RT 265 Digital Radiography
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What is a Pixel?
(picture element) This is the Basic component of the digital image; What we see in 2D
What is a Voxel?
- Volume Element. This is the 3D element that includes Depth.The pixel is essentially the End of the Voxel
Voxel is the ------- of the patient?
Thickness of the patient
Is Voxel controlable in CR or DR?
No... its fixed in CR and DR
- With large patients =Poor image
- Small patietn= better image
What is a Matrix?
- The ACTUAL Image we SEE is made up of a series of Pixels in Rows & Colums called a
What is a BIT?
A BIT is the amount of GRAY SCALE
in the image. (Contrast) More bits=more shades of gray
- (bit is the exponenet to TWO)
- 2Bit is two to the second or four
- 2squared 2(2) = 4 shades of gray displayed
Today most image are 10 to 12 Bits
What is FoV?
- Field of View.
- How much anatomy is Displayed
12cm FoV display 12cm of anatomy on the screen
The Smaller FoV= More Magnified Anatomy
Small FoV = Better or Worse Spatial resolution
(This is true for all modalities Except for DR)
Smaller FoV= Better Spatial Resolution
but, image will appear larger
8x10= sharper image vs 14x17=less sharp
Noise= Scatter radiation
The GRAY SCALE of the digital image.
Larger Window width=
More or less grays scales?
Larger Window Width= MORE Gray scales=Lower contrast
(narrow Width= fewer gray scales-shades of gray)= Higher contrast
- Window Level is the DENSITY or BRightness of the image.
- The Higher the number the Brighter the image
What is the Photoconductor made up of?
Amorphous Selenium-->captures x-ray photon & generates a signal
Inderect (CR) Intensifying Screen is made up of?
Cesium-iodide crystals & the Photocondector is made up of Amorphous silicon
What are the Elements of DRD Imaging system
1. Capture Element-to capture x-ray photon
2. Coupling element-Transfers x-ray generated signal to the collection element
- 3. Collection Element- Photodiode, CCD, TFT, CMOS-(light sensitive devices that collect light photons)
- TFT-collect Electrons
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