Digital Imaging Lecture Notes

Flashcards generated from lecture notes on Digital Imaging.

What material is the tostimulable Phosphor Plate (PSP) made of?

Barium fluorohalide phosphors

What are the layers of the PSP plate?

Protective overcoat, Phosphor (Active) layer, Reflective (Color) layer, Base layer, Antistatic layer, Lead layer, and Support Layer

What is the function of the Phosphor (Active) layer?

Where the PSP crystals are that trap stimulated electrons during exposure.

What is created when photons that have passed through the body are trapped within the phosphor active layer?

A latent image.

Why is a barcode label placed on the back of the PSP plate?

To match the image information with the patient identifier.

What type of laser is used to scan the cassette in a raster pattern?

Helium-neon laser.

What is the minimum laser beam wavelength required to achieve high spatial resolution?

633nm

What are the grid selection factors for PSP?

Frequency, ratio, and focus.

What does grid frequency refer to?

The number of grid lines per centimeter or lines per inch.

What does Grid Ratio refer to?

Refers to relationship between the height of the lead strips and the space between them. The higher the ratio, the more scatter radiation is absorbed.

What is the primary purpose of collimation?

Reduces the area of irradiation and the volume of tissue in which scatter can occur. Important for reducing patient dose.

What is shuttering?

Postexposure image manipulation technique that adds a black background around the original collimation edges.

Why are anatomical markers important?

To identify the patient and the technologist performing the examination, which is a legal issue.

What type of light is released and collected by the photomultiplier tubes during the 'Read' stage?

Blue/purple light

What process converts the analog signal from the light released by the phosphor into a digital signal?

Analog to digital converter (ADC).

How is a CR plate erased?

Exposing the IR to a bright light to erase any residual (ghost) image.

Why is it not recommended to use kVp values lower than 45 or greater than 120?

Inconsistent and may produce too little or too much excitation of the phosphors.

What happens if there are too few photons during mAs selection?

Lack of sufficient phosphor stimulation (insufficient light production), resulting in quantum mottle or noise.