CRI Digital Radiography Systems 2

Question 1

What is the primary function of a scintillator layer in an indirect flat-panel detector?

Accepted Answer

Convert X-rays into visible light for photodiode capture

Answer

In indirect flat-panel detectors, the scintillator (commonly cesium iodide) converts X-ray photons into visible light, which is then captured by a photodiode array.

Question 2

Which artifact in computed radiography (CR) is caused by a partially erased image remaining on the phosphor plate?

Accepted Answer

Ghost image (residual signal)

Answer

A ghost image (residual signal or ghosting) occurs when the CR phosphor plate was not fully erased before the next exposure, leaving remnants of a prior image.

Question 3

In digital radiography, what does the term 'exposure index' (EI) primarily indicate?

Accepted Answer

The relative amount of radiation reaching the detector

Answer

The exposure index is a numeric value that reflects the radiation exposure level received by the digital detector, used to assess technique adequacy.

Question 4

What is the typical advantage of a cesium iodide (CsI) scintillator over a gadolinium oxysulfide (GOS) screen in flat-panel detectors?

Accepted Answer

Needle-shaped crystal structure that reduces light diffusion and improves resolution

Answer

CsI grows in needle-shaped columns that channel light toward the photodiodes, significantly reducing lateral light spread and improving spatial resolution compared to granular GOS.

Question 5

Which factor most directly affects the spatial resolution of a computed radiography system?

Accepted Answer

The phosphor plate thickness and laser spot size during readout

Answer

Spatial resolution in CR is primarily limited by phosphor layer thickness (affecting light spread) and the size of the laser beam used to stimulate the plate during readout.

(CRI) Certified Radiographic Interpreter Practice Test

(CRI) Certified Radiographic Interpreter Practice Test

CRI Digital Radiography Systems 2