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rjo_
05-17-2010, 10:50 PM
My son's special olympics coach has now had 4 brain surgeries to correct the equivalent of a simple plumbing problem.· She has two shunts, which don't work and I am now trying to figure out how to look in her ear to figure out what the pressure in her brain is doing... obviously this is not a· joke.

The shunts, which don't work very well... don't work because they are stupid shunts.· A genius trid to guess the fluids of the brain and got it wrong.· Actually...many geniuses have tried to figure this out... and they all got it wrong.·

Obviously... we need the smallest implantable Propeller possible.· If you build it... they will come.

Rich

rjo_
05-17-2010, 10:52 PM
Don't worry... we aren't going to put it into the brain.

TonyWaite
05-17-2010, 11:39 PM
Hi,

Could we have a little more info. about exactly what needs to be measured and the possible sensing points?

If the task is to reasonably crudely assess intercranial pressure or similar, could an air-puff tonometer be a starting point?

Regards,

T o n y

rjo_
05-18-2010, 01:12 AM
Tony... as usual I convolved two thoughts into a single misleading thread. There is an acoustic reflex, which changes with the intracranial pressure. This I can handle. An air puff tonometer is increadibly close to what is needed... and I have some in my basement that aren't being used. Typically a controlled 1KHz sound is used and the displacement angle of the tympanic membrane is measured... a perfect job for the TSL1401. But at the end of the day... the measurments that I can get will only be a "reflection" of the ICP. These measurements are repeatable for a given patient over reasonably long periods of time... but are not apparently comparable between patients.

What is actually needed is to directly monitor the ICP. This lady already has two shunts... but the only thing they do is open when they sense a certain pressure. They are continually obstructed by bits of tissue finding their way into the tips placed in the brains (when the ventricles collapse, which they tend to do repeatedly and in unexpected ways.)

None of the available shunts really compensate adequately for human activity... such as getting out of bed and moving around. They don't tell us how much fluid is passing through or what the pressure is... they are hydraulic machines, with the best reasoning behind them... which doesn't work.

But forget this application... what is needed is an implantable controller... not just for this but for lots of things.
Such controllers will obviously be produced ... if we wait long enough and don't mind people suffering in front of our eyes.

I can't do this sort of design... but we have lots of younguns and old pros who can. I just wanted everyone to remember that there is a huge need... and they could be the one to fill that need. It all sounds like rocket science... but all that really is needed ... is finding a way to make an externally controlled and energized Prop with the smallest dimensions possible... Hanno is already designing a system to remotely program a Prop... we aren't going to be implanting an XBEE into anyone soon, but the actual programming problem is solved. Until something like this happens, I'm going to be looking in an ear, trying to figure out what the brain is doing:) and then communicating with people, who really don't want to talk to me. There are important clues in the eye as well... we are doing OCT(ocular coherence tomography) to watch the changes at the interface between the ICP and the ocular pressure... but this is so dampened by everything in between that we see only gradual changes... we can sort of figure out what happened yesterday, but have no idea what is going on today:)

The real challenge that I was trying to make here is for someone to come up with the smallest, completely functioning Prop, which can be externally energized and programmed ... given that, the rest could be someone else's problem. There are guys devoting all of there time to this sort of thing... but you have to give them something to work with.

Rich

Bean
05-18-2010, 02:15 AM
Rich,
Not to promote other products, but I just saw that Atmel has a ATTiny10 with a footprint of only 2mmx2mm (4mm^2).
That has 1/2 the footprint of SOT23 part (which is about 8mm^2).
Very impressive.

Bean

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Use BASIC on the Propeller with the speed of assembly language.
PropBASIC thread http://forums.parallax.com/showthread.php?p=867134

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rjo_
05-18-2010, 05:53 AM
Thanks Bean... nice to know you are around today and have time to respond.

The issue of size is only important so far as it applies to the best microcontroller for the job.

If one were going to put this in a sensitive location, absolute size would be important. But this sort of device would probably be placed in a pocket under the scalp. If the smallest I could get was a protoboard... I would just make the pocket bigger and put it somewhere else.

I have talked to Kathy and she has given me permission to post some more info... which I will tonight.

Thanks

Rich

rjo_
05-18-2010, 10:20 AM
Bean

I have thought about it again... and I think the details aren't really necessary. There is one thing that I would make clear... I am not going to be doing any of the surgery. I write the way I speak and that can be confusing. What I meant to say... is that a surgeon wouldn't be concerned with size so much as the functionality. The process is the same... you would make a pocket for the implant. Where you make that pocket isn't terribly important. The smaller the better. I think it belongs under the scalp close to the other hardware.

