Mammographic Equipment and Quality Control
What the exam tests
This domain covers mammography unit components, image acquisition, dose, and the quality control program required under MQSA. Candidates should connect equipment settings to image quality and patient dose.
Core concepts
- X-ray tube: molybdenum, rhodium, or tungsten targets; small focal spot (commonly 0.3 mm) for detail; filtration shapes the spectrum.
- Beam-shaping and scatter control: compression paddle, grid, and collimation.
- Exposure control: automatic exposure control (AEC) and manual technique; kVp affects contrast and dose.
- Detectors: screen-film, computed radiography, and direct digital systems; flat-field and artifact evaluation.
- Image quality metrics: contrast, spatial resolution, noise, signal-to-noise ratio, and contrast-to-noise ratio.
- Dose metrics: mean glandular dose (MGD) and exposure indicators such as EI/DI.
- QC program: phantom image, compression force, kVp, AEC performance, flat-field, artifact, dosimetry, repeat/reject analysis, monitor, and printer checks.
Traps
- Compression force testing targets 111 N (25 lb) minimum and 200 N (45 lb) maximum, not an arbitrary value.
- The phantom is typically 4 cm thick, 50% glandular/50% adipose; scoring evaluates fibers, specks, and masses.
- Higher kVp generally lowers dose but may reduce contrast.
- Magnification views increase dose and should not be used routinely.
- A grid improves contrast but increases dose.
Worked example / rule of thumb
If a unit's compression test produces only 90 N, it fails the minimum requirement; the test must demonstrate at least 111 N and not exceed 200 N. Rule of thumb: know the numeric QC limits, not just the names of the tests.