The Challenge:

Cancellation of local imaging artifacts caused by air/tissue interfaces

Imaging at high fields where efficient compensation of the subject’s magnetic susceptibility is essential

Compensation of de-shimming due to respiratory or cardiac motion
Correction of thermal drift of ferro-magnetic (passive) shims
Dynamic Shimming

The Load&GoTM shimming technology allows for dynamic shim updating and real time shimming on multiple slices, voxels or regions of interest with simultaneous compensation of shim induced eddy currents.
A one-time setup enables the DSU shim induced eddy current compensation capabilities. Individual shim characteristics of each scanner are measured during the setup. Initially data is acquired on shim induced eddy currents; their self time constants together with B0 offset and associated time constants are then calculated and all data are stored in the Load&GoTM non-volatile memory.
Compensation of Shim Induced Eddy Current – a One-Time Setup
A one-time setup enables the DSU shim induced eddy current compensation capabilities. Individual shim characteristics of each scanner are measured during the setup. Initially data is acquired on shim induced eddy currents; their self time constants together with B0 offset and associated time constants are then calculated and all data are stored in the Load&GoTM non-volatile memory.
Dynamic Shim Update – Customized Settings for each Patient
A 3D B0 map of the target region is acquired and decomposed into its spherical harmonics constituents; their composition is then analyzed and optimized shim values for each slice are calculated.
The imaging system downloads each slice settings into a separate file in the Load&GoTM system.
The console sequence control is programmed to generate a TTL trigger synchronously with image acquisition of a given slice. The TTL pulse causes the corresponding shim file to be loaded into appropriate Digital-to-Analog Converters (DAC) and shim currents are set to the required values. This loop is repeated for each slice.
The average time for file loading is about 50 ?s and shim amplifier stabilization is approximately 1 ms, with no impact on the total data acquisition time.
A Comparison with Standard Technology and Specifications
Output channels
6 to 32
Offset channels (optional)
4 (X, Y, Z, Z0)
Maximum voltage output
+/-5V or +/-10V differential
GPA interface
Via MXC unit +/- 1A per channel
Packaging
19” x 4U x 24 “
Z0 Compensation - Yes
115 or 230 VAC, 50/60 Hz
Cooling system
Forced air
Setup control
RS-232
Operating control
Customer specific
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