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Determines how much and what section of the collected raw data are to be used to create or display an image.

Changing this factor changes image quality by changing pixel size

Display Field of View

1

Determines the quantity of the x-ray energy and this choice of parameter is more flexible and forgiving.

mAs

2

When a CT technologist selects a smaller inappropriately size of this parameter it will cause a reduction in pixel size therfore increasing in image noise.

If selected too small will reduce voxel size

Slice Thickness

3

The comparison of the image to the actual object being scanned for the means of providing useful information or a diagnosis.

Image Quality

4

Determines the quality of the beam and determines the beams ability to penetrate a thick dense anatomical part.

Main feature of image quality that can be manipulated.

kVp

5

A volume element that is determined by height, length, and width.

Voxel

6

Determines how the data are filtered in the reconstruction process.

Raw data is filtered

Reconstruction algorithm

7

The CT component that the technologist programs in protocols and scan parameters.

Operator's console

8

The distance the table travels between slices during the actual scanning of the patient.

Translation or Rotation

9

A ratio of the distance the table travels per 360 degree rotation to the total collimated x-ray beam width.

Is usually 1-2 only referred to in helical scanning

Pitch

10

Determines the area within the gantry for which raw data area is acquired therefore gantry isocenter is very crucial.

Isocenter crucial determines within gantry for which raw data is acquired

Scan Field of View

11

The ability to differentiate a structure that varies only slightly in density from surrounding structures. CT has superior advantage verses conventional radiography with this ability to distinguish .5 percent paramater variation.

Contrast Resolution

12

The system's ablity to resolve, as separate forms, small objects placed together


Isocenter is very crucial for spatial resolution

Spatial Resolution

13

How rapid the data is acquired and this parameter is controlled by the gantry rotation speed, the number of detector channels in the system and the speed with which the system can record changing signals.

The speed

Temporal Resolution

14

Occurs in digital imaging and refers to the fact that the relationship between radiation dose and the image quality is less direct than in film screen imaging.

In digital you really can't see if your image is over or under exposed

Uncoupling effect

15

Spatial Resolution is also termed as

Detail Resolution

16


2. What operations can the CT Technologist perform at the Operator’s Console?

• Starting or ending, changing of normal protocol scanning parameters, thickness and table increments, windowing and leveling of images as it appears on CRT

17


3. ? Identify the maximum ranges for the kVp and the mA settings.

120-140 kVp
20-800 mAs

18


4. How does the matrix size and display field of view have an effect on pixel size?

When DFOV is kept constant and matrix size is increased, pixel size is reduced

19


5. Identify the common matrix size used in CT.

512x512

20


6. Identify the affects of increasing or decreasing field of view has on the size of the pixel.
How to convert pixel size.

If you decrease the DFOV it improves spatial resolution
(d)= FOV/matrix

21

How does matrix size effect spatial resolution?

Matrix Size: increased matrix size, improves spatial resolution

22

How does pixel size effect spatial resolution?

Pixel Size: reduced pixel size = improved spatial resolution

23

How does focal spot size effect spatial resolution?

) Focal Spot Size: smaller focal spot size= increases spatial resolution

24

How does pitch effect spatial resolution?


) Pitch: increasing the pitch reduces spatial resolution

25

How does patient motion effect spatial resolution?

) Patient Motion: reduces spatial resolution

26

How does slice thickness effect spatial resolution?

) Slice Thickness: thinner slices increase spatial resolution

27

What is Spatial Resolution?

The ability to resolve as separate forms small objects that are close together

28

How does mAs/dose effect contrast resolution?

) mAs/Dose: increase mAs- increases contrast resolution- increases patient dose

29

How does pixel size effect contrast resolution?

) Pixel Size: reduce pixel size decreases contrast resolution

30

How does slice thickness effect contrast resolution?

) Slice Thickness: thicker slices allow more photons reducing noise (increase contrast)

31

How does patient size effect contrast resolution?

) Patient Size: larger patients require more photons but increase attenuation factor creating noise (decrease contrast resolution)

32

8. In reference to the quality of a CT image, temporal resolution is controlled by what scanning parameters?

Gantry rotation speed, number of detectors channels in the system

33

9. When should a technologist be concerned with obtaining the highest temporal resolution possible during their scanning of:

When imaging moving structures and for dynamic moving iodinated CM studies

34

when there is more than one type of tissue is contained within a voxel

Partial Volume Artifact:

35

artifacts from the pt appear as shading, streaking, blurring, or ghosting

Voluntary & involuntary

Motion:

36

when the scan contains metal objects in the SFOV that will create streak artifacts

Metallic Artifact

37

by anatomy that extends outside of the selected SFOV

Will give a streaky appearance

Out-of Field Artifact

38

caused by imperfect detector elements which appear as a ring or concentric ring

3rd generation

Ring Artifact:

39

Interruption in electricity/electrical surge
Storms

Tube arching

40

What factors affect beam hardening artifacts

Filtration low energy parts of the beam before it goes through the patient. Calibration of equipment. Beam hardening software.

