Principles of Radiology

Question 1

Can xrays be focused on a single point?

Answer 1

No

Question 2

What property of an xray allows it to penetrate

Answer 2

Short wavelength

Question 3

What produces an x ray?

Answer 3

Two electrodes in a glass vaccum tube

Question 4

Which is the positive Electrode?

Answer 4

Anode, the TARGET of negative electrons

Question 5

Which is the negative Electrode?

Answer 5

Cathode, the expeller of negative electrons

Question 6

What does the cathode consist of

Answer 6

Tungsten filament wound in molybdenum cup

Question 7

How does the cathode make electrons?

Answer 7

When the tungsten is heated it boils off electrons

Question 8

What is the process of “boiling off” electrons that the cathode goes through when heated?

Answer 8

Thermionic emission

Question 9

What is the anode made of

Answer 9

Copper for heat conduction and tungsten to produce radiation

Question 10

What percent of the xray kinetic energy produced by the cathode is turned into heat?

Answer 10

99%

Question 11

What are the 3 ways an x ray can interact with a patient?

Answer 11

Scattered
Absorbed
Transmitted

Question 12

Why are scattered x rays bad?

Answer 12

They produce fog on a film

They are a source of exposure for patients

Question 13

What happens when an x ray scatters?

Answer 13

It changes direction and has its energy lowered

Question 14

What is another word to describe an absorbed xray?

Answer 14

Attenuated

Question 15

What determines an xray’s absorbtion?

Answer 15

Wavelength/kilovoltage
Tissue thickness
Atomic Number
Density

Question 16

What color does an absorbed x-ray produce on the film?

Answer 16

White

Question 17

What measurement refers to the amount of x-rays being directed at the patient?

Answer 17

mA

Question 18

What measurement is the penetrating power of the x-ray beam?

Answer 18

kVp

Question 19

What is meant by the term “dead man switch”

Answer 19

It means you have to depress the button to make x-rays….you can’t leave the switch on passively

Question 20

What is the formula for the inverse square law?

Answer 20

I = 1/d^2

Question 21

What is the inverse square law?

Answer 21

The intensity of the radiation varies inversely with the square of the source-film distance

Question 22

What is SFD?

Answer 22

Source-Film Distance

Question 23

According to the inverse square law, what happens to the intensity of the beam if the SFD is doubled?

Answer 23

Intensity decreases by 4x

Question 24

Why does the intensity of the beam lessen as the SFD is increased?

Answer 24

There is more time for the x-rays to disperse which makes the beam less focused.

Question 25

What happens that causes dark/black areas to develop on image?

Answer 25

Primary photons are transmitted through the tissue and are received by the film

Question 26

Why are absorbed x-rays also called attenuated x-rays?

Answer 26

Because the intensity of the beam is reduced as it passed through tissues. Photons are absorbed by the tissue thereby removing them from the beam

Question 27

What will result in full beam attenuation

Answer 27

Metallic restorations

Question 28

What are the two most attenuating natural tissues

Answer 28

Enamel and Cortical bone

Question 29

What is the letter designating the fastest speed film?

Answer 29

F

Question 30

What determines the diagnostic quality of Radiographs

Answer 30

The balance between the visibility and sharpness of the image

Question 31

What does sharpness actually mean

Answer 31

The distinctness between all elements in the film

Question 32

what does mAs stand for?

Answer 32

Millamperage seconds

Question 33

What do the mAs of the beam control?

Answer 33

The density, increasing the mAs will increase the quantity of x-rays produced

Question 34

What is the general rule when adjusting density of the beam?

Answer 34

Increase the mAs by factors of two

Question 35

what does kVp stand for?

Answer 35

Kilovoltage Pontential

Question 36

What does the kVp of the beam control?

Answer 36

The strength and penetrating power. Increases the kVp will allow the x-rays to penetrate deeper into tissue

Question 37

What does Geometric Unsharpness mean

Answer 37

Diffusion of detail

Question 38

What is Penumbra or Edge Gradient?

Answer 38

Fuzzy margin around a structure on a radiograph

Question 39

What is Image Magnification vs. Image Shape Distortion?

Answer 39

Magnification is the equal enlargement of all parts of the radiographic image. Distortion is unequal enlargement

Question 40

Why is there magnification and/or shape distortion?

Answer 40

Because x-rays arise from a field instead of a point and they travel in diverging lines

Question 41

Which cusps are more magnified and distorted? Buccal or Lingual

Answer 41

Buccal

Question 42

What are the five keys to an accurate image?

Answer 42

Small focal spot Source to object distance as long as possible Object to Film distance as short as possible Long axis of object parallel to film Central x-ray perpendicular to film

Question 43

What size focal spot will result in a small penumbra?

Answer 43

Small

Question 44

What magnification results in less penumbra? High or Low

Answer 44

Low

Question 45

What distances should you strive for to minimize both penumbra and magnification?

Answer 45

Maximize Source to Object | Minimize Object to Film

Question 46

What steps should you take to minimize geometric distortion?

Answer 46

Keep film parallel to object | Keep film perpendicular to central x-ray