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Chapter 4 test

QuestionAnswer
1.What is dynamic receive focusing? Another beam former duty. After the echoes are converted back to electrical energy, the beam former performs dynamic receive focusing. Improves detail resolution
2.What are the regions of a standard TGC curve Set by the operator, object is to achieve uniform brightness across the image. Min,slope,knee,max
3.What does the pulser control? VRF=PRF and VRP=PRP Generates the voltages that drive the transducer
5.Output voltage of the pulser. as high as 100 volts
7.How do video monitors( CRTs) reduce flicker on the screen? displays every other line first(one field) , then goes back and fills in the skipped lines(second field).Alternates odd & even lines to avoid flicker
8.How many HORIZONTOAL Lines are on a CRT or television monitor? 525 lines horazontal lines
9.What does a CRT do? a tube that produces a sharply focused beam of electrons. This produces a spot of light on a phosphorcoated screen. "Generated a display w/an electron beam that painted the image in horizontal lines."
10.Echo amplitude is shown as brightness on the display.
11.DAC function converts DIGITAL to ANALOG So that voltages will be used for the display instead of numbers (digital)
12.ADC function: Converts VOLTAGE from ANALOG to DIGITAL form, All components use analog Except of Memory.
14.What do bits/pixel tell us? shades of gray, contrast resolution, gray scale resolution, differences in echo-strength differences between adjacent tissues
15.When an image is frozen, where is the data stored. Image memory
16.What is the job of a scan converter? To store and create each frame of information.
17.Binary system computer operated on the binary system, they recognize only 0’s & 1’s, based on #’s, Bi means 2
18.Pixel means picture element, each square on the matrix holds one piece of info & is called?
19.Spatial resolution Amount of anatomy per pixel; determined by size, size of matrix & depth. Typically .2cm of anatomy per pixel. The less the amount of anatomy per pixel the Better the spatial resolution.
20.Contrast or gray scale resolution Observe subtle echo strength between tissue, the more shades the better contrast, more bites/pixel improves contrast resolution.
21.Why is it important to have an adequate # of scan lines? Creates a much wider field of view
22.What affects frame rate? increase in depth makes FR go up. increase in focuse reduces FR, Harmonics reduces FR Color doppler, pluse wave, the more you have computer do the longer it takes.
24.How many scan lines are in a typical B scan image? 200-250 VERTICAL LINES
25.What happens with an increase of 3dB,10dB, 20dB? 3dB=2x 10dB=10x 20dB=100x brighter images
26.What info is seen on M-mode? Is it one, two, or three dimensional? Shows motion of cardiac imaging illistrates depth versus time. Is one dimensonal
27.Function of Gain ( Overall or 2D and TGC). Bosting and amplifing your echo, when you increase your overall gain it amplyfies overall gain top to bottom. TGC only increases echo brightness at certain depth ( you make it)compensates for depth
28.What is GAIN and what is the formula for GAIN? the ratio of output to input electrical power, Brighter or darker image. Formula: Output divided by input = gain
29.What does GAIN compensate for Attenuation
30.What are decibels the units for? ratio (gain & dynamic range)
31.What is Dynamic Range? the ratio of the largest to the smallest amplitude (or power) that a system can handle, relationship between weakest & strongest (dB) Compression reduces this
32.What is Persistance and how does it affect the image? Averaging of sequential frames together to provide a smoother image. Reduces speckle which improves dynamic range and contrast resolution
33.B-Color Is a form of postprocessing that improves contrast resolution by assigning colors, rather than gray shades, to different echo strengths.
34.Parts of the Beam Former 1.Pulser 2.Pulse delays 3.T/R switch 4.Amplifiers 5.Analog/Digital converters 6.Echo delays 7.summer
35.Parts of the Signal Processor 1.Bandpass filtering 2.Amplitude detection 3.Compression ( dynamic range reduction)
36.Parts of the Image Processor 1.Scan Conversion ( memory) 2.Preprocessing 3.Persistence 4.Panoramic imaging 5.Spatial compounding/cross beam 6.3D acquistion 7.Storing image frame Cine Loop,post processing,gray scale, color scale, 3D presentation, ADC
37.Filtering Eliminates frequencies outside the echo bandwidth while returning those that are most useful in a given type of operation. such as CT, scanner, artifact ect..
38.Types of Harmonic Imaging and advantages and disadvantages Lateral resolution= beamwidth Adv=helps w/borders Dis=decreases axial resolution uses pulse inversion technique to help w/axial resolution increase frequency=better resolution
What is the function of compensation? Reduces the dynamic range largest to smallest Compensates for attenuation (because reflectors or echoes from a greater depth are attenuated more than echoes from a shorter depth.
what is the function of rejection? Getting ride of info that it does not want. Throws it out
When talking about time gain where would you need to amplify echoes the least? Nearfield
Which will penetrate the deepest? Low frequency transducer
Know what the pulser does? sends the electrical voltage controls the PRF & PRP amplitude & intensity are controled by pulser increase amplitude the more intense= amplitude square
What does the D-modulation due? Change radio frequency to video form. changes neg to positive smoothing makes it look like a box detection/reflection same thing
Why do we need to have a compression function on our computer It controls dynamic range ( largest vs smallest)w/out it the display can only show about 100dB, Squeezes everything together for display.
Dynamic range question on test
Two types of amplification 2D & overall gain. amplify all echos at the same time. TGC we decide where we want it
What so we display on a CRT or TV Our image, anything that can be put together in a signal display, V-mode,2D, M-mode, A-mode
Bit / pixel means Improves contrast resolution
If we hit the freeze botton where does it go? Memory
Binary #'s based on the #? two
Decimal is based on the #? 10
Number of scanlines in image improves what? Resolution or ablity to resolve what we see
What happen with 3,10,20 dB
If we have a 5bit/pixel, how much gray do we have? 32
Rejection button eliminates? Low level echoes, noise, dynamic range
Function of decibles
23. cont:B-mode brightness mode; turns b mode on its side (tops of the peaks 2 D imaging
23.Cont: A-mode amplitude mode; used in opthalmology
23.Cont M-mode motion mode; used in cardiac imaging, illistrates depth versus time
What is the dynamic range of demodulator 20dB
What is the dynamic range of Amplifier 100-120dB
What is the dynamic range of Display 20dB
What is the dynamic range of the Compensator Compensator 50-100
What is the dynamic range of the Transducer- unlimited
What is the dynamic range of the Pulser does not have one
What is the dynamic range of the Compensator 50-100
13. What is Postprocessing Post= everything done w/echoes AFTER they are stored in memory. Read magnification, measurement. ect
13. What is Preprocessing PRIOR to being stored in memory. such as gain, focus, all receiver functions Write magnification
Is the scan converter a computer? Yes
Increases all amplitudes? Amplification
Reduces noise Filtering
Converts pulses form radio frequency to video form Detection
Decreases dynamic range Compression
Created by: yovana2011
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