ABR Quality Assurance and Quality Control 2

Question 1

The gamma (γ) index used in IMRT patient-specific QA combines which two criteria?

Accepted Answer

Dose difference and distance-to-agreement

Answer

Dose rate and monitor unit accuracy

Answer

Beam energy and field size

Answer

Flatness and symmetry

Question 2

AAPM TG-119 was developed primarily to establish:

Accepted Answer

Commissioning benchmarks and test cases for IMRT planning and delivery

Answer

QA protocols for CT simulators

Answer

Acceptance testing procedures for new linear accelerators

Answer

Dosimetry standards for brachytherapy sources

Question 3

Which AAPM report provides QA guidelines specifically for CT simulators used in radiation therapy?

Accepted Answer

TG-66

Answer

TG-142

Answer

TG-40

Answer

TG-51

Question 4

An EPID (Electronic Portal Imaging Device) is most commonly used in linac QA for:

Accepted Answer

Patient position verification and transit dosimetry

Answer

Absolute dose calibration at isocenter

Answer

Measuring electron beam percent depth dose

Answer

Commissioning photon beam energy

Question 5

What is the recommended passing criteria (gamma pass rate) for patient-specific IMRT QA according to AAPM TG-218?

Accepted Answer

95% of points with γ(3%/3mm) ≤1

Answer

90% of points with γ(3%/3mm) ≤1

Answer

95% of points with γ(2%/2mm) ≤1

Answer

99% of points with γ(5%/5mm) ≤1

Question 6

Machine-Specific Reference Fields (MSRF) are used in small-field dosimetry primarily because:

Accepted Answer

Standard 10×10 cm² fields cannot be produced by some small-field devices like CyberKnife or MRI-linacs

Answer

They allow direct comparison between institutions without corrections

Answer

They eliminate the need for ionization chamber measurements

Answer

They define the calibration field for all electron beams

Question 7

Which detector type is generally preferred for small-field dosimetry (fields < 3×3 cm²) due to its small sensitive volume and minimal perturbation?

Accepted Answer

Diode or diamond detector

Answer

Farmer-type ionization chamber

Answer

Large parallel-plate chamber

Answer

Thermoluminescent dosimeter (TLD) powder