A first proof-of-principle of a Tinnitus detector circuit

Posted on 27/07/2011 by | 1 comment

Tinnitus is a condition in which a patient perceives an auditory phantom sound that can take the form of ringing, buzzing, roaring or hissing in the absence of an external sound. Approximately a billion of people suffer from tinnitus worldwide, while in 2% – 3% of the population, tinnitus significantly degrades quality of life of the patients and can lead to insomnia, anxiety and depression.

Currently, there are no proven treatments for tinnitus. However, recent research has shown that tinnitus patients can benefit from electrical brain stimulation. In addition, it has been shown that there is a link between tinnitus perception and a change in the energy levels of several electrocortigography (ECoG) / electroencephalography (EEG) frequency bands. For example, the energies of theta (4-8Hz) and low-gamma (30-50Hz) waves increase, while the energy of alpha (8-12Hz) waves decreases during active tinnitus perception. The same studies suggest that the intensity of the tinnitus perception correlates with the amount of the energy increased in the gamma band.

The real-time tinnitus detection method proposed by the BME group detects tinnitus by comparing ECoG/EEG signal energies from different locations in the brain according to a tinnitus "signature". First, the proposed strategy selects appropriate ECoG/EEG bands per channel by means of band-pass filters. Next, their extracted energies are compared to their counterparts from a different (healthy) location. Tinnitus is detected only if higher theta and gamma energies while lower alpha energy is found when compared to the signals from this healthy region. The applicability of the detector is verified by means of circuit simulations with real neural waveforms and is able to successfully detect tinnitus.

Are you interested in any progress related to the tinnitus detector circuit? Stay tuned.

Senad 

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Posted in Education, Electronics, General, Neurostimulation and Neuromodulation, Understanding the Brain

Small chip to overcome inflammation of joints

Posted on 18/07/2011 by | 1 comment

Today, the Telegraaf and Nu.nl report that a team of the Dutch rheumatologist Paul-Peter Tak of the Amsterdam Academic Medical Center will implant a kind of pacemaker, its size in the order of a bout a square centimeter, that will deliver stimuli to the vagus nerve for about one minute a day. By doing so, it is expected that inflammation of the joints of patients that suffer from rheumatoid arthritis can be reduced or even completely stopped.

Of course, what can be deduced from the article is that this pacemaker, electronics-wise, is nothing more than a simple blinking light with a timer, which can be implemented by means of a miniature microcontroller and a battery. However, it is also obvious that electrical stimulation of the vagus nerve, albeit at its infancy, is already very promising and a possible treatment of a wide range of neural disorders and pain is dawning at the horizon.

Wouter

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Posted in Electronics, General, Neurostimulation and Neuromodulation

Be gentle to the heart, otherwise you’ll lose it

Posted on 15/07/2011 by | Leave a comment

Researchers at the Max Planck Institute and Cornell University have come up with a low-energy pulse sequence to
restart hearts and make implants last longer is what we can read in IEEE Spectrum today. Other advantages of using a train (a burst) of pulses instead of using a single (tonic) pulse are that defibrillation becomes less painful to the patient and is less likely to evoke fibrillation elsewhere in the heart. The new therapy still has to be tested on patients, though. 

From this, it is only a small step towards realizing that other types of tissue should be stimulated with burst-like or even more exotic yet gentle pulses, too. In the Biomedical Electronics Group of Delft University of Technology, we’re working on interfacing with the brain in a more natural manner. Stay tuned…

Wouter

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Posted in General, Neurostimulation and Neuromodulation, Pacemakers

New way of data conversion

Posted on 08/07/2011 by | 1 comment

Analog-to-digital converters (ADCs) are indispensable building blocks of wearable and implantable biomedical data acquisition systems. Ultra-low-power ADCs for biomedical signal sensing have witnessed a dramatically reduced power consumption in recent years, but we have to admit that our biomedical systems need more breakthroughs than just squeezing harder in conventional ways.

As is known to all, many biomedical signals are born with a sparse nature. A large amount of redundant digital samples will be thus generated if we use Nyquist-rate ADCs to convert such signals. Most likely, ADC power savings are not a major concern in a system in which transmission power dominates the overall power consumption. However, if this is not the case, from a signal point of view, new ways of sampling or sensing are necessary to further improve the performance of the whole system.

