Image Receptors

Question 1

An image receptor is:

Answer 1

a medium that transforms the x-ray or useful beam into visible image.

Question 2

Useful beam:

Answer 2

x-rays emerging from tube.

Question 3

Remnant beam:

Answer 3

x-rays that remain after the useful beam exits pt. (scatter & image forming x-rays)

Question 4

Image forming X-rays:

Answer 4

X-rays that form the radiographic image by interacting with IR. Also known as Remnant Radiation or Exit Radiation.

Question 5

Three types of Image Receptors:

Answer 5

• Film with Intensifying Screens
• Imaging plates (CR)
• Flat panel detectors (DR)

Question 6

Film:

Answer 6

film cassette contains an intensifying screen which turns energy from x-ray into visible light to expose film

Question 7

Latent image:

Answer 7

invisible image before it is processed into an image we can see.

Question 8

Manifest image:

Answer 8

image after it has been processed so that we are able to see it.

Question 9

CR (Computed Radiography):

Answer 9

uses loaded cassette consisting of imaging plate containing photostimulable phosphor (PSP).

Question 10

DR (Direct Readout digital radiography):

Answer 10

utilizes flat panel of detectors to absorb exit radiation.

Question 11

Neither CR or DR utilize:

Answer 11

film.

Question 12

How are CR IR’s similar to film?

Answer 12

the IR can be used similar to a film cassette – in the Bucky, on the tabletop or in a mobile unit.

Question 13

The CR does not contain a screen, but rather a/n:

Answer 13

Imaging plate.

Question 14

Characteristics of Direct Exposure Film (non-screen film):

Answer 14

used without intensifying screen
single emulsion thicker than screen film
longer developing time
greater exposure
manual processing needed since emulsion is so thick

Question 15

Why is direct exposure film not used frequently in medical imaging?

Answer 15

Exposure is too great to the patient.

Question 16

What areas is direct exposure film used in?

Answer 16

Dental
reconstructive surgery of hand,
biopsy specimen
forensic

Question 17

What is the most widely used type of film?

Answer 17

Screen film

Question 18

Characteristics of screen film:

Answer 18

used with one or two intensifying screens
more sensitive to light 
less sensitive to x-rays
thinner emulsion/less development time
less x-ray exposure
manual or automatic process
single or double emulsion

Question 19

What are the three characteristics of film to keep in mind?

Answer 19

Contrast
Latitude
Speed

Question 20

Contrast is inversely proportional to:

Answer 20

it’s exposure latitude.

Question 21

What is exposure latitude?

Answer 21

the range of exposure factors that will reproduce an acceptable radiograph.

Question 22

What kind of exposure latitude does a high kVp have? (90-120 kVp)

Answer 22

A high kVp has more latitude (or more margin for error).

Question 23

What kind of exposure latitude does a low kVp have? (50-80 kVp)

Answer 23

A low kVp has less latitude (or less margin for error).

Question 24

What does “speed” mean in reference to film?

Answer 24

the degree to which the emulsion is sensitive to x-rays or light OR the ability of an emulsion to respond to radiation such as light and x rays.

Question 25

The greater the speed of film:

Answer 25

the more sensitive it is and the less exposure necessary to produce density on film.

Question 26

Factors affecting speed:

Answer 26

Number of silver halide crystals | size of silver halide crystals.

Question 27

How is film speed and sensitivity influenced by size and number of halide crystals?

Answer 27

As the number of halide crystals and size of the crystals increase, the speed and sensitivity of film increases.

Question 28

How does film speed affect exposure?

Answer 28

the faster the speed of film the less radiation exposure needed to produce a specific density AND the faster the speed of film the less radiation dose to the patient

Question 29

Speed/mAs conversion formula:

Answer 29

Used to determine how to compensate or adjust mAs when changing from fast system to slow system or vice versa mAs1 = IR speed2 mAs2 = IR speed1

Question 30

What exams would one use a fast speed system for?

Answer 30

``` Thorax Abdomen Pelvis Skull Contrast media ```

Question 31

What exams would one use a slow speed system for?

Answer 31

Extremities, mandible, nasal bones

Question 32

Detail or extremity systems are slower and require ___________, which results in _________, and produces _______ recorded detail.

Answer 32

greater exposure rates, greater pt dose, excellent.

Question 33

Increased speed allows a radiographer to:

Answer 33

reduce x-ray exposure to pt and still be able to produce an image with the necessary amount of density to produce a diagnostic image