Computed Radiography CR Cassette Reader - Digital Radiography

Summary

This video explains the process of converting a latent radiographic image on a CR imaging plate into a digital radiograph. The plate is extracted from the cassette and scanned by a helium-neon laser, which interacts with the phosphors to release light photons through photo-stimulated luminescence. These photons are collected and amplified by a photo-multiplier tube or a CCD, then converted into a digital signal by an analog-to-digital converter. The process is completed by erasing the imaging plate for reuse. This technology enables efficient digital imaging in radiography.

Takeaways

• 😀 The latent radiographic image in the CR imaging plate must be processed as close to the exposure time as possible to prevent loss of the image.
• 😀 Plate readers are used to convert the latent image on the CR imaging plate into a digital radiograph.
• 😀 Common components of plate readers include a helium neon laser, laser separator, focusing lens, mirror, photo-multiplier tube, and analog-to-digital converter.
• 😀 The CR cassette is inserted into the plate reader, where rollers extract the imaging plate for processing.
• 😀 The laser beam in the reader is split by a laser separator, with one side used for laser intensity stabilization and the other for imaging plate processing.
• 😀 The laser interacts with the phosphors in the imaging plate in a raster pattern, releasing stored energy as light photons.
• 😀 The released light photons are collected by the photo-multiplier tube and amplified to brighten the signal.
• 😀 Light photons in analog form are sent to the analog-to-digital converter, which converts them into the digital signal required for the radiograph.
• 😀 After the image is processed, the CR imaging plate is erased by exposure to intense white light to prepare it for future images.
• 😀 Some plate readers use a charge-coupled device (CCD) to collect and amplify light photons, as well as convert them into an electrical signal.
• 😀 The overall process involves capturing the latent image on the CR plate, using a laser to release stored energy, and converting that energy into a digital radiograph for computer processing.

Q & A

What is computed radiography (CR)?

Computed radiography (CR) is a digital imaging technique that uses an imaging plate to capture a latent radiographic image. This image is later processed to generate a digital radiograph.

Why should the CR imaging plate be processed soon after exposure?

The CR imaging plate should be processed as soon as possible to avoid any loss of the latent image. If left too long, the stored energy on the plate can degrade, reducing the quality of the final image.

What is the function of the plate reader in computed radiography?

The plate reader's primary function is to process the latent image on the CR imaging plate, converting the stored X-ray image into a digital radiograph by using a laser and other components to extract and amplify light photons.

What are the common components of a CR plate reader?

Common components of a CR plate reader include a helium-neon laser, laser separator, focusing lens, reflecting mirror, photo-multiplier tube (PMT), and an analog-to-digital converter (ADC).

How does the laser in the plate reader interact with the CR imaging plate?

The laser interacts with the phosphors in the CR imaging plate through a process called photo-stimulated luminescence. The laser's light excites the phosphors, releasing stored energy as light photons in proportion to the absorbed radiation.

What is photo-stimulated luminescence?

Photo-stimulated luminescence is the process by which the phosphors in the CR imaging plate release stored energy as light photons when exposed to a laser beam.

Why are the light photons collected and amplified by the photo-multiplier tube (PMT)?

The light photons released from the CR imaging plate are collected and amplified by the PMT to make the light signal brighter, allowing for a clearer and more accurate digital image.

What is the role of the analog-to-digital converter (ADC) in the CR process?

The ADC converts the analog signal of the light photons, which are still in the form of light, into a digital signal required to produce a digital radiograph that can be processed by a computer.

What happens to the imaging plate after the digital image is created?

After the digital image is created, the CR imaging plate is exposed to intense white light to completely erase the latent image, preparing it for subsequent use.

How does a charge-coupled device (CCD) differ from a photo-multiplier tube (PMT) in the CR process?

A charge-coupled device (CCD) combines the tasks of collecting, amplifying light photons, and converting them into an electrical signal, whereas the photo-multiplier tube (PMT) focuses only on collecting and amplifying the light photons.