Principles test 4 acceptance testing/qa
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86 Terms
What is the purpose of QA in radiation therapy?
QA ensures patient safety and quality of patient care.
What is required before installing a new LINAC in a clinic?
A Certificate of Need is required to install a new linear accelerator.
What is acceptance testing?
Acceptance testing verifies that a newly installed LINAC meets manufacturer and regulatory specifications before clinical use.
When is acceptance testing performed relative to commissioning?
Acceptance testing is performed before commissioning.
What is commissioning in radiation therapy?
Commissioning is the process of connecting and validating the software, hardware, and treatment planning system so the LINAC can be used clinically.
Why is commissioning necessary?
Commissioning ensures the treatment planning system accurately models the radiation beam before patient treatments begin.
What is coincidence testing in LINAC QA?
Coincidence testing verifies alignment between the radiation beam, light field, and mechanical indicators.
What components are checked during light and field alignment tests?
Collimator axis, light beam alignment, and crosshair alignment.
How many isocenters are evaluated in LINAC geometry?
Two isocenters are evaluated: the mechanical isocenter and the radiation isocenter.
What is the mechanical isocenter?
The mechanical isocenter is the point around which the gantry and collimator rotate.
What is the radiation isocenter?
The radiation isocenter is the intersection point of the colli, gantry and table
What is the split field test also called?
The split field test is also called the multiple beam alignment check.
What is the purpose of the split field test?
The split field test checks alignment of opposing radiation beams.
How is the split field test performed?
The split field test is performed using beams 180 degrees apart.
What device is checked during an MLC test?
The multileaf collimator is evaluated.
What parameters are evaluated in an MLC check?
Leaf drop speed, leaf transmission, leakage, and field shaping accuracy.
What is MLC leaf transmission?
MLC leaf transmission is the amount of radiation passing through the leaves when they are closed.
What is MLC leakage?
MLC leakage is unwanted radiation escaping between or around the MLC leaves.
What is MLC field shaping?
Field shaping is the ability of the MLC leaves to conform the radiation beam to the tumor shape.
Where is MLC symmetry commonly checked?
MLC symmetry is commonly checked at Dmax.
What does Dmax represent?
Dmax is the depth where maximum dose occurs in a radiation beam.
At what approximate depth is Dmax sometimes checked during QA measurements?
Approximately 10 cm depth may be used for some QA symmetry checks.
What is the tolerance for gantry and collimator angle accuracy?
The tolerance for gantry and collimator angle accuracy is about 1 degree.
What level of dose error must be reported to the NRC?
A misadministration must be reported if the delivered dose differs by 10 percent or more.
Why does each LINAC have its own dose rate?
Each LINAC has a unique calibrated dose rate due to machine-specific radiation output characteristics.
Can two LINACs of the same model have different dose rates?
Yes, even LINACs of the same model can have different calibrated dose rates.
What is included in acceptance testing for a LINAC?
Radiation survey, jaw symmetry check, light field coincidence check, mechanical isocenter check, radiation isocenter check, split field test, MLC check, x-ray beam performance check, electron beam performance check, monitor chamber check, wedges check, and miscellaneous checks.
What does a radiation survey verify?
A radiation survey verifies leakage radiation levels are within regulatory limits.
What does the jaw symmetry test evaluate?
The jaw symmetry test evaluates whether opposing jaws produce symmetrical radiation fields.
What does the light field coincidence test evaluate?
It evaluates whether the light field matches the radiation field.
What does the mechanical isocenter check verify?
It verifies that the gantry and collimator rotate around a consistent mechanical point.
What does the radiation isocenter check verify?
It verifies that radiation beams intersect at the same point in space.
What does the monitor chamber check verify?
It verifies the accuracy and stability of the LINAC dose monitoring system.
What do x-ray beam performance checks evaluate?
X-ray beam performance checks evaluate beam energy, output consistency, and beam profile.
What do electron beam performance checks evaluate?
Electron beam performance checks evaluate electron energy, output, and field characteristics.
What are wedges checked for during acceptance testing?
Wedges are checked for correct dose distribution and wedge factor accuracy.
What is workload in radiation shielding calculations?
Workload is the amount of radiation delivered by a LINAC in one week, usually expressed in Gy per week at 1 meter.
Why is workload important in shielding design?
Workload helps determine the required thickness of radiation shielding barriers.
What is the use factor in shielding calculations?
The use factor is the fraction of time the primary beam is directed toward a particular barrier.
What does the use factor help determine?
It helps determine shielding requirements for different walls of the treatment room.
What is the occupancy factor in shielding calculations?
The occupancy factor represents how often a space beyond a barrier is occupied by people.
Why is the occupancy factor important in shielding design?
It helps determine how much radiation shielding is required to protect people in adjacent areas.
What method is used to check both mechanical and radiation isocenter?
The star shot method is used.
