Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

FINALS > CT > Flashcards

CT Flashcards

1
Q

what does the window width determine?

A

the number of HUs represented on a specific image.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what does increasing window width do?

A

more HU are used for each shade of gray

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does the window level select?

A

the range of HU, the center CT value of the window width

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the three ingredients that define a helical scan process?

A

continually rotating xray tube, consistant xray output, and uninterrupted table movement

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is pitch?

A

a parameter that describes the CT table movement during a helical scan acquisition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what tradeoffs are necessary when pitch is increased?

A

there is a loss of image sharpness and a decrease in slice sensitivity profile (SSP)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how is the dose from an examination consisting of multiple adjacent scans calculated?

A

by the multiple scan average dose (MSAD)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what are the factors that affect the radiation dose?

A

radiation beam geometry, filtration, detector efficiency, slide width and spacing, pitch, scan field diameter, radiographic technique, patient size and body part thickness, repeat scans, and collimation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why are children more radiosensitive than adults?

A

they are smaller and still growing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

is patient shielding effective in reducing the dose from CT?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is reconstruction

A

when raw data are manipulated to create pixels that are then used to create an image

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

give an example of clinical application for reconstruction

A

if a scan of the chest, abdomen, and pelvis was performed and the DFOV (display field of view) was changed for each area since the diameters are different. If the DFOV needed to be consistent for the whole scanned area again, you could go back to the raw data and reconstruct

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

give an example of clinical application for reformation

A

a CT scan?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is reformation

A

when image data are assembled to produce images in different planes, or to produce 3D images

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the disadvantage to the many thin slices produced by MDCT systems

A

there is an unnecessary amount of images to manage and store

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

how can the disadvantage of the many slices produced by MDCT systems be overcome

A

changing image incrementation to maintain image quality while creating a more manageable file

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what is spatial resolution

A

the system’s ability to resolve, as separate forms, small objects that are very close together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

how does a change in slice thickness affect the spatial resolution

A

the thicker the slice, the more photons reach the detectors, giving the image a better SNR (signal to noise ratio)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

how does the slice thickness affect the patient dose?

A

the thicker the slice the more dose the patient recieves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what factors affect spatial resolution

A

matrix size, display field of view, pixel size, slice thickness, reconstruction algorithm, focal spot size, pitch, patient motion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what factors affect contrast resolution

A

mAs/dose, pixel size, slice thickness, reconstruction algorithm, patient size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what are the main advantages of CT over conventional radiography

A

CT defines small objects distinctly, can differentiate objects with similar densities, and has better resolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What defines the Z axis

A

the thickness of the slices in a patient’s body

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a pixel

A

a picture element; a 2d square

25
Q

what is a voxel

A

a volume element; a cube taking the z axis into account

26
Q

what is a matrix

A

the grid formed from the rows and columns of pixels

27
Q

explain beam attenuation

A

the degree to which a beam is reduced and is represented by varying shades of gray

28
Q

What determines a structure’s ability to attenuate the x-ray beam?

A

the objects thickness, density, and the atomic number of the object

29
Q

What unit quantifies a structure’s ability to attenuate the x-ray beam?

A

Hounsfield units. distilled water=0, air=-1000, dense bone=1000

30
Q

What is the relationship between Hounsfield units and the linear attenuation coefficient?

A

1 HU unit=1%difference between linear attenuation coefficient of tissue as compared with linear attenuation coefficient of water

31
Q

What are image artifacts?

A

objects seen on the image but not present on the image scanned

32
Q

Why does the slice thickness vary among examination protocols?

A

for image quality necessary for diagnosis at an acceptable radiation dose. thicker slices to miss small objects, thinner slices for more details and for smaller objects

33
Q

What is the anatomic position?

A

standing erect with palms of hands facing forward

34
Q

how are x-ray photons produced?

A

with fast moving electrons slamming into a metal target. kinetic energy of electrons is transformed into electromagnetic energy.

35
Q

What are the major components for data acquisition?

A

gantry and patient table

36
Q

What advances in scanning where made possible by slip rings?

A

slip rings permit the gantry frame to rotate continuously and they also make helical scan modes possible

37
Q

List the optimal characteristics of a detector

A

high detector efficiency, low or no afterglow, high scatter suppression, high stability

38
Q

Why is it important for all CT staff to set landmarks in the same way?

A

because it helps to maintain consistency between examinations

39
Q

what is high detector efficiency

A

the ability of the detector to capture transmitted photons and change them into electronic signals

40
Q

what is low or no afterglow

A

a brief, persistent flash of scintillation that must be taken into account and subtracted before image reconstruction

41
Q

what is high scatter suppression

A

method to remove scatter from images

42
Q

what is high stability

A

allows a system to be used without the interruption of frequent calibration

43
Q

define algorithm

A

a finite set of unambiguous steps performed in a prescribed sequence to solve a problem

44
Q

define interpolation

A

a mathematical method of estimating the value of an unknown function using the known value on either side of the function

45
Q

List the principal components in a computer

A

hardware and software

46
Q

what is the function of hardware

A

consists of parts of a computer that can be physically touched

47
Q

what is the function of software

A

refers to the instructions that tell the computer what to do and when to do it

48
Q

Explain how computer memory works.

A

ROM and RAM are parts of the systems primary memory (internal memory) primary storage is very fast.

49
Q

In what situation could scan data be lost?

A

RAM is very fast but can be volatile losing the stored data in the case of a power loss

50
Q

what is SFOV

A

scan field of view. determines area, within the gantry, from which the raw are required. located in the center of the gantry and the selection determines the number of detector cells collecting data

51
Q

define ray

A

the path the xray beam takes from tube to detector

52
Q

define view

A

a complete set of ray sums

53
Q

define ray sum

A

the detector senses each arriving ray and measures how much of the beam has been attenuated

54
Q

define attenuation profile

A

the system accounts for the attenuation properties of each ray sum and correlates it to the position of the ray

55
Q

define back projection

A

compiles the information from all of the attenuation profiles to create an image

56
Q

define filter function

A

the process of filtering to minimize artifacts that may appear on an image

57
Q

what is DFOV

A

display field of view. determines how much of the collected raw data are used to create an image. also called zoom or target and affects image quality by changing the pixel size

58
Q

what is the difference between DFOV and SFOV

A

DFOV cannot be larger than SFOV

FINALS (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions