FAQ

With some fMRI equipment, we sometimes have problems with noise on the images. Is this something we have to worry about with your response pads?

With an all-plastic, all-fiber system you don't have to worry about problems like intermittant noise that can arise unpredictably in any system with wiring in the magnet room. The electronic interface sits next to the computer, and everything after that is all plastic. All of the response pads and pointing devices are light-based, and contain no metal and nothing electronic.

We would like a matching electrical response pad for our mock scanner setup. Do you have a non-fMRI system like the fiber optic one?

Yes. USB Trainers are electrical copies of our fiber optic button boxes. The 2 or 4 button boxes attach directly to the USB port of a computer (no additional power supply). An additional input functions as either a trigger in, or an optical screen refresh detector. Outputs are bootloaded through the USB port can include time stamping.

Our scanner has several different groups using the same fMRI equipment. Some people use EPrime, some people use Presentation, we use both Macs and PCs, and someone wants to use MatLab?. Which of these programs will work with your interface?

All of them. The interface is compatible with every program. With Serial, Parallel and USB outputs, and 8 program options for each the system covers all bases.

I have an idea for a different type of response device I would like to use in an fMRI study. Do you make special "one-of-a-kind" systems?

Yes, one or two special projects like this are on the go at any given time. Components of the standard system can usually be used to complete special projects in a quick and economical way.

We would like a joystick and a response pad. Do we have to buy two complete systems?

You just need to buy 1 interface and 1 fiber optic bundle, and the handhelds you want. There arehave 7 standards handhelds, including up to 8 buttons and two pointing devices.

For our study would like to have a handheld with two boxes, one with 2 buttons and the other with 5. Can you make this for us?

Yes, the interface can be used for up to 8 butttons, or 4 buttons and 2 continuous detectors. Depending on the handheld enclosure, special configurations cost about the same as standard handhelds.

I'm a MEG user and the sound of the button's clicking is a problem. Can you fix this?

The buttons can be made extra quiet for MEG users, please specify when making an order.

I like your response pads, but want the buttons in different places. Can you do this?

Buttons can be easily moved or placed in a different enclosure, and many customers have asked for this. The buttons are actually specially designed optical switches which can be mounted in a variety of ways.

What are the TTL lines for?

These are generally used by people using either the parallel port on their computer, or a special purpose i/o board. Cabling can be provided for either case.

How does the program switch on the interface work?

The switch is read when the interface unit is powered-up, so all you have to do if you want to run the interface with a different software package is a) select the program number you want, b) unplug the power connection and wait a few seconds, and c) plug the power back in.

How do I connect the trigger in?

This depends a little on your scanner. Usually the hardest part is indentifying the appropriate output from your MR scanner. If it is a TTL signal, you can connect it directly to the BNC input on the interface unit. There's a helpful trick for debugging the trigger signal: With nothing connected to the BNC input, you can generate 'fake' triggers by shorting the BNC's center conductor to its cylindrical case, using a paperclip or similar small piece of metal. This will not harm the interface (or you!), but it will result in the interface generating the outputs that would result from a proper trigger signal. This can be helpful because sometimes its not clear if the software is responding correctly to triggers.

Does your interface work with EPrime, Presentation, and Superlab?

Yes.

Our lab developed its own programs. Which output on the interface should we use?

The bitwise serial output is probably the best from a performance standpoint as of today. From a timing standpoint, the TTL output is as good, but it is less universal since it requires a parallel port or special i/o card.

Please tell us if you are interested in having special types of interfaces or protocols. In particular, it would make a great deal of sense to transmit hardware-based timing information along with the button-press information, this can be done quite easily, but there does not seem to be software now that would use this.

We're using a real-time system. How fast is your response time?

The system uses a synchronous modulation and detection scheme to optically scan the buttons, to create high immunity from ambient light fluctuations. The present scanning takes 200 us per button. So 4 buttons systems have time resolution of 0.8 ms (8 buttons, 1.6 ms).

But this answer gives a false impression: the hardware interface delay (through serial, TTL, or USB) and the operating system timing overheads, can severely delay the final reception of the signal by the end software.

We have a new interface that is optically interchangeable with our present one which supports sub-millisecond timing.

Why do I need the fiber optic bundle to go out of the magnet room?

Wires can carry noise into the room. The radio frequency receiver in MR systems is incredibly sensitive (signals at the thermal noise level are routinely measured) and any increase in noise is generally unacceptable because it leads to longer scan times or degraded image quality.

Wires can of course be filtered, and this can go a long way to solving the noise problems that they bring.

But the worst thing about noise is that it's unpredictable, so testing if a system adds noise or not is never a fully convincing effort: it may be fine one day and noisy the next when, say, an elevator motor is turned on, or an electrocautery unit is in use.

Fiber optics provide the most reassuring solution to this problem, as long as they go all the way from the 'outside world', through the penetration panel, and to the response device, because they are not conductors. In addition to eliminating conducted noise, the non-conduction means that subjects are electrically isolated which is a valuable safety point.

Why do I want "no metal and nothing electronic" in the magnet room?

Metals interact with magnetic fields. Ferrous metals are especially dangerous and are often strictly forbidden because they can be drawn into the magnet and harm people or equipment along the way. But even non-ferrous metals like aluminum can create odd problems by interacting with time-varying magnetic fields, as well as by having magnetic susceptibilities that distort the shape of the magnetic field near the imaging region of interest.

Just as wires can carry noise into the magnet room, so too electronics in the room can generate noise. This is generally more of a concern as the electronics in question approach the bore of the magnet, since the proximity to the imaging area is what matters here. Most modern electronics involves switching components, and switching waveforms have broad frequency distributions that can be detected as intermittent radio frequency noise. If there is nothing electronic in the magnet room, this potential noise source is eliminated.

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