U.S. Philips Corporation

Jan A Den Hollander

Peter R Luyten

Reurt P Van Stapele

Rudolf M Lamerichs

Johannes J Van Vaals

Johannes H Den Boef

Arend Heerschap

A method for magnetic resonance imaging of a density distribution of a first substance and a second substance in a part of a body which is arranged in a substantially uniform, steady magnetic field, said first substance having a J-coupling. In order to image the contribution to the MR spectrum by said first substance having the J-coupling separately from the contribution to the MR spectrum by the second substance, repetition of refocusing pulses is used for the generating of the spin echo signals, so that in the direction of a first dimension of a data matrix, in which the measured values are arranged, a phase modulation of 180.degree. occurs in the successive values. Furthermore, the method according to the invention utilizes spatial encoding in which the maximum strength of a phase encoding gradient is equal to half the maximum strength of a corresponding phase encoding gradient used in a customary phase code, so that the field of vision is doubled in comparison with the customary field of vision. After Fourier transformation and integration of the MR spectrum, two separate images of the density distribution of the first substance and the second substance are thus obtained. Lactate is an example of a substance having a J-coupling. Fat is an example of a second substance.

Method and device for spectroscopic magnetic resonance imaging

A volume-selective magnetic resonance method for the determination of an MRI spectrum MR image, comprises a 90.degree. excitation pulse (p.sub.0) followed by two 180.degree. pulses (p.sub.1, p.sub.2,) the pulses (p.sub.0, p.sub.1, p.sub.2) being slice-selective. The magnetic resonance signal (SE) is sampled in the absence of magnetic field gradients and a spectrum is determined by way of Fourier transformation. In comparatively simple spin systems, J-refocusing is achieved for a specific choice of the echo time (TE), while only one J-coupling of more complex spin systems, comprising more than on J-coupling, is refocused by a specific choice of the echo time (TE). The method in accordance with the invention applies either a chemically selective 180.degree. pulse (p.sub.3) or a broadband 90.degree. pulse (p.sub.4) between the 180.degree. pulses (p.sub.1, p.sub.2). This causes J-refocusing to then occur, regardless the selected echo time (TE).

Volume-selective magnetic resonance imaging method and device

An object is placed within the field of magnetic coils which generate a steady uniform magnetic field. The object contains nuclear spins of coupled first and second types of nucleus, for example, CH.sub.n in which C is a .sup.13 C carbon isotope and H is a .sup.1 H proton. Magnetic resonance signals are generated in the object by RF pulses. Pulse and gradient sequences are generated for providing magnetization transfer from the first nucleus to the second nucleus via first and second channels. A display displays spectra formed from resonance signals processed by a programmed processor via Fourier tranformation of sampled values. A pick up coil is tuned to receive the signals from a corresponding nucleus which is processed by a corresponding channel. The process is volume selective combined with a Hartmann-Hahn transfer sequence.

Method and device for the volume-selective extraction of a magnetic

Polarization transfer pulse sequences in NMR, such as a DEPT pulse sequence, in combination with a volume selection (for example, VSE) in a body have been described. Therein first volume selection is performed in the body by means of VSE, after which the body is exposed to the DEPT pulse sequence. According to the present invention it is proposed to make the volume selection coincide with the polarization transfer pulse sequence, so that inter alia the pulse sequence is less susceptible to imperfections of rf electromagnetic pulses.

Method of and device for the volume-selective determination of an MR

The measurement of localized spectra by means of stimulated echoes is known per se. Using three 90.degree. pulses, stimulated echoes are then generated; these pulses are selective or not. However, this technique it is not suitable for measuring good proton spectra of metabolites because the response of the non-bound protons is much greater than the response of the bound protons. In accordance with the invention, a fourth (spatially selective) 180.degree. refocusing pulse is added to a pulse sequence consisting of a 90.degree. non-spatially selective but frequency-selective pulse and two subsequent 90.degree. spatially selective pulses. Thus, a refocused stimulated echo is generated in which the response of the non-bound protons is suppressed and which contains only signals from the chemically bound protons. The proposed methods are particularly suitable for measurements on lactate because of the excellent spectral editing properties.

Volume-selective spectroscopy using refocused echoes

Using the method in accordance with the invention a layer of an object is selected by means of a cycle comprising a non-selective 90.degree. pulse, a dephasing gradient magnetic field, a non-selective 180.degree. pulse and a selective 90.degree. pulse in the presence of a similar gradient field. In the layer, a magnetization in the z-direction is obtained. Outside the object layer the transverse magnetization is totally dephased. By executing the cycle three times, during which the gradient directions of the three gradient fields used are mutually orthogonal, a 'cube-like' volume is selected. High-resolution images of spin density distributions and T1 or T2 distributions can thus be realized and location-dependent spectroscopy is also possible.

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Eindhoven, Netherlands

Jan A Den Hollander