A new and promising ADC approach for biomedical data acquisition is based on so-called level-crossing (LC) sampling, in which samples are generated only when the input signal crosses the threshold levels, so there is no redundant sample in this case. However, the conventional LC-ADC utilizes power hungry comparators and DACs, which causes the LC-ADC to consume much more power than ultra-low-power Nyquist ADCs (e.g., SAR ADCs). In our new approach (mentioned by Wouter earlier in the weblog), innovations at both system level and circuit level enble us to design a more power-efficient LC-ADC. Power consumption is now in the range of hundreds of nanowatts. We are currently investigating the possiblity to further improve its performance and reliability.

Yongjia

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Posted in Electronics, General, Medical Body Area Networks

In case you’ve just missed it…

Posted on 30/06/2011 by | Leave a comment

Fixing the Brain-Computer Interface

Researchers are addressing the sizable population for whom
BCI doesn’t work

By Erica
Westly  /  June 2011

New website (in Dutch): http://www.braininnovations.nl/

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Posted in General

It takes some cooking to prepare a good meal

Posted on 24/06/2011 by | Leave a comment

Frequent readers of this weblog may have started to wonder whether the activities of the Biomedical Electronics Group have gradually fainted and dissolved in eternity, its members have all become hobos and it all ended in a big dream. Bzinga. The truth is, of course, that everybody is very busy and under the yoke of some deadline or another.

Senad and June been working very hard on a first proof-of-principle of a Tinnitus detector circuit. Such a circuit should allow for detection of the spatial properties of tinnitus and give objective information on its severity. This could, in turn, lead to more refined or adjusted stimulation therapies. Don’t sell your mother for it, yet, but expectations are high. The findings will be worked out in a manuscript, to be submitted to the annual BioCAS Conference today.

On the detection side of things, Yongjia has been working very hard on the new type of level-crossing analog-to-digital converter, described in an earlier weblog. Also this work will be submitted to the BioCAS Conference.

Duan Zhao received the good news that our paper (together with the Holst Centre) on a reconfigurable subsampling receiver has been accepted for presentation and publication at the PIMRC Conference in Toronto. Congratulations. He just returned from a visit to his home country and we’re happy to have him back again.

Of course there is more that can be reported, such as the coming ELCA day trip, the preparations for organizing BioCAS 2013 in Delft, the IMDI NeuroControl, more power-efficient neurostimulation circuits, higher-efficiency RF energy harvesting circuits, June’s paper that got accepted in Transactions on Circuits and Systems-I: Regular Papers (congrats, too), Sandro’s and Senad’s paper that enjoyed the same fate (congrats, too), STW Perspectief and how the Dutch Ministries of Economical Affairs, Agriculture and Innovation and of Health, Wellbeing and Sport have no clue on how to increase valorization in the Netherlands (as witnessed yesterday at the MedTech West Event), but this would make good stuff for another blog. So stay tuned!

Wouter

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Posted in General

Mr. Brain: The Role of Neuroscience in Crime Investigation

Posted on 08/06/2011 by | 1 comment

More than a week ago, Wouter recommended a Dutch documentary ‘Mystery of the brain’. I believe that the documentary must be very interesting but unfortunately I don’t understand Dutch… What a pity.

I also would like to share my experience with you all in a way that is more relaxing. There is a Japanese TV series called “Mr. Brain” that we can watch online at http://www.youtube.com/watch?v=pKjHIIK7qew&feature=related.

After being busy with my research, watching it reminds me of myself and my work. It makes me smile sometimes. In these series, we will see how the detective and the neuroscientist deal with each other in a bitter-sweet-funny way. Understanding the brain helps a lot in interpreting the evidences that are left behind at the crime scene. Whenever the story goes to a complicated theory of neural processing there will be animations popping up to explain in a very cute way.

It is also good for kids, I think.

A few useful things I got from watching it:

  • I enjoy eating bananas more
  • I know where to sit in front of the girl I meet for the first time
  • Color comes first, shape follows but sound is the most powerful
  • We are using only 5% of our brain. There are still more than enough resources in our brain
  • For creativity, just don’t give up

Like Neil Yongjia said before singing: “I hope you’ll enjoy.”

June

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Posted in General

Smaller can be better

Posted on 07/06/2011 by | Leave a comment

After the 2011 edition of ELCA Music Festival, I was dragged (by some mysterious power) deep into the idea that came to my mind around three years ago. At that time, I was trying to simultaneously linearize and reduce a transconductance of a Gm cell (V–I converter circuit) for very low frequency biomedical filtering. The linearization and transconductance reduction were successful but the success came prices that I needed to pay:

  1. circuit complexity which is really unfriendly to weak inversion CMOS.
  2. more current consumption which was not surprising. It was very well in line with the circuit complexity. 
  3. more noise contribution (this was also a good friend with circuit complexity).

