NCT Quality Control & Equipment Assurance 2

Question 1

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

Accepted Answer

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

Answer

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

Question 2

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

Accepted Answer

Weekly

Answer

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.

Question 3

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

Accepted Answer

20% symmetric window centered at 140 keV

Answer

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.

Question 4

Dead time in nuclear medicine instrumentation refers to:

Accepted Answer

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

Answer

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.

Question 5

The multi-window spatial registration test evaluates whether:

Accepted Answer

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

Answer

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.

NCT - Nuclear Cardiology Technologist Practice Test

NCT - Nuclear Cardiology Technologist Practice Test

NCT Quality Control & Equipment Assurance 2