Week 4 Flashcards
When and by whom was Computed Radiography (CR) developed?
CR was developed in the early 1980s by the Fuji Corporation.
What are the advantages of CR over film-based radiography?
Eliminates expensive film and chemical processing.
Requires 5-50% less exposure than film.
Uses existing radiographic equipment with specialized receptors.
What are the key components of a CR system?
CR cassette with a photostimulable phosphor (PSP) plate.
CR reader to process the latent image.
Computer system for image processing and display.
What is a latent image in CR?
The invisible stored image created when X-ray photons excite the photostimulable phosphors (PSP) in the imaging plate.
What happens during the Expose step in CR?
The CR cassette stores energy from X-ray photons in the PSP plate, forming a latent image.
What happens during the Stimulate step in CR?
A laser scans the imaging plate in the CR reader, releasing stored energy as photostimulable luminescence (PSL).
What happens during the Read step in CR?
The emitted light is detected, converted into an electrical signal, and processed into a digital image.
What happens during the Erase step in CR?
The imaging plate is exposed to intense light to remove any retained energy, making it ready for reuse.
What is the primary function of the CR cassette?
To protect the imaging plate (IP) from mechanical damage, dust, and static electricity.
What materials make up the CR cassette?
Front (tube side): Radiolucent carbon fiber
Back: Thin aluminum sheet to absorb excess X-rays
Antistatic material to prevent dust buildup and mechanical damage.
Why must the CR cassette be used correctly?
The back of the cassette contains brackets and hinges that can appear on images if used backward.
How does the barcode on the CR imaging plate help with patient identification?
It links the scanned image to the patient’s electronic medical record (RIS system).
What material in the imaging plate stores X-ray energy?
Photostimulable phosphors (PSP) such as barium fluorohalide or cesium bromide crystals.
What element in the PSP layer allows energy storage?
Europium (Eu), which enables the imaging plate to retain energy before processing.
Why must the CR plate be processed soon after exposure?
PSPs gradually release stored energy over time, reducing image quality if processing is delayed.
What is the function of the Protective Layer?
Topmost layer, made of thin, clear plastic. Protects the phosphor layer from mechanical wear and cleaning solutions. Helps improve signal-to-noise ratio.
What is the function of the Phosphor Layer?
Active layer that stores energy from X-ray photons. Releases photostimulated luminescence (PSL) when scanned by a laser. Composed of barium fluorohalide or cesium bromide crystals.
What is the function of the Light Reflective Layer?
Reflects light back toward the detector during plate reading. Prevents loss of signal and reduces light spread.
What is the function of the Conductive Layer?
Absorbs static electricity to prevent image artifacts. Reduces unwanted light emission that could cause false images.
What is the function of the Support Layer?
Made of polymethylene terephthalate (PET). Provides structural strength and stability for other layers.
What is the function of the Colour or Anti-Halation Layer?
Absorbs unwanted stimulating laser light to prevent reflections. Contains a blue-tinted dye to prevent false images.
What is the function of the Backing Layer?
Soft polymer layer that protects the imaging plate from damage. Contains the barcode for patient-image matching.
What is the first step a technologist takes at the workstation before processing a CR image?
Locate the patient on the worklist and select the exam type (e.g., hand, chest, etc.).
Why must the CR cassette be scanned at the workstation before processing?
Scanning the cassette matches the imaging plate to the correct patient and exam type.
