ct unit 3 test

Question 0

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

Answer 0

mAs

Question 1

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

Answer 1

Display Field of View

Question 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

Answer 2

Slice Thickness

Question 3

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

Answer 3

Image Quality

Question 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.

Answer 4

kVp

Question 5

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

Answer 5

Voxel

Question 6

Determines how the data are filtered in the reconstruction process.

Raw data is filtered

Answer 6

Reconstruction algorithm

Question 7

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

Answer 7

Operator’s console

Question 8

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

Answer 8

Translation or Rotation

Question 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

Answer 9

Pitch

Question 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

Answer 10

Scan Field of View

Question 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.

Answer 11

Contrast Resolution

Question 12

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

Isocenter is very crucial for spatial resolution

Answer 12

Spatial Resolution

Question 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

Answer 13

Temporal Resolution

Question 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

Answer 14

Uncoupling effect

Question 15

Spatial Resolution is also termed as

Answer 15

Detail Resolution

Question 16

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

Answer 16

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

Question 17

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

Answer 17

120-140 kVp

20-800 mAs

Question 18

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

Answer 18

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

Question 19

5. Identify the common matrix size used in CT.

Answer 19

512x512

Question 20

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

Answer 20

If you decrease the DFOV it improves spatial resolution

(d)= FOV/matrix

Question 21

How does matrix size effect spatial resolution?

Answer 21

Matrix Size: increased matrix size, improves spatial resolution

Question 22

How does pixel size effect spatial resolution?

Answer 22

Pixel Size: reduced pixel size = improved spatial resolution

Question 23

How does focal spot size effect spatial resolution?

Answer 23

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

Question 24

How does pitch effect spatial resolution?

Answer 24

) Pitch: increasing the pitch reduces spatial resolution

Question 25

How does patient motion effect spatial resolution?

Answer 25

) Patient Motion: reduces spatial resolution

Question 26

How does slice thickness effect spatial resolution?

Answer 26

) Slice Thickness: thinner slices increase spatial resolution

Question 27

What is Spatial Resolution?

Answer 27

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

Question 28

How does mAs/dose effect contrast resolution?

Answer 28

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

Question 29

How does pixel size effect contrast resolution?

Answer 29

) Pixel Size: reduce pixel size decreases contrast resolution

Question 30

How does slice thickness effect contrast resolution?

Answer 30

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

Question 31

How does patient size effect contrast resolution?

Answer 31

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

Question 32

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

Answer 32

Gantry rotation speed, number of detectors channels in the system

Question 33

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

Answer 33

When imaging moving structures and for dynamic moving iodinated CM studies

Question 34

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

Answer 34

Partial Volume Artifact:

Question 35

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

Answer 35

Motion:

Question 36

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

Answer 36

Metallic Artifact

Question 37

by anatomy that extends outside of the selected SFOV Will give a streaky appearance

Answer 37

Out-of Field Artifact

Question 38

caused by imperfect detector elements which appear as a ring or concentric ring 3rd generation

Answer 38

Ring Artifact:

Question 39

Interruption in electricity/electrical surge | Storms

Answer 39

Tube arching

Question 40

What factors affect beam hardening artifacts

Answer 40

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

Question 41

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

Answer 41

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

Question 42

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

Answer 42

) 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

Question 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

Answer 43

Image Reconstruction

Question 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

Answer 44

Image Reformation

Question 45

What are three things that cause artifacts

Answer 45

⚫️equipment ⚫️pt ⚫️physics

Question 46

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

Answer 46

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.

Question 47

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

Answer 47

Segmentation Errors

Question 48

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

Answer 48

Image Noise

Question 49

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

Answer 49

Artifact

Question 50

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

Answer 50

Informatics

Question 51

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

Answer 51

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

Question 52

Used for scheduling patients, storing reports, patient tracking, protocoling examinations, and billing Strictly for the radiology department

Answer 52

Radiology Information System (RIS):

Question 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.

Answer 53

Picture Archive and Communication System (PACS)

Question 54

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

Answer 54

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.

Question 55

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

Answer 55

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.

Question 56

Requires the use of a large pixel size

Answer 56

Contrast resolution

Question 57

Requires the use of a small focal spot size

Answer 57

Spatial resolution

Question 58

Requires the thinner slice thickness

Answer 58

Spatial resolution

Question 59

Requires the use of a smaller pixel size

Answer 59

Spatial resolution

Question 60

Best is patient is of smaller size

Answer 60

Contrast resolution

Question 61

Requires the use of a large matrix size

Answer 61

Spatial resolution

Question 62

Requires the use of a larger slice thickness

Answer 62

Contrast resolution

Question 63

Requires the use of a smaller matrix size

Answer 63

Contrast resolution

Question 64

This parameter has direct influence with mAs

Answer 64

Contrast resolution

Question 65

Prefers the use of a 1 to 2 pitch

Answer 65

Spatial resolution

Question 66

Less patient motion during the scanning

Answer 66

Spatial And contrast

Question 67

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

Answer 67

Spatial resolution

Question 68

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

Answer 68

Contrast resolution

Question 69

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

Answer 69

Contrast resolution

Question 70

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

Answer 70

Spatial resolution