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lduffell46
02-22-2010, 02:39 AM
Dear colleagues,



Thanks so much to everyone that took the time to respond to my post regarding wireless EMG. In general, there was a very positive response regarding wireless systems. Most responses commented on good quality signals that were comparable with wired systems.



I think overall the points to be aware of with wireless systems are any loss of signal due to connectivity issues, and the time delay due to the A/D - D/A conversion: this varies from system to system but it seems important to ensure this delay is consistent in order to compensate for it easily once your data has been collected.



A number of people commented on reduced set up time and ease of use of wireless systems, particularly when taking EMG measurements from children where wires are likely to get in the way and tangled.



I have posted all responses below, organised by manufacturer/model. Please be aware some of the responses are made by manufacturers of the systems and not users.



Thanks again,



Lynsey.



General comments:



The main problem with wireless system are known like limited bandwidth, the bad A/D - D/A-conversion and the time shift.

If you need the maximum bandwidth, clear signal, no time shift, stay with the cable.

There is one exception: a full digital system, but the Vicon system has no digital port.

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One important point to note is that none of the wireless EMG systems that I have seen (ZeroWire or Myon) have any in-built filters to process the data before it gets to the PC - these systems provide pure, raw data that can then be post-processed on the PC. This is compared to all of the hard-wired EMG systems that I have seen, DO include some form of signal filter built into the system, therefore please take this into account when you comparing the signal quality.



I have also heard some comments from the community that using a wired system with low voltage signals merely turns the cable into an antennae! I have not tested this so cannot comment either way, however, to my mind it certainly could be plausible to some level.



Delsys Myomonitor

We've got both hard-wired and telemetry/data logger versions of Delsys EMG systems and they both produce excellent signals. I've not used the telemetry system with our VICON (hard-wired works fine), but I wouldn't envisage any problems.
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We are in the process of ordering a new Wireless system - compatible with Vicon NEXUS too.

We had very similar concerns and have looked into a few different manufacturer's systems.

The one we have decided to pursue is the Semi-wireless "Myomonitor IV" system from Delsys USA. Please follow the link below:

http://www.delsys.com/Products/Wireless.html

We decided upon this system as it has less bulky sensors, the data-logger unit is lightweight and self-contained, allowing the patient to walk unhindered by a connecting trailing wire and we work with CP children who can get tangled up in a trailing wire.

As I understand it, the data-logger unit communicates wirelessly real-time or after data has been stored/logged it can be downloaded to a separate 'base' unit which is wired into the PC and Vicon system when in use.

An 8-channel system costs 11,000 and a 16-channel one will set you back 13,000.
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I have been using an 8 Channel Delsys Wireless Myomonitor EMG system (www.delsys.com) for the past year and a half and I have been very pleased with the quality of the EMG signals it collects. I have not had this system synched with a motion capture system or force platform yet but plan to set that up in the next couple of months. I have also had great dealings with a number of people from the company and they are always quick to respond if I have any questions about their system.
The system I have can be upgraded to 16 channels as well. I have used this wireless system on the skating rink, around a running track and in various other sporting environments and very rarely have my research students had any issues with losing wireless connectivity during the data collection session. Sometimes my students have had minor issues at the start of data collection getting the Myomonitor to initially start communicating with the computer, however, I think this is more related to Windows Vista than anything. But as I said, generally we have very little problems once we get the system running and communicating with the computer. The system can also be switched to a datalogger mode which allows you to collect data without a wireless connection to the computer. The little logger or computer that runs and collects the data is quite light and we just place it in a small backpack and have the athlete run around. The system comes with a little belt that allows you to attach the unit around one's waist as well.
With respect to the signal itself, the quality of the signal has been great and the leads are very resistant to being damaged. We have put this system through a number of very dynamic movements (ice skating, sledge hockey, sprinting, jumping and cutting) and have had no issues with the wires or leads. I have used a Bortec EMG system and a wireless Biovision EMG system in the past at other laboratories and for what I want out of the data, the Delsys signal quality is certainly comparable to the other systems. I do tend to focus more of my analysis on the linear envelope and magnitude of the EMG signal and less on the frequency content of the signal.
The EMGworks software that controls the wireless computer has worked well in my lab. I would like to see a few improvements in this software (i.e. the way triggering or data collection is started and the elimination of a small delay when starting to capture the data) but for the most part, the software is more than adequate. From an analysis point of view, I do not use their software to analyze the data and instead export the raw data into Matlab and then use a custom written in-house software program to process and analyze my data. But I have noticed that the analysis program that comes with the Delsys system does have many different options in how to handle the data.
You can also attach other sensors to the system such as foot switches, triaxial accelerometers and goniometers and I have had good luck with all of these sensors.


Delsys Trigno (+ accelerometers)


Take a look at the Delsys trigno wireless emg... I've seen/used it a couple of times in demonstrations now and it's a very clean signal. Also allows integration with vicon. We currently have a bid in to purchase one.

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One thing I would recommend you check out is a new product by Delsys called the Trigno Wireless System. This is a 16 channel EMG system with 48 accelerometer channels. This system is completely wireless from my understanding and you do not even have wires going to the individual sensors. I have not had any experience with this system but it's definitely a system that I will look at in the future when I obtain some external funding.



Aurion Zerowire

With our Vicon system we bought the Aurion ZeroWire EMG system http://www.aurion.it/. In general we are very satisfied with it. The signal quality is excellent and the advantage that the subject is completely free of wires is really great. We had experience with a wired system (TMSi Porti), which in itself was very good, but -especially with children- the wires are always a hinder. The main disadvantage we found with the Aurion system is that we have already returned 3 defective amplifier/transmitters in two years. The recharchable battery is probably the culprit.

Aurion has a separate (very small) unit as an amplifier, A/D converter and radiotransmitter, each with its own frequency, up to 16 channels. The receiver has analog outputs, so it can be directly connected to the Vicon A/D-card.
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2 years ago the hospital took the new Vicon system and also the ZeroWire system for EMG, by the Aurion, perfectly and easly integrated in the Vicon system. I knew that the physioterapists used ZeroWire in their clinical tests, replacing totally the old wire system. Probably less accuracy (but not so less as in the past) but really more avaibility for movements (especially in case of 5 years old children equipped by 35 markers and 8 canals of EMG.)

I knew that many different structures bought it, you can find a short and not complete list on the company website (there isn't my hospital).

Here, the link: http://www.aurion.it/
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We are using a wireless system called ZeroWire (http://www.noraxon.com/aurion/zerowire.php) and have been getting very good quality signals. The one surprising drawback of this system is surprisingly low quality of connectors, however the quality of the data is good and I would definitely recommend it for gait analysis where the wired systems are far more limiting.
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The Aurion zerowire system is a good one working well with vicon.
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here at University of Verona, Italy, we are using a Vicon system with Aurion ZeroWire EMG wireless system (Aurion srl, Milan, Italy).

I have not had the possibility to compare the quality of the signal with a wired system, but in my opinion this system provides clear EMG signals and is very functional because you have for every channel only a small box with the two electrode wires and no other weights to be delivered by the subject.

Myon

the company selling the vicon system in europe (www.prophysics.ch) has just released a new wireless emg system and the quality of the signals is really outstanding. You might visit their homepage or call them directly.
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The EMG system is called Myon, and you can view the web pages and download the brochure at www.myon.ch.



I won't repeat the technical details of our system to you, since these are available via the above link. However, I would like to point out the following advantages of a fully wireless system compared to a wired, or semi-wireless one:



1) Ease of use. I don't know if you've tried using a fully wireless system where each sensor has its own transmitter, but in my experience, clinicians find that attaching sensors to a patient without having to route cables to a central backpack is advantageous, both in terms of time and in terms of comfort for the patient.



2) Signal quality. There is no reason why a wired system should have better signal quality than a wireless one, in fact the opposite should be true. A wireless system with transmitters for each sensor has only very short wires from the actual electrode to the transmitter. The signal is therefore digitized almost straight away, instead of having to travel along a long wire which picks up all sorts of movement artefacts whilst moving through the magnetic and electrical fields that inevitably exist in labs full of modern equipment.



Speaking for our own system, we've put a lot of effort into both the above mentioned points, and have achieved a signal-to-noise ratio that compares very well with the competition, whilst keeping the system plug-and-play and really simple to use. For example, our technology means that no ground electrode is necessary (i.e. just two electrodes per muscle), and also that the latency of the wireless transmission is fixed at 16ms, which is due to our own proprietary wireless transmission protocol that guarantees the latency (unlike wireless LAN or Bluetooth, which do not have a guaranteed latency)


Personally, I have been mostly involved in the software development, and here we have something quite unique for Vicon users, namely EMG processing software that is integrated with Vicon Nexus as plug-ins in the processing pipeline. In practical terms, this means that you can capture synchronized EMG with the Vicon data, and then perform advanced processing on the EMG data from within the Vicon Nexus software - unlike other systems, where you would have to do the EMG processing in separate software packages.



