Tracking Cancer Treatment With An ESP8266-Based Radiation Sensor

Those of us who have not been in that position can only imagine the anguish of learning that your teenager has cancer. This happened to [Rob], whose child was diagnosed with papillary thyroid cancer. It’s a condition that can be treated with surgery followed by a course of radioactive iodine to kill any remaining cancer cells. During iodine treatment, the patient is radioactive enough that other people must maintain a distance of 3m from them, and as a learning exercise for both father and teen he created and refined the design of a portable wireless radioactivity monitor.

There are a variety of sensors for radiation monitoring including the well-known Geiger–Müller tube, but he settled on a PIN photodiode based sensor supplied by This sensor is not at its most sensitive at the energy levels emitted by the iodine isotope used in the treatment, but the relatively high intensity of the radiation meant that enough would register for a useful reading to be taken. The sensor board he was mated to an ESP8266 module. [Rob] went through three iterations of the balance of the hardware before settling on a lithium-ion battery and a plastic case.

On the software side, the ESP connects to an MQTT server, from which a CSV file of data is derived. On a computer, the CSV data is collected and plotted to a graph. The data take during treatment clearly shows the reduction in radiation following the isotope’s half-life. The graph isn’t perfect though, there is a gap due to the second prototype’s batteries running flat

From his epilogue it appears that his son has recovered, and we wish them further good health. The details have been published in the hope that other young people facing the same trial might benefit from building their own radiation monitor.

22 thoughts on “Tracking Cancer Treatment With An ESP8266-Based Radiation Sensor

  1. As someone who had their thyroid taken out last year for the exact same type of cancer (and will soon be undergoing radioiodine therapy), this is a super cool project! Definitely glad to hear Rob’s kid made a full recovery.

  2. In case you want to try this yourself, you can get a better version of that detector.

    The one used in the radiation-watch sensor is a bare PiN diode: it’s nice and sensitive to lower energy x-rays, but is pretty transparent and insensitive to x- and gamma rays higher than 20 keV or so, and darned near blind to the 364 keV gammas coming from the radioiodine, as the author notes.

    The diode detector itself is from First Sensor
    Along with the plain diode that Radiation Watch uses, they also offer versions with scintillators, which have MUCH better sensitivity to the higher-energy gammas:

    If really want to roll your own, you can get pretty good sensitivity with just a plain large-area diode like a BPW34, with a piece of scintillator like Lanex Fast stuck on top. Huge sheets of scintillator can be had really cheaply from surplus places – they are (or were) used in x-ray screen-film cassettes, and were routinely cycled through. You can get about 10% of the sensitivity of the First Sensor diode this way, for about 0.5% of the cost…

    A good high-quality monocrystaline large-area solar cell with a scintillator sheet also works really well as a sensitive general survey sensor, but it’s tough to detect single-photon gamma hits because the diode capacitance is so high: it behaves more like an ion chamber in response time.

    1. From searching the Web it looks like a Sodium Iodide crystal is most commonly used for detecting radiation from I131. I see a few offered at a wide price range on ebay. Would using one of these with a PMT or other photosensor work?

      1. Štěpán is right: you need to match the scintillator with the detector.
        Thalium-doped sodium iodide (NaI:Tl) is pretty common, cheap, and an efficient scintillator, but emits its fluorescence in the deep blue: well suited for most photomultipliers, but not the best for silicon diode detectors, which are nearly blind at that wavelength.

        Cesium Iodide (again, thalium-doped, CsI:Tl) emits in the green and is much better suited for coupling to silicon diodes. That’s what First Sensor uses. Unfortunately, CsI is hygroscopic and deliquescent: unless hermetically sealed, it will slowly absorb water from air and dissolve itself, so not well suited to DIY approaches. I suspect Radiation Watch chose the no-scintillator version if the First Sensor detector in part because of this (also it’s a thicker detector stackup and more costly)

        That’s why I recommended Lanex phosphor screens: They’re gadolinium oxysulfide, very efficient and emit in the green, and aren’t affected by humidity. The “Fast” variety is extra thick and better suited for detecting higher energies like that from 131-I (anything over 25-50 keV, actually). You want to avoid the more common scintillator (phosphor) screens that emit in the deep blue, like Cronex and pretty much every autoradiography screen: they are essentially useless for coupling to silicon diodes.

  3. My aunt had radioiodine therapy too. My uncle and the rest of the not-science-literate family were duly warned to stay away from her for a few days, but none of them had a geiger counter. So I pulled mine out and gave them a pretty dramatic demo of how hot she was and how fast the dose rate dropped off to near background even just in the same room.

    Air can be better radiation protection than lead: lead blocks radiation proportional to its thickness, but air is unusual: protection is more than proportional to its thickness *squared*. (yeah, a physics joke, but not wrong — think about it.)

    1. Beg pardon Paul about your unusual claim about air ???
      I studied nucleonics in great detail decades ago in relation to several radiation sources and absorption issue measuring flow of iron ore. Air has negligible value other than alpha but, that is nothing special about air per se, it’s very low density makes it useless overall for all nuclear radiation though with CO2 and water vapour its effective at increasing infra red resistivity. There are all sorts of stupid rubbish claims bordering on dangerous scientific misconduct and your use of language mirroring that seems to indicate you’ve been seriously misled not having base physics under your belt :-(
      Unfortunately I’ve read more claims of that type foisted on you, they are mostly from click bait web sites seeking traffic which sadly you repeated without checking or basic references.

      Please link to the source of your claim Paul ?

        1. Really Paul, didn’t come across as a joke, unclear vocabulary, no emoticons hence can be so easily mislead the unwary and uneducated.
          Now you claim PhD really – what the heck has that got to do with your ‘joke’ ?
          Since you raise issue of credentials, what PhD topic, year, institute ?
          Link to your PhD would be far more useful than Wikipedia, which is tangential, facile and barely relevant in respect of nucleonics nonlinearities, surely someone with a PhD in medical Physics would know that ;-)
          So PhD link please ?

          1. Mike, you’re right, my degree has nothing to do with my post – I mentioned it only in response to your assertion of me “not having base physics under your belt “. It is otherwise not relevant, whereas the inverse square law in that Wikipedia link is the key to understanding the physics lesson masquerading as a weak joke.

            But thanks for reinforcing that I shouldn’t quit my physicist day job to become a comedian.

            To make it perfectly clear: A large thickness of air is a good way to reduce direct radiation exposure, not because air is a good absorber, but because putting a lot of air between you and the source means putting a lot of distance between you and the source, and the dose rate goes down as the square of the thickness of air, thanks to the inverse square law.

            Yeah, it’s even less funny when you have to explain it.

    2. My significant other needed this type of therapy after thyroid surgery. I had built a few “dumb” (clicking only) Geiger counters years earlier around some highly regarded tubes (American and East German surplus). I thought that I’d try them out. The results were shocking. I could detect an uptick up while driving behind my house! Later, they came in handy when I “discovered” that radiation works in three dimensions. I had to stay 15 feet away from her for a week, and I found that the table that I like to sit at was almost exactly under our second-story bed where she would watch TV. So, I stopped sitting there for a while…the toys that I built came in handy.

      Within a month and a half, I could not detect any radiation above background in our house.

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