PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 3362070

Multifrequency selective rf pulses for multislice MR imaging.

S Müller
View original source ↗Export metadata ↓

Abstract

A method is described for multislice imaging by means of rf pulses which contain a multifrequency excitation spectrum. These pulses label each slice by an individual signal phase and allow the separation of the signals from all the slices by subsequent add/subtract procedures. The image sensitivity corresponds to the total number of acquisitions. Sequences for the imaging of an arbitrary number of slices with a minimum number of experiments are described.

Explore related subjects

Magnetic Resonance ImagingModels, StructuralJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S Müller. 1988. Multifrequency selective rf pulses for multislice MR imaging.. https://doi.org/10.1002/mrm.1910060315

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2026

Ultra-high-field 7T MRI reveals neural abnormalities of attention networks in relation to cognitive impairment in hypertension.

Hypertension is a significant risk factor for cognitive impairment (CI), yet the corresponding neural network abnormalities remain underexplored. In this study, we examined the associations among global and domain-specific cognitive dysfunction, neuroimaging measures, and blood pressure in a subgroup of hypertensive patients with CI (N = 41) from a randomized controlled trial who underwent ultra-high-field 7 T MRI. Structural atrophy related to CI was localized to regions overlapping the attention networks. Both whole-brain and within-network dysfunction of the attention networks were associated with worse global cognitive performance. Notably, hyperconnectivity within key attention network hubs, including the right anterior insula and posterior intraparietal sulcus, was associated with declined processing speed in hypertensive patients, mediating the association between pulse pressure and processing speed. These findings provide new insights into the neural pathophysiology of hypertension-related CI and suggest potential network-based targets for intervention.

Magnetic Resonance Imaging↗
PubMed2002

Liquid-state NMR and scalar couplings in microtesla magnetic fields.

We obtained nuclear magnetic resonance (NMR) spectra of liquids in fields of a few microtesla, using prepolarization in fields of a few millitesla and detection with a dc superconducting quantum interference device (SQUID). Because the sensitivity of the SQUID is frequency independent, we enhanced both signal-to-noise ratio and spectral resolution by detecting the NMR signal in extremely low magnetic fields, where the NMR lines become very narrow even for grossly inhomogeneous measurement fields. In the absence of chemical shifts, proton-phosphorous scalar (J) couplings have been detected, indicating the presence of specific covalent bonds. This observation opens the possibility for "pure J spectroscopy" as a diagnostic tool for the detection of molecules in low magnetic fields.

Magnetic Resonance Imaging↗
PubMed2002

MRI volume measurements of hypointense objects. A phantom study using stereological methods.

Volume estimates made from thick slabs overestimate the volume of a positive contrast particle in a translucent matrix and underestimate its volume if the particle has negative contrast and the matrix is opaque. For T2-weighted MRI high signal objects the bias can be corrected according to simple geometric models. For negative contrast or hypointense objects the magnitude of the bias is unknown and no corrections have yet been put forward. We wanted to determine the bias of MRI measurements of hypointense objects of known diameter surrounded by a positive contrast solution. One, 3 and 5 mm slices with three different contrast concentrations were obtained according to a stereological MRI protocol. Results were compared with the true object size to estimate the bias. A simple correction for the bias could not be developed due to interslice cross-talk. Cross-talk makes an object appear in more MRI slices than corresponding to its physical size and larger than the true diameter. For phantom measurements an empirical correction could be developed, but for measurements of non-ideal objects such as brain structures the validity of the correction would be unpredictable. Besides avoiding or reducing cross-talk, the best way to deal with this bias is to measure the object's maximal contrast from edge to edge, a solution which is not perfect.

Magnetic Resonance Imaging↗