| T O P I C R E V I E W |
| allen.song |
Posted - Nov 21 2005 : 09:49:51 AM
Late last friday, I found another problem with the zoom part of the twin gradient system, which is responsible for the high slew rate of the spiral-in scans. Jerry and GE engineers have replaced the gradient amps over the weekend, however, I have not been able to reach a stable condition with the spiral-in sequence. The peak-to-peak noise level on the phantom was higher than 10%, which normally should be less than 1%. The spiral-out scans, however, did appear to have stability within the specs. This may be due the fact that the center of the k-space data is acquired first for spiral-out scans, when there is no gradient present.
In summary, I am suspecting a hardware failure on the zoom gradient coil itself, which would lead to additional down time on the 3T. I will be talking with John Chiminski, the general manager of the GE Medical Systems today, to find a prompt solution. Will keep y'all posted. Thanks for your patience.
Sincerely,
Allen Song |
| 5 L A T E S T R E P L I E S (Newest First) |
| allen.song |
Posted - Nov 22 2005 : 5:38:37 PM
After installing the mechanical clamps, Jerry (the GE service engineer) ran into a problem bringing up the scanner due to a communication failure between the scanner hardware and the console. He is going to come back tomorrow morning to continue working on the scanner - he has been here for 12 hours today.
As such, I was not able to conduct my tests to investigate the stability. All scans for tomorrow morning will need to be cancelled. |
| allen.song |
Posted - Nov 22 2005 : 4:36:58 PM
As of 4:30 pm, Tuesday, Jerry is finishing up the mechanical part of stablization process. I am waiting to test the effectiveness of the new clamps that he put in. I will keep you updated on the test results later today.
Even though the scanner can perform anatomical, spiral out, EPI and DTI scans, we still had to cancel one such scan today because GE wanted to install the clamps. We are sorry for the inconvenience this may have caused you. |
| tharsh |
Posted - Nov 22 2005 : 10:42:41 AM
To keep everyone informed: After much work by Allen, Jerry, and Susan, it has become apparent that the gradient coil is not the problem, but instead the problem is vibration produced by the imaging sequences. A fix is being worked on for this problem. Until that is complete, the status of the 3T is the same as described above.
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| tharsh |
Posted - Nov 21 2005 : 3:44:52 PM
The 3T's status will be the same for tomorrow (Nov 22). Spiral-in scans will not be available. However, anything using spiral-out, EPI, or just anatomical imaging will work fine. We are working with GE to find and correct the problem, and will try to keep everyone informed.
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| smusic |
Posted - Nov 21 2005 : 10:13:12 AM
If any of the scans scheduled on the 3T are anatomical only, spiral-out, or EPI, don't cancel - Allen says those scans can be done.
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