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CT image production > Image production > Flashcards

Image production Flashcards

1
Q

CT differentiation of tissue relies on…

A

Densities of tissues

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2
Q

X ray production requires 3 things…

A

Electrons, means of accelerating them, and means of deceleration

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3
Q

how are CT tube different from x ray

A

thicker anode, faster rotation, higher heat capacity

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4
Q

what does mA control in CT?

A

Intensity, dose, and exposure

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5
Q

rotation time controls…

A

intensity, dose, and exposure

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6
Q

what is the disadvantage of increasing rotation time?

A

lowers resolution

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7
Q

mAs is calculated by

A

mA x rotation time

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8
Q

what does kVp control?

A

Energy, Dose, and Penetration

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9
Q

what is the function of detector array?

A

detecting photons and converting it to electrical signal called attenuation measurement

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10
Q

what does Data Acquisition system do?

A

it measures the transmitted rad, converts electrical signal, and transmit to raw data

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11
Q

X axis indicates

A

Right to left

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12
Q

Y Axis indicates

A

Vertically, anterior to posterior

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13
Q

Z Axis extends

A

Superior and Inferior

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14
Q

Coronal view changes from Ant to Post which is what axis?

A

Y Axis

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15
Q

Sagittal view changes from Right to left, which is what axis?

A

X axis

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16
Q

what is axial scanning?

A

Slice by slice, it is a non-continuous exposure

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17
Q

Helical scanning is also called

A

Spiral scanning, the table is in constant motion

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18
Q

what scan technique is used with contrast?

A

Helical scan, best for contrast enhancement

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19
Q

what is volume scanning?

A

it is like axial, but it is organ specific. Entire organ is scanned

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20
Q

how would you describe pitch?

A

pitch is the ratio of table movement to beam width

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21
Q

What are the different values of pitch?

A

pitch is either greater to 1, 1, or less than 1

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22
Q

When the pitch is greater than 1…

A

when table moves more than the beam width itself

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23
Q

When pitch is less than 1…

A

when the table moves shorter than the beam width

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24
Q

what is the advantage of less than 1 pitch

A

highest spatial resolution, but disadvantage is highest dose and slowest scan

25
Q

pitch greater than 1 advantage is

A

it is the fastest scan speed, but lowest spatial resolution

26
Q

how do you calculate for table movement?

A

Beamwidth x Pitch

27
Q

is 1mmx16 rows the same as 2mm x 8 rows and 4mmx4 rows?

A

Yes

28
Q

what is the benefit of thin rows ?

A

higher spatial resolution

29
Q

thick rows benfits are?

A

lower pt dose and faster scan

30
Q

whats wrong with faster scan and less patient dose acquisition thickness adjustment?

A

decreased spatial resolution

31
Q

Raw data is also known as

A

Scan data

32
Q

what is interpolation?

A

It is a reconstruction process unique to helical scan, it can be summarize as deduction method.

33
Q

What is convolution used for? and what are the 2 types?

A

it is used for reconstruction. Smooth and edge enhancing

34
Q

Standard algorithm is also known as

A

Smooth

35
Q

what is filtered backprojection

A

projections being compiled back onto each other

36
Q

what are the 3 steps of reconstruction?

A

Interpolation, Convolution, and Filtered Backprojection

37
Q

what are the differences in prospective vs retrospective recon?

A

time at which it was done, either before or after

38
Q

Reconstruction slice thickness depends on….

A

anatomical parts

39
Q

Chest, Abd, and pelvis are thicker/thinner slices?

A

Thicker

40
Q

What’s wrong with thinner slices?

A

increases image noise

41
Q

True or false, thick slices must be applied to all, coronal, axial, and sagittal

A

False, they can be different

42
Q

When slice interval is equal to thickness

A

there are no space a part

43
Q

If slice interval is more than the thickness what would happen?

A

there would be gap between slices

44
Q

if slice interval is less thank thickness?

A

there would be overlapping of information

45
Q

does changing the window width and level affect Hounsfield Unit?

A

no

46
Q

what increases spatial resolution?

A

recon for thinner slice, smaller detector size, decreasing pitch, increasing rotating time, decreasing DFOV, Decrease acquisition thickness, increasing matrix size

47
Q

how is spatial resolution measured?

A

line pairs per centimeters

48
Q

Does algorithm affect spatial resolution?

A

yes

49
Q

When Spatial Resolution is increased.. what can unfortunately happen?

A

increased image noise

50
Q

what is contrast resolution?

A

ability to tell the difference between the anatomy in the area

51
Q

If image noise increase… what happens to contrast resolution?

A

decreases contrast resolution

52
Q

Can algorithm affect contrast resolution?

A

yes

53
Q

If you want to increase contrast resolution what can you do?

A

increase technical factors, avoid scaning big pts, using thicker detector rows, using thick recon slice,

54
Q

how do you quantify image noise?

A

by placing ROI in the general area and checking the average HU and Stand. Dev

55
Q

what is Standard deviation also known as?

A

Image noise

56
Q

Ability of scanner to produce still images of objects in motion describes…

A

Temporal resolution

57
Q

what increases temporal resolution?

A

increasing scan speed

58
Q

what are the quality control tests?

A

spatial res, contrast resolution test, Image noise, Accuracy of CT numbers, linearity test (as attenuation incr, CT number should incr), Uniformity (same CT number in same substance regardless of diff ROI)

CT image production (1 decks)

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