In-phase (IP) and out-of-phase (OOP) sequences correspond to paired MRI gradient echo (GRE) sequences obtained with the same repetition time (TR) but with two different echo time (TE) values.

What are the different MRI sequences?

The most common MRI sequences are T1-weighted and T2-weighted scans. T1-weighted images are produced by using short TE and TR times. The contrast and brightness of the image are predominately determined by T1 properties of tissue. Conversely, T2-weighted images are produced by using longer TE and TR times.

What is gradient echo sequence in MRI?

A gradient echo sequence is the base of many important derived sequences such as echo-planar imaging and SSFP stationary sequences. It allows to obtain very short repetition times (TR), and therefore to acquire images in a short time.

What is signal dropout MRI?

When the susceptibility gradient adds to one of the scanner's gradients in a way that the resulting gradient experienced by the water molecules in a particular region is not what we intended, then signal drop-out can result.

What is chemical shift MRI?

Chemical shift imaging is an MRI technique that is used to determine whether lipid and water protons are present with the same small voxel (three-dimensional pixel) of space.

MRI in-phase, out-of-phase and the DIXON method

23 related questions found

What is the chemical shift at 1.5 T?

With a 1.5 T field strength, the frequency shift is 225 Hz, corresponding to a period of 4.4 ms. Therefore, at 1.5 T, protons of fat and water will be in phase every 4.4 ms : their signals are additive.

What is magic angle artifact?

The magic angle artifact refers to the increased signal observed when MRI sequences with short echo time (TE) (e.g., T₁ or proton density spin-echo sequences) are used to image tissues with well-ordered collagen fibers in one direction (e.g., tendon or articular hyaline cartilage).

What is in and out of phase?

In-phase (IP) and out-of-phase (OOP) sequences correspond to paired MRI gradient echo (GRE) sequences obtained with the same repetition time (TR) but with two different echo time (TE) values.

What is signal drop out?

A dropout is a momentary loss of signal in a communications system, usually caused by noise, propagation anomalies, or system malfunctions. For analog signals, a dropout is frequently gradual and partial, depending on the cause.

What is the EPI factor?

The number of k-space lines (echoes) collected in a single shot is called the "Echo Train Length (ETL)" by GE and Canon; the "EPI factor" by SIemens and Philips; and the "shot factor" by Hitachi. The regions of k-space divided up by each shot of a multi-shot sequence are called segments.

What is flair in brain MRI?

Fluid-attenuated inversion recovery (FLAIR) is an MRI technique that shows areas of tissue T2 prolongation as bright while suppressing (darkening) cerebrospinal fluid (CSF) signal, thus clearly revealing lesions in proximity to CSF, such as cerebral cortical lesions.

Is gradient echo T1 or T2?

For the basic GRE sequence FLASH, the larger flip angles give more T1 weighting to the image and the smaller flip angles give more T2, or actually T2* weighting, to the images.

What is gradient sequence?

Gradient echo sequences (GRE) are an alternative technique to spin-echo sequences, differing from it in two principal points: utilization of gradient fields to generate transverse magnetization. flip angles of less than 90°

What is T1 and T2?

T1 and T2 are technical terms applied to different MRI methods used to generate magnetic resonance images. Specifically, T1 and T2 refers to the time taken between magnetic pulses and the image is taken. These different methods are used to detect different structures or chemicals in the central nervous system.

Is Flair T1 or T2?

FLAIR MRI is a heavily T2-weighted technique that dampens ventricular CSF signal. This causes the highest signals on the sequence are from certain brain parenchymal abnormalities, such as MS lesions, while the CSF appears black.

What are pulse sequences in MRI?

An MRI pulse sequence is a programmed set of changing magnetic gradients. Each sequence will have a number of parameters, and multiple sequences grouped together into an MRI protocol.

What do you mean by out of phase?

If two things are out of phase with each other, they are not working or happening together as they should. If two things are in phase, they are working or occurring together as they should. The Skills Programme is out of phase with the rest of the curriculum. [ + with]

What does out of phase mean physics?

If one of the two sound waves of the same frequency is shifted by one-half cycle relative to the other, so that one wave is at its maximum amplitude while the other is at its minimum amplitude, the sound waves are said to be “out of phase.” Two waves that are out of phase exactly cancel each other when added together.

What does out of phase look like?

Since phase cancellation is most apparent in low frequency sounds, the audible result of out of phase monitors is typically a thin-sounding signal with little or no bass sound. Another possible result is that the kick drum or bass guitar will move around the mix, rather than coming from a single spot.

What is zipper artifact?

In MR imaging, zipper artifact refers to a type of MRI artefact where one or more spurious bands of electronic noise extend perpendicular to the frequency encode direction and is present in all images of a series. There are various causes for zipper artifacts in images.

What is Samsung magic angle?

Magic angle is a feature in Samsung monitors where the viewing angle for the user is taken are of by adjusting the settings of image in such a way that the viewing angle for any perspective is optimum.

What is cross talk in MRI?

Cross-talk refers to interference between adjacent slices in MR imaging. Cross-talk arises because the slice profiles generated by RF- pulses are not perfectly rectangular. The simplest solution is to introduce small gaps on the order of 10-20% between slices so that the "tails" of the slice profiles do not overlap.

What is the chemical shift between fat and water at 3 T?

Spectral peaks for fat and water over a large anatomic area broadened due to inhomogeneity effects. The average chemical shift difference is about 3.5 ppm. At 3.0T where the Larmor frequency is 128 MHz, the fat-water frequency shift would be twice as large, or about 440 Hz.

What is entry slice phenomenon?

Entry slice phenomenon occurs when unsaturated spins in blood first enter into a slice or slices. It is characterized by the bright signal in a blood vessel (artery or vein) at the first slice that the vessel enters. Usually, the signal is seen on more than one slice, fading with distance.

What are chemical shifts in NMR?

In nuclear magnetic resonance (NMR) spectroscopy, the chemical shift is the resonant frequency of a nucleus relative to a standard in a magnetic field. Often the position and number of chemical shifts are diagnostic of the structure of a molecule. ... This is reflected in the spin energy levels (and resonance frequencies).