The software has the following key features:

* Lowpass, highpass and notch filters.

* Smoothing (moving average & RMS)

* Frequency-based analysis (Fast Fourier Transform & automatic identification of mean & median frequencies).

* Automatic identification of key events such as muscle activity onset and off.

* Automatic calculation of key parameters, such as muscle timing or integrated EMG.

* Integration with the kinematic gait events from the Vicon software, so that parameters can be normalized (e.g. Muscle X fires at Y% of the gait cycle).

* Export of all EMG data and calculated parameters straight to Excel for further analysis.

* Export of all EMG data and calculated parameters straight to Word for reporting.


Our system is relatively new on the market (launched last summer), but we already have more than 20 customers. We're currently trying to promote our system a bit more in the UK, so I hope this is of interest to you.

BTS FREEEMG/POCKETEMG


There is a similar system from BTS http://www.btsbioengineering.com/Electromyography/FREEEMG.html, but this has a digital and no analog outputs, which makes it in fact impossible to connect with non-BTS motion capture systems---

in my lab I use 2 different wire less systems from BTS Bioengineer - www.bts.it



They works very well.

The PocketEMG I have permit surface and needle EMG with different freqeuncy settings and a very handly software. We have the 16ch systems http://www.btsbioengineering.com/Electromyography/POCKETEMG.html



The second systems we have is the FreeEMG totally wire less (without patiente unit). We have the 8ch but is possible to arrive a 16ch http://www.btsbioengineering.com/Electromyography/FREEEMG.html



They are easy to use and works very well.

For gait analisys you can use both system, but if you would like to do more advanced analisys (jumping or running) FreeEMG is better because patiente unit is not necessary. FreeEMG is also very quickly to place on the patient instead pocket, because you not need to fix cable/wire (amplification movment artifacts).

Quality of the signal is very good but FreeEMG for now works at 1Khz. (they should arrive at 2Khz in this year), Pocket arrive at 4Khz just now with 16ch and foot switch. And if you want to use for neuromuscular testing (M-wave or twitch interpolation) you must use the PocketEMG.
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Another wireless system is the one produced by BTS, but I heard some people complaining about it.
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I would like to introduce a EMG system with wireless and semi-wireless system for your referece.
The system is from Italy and called BTS.,

You also can see the detail in their website http://www.btsbioengineering.com/.

As your need, I can refer to PocketEMG and FreeEMG system. I had the experience in intergrating the FreeEMG or PocketEMG system into Vicon system to get sychronization and high quality signal.
BTS can provide you a complete system and total solution in motion analysis, the specification of Pocket and Free as attached for your reference.
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A BTS client has been passed on your details following a request that you put on BIOMCH-L on Friday; regarding wired/wire less EMG systems.
My name is Scott Barton; Sales Manager for BTS Bioengineering. BTS are a global leader in providing kinematic, kinetic and EMG solutions.
In response to your email I would like to offer you a no obligation demo of both of our systems the BTS Pocket and BTS FREE EMG this way you can establish with your own findings which you think would be preferred for your study. I'm happy to do some mini trials of your request so that you can see what provides you with best signal, functionality etc.
The obvious benefits that the wire less systems have to offer are of a dramatic reduced set-up time of the patient and also for the first time the patient has full range of movement.
BTS Bioengineering were the first company to launch the wire less technology which was almost two years ago and remains a market leader following in the steps of their powerful wired system the Pocket EMG.
I understand that you are interested also in Motion Analysis System and mention in your email that you have or are purchasing a Vicon system. If this decision has not been finalised then I would be very interested in discussing with you the possibility of a BTS SMART-D Motion System which will offer equal performance with better features than the Vicon System. And also the advantage will be that no matter which EMG system you require it will have seamless integration as BTS are the only company that can offer this one system integration.
We already have a SMART-D System in the Imperial College which has been in place now for nearly two years and I'm sure if you require a demo or testament from the department at Imperial College I can arrange for you. They also chose the BTS SMART-D against the Vicon System.
I can also assure you in this case that I will be able to offer you a price for both a Motion System and an EMG System with a fully comprehensive two year warranty for a cost that won't be beaten.

