Nuclear magnetic resonance whole-body imager operating at 3.5 KGauss.

Inversion recovery has the potential to be a powerful method of determining the values of T1 in in vivo studies. However, because of its relative slowness it is not practical to undertake several experiments with different values of the interval between the magnetization inverting 180 degree pulse and the interrogating 90 degree one. The multiple inversion recovery method described here uses a series of sampling pulses, most much less than 90 degrees, to produce a series of images. It is shown that slice shape is relatively reproducible from one sample to another and that, largely as a result, the accuracy of the sequence in measuring T1 is encouraging.

Section: Discussionmentioning

confidence: 99%

The design of a multiple inversion recovery sequence for T1 measurement

Young¹,

Hall

1987

“…Flow direction ( 3 , 4 ) and timing information ( 5 ) have been transferred into composite images using color scales. Others have used color to represent intensities in a single image (6,7).…”

Section: Introductionmentioning

confidence: 99%

Unified multiple‐feature color display for MR images

Kamman¹,

Stomp²,

Berendsen³

1989

A display method is proposed in which the spin-lattice relaxation time T1, the spin-spin relaxation time T2, and the proton density rho of each pixel in a MR image are simultaneously expressed in color features in a unified way that allows international standardization. MR images were made from a phantom, a healthy volunteer, and patients in such a way that T1 and T2 and proton density images could be derived. T1 and T2 data were compared with accurate relaxation time measurements of the phantom content. Color images were computed from the acquired T1 and T2 images using matrix multiplication on a pixel base. In this way the color combination in each pixel represents the properties of that particular pixel by a unique mixing of the elementary colors red, green, and blue. Color resolution could be modified using different choices of the reference triangle in which the color combinations were defined. This method of representation offers a means for displaying multiple features as T1 and T2 in one directly interpretable image, independent of instrumental settings.

“…Spin-echo behavior, with or without a selective a (18)(19)(20), is complex and very dependent on the quality of the experiment, particularly the rf pulses. Figure 8 illustrates the theoretical predictions with a selective a of signals for gray and white matter at various repetition rates, while with a nonselective a the signal in SE (unlike PS) is predicted by the better model to be less than that by the simple, with the slice becoming more triangular at faster repetition rates.…”

mentioning

confidence: 99%

Variations in slice shape and absorption as artifacts in the determination of tissue parameters in NMR imaging

Young¹,

Bryant²,

Payne³

1985

Existing models for the contrast between one tissue and another in NMR imaging have shown that there are regions of ambiguity particularly in spin-echo sequences. This paper indicates that there are further problems due to variations in slice formation with tissue parameters, and that it is necessary to be very conservative in assessing the magnitude of T1 in any imaging system. The change in shape affects the appearance of images due, in essence, to adjustments in partial volume effects, with some of the contributions to the signal from lesions with long T1 coming from different regions to those for normal tissue. A simple model for a slice is used because the actual form in a real imaging situation is the result of a number of factors which are usually not accurately enough known.