Quality Control & Equipment Assurance Flashcards

Center of rotation (COR) calibration in SPECT imaging is performed to:

Answer: Ensure the mechanical rotation center and the electronic center of the projection data are aligned

A COR offset causes the projection data to be misregistered during backprojection, producing ring or 'bull's-eye' artifacts in reconstructed SPECT images.

How frequently should SPECT center of rotation calibration be performed under standard nuclear cardiology QC protocols?

Answer: Weekly

Weekly COR calibration is the standard recommendation from ASNC and SNM guidelines, or whenever camera service has been performed, to detect mechanical drift before it affects clinical studies.

The recommended energy window for Tc-99m myocardial perfusion SPECT imaging is:

Answer: 20% symmetric window centered at 140 keV

A 20% symmetric window (126–154 keV) centered on the 140 keV photopeak of Tc-99m provides the optimal balance between true-event acceptance and scatter rejection.

Dead time in nuclear medicine instrumentation refers to:

Answer: The period after a detected event during which the system cannot register additional events

During dead time, the detection electronics are busy processing a pulse and are unable to detect another incoming photon, leading to count loss at high activity levels.

The multi-window spatial registration test evaluates whether:

Answer: Multiple energy peaks from different radionuclides are spatially co-registered on the detector

Multi-window spatial registration verifies that images acquired at different energy peaks (e.g., Tl-201's 70 and 167 keV peaks) are spatially aligned, preventing artifactual misregistration in dual-isotope protocols.

Gamma camera system sensitivity is typically expressed as:

Answer: Counts per second per megabecquerel (cps/MBq) or counts per minute per microcurie (cpm/µCi)

Sensitivity describes the detection efficiency of the system — how many counts are recorded per unit of radioactivity — which directly affects how much activity is needed to achieve adequate image statistics.

A SPECT uniformity correction flood is acquired to:

Answer: Generate a pixel-by-pixel correction matrix that compensates for non-uniformities during tomographic reconstruction

Non-uniformities that are minor in planar imaging become amplified during SPECT backprojection into ring artifacts; a high-count flood correction map normalizes sensitivity across all pixels before reconstruction.