High field MRI

Based on ultra-high Field (Ultra High Field, UHF) magnetic resonance (NMR) application directly benefited from its High sensitivity.Such as: higher signal-to-noise ratio, helps to obtain higher resolution and/or use the shorter scan, or to make nuclear imaging.

In order to avoid the partial volume effect, to improve the quality and improve the data analysis, data often require the highest resolution.If it is the object of study, however, each individual element of the signal is not strong, so the resulting low SNR can interfere with the analysis of the image.Ultra-high field (UHF) instrument can acquire larger signal-to-noise ratio, thus can be directly converted into higher resolution.This allows researchers to the resolution to the direction of the "living MRI histology", and helps to improve the data quality in a series of disease model [1, 2].

In addition to the anatomical imaging, many magnetic resonance imaging (fmri) method also thanks to the improvement of sensitivity.For example, in a BOLD fMRI, can define the more accurate way of stimulation, which increase signal-to-noise ratio makes the requirement to the stimulus intensity decreased.In addition, with the improvement of resolution, fMRI less receptor element limiting the size of precision, but is restricted to reach the neurons active point of blood flow was particularly accurate (in space and time) to adjust the degree of how [3].In addition, for high resolution fMRI, partial volume effect of reducing is expected to further improve the signal-to-noise ratio [4].A high-resolution fMRI with small voxel size will benefit from additional ultra-high field, because it work under thermal noise dominant status, therefore, in this case, compared in terms of low magnetic field ultra-high field can significantly improve the sensitivity of [4].

Because of limited time available magnetic resonance imaging system, need a lot of animals, or model is not stable, often need shorter time measurement.

When using low field strength, usually require a longer time to get enough SNR measurement.Using ultra-high field can significantly shorten the measurement time, the reason is that, for example, triple sensitivity can be obtained in a quarter of the time resolution is the same, the quality of similar images [5].Therefore, can reduce the number of average data, the time saved can into other topics or further study.

Ultra-high field to obtain high signal-to-noise ratio of another benefit is that four times gyromagnetic ratio, low torque and low abundance of miscellaneous nuclear imaging can be improved significantly, even for the first time realized,6,7,8 [5].

This created a number of different research and application, such as sodium (squared after Na) imaging, etc.Sodium magnetic resonance imaging (fmri) are widely used at present.In clinical systems, for example, sodium concentration measurement is used to research organization vigor [9].Due to high sensitivity, using ultra-high field very help sodium imaging [7].In addition, the high field mri can potentially achieve the breakthrough of oxygen (17 o) imaging, imaging support direct cell oxygen metabolism.Cell oxygen metabolism in alzheimer's disease and Parkinson's disease, and diseases such as cancer has changed.Therefore, 17 o magnetic resonance imaging (fmri) has showed the potential of local pathological changes in brain, it also illustrates the importance of this imaging method [8].

Metabolism of mixed imaging is another application of deuterium nuclear imaging, can be used to map glucose metabolism.In addition to being able to map figure rather than glucose uptake glucose metabolism, metabolic imaging deuterium (DMI) than positron emission tomography (PET) has additional advantages, the use of radioactive matrix [11].Deuterium under ultra-high frequency sensitivity increases, make DMI PET viable alternatives.

Greatly benefit from the high field (UHF) is the application of magnetic resonance imaging blood oxygen level dependent (BOLD) fMRI.In ultrahigh off the increase of the magnetic sensitivity into more observable BOLD signal change, thus improves the fMRI experiment [1].

Functional magnetic resonance imaging (fmri) used to study the function of connection, in order to further understand the brain function in health and disease [2].Using ultra-high field provides high sensitivity, high resolution fMRI before the clinical experiment and feasible [3].In addition, under the condition of the thermal noise dominates, function will also benefit from the high field sensitivity, because it directly depends on the sensitivity and noise [4] indirectly dependent on time.This is a study on high resolution in ultra high off the situation [5].

In addition to the BOLD Imaging, other dependent on high magnetic sensitivity and high signal-to-noise ratio also benefit from the high field magnetic resonance (NMR) application, such as magnetic sensitive Weighted Imaging (Susceptibility Weighted Imaging, SWI) and Quantitative magnetic sensitive Imaging (policy Susceptibility Mapping, QSM) [6].QSM of stroke model can be used for live animals microvascular study [7].

Because it has higher sensitivity and frequency dispersion, which makes high field technology is naturally used in magnetic resonance spectrum.Currently on the market already can buy field strength is as high as 23.5 tesla MRS instruments, can high resolution spectrum analysis was carried out on the small sample experiment [1].

Similarly, the high field MRI magnet is advantageous to the living specimen increase chemical shift and increase sensitivity.As a result, the existing clinical report before using high field magnets can significantly improve the quality of living spectrum, 5-tetrafluorobenzoic [2].It is important to note that due to the magnetic field intensity is high, some metabolites can be detected for the first time in the body [4].

Besides the advantage of increased and chemical shift sensitivity and studies further show that the relaxation MRS strategy could be additional use of ultra-high water and metabolites of relaxation time differences "anhydrous" MRS, without the need for a common pressure water technology [3].

In addition to the magnetic resonance spectrum, enhanced spectrum dispersion also is good for magnetization transfer technology, such as: chemical exchange saturation transfer (CEST) imaging, so as to realize high selectivity [6].Ultra-high field including chemical exchange other advantages can achieve higher saturation [6] and relative to the chemical shift of a lower exchange rate [7].

Chung et al., recently published a paper show that, compared with 9.4 tesla 15.2 tesla histamine in the rat brain chemical exchange effect of proton signals increased significantly.Increased by 65% compared with 9.4 tesla, emphasize the importance of a strong field of chemical exchange application [7, 8].

A prominent benefit Yu Chaoqiang field application is GluCEST CEST, GluCEST can monitoring the local metabolic defects of neurodegenerative diseases [6, 9].Technology research, for example, in the past by ultra-high field gene typing in model mice, found GluCEST is a potential biomarkers in the body of huntington's disease [9].

In addition, there are signs that the Gluco CEST metabolism associated with neuron activity can be used in the survey.Using the rat model of electrical stimulation on its front PAWS in under 17.2 tesla Gluco CEST during stimulation shows negative contrast, and BOLD imaging provides a contrast, thus proving CEST fMRI can time change of local monitoring glucose levels.

For clinical systems, recent research suggests that to receive only array coil, signal-to-noise ratio (SNR) with the increase of magnetic field intensity enhancement is superlinear [1].These results highlight when using high field (UHF) system for impressive SNR gain.

In addition to the SNR gain itself, receiving array coil provides the possibility of accelerating further, which has the potential to increase the space and time resolution.For arrays of preclinical ultra-high field imaging, coil can be used in the brain, heart, spine, and the body, and has set up a routine use.

Before clinical magnetic resonance imaging, MRI cryogenic cryogenic cooling type probe [2] can improve sensitivity extra [3], and has been widely used.Combined with a high field MRI, additional gain significant, can be realized in a reasonable measurement time of the highest quality images [4].Can be equipped with magnetic resonance imaging (MRI), for example, ultra-low temperature probe of preclinical 15.2 tesla system to obtain high resolution in vivo mouse data easily.