Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Radiology > Radiation Physics + Biology > Flashcards

Radiation Physics + Biology Flashcards

1
Q

X-ray generation steps

A
  1. Form electron cloud
  2. accelerate electrons into tungsetn target
  3. interaction with tungsten electrons produces x-rays
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what percent of energy created is lost as heat?

A

99%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

focal spot is where? effective focal spot size?

A

in anode

changing angle to about 20 degrees so we can get a smaller focal spot as smaller = more sharpness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why use tungsten?

A

element that has several characteristics of an ideal target material, including the following: •High atomic number (74) •High melting point (3422°C) •High thermal conductivity (173 W · m−1 · K −1 ) •Low vapor pressure at the working temperatures of an x-ray tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what interactions occur in the PATIENT

A
  • Photoelectric absorption

- Compton scattering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what attenuates more bone or soft tissues?

A

BONE

- more dense will attenuate more (like vs. tissues)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Definition of Attenuation

A

– reduction in intensity of the x ray beam by interactions with matter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Definition of Absorption

A

photon ionizes an atom, converts its energy to the kinetic energy of an electron, and the photon ceases to exist

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Definition of Scatter

A

– photon interacts with an atom and moves off in a different direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

interaction in which photon ceases to exist?

A

Absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

which interaction contributes the most to beam attenuation?

A

Compton Scattering

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Breakdown of PERCENTAGES in

A

No interaction - 9% goes right through

Coherent scattering - 7%

Photoelectric Absorption - 27%

Compton Scattering -57%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Primary contributor to the image formation

A

Photoelectric Absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Photoelectric Absorption

A

Primary in image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what two interactions contribute to most x-ray beam attenuation?

A

PE (photoelectric absorption and Compton scattering)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Factors controlling the X-ray beam

A
  1. tube current (mA)
  2. Energy (kVp)
  3. Timer (s)
  4. Shape (collimation)
  5. Intensity (distance)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

energy of the photons is referred to as

A

beam quality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Increasing kVp increases..

A

the number of photons generated

the mean energy of the photons and the maximum energy of the photons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

exposure time and tube current mA are referred to as

A

beam quantity or beam intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Intensity formula

A

o I1/12=d2^2/D1^2
The intensity is inversly proportional to the square of the distance from the source

if move 3 x away
intensity becomes 1/9th

if move 4x as far away it becomes 1/16th of the intensity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

exposure definitino

A

potential of a source of radiation to ionize

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

T/F absorbed dose is the same as equivalent dose

A

TRUE - for our circumstances

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what accounts for 2/3 of radiation induced biological damage

A

INDIRECT effects of radiation

- free radicals

24
Q

deterministic effects occur when?

A

when radiation exceeds a THRESHOLD

  • does NOT occur below threshold levels
  • severity is proprotional to dose

vs. stochastic which there is NO minumum threshold for causation

25
Q

can stoachastic (x-ray radiation) effects cause cancer?

A

Yes we assume it can

they cannot cause deterministic because they do not reach that threshold

26
Q

dental radiographs can cause?

A

stochastic effects

but this is an ASSUMPTION

27
Q

can dental x-rays cause congenital malformations in an embryo or fetus?

A

NO

  • this is a deterministic effect
28
Q

natural background dose of radiation annually?

A

3.1 mSv (micro)

29
Q

daily average background radiation dose?

A

8.5 UsV

30
Q

DENTAL effective dose of ionizing radiation?

A

0.007

31
Q

dose from medical, consumer products and other annually? importance?

A

3.1 msV which is equivalent to natural background radiation dose

32
Q

the optimal operating potential of dental x-ray units is between?

A

60 and 70 kVp

33
Q

patient dose is reduced or increased with higher kVp?

A

reduced

- we would get better contrast with low kVp - but the patient dose is reduced with higher kVp exposures

34
Q

what is the TOTAL average radiation dose in the US from medical and consumer products?

A

3.1 MICRO severts

mSv

35
Q

full mouth with CCD sensor

effective dose in uSv and equivalent background exposure in days

A

85 (5 each)

10 days

36
Q

Bitewing effective dose in microSv and equivalent background exposure in days

A

5 with 0.6 days

so four bitewings would be roughly 2-3 days

37
Q

dose from natural background

A

3.1 mSv

Same as from medical in a year

38
Q

dose from all radiation in a year

A

6.2 mSv

39
Q
  • Daily average background dose
A

8.5 MICROmSv

40
Q

dose mSv from dental

A

0.007 mSv

41
Q

what units are used to describe dose

A
  1. Seivert – effective dose

2. Grey – absorbed dose

42
Q

how much is dose reduced by rectangular collimation compared to round collimation?

A

80%

43
Q

Radiation protection laws and guidelines are made based upon what hypothesis?

A

Linear NON-threshold theory

44
Q

the suspected dose to a fetus wearing a lead apron when getting FMX

A

.25 micro Gy or .25 micro seivert

45
Q

what is the optimal potential of dental x-ray units

A

60-80 kVp

46
Q

filtration minimum

A

aluminum with equivalent half value layer of 1.5mm

w/ filtration of 3mm aluminum the surface exposure is reduced by about 20% of the exposure with no filtration

47
Q

filtration defintion and importance

A

Low energy photons are mostly absorbed by the patient and contributing to the patient dose but not the image

*so if we remove these photons we can reduce the dose without any loss in the radio-graphic information

48
Q

lead aprons vs thyroid collars

A

lead aprons are still required - however seem to be unnecessary

*reducing exposure in the main beam is more necessary

thyroid collars should be used whenever possible as this tissue is more suscpetible to radiation exposure and children are more at risk

every precaution should be made so thyroid collars should be used whenever possible

49
Q

kVp relationship b/w dose and contrast

ideal kVp?

A
  • Should be used within 60-70 kVp
  • Even though lowering the kVp may make image contrast better, the dose to the patient would increase
  • The patient dose is reduced with a higher kVp exposures
50
Q

color if over-exposure? under-exposed?

A

too dark if over-exposed

too light = under-exposed

51
Q

Milliampere-Seconds

A
  • Amperage and time settings for exposure should be set for optimal quality
  • Should be of diagnostic density – so neither too dark (over-exposed) or too light (under-exposed)
  • Correct density should show  faint soft tissue outlines
52
Q

position and distance rule

A
  • At least 6ft (2m) away and at an angle of 90 to 135 degrees to the central ray of the x-ray beam
53
Q

personal dosimeters

A

Recommended for workers who may receive more than 1 mSv and for pregnant workers.
Required by law in certain states
Optically Stimulated Luminescence Dosimeter
Strip of Al2O3 – radiosensitive crystal
Sensitive to 10µSv

54
Q

personal dosimeters recommended for?

A

workers who may recieve more than 1 mSv and for pregnant workers

55
Q

sensitivity of personal dosimeters

A

10 MICROSv

56
Q

what is a typical anode target made from?

A

Tungsten and the stuff around it is copper

57
Q

units for measuring effective dose

A

SEIVERTS (it is a 1:1 conversion with gray but this is the one we will focus on)

Radiology (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions