cr3 Flashcards
What are the four major components of the CR reader?
The imaging plate transport mechanism, the light channeling guide, the photodetector (PMT), and the analog-to-digital converter.
How many main types of PSP readers are there? What are they?
Two types: Point scan and Line scan.
List the components of a point scan type PSP reader.
An optical stage,
scanning laser beam
translation mechanics,
light pickup guide,
photomultiplier
signal transformer/amplifier,
(ADC)
How does the laser beam interact with the imaging plate in a point scan reader at any given time?
Only a single laser point radiates the imaging plate.
What is the fundamental principle behind line scan PSP readers
Simultaneous stimulation of the imaging plate one line at a time.
How is photostimulable luminescence (PSL) acquired in line scan readers?
: With a charge-coupled device (CCD) linear array photodetector.
How does the laser system in a line scan reader differ from a point scan reader?
Instead of a single laser beam, there is a scanning module that contains several linear laser units and optical light collection lenses.
What optical component does a line scan system use to focus the laser beams?
A lens array to focus each laser beam to a corresponding point on the CCD array.
What processing steps are eliminated with PSP systems compared to conventional film-screen radiography?
Chemical processor (wet chemistry) and darkroom are not required.
What two scan directions might a radiographer notice in terms of how the PSP interacts with the reader?
Fast scan direction and Slow scan direction.
Define the fast scan direction in a CR reader. What is it also referred to as?
The movement of the laser across the imaging plate, also referred to as “scan”.
Define the slow scan direction in a CR reader. What are other terms for it?
The movement of the imaging plate through the reader, also known as “translation or sub-scan direction”.
What does LASER stand for?
Light Amplification of Stimulated Emission of Radiation.
Describe how a laser device creates and amplifies light.
Atoms or molecules are excited to higher energy levels. Surfaces at both ends reflect energy, stimulating lower energy atoms to emit secondary photons of the same frequency.
What components does the laser beam pass through before reaching the imaging plate? What is their function?
Beam shaping optics (to modify the beam) and an optical mirror (to direct the beam).
Reading plate process
imaging plate is scanned with helium
laser beam
* The beam scans the plate with red light in a raster pattern and
gives energy to the trapped electrons
* The red laser light is emitted at approximately 2 electron volts
(eV) which is necessary to energize the trapped electrons
* This extra energy allows the trapped electrons to escape the
active layer where they emit visible light at an energy of 3eV as
they relax into the lower energy level
Reading the imaging plate
- As the imaging plate moves through the reader or remains stationary,
the laser scans the imaging plate multiple times - The plate movement through the scanner is known as translation
since it moves in a parallel manner at a certain rate through the
reader, - The translation speed of the plate must be coordinated with the scan
direction of the laser, or the spacing of the scan lines will be affected - This scan process produces light intensity information that are
detected by a photodetector - The photodetector amplifies the light and sends it to ADC to
complete the process of digitizing the image as explained in previous
lecture
