INTRODUCTION Accurate T1 relaxation time parameter estimation is essential for a wide variety of quantitative MR applications; for example, obtaining accurate T1 values can be crucial in problems such as quantitative contrast enhanced imaging studies, image segmentation and tissue characterization, and absolute metabolite quantification in NMR spectroscopy. Typical experiments designed specific...

We give a detailed study of the semiconvergence behavior of projected nonstationary simultaneous iterative reconstruction technique (SIRT) algorithms, including the projected Landweber algorithm. We also consider the use of a relaxation parameter strategy, proposed recently for the standard algorithms, for controlling the semiconvergence of the projected algorithms. We demonstrate the semiconve...

Background A novel strain relaxation index (SRI) is introduced to assess diastolic function by CMR, using myocardial deformation during LV relaxation. We investigate how SRI relates to standard diastolic parameters by echocardiography (echo). We also relate SRI to mass to volume ratio (MVR) by CMR, which is seen to increase in diastolic dysfunction. SRI accounts for both very early myocardial r...

S U M M A R Y The material properties of earth materials often change after the material has been perturbed (slow dynamics). For example, the seismic velocity of subsurface materials changes after earthquakes, and granular materials compact after being shaken. Such relaxation processes are associated by observables that change logarithmically with time. Since the logarithm diverges for short an...

M. A. Katsoulakis, G. Kossioris and Ch. Makridakis Abstract. We study discrete and semidiscrete relaxation schemes for multidimensional scalar conservation laws. We show convergence of the relaxation schemes to the entropy solution of the conservation law and derive error estimates that exhibit the precise interaction between the relaxation time and the space/time discretization parameters of t...

Cerebral ischemia alters the molecular dynamics and content of water in brain tissue, which is reflected in NMR relaxation, diffusion and magnetization transfer (MT) parameters. In this study, the behavior of two new MRI contrasts, Relaxation Along a Fictitious Field (RAFF) and Z-spectroscopy using Alternating-Phase Irradiation (ZAPI), were quantified together with conventional relaxation param...

Background Characterization of infarcted myocardial tissue by current cardiovascular magnetic resonance (CMR) methods is predominantly carried out after i.v. application of Gadolinium (Gd)-based contrast agents (CA). However, recent advances in CMR enable the acquisition of parametric maps making use of endogenous tissue properties for diagnostic purposes, which may supersede the need for injec...

The problem of redistribution of translational and rotational energy has been solved for diatomic gases within the framework of the Chapman-Enskog method and the Parker model in the general case of the arbitrary energy exchange ratio. The nonequilibrium gasdynamic equations, transport coefficients and relaxation time have been found for rotational-translational processes in a diatomic gas. The ...