Chapter 15 Flashcards
bistable images are composed of only 2 shades ______ and ______ (high contrast)
black and white
______ displays present multiple levels of brightness, the numerous levels allow the system to assign different gray shades to different echo amplitudes and to differentiate biologic tissues of different reflectivity
gray scale
______ determines the range of brilliancies within the displayed image
contrast
______ determines the brilliance of the displayed image
brightness
gray scale imaging was initially made possible with the use of ______, which first store information and later display it
scan converters (changes the format of data)
the scan converter translates the information from the ______ format to the ______ format
spoke, video
______ are “real world” numbers that are found in our everyday lives, they have an unlimited and continuous range of values
analog numbers (first type of can converter)
______ are associated with computer devices, have only discrete values (limited choices)
digital numbers
the analog scan converter is a ______ vacuum tube with an electron gun located within its smaller end, electrons contain information and shot out of the electron gun
funnel-shaped
the ______ may be thought of as a picture divided into millions of tiny dots, each containing an electronic storage element, the storage element charges in each bucket are read to retrieve the image information
dielectric matrix (also known as silicon wafer)
the ______, or image detail, of an analog scan converter is excellent because of the large number of storage elements within the matrix
spatial resolution
what are the limitations of analog converters?
image fade, image flicker, instability, and deterioration
digital scan converters use computer technology to convert images into numbers, a process called ______, the images is stored as a series of zeros and ones, then processed and re-translated into an image
digitizing
what are the advantages of digital scan converters?
uniformity, stability, durability, speed, and accuracy
what are the 2 important elements of digital scan converters?
pixel and bit
_____ (from the term picture element) is the smallest block of a digital picture
pixel- the entire pixel is a single shade of gray
______ is the number of picture elements per inch
pixel density
high pixel density=smaller pixels, and more of them
______ improves with high pixel density and creates an image with greater detail
spatial resolution
______ (from the term binary digit) is the smallest amount of computer memory
bit- has a value of either 1 or 0
a ______ is a group of bits and is simply a series of 0’s ands 1’s
binary number
______, which are used in everyday life, are based on ten choices, 0 though 9
decimal numbers
a ______ is a group of 8 bits of computer memory, such as 10011111
byte
a ______ of computer memory consists of 2 bytes, or 16 bits
word
fewer shades of gray, degrades contrast resolution is?
fewer bits per pixel
more shades of gray, improved contrast resolution
more bits per pixel
How do you determine the number of gray shades that can be represented by a cluster of bits?
Multiply the number 2 by itself the same number of times there are bits
What are the 5 steps in translating image information from real world (analog) to the computer world (digital) and back again?
1) analog-to-digital converter
2) the digital information is stored in the scan converter’s memory
3) post processing
4) digital-to-analog converter
5) presented on analog video display
______ is the manipulation of image data before storage in the scan converter, cannot be reversed or undone
Preprocessing
______ is the manipulation of image data after storage in the scan converter (can be reversed)
Post processing
TGC, log compression, white magnification, persistence, spatial compounding, edge enhancement, fill-in interpolation is?
Preprocessing
Any change after freeze frame, black/white inversion, read magnification, contrast variation, and 3D rendering is?
Postprocessing
With ______ (or zoom) the sonographer can improve visualization of anatomic detail by enlarging a portion of an image to fill the entire screen
Magnification
What are the 2 forms of magnification?
Read and write
_______ modification occurs after the image data is stored in the scan converter
read: 3 steps
1) US system scans anatomy
2) image is converted from analog to digital form and stored in the scan converter
3) the system reads and displays only the original data that pertains to the ROI
what is read magnification characterized by?
- number of pixels or scan lines in the magnified image is the same as in the original image
- spatial resolution does not change because the number of pixels in the pixel are larger in the zoomed image
______ magnification is applied during data acquisition, before storage in the scan converter
write; 4 steps
1) US system scans the anatomy and creates an image
2) the image is converted from analog to digital form and is stored in the scan converter
3) when the sonographer identifies ROI, the system discards all the existing data in the scan converter
4) the US system then rescans only the ROI and writes new data into the scan converter
what is write magnification characterized by?
- the image used to identify the ROI is discarded and all new image information is acquired
- the number os pixels or scan lines in the ROI image is greater than that in the ROI’s portion of the original image
- the increased number of pixels in the ROI improves spatial resolution
uses old data, post processing, larger pixel size, same # of pixels as in the original ROI, unchanged spatial resolution, unchanged temporal resolution is?
read magnification
acquired new data, preprocessing, identical pixel size, more pixels then in the original ROI, improves spatial resolution, and may improve temporal resolution is?
write magnification
what does coded excitation provide?
higher signal-to-noise ratio, improves axial resolution, improves spatial resolution, improves contrast resolution, and deeper penetration
______ is an sophisticated method of improving image quality, creates long sound pulses containing a wide range of frequencies and improves penetration results
code excitation; occurs in the pulser
______ is a method of using sonographic information from several different imaging angles to produce a single image, starts by acquiring multiple frames from different viewing angles
spatial compounding; the more frames in the compound acquisition sequence, the better the compound image quality
what does compound imaging do?
reduces speckle and minimized shadowing artifacts, reduced frame rates and temporal resolution is the limitation of this technique
______ is an advanced technique that reduces speckle artifact and noise in US images, the reflected signal from the transducer is divided into sub-bands of limited frequencies, and an image is created from each sub-band (then combined into a single image)
frequency compounding
______ is an image processing method that makes pictures look sharper, the computer identifies and emphasizes sharp edge boundaries in the image
edge enhancement
edge enhancement creates subtle ______ and ______ highlights on either side of these boundaries to make them appear more defined, works by increasing the image contrast in the area immediately around the edge
bright and dark
______, ______, or ______ is an image processing technique that continues to display information from older images
temporal compounding, persistence, or temporal averaging
with ______, a number of pervious frames are superimposed on the most current frame (the display image contains history from earlier frames)
persistence; produces a smoother image with reduced noise, higher signal-to-noise ratio, and improved image quality
what is the limitations of persistence?
a reduction in the displayed frame rate, which reduces temporal resolution; it is most effective with slowly moving structures and less with rapid moving structures
all the images used in persistence are from the _____ view, the images used in spatial compounding are from ______ views or angles
same, different
______ is a method of construction new simulated data points to fill in the gaps
interpolation- the goal of fill-in interpolation is to fill in the gaps of missing data in a way that cannot be detected by the observer
fill-in interpolation is a form of prepocessing, the line density increased, improving ______
spatial resolution
______ is a dynamic technique that produces images from sound reflections in an entirely new way, images are related to mechanical properties of tissue
elastography
what is the theory of elastography?
tissue will deform differently following the application of a force, the tissue stiffness data and US reflections are combined into images called elastograms
the tissues in elastography deformation results from the force of the sound beam itself, the elastogram can be combined with ______ images and _____ to add to the diagnostic value of the US exam
anatomical, doppler
what is PACS (pictue archiving and communications system)?
describes the digital ultrasound laboratory in which images and additional medical information are digitized and stored on a large computer network
what is DICOM (digital imaging and computer in medicine)?
it is a set of rules, or protocols, that allows imaging systems to share information on a network, when a particular US adheres to DICOM standards the system can successfully connect to a PACS medical information network
