Digital imaging week 3 cont.II

Question 1

Different frequencies built into the system to allow for more spatial resolution

Answer 1

sampling frequency

Question 2

to match the optical and electronic resolution of system, there should be a sufficient amount of _ to represent the original signal presented

Answer 2

samples per horizontal line

Question 3

Sampling frequency is expressed in

Answer 3

pixels/mm

Question 4

the major factor that limits the recorded detail for indirect digital systems is the

Answer 4

size of the detector element

Question 5

The major factor that limits the recorded detail for direct systems is the

Answer 5

size of the detector element

Question 6

what uses a fine laser beam of variable spot sizes down to 50 um (micrometers)

Answer 6

laser scanners

Question 7

a matrix of data that manipulates the values of gray levels, converting an image input value to a different output value

Answer 7

Grayscale rendition or look up table (LUT)

Question 8

An image processing, lookup tables are often called _

Answer 8

LUT’s

Question 9

LUT’s link _ to output values

Answer 9

index #

Question 10

One common LUT is called the

Answer 10

colormap or palette

Question 11

The color map or palette is used to determine the _

Answer 11

colors and intensity values with which a particular image will be displayed

Question 12

what is a graphic display of the distribution of pixel values

Answer 12

Histogram

Question 13

Each image has its own histogram and is evaluated to determine the

Answer 13

adequacy of the image receptor exposure

Question 14

what is used to identify the edges of the image and assess the raw data prior to image display

Answer 14

Histogram

Question 15

uses processing algorithms and compares it with prestablished histogram for the part

Answer 15

Histogram analysis

Question 16

what is generated with the pixel values on the x-axis and the # of pixels on the y-axis

Answer 16

histogram graph

Question 17

the peeks and valleys represent the

Answer 17

subject contrast

Question 18

the voi is identified with S1 representing the _ and S2 representing the

Answer 18

min. useful signal

max. useful signal

Question 19

computer system automatically adjusts the brightness by comparing the histogram with the LUT

Answer 19

automatic rescaling

Question 20

Overexposures of _ and underexposures of _ can be rescaled without losing image quality

Answer 20

12%

6%

Question 21

For production of an optimal histogram you need a 
correct
choose
center
collimate
control
cover

Answer 21

technique selection
correct body part
CR to VOI
closely, leaving min background
scatter
at least 3% of IR

Question 22

grid error that occurs with digital image receptor systems when the grid lines are captured and scanned parallel to the scan lines in the IP reader

Answer 22

Moire Effect

Question 23

Digital imaging requires that the spatial resolution frequency signal be sampled twice from each cycle, this is the

Answer 23

Nyquist criterion

Question 24

what occurs when the Nyquist criterion is violated; incoming data is sampled less than twice per cycle

Answer 24

Aliasing

Question 25

Aliasing appears as a

Answer 25

Moire pattern

Question 26

for CR the cassette used is a

Answer 26

Photostimulable storage phosphor imaging plate | PSP or IP

Question 27

CR is also called

Answer 27

indirect acquistion

Question 28

Two part process

Answer 28

1. Scintillator | 2. Photodetector

Question 29

converts photons to light

Answer 29

scintillator

Question 30

converts light into an electrical signal

Answer 30

photodetector (charged couple device)

Question 31

Layers of an IP

Answer 31

``` Protective layer Phosphor layer conductor layer support layer light shield layer backing layer ```

Question 32

``` what are the layer's function Protective layer- Phosphor layer- conductor layer- support layer- backing layer- ```

Answer 32

insulates from trauma - active component of IP - grounds plate to avoid static - support base for other layers - prevents light from erasing data - attaches to cassette

Question 33

most common IP phosphor is

Answer 33

barium flourohalide bromides with europium activators

Question 34

a min. of _ of the IR must be exposed for an accurate exposure index to be obtained

Answer 34

3%

Question 35

the latent image will lose _ of its energy in _ hrs.

Answer 35

2% | 8 hrs.

Question 36

latent image is processed by loading the cassette into an image reader device where the plate is scanned by a

Answer 36

helium-neon laser beam

Question 37

the beam scans the _ and emits the latent image in the form of _, which are then converted into an electrical signal, then converted to a _ for that level of luminescence

Answer 37

phosphors light photons digital value

Question 38

reading the IP requires a finely focused red laser beam hat frees the trapped electrons, allowing them to return to a lower energy state called

Answer 38

photostimulated luminescence (PSL)

Question 39

4 CR artifacts

Answer 39

1. Phantom images 2. Dropout artifacts 3. Quantum 4. heat blur

Question 40

Phantom images may appear from

Answer 40

incomplete IP erasure

Question 41

reduction in resolution, result of dust

Answer 41

dropout artifacts

Question 42

caused from inadequate exposure (mAs)

Answer 42

Quantum

Question 43

IR exposure to extreme heat

Answer 43

heat blur

Question 44

4 factors that produce low contrast and are prone to cause IP fog

Answer 44

1. high kV 2. No grid or inadequate grid efficiency 3. Inadequate beam limitation 4. Increased part size or tissue density

Question 45

DR is also called

Answer 45

direct acquisition

Question 46

for a DR what is not needed

Answer 46

cassette

Question 47

direct acquisition directly converts

Answer 47

photons to an electrical signal

Question 48

DR uses

Answer 48

amorphus selenium or amorphus silicon

Question 49

material lacking crystalline structure

Answer 49

Amorphous

Question 50

CR's advantages vs DR

Answer 50

less expensive can be used portably compatible w/existing radiographic tables

Question 51

DR's advantages

Answer 51

immediate readout cassette free can be re-exposed immediately

Question 52

CR's disadvantages

Answer 52

delayed readout cassettes needed plate must be erased before use

Question 53

DR's disadvantages

Answer 53

more expensive | not compatible w/existing equipment

Question 54

what is the greatest advantage of digital imaging over film/screen

Answer 54

post-processing