Physics Ch. 15
Translating image info from real world - to computer world - and back again is a - step process
Analog; digital; 5
In early days of 2D imaging scan converters were constructed from - technology. Modern - scan converters use - technology
Analog; digital; computer
Advantages of digital scan converters
Uniformity (consistent gray scale quality throughout image) Stability (doesn't fade) Durability (not affected by age or use) Speed Accuracy (error-free)
Characteristics of read magnification (6):
Uses old data Post processing Larger pixel size Same # of pixels as in original ROI Unchanged spatial resolution Unchanged temporal resolution
PACS has 3 major advantages:
Virtually instant access to archived studies No degradation of data Ability to electronically transmit images and reports to remote sites.
A - of computer memory consists of two - or 16 -
Word; bytes; bits
Characteristics of digital numbers
- relate only to the computer world - limited number choices - discrete values (for example, a weight on a digital scale may be limited only to whole pounds)
Characteristics of analog numbers
-Real world numbers (like weight or length of a string) - unlimited number of choices - continuous range of values (like 164 lbs, 163.998673 lbs, or 164.004432 lbs).
Binary numbers are based on only two choices, - or -. -- used in everyday life are based on ten choices, - through -.
0 or 1; decimal numbers; 0 through 9
1) ultrasound system - the anatomy 2) image is converted from - to - form and is stored in the scan converter 3) sonographer identifies region of interest and system - and - only - that pertains to ROI. ROI isn't rescanned
1) scans 2) analog to digital 3) reads; displays; the original data
1) ultrasound system - anatomy and creates an image 2) image is converted from - to - form and is stored in the scan converter 3) sonographer identifies ROI. At that moment, system discards all - data in scan converter 4) ultrasound system then - only - and writes new - into scan converter
1) scans 2) analog to digital 3) existing 4) rescans; ROI; data
How many possible shades of gray are displayed with 5 - of memory?
32...multiplying 2 by itself 5 times yields 32. Thus a max of 32 different shades of gray can be displayed with 5 bits
Characteristics of write magnification (6):
Acquires new data Preprocessing -- Identical pixel size More pixels than in original ROI Improved spatial resolution May improve temp resolution (if bottom of ROI is shallower than original image's depth of view)
Read magnification occurs - image data is stored in scan converter. Consists of - steps
After; 3
Data stored in the scan converter can be - between the - process and the - process.
Altered; writing; reading
1) electric signals created by transducer during reception are converted from analog to digital form by the ---- . The digital info is a string containing only - and -.
Analog-to-digital (A-to-D) converter; 0s and 1s
A computer mouse is an --- converter. Analog signals in the form of - of the mouse are - to digital form. This moves a cursor on computer screen
Analog-to-digital; motion; converted
Converting info from - to - form is advantageous because - information is far - susceptible to - . Prior to display on an - monitor, the - info must be converted back to - form.
Analog; digital; digital; less; contamination; analog; digital; analog
The - scan converter was the first type of scan converter and made - imaging possible
Analog; gray scale
5) the signal, now in - form is presented on the analog -- for interpretation.
Analog; video display
Elastogram can be combined with - images and - to add to - value of the US exam. This method has been applied to differentiate - from - lesions. Has potential as a complementary tool for diagnosis of -.
Anatomical; Doppler; diagnostic; benign from malignant; cancer
Examples of post processing actions
Any change after freeze frame Black/white inversion Read magnification Contrast variation 3D rendering
A -- is a group of - and is simply a series of - and - such as 0101010011. Digital or -- numbers are -
Binary number; bits; zeroes; ones; computer-based; binary
The word - derived from the term -- is the smallest amount of - memory. A bit is bistable, having a value of either - or -
Bit; binary digit; computer; 0 or 1
Bistable images are composed of only 2 shades --
Black and white
- determines the - of the image
Brightness; brilliance
A - is a group of eight - of computer memory such as 10011111.
Byte; bits
How are info and images stored in PACS?
Computer hard drives are the primary digital storage devices used.
