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Flashcards in Forming CT Images Deck (39)
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1

What do you need to measure in order to produce a cross-sectional image?

Attenuation information through many projections

2

What are the three scanning methods used in CT?

Localizer
Conventional (Serial)
Helical

3

When would a localizer image (single projection image) be used?

To position the slices at the location where we want to collect the cross-sectional images

4

Which of the scanning methods used in CT produces cross-sectional images?

Conventional & Helical Scan

5

What is another term used for helical scans?

Spiral or Volumetric CT

6

What views may be collected in a localizer scan?

Lateral
Anterior/Posterior
Oblique

7

When would an AP localizer image be collected?

To specify transverse slices

8

When would a lateral localizer image be collected?

To specify oblique slices when the gantry is angle

9

What is the length of anatomical coverage of the localizer image dependent upon?

Speed of the patient table and amount of time the x-ray tube is on

10

What are the reasons as to why helical CT is most often used in CT studies performed today?

Speed
Ease of use
Ability to reconstruct images

11

Conventional CT yields the best image quality which is free from:

Helical artifacts

12

What are some reasons as to why conventional CT scans may be chosen over helical CT?

Neurological work involving fine detail
Obese patients
Cardiac calcium scoring

13

When performing a conventional scan on a single-row detector scanner, how is raw data obtained?

By a single rotation of the gantry from only one cross-sectional slice location

14

Why does a helical scan's x-ray beam take on a helical path?

The patient table is moved through the gantry at the same time that the x-ray tube rotates around the patient's body

15

Why would a patient be required to refrain from breathing in CT?

To minimize motion artifacts
To avoid skipping anatomy

16

What are some advantages of helical scanning?

Faster studies
More coverage in a breath-hold
No missed anatomy
Less contrast injection needed
Arbitrary slice positioning
Ideal data for post-processing

17

In a helical scan, how is the path of the x-ray beam defined?

Thickness of the x-ray bream
Speed of the patient table

18

How is the thickness of the x-ray beam determined on a single-row detector scanner?

It equals the slice thickness of the final image

19

How is the thickness of the x-ray bream determined on a multi-row detector scanner?

It is divided by the number of rows of detectors being used

20

In which scanning method used in CT does not collect images in a single slice plane?

Helical

21

What must be done to the attenuation information in a helical scan?

It must be divided into raw data files for individual, planar slices

22

What are sharp reconstruction filters often used for?

Visualizing musculoskeletal detail

23

What are smooth reconstruction filters often used for?

Visualizing soft tissue contrast

24

On what kind of scanners would back projection be used?

Single-row detector
Multi-row detector

25

Why would retrospective reconstruction be commonly performed?

To apply a different reconstruction filter

26

Why might retrospective reconstruction be performed on MDCT scanners?

To vary the reconstructed slice thickness

27

Multiplanar reconstruction requires only the _____ data.

Image

28

3D surface rendering is performed on the _____ data.

Image

29

In which orientation would we position the scanner if we want to angle the slice away from the transverse plane and toward the coronal plane?

Lateral

30

What is used to store the actual attenuation data measured by the detectors prior to image reconstruction?

Raw data file

31

What is another term used for reconstruction filter?

“Kernel”

32

On scanners that are capable of collecting 64 slices in one rotation, which reconstruction is used?

Cone beam

33

On scanners that do not collect more than four slices per rotation, which reconstruction method is best to be used?

Back-projection

34

When performing retrospective reconstruction, what kind of data is needed?

Raw data

35

On a single-row detector, how is the slice thickness determined?

By the collimation of the x-ray beam

36

Which reconstruction process is used to reconstruct images in orientations other than the one in which they were acquired?

Multiplanar reconstruction

37

Overlapping slices with no gaps in-between generates the most diagnostic _____ reconstruction

Multi-planar

40

Which reconstruction method allows us to reconstruct images using different parameters than those that were originally reconstructed?

Retrospective reconstruction

41

Which reconstruction process is used to reconstruct cross-sectional CT images from the raw data?

Back-projection