Displays and Image Processing

Question 1

determines range of brilliances within the displayed image

Answer 1

contrast

Question 2

determines brilliance of displayed image

Answer 2

brightness

Question 3

scan converters

Answer 3

store images (write) and display them (read)
made grayscale imaging possible
translates info from spoke format to video format
can be digital or analog

Question 4

funnel shaped vacuum that shoots image info

Answer 4

analog scan converter

Question 5

benefit of analog scan converter

Answer 5

GREAT spatial resolution

Question 6

limitations of analog scan converters

Answer 6

images fade, flicker, and are unstable and deteriorate

Question 7

digital scan converters

Answer 7

convert images into numbers and store as a series of ZEROs and ONEs

Question 8

advantages of digital

Answer 8

uniform, stable, durable, instant speed, accurate

Question 9

smallest building block of a digital picture

Answer 9

pixel

Question 10

high pixel density has high _______ resolution

Answer 10

spatial

Question 11

smallest amount of computer memory

Answer 11

bit

Question 12

bits are bistable and can only have a value of

Answer 12

0 and 1

Question 13

group of 8 bits

Answer 13

byte

Question 14

2 bytes, or 16 bits is called

Answer 14

word

Question 15

when we talk about pixels, we are referring to the image’s

Answer 15

spatial resolution

Question 16

when we refer to bits, we are referring to the image’s

Answer 16

shades of gray

Question 17

images with many shades of gray have great _____ resolution

Answer 17

contrast

Question 18

how do we calculate number of shades of gray

Answer 18

2 ^ # of bits

Question 19

processing of reflected signals before storage is called

Answer 19

preprocessing

Question 20

processing after storage is called

Answer 20

postprocessing

Question 21

Preprocessing

Answer 21

compensation
compression
WRITE magnification
persistence
spatial compounding
edge enhancement
fill-in interpolation

Question 22

postprocessing

Answer 22

any change after freeze frame
black / white inversion
READ magnification
contrast variation
3D rendering

Question 23

a way to improve detail by enlarging a portion of an image

Answer 23

magnification

Question 24

selected portion of image in magnification

Answer 24

region of interest, ROI

Question 25

read magnification

Answer 25

occurs AFTER image data is stored in scan converter (post processing)
uses old data
larger pixel size
same amount of pixels as original ROI
unchanged resolution

Question 26

write magnification

Answer 26

applied before storage in scan converter (preprocessing)
uses new data
identical pixel size
more pixels than in the original ROI
improved spatial and temporal resolution

Question 27

method of improving image quality, creates long sound pulses containing a wide range of frequencies, occurs in the pulser, alter long reflected pulses into a form suitable for high image quality

Answer 27

coded excitation

Question 28

coded excitation improves ____ resolution

Answer 28

contrast, axial, and spatial

Question 29

Spatial Compounding

Answer 29

method of using sonographic info from several imaging angles to produce a single image
o Frames are overlapped / compounded
o Reduces speckle and minimizes shadowing artifacts
o Limitations – reduced frame rates, reduced temporal resolution
o Uses electronic steering
o Available only with phased array transducers

Question 30

Frequency compounding

Answer 30

reduces speckle artifact and noise in US images
o All reflected sound pulses contain a large range of frequencies, with frequency compounding the reflected signal is divided into sub-bands of limited frequencies and an image is created from each sub-band
o The images from each sub-band are then combined into a single image

Question 31

Edge enhancement

Answer 31

makes pictures look sharper by emphasizing sharp edge boundaries in the image, such as the reflecting surface between two media with different gray scale levels
o Works by increasing the contrast in the area around the edge

Question 32

Temporal Compounding

Answer 32

also called persistence or temporal averaging
o Image processing technique that continues to display information from older images
o Several previous frames are superimposed on the most current frame
o Produces a smoother image with reduced noise, higher signal to noise ratio, and improved image quality
o Limitations – reduction in displayed frame rate which reduces temporal resolution
o Persistence/temporal compounding is the most effective with slowly moving structures and less useful in rapid moving structures such as echo because rapid motion cannot be observed acuratelly

Question 33

Fill-in interpolation

Answer 33

2D images created from multiple ultrasound pulses into the body, with sector shaped images the scan lines separate at increasing depths, gaps/missing data exist between the scan lines and interpolation is a method of constructing new simulated data points to fill in the gaps
o Goal is to fill in the gaps of missing data in a way that cannot be detected by the observer
o Predicts grayscale levels of missing data
o A form of preprocessing
o As the line density increases with fill-in, the spatial resolution increases

Question 34

Elastography

Answer 34

a dynamic technique that produces images from sound reflections in an entirely new way
o Images are related to the mechanical properties of tissue
o Theory of elastography – tissues will deform differently following the application of a force
o Estimates of tissue stiffness are obtained
o Stiffness data and ultrasound reflections are combined into images called elastograms
o Can be combined with anatomical images and doppler to add to the diagnostic value of the ultrasound exam
o Can differentiate between benign and malignant tumors

Question 35

PACS system

Answer 35

picture archiving and communication system
o Describes the digital ultrasound laboratory in which images and medical info are digitized and stored on a large computer network
o 3 major advantages
1. Virtually instant access to archived studies
2. No degradation of data
3. Electronic transmit images and reports to remote sites
o Computer hard drives are the primary digital storage devices used in PACs

Question 36

DICOM

Answer 36

digital imaging and computers in medicine
o A set of rules, or protocols, that allows imaging systems to share information on a network
o Assures current imaging modalities can communicate
o Guarantees that all devices developed in the future will easily attach to the PACs network