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Radiology (Spring 2014) > Lecture 1: Intro/X-ray Production/Image Formation/QUIZ 1 (Winter) > Flashcards

Lecture 1: Intro/X-ray Production/Image Formation/QUIZ 1 (Winter) Flashcards

1
Q

Radiology is used as a clinical tool for 4 main things:

A

1) detect presence or absence of disease
2) specific disease recognition and/or localization
3) progression of disease
4) evaluation of therapeutic success of failure

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2
Q

4 types of diagnostic imaging

A

1) MRI
2) Nuclear medicine (i.e. PET scans)
3) Radiography (i.e. CT, fluoroscopy)
4) Ultrasound (i.e. echocardiography)

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3
Q

who discovered x-rays?

A

Roentgen

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4
Q

who discovered radioactivity?

A

Becquerel

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5
Q

radiation

A

the transfer of energy as particles or electromagnetic (EM) waves. Radiation differs in its wavelength, frequency, and energy

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6
Q

energy and wavelength are (directly/inversely) proportional?

A

inversely

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7
Q

ionizing radiation

A

radiation with sufficient energy to cause the atom or molecule that it reacts with to lose an electron; an essential characteristic of high energy radiations when interacting with matter.

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8
Q

The energy of electromagnetic radiation is inversely proportional to:

A

wavelength

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9
Q

light travels at the same SPEED, but at different ENERGIES because of the varying frequencies and wavelengths of light

A

:)

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10
Q

How are x-rays produced? Where does this occur?

A

through the conversion of energy within particulate radiation (electrons) to electromagnetic energy (x-rays). Occurs inside the x-ray tube when high speed electrons collide with the metal anode

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11
Q

Which end of x-ray tube is positive? negative?

A

positive: anode
negative: cathode

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12
Q

What causes electrons to be drawn across the negative and positive ends of the x-ray tube?

A

high voltage

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13
Q

what metal comprises the cathode filament?

A

tungsten

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14
Q

fx of focusing cup

A

negatively charged and focuses the electron cloud from the cathode toward the anode

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15
Q

the cathode of an x-ray tube has (low/high) voltage and (low/high) resistance

A

low voltage, high resistance

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16
Q

what metal comprises the anode (target)?

A

tungsten, rhenium

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17
Q

The (cathode/anode) determines the NUMBER of electrons?

A

cathode

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18
Q

The (cathode/anode) determines the ENERGY of electrons?

A

anode

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19
Q

The anode has (low/high) voltage and (low/high) resistance

A

high voltage, low resistance

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20
Q

kVp

A
  • the energy potential applied from cathode to anode
  • kilovoltage peak applied across the tube
  • refers to the maximum energy of xrays
  • determines how many of the x-rays make it through the patient
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21
Q

mA:

A
  • (milliamperes) controls the resistance of the circuit through the tungsten filament
  • refers to the NUMBER of electrons boiled off the tubngsten tube/number of x-rays produced
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22
Q

keV:

A

the duration of a photon/EM wave

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23
Q

s-time

A
  • the duration of a radiographic exposure

- combined with mA, determines # of x-rays that will be produced during a given exposure

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24
Q

Which of the following is true of electromagnetic radiation?

a: has properties of a wave
b: has properties of a particle
c: travels at the same velocity regardless of wavelength or frequency
d: has a charge

A

a,b,c

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25
Q

Bremsstrahlung

A

the process by which an x-ray is emitted by an e- during loss of kinetic energy

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26
Q

In the diagnostic energy range typically used, the primary interaction of x-rays w/ matter is:

A

compton scatter

27
Q

ALARA stands for:

A

As Low As Reasonably Achievable

28
Q

Penumbra

A

a blurred area around the image of an object that results from use of a large focal spot, or decreased FOD

29
Q

quantum mottle

A
  • relates to the # of photons that are incident on the detector and cause film blackening
  • mottle caused by the statistical fluctuation of the number of photons absorbed by the intensifying screens to form the light image on the film
30
Q

summation

A

the perceived increase in opacity observed when two objects are superimposed upon one another, but not necessarily in the same plane

31
Q

border effacement

A

the inability to distinguish margins of objects that are of the same opacity and in contact w/ one another

32
Q

the 5 radiographic opacities are:

A

gas, fat, soft tissue, mineral, metal

33
Q

3 settings we have control over when taking a radiograph

A

time (sec), mA, and kVp

34
Q

What happens if kVp is set too low?

