Instrument Operations & Quality Control Flashcards

Which QC test is performed daily on a gamma camera to verify the uniformity of detector response across the field of view?

Answer: Intrinsic uniformity flood

A daily flood uniformity acquisition (intrinsic or extrinsic) confirms that detector response is uniform across the entire field of view.

On a PET scanner, what is the purpose of performing a normalization scan?

Answer: To correct for detector efficiency variations between crystal pairs

Normalization corrects for non-uniform detector efficiencies among the many crystal pairs in a PET ring so that reconstructed images have uniform sensitivity.

A technologist notices that the center of rotation (COR) for a SPECT system is off by more than 2 pixels. What is the most likely consequence if imaging proceeds without correction?

Answer: Ring artifacts in reconstructed SPECT images

An uncorrected COR offset causes ring or 'bull's-eye' artifacts in SPECT reconstructed images, degrading image quality significantly.

What does the energy resolution of a scintillation detector describe?

Answer: The ability to distinguish photons of slightly different energies

Energy resolution, expressed as % FWHM of the photopeak, reflects how well the detector discriminates between photons of closely spaced energies.

Which quality control test for a well counter verifies that the system gives consistent counts for the same source activity on different days?

Answer: Reproducibility (precision) test

A reproducibility or precision test involves repeated counting of a long-lived standard source to confirm day-to-day consistency of the well counter.

What is the primary purpose of the chi-square (χ²) test in nuclear medicine instrumentation QC?

Answer: To verify that a counting system exhibits Poisson (random) statistics

The chi-square test confirms that repeated counts of a stable source follow the expected Poisson distribution, indicating proper random counting behavior.

When performing an extrinsic flood for gamma camera uniformity QC, the collimator is left ON. Why might an intrinsic flood (collimator removed) be preferred for routine uniformity testing?

Answer: It detects subtle non-uniformities in the crystal and PMT array without collimator effects

Intrinsic floods bypass collimator-related artifacts and directly reveal non-uniformities in the NaI crystal and photomultiplier tube array.