Test 3 Unit 3 - Cont'd

Question 1

Power. Responsible for penetrating anatomy, responsible for producing scatter. higher=more scatter, more penetration.

Answer 1

kVp

Question 2

radiation interacting with matter that travels in all different directions and has experiences loss of energy. Fogs an xray, leading to decreased contrast of the image. radiographic noise.

Answer 2

scatter

Question 3

5 xray interactions with matter

Answer 3

Compton’s Effect, Photoelectric Effect, Classical Scatter, Pair Production, Photodisintegration

Question 4

in the diagnostic energy range (40-150kEv), clinically significant interactions with matter

Answer 4

Compton’s and photoelectric effects

Question 5

most of the scatter produced is this. xrays interacting with matter deflect off outer shell electrons of the material, lose energy, and change direction.

Answer 5

Compton’s Effect

Question 6

the probability that an xray photon will scatter is contingent upon the….

Answer 6

energy of the xray and density of the object

Question 7

xrays are absorbed. xrays lose all of their energy through an ionization interaction with an inner shell electron. causes differential absorptionof xray tissues, thereby producing subject contrast. The elctron has been absorbed causing white on the film.

Answer 7

photoelectric effect

Question 8

As kVp increases, penetration and scatter_______

Answer 8

increase

Question 9

What do high energy xrays tend to do?

Answer 9

pass through matter

Question 10

What low energy xrays tend to do?

Answer 10

become totally absorbed

Question 11

What do mid to high energy xrays tend to do?

Answer 11

scatter

Question 12

The larger the subject ___________________

Answer 12

the more kVp needed = the more scatter produced

Question 13

Xray absorption is also contingent upon…..

Answer 13

xray energy and tissue density

Question 14

Absorption is most likely to occur when…….

Answer 14

the energy of the xray is equal to or slightly greater than the binding energy of the electron it interacts with

Question 15

Greater energy will cause….

Answer 15

the ray to scatter or penetrate straight through

Question 16

Increased absorption is due to

Answer 16

more dense tissues

Question 17

results from low energy xrays interacting with matter

Answer 17

classical scatter (aka Coherent, Thompson, or Rayleigh)

Question 18

These xrays have insufficient energy to cause ionization, but vibrate the atom. Vibrating electrons produce a summative xray with the same wavelength as the incident xray, but in a different dierction

Answer 18

classical scatter

Question 19

occurs with xrays in the MeV (milivolt) range. It interacts with the nucleus and the energy is converted into matter in the form of two particles, a positron and a negatron. The two oppositely charged particles annihilate each other releasing 2 .51 MeV gamma rays in opposite directions

Answer 19

Pair Production

Question 20

occurs when a 10 MeV xray invade a nucleus. The energy is absorbed by the nucleus and nuclear fragments are emitted

Answer 20

photodisintegration

Question 21

Conditions that contribute to scatter radiation production

Answer 21

high kVp, thick soft tissue (water density), large field size

Question 22

Scatter control methods for contrast improvements

Answer 22

optimum kVp, field size control (collimation), scatter-absorbing grids, air-gap technique, recumbent radiography

Question 23

affects radiographic density and contrast

Answer 23

scatter-absorbing grids and air-gap technique

Question 24

selective lead strip filter, placed between the patient and the film, designed to absorb scatter radiation. Gustave Bucky in 1913

Answer 24

scatter absorbing grids

Question 25

Were are grids installed?

Answer 25

inside the front cover of the Bucky

Question 26

When is a grid used?

Answer 26

when the patient part measures greater than 10 cm or when using techniques above 70 kVp

Question 27

how well the grid cleans scatter

Answer 27

grid ratio

Question 28

To reduce scatter radiation, the scatter radiation enters the lead strips...

Answer 28

at an angle where it is absorbed and does not reach the film.

Question 29

Some xray photons, having interacted with the patients body...

Answer 29

change direction, loose energy, and have the potential to reach the film entering from a different direction which degrades the quality of the image

Question 30

the orientation of lead lines follow a ....

Answer 30

linear, cross hatched, or rhombic cross hatched pattern

Question 31

What is the grid made of?

Answer 31

very thin lead lines separated by thin strips of aluminum or carbon fiber

Question 32

two types of linear grid

Answer 32

parallel and focused

Question 33

the lead lines are parallel to each other across the grid plate creating an infinity focus.

Answer 33

parallel grid

Question 34

Because the xray beam diverges from the focal spot, parallel grids typically produce images with reduced exposure on the sides called _______.

Answer 34

grid cutoff

Question 35

Peripheral cutoff of exposure. Grid cutoff appears as underexposure on film.

Answer 35

Parallel lead lines ( we don't use)

Question 36

grid specifications

Answer 36

grid ratio, grid frequency, grid radius, grid focal range

Question 37

Grid ratio

Answer 37

is the measure of the height of the lead strips divided by the distance between them. h/d

Question 38

the higher the grid ratio, the _________ the contrast

Answer 38

higher

Question 39

common chiropractic grid ratios

Answer 39

8:1 and 10:1 and 12:1

Question 40

12:1

Answer 40

focused grid used with a single phase generator

Question 41

10:1

Answer 41

focused grid used with a high frequency generator

Question 42

a measure of the number of lead lines per inch or centimeter the more present the less grid lines on the film but patient does increases

Answer 42

grid frequency

Question 43

every focused grid is manufactured to a set distance

Answer 43

grid radius

Question 44

the set distance without a significant amount of peripheral cutoff

Answer 44

grid focal range.

Question 45

xray outside the range _________ peripheral cutoff

Answer 45

increases

Question 46

removing scatter = _______ film density

Answer 46

reduced. removing gray layers which affects the overall darkness of the film.

Question 47

decreased collimation = ________ density

Answer 47

decreased

Question 48

scatter results from....

Answer 48

primary xray interacting with matter

Question 49

smaller field size = ______ scatter

Answer 49

less. because less primary xrays are interacting with tissues

Question 50

using smaller films and tight collimation

Answer 50

spot filming

Question 51

if the patient part is moved a short distance away from the film, some of the scatter radiation exiting on the film side of the patient will miss the film

Answer 51

air-gap technique (not diagnostic)

Question 52

air gap technique produces a ______ scale contrast

Answer 52

shorter 10" gap maximum

Question 53

recumbent radiography

Answer 53

laying patient down decreases the diameter of the patient which allows for less kVp=less scatter. also helps stabilize a patient

Question 54

not often used in chiropractic. stretched across bucky to compress abdominal tissues with the patient in an upright position

Answer 54

compression band

Question 55

used to cover areas of film on film cassettes where multiple exposure are made on a single film

Answer 55

lead vinyl blockers