SPECTRA AND OPENEIT: AN OPEN-SOURCE ELECTRICAL IMPEDANCE TOMOGRAPHY IMAGER
A thirty-two electrode board that images lungs in real time using tiny currents instead of X-rays, and every file is published.
by Jean Rintoul
ScienceOpen-hardware
- difficulty
- ●●●●●
- time
- weeks
- license
- CC-BY-NC-SA-4.0
- repo
- repo INACTIVE97 stars
●●●●● · weeks · CC-BY-NC-SA-4.0 · 97 stars · repo INACTIVE
WHAT YOU’LL NEED
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COMPAREE VERDICT
Electrical impedance tomography works by driving small alternating currents through electrodes on the skin and reconstructing a cross-section from how tissue resists them. Jean Rintoul designed Spectra as an open counterpart to hospital systems. The board, firmware and reconstruction dashboard are all published under a non-commercial licence, and the OpenEIT docs site has installation steps and tutorials. What is thin is the path from files to a working board: the 32-electrode Spectra design is published as a schematic and layout PDF, and the three repositories assume fluency in mixed-signal board bring-up, Python signal processing libraries, and impedance tomography theory. If you already work in biomedical instrumentation or have built EEG or ECG systems from scratch, this is the starting point you want. If you have not, you will spend weeks learning what the ADuCM350 does, why the electrode interface matters, and what back projection even reconstructs. The biggest trap is assuming this will behave like a consumer kit — it will not. This is a research build for people who troubleshoot analog front-ends and write their own calibration routines. If that is you, it is a remarkable foundation.
IN THE REPO
GOOD TO KNOW
- —PCB design is in the EIT_EE repository as Spectra.pdf, a schematic and layout.
- —Firmware is in a separate repository called EIT_Firmware.
- —OpenEIT Python dashboard is in its own repository for reconstruction.
- —No assembly guide for the 32-electrode board; the parts list in the repo covers the earlier 8-electrode design. Software installation and usage tutorials are on the OpenEIT docs site.
- —Licence is CC BY-NC-SA 4.0: you may build for yourself but not sell boards or services.
- —This is research hardware, not a medical device, and not approved for clinical use.
Parts to buy
2 itemsFrom our check of the build. Exact quantities and part numbers are in the creator’s BOM.
- Custom PCB fabricationfrom the repo files
- Electrodes and cablesFind
Can I build this?
Build at your own risk. Projects involve tools, electronics and sometimes mains voltage — follow the creator’s safety notes.
Videos
Spectra EIT live imaging demos (Jean Rintoul)
No official build video. This short clip is Jean Rintoul's own demo of EIT recognising wrist muscle movements, not a tutorial.
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Start here
Navigation into the creator’s own docs — we don’t rewrite the guide, we route you to the source.
- 1.Read the three repositories (Hardware schematics in EIT_EE, firmware in EIT_Firmware, dashboard in OpenEIT. All are separate.)
- 2.Understand the impedance measurement chain(The ADuCM350 impedance-measurement SoC and the ADG732 electrode multiplexers are the core of the design. If you have not worked with impedance analyzers before, start there.)
- 3.Find a PCB fabricator who will work from the PDF schematic(Gerbers in the repository are for the older 8-electrode board; for the 32-electrode Spectra there is only the PDF schematic and layout.)
- 4.Source components without a BOM(The Spectra schematic shows part numbers; partsdb.txt adds Digi-Key numbers for the earlier board. Quantities and substitutions for the 32-electrode version are up to you.)
Resources
Documentation, files and community threads for this build — we link straight to the original sources and never rehost the creator’s files.
KNOWN ISSUES
- The parts list with Digi-Key numbers (partsdb.txt) and the Eagle BOM cover the earlier 8-electrode board; for the 32-electrode Spectra you will build your own BOM from the part numbers in the schematic PDF.
- The 32-electrode Spectra board is published as a PDF schematic and layout only; Gerbers and Eagle source files exist just for the older 8-electrode board, so modifying Spectra means redrawing it.
- The three repositories do not link to each other or explain how they connect. You will map firmware to hardware to dashboard yourself.
- Electrode placement, skin preparation and calibration are only covered briefly in the OpenEIT tutorials. Hospital systems include detailed protocols; this does not.
- The licence is CC BY-NC-SA 4.0, which prohibits commercial use. You cannot sell boards, offer paid scanning services or build it into a commercial product without the author's permission; if your use sits in a grey zone, such as company-funded research, ask first.
- Reconstruction algorithms are implemented but not explained. If you do not already know what Gauss-Newton or the Graz consensus method are, the code will not teach you.
Is this a medical device?
No. It is research hardware and is not approved for clinical use, diagnosis, or any medical decision-making. Build it to learn how EIT works, not to replace a hospital scanner.
Can I sell boards or offer services built on this?
No. The licence is CC BY-NC-SA 4.0, which prohibits commercial use. You may build for yourself, for education, or for non-commercial research.
What does it actually cost to build?
PCB fabrication and components dominate the cost, depending on your supplier and whether you already have test equipment. The assembled Spectra kit is currently sold out.
Do I need electrodes beyond what is on the board?
Yes. The board has 32 electrode connections but does not include the electrodes or cables. The OpenEIT tutorials recommend gold-plated electrodes with gel and explain basic drive and sense placement, but there is no clinical-style placement protocol.
How do I know if I am qualified to build this?
If you have brought up a custom mixed-signal biomedical board before, debugged an impedance measurement front-end, or implemented reconstruction algorithms from papers, you are ready. If you have not, this is not a first project.
Community builds
No community builds yet — be the first, we feature the best ones.
Discussion1
FROM THE COMPAREE TEAM
Spectra drives thirty-two electrodes from a board two inches square, with hardware, firmware and reconstruction code in three separate repositories. If you have built one, what was the hardest part to source or figure out?
Jean Rintoul
Jean Rintoul created Spectra and OpenEIT at Mindseye Biomedical, a San Francisco company building non-invasive biomedical imaging tools. She designed Spectra to make electrical impedance tomography accessible outside hospital budgets, publishing the hardware and software under a non-commercial licence so researchers and makers can build their own systems.
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DISCLAIMER
- Comparee is not the author of the projects featured here. All rights to each project belong to its creator — every page links to the original source, and we never host creators’ files.
- Information is provided without warranty and may become outdated as projects evolve. Prices are indicative bands only — always check the creator’s parts list for current costs.
- Building and operating any project is at your own responsibility. Protective equipment, safe workshop practice and compliance with local regulations are the builder’s responsibility.
CompareeTEAM1mo agoedited
Practical notes from our verification: the 32-electrode Spectra board is published only as a schematic PDF, without Gerbers; the PDF does carry reference designators and part numbers around the Analog Devices ADuCM350 impedance chip and ADG732 multiplexers. The same hardware repository also has Eagle sources, Gerbers and a parts list with Digi-Key numbers, but those are for the older 8-electrode board. The firmware repository is written for Spectra and needs IAR Embedded Workbench, with a separate gcc branch; the Python dashboard and reconstruction code are in a third repository, and a documentation site has installation steps and three tutorials, including electrode attachment. The linked video is Jean Rintoul's gesture-recognition demo, not a build tutorial. The hardware and firmware repositories have not changed since 2021, while the dashboard received updates in 2025. If you have turned a schematic into a working board before, this is a strong foundation; if not, budget real time for parts sourcing and layout. Correction (4 October 2026): we re-checked this page line by line against the project's own repository, documentation and videos, and fixed errors in earlier versions.