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Quals > CT > Flashcards

CT Flashcards

1
Q

what does CT measure

A

attenuation of tissue

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2
Q

how is a signal processed

A

same as x-ray

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3
Q

what are the components of CT

A

rotating x-ray tube, rotating detector array, grid, filter/bowtie, collimator, gantry adn slip ring for helical scanning

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4
Q

what can we control

A

anode/cathode axis with z axis to avoid heal effect, KVP, mas, focal spot, pitch, rotation time, detector configuration

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5
Q

what is a flying focal spot

A

allows increased sampling for detector size

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6
Q

what parameters are for image wuality of CT

A

spatial resolution, contrast, temporal resolution, noise proportional to 1/swuare root of photon number, HU

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7
Q

how does flying focal spot affect image quality

A

reduces artiface

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8
Q

how does mA affect image quality

A

number of photons-affects noise

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9
Q

how does kVP affect image quality

A

increased dose, decreased contrast

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10
Q

how does pitch/rotation time affect image quality

A

slower the better noise, more motion artifacts though

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11
Q

are thinner slices or thicker slices better

A

thin slices have more noise but better resolution

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12
Q

what is the noise proportional to in CT

A

1/square root of the photon number

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13
Q

what is the trade off on time

A

image quality vs. dose

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14
Q

what is the trade off with mA

A

noise vs. dose

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15
Q

what is the trade off on slice thickness

A

better resolution vs. noise

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16
Q

what is the trade off with kernal

A

spatial resolution vs. noise

17
Q

what are the bioeffects

A

same as x-ray, but more burns

18
Q

how is the image reconstructed

A

detectors-scintillator etc in array, filtered back projection, iterative recontruction

19
Q

when is iterative reconstruction done

A

post processing

20
Q

what are the strengths of CT

A

fast and good detail

21
Q

what are the weaknesses of CT

A

expensive, higher dose, and weight limited

22
Q

what are the special kinds of CT

A

dual energy, cardiac gating, prospective gating, and retrospective gating

23
Q

what is special about dual energy

A

can show different attenuation to distinguish between tissues

24
Q

what is cardiac gated trying to do

A

avoid motion

25
Q

what is prospective gating

A

high pitch or step and shoot, only on low heart rate patients.

26
Q

what is retrospective gaiting

A

record everything then remove the parts you dont want

Quals (5 decks)

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