A

rad will be a shadow of an image b/c x-rays don’t make it through the patient

35
Q

fx of filtration

A

removes the low energy x-rays that we don’t need (won’t be diagnostic, and may cause harm)

36
Q

fx of collimation

A

reduces scatter, protects patients, and focuses on an area of interest when taking a rad

37
Q

clicker Q: X-rays are produced in an x-ray tube by:

A

interactions of electrons with metal

38
Q

photoelectric effect vs. compton scatter

A

Both involve the ejection of an electron when light strikes a metal.

Photoelectric effect:

  • photon is absorbed and does NOT contribute to image formation, electron is released
  • Usually occurs at lower energies

Compton scatter:

  • photon is scattered at some angle and contributes to image formation, and the electron is released with another direction
  • Usually occurs at higher energies
  • degrades image
39
Q

increased kVp –> likelihood of Compton scatter

A

increases

40
Q

increased kVp –> likelihood of photoelectric effect (PE)

A

decreases

41
Q

increased atomic number –> likelihood of PE

A

increases

42
Q

thickness/density of object –> compton scatter

A

increases

43
Q

attenuation

A

reduction in intensity of the primary beam as it travels through an object/patient (i.e. via absorption, scatter)

44
Q

latitude

A
  • the ability of a film to record differences in density
  • maximum difference in radiographic density of anatomical structures that can be evaluated on a given radiograph
  • inversely related to contrast with many shades of gray
  • obtained with HIGH kVp and LOW mAS
  • used for abdomen and thoracic evaluation
45
Q

contrast

A
  • the state of being strikingly different from something else, typically in juxtaposition or close association
  • difference in the photo density (optical whiteness/blackness) b/w 2 adjacent anatomic structures
  • short gray scale
  • obtained with LOW kVp and HIGH mAS
  • used for musculoskeletal evaluation
46
Q

clicker Q: when creating a radiograph of the thorax, your settings should aim to:

A

decrease the inherent contrast in the image, and use a higher kVp

47
Q

increasing kVp –> contrast

A

decreases

48
Q

more scatter will be produced with increases in:

A

kVp, field size (collimation), and patient thickness

49
Q

2 methods to reduce scatter after x-ray prod.

A

grids, air gap

50
Q

What are grids?

A
  • series of radioopaque material (lead) alternated with strips of radiolucent material
  • fx: transmits only those x-rays on a straight line from the source to the image receptor
  • placed b/w the patient and the film to remove scatter prod. by the interaction of the primary beam with the patient
51
Q

grid ratio

A

height of strips/space between the strips (standard ratio = 8:1, 10:1)

52
Q

purpose of the image recording system

A

to form a visual display and permanent record for future comparison

53
Q

what do intensifying screens do?

A

convert x-ray energy into visible light which then exposes the film. Film by itself is an inefficient detector of x-rays

54
Q

4 main components of the intensifying screen and their functions?

A

1) protective coating: prevents damage
2) phosphor: active layer that emits light
3) reflective layer: reflects light photons toward film
4) base: support layer

55
Q

screen speed

A

relative number that identifies the efficiency of conversion of x-ray radiation into light

56
Q

3 factors that determine screen speed

A

1) phosphor type
2) crystal size
3) secondary factors (dye, reflective layer)

57
Q

faster screen speed –> detail of image

A

decreases

58
Q

advantages of intensifying screens

A
  • decrease x-ray dose to the patient, exposure times

- increase image contrast

59
Q

disadvantages of intensifying screens

A
  • decrease detail

- artifacts

60
Q

Computed Radiography (CR)

A
  • uses cassettes w/ image plate
  • phosphorescence records and stores latent image
  • read by laser
61
Q

Direct Digital Radiography (DR)

A
  • x-rays converted to electronic signal

- immediate display

62
Q

What is DICOM?

A

(Digital Imaging and Communications in Medicine)

  • standard for handling, storing, printing, and transmitting info for medical imaging.
  • safe, legal storage of medical record document
63
Q

what is PACS?

A

(Picture archive and communication system)

-storage of DICOM images in a complex database

Radiology (Spring 2014) (1 decks)

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