including the proton density, machine-dependent gain factor and the echo term. Optimisation of flip angles when imaging samples with a large R1 range of values has been far from trivial and little work has been published on this subject [1, 2]. During the optimisation, it is important that the actual distribution of R1 values in the image sample is taken into account. We propose a novel flip an...

This paper presents a consistent theory for describing indeterminacy and uncertainty of 3-D reconstruction from a sequence of images. First, we present a group-theoretical analysis of gauge transformations and gauges by invoking the Lie group theory. We then discuss how to evaluate the reliability of the solution that has indeterminacy. We also extend the Cramer-Rao lower bound to problems with...

This paper considers a method for estimating time delays, amplitudes, and Doppler scales of a multipath signal. The method is an extension of work previously reported by Manickam and Vaccaro [1] which dealt solely with time delays and amplitudes, and extended by Habboosh and Vaccaro [2] to include Doppler scale. In this paper, an algorithm is presented for determining the size of the indicator ...

This paper considers the problem of estimating the parameters of two-dimensional moving average random elds. We rst address the problem of expressing the covariance matrix of a moving average random eld, in terms of the model parameters. Assuming the random eld is Gaussian, we derive a closed form expression for the Cramer-Rao lower bound on the error variance in jointly estimating the model pa...

We address precision of estimation of the degree of polarization (DOP) from the orthogonal state contrast image (OSCI) in the presence of both signal-dependent Poisson noise due to useful signal, and additive Poisson noise due to dark current and / or background light. We determine the Cramer Rao Lower Bound and deduce from it figures of merit for DOP estimation. In particular, we show that the...

Within the general framework of active imaging we address the degree of polarization (DOP) estimation in the presence of additive Gaussian detector noise. We first study the performance of standard DOP estimators and propose a method to increase estimation precision using physically relevant a priori information. We then consider the realistic case of nonuniform illumination distribution. We de...

INTRODUCTION Magnitude fitting has been proposed as an alternative to complex data fitting for quantitative chemical shift-encoded water/fat imaging. Advantages of magnitude fitting include the removal of sensitivity to phase errors in the signal (e.g., caused by eddy currents) [1] and suppression of B0 field inhomogeneity effects (i.e., removal of one nonlinear parameter from the signal model)...

A closed-form expanded autocorrelation method for real single-tone frequency estimation is proposed. Firstly, the modified covariance (MC) method based on multiple autocorrelation lags is applied to provide a coarse frequency estimate. Then, a closedform adjustment term based on a least square cost function is derived to get the fine frequency estimate. Simulation results show that the performa...

In radio telescope arrays, the complex receiver gains and sensor noise powers are initially unknown and have to be calibrated. Gain calibration enhances the quality of astronomical sky images and moreover, improve the effectiveness of certain radio telescope phased-array data processing techniques, such as radio interference (RFI) mitigation and beamforming. In this paper we present several clo...

Localization of a moving target in a dual-frequency radars system has now gained considerable attention. The noncoherent localization approach based on a least squares (LS) estimator has been addressed in the literature. Compared with the LS method, a novel localization method based on a two-step weighted least squares estimator is proposed to increase positioning accuracy for a multi-station d...