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67 Cards in this Set

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what is registration
Registration is the spatial orientation of the beam.
explain the SUAR system?
-consists of two rowes of fine wires imbedded in a perspex block which mimics sound transmission through the human body.
-two rows of wires converge
-3 parameters evaluated=axial resolution, system uniformity,
-initially, we take care of the uniformity(set parameters to penetrate deepest wire(shouldn't change much from month to month if output and ampitude are functioning properly))
-by scanning and finding the point of convergence(where 2 rows are now distinguished as one)-this shows axial resolution
-system uniformity determines weather all transducers in a linear array are firing properly(should see an unbroken line). If several transducers are not firing, there will be a gap.-consists of two rowes of fine wires imbedded in a perspex block which mimics sound transmission through the human body.
-two rows of wires converge
-3 parameters evaluated=axial resolution, system uniformity,
-initially, we take care of the uniformity(set parameters to penetrate deepest wire(shouldn't change much from month to month if output and ampitude are functioning properly))
-by scanning and finding the point of convergence(where 2 rows are now distinguished as one)-this shows axial resolution
-system uniformity determines weather all transducers in a linear array are firing properly(should see an unbroken line). If several transducers are not firing, there will be a gap.
Calorimeter
-uses physical properties of wave propegation
-The rise in temperature is proportional to the increase in the power of the beam.
-In this gadget we have an absorbing liquid encased in an insulating tank (so that heat is not easily lost
-Temperature is accurately asssessed.
-THis temperature reading will indicate the power in the beam.
# Why are cylindrical objects placed in some phantoms?
Cylindrical objects are placed in test objects to evaluate contrast resolution.
explain how the tissue equivilant phantom tests axial resolution?
-pin arrangements similar to the AIUM test object, but often placed in near, medium and far distances from the transducer to test axial resoution at various depths.
What parameters are generally tested for 2D, and doppler imaging?
2D;
-detail resolution(axial, latereral, and elevational)
-contrast resolution
-penetration
-range accuracy

Doppler:
-Penetration(sensistivity) of PW, CW, and Color
-Range accuray of PW and Color
-Peak or mean velcity accuracy of PW, CW, and COlor
-Spectral broadening-PW
-Lateral resolution-Color
explain how the tissue equivilant phantom tests lateral resolution?
-determined by evaluatine line widths corrisponding to equally spaced rods within the test object
-measurement of the narrowest line corrisponds to the best possible lateral resolution of that system
-will indicate at what distance from the transducer the optimal lateral resolution will occur(w/ a static focal zone)
-will provide an indication of a transducer's fixed focal zone.
# How can slice thickness be evaluated?
A diagonal reflector in a test object is scanned. The width of the demonstrated beam at a given depth is the slice thickness at that depth.
# What do string test objects evaluate?
String phantoms are used to test for -beam penetration,
-determine flow directions,
-accuracy of sample volume, and -determining flow speed.
Explain the hypdrophone
-small piezoelectric element mounted on the end of a narrow tube or hollow needle. --crystal is placed in the beam path
-Varying intensities encountered in different sections of the beam produce a corresponding varying voltage which can be displayed on an oscilloscope
# Describe the construction of a SUAR test object and what information can be provided.
-consists of an acrylic or Perspex block incorporating a wedge at the bottom. (One reference describes this as a water-filled wedge.) -Sensitivity is determined when one notes the settings needed to just penetrate the back of the block. -Uniformity is judged by looking at the back of the block (acrylic/air interface) or the wedge to see if image is the same across the rectangle.
-Axial resolution is determined by the point at which one no longer identifies the anterior and posterior edges of the wedge as separate structures.
PIRTO
-particle image resolution test object
-tissue equivalent phantom in which cystic spheres are randomly placed
What are the problems with non-fluid based phantoms.
-strong specular reflectors createm blossoming causing an overestimation of peak velocity, so gains and power need to be turned down.
explain how the tissue equivilant phantom tests dot formation?
-no single dot should be >3 wavelengths in diameter
(no large blobby dots)
-large dots indicate informtion processing problems
which is the worst measrure of spacial resoluation?
lateral and elevational resolution is typically worse than axial resoluation
of what use is a beam profiler
allows evaluation of bam focusing characteristics
Name 4 ways of measuring intensity and power?
-hydrophone
-radiation force measurements
-calorimeter
-schleirin photography
# What is a hydrophone and what is its main use?
-large piezoelectric crystal which is placed in the path of the ultrasound beam
-voltage generated is directly proportional to the energy in the beam
-better in house method than radiation force measurements of output evaluation
what information does a calirimeter provide?
-indicates the output.
- A medium is placed in an insulated fluid-filled object containing a thermometer.
-The beam is passed into the medium.
- The degree of heating is directly related to the energy in the beam.
what are spacial measurements? temporal and pulse measurements
the power distribution over physical dimensions
-temporal and pulse measuements-distribution of power over time
what factors determine TI and MI?
TI:
-determined by output and transducer frequency
MI:
-determined by transducer frequency and peak rarefactional pressure(output)
what does MI depend on?
frequency and output of the system
what are the types of mechanical biological effects?
-radiation force
-streaming
-cavitation(stable and transient)
when does heating become significant in ultrasound?
-significant if it exceeds 2 degrees celsius
what is the threshold for fetal anomolies over extended periods of time?
41 degrees
explain streaming
-excessive radiation can show flow within a medium
-can cause sheer(rectangular book becomes rhobic w/ sheer foce) or tearing stress
ODS
output display standard
-displayed as MI and TI=take a number of factors into account to display potential heating and mechanical pressures
explain biological studies on cells?
-some reports of cell damage due to the use of medical ultrasound, but these studies have not been able to be independently confimed
-cell studies are significantly different from human cells, so even w/ independant confirmation of harmful effects, reproducing this in the human population is extremely difficult
-cells are particularly susceptible to changes in heat
explain transient cavivation
aka collapse cavivation:
-bubble collapses as a reaction to the changing mechanical pressures
possible results:
-shock waves
-extremely high temperatures
-light emmision(in clear fluid)
epidemiological studies
-evaluations of the effects of ultrasound in a stated population
-12 studies have been carried out, and have not revealed any adverse effects of u/s
explain biological studies on plants?
-useful to study effects on plants because gas filled channels btw cell walls allow studying cavitation.
-the only irreversible effects on plant cells has been cell death.
-other effects are:
-chromosomal abnormalities
-mitotic index reduction
-growth rate reduction
what factors are used to calculate TI?
-frequency, aperture, and internsity
what ways can TI be expressed?
TIS-thermal index in soft tissue
TIB-thermal index in bone(at or near the focus after travelling though soft tissue)
TIC-thermal index in cranial tissue(when transducer is close to bone)
what are the wave variables? which variable are the main concern for biological effects?
-pressure
-density
-temp
-distance
(temperature and distance are the main concern for biological effects)
how is mechanical index calculated?
-Peak rarafactinal pressure/ square root of center frequency of the bandwidth
explain the development portion of transparency film processing?
-converts exposed ares of the film to regions of concentration on the film
-phenidone, and hyproquinone are the active chemicals which accomplish this

