Ch 15 Displays and Image Processing

images composed of only 2 shades; black and white images

bistable

2 user controls that alter characteristics of displayed images:

contrast and brightness

determines the range of brilliances within the displayed image

contrast

more shades of gray =

low contrast

bistable images are ____ contrast

high

low contrast = _______ contrast resolution

high

determines the brilliance of the displayed image

brightness

- stores digital image info to later display it

- changes format of data

scan converter

what created grayscale imaging

scan converter

storage of information in converters is called

writing

real world numbers found in our everyday lives; have an unlimited and continuous range of values

analog numbers

numbers associated with computer devices that have discrete values

digital numbers

analog scan converters have excellent _______ resolution

spatial

spatial resolution =

image detail

computer technology that converts images into numbers

digitizing

- image fade

- image flicker

- instability

- deterioration

limitations of A-D converters

- uniformity

- stability

- durability

- speed

- accuracy

advantages of D-A converters

with digital scan converters, the image is stored in computer memory as a series of

zeros and ones

smallest building block of a digital picture

pixel

a pixel is a single shade of

gray

the number of pixel elements per inch

pixel density

low pixel density = _____ pixels per inch

fewer

low pixel density = _____ spatial resolution

poor

the smallest amount of computer memory

bit

a bit is bistable -- it has a value of either ____ or ____

0 , 1

a group of bits; a series of 0s and 1s

binary number

group of 8 bits

byte

group of 2 bytes (or 16 bits)

word

each pixels shade of gray is determined by the cluster of ____ assigned to it

bits

fewer bits per pixel = ______ shades of gray

fewer

any processing of the reflected signals before storage

preprocessing

any processing after storage in the digital scan converter

postprocessing

alters image data and cannot be reversed or undone

preprocessing

changes can be reversed; alterations are done to a frozen image

postprocessing

write magnification occurs during

preprocessing

read magnification occurs during

postprocessing

enlarging a portion of the image to fill the entire screen

magnification (zoom)

magnification that occurs after image data has been stored in the scan convertor

read magnification

the ROI (reason of interest) is not rescanned

read magnification

with read magnification, the number of pixels/scan lines in the magnified image is _____ as original image

the same

read magnification _____ (does/doesn't) change spatial resolution

does not

with read magnification, the pixels are ____ in the zoomed image

larger

magnification that occurs during data acquisition, before data is stored in the scan converter

write magnification

with write magnification, the number of pixels/scan lines in the ROI image are ______ the original image

greater than

write magnification _____ spatial resolution for the ROI

improves

write magnification may improve ______ resolution

temporal

magnification that creates a better zoomed in image =

write

creates very long pulses containing a wide range of frequencies --- distributing energy over a broad frequency range

coded excitation

coded excitation occurs in the

pulser

coded excitation _____ penetration

improves

produces an image with a wider field of view; old info from previous images are retrained and new echoes are added to the image in the same direction as the scan plane is moving

panoramic imaging

panoramic imaging is a ________ process

pre processing

A method of using sonographic information from several different imaging angles to produce a single image

spatial compounding

- reduces speckle and shadowing artifacts

- reduces frame frate/temp res

spatial compounding

spatial compounding is possible with ______ only

phased arrays

speckle reduction _______ dynamic range and contrast resolution

improves

Reflected signal is divided into sub-bands of limited frequencies and an image is created from each sub-band. Images from the sub-bands are then combined into a single image

frequency compounding

reduces speckle and noise

frequency compounding

image processing method that makes pictures look sharper

edge enhancement

AKA persistence or temporal averaging

temporal compounding

An image processing technique that continues to display information from older images. A number of previous frames are superimposed on the most current frame

temporal compounding

temporal compounding creates a _______ image

smoother

temporal compounding is good for _______ structures

stationary, slow moving

temporal compounding ______ frame rate/temporal resolution

reduces

- reduced frame rate

- reduces noise

- smoother image

persistence

a method of constructing new simulated data points to fill in the gaps between scan lines at increasing depths

fill-in interpolation

what display technique does not reduce speckle or noise?

fill in interpolation (only improves spatial res)

fill-in interpolation _____ spatial resolution

improves

dynamic technique where estimates of tissue stiffness are obtained and combined with ultrasound reflections

elastography

operative dependent method of elastography

strain (SE)

elastography that is qualitative

strain (SE)

AKA transient elastography

shear wave (SWE)

elastography that is quantitative

shear wave (SWE)

Digital ultrasound lab where images and additional medical information are digitized and stored on a computer network

PACS

A set of rules that allows imaging systems to share information on a network

DICOM

preprocessing occurs

when the patient is scanned

postprocessing occurs in the

A-D converter