Chapter 21: Computer Radiography (CR)

Question 1

-evolved in 1980s
-uses the technology of storage phosphors
pioneered by Eastman Kodak

Answer 1

Computed Radiography (CR)

Question 2

Is CR still consider a type of digital?

Answer 2

Yes, because you can still manipulate the image

Question 3

CR two step process

Answer 3

-acquisition
-image processing and display

Question 4

associated with photostimulable imaging plates

Answer 4

CR

Question 5

How is the CR data read?

Answer 5

It is read in a raster pattern, which is a zig-zag pattern

Question 6

is considered an activator as it maintains the presence of electron holes in the PSP

Answer 6

Europium

Question 7

Common PSP phosphors

Answer 7

-Barium fluorohalide bromides
-Barium fluorohalide iodides

Question 8

What is the best answer for the common psp phosphors

Answer 8

Europium doped barium fluorohalide

Question 9

-reusable plates
-rigid sheet of several layers
-records and transmits image from xray beam
-inserted into cassette
-transferred to reader assembly for processing

Answer 9

photostimulable imaging plates

Question 10

-more sensitive to scatter both before and after exposure, than radiographic film
-sensitive to low levels of radiation energy

Answer 10

PSP’s

Question 11

Why can’t cassetee be left in the room

Answer 11

They are too sensitive

Question 12

best between 35 and 50 kev
-absorb more low energy radiation than radiographic film
- more exposure needed if applied kvp is outside of this range

Answer 12

K-edge attenuation

Question 13

is a digital radiographic imaging modality that uses a photostimulable storage phosphor
imaging plate (PSP or IP), typically inside
a cassette.

Answer 13

CR

Question 14

is the method by which the data are collected from the imaging plate

Answer 14

Raster pattern

Question 15

what type of sampling frequency gives you better detail

Answer 15

Higher sampling frequency

Question 16

how the laser reads the CR (zig zag pattern)

Answer 16

Raster

Question 17

What laser erases the image, making the electrons return to a stable state?

Answer 17

white laser

Question 18

What laser reads the electrons inside the plate?

Answer 18

red laser

Question 19

which laser involves helium neons helps release phosphor

Answer 19

blue/violet laser

Question 20

-Electron pattern stored in active layer of exposed IP
-Fluorohalides absorb beam through photoelectric interactions

Answer 20

latent Image production

Question 21

if you wait to process the image for CR how much energy is lost within 8 hours

Answer 21

latent image will lose approximately 25% of its energy in 8 hours
**important to process cassette shortly after exposures

Question 22

If you don’t run the cassette immediately what happens to those electrons

Answer 22

Those electrons are going to go back to their normal state

Question 23

What are the two types of scanning:

Answer 23

fast scan and slow scan

Question 24

which scan is reading the image (the movement of the laser across the IP)

Answer 24

fast scan

Question 25

which scan is the plate moving through the reader

Answer 25

slow scan

Question 26

PM tubes (photomultipler) convert light to what

Answer 26

to analog electronic signal

Question 27

-PM tubes convert light to analog electronic signal
-Analog electronic signal sent to analog to digital converter
-ADC sends digital data to computer for additional processing
-IP erased via exposure to intense light

Answer 27

Reading CR Data

Question 28

Determines number of density values
-affects density and contrast of system

Answer 28

Pixel Bit depth

Question 29

dependent upon sampling frequency and plate size

Answer 29

Matrix size

Question 30

-raw data located and prepared
-what anatomical part is selected
-orientation of part on IP
-number of projections on IP

Answer 30

preproccessing

Question 31

image file size affected by

Answer 31

-pixel size
-matrix
-bit depth

Question 32

CR Image processing
Two step process:

Answer 32

-pre-processing
-post processing

Question 33

-exposure field recognition (FOV)
-histogram analysis
-grayscale analysis

Answer 33

preproccessing

Question 34

-frequency processing
-spatial location processing

Answer 34

post processing

Question 35

with this processing, you can not change it or manipulate it

Answer 35

pre processing

Question 36

With this processing, you can manipulate the image

Answer 36

post processing

Question 37

-computer looks at distribution of exposure on plate
-improper placement yields histogram analysis errors

Answer 37

Exposure field recognition

Question 38

-obtained image data does not match reference histogram
-computer cannot find collimated edges
-prosthetic devices
-abnormal areas of increased or decreased attenuation

Answer 38

histogram analysis errors

Question 39

for CR what cassette size is the best spacial resolution

Answer 39

Smallest cassette

Question 40

grid error that occurs with digital image receptor systems when the grid lines are cap-tured and scanned parallel to the scan lines in the imaging plate readers. This error occurs with grids used in a stationary fashion for examinations such as mobile radiography or translateral hip images.
grid lines must be running in the same direction as the movement of the laser beam that is scanning the
imaging plate

Answer 40

Moire effect

Question 41

math algorithm of how it is read

Answer 41

Nyquist Frequency

Question 42

how often the lead occurs

Answer 42

grid frequency

Question 43

what technique is there not enough of if there is quantum noise

Answer 43

mAs

Question 44

grid artifact is what type of effect

Answer 44

moire

Question 45

pixel pitch and size is inversely related to:

Answer 45

spatial resolution

Question 46

Th minimum separation between two objects at which each can be distinguished as two seperate objects in the image;most similar to sharpness of detail

Answer 46

spatial resolution

Question 48

CANNOT be manipulated after exposure; dependent on image acquisition and display factors which include:

Answer 48

o Pixel size
o Number of pixels
o Pixel density
o Pixel pitch
o Sampling frequency