Theoretical model of the single spin-echo relaxation time for spherical magnetic perturbers

2014 ◽  
Vol 71 (5) ◽  
pp. 1888-1895 ◽  
Author(s):  
Felix T. Kurz ◽  
Thomas Kampf ◽  
Sabine Heiland ◽  
Martin Bendszus ◽  
Heinz-Peter Schlemmer ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Theoretical Model ◽  
Spin Echo ◽  
Single Spin

Method Dependence of Proton Spin-Lattice Relaxation Analysis in Biologic Tissues

1989 ◽  
Vol 30 (1) ◽  
pp. 97-100 ◽  
Author(s):  
M. Komu ◽  
A. Alanen ◽  
H. Määttänen ◽  
M. Kormano
Keyword(s):  
Relaxation Time ◽  
Spin Echo ◽  
Weighted Average ◽  
Proton Spin ◽  
Point Method ◽  
Spin Lattice Relaxation ◽  
Proton Relaxation ◽  
Spin Lattice ◽  
Exponential Relaxation ◽  
Data Point

Spin-lattice proton relaxation times (T1) in several biologic and phantom samples have been measured and analysed by using standard inversion recovery (IR) and spin echo (SE) sequences at 0.02 T. The average T1 of the sample was measured with the two-data point method. In the case of bi-exponential relaxation the value of a single T1 is strongly dependent on the T1 and TR selected. With short TI the T1 value obtained by using the two point method is approximately equal to the weighted average of the two relaxation time components (T1s and T1l), while at long inversion times TI the single T1 is more dependent on the long component T1l. The more the true short and long relaxation time components T1s and T1l of the bi-exponential relaxation differ from each other, the greater is the potential error, provided that the weights ws and wl do not differ very much. When two-data point analyzing method is used, the possible multi-exponential behaviour of the relaxation in tissues will be missed. For more reliable T1 values a series of images with as many values of TI as possible should be taken. Knowledge of true multi-exponential relaxation parameters helps in optimizing the sequence parameters and the image contrast between the various tissues.

BEHAVIOR IN ELECTRIC FIELDS OF SIMPLE BIOLOGICAL MEMBRANES

2001 ◽  
Vol 15 (09n10) ◽  
pp. 299-308
Author(s):  
MARIA HONCIUC ◽  
ELENA SLAVNICU
Keyword(s):  
Fatty Acids ◽  
Relaxation Time ◽  
Fatty Acid ◽  
Liquid Crystals ◽  
Theoretical Model ◽  
Electric Fields ◽  
Biological Membranes ◽  
Biological Processes ◽  
Electric Permittivity ◽  
Order Of Magnitude

The latest studies in biophysics and biochemistry have revealed the major role that liquid crystals (LC) and related phenomena play in biological processes. To account for a number of membrane mechanisms in view of the theoretical model developed by S. J. Singer, studies were carried out on mixtures of fatty acids (arachidic, lauric, butyric) and cholesterol in different weight percentages. Such mixtures may help one understand some mechanisms on which the operation of biological membranes relies. To this end, the way these mixtures behave in an electric field was studied. Electric measurements were conducted from which the average time of electric relaxation (τ) and average electric permittivity (ε r ) were determined. Depending on cholesterol percentage, changes by more than one order of magnitude were found to occur in the electric relaxation time. The ratio between the various fatty acid components did not influence the average time τ in any significant manner. By contrast, the relative electric permittivity ε r was seen to decrease by at least one order of magnitude with raising the cholesterol percentage. The electric properties of such systems essentially depend on changing the amount of cholesterol in the system.

scholarly journals Inter-plane Coupling and Spin Gap -an NMR/NQR Look on Typical Properties of High-Temperature Superconductors

1996 ◽  
Vol 51 (5-6) ◽  
pp. 786-792
Author(s):  
D. Brinkmann
Keyword(s):  
Relaxation Time ◽  
Spin Echo ◽  
High Temperature Superconductors ◽  
Double Resonance ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Nmr Studies ◽  
Spin Gap ◽  
Spin Lattice

Abstract The paper discusses some NQR/NMR studies performed on Y-Ba-Cu-O superconductors at the University of Zürich. In particular, we review studies performed in Y2Ba4Cu7O15 by measuring various planar Cu NQR/NMR parameters: the spin-lattice relaxation time, the Knight shift and the indirect component of the Gaussian contribution to the spin-spin relaxation time. The temperature dependence of these parameters reveals a coupling between adjacent planes of a double plane. The existence of the inter-plane coupling has independently been confirmed by performing NQR Spin-Echo Double Resonance (SEDOR) experiments. The appearance of a spin gap seems to be the consequence of inter-plane coupling.

