High-order Shimming
High-order Shimming - Related Videos
06:19
The Mouse Forced Swim Test
0 Views •
Cited by 541 •
2012
The forced swim test is validated as an experimental approach to assess potential antidepressant efficacy in rodents. Experimental animals are placed in a tank of water and escape-related mobility behavior is quantified. The common procedures for the mouse version of this test are described.
05:12
Swimming Performance Assessment in Fishes
0 Views •
Cited by 55 •
2011
The lives of the majority of fish are predicated on swimming. This protocol describes techniques for capturing a range of swimming modes available to individual and schooling fish, and includes metrics associated with swimming physiology and behaviour.
05:42
The Forced Swim Test as a Model of Depressive-like Behavior
0 Views •
Cited by 686 •
2015
This protocol describes the forced swim test, which is used for the study of depressive-like behavior in rodents. This procedure involves placing an animal in a container filled with water that eventually will lead to the exhibition of immobility behavior, which is considered to reflect behavioral despair.
08:47
Automated Analysis of C. elegans Swim Behavior Using CeleST Software
0 Views •
Cited by 17 •
2016
An efficient and simple methodology for computer-based analysis of nematode swimming behavior in liquid is described. The method requires little to no investment for C. elegans laboratories. The hardware used is standard, and the computer software for the behavioral analysis (CeleST) is an open source one.
06:50
Preparation and 3D Tracking of Catalytic Swimming Devices
0 Views •
Cited by 1 •
2016
A method to prepare catalytically active Janus colloids that can "swim" in fluids and determine their 3D trajectories is presented.
FAQs
Higher-order spherical harmonics provide mathematical components for describing shim fields with spatial patterns more complex than lower-order adjustments. Field maps reveal how the magnetic field varies across the relevant volume, and optimization selects the strengths of available components to counter those variations. This spatial matching allows correction of localized or position-dependent errors rather than only broad field offsets.
Lower-order adjustments cannot fully represent inhomogeneities whose strength changes substantially with position. High-order components add additional spatial patterns, allowing the correction field to follow more complicated deviations across an imaging or spectroscopy volume. This distinction matters when residual nonuniformity remains after simpler corrections, especially in measurements that depend strongly on field uniformity.
The technique becomes particularly valuable when the field contains complex spatial deviations, when the sample geometry makes uniformity difficult, or when the experiment covers a large field of view. It is also important when imaging or spectroscopy requires high spatial or chemical-shift resolution, because these conditions make residual field variations more consequential to the measurement.
A typical workflow begins by measuring a field map over the relevant imaging or spectroscopy volume. The observed deviations are then represented using available higher-order shim-field components, and their strengths are optimized to compensate for the measured variation. Applying those optimized components produces a more uniform field, which can then support the intended magnetic resonance measurement.
Improved field uniformity can produce narrower spectral lines, reduce artifacts, and make quantitative measurements more reliable. Narrower lines are especially relevant to spectroscopy, while artifact reduction supports imaging quality. Because the correction is optimized from spatial field information, the resulting benefits apply across the selected volume rather than only at a single measurement location.
High-order Shimming is most valuable in magnetic resonance imaging and spectroscopy when the experiment must maintain field uniformity across a challenging sample geometry or a large field of view. It also supports applications demanding high spatial or chemical-shift resolution. In these settings, improved homogeneity helps preserve spectral sharpness, limit artifacts, and strengthen the reliability of quantitative results.