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35 Cards in this Set
- Front
- Back
- 3rd side (hint)
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Bistable |
Images that are composed of only 2 shades: black and white |
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Gray Scale Display |
Present multiple levels of brightness (white, light gray, medium gray, etc). |
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Display Contols |
1. Contrast determines the range of brilliancies within the displayed image. Bistable images, in which only white and black appear, are high contrast. 2. Brightness determines the brilliance of the displayed image. |
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Scan Converters |
First store information and later display it. Translate the information from the spoke format into the video format. |
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Analog Numbers |
“Real world” numbers that are found in our everyday lives. Can have an unlimited and continuous range of values. Ex. 163.998673 instead of 164 |
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Digital Numbers |
Associated with computer devices. Have only discrete values. Ex. 163 instead of 163.12 |
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Analog Scan Converter |
A funnel-shaped vacuum tube with an electron gun located within its smaller end. A dream of charged particles, called electrons contain the image information, and are shot out of the electron gun. The larger end of the tube contains a dielectric matrix or silicon wafer. |
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Spatial resolution |
Image detail |
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Limitations of analog scan converters |
• image fade - stored charges on the silicon wafer dissipate over time. • image flicker - caused by switching between read and write modes. • instability - picture quality depends on many factors including length of use, room temperature, and humidity. • deterioration - image degrades as the device ages. |
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Digital Scan Converter |
Use computer technology to convert images into numbers, a process called digitizing. |
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Advantages of digital scan converters |
• uniformity - consistent gray scale quality throughout the image. • stability - does not fade or drift. • durability - not affected by age or heavy use. • speed - nearly-instant processing. • accuracy - error-free |
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Two important elements of digital scan converters |
1. Pixel 2. Bit |
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Pixel |
The smallest building block of a digital picture. |
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Pixel Density |
The number of picture elements per inch |
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Spatial resolution |
Improves with high pixel density and creates an image with greater detail |
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Bit |
The smallest amount of computer memory. Is bistable, having a value of either 0 or 1. |
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Binary Number |
A group of bits and is simply a series of zeros and ones, such as 010101010011. |
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Decimal numbers |
Used in everyday life, are based on ten choices, 0 through 9. |
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Byte |
A group of eight bits of computer memory |
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Word |
Computer memory consists of two bytes or 16 bits |
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Calculating the number of gray shades |
Multiply the number 2 by itself the same number of times as there are bits. Result is the maximum number of different gray shades. |
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Preprocessing |
The manipulation of image data before storage in the scan converter. Receiver function. Write zoom |
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Elastography |
Produces images from doing reflections in an entirely new way. Tissues will deform automatically. Estimates of tissue stiffness are obtained. |
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Postprocessing |
The manipulation of image data after storage in the scan converter. Read zoom |
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Write magnification |
Applied during data acquisition, before storage in the scan converter. |
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Read Magnification |
Occurs after the image data is stored in the scan converter. |
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Coded Excitation |
A sophisticated method of improving image quality. Creates very long sound pulses containing a wide range of frequencies. Occurs in the pulser. Improves resolution. |
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Spatial Compounding |
Using sonographic information from several different imaging angles to produce a single image. The more frames in the compound acquisition sequence, the better the compound image quality. Electronic steering of the sound beams is used in compound imaging. Available only with phased array transducers. |
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Frequency Compounding |
An advanced technique that reduces speckle artifact and noise in ultrasound images. |
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Edge Enchancement |
An image processing method that makes pictures look sharper. |
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Temporal Compounding |
An image processing technique that continues to display information from older images. Frame averaging |
Persistence or temporal averaging |
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Elastography |
Produces images from doing reflections in an entirely new way. Tissues will deform automatically. Estimates of tissue stiffness are obtained. Applies to differentiate malignant from benign lesions. |
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PACS - picture 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. |
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PACS three major advantages |
• virtually instant access to archived studies. • no degradation of data, which often happens over extended time periods with analog archiving. • “store and forward” telemedicine, the ability to electronically transmit images and reports to remote sites. |
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DICOM - digital imaging and computers in medicine |
A set of rules, or protocols, that allows imaging systems to share information on a network. |
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