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Spectra: Open Biomedical Imaging

Biomedical Imaging project using AC currents to do image reconstruction of conductive bodies.

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Biomedical Imaging has previously been expensive and near impossible to hack and experiment with. If more people experimented and understood how imaging works we could move it forward much faster and make these transformative technologies available to everyome. OpenEIT(EIT is for electrical impedance tomography) uses non-ionizing AC current to recreate an image of any conductive material, such as your lungs, arm or head, using the same tomographic reconstruction technique as a cat scan. The PCB is only 2" square, with bluetooth, making it a portable and hackable way to do biomedical imaging!

OpenEIT is an open source and safe way to experiment with biomedical imaging. It has reconstruction algorithms, a PCB and can re-create an image in real time. The technique is also ideally suited to machine learning applications where even more useful applications/diagnostics could be found.  

An AC wave is sent through the medium to be interrogated, and the impedance magnitude and phase is measured at the other electrode. This process is repeated around every combination of an array of electrodes, which gives us the base data to perform a tomographic reconstruction. The board is a tiny 2" square, with bluetooth, 16 bit resolution and 160kSPS sample rate. 

Below is a video of an image being reconstructed in real-time using only 8 electrodes. Notice the image moves as the shot glass rotates. Since then we've moved to a smaller PCB design with 32 electrodes! 

The picture here shows the new 32 electrode device, with a cup being rotated around in the tank. You can see it's got far better resolution than the first 8 electrode device! 

You can easily experiment with reconstruction algorithms or see if you can detect differences in materials such as fruit shown below. Each piece of fruit has it's own unique signature, based on the cell characteristics within it. 

You could also apply this to meat, bones, blood clots or tumors just as easily. 

Although this might not look like an MRI scan today, MRI started with some pretty rough images. MRI's are expensive and need a lot of personnel and equipment to keep running so a nice small portable imaging device seems generally advantageous. Below we see the first ever MRI scan of the human thorax, with a current 3 Tesla scan below it to show how far the technology has progressed. This technology is in its early stages, so it will be interesting to see where it ends up. 

Here is a link to the project on github, that contains an easy to use dashboard with reconstruction algorithms that can be run in real-time or alternatively read in offline files. There are 3 different reconstruction algorithms currently available. The true strength of this technique I think is that you can get a dielectric spectrum at every pixel, meaning you can see differences in material properties really well. 

The project from python tomographic reconstruction software to hardware and firmware are available under an Apache2.0 license on Github. Please refer to the readme to install it! Questions and collaborators welcome: 

https://github.com/openeit

  • A tale of 32 cables: Process Log

    jean3 hours ago 0 comments

    I thought I'd make this one more of a process log, showing some of the experiments and iterations along the way. 

    The idea of using a flex PCB as an electrode cable seemed efficient, as nobody likes having cables go everywhere and having them be the wrong size for your needs. This is both a good and a bad idea. It works great in tanks and I believe this is a superior method when doing reconstructions in phantoms, and it also works on the body. The problems with flexPCB's come when you encounter a concave location on the part of the body you are imaging. For instance the dibit that your backbone makes around your thorax. To get over this, I also made the 32 electrode cable which you see here on the lower right - I am yet to try it as it just arrived but it appears like it will be a good solution to the concavity issue. 

    PCBs aren't born perfect it turns out and it took a few attempts(and I still have one more final run planned actually). On the left you can see my initial attempt which worked for 8 electrode EIT but had a couple of small errors. It's not as user friendly as the design on the right but has bluetooth and lots of options and test points not to mention being a bit on the large side! The second smaller board was one made just to do 8 electrode EIT as well as bio-impedance spectroscopy. The third board shows my move to 32 electrode EIT.  At this stage I decided to do another run which was all about user friendliness and fitting neatly into a box with a battery which is the white PCB on the right. I made a small mistake in the FTDI chip arrangement, which means I need another run, though this PCB works in most regards(the analog sections and the bluetooth as well as the power sections are all good).  The next iteration will have the FTDI chip fix as well as a few more added tests points. 

    Finally we have the boxes - it's always nice to have an enclosure which both protects the PCB and houses the battery. Mechanical design is not my forte and here are a few attempts. I started with a transparent design(the yellowish looking thing on the left bottom) an decided transparent 3D printing is not the way to go. The large one on the left was a bit overly generous with space and it's nicer to have something snug. The one on the far right, was not done with ABS but PLA instead and you can see how rough the finish is on that. It's so rough the screw holes aren't functional. Then, there is the one at the bottom which fits snug, is relatively smooth and does the job! 

