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

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Flashcards in Lecture 1: Intro/X-ray Production/Image Formation/QUIZ 1 (Winter) Deck (63):
1

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

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

2

4 types of diagnostic imaging

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

3

who discovered x-rays?

Roentgen

4

who discovered radioactivity?

Becquerel

5

radiation

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

6

energy and wavelength are (directly/inversely) proportional?

inversely

7

ionizing radiation

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.

8

The energy of electromagnetic radiation is inversely proportional to:

wavelength

9

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

:)

10

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

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

11

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

positive: anode
negative: cathode

12

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

high voltage

13

what metal comprises the cathode filament?

tungsten

14

fx of focusing cup

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

15

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

low voltage, high resistance

16

what metal comprises the anode (target)?

tungsten, rhenium

17

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

cathode

18

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

anode

19

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

high voltage, low resistance

20

kVp

-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

21

mA:

-(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

22

keV:

the duration of a photon/EM wave

23

s-time

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

24

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,b,c

25

Bremsstrahlung

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

26

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

compton scatter

27

ALARA stands for:

As Low As Reasonably Achievable

28

Penumbra

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

29

quantum mottle

-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

summation

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

31

border effacement

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

32

the 5 radiographic opacities are:

gas, fat, soft tissue, mineral, metal

33

3 settings we have control over when taking a radiograph

time (sec), mA, and kVp

34

What happens if kVp is set too low?

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

35

fx of filtration

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

36

fx of collimation

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

37

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

interactions of electrons with metal

38

photoelectric effect vs. compton scatter

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

increased kVp --> likelihood of Compton scatter

increases

40

increased kVp --> likelihood of photoelectric effect (PE)

decreases

41

increased atomic number --> likelihood of PE

increases

42

thickness/density of object --> compton scatter

increases

43

attenuation

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

44

latitude

-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

contrast

-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

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

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

47

increasing kVp --> contrast

decreases

48

more scatter will be produced with increases in:

kVp, field size (collimation), and patient thickness

49

2 methods to reduce scatter after x-ray prod.

grids, air gap

50

What are grids?

-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

grid ratio

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

52

purpose of the image recording system

to form a visual display and permanent record for future comparison

53

what do intensifying screens do?

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

54

4 main components of the intensifying screen and their functions?

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

screen speed

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

56

3 factors that determine screen speed

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

57

faster screen speed --> detail of image

decreases

58

advantages of intensifying screens

-decrease x-ray dose to the patient, exposure times
-increase image contrast

59

disadvantages of intensifying screens

-decrease detail
-artifacts

60

Computed Radiography (CR)

-uses cassettes w/ image plate
-phosphorescence records and stores latent image
-read by laser

61

Direct Digital Radiography (DR)

-x-rays converted to electronic signal
-immediate display

62

What is DICOM?

(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

what is PACS?

(Picture archive and communication system)
-storage of DICOM images in a complex database

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