The utilization of two frequency‐shifted sinc pulses for performing volume‐selected <i>in vivo</i> NMR spectroscopy

Doddrell, D. M.; Galloway, Graham J.; Brooks, William M.; Bulsing, J.Mark; Field, James; Irving, MG; Baddeley, H.

doi:10.1002/mrm.1910030620

Cited by 18 publications

(11 citation statements)

References 11 publications

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“…Examples of such application include chemical‐shift selective suppression of water or fat resonances and outer‐volume suppression (OVS) in localized spectroscopy and imaging. In the most common approach, signal suppression is achieved by exploiting one or more frequency‐selective pulses that convert the initial magnetization M 0 into transverse magnetization M xy that is subsequently dephased by pulsed B 0 gradients (1–11). In OVS techniques, M xy is dephased after being excited in slabs at selected locations and orientations.…”

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confidence: 99%

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

Luo

Graaf

DelaBarre

et al. 2001

Magnetic Resonance in Med

106

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A technique is described for performing frequency-selective signal suppression with a high degree of tolerance to RF field inhomogeneity. The method is called B 1 -insensitive train to obliterate signal (BISTRO). BISTRO consists of multiple amplitude-and frequency-modulated (FM) pulses interleaved with spoiler gradients. BISTRO was developed for the purpose of accomplishing bandselective signal removal, as in water suppression and outer-volume suppression (OVS), in applications requiring the use of an inhomogeneous RF transmitter, such as a surface coil. In the present work, Bloch simulations were used to illustrate the principles and theoretical performance of BISTRO. Its performance for OVS was evaluated experimentally using MRI and spectroscopic imaging of phantoms and in vivo animal and human brain. By using FM pulses featuring offset-independent adiabaticity, BISTRO permitted high-quality, broadband suppression with one (or two) discrete borders demarcating the edge ( Key words: adiabatic pulse; pulse sequence; volume localization; outer-volume suppression; frequency modulation A technique to accomplish band-selective signal suppression is a common need in many types of NMR experiments. Examples of such application include chemicalshift selective suppression of water or fat resonances and outer-volume suppression (OVS) in localized spectroscopy and imaging. In the most common approach, signal suppression is achieved by exploiting one or more frequency-selective pulses that convert the initial magnetization M 0 into transverse magnetization M xy that is subsequently dephased by pulsed B 0 gradients (1-11). In OVS techniques, M xy is dephased after being excited in slabs at selected locations and orientations. RF pulses used to excite the unwanted magnetization are commonly the amplitude-modulated (AM) variety. Such OVS approaches generally provide excellent signal suppression, provided the RF field is relatively homogeneous so that each position in the sample experiences a flip angle of 90°. When the flip angle deviates from 90°, some longitudinal magnetization M z remains, giving incomplete signal suppression. The projection presaturation (PP) method of and related techniques (7,8) solve this problem to a certain degree by employing a series of identical, small flip-angle pulses. For example, by repeating the small flip 32 times, the PP technique can offer high-quality suppression (M z / M 0 Ͻ 0.01) on resonance despite an approximately fivefold variation of RF amplitude. Although this degree of compensation for RF inhomogeneity is more than sufficient for experiments performed with volume coils, it is inadequate for RF transmission with a surface coil, which typically subjects the sample to a Ͼ10-fold variation in RF amplitude. Furthermore, because the frequency response profile produced by AM pulses is highly dependent on flip angle, RF transmission with a surface coil can lead to out-of-slice signal excitation, and hence to an undesirable reduction of M 0 in the tissue region(s) to be detected.To overco...

