Electromagnetic Tracking System Sensor - Page 1
Forum section: electronics / projects

author: alexjaeger
author_rank: Newbie
timestamp: February 01, 2016, 12:04:29 pm
content: Hi all,This my first post, so lets going!I'm working on an electromagnetic position tracking system that uses a proprietary sensor developed by Northern Digital (http://www.ndigital.com/medical/products/tools-and-sensors/). Its the really tiny 5-DOF version I'm using. It measures 0.5mm x 8mm with an inductance of 2.4mH. I've estimated approximately 350-400 turns on the core is (assuming ferrite based)Currently I have to purchase sensors from that company, but they are expensive and I have doubts whether they wind the coils themselves.Does anyone here know of coil winding companies capable of winding something this small?Cheers!

author: CaveMannDave
author_rank: Regular Contributor
timestamp: February 01, 2016, 02:05:25 pm
content: Hi:Those folks DO push the envelope for tracking small things in human-bodies, don't they!We used to use 1, 2, or 3 X-ray beams w/image converters (fluoroscopy) and injected contrast media to get close to that.First question; is this to be used AT ALL in living humans? The FDA and other agencies in the world may object.Next; is the application in ~water-density (like living tissue) media, and (say) a 1 meter cube? I don’t know all their technology, but it probably has to be within range of several transducers or antennae emitting marker "pings" that rely on known propagation behaviour, just as GPS systems do.Finally; their propaganda mentions Micron, I'm guessing .1 millimetre-order accuracy and precision normally. If you REALLY require that, don't care about life-safety (sterility, etc.), are dealing with well-characterized and predictable targets, MUST have sub-millimeter diameter X 1+ meter reach, and yet can't invest in (what, $500.00US?) for re-usable, non-sterile probes, then what kind of trickiness are you doing?What is the cost of the Reference transmitters and positioning devices -- they LOOK pricey.Sheesh!Cheers,Dave

author: alexjaeger
author_rank: Newbie
timestamp: February 01, 2016, 03:29:56 pm
content: Hi Dave,Its incredible really the amount of sensitivity they can pack into these beauties!Yup, this work is for human use (eventually...). The sensors from NDI are FDA approved so there's no worry there. If we were to find another sensor vendor/develop our own then approval would be easier as a similar device exists.The application is bronchoscopy. The sensor is embedded into the bronchoscope and is used to wirelessly track the tip position within lungs of a patient. The system uses low frequency time-varying EM fields to generate a working volume around the patient's chest.We've developed our own homebrew EM tracking system (http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6731548) and would like to stop relying on 3rd party hardware is allThe overall cost of the system is pretty low at ~3000eurocheers!

author: CaveMannDave
author_rank: Regular Contributor
timestamp: February 01, 2016, 07:00:37 pm
content: Quote from: alexjaeger on February 01, 2016, 03:29:56 pmI thought so. And, as far as I know, having something 'Similar' to another approved product does not exempt your company from the Obstacle-course (and costs) of getting type-approval.I figure you’d need a recognised, accredited, medical device manufacturer that could ALSO manufacture the required windings (finer than silk?) in a certified plant, and encapsulate them in the end of guide-wire skinny (what French #?), super flexible, and almost infallible leads, with cleanliness and sterility nearly perfect, and turn these out for any significant amount LESS than the "other guys" who must have already run that gauntlet?Try to set up a relationship w/NDI for volume pricing: let them carry the liability.Medical devices are outta-sight in cost, but there are reasons: Universities turn out Law students by the carload, these folks spend their CAREERS finding someone to blame for any and every misfortune they can find on Someone, hopefully with DEEP pockets, and then put out a mass media campaign "Did you or a Loved One die or suffer from [device or procedure XYZ], then call now to 1-800-bla-ther, and Our Team will get you the Justice you DESERVE", and then they purchase that 3-story house on 5 acres with a pool in the Suburbs, to keep their Trophy (High Maintenance) Wife.Funny how that works...I don't relish being a wet-blanket to your desire to make medical diagnostics/treatment affordable, but, I don't think, that you would enjoy being a defence witness for apreviousemployer, trying to justify your choice to low-ball the cost of part of your device, just to save expenses -- while facing an entire "Class" of bereaved Plaintiffs.Quote from: alexjaeger on February 01, 2016, 03:29:56 pmIt really sounds like a wonderful way to guide a 'scope, though how far can one go before the bronchioles are too narrow to enter? I'd guess that one could at least select a lobe, and perhaps a Region of a lobe.Consider, however, that this procedure would only be administered on a patient already needing invasive diagnostics: All valiant efforts fail, and the CA metastasises to the rest of the body. And along comes a sharp Attorney with a hard-on for for 'devices'; after MUCH digging, he finds a short memo about getting the Wun Hung Lo company in XingXang, PRC to save the company 800.00 Euros per procedure, which makes it more available to more people, possibly saving lives; the signature is yours.He asks: "Why, when you had a perfectly good, and well qualified supplier, did you choose to have one of the most critical parts of your system "offshored", when the Patent holder had spent Millions to perfect and Certify his Own design?""Uh, we could save $NNN per procedure""And this increased your sales and market valuation?""Uh, I guess..."......And on it rolls...I HOPE you get my REAL point: Is making the sensor yourself REALLY worth the Risk? Costs are Always passed on: Tax companies, prices go up/wages go down. Set Minimum wage laws, prices go up. Price of some material goes up, something has to give, somewhere...ECON101There Ain't No Such Thing As A Free Lunch. (TANSTAAFL) {Robert A. Heinlein}Quote from: alexjaeger on February 01, 2016, 03:29:56 pmI'd LOVE to read that, but it's behind a PayWall:Does this forum allow Private Messaging? If so, please shoot me a copy.Believe me, I have ALWAYS looked for the lowest-cost solution for WHEREVER I was working, from shoestring-startups to multi-billion$ giants (T.I.), and the HARDEST lesson to learn was that sometimes Perfect is the Enemy of Good Enough. That REALLY rankles me to my CORE, butrealityeventually will get your attention, if you survive it.My best wishes to you in your career!Cheers,DaveEDIT: screwed-up acronym spelling in Heinlein quote {FACEPALM}

