NCT Quality Control & Equipment Assurance

Question 1

What is the primary purpose of performing a daily flood field uniformity test on a gamma camera?

Accepted Answer

To detect non-uniformities in detector sensitivity that could degrade image quality

Answer

To calibrate the injected radiopharmaceutical dose

Answer

To verify patient positioning accuracy on the imaging table

Answer

To measure collimator hole size and alignment

Question 2

An intrinsic flood field uniformity test is performed by:

Accepted Answer

Removing the collimator and using a distant point source to irradiate the bare crystal uniformly

Answer

Placing a sheet source against a collimator attached to the camera

Answer

Using a bar phantom positioned at isocenter with the collimator on

Answer

Injecting a known activity into a water-filled phantom placed on the detector

Question 3

Which term describes the maximum count-rate difference between any pixel and the mean count rate across the entire detector field of view in a uniformity test?

Accepted Answer

Integral uniformity

Answer

Differential uniformity

Answer

Spatial linearity

Answer

Energy resolution

Question 4

The 'peaking' procedure performed before gamma camera imaging refers to:

Accepted Answer

Adjusting the photomultiplier tube high voltage to center the energy window on the radionuclide photopeak

Answer

Maximizing patient dose to achieve the highest possible count rate

Answer

Setting the SPECT rotation arc to 360 degrees

Answer

Calibrating collimator attenuation at peak energy

Question 5

A bar phantom placed in front of a gamma camera is used primarily to assess:

Accepted Answer

Spatial resolution and spatial linearity

Answer

Detector sensitivity and count rate capability

Answer

Energy resolution of the NaI crystal

Answer

Uniformity across the flood field

Question 6

The acceptable limit for integral uniformity on a modern digital gamma camera, as recommended by NEMA standards, is:

Accepted Answer

Less than 5%

Answer

Less than 2%

Answer

Less than 10%

Answer

Less than 15%

Question 7

Which of the following best describes the energy resolution of a gamma camera?

Accepted Answer

The full-width at half-maximum (FWHM) of the photopeak expressed as a percentage of the peak energy

Answer

The ability to differentiate two point sources separated by a known distance

Answer

The count rate at which dead time losses reach 20%

Answer

The maximum field of view size available for imaging