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mentioning

confidence: 99%

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

Luo

Graaf

DelaBarre

et al. 2001

Magnetic Resonance in Med

106

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“…The pulse sequence used for our 1 H MRS study is composed of (1) a chemical shift-selective (CHESS) pulse, which consists of three RF pulses, normally used for water suppression followed by crusher gradients, (2) an outer volume suppression (OVS) that saturates the six slices adjacent to the volume of interest, and (3) localized point-resolved spectroscopy (PRESS) used for obtaining spectra of the selected volume. [19][20][21] Then FID data were acquired (ACQ).…”

Section: Modi®cation Of 1 H Mrs Pulse Sequencementioning

confidence: 99%

Functional analysis of human parotid gland in vivo using the ¹H MRS MT effect

et al. 2002

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Magnetization transfer (MT) was measured in the parotid gland in vivo by (1)H MR spectroscopy in 10 adult volunteers. A comparison was made of stimulated (excess saliva) and resting parotid gland (SPG and RPG, respectively). Following irradiation at an MT pulse of 150 Hz downfield from the water proton signal, signal reductions in SPG and RPG were 83.8 +/- 4.7 and 91.4 +/- 5.7%, respectively. The larger reduction for SPG indicates that an increase in the amount of water in gland cells for the production of more parotid saliva may lead to greater affinity between the protons adjacent to macromolecules and free water which contributes to the MT effect. Activity in the parotid gland correlates with the effect. This method is useful for diagnosing disorders of parotid gland secretion.

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“…In single-voxel MRS (SVS) methods, MR spectra are obtained from a single volume of interest (VOI), while multi-voxel MRS methods yield spectra of multiple adjacent volumes usually covering a larger region than that in SVS. Commonly used SVS techniques include the stimulated echo acquisition mode (STEAM) [3], point resolved spectroscopy (PRESS) [4–6], image selected in vivo spectroscopy (ISIS) [7] and outer volume suppression (OVS) [8, 9]. The multi-voxel MRS methods are imaging-based localization methods and are known as magnetic resonance spectroscopic imaging (MRSI), chemical-shift imaging (CSI) or simply spectroscopic imaging (SI), each referring to the same variety of techniques [10–13].…”

Section: Introductionmentioning

confidence: 99%

Imaging based magnetic resonance spectroscopy (MRS) localization for quantitative neurochemical analysis and cerebral metabolism studies

Lee

Adany

Choi

2017

Analytical Biochemistry

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Accurate quantitative metabolic imaging of the brain presents significant challenges due to the complexity and heterogeneity of its structures and compositions with distinct compartmentations of brain tissue types (e.g., gray and white matter). The brain is compartmentalized into various regions based on their unique functions and locations. In vivo magnetic resonance spectroscopy (MRS) techniques allow non-invasive measurements of neurochemicals in either single voxel or multiple voxels, yet the spatial resolution and detection sensitivity of MRS are significantly lower compared with MRI. A fundamentally different approach, namely spectral localization by imaging (SLIM) provides a new framework that overcomes major limitations of conventional MRS techniques. Conventional MRS allows only rectangular voxel shapes that do not conform the shapes of brain structures or lesions, while SLIM allows compartments with arbitrary shapes. However, the restrictive assumption proposed in the original concept of SLIM, i.e., compartmental homogeneity, led to spectral localization errors, which have limited its broad applications. This review focuses on the recent technical frontiers of image-based MRS localization techniques that overcome the limitations of SLIM through the development and implementation of various new strategies, including incorporation of magnetic field inhomogeneity corrections, the use of multiple receiver coils, and prospective optimization of data acquisition.

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The utilization of two frequency‐shifted sinc pulses for performing volume‐selected in vivo NMR spectroscopy

Cited by 18 publications

References 11 publications

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

Functional analysis of human parotid gland in vivo using the ¹H MRS MT effect

Imaging based magnetic resonance spectroscopy (MRS) localization for quantitative neurochemical analysis and cerebral metabolism studies

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The utilization of two frequency‐shifted sinc pulses for performing volume‐selected in vivo NMR spectroscopy

Cited by 18 publications

References 11 publications

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

BISTRO: An outer‐volume suppression method that tolerates RF field inhomogeneity

Functional analysis of human parotid gland in vivo using the 1H MRS MT effect

Imaging based magnetic resonance spectroscopy (MRS) localization for quantitative neurochemical analysis and cerebral metabolism studies

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Functional analysis of human parotid gland in vivo using the ¹H MRS MT effect