Chemicals which perform ancillary functions:
-sodium carbonate-controls hydrogen ion concentration
-sodium sulphate-inhibits oxidation
-potassium bromide-restrainer-to limit reaction rate
-a hardener to control swelling of the emulsion
explain photothermography
-1995
-processed by a heating method
-chemicals in emulsion are heat sensitive
-when a latent image is generated in the normal fashion, film is carried across a heated drum
explain thermal silver behenate
-heat sensitive coating on a base
-laser heats the coating which results in silver deposits in that region
-intensity of laser determines optical density in a given region
explain heat-sensitive paper
-Chemically-treated paper is transported past a CRT displaying a single echo train. --The echo train changes as paper moves past the CRT.
-Heat forms deposits of silver on the paper.
-Variations in heat forms different shades of gray.
explain dye sublimation
-dye is coated onto a ribbon
-as dye is heated, it transforms(sublimates) into gas and transfers to the films
-density depends on how much dye was depositied which is dependant on how much heat is applied.
video printers
-Dyes are heat activated and are transferred to paper without the need for chemical processing.
-Separate ribbons are needed for each of the primary colours and are placed on the paper separately.
- colours are transferred to the paper by a sublimation process.
explain how the VHS works?
-most common method of recording motion until DVD's came around
- A 1/2-inch diameter tape is coated with magnetic particles
-This coating consists of dipoles which are subjected to a magnetic field.
-When recording, the tape is transported past two writing heads which produces a magnetic field in the region of the tape.
-The magnetic field varies according to the brightness changes on the image(variations are stored in oblique tracks on the tape)
-Audio information is recorded on a linear track.
-During playback, magnetic variations are read and changed into the varying brightnesses which make up the image.
explain dye sublimation
-dye is coated onto a ribbon
-as dye is heated, it transforms(sublimates) into gas and transfers to the films
-density depends on how much dye was depositied which is dependant on how much heat is applied.
multiformat camera?
-photographic method which uses transparency film to place a selected number of images on a transparency film
explain thermography
-layer of heat-sensistve material consisting of devleloper and dye in separate minicapsules is coated onto a film base
-heat from laser causes walls of the devloper and dye capsules to become permeable
-they combine to form a black blob
-the amount of heat determines how dark the blob gets
-when heat is removed, capsules become impermerable again
-since this system is not light sensitive, a dark room is not required
Which are the two main components of transparency film.
base and emulsion
explain the fixing portion of transparency fild processing?
-an acetic acid solution is used to stop the devlopment
-sodium thiosulfate helps remove underdevloped halide grains
-aluminum chloride hardens
-sodium sulfite preserves
name some dry processing systems
-photothermography
-direct thermal silver behenate
-thermography
-dye sublimation
explain the basic function of a multiformat camera?
-cathode ray tube directs the image toard a lens which positions an image over a designated section of the film
-the film/lens/CRT relative postitions are adjusted so that images are correctly placed on the film.
What is a 'true colour' memory?
24-bit memory
some have said that 2D has a 3rd non-spacial dimension. What are they talking about?
brighness
what 3 ways can 3D information be displayed?
-Multiplanar formattting-viewing a single plane using perpendicular planes anywhere in the 3D volume
-surface rendering-depicts the surface of objects for display
-volume rendering-a 2D image based on inside the 3D volume
What are the limitations of 3 and 4D? why has it been slow to be accepted in some cases
-its time consuming to learn
-requires huge amount of computer memory
-lack of orthogonal scan planes
-slow frame rates
-limited scan lines
-long computational times
-many factors contribute to the echo induced signal making data manipulations difficult to apply.
In transient echo imaging, what causes the chaotic appearances that helps track blood flow?
The disintegration of the gas bubbles.
Compare the terms linear and non-linear propagation
Linear propegation:
-When low pressure fundamental frequencies are used, fundamental frequency echoes are returned.

