wk5b quality control

Vocabulary-style flashcards covering Quality Control (QC) and Quality Assurance (QA) protocols for dose calibrators, gamma cameras, SPECT/CT, and PET systems based on the MRSC1350 lecture.

Quality Control (QC)

Routine assessments of equipment performance designed to detect changes from a baseline condition and ensure findings originate in the patient rather than the equipment.

Quality Assurance (QA)

A planning and documentation process focused on sets of guidelines to ensure all procedures are appropriate, images contain necessary clinical information, and patient radiation exposure is minimized.

Constancy Check

A daily dose calibrator test performed using a long-lived radioactive source, typically $^{137}Cs$, to ensure readings remain stable from day to day across all clinical radionuclide settings.

Accuracy Check

A yearly assessment of the dose calibrator to verify the accuracy of the activity readings.

Zero Adjustment

A daily dose calibrator check to ensure the readout displays $0$ when no activity is present.

Point Source

A source, typically $10-20\,MBq$ of $^{99m}Tc$, positioned at least $4 \times$ the diameter of the crystal away from the detector to provide a uniform signal.

Sheet Source

A solid source containing a long-lived radionuclide, such as $^{57}Co$ ($T_{1/2}$ of $271\, ext{days}$, $120\,keV$ gamma), used for gamma camera QC.

Flood Tank

A Perspex tank filled with water and approximately $500\,MBq$ of $^{99m}Tc$ that must be mixed thoroughly to remove air bubbles before use.

Photopeak Setting

A daily check to verify that the camera's energy window coincides with the actual photopeak of the radionuclide, preventing degradation of uniformity and sensitivity.

Uniformity (Daily Flood)

A daily visual and quantitative check to ensure the detector response to uniform irradiation is consistent within defined limits.

Intrinsic Uniformity

A uniformity check performed with the collimator removed, usually using a point source of approximately $18\,MBq$.

Extrinsic Uniformity

A uniformity check performed with the collimator on, utilizing either a sheet source or a flood tank.

High Count Flood

A weekly or monthly uniformity scan of $50-100\, ext{million}$ counts used to provide correction data and prevent ring artifacts in SPECT images.

Ring Artefact

Concentric rings of alternating high and low count densities in transaxial images caused by insufficient camera uniformity or COR misalignment.

Centre of Rotation (COR)

The single point around which detectors rotate; alignment between the electronic COR and mechanical COR is critical to prevent image distortion and loss of resolution.

Spatial Resolution

The ability of a system to accurately depict two separate events in space as distinct sources; can be measured using a quadrant bar phantom.

Quadrant Bar Phantom

A device divided into four sections with lead strips at different spacings, used to detect long-term deterioration of spatial resolution.

Linearity

The ability of the camera to accurately determine photon position without displacement, ensuring a straight-line source yields a straight line in the resulting image.

Blank Scan

A PET camera QC check used to identify evidence of defective detectors.

Tube Conditioning (Warm-up)

A CT component QC procedure that prevents tube cracking and electrical arcing.

Air Calibration

An automatic CT function check to ensure the response to X-ray flux is uniform among all detectors.

CT Number Quality Control

A performance check using a water-filled phantom to verify the accuracy of the CT number for water and calculate noise.