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
When performing annual QA on a multileaf collimator (MLC), which test specifically evaluates leaf position accuracy under dynamic conditions?
Answer: Picket fence test
The picket fence test uses a series of narrow, sequential MLC-defined fields to expose film or an EPID, revealing individual leaf positioning errors under dynamic movement.
According to TG-40, how frequently should beam flatness and symmetry be measured for a clinical linear accelerator?
Answer: Monthly
TG-40 recommends monthly measurements of beam flatness and symmetry for clinical linear accelerators as part of standard QA protocols.
A radiation therapy department uses IMRT for head and neck treatments. Per TG-142, what is the recommended tolerance for IMRT patient-specific QA gamma analysis (3%/3mm)?
Answer: Greater than 95% of points passing
TG-142 recommends that IMRT patient-specific QA should achieve greater than 95% of points passing using a 3%/3mm gamma criterion.
During a brachytherapy source calibration, the measured air kerma strength deviates by 6% from the vendor-stated value. What is the appropriate action per TG-56?
Answer: Use the measured value and notify the vendor
TG-56 states that if the measured source strength deviates by more than 5% from the vendor certificate, the measured value should be used and the discrepancy reported to the vendor.
What physical quantity is directly measured by a well-type ionization chamber used in brachytherapy source calibration?
Answer: Air kerma rate
A well-type chamber calibrated with a NIST-traceable standard measures air kerma rate, which is then used to determine air kerma strength (SK) for brachytherapy sources.
Which QA procedure verifies that a treatment plan correctly accounts for tissue heterogeneity in the presence of lung tissue?
Answer: End-to-end test using an anthropomorphic heterogeneous phantom
An end-to-end test using an anthropomorphic phantom with tissue-equivalent lung inserts verifies the complete chain from imaging through dose calculation and delivery in realistic heterogeneous conditions.
A dosimetrist reviews a prostate IMRT plan and notices the rectal V70Gy constraint of 20% is exceeded. Which plan modification is MOST appropriate to address this?
Answer: Add a rectal avoidance structure and re-optimize with tighter rectal constraints
Adding a dedicated rectal avoidance structure with tighter optimization constraints allows the optimizer to better spare the rectum while maintaining target coverage.