Computed Radiography (CR) Imaging and Plate Construction

This set of flashcards covers the hardware components, chemical composition, layer construction, and processing steps of Computed Radiography (CR) and Photostimulable Phosphor (PSP) plates.

What kind of system is Computed Radiography (CR) described as in terms of hardware?

Computed Radiography is a cassette based system.

What material is the backing of the CR cassette made of and what is its function?

It is backed with a thin sheet of aluminum that absorbs x-rays.

What chemical coating is found on the phosphor plate in a CR system?

Photostimulable phosphor (PSP).

What is the purpose of the barcode label on a CR cassette?

It allows the technologist to label the image with the patient information via the identifying barcode on the examination request.

What are the six layers of the CR Imaging Plate construction in order?

1. Protective Layer, 2. Phosphor or active layer, 3. Conductive Layer, 4. Support Layer, 5. Light Shield (Reflective) Layer, 6. Backing Layer.

What mnemonic is used to remember the layers of the CR imaging plate?

PPCSLB (Poor Polly Can't Sing Long Ballads).

The phosphor or active layer is made of photostimulable phosphor from which chemical family?

The barium fluorohalide family.

What are the two functions of the Conductive Layer in a CR imaging plate?

It grounds the imaging plate from electrostatic charge and increases spatial resolution by absorbing light.

What is the purpose of the Light Shield (Reflective) Layer?

It sends light in a forward direction when released in the reader and prevents unwanted light from affecting the unexposed latent image.

What process is required to release the latent (invisible) image from the radiation detector (IP)?

The imaging plate must be processed in a laser reader.

What specific light source is used by the CR reader to scan the imaging plate?

A red helium neon laser light.

What color of visible light is released when the red laser hits the photostimulable phosphor plate?

Blue-violet light.

What device captures the emitted blue-violet light to help create the manifest image?

The photomultiplier tube (PMT).

In CR reader mechanics, what is the difference between slow scan and fast scan?

Slow scan refers to the drive mechanism moving the IP slowly along its long axis, while fast scan is the movement of the laser across the IP.

At what energy level does the red laser light scan in a raster pattern?

$$2\,eV$$

What physical property of the laser beam affects the spatial resolution (detail) of the CR imaging system?

The diameter of the laser beam.

What causes a Ghosting Error artifact on a CR plate?

Incomplete erasure of the imaging plate.

What causes the Moir artifact (Aliasing) in CR imaging?

It is caused by the scanning laser beam overlapping with the grid line structure, often when the laser scan runs parallel to the grid lines.

How is the imaging plate prepared for reuse after the manifest image is created?

The IP is erased with an intense bright white light and returned to the cassette.

What is the function of the Analog-to-digital converter (ADC) in the CR process?

It converts the analog signal (electrical signal from the PMT) into a digital signal to produce the manifest image.