Radiographic Quality Control - Filtration, Collimation, Focal Spot, and Related QC Terms

Vocabulary flashcards covering key quality control concepts from the notes, including filtration (inherent, added, compensating), HVL, kVp calibration, focal spot measurement tools, collimation, protective apparel, and film illuminator maintenance.

Total filtration

The sum of inherent and added filtration in an X-ray system; minimum equivalent to 2.5 mm aluminum and evaluated annually or after changes to the X-ray tube or housing.

Half-Value Layer (HVL)

The thickness of material (aluminum) that reduces the X-ray beam intensity by 50%; used to specify filtration adequacy.

Minimum HVL (mm Al)

The required HVL in millimeters of aluminum for given kVp and waveform (e.g., 30 kVp to 130 kVp shows values for single-phase and three-phase/high-frequency).

Operating kilovolt peak (kVp)

The maximum tube voltage setting that determines beam energy and filtration requirements.

Single-phase

An electrical power waveform used in older X-ray systems; associated HVL values differ from three-phase/high-frequency.

Three-phase/high-frequency

Advanced power delivery waveforms that yield different HVL requirements compared with single-phase at the same kVp.

Inherent filtration

Filtration due to the X-ray tube glass/metal enclosure; typically around 0.5 mm Al and increases with tube aging.

Added filtration

An external aluminum sheet placed between the tube housing and collimator to increase HVL and improve beam quality.

Compensating filter

A filter (aluminum or plastic) used to equalize differences in subject radiopacity; examples include wedge, bilateral wedge, trough, and bow-tie filters.

Wedge filter

A compensating filter shaped like a wedge to balance exposure across varying subject densities.

Bow-tie filter

A compensating filter with a bow-tie shape used to equalize exposure, often in specialized imaging.

Collimator

A device that shapes and limits the X-ray beam; misalignment should not exceed 2% of SID.

PBL (Positive Beam Limitation) collimator

Automatic collimator that senses the image receptor size and adjusts shutters to fit; override mode allowed but beam should not exceed receptor size.

Collimator misalignment tolerance

Misalignment should not exceed 2% of the source-to-image distance (SID).

Focal spot size

Determines the system’s spatial resolution; measured annually or after X-ray tube replacement.

Pinhole camera

Measurement tool used to determine focal spot size.

Star pattern

Measurement tool used to determine focal spot size by projecting a star-shaped pattern.

Slit camera

Measurement tool used to determine focal spot size via a narrow slit method.

Line pair test tool

An alternative method to assess spatial resolution (line pairs per millimeter).

kVp calibration

Annual check of kVp accuracy; measured kVp should be within 10% of the indicated value.

Exposure time accuracy

Verification that the actual exposure time matches the indicated exposure time.

Protective apparel

Aprons, gloves, and gonadal shields; thermally inspected annually for cracks, tears, or holes; replace if damaged.

Viewbox illumination

Illuminator used for viewing radiographs; evaluated annually with a luminance meter; target brightness ≥1500 cd/m2 and variation ≤±10% across the surface.

Luminance meter

Instrument used to measure viewbox brightness to ensure proper illumination.

cd/m2

Candela per square meter; unit of luminance used to specify viewbox brightness.

Bulb replacement policy for illuminators

If a bulb is replaced, all bulbs in that illuminator should be replaced and matched to maintain uniform brightness.