Brainscape's Knowledge GenomeTM

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


See full index

R1 > Physics > Flashcards

Physics Flashcards

1
Q

Increasing which factors would increase radiation dose to patient? (3)

A
  • mA
  • kVp
  • scan length (anatomic coverage)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Increasing what factor would decrease radiation dose to patient?

A

pitch

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

What is the effect of increasing screen thickness in film-screen system?

A

Increased chance of xray interacting with the screen

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

Increasing kVp from 100 to 140 on CT abd will have what effect?

A
  • increase radiation dose

- decrease image noise

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

What is beam hardening?

A

xray beam passes thru matter –> low energy photons are removed from xray beam

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

What effect does beam hardening have on xray beam?

A

higher effective energy

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

What will lessen fluoroscopic radiation dose to a patient, in terms of distance of xray source and image receptor?

A
  • xray source: far from patient

- image receptor: close

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

Fluoroscopy –> does electronic magnification have any effect of radiation dose to patient?

A

Yes –> increase radiation

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

Annual whole-body occupational effective dose limit?

A

5 rem (50 mSv)

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

Max dose/yr (whole gestation) for pregnant worker?

A

0.5 rem (5 mSv)

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

What is the threshold for cataracts caused from an acute exposure to the eye (onset > 20 years)

A

0.5 Gy (50 rads)

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

how often is constancy checked on a radioisotope dose calibrator?

A

daily

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

White I radioactive label –> maximum permissible surface exposure rate per hour?

A

0.5 mrem

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

What is the minimum luminance of grayscale monitors required by the American College of Radiology?

A

50 foot-lamberts (171 cd/m^2)

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

medical imaging –> avg annual radiation exposure –> how did it change from 1980s to 2006?

A

increased 6x

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q
  • what is DI?
  • DI of 0 indicates what?
  • positive DI indicates what?
  • negative?
A

deviation index: regarding whether appropriate exposure used

0: intended exposure was used
positive: overexposed
negative: underexposed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is mAs?

A

milliampere-seconds: amt of radiation per second

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

what is air kerma?

A

xray photons per unit area

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

how do mAs and air kerma relate to each other? ie. if mAs is increased x2, what happens to air kerma?

A

linearly proportional

mAs increase 2x –> air kerma increase 2x

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

- SOD?

A

SID: source to image distance

SOD: source to object distance

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

formula for x-ray magnification?

A

M = SID/SOD

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

what is calibration phantom?

what is it for?

A

cylinder or plate –> contain densities of known value –> used in quality control to ensure images are reconstructing density to correct values

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

quality control –> calibration phantom –> needs to be done how often?

A

wkly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

velocity encoded value –> low –> what kind of artifact may occur?

A

aliasing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

principal reason that iodine contrast increases blood’s ability to attenuate xrays?

A

higher atomic # –> increase photoelectric interactions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

trauma –> pregnant F –> CT chest –> fetus –> radiation exposure –> primarily derived from what type of radiation?

A

internal scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

fxal MRI utilitizes what kind of imaging technique?

A

blood oxygen level dependent (BOLD)

28
Q

increase skin to image receptor distance –> entrance skin dose –> increase/decrease? why?

A

increase

xray source –> need to increase radiation output to maintain constant exposure to image receptor to maintain same image quality

29
Q

what physical property allows contrast media to provide enhanced contrast at certain xray energies?

A

K-absorption edge

30
Q

what is K-absorption edge?

A

property of a material that provides preferential absoprtion of xrays for energies near the K-shell energy –> provides increased contrast where the media is located

31
Q

area under the curve (AUC) value from receiver operator characteristic (ROC) curve = 0.5 –> indicates what?

A

inputs are random guesses

32
Q

what is minimum inherent threshold energy required for positron emission decay process to occur?

A

1.022 MeV

33
Q

PET/CT –> typical uptake time?

A

60 min

34
Q

US liver –> acoustic radiation force impulse (ARFI) –> hepatic fibrosis or stiffness estimated by what?

A

speed of the shear wave

35
Q

radioisotope dose calibrator –> quality control –> accuracy –> how often?

