IRs Flashcards
This performs dynamic studies.
FLUOROSCOPIC SCREEN
The fluoroscope was invented by (1) in (2)
- Thomas A. Edison
- 1896
During fluoroscopy, the XRT is operated at (1), however, the patient dose is considerably higher because the XR beam is emitted for considerably (2) times.
- less than 5 mA
- longer
It is a complex electronic device that receives the image-forming XR beam and converts it into a visible light image of high intensity
IMAGE INTENSIFIER
Each photoelectron that arrives at the output phosphor (image intensifier) results in approximately (1) as many light photons as were necessary to create it.
- 50 to 70 times
Thin, light- tight device, slightly larger than the film it intends to hold
Cassette
CASSETTES loaded with screen-film: The front is made of (1) while the back is made of light metal such as (2).
(3) are used to insure light proof edges. Some inner (back) cassette (except (4)) are lined with thin layer of lead to absorb secondary radiation.
- Bakelite material
- magnesium
- Felt gaskets
- photo timers
— has reported a clever approach to describing and identifying the various DR imaging systems - CAPTURE ELEMENT, COUPLING ELEMENT and COLLECTION ELEMENT
Ehsan Samai
The capture element is that in which the x-ray is captured. In computed radiography (CR), the capture element is the —
photostimulable phosphor
In the other DR modes, the capture element may be (1), (2), (3), or (4).
- NaI
- CsI
- GdOS
- a-Se
The coupling element may be a(1), a (2), or (3)
- lens of fiberoptic assembly
- contact layer
- a-Se
The collection element may be a (1), a (2), or a (3)
- photodiode
- CCD
- TFT
Photodiode vs CCD vs TFT
Photodiode and CCD: light-sensitive devices that collect light photons.
TFT: a charged sensitive device that collects electron
Housed in a rugged cassette that appears similar to a screen-film cassette
Photostimulable phosphor (PSP) screen
The PSP screen-fiim cassette is called —
Imaging plate (IP)
principal advantage of CR
IP is handled in the same manner as a screen-film cassette
Not loaded and unloaded in a darkroom. Rather, it is handled in the manner of a screen-film daylight loader.
PSP screen of the IP
a scintillation phosphor, which is the crystal used in earlier imaging systems which was quickly replaced
Sodium lodide (Nal)
Usually married to a linear array of CCDs through fiberoptic light path
Sodium lodide (Nal)
This signal is channeled to a CCD through fiber-optic channels
Cesium lodide (CSI)
Csl has a high (1) because the atomic number of cesium is (2) and that of iodine is (3)
- photoelectric capture
- 55
- 53
The result for CsI capture elements is high x-ray capture efficiency and good spatial resolution - up to —.
5 lp/mm
had been widely used as the capture element of most rare earth radiographic intensifying screens
Gadolinium oxysulfide (GdOS)
GdOS in screen-film vs GdOS in DR
Screen-film:
- GdOS thickness determines speed of the IR.
- As GdOS screen-film speed was increased, spatial resolution was reduced because of light dispersion in the GdOS.
DR
- Increasing thickness of GdOS in a DR IR increases the speed of the system with no compromise in spatial resolution.
The a-Se is approximately (1) thick and is sandwiched between (2).
- 200 um
- charged electrodes
X-rays incident on the a-Se create (1) through direct ionization of selenium. The created charge is collected by a (2) and remains there until the signal is read by the switching action of the TFT
- electron hole pairs
- storage capacitor
The CCD was developed in the (1) as a highly light-sensitive device for (2)
- 1970s
- military use
The CCD, which is the light-sensing element for most digital cameras, has three principal advantageous imaging characteristics:
- sensitivity
- dynamic range
- size
a silicon-based semiconductor that has higher sensitivity for radiation and a much wider dynamic range than screen-film IRs
CCD
very small, making it highly adaptable to DR
CCD
The CCD itself measures approximately (1), but the pixel size is an exceptional (2)
- 1 to 2 cm
- 100 x 100 um
charge-sensitive device that collects electrons
TFT
Ability to control individually each pixel of the digital display device.
Active read
Nature of reading a digital image receptor line by line
Passive read
Required for the active read
TFT
commonly used scintillator in digital radiography.
Sodium Iodide (NaI) capture element
known for its high efficiency in xr detection.
CsI capture element
serves as an effective phosphor material in radiography
GdOS capture element
acts as a direct conversion material in digital radiography
A-se capture element
transmits the captured X-ray energy to the collection element
Coupling elements
Converts the transmitted xr energy into a digital signal
Collection elements
Collection elements is typically achieved using —
CCD or CMOS (Complementary Metal- Oxide- Semiconductor)
Most commonly used collection element
CCD
known for its high sensitivity and ability to produce high-resolution images
CCD
convert light into electrical signals, which are then processed to create a digital image
CCD
known for its fast image capture and processing capabilities
TFT
embedded in flat- panel detectors to capture and store digital radiographic images efficiently.
TFT arrays
Consists of matrix of switching transistors and capacitors that detect and store data, enabling rapid image capture and processing, making it ideal for clinical setting
TFT
Each pixel has its own pixel and capacitor which allows for individual pixel control and storage of captured data.
TFT
Facilitates swift capture for dynamic imaging applications such as fluoroscopy
TFT
