Science topic

Doppler Ultrasonography - Science topic

Ultrasonography applying the Doppler effect, with frequency-shifted ultrasound reflections produced by moving targets (usually red blood cells) in the bloodstream along the ultrasound axis in direct proportion to the velocity of movement of the targets, to determine both direction and velocity of blood flow. (Stedman, 25th ed)
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Hello everyone,
I hope you are doing well.
I am using a Vantage Verasonics Research Ultrasound System to do Ultrafast Compound Doppler Imaging. I acquire the beamformed IQData with compounding angles (na = 3) and ensemble size of (ne = 75) which are transmitted at the ultrafast frame rate (PRFmax = 9kHz) and (PRFflow = 3kHz). Can I used the Global SVD clutter filter to process the beamformed IQData instead of conventional high-pass butterworth filter.
Your kind responses will be highly appreciated.
Thank you
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From one of the best group in the field :
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One of the medical ultrasonic imager gives line disturbance(Probably from a LED Source.
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That is so general question which will lead you to get more general answer. Being more specific would help a lot. Understanding the source of the problem is the first step you can do. Then having some ideas about how does it influence the ultrasound probe? If you say that it is the LED source causing this problem, try to cover it!! ;)
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I recently register a clinical trial in patients with liver cirrhosis. One of the study variables is hepatic vein velocity. There are three hepatic vein and determine hepatic vein velocity is possible to all three veins and in different regions (i.e. proximal to ivc or distal or in sinusoids)
Which hepatic vein velocity is more reliable in cirrhotic patient for determine of hepatic vein velocity? Which section of vein is beter for determine this value?
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The left hepatic vein can sometimes be harder to profile if the liver is echogenic and the patient is large. But no difference in the middle and right that I am aware of.
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Hello,
I am working on a thesis project and I would like to analyse a number of waveforms obtained via ultrasound doppler.
Essentially, I have jpeg. files of the doppler trace but currently unsure how to calculate the area under the curve to determine mean height velocity in an easy, automated way. I thought some sort of program that can pick up the colour differences? And then allow me to have a scale set for both the x and y axis.
I have looked into programs to draw the area manually however this may have significant error.
I have attached a file for reference (see trace at bottom of image).
Thanks,
Rachel.
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Hi. Do you use artificial intelligence for this measure?
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Ultrasonic waves cause leukemia cancer,  is it true?
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Please remember that continuous wave ultrasound at the focal point of a transducer in a fluid medium like tissue culture or flask can generate fluid streaming and depending on the conditions cavitation which can be locally destructive. This is not relevant to pulsed wave ultrasound used medically for diagnostic studies in intact bodies. 
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In Doppler ultrasonography, be it umbilical artery ultrasound or transcranial Doppler the focus is always on the maximal blood flow velocity, i.e. on the envelope of the spectrogram (see attached Figure). 
Why is this the case and what are the underlying assumptions?  By this I mean, why are we not interested in e.g. the mean flow velocity? I feel the 'maximum' is quite hard to define since the transition region is quite blurry
One assumption, I guess, is that in the insonated vessels such as the middle cerebral artery blood flow is more or less laminar. But still, why the max. velocity?
Thanks a lot!
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Federico,
If you are interested in flow volume, yes, the systolic diameter is the significant one, as most of flow occurs during the systolic phase. Accurate absolute flow volume, however, is rarely of clinical interest: person-to-person variation, as well as the impedance of the vasculature, varies so much that there is no "correct" volume flow like 37C for temperature. What is generally clinically significant are  gross changes, e.g. no flow indicating a blockage, or high flow indicating a hemorrhage, or relative changes, e.g. change in cerebral flow while holding your breath.
Various methods have been proposed for determining the lumen. One method that is appealing to engineers, is to use a narrow beam, and then a beam wide enough to ensure full insonation of the vessel, and look at the difference in backscattered energy at the same distance (so the attenuation is the same); if you know the diameter of the narrow beam, the ratio of the wide to narrow backscatter energy times the diameter of the narrow beam gives the lumen cross-section. (To do this right you must take into account the non-uniformities of the beams, so its not so simple -- or often used.)
See David Evans's publications for real expertise in this and other areas of transcranial Doppler measurements.