3 things related to bits
Computer memory Gray shades Contrast resolution
Digital scan converters use - technology to convert images into numbers, a process called -. Image is stored in computer memory as a series of - and -. Numerical representation of image is processed and then re-translated into an - displayed on a -
Computer; digitizing; zeroes and ones; image; monitor
2) the digital info is stored in the scan converters - memory. Any processing of reflected signals before - is called -
Computer; storage; preprocessing
- determines the range of brilliancies within the image. - images, in which only black and white appear, are - contrast.
Contrast; bistable; high
Write magnification is applied during -- before - in the scan converter. Consists of - steps
Data acquisition; storage; 4
-- may be thought of as a picture divided into - of tiny dots each containing an --- or -- . The stored electron - in each bucket are read to retrieve image info.
Dielectric matrix; millions; electrical storage element; electron bucket; charges
What does DICOM stand for?
Digital imaging and computers in medicine
An iPod is a ---- converter. A digital file composed of - and - represent a song. The - are converted into analog - that create music.
Digital-to-analog; 0s and 1s; numbers; voltages
Modern flat-panels are - display devices. When using a - display device, step 4, ---- conversion isn't necessary
Digital; digital; digital-to-analog
4) digital signals can't be - displayed on analog - devices. The digital signals must be translated back into - form by a ---
Directly; display; analog; digital-to-analog (D-to-A) converter.
-- is an image processing method that makes pics look -. Computer identifies and emphasizes - edge boundaries in image. Method works by - image contrast in area - around edge. Creates subtle - and - highlights on either side of these boundaries to make them more -
Edge enhancement; sharper; sharp; increasing; immediately; bright and dark; defined
- is a dynamic technique that produces images from sound reflections in an entirely - way. Images are related to -- of tissue. Theory is that tissues will deform - following application of -. - data and ultrasound - are combined into images called -.
Elastography; new; mechanical properties; differently; force; stiffness; reflections; elastograms.
A stream of charged particles called - contain the image info in an analog scan converter. They're shot out of the -- . Larger end of the tube contains a -- or --. Electrons strike the matrix where they're stored.
Electrons; electron gun; dielectric matrix; silicon wafer
Characteristics of low pixel density
Few pixels per inch Larger pixels Less detailed image Lower spatial resolution
Fewer bits per pixel result in?
Fewer shades of gray Degraded contrast resolution
Scan converter changes the - of data. It translates the info from the - format into the - format.
Format; spoke; video
The more - in the compound acquisition sequence, the better the compound image -. Compound imaging reduces - and minimizes --. Reduced -- and reduced -- are limitations of this method. Electronic steering is used with this method.
Frames; quality; speckle; shadowing artifacts; frame rates; temporal resolution
-- is an advanced technique that reduces -- and - in ultrasound images. With this technique, reflected signal is divided into - of limited - and an image is created from each -. Images from the sub bands are then combined or compounded into a single image. When combining happens, - level is reduced.
Frequency compounding; speckle artifact; noise; sub bands; frequencies; sub-band; noise
Read magnification can be used on a - image and is --
Frozen; post processing
Coded excitation is a sophisticated method of improving image quality. It creates very long sound pulses containing a wide range of frequencies. This specially designed long pulse distributes energy over a broad frequency range. Coded pulse is strong but still keeps peak intensity below FDA limit. Improved penetration results. This occurs in the pulser. Coded excitation provides 5 important benefits:
Higher signal-to-noise ratio Improved axial resolution Improved spatial resolution Improved contrast resolution Deeper penetration
3 things related to pixels
Image element Image detail Spatial resolution
Limitations of analog scan converters
Image fade Image flicker (from switching between read and write modes) Instability (picture quality depends on many varying factors) Deterioration (image degrades as device ages)
Write magnification is characterized by:
Image used to identify ROI is discarded and all new image info is acquired. Number of pixels or scan lines in ROI image is greater than that in ROI's portion of original image The increased number of pixels in ROI improves spatial resolution. Pixels are same size in both old and zoomed image.
PACS is the ultrasound - in which images and med info are - and - on large computer network.
Laboratory; digitized; stored;
With - or zoom sonographer can - visualization of anatomical detail by - a portion of an image to fill - screen. Selected part of the image is known as --- or ROI
Magnification; improve; enlarging; entire; region of interest
Characteristics of high pixel density
Many pixels per inch Smaller pixels More detailed image Higher spatial resolution
More bits per pixel result in?
