CT Assignment

Question 1

Which generation of CT detectors use a “translate-rotate” tube and detector assembly motion

Answer 1

1st and 2nd

Question 2

which CT scanners use a fanned x-ray beam?

Answer 2

2nd and 3rd

Question 3

True or false: slip ring technology improve temporal resolution

Answer 3

true

Question 4

which artifact result from beam hardening in CT?

Answer 4

Cupping

Question 5

what is the relationship between patient dose and pitch?

Answer 5

if pitch increases, patient dose decreases

Question 6

A technologist wishes to image 40cm of tissue with a beam width of 8mm in 25 sec. If the gantry rotation time is 1.5s, what is the required pitch?

Answer 6

3:1

Question 7

do pre-detector grids in CT scanners increase or decrease contrast?

Answer 7

increase

Question 8

what do sharpening filters do?

Answer 8

• accentuate image noise
• increase spatial resolution
• decrease blurring

Question 9

In CT systems with the capability of gantry angulation, what is the typical maximum degree of angulation possible?

Answer 9

± 30 degrees

Question 10

Solid state scintillation detectors in the latest 3rd generation CT scanners are made of?

Answer 10

Cadmium Tungstate

Question 11

The “filter” in filtered back-projection refers to the?

Answer 11

mathematical function applied to the attenuation profile to reduce blurring

Question 12

A virtual non-contrast image may be generated using data from which dual-energy CT acquisition techniques?

Answer 12

• temporal sequential scanning
• rapid kVp switching
• multilayer detectors
• dual x-ray source

Question 13

For the first time, sub-second imaging was possible with which generation of CT scanners?

Answer 13

3rd

Question 14

True or false: Mild differences in attenuation in the brain requires the use of a sharp filter to accentuate these differences during image reconstruction using filtered back projection technique.

Answer 14

False

Question 15

Image reconstruction times in CT are primarily dependent on the?

Answer 15

RAM

Question 15

Before a CT image can be reconstructed by the computer, the signal produced by the photodiode must be converted into numeric/binary information by which of the following?

Answer 15

Analog-to-digital converter

Question 16

True or false: CT has a higher scatter to primary beam ratio than general radiography.

Answer 16

False

Question 17

The type of filter used between the x-ray tube and the patient in a CT scanner is called a?

Answer 17

bowtie filter

Question 18

Which of the following is not controlled/manipulated by the CT operator when planning image acquisition?

Answer 18

Pitch

Question 19

What would decrease the total scan time for a given volume of tissue in CT?

Answer 19

increasing the number of detector rows during image acquisition and increasing pitch

Question 20

What pitch ratio produce contiguous image slices in CT?

Answer 20

1:1

Question 21

The average CT number (Hounsfield unit) of blood is approximately:

Answer 21

+30 HU

Question 22

Changing Kernels in filtered back-projection results in?

Answer 22

• a trade-off between image shapes and noise

Question 23

True of False: The primary advantage of iterative reconstruction techniques in CT over back projection techniques is faster reconstruction times.

Answer 23

False

Question 24

The technique that involves the estimation of an unknown value from known values on either side of it is termed?

Answer 24

interpolation

Question 25

What is the approximate Hounsfield unit (CT number) of water?

Answer 25

0

Question 26

A disadvantage of 3rd generation CT scanner design compared to previous generations is?

Answer 26

the possibility of ring artifacts

Question 27

True or False: Bowtie filters in 3rd generation CT reduce the intensity of the peripheral x-ray beam to a much greater degree than the central beam.

Answer 27

True

Question 28

The term ____________ describes the ability of the CT scanner to differentiate objects with minimal differences in attenuation coefficients.

Answer 28

contrast resolution

Question 29

When a patient is placed supine on the CT table, the X-axis of the patient...

Answer 29

runs in the right to left direction

Question 30

In dual-energy CT scanners, what is the biggest challenge during temporally sequential scans?

Answer 30

patient motion