CH 13 digital radiography / exam 1 wren

Indirect conversion in DR refers to

And requires what type of device

A two-part process where x-rays are converted to light and then light photons are converted to an electrical signal

Requires a scintillation device and photo-detectors, charge coupled devices and or TFT’s that send those electrical signals to the  image processor so image can be generated: ( Uses Cesium iodide or gadolinium oxysulfide for scintillation)

Direct conversion in DR refers to

Directly convert x-ray photons to an electronic digital signal using a photo conductor (a-Se) and a TFT

 

•Photons interact with selenium atoms and release electrons for capture by the TFT 

Digital imaging systems require __________than screen film radiography?

Require computer processing

Digital radiography is best described by 3 elements ;

capture,coupling, and collection

The ______ element is the element that in which the X-ray is captured.

That in which captures the photons after patient penetration

Capture elements, capture

In CR the ________ element is the _________

Capture, Photostimulable PHOSPHOR( contains barium flurohalide with europium)

In DR, the capture element is ______

Phosphors( sodium iodide Nal or cesium iodide Csl , gadolinium oxysulfide ( GdOS) or amorphous selenium a-Se)

The _____ is that which transfers the X-ray genera Signal to the collection element. The coupling element may be LENS OR FIBER OPTICS AASEMBLY OR CONTACT LAYER OR a-Se

Coupling elements

The ______ element may be a photo diode (photo detector ) , charged coupled device CCD, OR a thin film transistor TFT.

collection element

Each square is called ________ : each containing ______ of information known as ________

Pixel, containing BITS, ,

Known as bit depth EX. If pixel has bit depth of 8, then # of gray tones it can produce is 2 to the power of 8 = 256 shades of

•The greater the # of pixels, the greater the __________or quality of the image!

image resolution

Means to assign a numerical value to each light photon energy phosphor (photoelectrons) stored as the Latent image

 

•Each  energy phosphor is then exposed with an infrared laser light liberates the electrons stimulating the phosphor to release its stored energy in the form of ulta-traviolet light =photostimulable luminescence

 

•The intensity of light emitted is proportional to amount of photons absorbed by storage phosphor

 

•Each phoshor is scanned: electrons sent to digitizer that divides the analog signal into squares called a matrix and assigns each square a number according to brightness or tissue representing patient body part.

Cr digital processing

CR:  

•SPR:  

•CR:  COMPUTED RADIOGRAPHY

•SPR:  SCANNED PROJECTION RADIOGRAPHY

In contrast to CR, which requires a two-step process of Indirect conversion, DR combines __________

combines the two processes.

Scanned projected radiography was developed by CT vendors, what is the process ……

And what was the principal advantage of the SPR

The x-Ray tube and the detector array do not rotate but are stationary and the result is a digital radiograph.

principle advantage; was Collimation, to a fan x-ray with associated scatter radiation rejection and improved image contrast

The charged coupled device CCD was developed in …. As a

Developed in 1970. As a highly sensitive device for military use.

_____ is a light sensitive device that collects light photons

Used for night vision devices, digital cameras, surveillance cams, camcorders, television, astronomy. Therefor reduces patient dose.,,,,,,

CCD

_________ Collect electrons, sends signals to computer immediately for generation of image

THIN FILM TRANSISTORS:

3 Advantageous Imaging Characteristics of charged coupling device

1.  sensitivity

   2.  dynamic range

   3.  size

Sensitivity of the CCD refers to

Dynamic range of CCD refers to

Sensitivity of the CCD refers to; is the ability of the CCD to detect and respond to very low levels of light. Assures using low radiation doses

Dynamic range of CCD refers to the ability of the CCD to respond to a wide range of light intensity, from very dim to very bright, and sensitive to very low radiation exposure, thereby reducing radiation doses

_____ is indirect DR process by which X-rays are converted to light then to electronic signal

csl/CCD

The percentage of the pixel face that is sensitive to X-rays is the ______. The _____ is approximately 80% therefore 20% of the X-ray beam does not contribute to the image.

FILL FACTOR, THE FILL FACTOR

•How efficiently a system converts x-ray input signals into a useful output image

•Is a measure of the percentage of x-rays that are absorbed when they hit the detector

•Dependant on X-ray energy

Known as

Detective quantum effeciancy

The amount of detail or sharpness present in any image

Spatial resolution

_____ & _______ affect image sharpness( image resolution)

Focal spot and OID

Amphorphorus selinum detectors refers to

•Direct Conversion

•No scintillation phosphor is used

•Photons interact directly with Amorphous Selenium producing a charge

•aSe is both the capture and coupling element

•aSe are arranged as an active matrix array of TFT’s

_______ is a direct process by which x-rays are converted Directly into an electronic signal!

•Faster image production!

A-Se

detective quantum Efficiency

•Known as DQE

How efficiently a system converts x-ray input signals into a useful output image

•Is a measure of the percentage of x-rays that are absorbed when they hit the detector

•Dependant on Xray energy