Mri Gradient Echo
Mri Gradient Echo - Related Videos
10:00
Gradient Echo Quantum Memory in Warm Atomic Vapor
0 Views •
Cited by 2 •
2013
The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.
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...
06:06
Optogenetic Functional MRI
0 Views •
Cited by 15 •
2016
This protocol describes the steps and data analysis required to successfully perform optogenetic functional magnetic resonance imaging (ofMRI). ofMRI is a novel technique that combines high-field fMRI readout with optogenetic stimulation, allowing for cell type-specific mapping of functional neural circuits and their dynamics across the whole living brain.
10:26
A Multicenter MRI Protocol for the Evaluation and Quantification of Deep Vein Thrombosis
0 Views •
Cited by 5 •
2015
The goal of this study is to use magnetic resonance venography with long-circulating gadolinium-based contrast agent and direct thrombus imaging for quantitative evaluation of DVT volume in a multicenter, clinical trial setting. Inter- and intra-observer variability assessments were conducted, and reproducibility of the protocol was determined.
06:58
Synthesis of an In vivo MRI-detectable Apoptosis Probe
0 Views •
Cited by 3 •
2012
Early detection of apoptosis may identify at-risk cell populations in a variety of diseases. Here we demonstrate a method to link an early apoptosis-detection protein (Annexin V) to a MRI-detectable iron oxide nanoparticle (SPIO). This method may be extended to other proteins of interest to generate MRI-detectable molecular imaging probes.
FAQs
After radiofrequency excitation, transverse magnetization becomes progressively out of phase when the gradient dephases it. Reversing the gradient changes the magnetic-field evolution experienced by the spins, allowing them to rephase at a later time and generate a signal. The resulting echo reflects both the gradient timing and additional magnetic-field variations that contribute to T2* contrast.
Signal in these sequences reflects T2* rather than tissue transverse relaxation alone. T2* combines tissue properties with magnetic-field variations, so local susceptibility-related changes can alter image intensity. This sensitivity helps make gradient-echo imaging useful for detecting clinically relevant findings such as hemorrhage and iron deposition, but the signal represents a combined tissue-and-field effect rather than a purely tissue-specific measurement.
The key distinction is how transverse magnetization is rephased. Gradient echo uses a dephasing gradient followed by gradient reversal, whereas the alternative approach uses a 180-degree refocusing pulse. This difference supports rapid image acquisition and contributes to sensitivity to T2* effects from tissue and magnetic-field variations, giving gradient echo a distinct role in fast and susceptibility-sensitive examinations.
Following radiofrequency excitation, the sequence applies a gradient that dephases transverse magnetization. The gradient is then reversed so the magnetization rephases and produces the echo signal used for image formation. This gradient-based timing is the central sequence workflow and permits rapid acquisition without applying a 180-degree refocusing pulse, which is important for fast clinical imaging.
Rapid acquisition is the main practical advantage supporting these applications. Gradient-echo sequences can acquire three-dimensional datasets and are used in dynamic contrast studies, where time-sensitive imaging is relevant. The same family also supports angiography, allowing imaging strategies to address vascular anatomy and blood flow alongside broader anatomical assessment in medical examinations.
Gradient-echo imaging is particularly relevant when the examination focuses on blood flow, vascular anatomy, hemorrhage, or iron deposition. Angiographic applications emphasize vessels and flow, whereas susceptibility-sensitive examinations can reveal changes associated with hemorrhage or accumulated iron. Selecting this sequence therefore depends on whether the clinical question prioritizes rapid imaging, vascular information, or sensitivity to these findings.