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SPI Chapter 15
Displays and Image Processing
| Question | Answer |
|---|---|
| what are bistable images composed of? | black and white |
| what are the are the 2 display controls? | contrast and brightness |
| what is contrast? | range of brilliancies with in displayed image (black and white = high contrast)(many shades of gray = low contrast) |
| what is brightness? | determines brilliance of the displayed image |
| what does the scan converter do ? | translate spoke format into video format |
| what does the scan converter initially do? | store information and later displays it |
| what is the scan converter's format? | pulses |
| how does the monitor display the scan converter? | horizontal lines |
| how do we use modern digital scan converters? | by computer technology |
| In the early days, how did we use scan converters? | by analog technology |
| what are analog numbers? | real world numbers/continuous values |
| what are digital numbers? | associated with computer device/discrete values |
| what was the first type of scan converter? | analog |
| what is the shape of an analog scan converter? | a funnel-shaped vacuum tube with an electron gun located within its smaller end |
| what is electrons? | a stream of charged particles that contain image information |
| where are the electrons from? | they are shot out of the electron gun |
| What does the larger end of the tube contain? | dielectric matrix or silicon wafer |
| what is a dielectric matrix? | a picture divided into millions of tiny dots containing an electrical storage element |
| what is spatial resolution? | image detail |
| why is the spatial resolution of an analog converter excellent? | because of the large number of storage element with the matrix |
| what are the limitations of an analog scan converter? | image fade, image flicker, instability, and deterioration |
| what is image fade? | stored charges on the silicon wafer dissipate over time |
| what is image flicker? | caused by switching between read and write modes? |
| what is instability? | picture quality that depends on many factors (length of use, room temp., and humidity) |
| what is deterioration? | image degrades as the device ages |
| what is a digitizing? | converting images into numbers |
| what are the advantages of digital scan converters? | uniformity, stability, durability, speed and accuracy |
| what is uniformity? | consistent gray scale quality throughout the image |
| what is stability? | does not fade or drift |
| what is durability? | not affected by age or heavy use |
| what is speed? | nearly-instant processing |
| what is accuracy? | error-free |
| what are the two components of digital scan converters? | pixel and bit |
| what is a pixel? | smallest building block of a digital picture |
| what is pixel density? | number of picture elements per inch |
| what does spatial resolution do? | improves high pixel density and creates an image with greater detail |
| what is a bit? | smallest amount of computer memory |
| what is a binary number? | group of bits and is a series of zeroes and ones (ex. 0101010011) |
| are digital (or computer-based) numbers binary? | yes |
| what are binary numbers based on? | only 0 or 1 (two choices) |
| what are decimal numbers based on? | 0 through 9 (ten choices) |
| what is a byte? | group of eight bits of computer memory (ex. 10011111) |
| what is a word? | computer memory that consists of two bytes or 16 bits |
| what does images with many gray shades have? | better contrast resolution |
| what is the formula for calculating the number of gray shades? | 2^number of bits |
| during reception, what type of electrical signals does a transducer produce? | very low-voltage/weak and they are susceptible to noise |
| what conversion is less susceptible to contamination? | analog to digital form |
| what must happen prior to display on an analog monitor? | digital information must be converted back to analog form |
| how many steps take place for translating analog to digital information? | 5 |
| what are the first step of translating analog to digital information? | electrical signals created by transducer during reception will convert from analog-to-digital (A-to-D) |
| what are the second step of translating analog to digital information? | digital information is stored in the scan converter's computer memory (preprocessing) |
| what are the third step of translating analog to digital information? | digital form continues to be processed (postprocessing) |
| what are the fourth step of translating analog to digital information? | digital signals can not be directly displayed on analog display devices, therefore the signals must be translated from digital-to-analog (D-to-A) |
| what are the fifth step of translating analog to digital information? | the signal is now in analog form and will be presented on the analog video display |
| In modern flat-panel, which step is unnecessary? | step 4:the digital-to-analog conversion (D-to-A) |
| what is preprocessing? | before storage |
| what is post processing? | after storage |
| what consists of preprocessing? | TGC, log compression, write magnification, persistence, spatial compounding, edge enhancement, fill-in interpolation |
| what consists of postprocessing? | any change after freeze frame, black/whit inversion, read magnification, contrast variation, and 3-D rendering |
| what is magnification? | zoom |
| what are the two forms of magnification? | read and write magnification |
| how many steps does read magnification consists of? | 3 |
| what is the first step of read magnification? | the ultrasound system scans the anatomy |
| what is the second step of read magnification? | the image is converted from analog to digital form and is stored in scan converter |