I will be driving Kathy to Baltimore to see one of the leading authorities in the field and will discuss it with her(the doctor) in the near future.

You might ask... isn't this the sort of thing that is normally done by big companies? Surprisingly not. It is almost always done by doctors and a few good people helping them. If it works, they then either start a company or more often turn it over to a large company.

Isn't the FDA a problem? Surprisingly not. If everyone does their jobs right, an ethics panel would be convened at the hospital to make sure that what is proposed is ethical. A review committee would then examine whether it is feasible, practical and in the best interests of the patient. And an exclusion would be requested from the FDA and is almost always granted. All of this could take anywhere from a few days to a few weeks... or never.

Kathy's problems are very common.

Rich

rjo_
05-18-2010, 10:23 AM
I am not interested in making one penny from Kathy's suffering. I would greatly prefer it if everything is in the public domain... so that if it works, the greatest number of people will have the earliest, least expensive access.

KenBash
05-18-2010, 10:24 AM
Hi Rich,

I was just on the phone talking to my girlfriend who's daughter is in special Olympics. I have an idea of how much the people that are part of it give and they deserve a lot given back.

I have no idea if what I do could be of any help in your project, but I'll mention it and if you think it might be helpful somewhere I'll do my best.

I'm part of a company called BioEmbedded Research we make silicone tubes and shapes for medical testing. Most of this stuff is for testing stents and deployment procedures, but I work with silicone a lot and have done odd-ball things like coating circuitry and connections to seal them from harsh environments. I want to make it clear that the stuff I make isn't intended for implant, but the Silicone I work with IS transparent medical grade.

I understand Implant grade is the same stuff with a bit more paperwork attached to it.

I have embedded wires, small metal shapes, Kevlar, Dacron and the random housefly into this stuff. If it can take 300 deg. F. for an hour or so... (no, the fly didn't do so well.) it can be embedded in a bio-compatible silicone capsule. I'm sure there are other suitable materials, but this stuff is flexible if that's an issue.

If you come up with something that needs a bio-compatible coating or even some odd-ball shapes or tubing, let me know, I'd be happy to help out. I've been considering putting a pressure sensor silicon chip INTO the silicone with small wires for power and signals as well for a cardiac "Device" I am designing, but if you have an application for an implantable pressure sensor, let's talk.

I 'm working with a couple of groups that are part of the Jordan Valley Innovation Center in Springfield Missouri. They have chip bonding equipment, and quite a bit of stuff in place to build nano technology. ( some of my friends have really interesting toys )

I don't know if the Propeller can be acquired in silicon only form, but I can see how it could be turned into an implantable computer pretty easily given the small number of components necessary to make it work.

I won't go into details, but I recently built a prototype micro-pump. ( my valve size was about .3mm ) I can see some cross-over potentials for use as an active (Pumping) shunt if someone was inclined to look into it for development.

I was also talking with a surgeon last year about problems he has encountered with shunts collapsing and discussed some possibilities for making a shunt that would still be flexible but very resistant to collapse . We both got involved in other projects and it never went anywhere, but the idea is still valid.

If you are looking into this then you must have some idea of the difficulty and the expense of developing an implant, but some great people are worth all the effort in the world.

Let me know if I might be able to help you.

Ken Bash

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" Anything worth doing... is worth overdoing. "

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rjo_
05-18-2010, 11:12 AM
Are you kidding? Could be helpful? Might be helpful? More like manna from heaven. Thank you SOOOOOOOOOOO much.

I'm looking to fix what she has... by building an intelligent system to drive it. The thing is already programmable.

After that I could care less:)

In her case, I am fairly well convinced that the shunt isn't collapsing.


Rich

Dr_Acula
05-18-2010, 01:46 PM
When I worked on the neurosurgery ward transducers were implanted all the time. However, those patients were generally post-op and in intensive care or high dependency and it was a temporary arrangement.

So you are looking for a permanent implant? This is not dissimilar a problem to programmable pacemakers which sit under the skin and have a long life battery, and are made from materials that the body does not reject. The main difference is the sensor which is pressure instead of electrical.

It looks like others recognise the need www.mems-issys.com/implantable_intracranial.shtml (http://www.mems-issys.com/implantable_intracranial.shtml)

Presumably you have a neurosurgeon already?

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KenBash
05-19-2010, 01:26 AM
Rich,

The Issys sensor looks like a giant leap in the right direction!