author: HAL-42b
author_rank: Frequent Contributor
timestamp: February 01, 2016, 08:02:34 pm
content: Look into microphone capsule manufacturers maybe? They are equipped to deal with thin wire.

author: alexjaeger
author_rank: Newbie
timestamp: February 02, 2016, 09:18:51 am
content: QuoteWhen you phrase it like that it really does seem a bit extreme to develop our own. Setting up a volume licensing agreement with NDI could be tricky though, as its an obvious conflict of interest since we have our own tracking system! It depends though on how we choose to market everything (if it ever comes to that stage). Most likely it might make sense to market our tracking system as a low-cost experimental toolkit for research use and keep it entirely separate from instruments containing a tracking sensor.I try not to worry about the legal/approval side of things too much though, I leave all that to my supervisorIn all fairness though, I do try and keep these issues in mind all the same, but I'd always rather focus on the tech and let someone else deal with approval once development reaches a certain stage.QuoteWe're also making a catheter to investigate though the narrow bronchioles. The catheter contains a sensor too!QuoteYeah, I still have a lot to learn in that regard. When the OCD kicks I can't be swayed!Cheers for the chat (I'll PM you that article soon)!

author: alexjaeger
author_rank: Newbie
timestamp: February 02, 2016, 09:21:20 am
content: Quote from: HAL-42b on February 01, 2016, 08:02:34 pmThat's a good call, I had never thought of thatI'll check out some companies and post any interesting ones up here.cheers!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: February 02, 2016, 09:40:54 am
content: Quote from: alexjaeger on February 02, 2016, 09:21:20 am..and the people who make the coils for mechanical watch movements

author: CaveMannDave
author_rank: Regular Contributor
timestamp: February 03, 2016, 01:44:17 am
content: Quote from: alexjaeger on February 02, 2016, 09:18:51 amYou never know 'til you ask.I'm aware that many outfits sell their product at reasonable below-wholesale rates, when a legitimate contract for hassle-free product sales is on the table. Bidness is bidness. Consider Sears & Roebuck in the US -- they sold, over the Years, Household appliances from almost every manufacturer, happily re-branded, at competitive prices, and did ALL the stocking, delivery, warranty, and (LOCAL) service nationwide. Did Whirpool or Amana complain? Maybe -- on their way to the bank!Your outfit MIGHT even offer, as sweetener, some cross-licensing arrangement for your Less-Costly, but pre-engineered tools for specific uses, and increase YOUR sales by offering their High End components to your customers. (Comedienne Judy Tenudo had a famous tag-line "It Could Happen...")quote author=alexjaeger link=topic=62265.msg857431#msg857431 date=1454404731]I try not to worry about the legal/approval side of things too much though, I leave all that to my supervisorIn all fairness though, I do try and keep these issues in mind all the same, but I'd always rather focus on the tech and let someone else deal with approval once development reaches a certain stage.That was my attitude for most of my career, until recently. I kept my head down with Aspergers-induced devotion, going home only when they kicked me out, thoroughly convinced that MY project was the only one that mattered, walking up to the CEO (politely, but as Equals) to get approval on a purchase order for something "I KNEW" would fix something, whether in my Bailiwick or not. I never lusted for anyone else's position, but I would not be ignored (/RANT)I let OTHERS sweat the 'small' stuff.Now, I know that Engineering has more than just what is on the bench in front of you to think about. I don’t mean "Really Big Issues", unless you like that crap. I'm just suggesting that the Economic Future of our employers, and the well-being of our customers should,somewhere, enter our minds as we make our decisions.I think Hippocrates is credited with the Oath, that Physicians are (supposed) to follow "First of All, DO NO HARM". I believe I can follow that.Quote from: alexjaeger on February 02, 2016, 09:18:51 amI like it already! Tell me more. How small are you shooting for, and is this for super-selective radiotherapy/drug-delivery-treatments, or targeted biopsy/visual imaging type procedures. Perhaps spot-placement of contrast media for other imaging methods? (CAT, PET, MRI, EBT)Quote from: alexjaeger on February 02, 2016, 09:18:51 amHeh heh, OCD, Aspergers, ADHD, (maybe even PMS) in my case, but Engineering isdrivenby folk that neverquitefit in: Half-a-Bubble off Plumb, stare at the ceiling a lot, and die alone. But, at least in my case, I've had a good, mostly fun run, and enjoyed being able to point and say "I made that", if anyone is listening.Quote from: alexjaeger on February 02, 2016, 09:18:51 amThat would be appreciated.Cheers,Dave