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jim.voyvodic
BIAC Faculty
138 Posts |
 Posted - Jun 30 2006 : 10:11:06 AM
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6/30/06
The video and audio stimulus presentation hardware has been upgraded on the 3T in the past week. This upgrade involved 3 separate changes that happened to occur at the same time.
1) The first change was replacing the old video projector with a new projector, because the old one stopped working properly and could not easily be repaired. Not surprisingly, the old model is no longer available so the new projector is somewhat different (hopefully better) than the old one. We have attempted to configure the new display to be similar to what we had before, but if the details of pixel size, field of view, brightness, or contrast are important to your studies you should be aware that they might be slightly different now. Contact Imran or Jim if you find that the current setup does not meet your needs and we will see what can be done.
You should be aware that the new video projector handles changes in video display mode differently than the old projector. In particular, it appears to reset many of its configuration settings whenever the video input resolution changes. This seems mostly to affect the overall size of the display. To avoid problems, therefore, I recommend that all users be aware of what screen resolution setting they wish to use and make sure that the video display is at that resolution while the Tech is putting the subject into the scanner and setting up the video screen. If you care about the edges of the display screen, make sure that your set-up video display has objects near the edges and double check that the subject can see all important screen regions before you start scanning. Keep in mind that changing screen resolution during the session may reset any manual configuration changes made at set-up (this includes switching to the DVD video display, which is always at 800x600 resolution.)
Optimal video screen resolution is to present stimuli in 800x600 display mode. That should prevent configuration changes if using the DVD, and it is the only display mode that works with the new video goggle system. The current projector configuration also supports full-screen 1024x768 display resolution, but if you use any other video mode you should be aware that you may have resizing problems. Be sure to check that each subject can see your entire stimulus before you start scanning.
2) The second stimulus hardware change is the installation of a new set of stereo video goggles from Resonance Technology Inc. These are similar (but not identical) to the video goggles on our 4T scanner. On both scanners the goggles are designed to work in 800x600 display mode. Unlike the 4T goggles, however, THE NEW 3T GOGGLES WILL NOT WORK AT ANY RESOLUTION EXCEPT 800x600. Therefore, before using the new goggles make sure that your stimuli can be presented properly in 800x600 mode, and make sure that when you log into the PC at the scanner it is in 800x600 mode before you start.
When using the goggles it is very important that you remember to give the subject a test image and verify that they can actually see it before you begin your fMRI scans. (With the projector you can see the subject's display, but with the goggles you have to ask them what they see.)
The goggles have been installed as user-device 4 on the video switch (the projector is still user-device 3) so if you want to use the goggles you simply need to tell the MR Tech before the subject goes into the magnet, and you need to select the goggle display (#4) on the video switch.
The new goggles have an integrated eye-tracker device that has not been fully tested but should be available in the next week or so.
3) With the new video goggles we also installed a new audio system on the 3T. If you want to use sound please let the MR Tech know while the subject is being set up, and be sure to test that the subject can hear properly before you start scanning. The 4-button sound switching boxes above the DVD player control which sound source goes to the subject's headphones and to the PC speakers in the control room. Currently the sound works properly from the DVD player, the radio, and the Donders PC. Sound from the Mach PC is not yet working but should be available very soon.
Both the video goggles and audio headphones have been tested for imaging artifacts in a variety of scanning modes. The devices are not completely MR invisible, so you may see them appear faintly in your MR images. They do not cause any imaging artifacts or distortions, however, in any scanning mode tested. If you detect any image artifacts that you suspect may be caused by this new hardware please let Jim, Allen, or Imran know as soon as possible.
regards,
Jim |
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goggles, projector, sound at 3T
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