TMSI


TMSi http://www.tmsi.com/?id=5 makes now a 8-channel unit with one Bluetooth transmitter, at a favourable price. So here you have still 8 leads from the electrodes to the transmitter unit, but none from subject to base station. We have no experience with this system.
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We evaluated lately a EMG-Systems for general use, but asked always if they would work with the Vicon-System.



The best digital mobile system was:

TMSI (tmsi.com), a digital system, usable for EMG, ECG, EEG, footswitsches, goniometer, etc.

A 16 Channel System will be bought in Summer 2010 by the Physiotherapy of the Bildungszentrum Gesundheit BZG, Basel (www.bzgbs.ch)) for research and teaching

KinePRO

I just wanted to point out our fully integrated 2D motion capture and wireless EMG system, KinePro.



Also our wireless EMG can be integrated with Vicon, Qualisys and other systems. This is confirmed by tests.



We state that the quality of our wireless EMG is higher than of a typical wired EMG. There is less noise and it is quicker to apply than many wired systems. We have confirmed this by testing.



Motion Lab MA300

We sell a range of wired EMG systems (see http://www.motion-labs.com) that have a radio-telemetry option that might interest you.



In general, with radio telemetry systems the user sacrifices signal bandwidth, flexibility and signal integrity for the convenience of not having a cable attaching the subject to the computer. Our MA300 systems were designed as cabled system originally so they have all of the advantages of high signal bandwidth (up to 2kHz per channel), flexibility (use gel electrodes, fine-wire electrodes, surface electrodes, as well as event switches, goniometers, EKG etc) and the certainty that you get with a wired system, that the EMG data is accurate and is collected synchronously with the 3D marker information.



We now offer a wireless option to the MA300 systems that replaces the cable with a wireless link, while retaining all of the advantages of our wired system. The result is that our wireless performance is identical to our wired performance and you can switch between the two transmission methods in seconds if you wish.





You mention that you are collecting data via a 3D motion capture system - so you may want to record EMG data and 3D data at the same time. One question to ask any wireless vendor is "What is the delay between seeing a signal at the EMG system input and recording the signal at the EMG system output?"



Many wireless systems cause a delay of in the EMG signal that results in the EMG signal arriving up to several frames late (15-40ms) when the data is recorded.



Another issue with many EMG systems, and common with wireless system is EMG signal fidelity - particularly the way that each EMG channel responds when the signal input rapidly changes from one value to another - engineers call this "step response".



Many wireless EMG systems use signal filters that produce the sharp filter cut-off required by the wireless system; but this can result in ringing (oscillations that slowly decreasing in amplitude) in the EMG channels that can distort the EMG data.



Konisberg

Konigsburg in Pasadena has been a great system for us for the last 20 years both in quality of product, reliability, and in service.

http://www.konigsberginc.com/



DataLOG (W4X8)
I saw your posting on the Biomch-L board and thought you may find our product information of interest. We manufacture a wireless (Bluetooth) 8/channel DataLOG (W4X8) which is used for a variety of sensors including EMG. The W4X8 and low-profile SX230-1000 EMG sensors(see website for photo) is used worldwide for data collection. You will also find a number of reference articles under the Publications section of our website relating to these products.

Biomechanicsweb
What a great honor know your inquiry from BIOMCH-L@NIC.SURFNET.NL, we are a unique manufacturer of biomechanics' devices in china .and also include Wireless EMG , Force Plateforms and Pressure Measureing System.
We have experienced saled our Wireless EMG , Force Plateforms and Pressure Measureing System domestic and overseas nearly 6 years.And as a sponsor of International Society of Biomechanics .
Pls browse our website http://english.biomechanicsweb.com/ get more info,and tell us your view directly at any time without any hesitation .

Lynsey Duffell PhD
Division of Surgery
Department of Cancer & Surgery
Imperial College London
Room 7L13 Charing Cross Hospital
London W6 8RF
Email: l.duffell@imperial.ac.uk

www.imperial.ac.uk/osteoarthritis
Medical Engineering Solutions in Osteoarthritis Centre of Excellence
Funded by the Wellcome Trust and the EPSRC
Using emerging technologies to change the paradigm by which osteoarthritis is managed