  • New thorax lung images and time series of breathing

    jean09/11/2018 at 20:25 0 comments

    With the latest PCB revision: spectra, I can wrap the electrodes around my middle to see lung expansion as well as heart rate. Below is a time series of just 4 electrodes to show breathing in and out, as well as impedance changes due to the movement of blood through the heart. 

    Once I'd get the time series data on my body, I went to wrap the 32 electrode cable around my thorax and used the GREIT algorithm to do a tomographic reconstruction of a conductivity map of my lungs. This is just an initial image, and you can clearly see I have two lungs! Further work could be done to refine the algorithm, and ensure the connection to my body is good but I am quite happy with this as a tomographic image reconstruction, using only 32 electrodes. In comparison, a CATSCAN typically uses upwards of 256 'electrodes' or angles for it's reconstruction, and also uses ionizing radiation. Below is the frequency at 25kHz, so it's just one frequency. With multi-frequency EIT even more information should be available. 

  • New 32 electrode model that's safe for use on humans

    jean08/31/2018 at 23:20 0 comments

    I revised the PCB so that it's now IEC60601-1 compliant for safe use on humans as well as with 32 electrodes for better spatial resolution. Also there is updated software with a choice of Gauss-Newton approximation, Back Projection and GREIT algorithms available at https://github.com/openeit

    See the new higher resolution image reconstruction! 

    Super small PCB with Bluetooth for wireless transmission too. Still working on refining the details but so far so good! 

    Soon, after one last PCB revision(yes the final one now *fingers crossed* ), I'll start generating more test images on humans and animals and of course - fruit. 

  • Future Plans

    jean07/15/2018 at 05:53 0 comments

    Medicine is an important field that deserves to have some innovation balanced with it's regulatory hurdles. At the start of surgery people used large saws, now moving to finer tools such as keyhole surgery. Imagine if we could develop bioelectronic techniques to the extent that we could do all surgeries precisely and non-invasively. 

    It still needs much more work to get to that future, but if more of us could improve the technology, it seems it would improve faster and we would reach a better, happier and healthier future together. 

  • What can you use it for?

    jean07/15/2018 at 05:48 0 comments

    You could use it for many things ranging from teaching yourself about biomedical imaging, to assessing the health and well being of various constituent body parts. It doesn't have as high spatial resolution as MRI, but it can have great time resolution(like EEG but EIT has better spatial and contrast information). 

    Here is a summary of potential applications if it got a little bit better(with your help). 

    Even if it is not as good as MRI for a particular purpose, perhaps it's better than nothing... making it a great option for situations where populations have none. 4 Billion people have no access at all to any form of medical imaging, and problems like Tubercolosis run rife. 

  • Reconstructing the image.

    jean07/15/2018 at 05:42 0 comments

    You might wonder how you reconstruct an image with AC current. Well it's exactly the same way as you do in a cat scan. 

    By sending current through every combination of electrodes, you measure the differences at the receive end and add up all the signals similar to the picture above. The addition of all these paths adds up to the image again. This technique is called back projection, and you can use the radon transform to do it. 

  • How does it work?

    jean07/15/2018 at 05:38 0 comments

    Different tissue types have different impedances, so when you send an AC current through it will take different paths dependent on the material that is in it's way. The picture below describes the basic re-routing that is done by current that enables an image to be reconstructed. It's interesting as this is non-ionising radiation meaning it can be done much more safely than say an Cat scan which can cause cancer over time. 

View all 7 project logs

  • 1
    Build instructions can be found at mindseyebiomedical.com
  • 2
    https://github.com/openeit

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Nixie wrote 10/07/2018 at 20:34 point

That's worth of the Grand Prize, if I may say so!
Excellent project!!

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ws786873 wrote 09/12/2018 at 06:02 point

Great project. If it can be miniaturized, it is cheap and can be bought by ordinary families. And with the cloud AI diagnosis. It allows people to discover cancer and other diseases earlier. It’s great for the public!

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jean wrote 09/12/2018 at 16:03 point

Thanks! It's very small AC current within human safety standards too. The current size is 2" square. It's in development, but it's a very open area so it seems like it can easily be improved further. Plan to make a kit available in a few months time. Large parts of the world have no access to medical imaging at all, so having something open and inexpensive seems like a way to create a platform to make this technology cheap and ubiquitous. 

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jean wrote 08/31/2018 at 23:11 point

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