Filtration, calibrating, beam hardening software
-relate to petrous ridges because of density

41

12. What are some strategies in which the CT technologist should do to reduce or eliminate motion artifacts?

Prep the patient for the exam fully explaining the procedure and what they need to do. Use breathing instructions. Sedation. Immobilization.

Short scan time to compensate for involuntary motion.

Communication is number one way to prevent movement

42

13. What is the difference between image reconstruction and image reformation for CT imaging?

) Image Reconstruction: Raw data or manipulated to create pixels that are then used to create an image. Images are digitized using an algorithm in which the images was already received by a computer

) Image Reformation: When image data are assembled to produce images in different planes or to produce 3D images. Software allows additional information to be obtained that were not originally scanned

43

: Raw data or manipulated to create pixels that are then used to create an image. Images are digitized using an algorithm in which the images was already received by a computer

Image Reconstruction

44

When image data are assembled to produce images in different planes or to produce 3D images. Software allows additional information to be obtained that were not originally scanned

Image Reformation

45

What are three things that cause artifacts

⚫️equipment
⚫️pt
⚫️physics

46

14. Explain how the following factors degrade a reformatted image?
) Segmentation Errors:

) Image Noise:

) Artifact:.

Segmentation Errors: when a vessel or structure has been subtracted out of edited out

Image Noise: if noise is sufficient enough it will have a big effect on image equality

Artifact: makes it difficult for an accurate reading or diagnosis and can leave gaps.

47

: when a vessel or structure has been subtracted out of edited out

Segmentation Errors

48

: if noise is sufficient enough it will have a big effect on image equality

Image Noise

49

: makes it difficult for an accurate reading or diagnosis and can leave gaps.

Artifact

50


15. What is the term used for the collection, classification, storage, retrieval, and dissemination of recorded information for the imaging department?

Informatics

51

Describe the two key elements in the information infrastructure for imaging network:

Radiology Information System (RIS): Used for scheduling patients, storing reports, patient tracking, protocoling examinations, and billing

) Picture Archive and Communication System (PACS): Technologies necessary for the storage, retrieval, distribution, and display of images

52

Used for scheduling patients, storing reports, patient tracking, protocoling examinations, and billing

Strictly for the radiology department

Radiology Information System (RIS):

53

Technologies necessary for the storage, retrieval, distribution, and display of images

The information must be in digital form. The more information coming to the radiologist the more volume/work flow. You don't store raw data, just the image data.

Picture Archive and Communication System (PACS)

54

17. Why has the PACS system become so important to the imaging world?

PACS allows the integration of image acquisition devices display work stations, and storage systems. This technology has made a big impact on the work flow of radiologists and technologist, as well as referring physicians since it allows easy remote access to the images of pts.

55

18. Why is an optical storage disk the most preferred data storage devices rather than hard copy films?

They can be used for long term data storage. CD/DVD has a greater storage capacity. The CD/DVD can hold more information and in a smaller space than actual hard films.

56

Requires the use of a large pixel size

Contrast resolution

57

Requires the use of a small focal spot size

Spatial resolution

58

Requires the thinner slice thickness

Spatial resolution

59

Requires the use of a smaller pixel size

Spatial resolution

60

Best is patient is of smaller size

Contrast resolution

61

Requires the use of a large matrix size

Spatial resolution

62

Requires the use of a larger slice thickness

Contrast resolution

63

Requires the use of a smaller matrix size

Contrast resolution

64

This parameter has direct influence with mAs

Contrast resolution

65

Prefers the use of a 1 to 2 pitch

Spatial resolution

66

Less patient motion during the scanning

Spatial And contrast

67

This factor depends on the quality of raw data and the reconstruction method as a means of being determined

Spatial resolution

68

Least amount of noise is very detrimental to this type of resolution

Contrast resolution

69

A higher mAs could be used to offset the signal to image noise but increasing the patient dose will result

Contrast resolution

70

The use of reconstruction algorithm can increase and decrease this resolution pending on removing an artifact or fine detail of bone

Spatial resolution