Linac treatment options?
IMRT (Intensity-Modulated Radiation Therapy)
VMAT (Volumetric Modulated Arc Therapy)
SRS/SBRT (Stereotactic Radiosurgery/Radiotherapy).
What is the purpose of the collimator on a Linac?
The collimator shapes the radiation beam by controlling the X and Y jaws, allowing for both square and complex field shapes.
What does SSD stand for, and how is it used in Linac treatments?
SSD (Source to Skin Distance) refers to the distance from the radiation source to the patient’s skin, crucial for determining treatment geometry.
What is the treatment head on a Linac?
The treatment head contains the equipment that shapes and delivers the radiation beam, and it rotates around the patient to target the tumor.
What does PSA stand for in Linac terminology?
PSA (Patient Support Assembly) is another term for the treatment couch or table, used to position the patient during treatment.
How many pounds can the treatment couch support, and what is it made of?
How does the gantry move on a Linac?
The gantry rotates clockwise and counterclockwise around the patient, typically moving 360 degrees but cannot move significantly past 180 degrees. 0 (zero) degrees is at the top and 180
degrees is at the bottom
What does the portal imager (MV imager) do?
The portal imager captures megavoltage (MV) images, which are used to verify patient positioning and treatment accuracy.
What is CBCT, and how is it used in Linac treatments?
CBCT (Cone-Beam Computed Tomography) is used to generate 3D images of the patient’s treatment area, improving precision.
What function does the light field serve during Linac treatments?
The light field is projected from the treatment head, showing the size and shape of the radiation field on the patient’s skin.
What are the two main types of Linac hand controls?
The hand pendant controls gantry and table movement, while the control console manages imaging and treatment functions.
How are Linac table controls activated?
Controls on both sides of the table allow the following functions:
* Motion Enable – Used in conjunction with other switches
(Dead Man’s Switch – NEVER USE THIS TERM)
* Vertical, long, lateral, rotation (Used with motion enable)
* Field Light
* ODI (SSD)
* Room lights
* Test/Reset
* Emergency Stop (Not your first choice to stop the machine)
How are the Hand Pendant controls activated?
Most commonly used functions:
* Note: Squeeze enable switches to activate other
functions
* Table movement – Vertical, long, lateral, rotation
* Room lights, field light, ODI (SSD)
* Gantry movement – clockwise and counterclockwise
* Collimator - clockwise and counterclockwise
* Setting field size by adjusting X and Y jaws
What are some of the emergency safety features in a Linac room?
Safety features include emergency stop buttons, door interlocks, and warning lights indicating radiation is active.
What are some modern linear accelerator models?
Models include Varian TrueBeam, CyberKnife, Elekta Synergy, the MR-Linac, and the Varian Halcyon.
3rd generation models
What is the function of the Dead Man’s Switch in Linac operations?
The Motion Enable switch (referred to as the Dead Man’s Switch, but this term should never be used in a clinic) activates table or gantry movement only while it is being held down.
How does the collimator move during a Linac treatment?
The collimator can rotate both clockwise and counterclockwise to further customize the shape of the radiation beam.
What are the components displayed on the control console monitors?
- Top Center Monitor: Visual on Patient
- Left Monitor: Linac Functions
- Middle Monitor: Treatment Plan
- Right Monitor: Imaging System
- Upper Control Panel: Visual controls
- Lower Control Panel: Operates
functions on the three main Linac
monitors - Possibly Missing: OBI controller
- Not Shown: Charting computer
What happens if the Linac vault door opens during a treatment session?
Door interlocks will automatically turn off the radiation beam if the vault door is opened during treatment.
What does the term “iso-centric treatment” mean?
In an iso-centric treatment, the tumor is placed at the isocenter of the radiation field, and the gantry rotates around this fixed point.
What is the key difference between SSD and isocentric treatments?
In SSD treatments, the distance from the source to the skin surface changes with gantry angle, whereas in isocentric treatments, the distance remains constant (100 cm) because the isocenter is fixed.
What is a Varian Halcyon unit used for?
The Varian Halcyon unit delivers slice therapy, offering more precise radiation by targeting thin slices of tissue, often used for highly localized treatments.
Primary Collimator
What is the purpose of secondary collimators in a Linac?
Secondary collimators work in conjunction with MLCs to refine the radiation beam, shaping it for more accurate targeting of the treatment area.
Control by using the setting knobs at the collimator head or pendant to adjust the upper and lower collimator jaws.
MLCs or Cerrobend blocking may further define field.
What safety protocol is associated with the Emergency Stop button on a Linac?