| what is the third step of read magnification? | the sonographer identifies the region of interest (ROI) , and the system reads and displays only the original data. The ROI is not rescanned |
| what is read magnification characterized by? | the number of pixels or scan lines equals the same as the original image and spatial resolution does not change because ROI is unchanged |
| how many steps does write magnification consists of? | 4 |
| what is the first step of write magnification? | the ultrasound system scans the anatomy and creates an image |
| what is the second step of write magnification? | the image is converted from analog to digital form and is stored in the scan converter |
| what is the third step of write magnification? | the sonographer identifies the ROI and the system discards all existing data in the scan converter |
| what is the fourth step of write magnification? | the ultrasound system rescans only the ROI and writes new data into the scan converter |
| what is write magnification characterized by? | the image used to identify ROI is discarded, the number of pixels or scan line in ROI image is greater than the ROI's original image, and an increased number of pixels improves spatial resolution |
| what is coded excitation? | sophisticated method of improving image quality |
| what context was coded excitation developed in? | the context of bioeffects |
| who established the maximum peak for sound beams? | the FDA |
| what does coded excitation create? | long sound pulses containing a wide range of frequencies which improves penetration results |
| where does coded excitation occur? | the pulse |
| what are the advantaged of coded excitation? | higher signal-to-noise ratio, improved axial, spatial, and contrast resolution, and deeper penetration |
| what is spatial compounding? | method of several angles to produce a single image |
| what does compound imaging reduce? | speckle and minimizes shadowing |
| which transducer is used for electronic steering of the sound beams that are used in compound imaging? | phased array transducers |
| what is frequency compounding? | reduces speckle artifact and noise in ultrasound images |
| with frequency compounding, the reflected signal is divided into sub-bands of limited frequencies, how is the image created? | from each sub-band |
| what happens to the images from the sub-band? | they are combined into one image |
| with frequency compounding, what is reduced? | the noise level |
| what is edge enhancement? | makes pictures look sharper |
| how does edge enhancement work? | by increasing image contrast in the area immediately around the edge |
| what is temporal compounding? | display info from older images (history) |
| what is another word for temporal compounding? | persistence |
| what are the advantages of temporal compounding? | smooth image with reduced noise, higher signal-to-noise ratio , and improved quality |
| what is the primary limitation of temporal compounding? | reduction in the displayed frame rate, which reduced temporal resolution |
| what is persistence most effective with? | slowly moving structures |
| what is Fill-in-interpolation? | new data points to fill in the gaps or missing data in the sector size |
| what is Fill-in-interpolation a form of? | preprocessing |
| with Fill-in-interpolation, what improves? | spatial resolution and line density increases |
| what is elastography? | produces images from sound reflections in a new way |
| what are images related to? | mechanical properties of tissue |
| what are elastograms? | stiffness data and ultrasound reflection that are combined |
| in elastography's early stages, what would the sonographer do? | distort by pressing the transducer on the tissue |
| in today's elastography, what would the sonographer do? | nothing, the force of the sound beam is enough |
| what can the elastogram be combined with to add diagnostic value? | doppler and anatomical images |
| what has elastography been applied to differentiate? | malignant and benign lesions |
| what concept would elastography benefit for the diagnosis, but needs more scientific study? | cancer |
| what does PACS stand for? | Picture Archiving and Communications System |
| what is PACS? | stores images and info |
| what are the 3 major advantages of PACS? | access to archived images, no degradation of data, and can forward images/reports to sites |
| how are info and images stored in PACS? | hard drives |
| what does DICOM stand for? | Digital Imaging and Computers in Medicine |
| what is DICOM? | set of rules, protocals, that allows sharing of information (translator) |
| what is paper media? | charts with pen |
| what are advantages of paper media? | portable, does not require device |
| what are the disadvantages of paper media? | bulky, hard to store, cannot display dynamic images, difficult to make copies |
| what is magnetic media? | CDs, video tape |
| what are the advantages of magnetic media? | able to store, can record in color, can play dynamic images |
| what are the disadvantages for magnetic media? | can be erased by strong magnetic field |
| what is chemically mediated photographs? | photos, films |
| what are the advantages of chemically mediated photographs? | high resolution, color images, accepted in medical community |
| what are the disadvantaged of chemically mediated photograpghs? | bulky, hard to store, requires chemical processing, artifacts can arise from dirt or contamination |
| what is optical media? | laser/compact discs |
| what are advantages of optical media? | store huge amounts of data, inexpensive, not erased by exposure of magnetic fields |
| what are disadvantages of optical media? | requires display system, not standard format for image display and storage |
Created by:
Lazacha
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