When I looked into the dynamic range of my design, it was not improved that much from that of an ordinary differential pair circuit (even so the paper was published [1] :). Then I got an idea that ‘instead of inventing a sophisticated linearization technique to obtain larger dynamic range, trying to use as less as possible noisy circuit elements and forget about linearization are more reasonable for biomedical signal processing which requires a good deal of power reduction’. The idea was left there since then for two reasons: I had other jobs to do and the idea seemed too sloppy.

Let me tell you more about the mysterious power. Several times we did rehearsals before the ELCA festival. I was in charge of acoustic guitar and harmonica for the song called ‘The end of the world’ http://www.youtube.com/watch?v=KmnKCE99sYE. Playing two instruments at the same time made me tired and it did not make a good harmony as expected. So I stopped playing the guitar and exercised only the harmonica (of course combined with the piano from Wouter, the electric guitar of Mark and Wannaya’s voice (I could not find this song on our Youtube channel — don’t know why). The song turned out better than before and this reminded me of that sloppy idea!!!

I did an investigation and found that there are strong evidences supporting my idea founded in low-pass filter design [2] [3]… It works!!! Large dynamic range was achieved as well as a very good figure of merit. Although the above filters were dedicated to communication systems rather than for low frequency biomedical signals, the underlying concept of the filter should be applicable for biomedical signal as well. Only a bit more effort was needed to work it out.

Good news!!! Recently, with the help from Senad, who has become 22 years old today — the same as me :). Happy Birthday!!!— my sloppy idea was realized. A 6th-order ECG low-pass filter with a large dynamic range of 59dB and extremely low power consumption of 0.45nW has been designed. We plan to submit this work to BioCAS2011. Hopefully, the reviewers will like it, too.

More good news!!! The application is not limited to low-pass filters only. I’m developing this idea further to apply it for a cochlear channel band-pass filter. What I can say now from the circuit simulations is that the filter provides the best figure of merit compared to state of the art designs. The secret is that all terminals of a single MOSFET device are being used, one pole and one zero are achieved by only two transistors sharing the same bias current.

Next time, I will tell you more about this. Stay tuned if you are interested!!!

Healthy Haring is coming. I heard from Marijn that this year, since the weather is warm, the fish is growing bigger. See you in the Pub this coming Thursday for Harings and Beers 😀

June

[1] C. Sawigun, D. Pal and A. Demosthenous, “A wide linear range transconductor subthreshold transconductor for sub-Hz filtering,” Proc. IEEE ISCAS, pp.1567-1570, 2010

[2] D. Python, A. S. Porret and C. Enz, “A 1V 5th-order Bessel filter dedicated to digital standard proceses,” Proc. IEEE CICC, pp. 505-508, 1999

[3] S. D’Amico, M. Conta and A. Baschirotto, “A 4.1mW 10MHz fourth-order source-follower-based continuous-time filter with 79-dB DR,” IEEE J. Solid-State Circuits, pp. 2713-2719, Dec. 2006

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Posted in Electronics, General, Pacemakers

BME Youtube Channel

Posted on 30/05/2011 by | Leave a comment

Only three months ago the Biomedical Electronics Group started this weblog to give the world a glimpse of what we are doing. More than 30 blogs have been written so far on our daily thoughts and projects and we’re still going strong! 

Today, we created our own "BMETUDelft" youtube channel!! The first few videos have already been posted. Here an impression of the atmosphere during the ELCA festival 2011 while the ELCA band plays Drunken Lullabies!!

http://youtu.be/18jmQCklfog

This youtube channel will also be used to explain our research areas. This short animation movie explains the concept of the Smart Implantable Neuro-Stimulator that we are developing:

http://youtu.be/UX56ibySb3I

So check out our youtube channel named BMETUDelft. We will soon post more videos, so stay tuned!!

Mark

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Posted in General

Dutch documentary on the Mystery of the Brain (6 episodes)

Posted on 28/05/2011 by | Leave a comment

BreingeheimLast Tuesday I saw an excerpt of an interesting episode on Dutch television about what happens with the human brain when it ages and in particular what happens with it in the unfortunate situation of Alzheimer’s disease. This episode, presented by the well-known and charming Dutch news presenter Charles Groenhuijsen, in fact is part of a larger series that tries to shed some light on what happens in this 1.5kg human organ that is at the base of all our thoughts, actions, emotions, etc., of which its intricacies and inner workings are still a mystery to us. 

The complete series (in Dutch) can be viewed from Uitzending Gemist and also from the following link of Omroep Max: http://www.maxbreingeheim.nl.

Highly recommended!

Wouter

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Posted in General, Understanding the Brain