A

annual

36
Q

radioisotope dose calibrator –> quality control –> linearity –> how often?

A

quarter

37
Q

control room –> MRI zone?

A

3

38
Q

MRI aliasing (wrap-around artifact) –> how fix?

A
  • increase FOV

- increase velocity encoded value

39
Q

annual occupational dose limit for eye?

A

0.5 Gy

40
Q

calcium –> has what magnetic property?

A

diamagnetic

41
Q

diamagnetic material –> magnetic field properties?

A

induced internal magnetic field –> opposes external field –> weakly repulsed

42
Q

what substances are diamagnetic? (2)

A
  • water

- calcium

43
Q

paramagnetic material –> magnetic field properties?

A

internal field –> enhance local magnetic field –> weakly attracted

44
Q

what substances are paramagnetic? (2)

A
  • gadolinium at body temp

- deoxyhemoglobin

45
Q

ferromagnetic material –> magnetic field properties?

A

internal field –> strongly augment external magnetic field –> strongly attracted

46
Q

what substances are ferromagnetic? (2)

A
  • iron

- cobalt

47
Q

superparamagnetic material –> magnetic field properties?

A
  • strongly augment external magnetic field

- but not magnetic when removed from external field

48
Q

what are isotones?

A

atoms w same #neutrons; diff # protons

49
Q

100 kVp x-ray beam –> avg energy (KeV)?

A

1/3-1/2 of kVp

50
Q

Compared to standard contact imaging, what may compromise image quality of magnification views in mammography

A

increased motion blur

51
Q

The digital radiography system that employs direct conversion of x-rays into a signal (electrons) –> what substance?

A

Amorphous selenium – TFT flat panel array

52
Q

A CT scan is performed at 120 kV and 100 mAs. A region-of-interest measurement from the CSF in the ventricles yields an average CT number of 10 with a standard deviation of 8. The scan is repeated with 400 mAs. What is the expected CT number and standard deviation of the CSF?

A

CT number of 10 with a standard deviation of 4

53
Q

In what direction do chemical shift artifacts manifest in MRI

A

frequency encoded

54
Q

Which radionuclide would require the use of a medium energy collimator to image a patient on a gamma camera ?

A

Ga-67

55
Q

A chief advantage of digital radiography systems over screen film systems is

A

wider exposure latitude

56
Q

acquisition time for a standard spin - echo pulse sequence –> formula?

A

TR x # phase encode steps x # averages

57
Q

What is the annual permissible effective dose equivalent for the general public in the United States

A

1 mSv (0.1 rem)

58
Q

During the preimplantation stage of pregnancy, what is the most likely adverse effect due to a radiation exposure of 200 mGy ( 20 rads)?

A

embryonic death

59
Q

What is the average annual natural background radiation level in the United States?

A

3.1 mSv/yr

60
Q

Portable radiographs taken with a film - screen system utilizing a fixed radiographic grid tend to have less contrast than radiographs taken in radiography rooms because of what?

A

Use of lower grid ratio radiographic grid

61
Q

A computed radiography image with a 10-bit pixel depth will have how many possible shades of gray?

A

1024

62
Q

Dynamic range refers to the ratio of the highest to the lowest amplitude displayed on the screen in decibels –> T/F?

A

T

63
Q

What is the latent image in computed radiography (CR)?

A

Electrons trapped in semi-stable energy wells

64
Q

US –> axial resolution is better than lateral resolution –> T/F?

A

T

65
Q

Concerning the inverse square law in chest fluoroscopy, how much does the entrance dose change if the source - to - image distance (SID) is increased from 90 cm to 120 cm while maintaining a similar source - to - skin distance (SSD) –> inc or dec? by a factor of how much?

A

Increases by a factor of approximately 1.8

66
Q

Concerning ultrasound interaction with matter, an ultrasound beam reflected from small (2 mm) kidney stones would a non-specular reflection –> T/F?

A

T

67
Q

MRI –> which sequence generates the highest signal intensity in a conventional spin - echo pulse sequence?

A

proton density

R1 (15 decks)

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