Quality Assurance & Control Flashcards
7 cards from real CMD practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Quality Assurance & Control flashcards as text
The TG-119 report provides acceptance criteria for IMRT commissioning. What is the recommended action if an institution's IMRT QA results consistently fall below TG-119 benchmarks?
Answer: Investigate and resolve systematic errors in the treatment planning or delivery process
Consistently failing TG-119 benchmarks indicates systematic errors in the IMRT process that must be identified and corrected before clinical use.
Which parameter is measured by the 'garden fence' or 'picket fence' test and what tolerance is typically applied?
Answer: MLC leaf positional accuracy; tolerance of 1 mm per leaf
The picket fence test evaluates MLC leaf positional accuracy, with a typical clinical tolerance of 1 mm deviation per leaf from the intended position.
During a CT simulator QA, the Hounsfield unit (HU) for water measures -15 HU instead of 0 HU. What is the MOST significant clinical consequence if uncorrected?
Answer: Dose calculation accuracy will be compromised due to incorrect electron density assignment
HU values are directly converted to electron density for dose calculations; a systematic HU offset will cause incorrect electron density assignments, leading to dose calculation errors.
According to AAPM TG-100, what methodology is used to identify and prioritize failure modes in radiation therapy QA programs?
Answer: Failure mode and effects analysis (FMEA)
TG-100 recommends using failure mode and effects analysis (FMEA) to proactively identify potential failure modes, assess their risk priority numbers, and design QA programs accordingly.
A 4D-CT scan is acquired for a lung SBRT patient. Which QA procedure should be performed on the 4D-CT system to ensure accurate motion characterization?
Answer: Validation of phase binning accuracy using a motion phantom
A motion phantom with known, reproducible motion patterns verifies that the 4D-CT system correctly bins projection data into respiratory phases for accurate motion characterization.
What is the purpose of performing output constancy checks using a solid water phantom and reference ionization chamber on a daily basis?
Answer: To detect day-to-day variations in beam output before patient treatments
Daily output constancy checks detect short-term fluctuations in machine output relative to a baseline, allowing identification of problems before patients are treated.
In volumetric modulated arc therapy (VMAT), which QA metric specifically tests the synchronization between gantry rotation speed, dose rate, and MLC position?
Answer: Trajectory log analysis
Trajectory log files recorded by the linac capture gantry angle, dose rate, and MLC positions as a function of time, allowing verification of their synchronization during VMAT delivery.