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Quals > X-ray > Flashcards

X-ray Flashcards

1
Q

what property of the body does it measure

A

tissue density. Denser tissue attenuates xrays a fewer pass through

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2
Q

how is the signal produced (physics)?

A

thermionic electron emission from wire. Focusing on the cup to get tight beam. Anode/cathode cahrge pulls electrons towards tungsten anode. Anode is a spinning disk with angled edged. When electrons hit it, they produce characteristic radiation/Bremmstralung/compton scattering.

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3
Q

what is characteristic emission of x-ray

A

electron knocks out inner electron, upper one falls down and emits x-rays

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4
Q

what is Bremsstrahlung emission of x-rays

A

electron swings off path due to nuclear attraction, slows down & emits energy x-ray

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5
Q

what happens to collimated x-rays

A

they pass through patient, some are attenuated, some are scattered, some reach detector below.

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6
Q

What is the photoelectric effect

A

x-ray in, and electron is knocked out. Proportional to Z^3/E^3 used in mammography- so this is lower energy

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7
Q

What is the Compton scatter

A

x-ray in, electron knocked out with another x-ray- diagnostic normal

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8
Q

what is Rayleigh scatter

A

x-ray in, x-ray out at a different angle

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9
Q

what does the image look like if more x-rays are hitting the detector

A

brighter image

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10
Q

what are the key components of the system

A

anode (tungsten), filter, collimator, grid, detectors

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11
Q

what anode is used for mammography and why

A

molybdenum because it has a Z that is better for differentiating fat from ductal cells

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12
Q

what parameters do we control on x-ray

A

kVp, mA, time, magnification/SID, focal spot size, grid sizes, AEC (automatic exposure control)

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13
Q

what image quality parameters do we look at?

A

spatial resolution (point spread function), contrast, temporal resolution, noise/SNR, heel effect (lower intensity x-rays through back side of anode)

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14
Q

what is the heel effect and draw how it affects an image

A

it lower intensity x-rays through the back side of the anode

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15
Q

what can increasing kvP do to an image

A

it increases the x-ray energy, which means less attenuation, higher dose, but less noise

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16
Q

what does increasing current do to an image

A

it increases the number of x-rays but it increases the signal to noise ratio

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17
Q

what does a shorter SID do

A

it increases the magnification and skin dose, but not the total dose because of the inverse square rule adn there is a bigger penumbra

18
Q

what happens if you increase the focal spot?

A

it just increases the penumbra, but it can take an image of more at a time

19
Q

what are the trade-offs with increasing kvp

A

dose vs. contrast

20
Q

what are the trade-offs with current

A

dose vs. SNR

21
Q

what are the trade-offs with the anode angle

A

greater focal spot size, but more heel effect

22
Q

what are the trade-offs with SID

A

magnification vs. penumbral blur

23
Q

what are the stochaistic effects of x-ray

A

probability increases with dose

24
Q

what are the deterministic effects of xray

A

severity increases with dose (acute radiation poisoning)

25
Q

what level of radiation affects the skin

A

> 2gy

26
Q

what effects the male gonads temp and permanent

A

temp is >2.5 Gy and infertile is >5Gy

27
Q

what are the xray effects to the female gonads temp and permanent

A

> 1.5Gy infertile >6Gy

28
Q

what are the effects radiation level for eyes

A

cataracts at >0.5gy

29
Q

what is the time course of radiation poisoning

A

many weeks for the larger symptoms

30
Q

what systems are affected by ARS

A

hematopoietc, GI, neuocascular

31
Q

what level of radiation for hematopoetic effects

A

death if 2Gy>

32
Q

what level of radiation for the GI synptoms

A

death is 12Gy>

33
Q

what is the level for neurovascualr symptoms

A

death if >50Gy and death within two days

34
Q

what are the three safety factors

A

shielding, distance, adn time

35
Q

what can we do to protect the patient

A

increase filtration, collimate to body part, increase SID, fast detectors

36
Q

how is the x-ray image reconstructed

A

detectors, which there are a variety

37
Q

what is the computed radiography

A

x-rays excite electrons, become trapped in material, read out with a laser at a later point

38
Q

what is direct radiography detector

A

semiconductor/amorphous selenium, x-rays prodyce current directly

39
Q

what is indirect radiography detector

A

scintillator/cesium iode turns x-rays into light, photodiode, capaitive storage element

40
Q

what are the special cases

A

fluoro is live and mammography

Quals (5 decks)

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