Regards,
David
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I would like to do renal doppler ultrasonography after abdominal insufflation with carbon dioxide but the hyperechoic gas inside the abdominal cavity makes this procedure impracticle. I would like to share the experience of anyone who has successfuly conducted intraoperative renal ultrasonography during laparascopy to overcome this problem.
Dr.Davoud Kazemi
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Since the kidneys are retroperitoneal structures, air will stay anterior to them and they will be visible from a posterior approach without reverberation artefacts. You willl obviously not be able to use an anterior or lateral approach.
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Hey, I have 2 pairs of PZT crystals (Piezoelectric) fixed to a tube in which water flows. The Transit time, or time from input transmitter (>500 KHz) to output receiver is to be measured. The time Along the flow is smaller and time Against the flow is larger. This time difference gives Velocity.
1. When I give a Sine input to both the Tx, I am getting the same phased output at Rx, Without any delay, or sometimes a sudden unmeasurable change of phase.
2. This happens for a pulse also
(The tubes are of resin and steel and have thick walls)
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Several good answers here.  For a minimal TOF measurement in a fluid you need to have several (more than 2-3) wavelengths  of travel in the fluid, though with correlation you can improve this at the expense of more complex signal processing.  if the tube bore is too small to permit this, then you must position the transducers such that beam reflections are used between the transmitter and receiver, i.e. single reflection V path, 3 reflection W path.   The transducer design is really important in all this.   The main points are
1. ensure a single mode (mentioned above) is transmitted into the pipe wall.   When an acoustic pulse encounters an interface between two materials of different acoustic impedance (plastic vs steel for example) refraction occurs which bends the path according to Snells law.  What also happens is that two or more vibrational modes are generated.   Most commonly a longitudinal wave (vibration along axis of propagation) will create a Shear wave (vibration perp to axis of propagation).  these wave travel at different sound velocities and can arrive at your receiver in overlapping fashion, corrupting the measurement.   With knowledge of the material properties of the pipe and transducer you can select a transducer angle that will produce only a shear wave.  this works by using a steep enough angle to exceed the critical angle of the LONG wave.   there is a calculator for this here:   http://alturl.com/qpsw9
2.  You also need to ensure sufficient energy is coupled into the pipe wall.  This means the acoustic impedance of the transducer facing material (matching layers or delay line) has a sound speed very close to the pipe material.  if not, then most of the energy will be reflected instead of transmitted at both the receive and transmit sides of the system.  
3.  You want a narrow unfocused beam so that the energy goes where you want.  a small crystal is a bad choice.  A point source is completely omnidirectional while a large surface is completely directional.  so you need to use the largest crustal that is practical for the geometries you are working with.   It is not uncommon to see 3-4" diameter transducers used in large pipeline applications for example.
4.  If you are doing time domain processing, a simple envelope detector (precision rectifier followed by an integrator) can be fed into a PLL along with the transmit (reference) signal to generate the TOF error voltage.  from there it is trivial to measure the voltage and convert it to flow.
If you are attempting to build a general purpose instrument that can handle multiple pipe sizes, fluid types, etc the complexity goes up from here.   These are just the basics required.
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Answers and pictures would be great.
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Dear Ehab,
I just wanted to add
duplex uses pulsed wave Doppler techniques
one single elements transmits the US wave and receives it
in contrary to continuous wave Doppler
here you have to 2 elements 
one is sending - one receiving
Doppler was from Austria and described the Doppler effect in 1843 in prag
New US systems use Duplex only
color, power or spectral wave Doppler
best regards
ferdinand
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I am trying to generate shear waves of significant amplitude and penetration depth using single element transducer rather than using phased array probe as proposed by the SSI and ARFI-shear wave techniques.  
If there is any specific transducer, please suggest me or if there is a chance of using Therapeutic transducer ?
Regards
Safeer
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All you can do with a single element transducer is generate shear waves near the focus.  You would need a second transducer to track the shear wave and calculate displacement/speed.  The Olympus transducer at 2.2 MPa should be fine for generating shear waves (use ~1 ms pulse duration at a low duty cycle). A phased array can be used to both generate and track shear waves. 
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I need to perform breast ultrasound, benign and malignant.
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Hi...I am not sure if it will help you a bit....However, I can suggest you two websites with some US images of the breast, though they do not provide a real database: http://www.medison.ru/uzi/eng/all/mammography.htm