Susceptibility Artifact Correction
Susceptibility Artifact Correction - Related Videos
01:09
Quantitative Susceptibility Mapping of a Human Brain Using Ex-Vivo Magnetic Resonance Imaging
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2025
Quantitative susceptibility mapping, or QSM, quantifies the magnetic susceptibility of brain tissue, which reflects its cellular composition, like myelin content.Begin by acquiring ex-vivo magnetic resonance imaging or MRI data of a fixed human brain hemisphere.Use 3D gradient magnetic fields to magnetize the tissue and collect signals at multiple time points or echoes to reduce background noise and artifacts and enhance the signals.Generate phase maps for all echoes, ensuring the removal of...
01:15
Distance Corrections
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2025
To achieve precise distance measurements, especially in surveying and construction, certain corrections must be applied to account for potential sources of error like the standardization errors, temperature variations, and slope adjustments.Standardization error emerges when measurement equipment undergoes changes, such as wear, repairs, or weather impacts. To address this, surveyors compare the equipment’s readings to a standard. This process identifies any deviation that might lead to...
01:20
Power Factor Correction
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2024
The power transmission to a factory involves the transfer of apparent power, a combination of active and reactive power. The power factor measures how effectively electrical power is converted into useful work output. The ratio of the real power (KW) that does the work to the apparent power (KVA) supplied to the circuit. A poor power factor means the inductive electrical load absorbs more reactive power, causing a low lagging power factor. This results in large voltage drops across the load...
03:59
Surgical Correction for Pediatric Epiblepharon and Trichiasis
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2025
Here, we present a protocol for surgical correction for pediatric epiblepharon and trichiasis.
03:18
Stimulation of the Intracardiac Nervous System to Assess Susceptibility to Arrhythmia
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2025
Source: Jungen, C., et al. Impact of Intracardiac Neurons on Cardiac Electrophysiology and Arrhythmogenesis in an Ex Vivo Langendorff System. J. Vis. Exp. (2018).The video demonstrates an ex vivo technique for stimulating the intracardiac nervous system to assess the heart’s susceptibility to arrhythmia. Using a perfusion apparatus, an isolated mouse heart is perfused with an oxygenated buffer. The intracardiac nervous system is then stimulated at a high frequency to induce arrhythmias.
FAQs
Field maps provide an estimate of spatial variations in the static magnetic field. These variations indicate where susceptibility-related field changes may shift signal location or reduce its reliability. Correction methods use that information to calculate how image data should be adjusted, helping restore a more accurate spatial representation for later anatomical alignment and functional analysis.
Images acquired with reversed phase-encoding directions provide complementary information about geometric distortion. Comparing the two acquisitions helps estimate how affected voxels have been displaced and supports an unwarping step during processing. This approach is especially useful when a field map is not the selected way to characterize spatial changes in the static field.
Interfaces between air and tissue can produce strong local magnetic-field changes, making signal loss and geometric distortion more pronounced. In neuroscience, the sinuses and ear canals are therefore common locations where functional MRI data become incomplete or spatially inaccurate. These effects may obscure nearby cortical and subcortical regions and complicate interpretation.
Correction can address susceptibility effects through several complementary strategies. Estimated field variations may guide improved shimming, while image reconstruction can be adjusted to account for the altered field. Thus, the goal is not limited to repositioning distorted voxels; it can also improve the image formation process and preserve information needed for downstream analyses.
A practical workflow begins by acquiring either a field map or images with reversed phase-encoding directions. The data are used to estimate spatial variations in the static field, after which the selected reconstruction or correction step adjusts the affected image. Researchers can then assess whether anatomical alignment or functional analyses are more reliable.
In neuroscience, correction is most valuable when functional MRI targets regions near the sinuses or ear canals, where artifacts can hide relevant cortical or subcortical signal. Improved images support more dependable functional localization and connectivity analyses, while also making comparisons across participants or scanning sessions more meaningful.