Doppler ultrasound blood flow detector???????

[johnseven]

Re: I NEED INFORMATION ABOUT FlOW SENSORS

Hi,

i need some information (lectures,ebooks,...)about mems based flow sensors.

would you please kindly help me?

mems123

ironjaycuttler

input for your project ideas:
One commercial medical ultrasound apparatus uses 14 bit A/D converter to
digitize the echo and then hi speed DSP to do the analysis.
That's essentially a DSP version of "zero IF" conversion.
Nice thread
j7

 

[ironjaycuttler]

Sorry

Well i had problems to access to my count!!!!! answer to your question i will use to DSP to but the problem that i have is in the analogic part, only i know that i will use the A/D 12 bit resolution for DSP and i will use FFT transfrom fourier fast for i can get the spectrum of this signal but i can't tell u more coz i have in the analogic part sorry!!!!

 

[sibi]

A prototype for sale

Check this site for a complete CW doppler prototype system. The engineer is willing to sell the entire IP on a non-royalty basis.


**broken link removed**

Hope that helped to speed up your project.

 

[ironjaycuttler]

diode mixer

Well i have investigated more about my work and i found that i must work with ultrsoaund well let's start for i can know about the direcction of the blood flow i must work with quadrature detection well this is a a phase sensitive demodulation technique where separates the complex demodulated signal into two components (the real and imaginary parts) which are 90° out of phase with each other. well of course the function of this signals are multyplied but the signals when are into a diode mixer are sum or difference and the output of the diode appear spectrum of this sum or differentce is that correct???? the diode mixer nte112 can help me in my work??? someone have one circuit that can post here??? well here i attachment one file where i want simulate the blood flow of course i want know the dimentions of the system for example if i can work with another substance different to blood that have the same density that blood??? and the dimention of tube of damper to container of blood??? and what type of material can be this tube ??? really i need help here

 

[Ratburn]

simulating blood flow

Ironjaycuttler, you can use whole milk to simulate blood for doppler ultrasound measurements. The fat globules in the milk reflect the ultrasound.

 

[jourval]

Hi, ironjaycuttler


Check AD630 balanced mod/demod. Fine chip!
Some years ago I built on his base blood flow detector
may be not best one, but cheapest one - it is sure.
pay attention, if you use relatively low freq. -
your filters will be bigger, but relative[/u] freq. deviation
will be bigger too, so it is more easy to detect signal.
BTW - it will not be sinus at all- it will be triangle pulses,
delayed to electrocardiograph pulse (the delay depend on measuring
place). and especially from triangle form and his slope
you get information about local vascular status !

 

[ironjaycuttler]

What about doppler shift????

Hello friends!! and thanks for answers u really help me very much and of course i have the RF amplifier and the mixer, well i only built a balanced mixer of course only with two diode mixer, well i hope can help me here coz of u know i'm working with fetal heart, well the question is what doppler shitf i can expect??? yes coz i will build a bandpass filter and i need this data, i have bibliography here and one link where on i have approximation:
For example the next URL said me that the doppler shift is around 1Hz to 10 KHz.

**broken link removed**

The next books said me the the doppler shift is around 30 a 100 Hz.
or 30 to 195 Hz

Libro: Estimation of blood velocities using ultrasound.
Autor: Jorgen Arendt Jensen.
Editorial: Cambridge, Pag. 140,141.

Libro: Ultrasonic Bioinstrumentation
Autor: Christensen Douglas A.
Pag. 187,188.

So i'm very confused about this datas, and if someone here have graph about the quadrature detector coz is the first time that i work with this method!!! so i relly nedd help

 

[ironjaycuttler]

hello!!!!

Well i was investigating about the speed of the fetal heart and i have this data the fetal heart speed is in the range of 8 cm/s 45 cm/s and this data correct??? and anybody here have graph about quadrature detector??? pls i need this information???

 

[ironjaycuttler]

another question

Well here i upload 2 images as u know i made a experiment where one hospital gave me a Doptone and of course i used a osciloscopio where i checked the oscillator signal and of course the received signal of my transductor the "imagen1" is the oscillator signal as u see the frequency is 2.25 Mhz and the voltage is 2.48 Vpp and the "imagen2" is the received signal ok i hope someone here can help me:

the question is that i have one oscillator the 4093B but this oscillator only work in DC and give 5 Vp if someone have another circuit that can give the signal that i upload

and the another question the signal of the received signal i can get or i can't see any chance in frequency the theory said me that in this signal is the chance doppler so if someone have any circuit that can capture this signal i wan't use a tank circuit with transistor where i can only capture the signal up of 2 MHz or another is use a OPAM but the opam that sells here in mexico doesn't support the high frequency if anyone have some circuit that can help me or another idea.

