Echo Planar Imaging
Echo Planar Imaging - Related Videos
16:31
Echo Particle Image Velocimetry
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Cited by 10 •
2012
An echo particle image velocimetry (EPIV) system capable of acquiring two-dimensional fields of velocity in optically opaque fluids or through optically opaque geometries is described, and validation measurements in pipe flow are reported.
01:06
Echo
0 Views •
2023
The human ear cannot distinguish between two sources of sound if they happen to reach within a specific time interval, typically 0.1 seconds apart. More than this, and they are perceived as separate sources. Imagine the sound is reflected back to the ears. Assuming that the source is very close to the human, the difference between hearing the two sounds—the emitted sound and the reflected sound—may be more than the minimum time for perceiving distinct sounds. If this is the case, then the...
09:25
An Endothelial Planar Cell Model for Imaging Immunological Synapse Dynamics
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Cited by 3 •
2015
Adaptive immunity is controlled by dynamic 'immunological synapses' formed between T cells and antigen presenting cells. This protocol describes methods for investigating endothelial cells both as understudied physiologic APCs and as a novel type of 'planar cellular APC model'.
10:49
Planar and Three-Dimensional Printing of Conductive Inks
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Cited by 58 •
2011
Planar and three-dimensional printing of conductive metallic inks is described. Our approach provides new avenues for fabricating printed electronic, optoelectronic, and biomedical devices in unusual layouts at the microscale.
07:01
Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
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Cited by 5 •
2016
A scanner for imaging magnetic particles in planar samples was developed using the planar frequency mixing magnetic detection technique. The magnetic intermodulation product response from the nonlinear nonhysteretic magnetization of the particles is recorded upon a two-frequency excitation. It can be used to take 2D images of thin biological samples.
FAQs
Echo Planar Imaging samples image information rapidly while traversing k-space with a sequence of gradient echoes. Because the acquisition depends on this rapid traversal, local variations in the magnetic field can alter the measured signal and spatial encoding. The resulting sensitivity helps explain why EPI can show susceptibility distortion and signal dropout, particularly in neuroscience images.
The frequency-encoding gradient rapidly alternates, while the phase-encoding gradient steps through successive positions. Together, these gradients move the acquisition through k-space after one radiofrequency excitation. This coordinated pattern makes it possible to collect the information needed for an image or image volume quickly, supporting measurements that must be repeated over time.
The principal tradeoff is that rapid acquisition increases sensitivity to motion and magnetic-field inhomogeneity. EPI can therefore acquire whole-brain information efficiently, yet the images may contain geometric distortion or regions of lost signal. Careful correction is important when comparing measurements across brain areas or interpreting changes in neural activity and tissue structure.
An acquisition begins with a single radiofrequency excitation, followed by a series of gradient echoes. The frequency-encoding gradient alternates rapidly and the phase-encoding gradient advances step by step as k-space is traversed. The collected information produces an image or image volume, after which susceptibility-related distortion and signal dropout may require correction.
In functional MRI, repeated EPI measurements track blood-oxygen-level-dependent signal changes over time. This time-resolved sampling allows investigators to examine patterns associated with neural activity and to study connectivity across the brain. Its rapid coverage is particularly valuable for whole-brain experiments in which signal changes must be related to an evolving task or condition.
EPI supports diffusion MRI, which assesses water movement in brain tissue. The resulting measurements provide information relevant to structural pathways rather than only time-varying neural activity. In neuroscience, this makes the technique useful for examining how tissue organization and pathway-related properties complement functional measurements obtained from blood-oxygen-level-dependent imaging.
Researchers must account for susceptibility distortion, signal dropout, and motion sensitivity. These effects can make brain regions appear displaced, reduce the measurable signal, or complicate comparisons between scans. Correction is therefore an important part of interpreting EPI data, especially when the goal is to map neural activity, connectivity, or diffusion-related structural pathways across the whole brain.