Medical Devices development (Biotelemetry)

On this page, a Biotelemetry project described.

In a lot of research medical project is a lot of tasks connected with testing of new medicine. In traditional way, small animals (rats, etc.) have the medicine injected and then researchers try to capture important biologic parameters, like electrocardiogram (ECG) and electroencephalogram (EEG), from animals under test. The problem is, that it's impossible to fix ECG sensors reliable over animal's skin - in best case, animal will try to remove it, which distorts data from sensors in unpredictable way. In connection with the fact that skin's electric potentials are very small (1-3 mV), we also have a problem with signal distortions, because there are many noises from equipment: DC-DC converters in any science laboratory. There are also other problems, but I'm not a medic, to explain it clearly (and clearly understand before).

One decision it to fix animal under test on table and insert sensors under its skin, but it means that we have very unreliable physiological conditions, because the animal near a death.

The decision is a surgery operation, which put implant with sensors under animal's skin. This way, we remove all problem simultaneously. We have skin as an electric shield from noises (very good shield), and we have animal with good health, inside its pride.

Of course, we weren't the first who invent the decision. Medtronic company has some products it his product line, however, very high cost of their implants makes their use impossible for 9/10 researchers (in Russia, it least). We did our device very cheaper with less size.

That's photo from one of the final stages. The picture shows 2 rats with implants on 6-th day after surgery operation:

 

Rat complex

The whole structure of developed ecosystem is:

rat overall

Let's consider the components in more details.

Implant

Implant with sensors inserted under animal skin, sensors are placed inside abdominal cavity. I didn't put corresponding howto picture here, it can be viewed in manual "Implantation protocol" here. I wouldn't say that it's nice picture.

The implant has quite small size and weight to ensure that animal can carry it without significant difficulty. However, its parameters are quite impressive:

150 hours active state, which can be used at any time during 20-day period;

300 mm distance (guaranteed, 5m max)

25x20x8mm size, 6.5g weight.

1 kHz 8-bit sampling.

In addition, it can measure a temperature - sometimes it can be useful to know if animal has some problems.

Here is a photo (7 is just radio link number):

implant with and without a case

Here is next implant generation, but it wasn't used broadly, because of its high cost and complexity in assembly (20 OpAmps, 0201 components). Moreover, most problem is that implantation 4 channels in animal is very hard and percent of death is very high, providing that 4 channels really need rarely.

rat 4 channel

 

Reciever

Receiver is quite simple in comparison with implant. It has no restriction by size and power consumption, it only need to send and capture radio packets from implant, assembly them in big chunks of data and then transfer it to host computer over USB:

reciever

 

Main Server

Main server is usual Windows-based web server that provides data upon request. All it require is regular security updated, to avoid unauthorized moving implant to active state, which reduces battery life.

Researcher workstation

Researcher workstation is usual PC or notebook with Java enabled. It creates TCP/IP link with main server, then receives and shows captured data. 

rat workstation

Final data view is something like this:

cardio picture

"Voltage" is what you think: battery implant voltage at current moment.

That's all I can disclose about the project. You also can look at corresponding materials below:

This leaflet is about BioTelemetry project in simple words (for investors)

This article (on Russian) describes the project in more details, for engineers. And this one - for scientists.

This article (on Russian) describes surgeric implantation process. It's not very strightforward and requires a lot of experience.

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