Digital Radiographic Digital Radiographic Image Processing and Image Processing and

ManipulationManipulationChapter 7

We’ve learned how images are We’ve learned how images are captured….nowcaptured….now

What happens in the reader (CR) pre processing?

How is the image constructed digitally?

LET’S FIND OUT!!!

PRE-PROCESSINGPRE-PROCESSING

THE READER IS TO BE INFORMED AS TO WHAT EXAM WILL BE PROCESSED.

So when you “flash” the cassette, or scan with a bar code reader or in DR, choose the patient and the examination and the views that are to be done

HISTOGRAMHISTOGRAMGraphical representation of optimal densities collected by exposure data recognition .

Exposure data recognition finds the collimated edges , disregards the scatter outside of these edges

Searches for anatomy

This area is the source of exposure data indicator

CR sampling, CR sampling, Carter pg 110 and Carter pg 110 and Page 492 BushongPage 492 Bushong

Notice the collimated area of the lungs in A and find the associated area in B on histogram and C on the response cure. Do the same for the black areas around the chest.

THE SHAPE OF THE HISTOGRAM IS THE SHAPE OF THE HISTOGRAM IS ANATOMY SPECIFICANATOMY SPECIFIC

histogramhistogramhttp://bloggingradiography.blogspot.com/2007/08/

anatomy-of-histogram.html

High energy=less frequency of the same density = narrower histogram

Low energy=more frequencies of the same density= wider histogram

The Nyquist Theorem How are signals converted from analog to digital?

THIS IS STILL THE BEST THIS IS STILL THE BEST EXPLANATION AND RESOURCEEXPLANATION AND RESOURCE

NYQUIST THEOREMNYQUIST THEOREM

When sampling(converting from analog to digital) a signal, the sampling frequency must be greater than the bandwidth of the input signal

http://images.google.com/imgres?imgurl=http://www.cs.cf.ac.uk/Dave/Multimedia/nyquist.gif&imgrefurl=http://www.cs.cf.ac.uk/Dave/Multimedia/node149.html&h=420&w=529&sz=6&hl=en&start=10&um=1&tbnid=zyDOLJNUH6mM8M:&tbnh=105&tbnw=132&prev=/images%3Fq%3Dnyquist%

Sample? Try thisSample? Try this

http://www.pcguide.com/art/soundSampleRate-c.html

WHAT DO YOU THINK THIS IS? PAGE 113 CARTER

Automatic rescaling

SKIPPING LUT,EXPOSURE SKIPPING LUT,EXPOSURE LATITUDE, MTF, QC workstation LATITUDE, MTF, QC workstation functions FOR NOW….NEXT functions FOR NOW….NEXT SEMESTERSEMESTER

However let’s discuss image manipulation

Window

Level

Stitching

REVIEW THOSE PESKY REVIEW THOSE PESKY ACRONYMS!ACRONYMS!

1. PSP2. CRT3. ADC

4. IP5. CR6. DR

7. DQE8. PMT

9. PACS