Tohoku University Cognitive Neuroscience Application Center

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Noise-Cancelling Headphones for MRI

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OptoACTIVE System
During MRI scanning, the noise from the MRI machine is loud. To provide auditory stimuli to the subject, noise cancellation is used to reduce the background noise.

Setup in the Imaging Room

Before the experiment, fit the subject with the specialized headphones.
Place foam between the head coil and the headphones to ensure a tight fit and eliminate gaps, as any gap will reduce the effectiveness of the noise cancellation.

The headphones should be snug but comfortable. Use soft foam to prevent the headset from slipping and firmer foam to secure it in place. Ensure the fit is tight but still bearable for the subject.

Inform the subject beforehand, saying:
"The headphones will be tightly fitted, but if it becomes too uncomfortable, please let us know."

Setup in the Control Room

Connect the audio cable labeled
“NOISE Canceling”
to the PC.

If using both earphones and control room speakers, use an audio splitter.

OptoACTIVE System Setup

Turn on the power at the back of the box.

When the screen says
“Touch screen to continue,”
touch the screen.

Ensure the “FOMRI NOISE CANCELLER” button is in the ON position.

Confirm “Start DSP Mode” is displayed and tap

“Start.”

If the “Status” reads "DSP Disconnected," press the “Hardware Reset” button on the back of the unit.

Once “Headphone Calibration” appears, tap
“Calibrate.”

Perform the calibration when the room is quiet (make sure the MRI machine is not performing any scans) with the door closed and no interruptions.

If calibration is successful, the mark will turn green and a waveform will appear.

Click on the “ANC” button in the top right.

If calibration fails, a red X will appear, and the waveform will flatten. Check for proper headphone connection and ensure there are no gaps, then retry calibration.

After successful calibration, click on the “ANC” button to proceed.

After calibration, begin the survey scan.


MRI Scanning

Press "Learn" to prepare the OptoACTIVE system for MRI scanning.
Start EPI imaging.
Initially, there will be no red waveform in the lower graphs. The system will sample the MRI sound for 16 seconds. This is the "Learn Time," and once the countdown finishes, noise cancellation will start automatically.

Ensure your program waits at least 30 seconds after the MRI scanning starts before presenting the experimental stimuli. The subject must tolerate the noise during this time.

Inform the subject: "There will be loud MRI noise for the first 30 seconds, but the volume will decrease after that."

Confirm that noise cancellation is working by checking the lines:

Blue line: Original MRI noise.
Red line: After noise cancellation.

When the scan ends, press "Stop" to halt the process.
Turn off the system by switching off the power on the back of the unit.

Notes and Precautions

• Due to the limitations of the system, complete noise elimination is not possible. The system can reduce the original noise by approximately two-thirds.
• It's recommended to increase the volume of the stimulus sound to compensate for the remaining noise.
• Noise cancellation cannot be applied during structural imaging (T1 scans).

The main unit is located under the desk.

Power supplies and cables should generally not be disconnected or altered.

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