Digital Radiography Flashcards

Practice flashcards covering Digital Radiography concepts, including CR, DR, image processing, and artifacts based on lecture notes.

What is the primary material used in the Photostimulable phosphor (PSP) layer for Computed Radiography (CR)?

Barium fluorohalide

In a CR plate reader, what color is the laser that scans the plate and what color light is released as a result?

A red laser scans the plate in a raster pattern, releasing blue light.

What specific photoconductor material is used in Direct Conversion Flat Panel Detectors (FPD)?

Amorphous Selenium ($\text{a-se}$)

In Direct Conversion, which component stores the electrons and converts them into an electric signal?

Thin-Film Transistor ($\text{TFT}$)

How long does the 1-step process of Direct Conversion FPD typically take?

$$1-5\,\text{seconds}$$

Wait is the function of the Scintillator (Cesium) in Indirect Conversion systems?

It converts X-rays into light.

What two devices can be used in Indirect Systems instead of a photodiode to convert light into an electric signal?

CCD or CMOS device

What is the relationship between pixel size and spatial resolution?

As pixel size decreases, spatial resolution increases.

What formula is used to determine the number of grays in a pixel based on bit depth?

$$2^n$$

What is the function of the Picture Archival and Communication System (PACS)?

It is a server used to save, manipulate, and send X-ray images, requiring the DICOM format.

How long does PACS typically save images?

$$5-7\,\text{years}$$

What does the Exposure Index (EI #) help the technologist determine?

Whether the digital image was over exposed or under exposed.

What is the Nyquist theory regarding signal reproduction?

The system must sample twice the amount of signal to reproduce it.

What kind of histogram is formed by using high KVP?

A narrow histogram

How is the Look up Table (LUT) used during image processing?

The image's histogram is compared to the LUT and adjusted through automatic rescaling to provide uniform brightness and contrast.

What is the difference between Window Level and Window Width?

Window level adjusts the brightness, while window width adjusts the contrast values.

Why does Direct FPD have the highest Detective Quantum Efficiency (DQE)?

Because it has no light conversion step, which prevents signal loss.

Which component is considered the 'weakest link' in the Modulation Transfer Function (MTF) of a digital radiography system?

The computer monitor

What is the result of increasing the Signal-to-noise-Ratio (SNR)?

Signal increases and noise decreases, but patient dose increases.

Which AEC detectors (cells) should be selected for a PA Chest exam?

The (L) and (R) cells (Left and Right cells).

What adjustment should be made to KVP and MAS for pediatric patients?

Both KVP and MAS should be reduced.

What artifact results from insufficient MAS and gives the image a grainy appearance?

Quantum mottle

How does the 'interpolation' or 'gain calibration' tool address dead pixels?

It fills in the dead pixels with information from surrounding pixels.

What process is used to create a mask of the inherent signal to remove it from subsequent images and prevent image lag?

Offset Correction