NOn-linear propegation:
-When high pressure fundamental frequencies are used, various harmonic frequencies are generated.
why does the effective beam width narrow when harmonics are generated?
-as pressures increase, output is increased, and there are more harmonics generated.
-only areas of the beam w/ sufficient energy will genreate harmonics
-this results in a narrow effective beam.
What is the down-side of using non-pulse inversion harmonics?
Because pulse lengths are increased to reduce bandwidths, there is a concomitant reduction in axial resolution.
One type of harmonics is considered a filtering technique and the other a subtraction technique. Which is which.
Regular, non-pulse inversion=a filtering technique because the fundamental is filtered out leaving only the harmonics.

Pulse inversion=a subtraction technique because the fundamental frequencies are removed from the bandwidth by cancellation.
what is another name for transient echo imaging?
stimulated acoustic emision(SAE)
what is transient echo imaging? what is it useful for?
-under the influence of ultrasound, gas bubbles can break allowing gas to diffuse into the surrounding tissues quite easily
-useful for slow moving blood
There is something to be given up when using each of the two types of harmonics. What are they?
-In regular harmonics axial resolution is worse than with pulse inversion.
-With pulse inversion, frame rate is lower due to the increased dwell time.
Why are longer pulse lengths generally used in non-pulse inversion harmonics?
Both transmitted and received bandwidths must 'fit' within the transducer bandwidth.
- In order to cause a narrowing of these bandwidths, the pulse lengths are increased.
HOw is information w/ harmonics processed?
-w/ regular harmonics, both fundamental and harmonic frequcny must fit into the transducer bandwidth w/out overlapping, so longer pulses are used
-as pulselength increases, bandwidth decreases.
-amplifier is tuned to process higher frequencies, so it filters out the fundamental frequencies leaving the harmonics to be displayed
what are the advantages of harmonic imaging?
-decreased clutter, grating lobes, side lobes, etc.
-decreased reverberation
-reduction of acoustic noise
-fluid spaces have less fill in
-improved lateral resolution due to decreased effective beam width
-effect of subcutaneous fat in lg. patients is reduced
what areas do not produce harmonics?
-peripher of a wave
-low amplitude waves
-first few centimeters
-lower pressure regions in the far field
what does generation of harmonics depend on?
-acoustic pressure
-frequency
-non-linearity co-efficient
-density of the medium
-velocity in the medium
-distance of propegation
Explain(in terms of the sinusoidal wave), how harmonics are produced?
-sinusoidal wave propigates as a series of pressure variations
-higher pressure=faster wave which results in a change in the wave shape(it's now non-sinusoidal), and generation of harmonic frequencies.
-as pressures increase(increased output), there are more harmonics genrerated.
-only areas of the beem w/ sufficient energy will generate harmonics, so there is effective narrowing of the beam.