More shades of gray Improved contrast resolution
Gray scale displays -- of brightness. The - levels allow the system to assign different - shades to different echo amplitudes and - tissues of different reflectivity.
Multiple levels;numerous; gray; biologic
Number of bits to number of gray shades? Bits: 1 2 3 4 5 10 n
Number of shades of gray: 2^1 = 2 2^2 = 4 (2x2) 2^3 = 8 (2x2x2) 2^4 = 16 (2x2x2x2) 2^5 = 32 (2x2x2x2x2) 2^10 = 1024 2^n
To determine the - of gray shades that can be represented by a cluster of -, - the number 2 by - the same number of times as there are -. The result is the - number of - gray shades.
Number; bits; multiply; itself; bits; maximum; different
In summary, - is the physical computer -. - is the set of - that allows the components of network to -
PACS; network; DICOM; rules; communicate
PACS stands for?
Picture archiving and communications system
From the term -- the pixel is the - building block of a digital picture. When a picture is divided into a grid, each individual box is a -. At any instant in time, the entire pixel is - shade of gray
Picture element; smallest; pixel; single
-- is the number of picture elements per inch
Pixel density
2 important elements of digital scan converters are:
Pixels Bits
- is the manipulation of image data -- in scan converter. The sonographer can control it. Since it occurs after A-to-D conversion and storage, all - changes can be - so initial numerical values of image data can be restored.
Post processing; after storage; post processing; reversed;
- is the manipulation of image data -- in the scan converter. The sonographer controls -. It alters image data - and can't be - or -.
Preprocessing; before storage; preprocessing; forever; reversed or undone.
3) the image info, still in digital form continues to be - by the ultrasound systems -. Any processing after - in the digital scan converter is called -
Processed; computer; storage; post processing
Two different forms of magnification exist:
Read magnification Write magnification
DICOM is a set of - or - that allows imaging systems to share - on a network.
Rules; protocols; information
Gray scale imaging was first made possible with use of -- which first - info and later - it. Storage of the image info in scan converter is called -. Later image data is - from scan converter for - on monitor
Scan converters; store; display; writing; read; display
With sector-shaped images, scan lines - at increasing depths. - or - data exist between scan lines. - is a method of constructing new simulated data to -- gaps. Goal of --- is to fill in gaps of missing data in a way observer can't -. It's a form of -. Line density - improving - resolution.
Separate; gaps; missing; interpolation; fill in; fill in interpolation; see; preprocessing; increases; spatial
Each pixel's --- is determined by the cluster of - assigned to it. With - numbers of bits per pixel, more --- appear on the image. Images with - gray shades have better --.
Shade of gray; bits; increasing; shades of gray; many; contrast resolution
Higher pixel density is achieved with - pixels. In this case, more - are required to - the image. -- improves with - pixel density and creates an image with - detail.
Smaller; pixels; create; spatial resolution; high; greater
-- is a method of using sonographic info from several different - to produce a single image. Starts by acquiring -- from - viewing angles. Frames are - to form a single real-time image
Spatial compounding; imaging angles; multiple frames; different; combined (overlapped or compounded)
The -- or image detail of an analog scan converter is excellent because of the - number of storage elements within the matrix.
Spatial resolution; large
Examples of preprocessing actions
TGC log compression Write magnification Persistence Spatial compounding Edge enhancement Fill-in interpolation
--, - or -- is an image processing method that continues to display info from older images. So the displayed image contains - from earlier frames. A - image with reduced - and higher --- ratio and - image quality is produced. Primary limitation is - in displayed frame rate which reduces --. Most - with - moving structures. - motion can't be observed accurately. All images are from the same - or -.
Temporal compounding; persistence; temporal averaging; history; smoother; noise; signal-to-noise; improved; reduction; temporal resolution; effective; slowly; rapid; view or angle
Read magnification is characterized by:
The # of pixels or scan lines in magnified image is same as in original image Spatial resolution doesn't change because number of pixels in ROI is unchanged. However, pixels are larger in zoomed image.