RT 265 Digital Radiography

(picture element)  This is the Basic component of the digital image; What we see in 2D

• Volume Element. This is the 3D element that includes Depth.
• The pixel is essentially the End of the Voxel

Thickness of the patient

No... its fixed in CR and DR

• With large patients =Poor image
• vs
• Small patietn= better image

• The ACTUAL Image we SEE is made up of a series of Pixels in Rows & Colums called a
• Matrix

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

• Field of View.
• How much anatomy is Displayed

12cm FoV display 12cm of anatomy on the screen

The Smaller FoV= More Magnified Anatomy

Smaller FoV= Better Spatial Resolution

but, image will appear larger

8x10= sharper image vs 14x17=less sharp

Singal =Photons

Noise= Scatter radiation

The GRAY SCALE of the digital image.

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

Amorphous Selenium-->captures x-ray photon & generates a signal

Cesium-iodide crystals & the Photocondector is made up of Amorphous silicon

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