Image production

Question 1

CT differentiation of tissue relies on…

Answer 1

Densities of tissues

Question 2

X ray production requires 3 things…

Answer 2

Electrons, means of accelerating them, and means of deceleration

Question 3

how are CT tube different from x ray

Answer 3

thicker anode, faster rotation, higher heat capacity

Question 4

what does mA control in CT?

Answer 4

Intensity, dose, and exposure

Question 5

rotation time controls…

Answer 5

intensity, dose, and exposure

Question 6

what is the disadvantage of increasing rotation time?

Answer 6

lowers resolution

Question 7

mAs is calculated by

Answer 7

mA x rotation time

Question 8

what does kVp control?

Answer 8

Energy, Dose, and Penetration

Question 9

what is the function of detector array?

Answer 9

detecting photons and converting it to electrical signal called attenuation measurement

Question 10

what does Data Acquisition system do?

Answer 10

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

Question 11

X axis indicates

Answer 11

Right to left

Question 12

Y Axis indicates

Answer 12

Vertically, anterior to posterior

Question 13

Z Axis extends

Answer 13

Superior and Inferior

Question 14

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

Answer 14

Y Axis

Question 15

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

Answer 15

X axis

Question 16

what is axial scanning?

Answer 16

Slice by slice, it is a non-continuous exposure

Question 17

Helical scanning is also called

Answer 17

Spiral scanning, the table is in constant motion

Question 18

what scan technique is used with contrast?

Answer 18

Helical scan, best for contrast enhancement

Question 19

what is volume scanning?

Answer 19

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

Question 20

how would you describe pitch?

Answer 20

pitch is the ratio of table movement to beam width

Question 21

What are the different values of pitch?

Answer 21

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

Question 22

When the pitch is greater than 1…

Answer 22

when table moves more than the beam width itself

Question 23

When pitch is less than 1…

Answer 23

when the table moves shorter than the beam width

Question 24

what is the advantage of less than 1 pitch

Answer 24

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

Question 25

pitch greater than 1 advantage is

Answer 25

it is the fastest scan speed, but lowest spatial resolution

Question 26

how do you calculate for table movement?

Answer 26

Beamwidth x Pitch

Question 27

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

Answer 27

Yes

Question 28

what is the benefit of thin rows ?

Answer 28

higher spatial resolution

Question 29

thick rows benfits are?

Answer 29

lower pt dose and faster scan

Question 30

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

Answer 30

decreased spatial resolution

Question 31

Raw data is also known as

Answer 31

Scan data

Question 32

what is interpolation?

Answer 32

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

Question 33

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

Answer 33

it is used for reconstruction. Smooth and edge enhancing

Question 34

Standard algorithm is also known as

Answer 34

Smooth

Question 35

what is filtered backprojection

Answer 35

projections being compiled back onto each other

Question 36

what are the 3 steps of reconstruction?

Answer 36

Interpolation, Convolution, and Filtered Backprojection

Question 37

what are the differences in prospective vs retrospective recon?

Answer 37

time at which it was done, either before or after

Question 38

Reconstruction slice thickness depends on....

Answer 38

anatomical parts

Question 39

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

Answer 39

Thicker

Question 40

What's wrong with thinner slices?

Answer 40

increases image noise

Question 41

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

Answer 41

False, they can be different

Question 42

When slice interval is equal to thickness

Answer 42

there are no space a part

Question 43

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

Answer 43

there would be gap between slices

Question 44

if slice interval is less thank thickness?

Answer 44

there would be overlapping of information

Question 45

does changing the window width and level affect Hounsfield Unit?

Answer 45

no

Question 46

what increases spatial resolution?

Answer 46

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

Question 47

how is spatial resolution measured?

Answer 47

line pairs per centimeters

Question 48

Does algorithm affect spatial resolution?

Answer 48

yes

Question 49

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

Answer 49

increased image noise

Question 50

what is contrast resolution?

Answer 50

ability to tell the difference between the anatomy in the area

Question 51

If image noise increase... what happens to contrast resolution?

Answer 51

decreases contrast resolution

Question 52

Can algorithm affect contrast resolution?

Answer 52

yes

Question 53

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

Answer 53

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

Question 54

how do you quantify image noise?

Answer 54

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

Question 55

what is Standard deviation also known as?

Answer 55

Image noise

Question 56

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

Answer 56

Temporal resolution

Question 57

what increases temporal resolution?

Answer 57

increasing scan speed

Question 58

what are the quality control tests?

Answer 58

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)