Abstract
Digital acquisition of signals with the aid of an analog-to-digital converter produces sets consisting of N equidistant data points. Each data point represents an interval on the axis of the independent variable of the signal function. We term this variable the “measuring variable.” It can be a time, or a component of the reciprocal positional or velocity spaces.
Keywords
Measuring Domain Exponential Multiplication Digital Resolution Gradient Axis Quadrature Detection
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Notes
- 1.Quadrature detection of the signal and its 90° phase-shifted counterpart permits the distinction of positive and negative frequencies relative to the carrier (or reference) frequency of the system. The complex transverse magnetization is then unambiguously defined in the complex plane. Quadrature detection with respect to phase-encoding domains is possible by recording signals from two series of transients acquired with correspondingly phase shifted RF pulses.Google Scholar
- 2.The FFT procedure [99] common in the numerical analysis of signals requires that the number N of data points in the measuring domain is a power of two. Recall that this can readily be fulfilled by zero-filling the data matrix as usual (see below).Google Scholar
- 3.With 2DFT imaging, apart from the in-plane resolution, the resolution in the third spatial dimension is also of interest as concerns the selection of the slice to be imaged. The factors influencing the slice thickness are discussed in Sects. 25.1 and 36.3 with respect to soft-pulse and spin-lock pulse slice selection, respectively.Google Scholar
- 4.According to Curie’s law this corresponds to about 107 uncompensated proton dipoles aligned along the magnetic field at room temperature.Google Scholar
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© Springer-Verlag Berlin Heidelberg 1997