Great spot Dr_Acula!

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" Anything worth doing... is worth overdoing. "

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Cluso99
05-19-2010, 05:18 PM
Rich: Does the prop require a xtal and eeprom or are you planning to remotely load the code and keep that running? How will you power it? How many I/O do you need and what about analog?

I have to ask, why do you want to use the Prop? Is is because it is actually easy to program and multiple cpus allow a lot of error checking?

I hate to say it, but maybe there are other better suited chips. I guess we need to know a lot more information about what configuration you require.

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heater
05-19-2010, 06:01 PM
I'm wondering what the power supply might be? The Prop is a bit thirsty compared to many other options now a days.
How are you going to get the pressure data out?

Aside: An old girl friend of mine was diabetic. She ended up in hospital one time in very bad condition. There they discovered that her new pen sized blood sugar meter was way off calibration. I would worry like hell about the reliability of any medical device I made. Avionics software I could live with, being surrounded by a whole team dedicated to making sure everything worked.

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rjo_
05-19-2010, 10:56 PM
Ken

Thanks again for responding... I need to clarify a statement. There is no doubt that the shunt may be collapsing... but the fault is not in the shunt. The shunt is made to collapse under tissue pressure... this is so that the dire consequences of tissue erosion are made less dire. Prior to her last two surgeries, we did positional testing on her (still existing) shunt and found that the collapse/obstruction was positional in nature. Supine, the shunt opened and filled the reservoir.

I am still hopeful that this is simply a clinical management issue... but getting to that point seems like pulling teeth:)

My deep suspicion is that in Kathy's case... there is a narrow window of conditions, which allow adequate drainage and headache relief. Outside of this window, you have unacceptable headache levels, with tissue collapse around the shunt on the low pressure side.

Heater

That is an engineering problem:) So, I'm not worried about it.:)


et al.

The other huge advantage of putting this into the public domain is that we get something better than peer review of the design... we get the review and criticism of the best minds in the world. That is something you cannot buy.

Rich

KenBash
05-21-2010, 10:42 AM
Rich,

Working with silicone shapes every day, I wonder if there might be some mechanical solution to the problem.

perhaps a shunt with a series of micro-holes that allow fluid to pass even if most of the opening is closed with tissue.

It might be difficult to "mold" these small openings in the shunt, but a friend owns a company (US Photonics ) that uses a femtosecond laser to cut micro and nano-scopic shapes into just about anything.

If the shunt could filter tissue but allow the passage of fluid, would this be a possible solution?

I can make tubing down to half a milimeter or so. If there was a balloon "Filter" on the end. Might this allow drainage regardless of tissue at the end of the tubing?


K.B.

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" Anything worth doing... is worth overdoing. "

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rjo_
05-22-2010, 01:11 AM
Ken,

Shunts have been around for a while. I wouldn't profess to know enough about them to design one. On the other hand, since they have been around for a while, the problems that pop up are fairly well researched and discussed. Since Kathy has two ... it seems that with the right additional external hardware, it should be possible to modify one... without really touching it much and actually turn it into a pressure sensor... but that is more a suspicion than a plan.

What does seem absolutely true... is that shunts in general do not do a very good job at correcting for positional changes... and to adjust this particular shunt, we are dependent upon going to a very busy surgeon... so it gets adjusted rarely. If it were my shunt... I would want gyros and accelerometers talking to it... adjust it to my motions:) Now that we are close to wireless solutions across the board... that seems like a real potential. And the added hardware can all be external.

For a brief time... before Kathy ran into her problems, I was interested in an ocular condition call "hypotony," in which the eye loses all pressure and basically goes away. A shunt from the CSF into the eye makes perfect sense to me. For a while, I had such a patient and was beginning to think seriously about it.

Kathy had a visit with her neurologist this morning... and he was not at happy:) When he gets done doing what he wants to do ... he wants to ship her off to Baltimore, which I have been trying to get her to do for the last two weeks:) I am hopeful that with some TLC and careful management of the shunt, maybe we won't have to do anything.
et. al.

I think the subject of an implantable Propeller is valid and should have been raised in this forum anyway. And if anyone has been thinking about it... keep thinking about it at least·until we are out of the woods.

I would encourage anyone... who is capable (or even almost capable) of such designs... put you doodling in the forum.· You will get great feedback... and if people like Ken see it and are impressed... they will send you in the right direction:)

Rich

Post Edited (rjo_) : 5/21/2010 5:28:43 PM GMT