1. DIGITAL RADIOGRAPHY

2. Digital Fluoroscopy
Input phosphoroutput phosphor electronic signal beam splitter video signal  TV monitor
Video signal is a voltage signal which varies continuously 
ADC (Analog Digital Converter) converts analog to digital

3. What are some negatives of conventional (film) radiography?
Difficult to image both soft tissue and bony structures in same image
Difficult to differentiate between the subtle differences of soft tissues (shades of gray---long contrast, low contrast)
Unable to gather quantitative info about attenuation characteristics of anatomy
Image is processed permanent as is
Amount of time needed to process
Archiving/storage/ acquisition issues

4. Similarities between CR and film radiography
Same x-ray tube and generator
Still select optimum kVp and mAs
Accurate positioning
Use cassette or image receptor
There is still a latent image which can be processed into a manifest image

5. DIFFERENCES Imaging plate rather than intensifying screen/film
Photostimulable phosphor-europium activated barium fluorohalide phosphor
200 screen speed equivalent
Phosphors absorb photons
Capable of wider latitudes = better visualization of soft tissues and bone

6. DIFFERENCES CONT. Film made of minute strands of black metallic silver
Digital image = rows and columns called a matrix

7. MATRIX, PIXEL AND VOXEL Matrix made up of pixels ( picture element)
Pixels = x-ray intensity at that location and given a numeric value for the shade of gray
Voxel represent the volume of tissue of the patient
Matrix preferred size – 2048 x2048 or
4, 194,304 pixels
Larger matrix = more pixels and pixels are smaller

8. IMAGE ACQUISITION
Exit(remnant radiation) IP photons absorbed photoelectrically by phosphor LATENT IMAGE
Exposed IP reader unit (digitizer) scanned to release energy as light  photomultiplier tube (PMT) collects, amplifies and converts light to electronic signal to ADC manifest image

9. Manifest image is a matrix composed of pixels with assigned brightness levels
IP scanned again with intense light to erase plate
10,000 readings

10. Histograms/window or index levels/algorithms
Histogram-graphic display of digital data
Used to evaluate adequacy of IP to x-rays
PMT needs to be adjusted to compensate for errors
Window/index levels –
Algorithms – math formulas needed to formulate image construction based on anatomy imaged
Radiographer must indicate correct procedure so the correct algorithms are used.

11. IP or IR

12. IR/IP List some characteristics of an IP
What speed film screen system is associated with a typical IP?
How does this affect technique?

13. DR DIRECT READOUT DIGITAL RADIOGRAPHY
FLAT PANEL DIRECT CAPTURE DETECTOR
CHARACTERISTICS?
COMPARE INDIRECT CONVERSION TO DIRECT

14. Post processing Subtraction Contrast enhancement Edge enhancement
Black and white reversal
Compensate for errors

15. Misc. Resolution =2.5 line pairs per millimeter
Window level = adjusts image brightness
Window width = adjusts radiographic contrast
Quantum mottle
Artifacts
Scatter

16. PACS
HIS
RIS