GE OPTIMA MR360 Service Training page 184

Along with the new 6-channel Grafidy fixture defined in the previous slide, improvements
have been made to the Grafidy calibration's data acquisition and software. The tool first
verifies proper fixture placement and signal from all channels. It then acquires data
simultaneously from all channels, thus reducing calibration time. With the new fixture and
new Grafidy software, Grafidy calibrations take about 45 minutes on BRM and CRM systems
and about 1.5-2 hours on TRM systems. In addition, the user interface has been modified.
In Manual Mode, the UI has changed from "coil placement" centered to "applied gradient"
because now one gradient can be pulsed to get data from all six coils
instead of just two as in the previous Grafidy releases. For 1.5T, as compared to previous
Grafidy, with the new software, using data from all six coils together allows for more
accurate B0 component. Also, after changing calibration factors, the UI does not allow the
user to exit without collecting data, and the number of significant digits displayed has been
reduced to make the values more readable. Grafidy can now compensate very long time
constants more accurately. The new Grafidy software allows for much better compensation
of the initial part of the eddy current curve in long mode because of three things: 1) there is
an additional time constant used 2) all data is now used (as opposed to data starting at
2.5msec before) and 3) software allows for negative amplitude.
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