 

[ironjaycuttler]

the images

i forgot the images

 

[flatulent]

small differences

The Doppler shift is so small that it can never be determined from examining the received signal in the raw. You have to do one of several things.

1. use a radio receiver type circuit with a narrow band FM detector. this will give you the frequency shift but not the amplitude.

2. mix (multiply) the received signal by the transmitted signal and low pass filter to get the audio tone which is the frequency shift and is proportional to the received signal level.

It is important that whatever method you use, the output frequency response should go down to DC. In the fm receiver case the waveform will be at the frequency of the heart beat and the amplitude will be proportional to velocity. In the hetrodyme (multiply) method the signal will go to DC when the movement reverses direction.

 

[ironjaycuttler]

thanks for the advice

Well as u see the received signal is very small and is in DC so the second option that u gave is the better for me, for example i will test my work first with a human heart and after with fetal heart so the most important for me is the oscillator i know that i most excited the crystal with natural frequency but i don't know if i apply the second option that u gave me (hetrodyme) the signal of oscillator must be sine or can be square in the theory said that i can mix the signal the signal of oscillator must by sine???? and the another i don't know the velocity of heart human can some can give me this data???? coz i need this data for the band pass filter that i want put and of course i want use mixer diode the only diode that i can found in my city and i have in my hand are the NTE112 this diode can help me?????

 

[sick_man]

the best solution is to make use of a ccd and watch the iron content in the bload

a ccd when you emit a magnetic field and tune the frame refresh to

the mag field freq you will see the iron or the polerised particules etc etc
as harmonics of the mix freq
so... you can split the ccd into different colours blocks
a ccd is very large

but what realy i am trying to say
is you interprite the data by assigning a global that means tables of colour response



using algrithms to extract and extrapolate the pallet content of the ccd

this way you can like a tri corder in startrek scan the skin etc for any movement and lock on it it
this is how you would first have to "teach" such a device
allowing for colour zones to be mapped and reassigned
as a ccd processor will allow zoom etc
a tip is to scrape or rub deslove etc the poleroid film from the lense
you can even watch stelth fighters in the sky after you do this
use ones from old vid cams leaving the guts intackt
for experiments
makes a fitting end for a tired camcorder

mri is much better mapping tasks

so perhaps you should try to find a sensible magnetic system that can also chart levels of saturations etc......
using a simple inductor and a charged electros static pulse
to excite the alligned iron

so perhaps using a tube filled with flurene gas and set rectify its output from a pick up on one end and a small emiter ioniser on the other
ionising at a slow rate pwm
much like a scanner for a pc

after all if you place 4 layers of paper on top of each other you can map it all by spliting out the background

so a jadded multiharmonic static field is needed as a referance
then vecter map that
finaly ustilise fft to give any level of anything you tune to


this way you can stobe across a zone
and get analogue responses with a data constant

first applying a room constant mag field as a synro

using a system of pulse magnetic field allignment techniques
in the corners of the room

 

[flatulent]

oscillator

The oscillator in the hetrodyne method has to be of constant frequency and stay on all of the time. There are two Doppler methods. Continuous and pulsed.

You may be taking on a project larger than your resources. These instruments are developed by teams of many experienced engineers with large amounts of expensive laboratory equipment.

 

[ironjaycuttler]

thanks

Well the method that i'm working is continus doppler only i want the blood flow but tell me about the mixer theory is necessary in the oscillator a sine signal or i can use a square signal??? all articles that i read said that sine is necessary for mixer one signal, i know that this system is difficult but we want be the first people that start working with continuos doppler system and thanks monkey for your explanation!!!! the diodes that i put can work for my project????

 

[flatulent]

square waves

Square waves will work well for your project. The articles use sine waves because the math is easier. In your system the transducer will turn the square wave into sine waves of sound.

 

[ironjaycuttler]

Well if i want put my oscillator to connected to transducer i won't have problem with the impedance of this cirstal???? coz i have the problem that i connected my oscillator to cristal and the voltaje donw my friend said me that i need a follower voltage but the Opam doesn't support the high frequency so what i can i don in this case?????

 

[flatulent]

adjust frequency

You need to adjust the frequency of the drive for the value that makes the sould out the largest. This may load down your generator and require higher drive capability. There are ICs that have gain of one and large current output.

 

[ironjaycuttler]

Can u tell me the common IC's that i can use???? thanks for the answer

 

[flatulent]

national part

**broken link removed** is an example of a buffer with 200 mA output capability.

If you are driving the transducer from a square wave, you can make a CMOS type circuit from power MOS transistors and drive with that.