Chapter 6 - Image Receptors & Acquisition

Question 1

4 steps for CR:

Answer 1

Expose
Stimulate
Read
Erase

Question 2

Does CR or DR use barium fluorohalide crystals doped with europium for Photostimulable Phosphor (PSP)?

Answer 2

CR

Question 3

After plate is exposed to X-rays, __% of metastable electrons relax (“expose”)

Answer 3

50

Question 4

IP is put in plate reader & ____ _____ passes over remaining mestastable excited electrons to stabilize them. They give off ______ when they relax/stabilize (“stimulate”)

Answer 4

Neon laser

Light

Question 5

Photomultiplier tube (PMT)

Answer 5

Collects light from IP & sends it to analog-to-digital converter (ADC) then to computer

Question 6

Passes over IP to stabilize any remaining excited electrons & clear any remaining image

Answer 6

Intense white light

Question 7

Exposed IPs should be processed within ______ because latent image starts to fade

Answer 7

1 hour

Question 8

Spatial resolution is ____ with increased sampling frequency, increased number of smaller pixels, smaller pixel pitch, & smaller sampling pitch

Answer 8

Increased

Question 9

Spatial resolution is increased with (4)…

Answer 9

Increased sampling frequency
Increased number of smaller pixels
Smaller pixel pitch
Smaller sampling pitch

Question 10

CR plates can be read approximately ______ times before they need replaced

Answer 10

10,000

Question 11

Combines image capture & readout so images are available almost instantly after exposure

Answer 11

DR (direct digital radiography)

Question 12

True or false: DR is less expensive & fragile than CR

Answer 12

False. It is more expensive & fragile

Question 13

Made with layers in order to receive X-ray photons & convert them to electrical charges for storage & readout

Answer 13

Flat panel detectors

Question 14

The first layer of a flat panel detector is

Answer 14

X-ray converter

Question 15

Thin film transistor (TFT) array which is divided into square detector elements (DELs), each with a CAPACITOR to store electrical charges & a switching transistor for readout to be sent to ADC

Answer 15

Second layer of flat panel detectors

Question 16

DR systems (can or cannot) be permanently mounted in table/wall Bucky

Answer 16

Can

Question 17

True or false: DR systems can be available as a mobile IR with “umbilical electrical cord” or wireless

Answer 17

True

Question 18

What uses a scintillator like Cesium Iodide (CsI) or Gasolinium Oxyaulfide to convert exit radiation into visible light, which is converted to electrical charges by photodetectors

Answer 18

Indirect CR

Question 19

Is indirect a 1 stage or 2 stage process?

Answer 19

2 stage

Question 20

3 step process of Indirect (a-Si with CsI):

Answer 20

X-ray > light > electrical charge

Question 21

Uses Amorphous Selenium (a-Se) to convert X-rays directly into electrical charges

Answer 21

Direct DR

Question 22

2 steps of Direct process:

Answer 22

X-ray > electrical charge

Question 23

Dynamic Range

Answer 23

Ability of detector to capture accurately the range of photon intensities exiting patient

Question 24

Digital IRs have much _____ exposure LATTITUDE than film-screen (analog)

Answer 24

Larger

Question 25

Image _____ occurs during post-processing to help produce images with appropriate grayscale appearance

Answer 25

Rescaling

Question 26

If IR is _________ quantum mottle/noise will result

Answer 26

Underexposed

Question 27

If the image is underexposed, the S number will be...

Answer 27

Too high

Question 28

If IR is _______, dose creep occurs

Answer 28

Overexposed

Question 29

If the image was overexposed, the S number will be....

Answer 29

Too low

Question 30

Increased signal-to-noise ratio (SNR) results in:

Answer 30

Improved image quality | Increased signal & decreased noise

Question 31

ALWAYS follow the ______ concept

Answer 31

ALARA

Question 32

Two types film screen systems

Answer 32

Regular cassettes | Extremity cassettes

Question 33

Duplitized or double-emulsion film

Answer 33

Regular cassette

Question 34

Single emulsion film

Answer 34

Extremity cassette

Question 35

Cassette that decreases patient dose with decreased detail (faster)

Answer 35

Regular

Question 36

Cassette that increases patient dose with increased detail (slower)

Answer 36

Extremity

Question 37

Film base

Answer 37

Polyester (usually tinted blue to decrease eye strain)

Question 38

Silver halide crystals suspended in gelatin

Answer 38

Film emulsion

Question 39

Super oat

Answer 39

Protects emulsion layer

Question 40

Theory that is most widely believed to explain latent image foundation on film

Answer 40

Gurney Mott

Question 41

Low scale, long contrast, wide latitude, many colors

Answer 41

High kV

Question 42

Decreased patient dose, increased scatter, good penetration

Answer 42

High kV

Question 43

Short scale, high contrast, narrow latitude, few colors

Answer 43

Low kV

Question 44

Increased patient dose, decreased scatter, poor penetration

Answer 44

Low kV

Question 45

Matching light sensitivity of film to color being given off by screen phosphors

Answer 45

Spectral matching

Question 46

Calcium tungstate color

Answer 46

Blue

Question 47

Rare earth color

Answer 47

Green

Question 48

Purpose of screens:

Answer 48

To INTENSIFY action of X-rays to decrease patient dose

Question 49

Faster screen=

Answer 49

Deceased detail

Question 50

_____ or ______ of screen is most important because it absorbs X-rays & converts them into light

Answer 50

Phosphor | Active layer

Question 51

_____% of density on a radiograph is from light

Answer 51

90-99%

Question 52

____% of density on a radiograph is from direct action of X-rays

Answer 52

1-10%

Question 53

5 INTRINSIC FACTORS that affect screen speed

Answer 53

``` Phosphor size (large=fast) Phosphor type (RE is faster than CT) Active layer thickness (thicker=faster) Reflective layer (faster) Light absorbing dye (slower) ```

Question 54

EXTRINSIC factor affecting screen speed

Answer 54

KV (increased kV = faster)

Question 55

Double screen speed = cut mAs _____

Answer 55

In 1/2

Question 56

Cut screen speed in half = ___ mAs

Answer 56

Double

Question 57

Thin sheet of lead foil on back of cassette is to prevent

Answer 57

Backscatter