Study guide test 2 Flashcards Preview

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Flashcards in Study guide test 2 Deck (39):
1

Which component organizes and functions?

master synchronizer

2

Which component excites the crystal?

pulser

3

Choose the area on the TGC curve where the attenuation is occurring:

far gain

4

What creates the pattern for phased array?

beam former

5

What are the functions of the receiver?

Amplification-receiver gain

Compensation-TGC

Compression-20 shades of gray, keeps large signal large, small signal small

Demodulation-rectification, smoothing

Reject-rejects low level echoes

6

Who decides the acoustic power of the sound beam?

the sonographer

7

In regards to a pulser, which form has the elctrical signal in a sine wave?

continuous wave

8

What can improve the signal-to-noise ratio? 

Increasing output power increases signal-to-noise ratio, which improves the image quality.

 

9

If an image is too dark or too bright, what are your options?

What tools may you use to improve the image?

Amplification(receiver gain) changes the overall brightness of an image

high amplification=brighter image

Compensation(TGC) corrects for attenuation by creating an image of uniform brightness

10

Which receiver function handles reflector depth?

Compensation(TGC):sound attenuates as it travels

The image gets darker as the depth increases

controlled by compensation

11

What are PRP and PRF?

PRP(pulse repetition period) determines the maximum imaging depth(depth of view)

PRF(pulse repetition frequency) reciprocal of PRP

PRP is short- PRF is high (system spends less time listening)

12

What are the components of an ultrasound system?

#1

master synchronizer:

communicates with all components

organizes timing and functions

13

What are the components of an ultrasound system?

#2

transducer:

converts electrical energy into acoustic energy

converts returning acoustic energy during reception

14

What are the components of an ultrasound system?

#3

pulser:

functions during transmission

controls electrical signals sent to the transducer

determines amplitude, PRP, PRF

15

What are the components of an ultrasound system?

#4

receiver:

transform electrical signals to a form suitable for display

16

What are the components of an ultrasound system?

#5

display:

monitor
 

17

What are the components of an ultrasound system?

#6

storage:

film, sony paper, CD/DVD, video, magnetic disc, USB drives, PACS

18

What can you do when the image is too bright?

What is the better choice?

output power vs receiver gain

output power:changes brightness of entire image, alters signal-to-noise ratio, alters patient exposure, bioeffects concerns, decrease this first if image is too bright

receiver gain:changes brightness of entire image, does not affect signal-to-noise ratio, does not change patient exposure, no bioeffect concerns, increase this first if image is too dark

19

Which function affects the strength of every signal?

amplification

20

What are the disadvantages of an analog scan converter?

Image fade

Image flicker

Instability

Deterioration

21

What are the advantages of a digital scan converter?

Uniformity

Stability

Durability

Speed

Accuracy

 

22

What is responsible for gray scale imaging?

scan converters

23

Know about shades of gray and bits (how to convert them):

each pixel's shade of gray is determined by the cluster of bits assigned to it

8 bits=1 byte, 2 bytes(16 bits)=1 word

We are able to see 20 shades of gray

24

Read Magnification

uses old data

 postprocessing

larger pixel size

same # of pixels as in the original ROI

unchanged spatial resolution

 

25

Write magnification

acquires new data

preprocessing

identical pixel size

more pixels than in the original ROI

improved spatial resolution

may improve temporal resolution

26

Preprocessing

time gain compensation

log compression

write magnification

persistence

spatial compounding

edge enhancement

fill-in interpolation

27

Postprocessing

any change after freeze frame

black/white inversion

read magnification

contrast variation

3-D rendering

 

28

Analog-Digital-Analog Process

Electrical signals created by the transducer are converted from analog to digital by the analog-to-digital (A-to-D) converter

Digital info is stored in the scan converter's computer memory. Any processing of the reflected signals before storage is called preprocessing

Image info (still in digital form) continues to be processed by the ultrasound system's computer. Any processing after storage in the digital scan converter is postprocessing

Digital signals must be translated back into analog form by a digital-to-analog (D-to-A) converter, because digital signals cannot be directly displayed on analog display devices

Signal is now in analog form and can be presented on the analog video display for interpretation 

29

Pixels and shades of gray

fewer bits/pixel: fewer shades of gray, degraded contrast resolution

more bits/pixel: more shades of gray, improved contrast resolution

30

bistable and grayscale imaging

bistable: black and white, high contrast

grayscale: many shades, low contrast

31

What is spatial resolution?

the details in an image

high line density= excellent spatial resolution

32

Analog vs Digital Numbers

analog: real world, unlimited # of choices, continuous values

digital: computer world, limited choices, discrete values

33

what is coded excitation?

method of improving image quality

coded excitation provides: higher signal-to-noise ratio, improved axial resolution, improved spatial resolution, improved contrast resolution, deeper penetration

34

What is spatial compounding?

It is a process of compounding several different frames

it reduces shadowing artifact

35

What is frequency compounding?

it is a technique that reduces speckle artifact and noise 

36

What is edge enhancement?

it is an image processing method that makes pictures look sharper

37

What is temporal compounding

(persistence)?

it is a technique that super imposes the current frame on previous frames to create  smoother image

38

What is fill-in interpolation?

it is a technique that fills in the missing data between the scan lines

39

What is elastography?

it takes the levels of stiffness in a structure and gives us info into the densitty (mass) of an object