The Emergency Stop button immediately cuts all power to the Linac and halts treatment, but it should only be used in true emergencies, as it may affect machine calibration.
What is the difference between kilovoltage (KV) and megavoltage (MV) imaging?
KV imaging is typically used for imaging and verification BEFORE treatment
MV imaging is used for verifying treatment delivery DURING high-energy radiation sessions.
How is the table (PSA) moved during treatment?
- PSA, PTA, Couch, and Table are
all synonyms - Older tables only have longitude,
lateral, vertical, and limited 90-
degree rotation - Newer tables also have pitch,
roll, and added rotational
movement
What are the major internal components of a linear accelerator?
Modulator cabinet
*houses power supply
The drive stand that
houses the klysrton, cooling
water system, the circulator,
waveguide
The Gantry houses:
*waveguide/accelerator
structure
*electron gun
*pressure system
*Vacuum system
*magnet & treatment head
components
Control console-controls the treatment couch
Klystron
Circulator
Waveguide
Hollow tube like structure, conveys the microwave power to the accelerator structure in the gantry.
Water cooling system
Gantry
Beam flattening filter
Scattering Foils
Dual Ion Chambers
What is the modulator cabinet in a Linac?
How are bending magnets used in a Linac?
Bending magnets are used to direct the electron beam within the Linac. The most common configuration is 270 degrees(most popular), but they can also be 90 degrees or 112.5 degrees (slalom bending).
What is the purpose of dynamic or virtual wedges in modern Linacs?
Dynamic (virtual) wedges use MLCs and collimators to electronically adjust the radiation dose, replacing the need for physical metal wedges.
What are manual or physical wedges, and how are they used in treatment?
Manual Wedges are angled or slopped pieces of metal that attach to the head of the machine.
Wedges change the dose distribution of the radiation beam. The thick end allows less radiation to pass through, than the thin end.
Their common purpose is to adjust or flatten the dose when dealing with slopped skin surfaces or with the body due to tissue sensitivity.
Typical wedge angles are 15, 30, 45, and 60.
Physical wedges are becoming dated technology, due to dynamic or virtual wedging as a result of MLC’s and Jaws (aka collimators)
What is a “beam’s eye view” in radiation therapy?
Beam’s eye view refers to how the radiation beam sees the patient and the treatment field from the perspective of the radiation source.
What is a bird’s eye view in the context of Linac imaging?
Bird’s eye view refers to the top-down view of the treatment field, showing the alignment and positioning of the patient.
What is the function of the control console in a linear accelerator?
The control console manages the functions of the Linac, including treatment settings, patient monitoring, and imaging systems.
What are the five major sections of a modern linear accelerator?
1)Gantry
2)Gantry stand (drive stand)
3)Modulator cabinet
4)Patient support assembly (PSA)
5)Control console
What is a cerrobend block, and what is it used for?
What is Cerrobend made of? BLTwcheese
Cerrobend blocks are made from a metal alloy used to shape electron radiation beams for custom treatment fields
Cerrobend (also known as Lipowitz Metal) is composed of:
Bismuth (50%)
Lead (27%)
Tin (13%)
Cadmium (10%)
This form of radiation treatment has been available since 2003 and is sometimes referred to as “slice therapy”. It is considered the next evolution of IMRT and advanced imaging capabilities according to Principles and Practice of Radiation Therapy. It is essentially a linear accelerator and a computed tomography (CT) unit combined. This form of radiation treatment is commonly called what?
TomoTherapy
What is the latest, meaning most current, generation of linear accelerators listed in chapter 7 of the Principles and Practice of Radiation Therapy?
Third-Generation Accelerators
Horshoe
Accessory if you’re gonna treat electrons
Cone that what goes into
Cerramend blocks
Pizza pie
Angle of table/gantry
Everything control monitor will tell you
Not regularly used
You are treating on a standard Varian linac. This is your first day at this office, but the patient is halfway through 6 weeks of treatment. You are treating the patient’s left breast cancer with two parallel opposed tangential fields (the blue and green beams on the first image - ignore the red beam). As you rotate the gantry from the green to the blue beam position, you realize the gantry head will not clear the patient’s elbow. You stop because if you continue as is, you will hit the patient. What are your options for moving to the next treatment field (blue) without hitting the patient?
B: Unlock the table and shift it a few centimeters to the patient’s right. Then put it back in the same position based on the screen table coordinates.
C: Move the table LONG to clear the patient’s elbow. You noted the table coordinates and return the table to the same position after the gantry clears.
Both of these options are acceptable