What is the most suitable MR signal index for quantitative evaluation of placental function using Half-Fourier acquisition single-shot turbo spin-echo compared with T2-relaxation time?

2017 ◽  
Vol 59 (6) ◽  
pp. 748-754 ◽  
Author(s):  
Kyoko Nakao Kameyama ◽  
Aki Kido ◽  
Yuki Himoto ◽  
Yusaku Moribata ◽  
Sachiko Minamiguchi ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Spin Echo ◽  
Psoas Muscle ◽  
Single Shot ◽  
T2 Relaxation Time ◽  
Turbo Spin Echo ◽  
T2 Relaxation ◽  
Placental Function ◽  
Turbo Spin ◽  
Psoas Major

Background Half-Fourier acquisition single-shot turbo spin-echo (HASTE) imaging is now widely used for placental and fetal imaging because of its rapidity and low sensitivity to fetal movement. If placental dysfunction is also predicted by quantitative value obtained from HASTE image, then it might be beneficial for evaluating placental wellbeing. Purpose To ascertain the most suitable magnetic resonance (MR) signal indexes reflecting placental function using HASTE imaging. Material and Methods This retrospective study included 37 consequent patients who had given informed consent to MR imaging (MRI) examinations. All had undergone MRI examinations between February 2014 and June 2015. First, the correlation between T2-relaxation time of normal placenta and gestational age (GA) was examined. Second, correlation between signal intensity ratios (SIRs) using HASTE imaging and placental T2-relaxation time were assessed. The SIRs were calculated using placental signal intensity (SI) relative to the SI of the amniotic fluid, fetal ocular globes, gastric fluid, bladder, maternal psoas major muscles, and abdominal subcutaneous adipose tissue. Results Among the 37 patients, the correlation between T2-relaxation time of the 25 normal placentas and GA showed a moderately strong correlation (Spearman rho = –0.447, P = 0.0250). The most significant correlation with placental T2-relaxation time was observed with the placental SIR relative to the maternal psoas major muscles (SIRpl./psoas muscle) (Spearman rho = −0.531, P = 0.0007). Conclusion This study revealed that SIRpl./psoas muscle showed the best correlation to placental T2-relaxation time. Results show that SIRpl./psoas muscle might be optimal as a clinically available quantitative index of placental function.

Effects of Aging on Polymerization Kinetics

1990 ◽  
Vol 215 ◽  
Author(s):  
Christopher N. Bowman ◽  
Nikolaos A. Peppas
Keyword(s):  
Relaxation Time ◽  
Theoretical Model ◽  
Light Intensity ◽  
Physical Aging ◽  
Volume Relaxation ◽  
Radical Concentration ◽  
Model Predictions ◽  
Maximum Conversion ◽  
Effects Of Aging ◽  
Crosslinking Reactions

AbstractA theoretical model was developed to describe the physical aging during photopolymerizations and crosslinking reactions of diacrylates and dimethacrylates. The model incorporates the strong coupling between the volume relaxation and the kinetics observed in these reactions. Model predictions are presented for the reaction kinetics, volume relaxation, radical concentration and maximum conversion as a function of light intensity and relaxation time of the polymer.

scholarly journals Single spin-echo T 2 relaxation times of cerebral metabolites at 14.1 T in the in vivo rat brain

2013 ◽  
Vol 26 (6) ◽  
pp. 549-554 ◽  
Author(s):  
Lijing Xin ◽  
Giulio Gambarota ◽  
Cristina Cudalbu ◽  
Vladimír Mlynárik ◽  
Rolf Gruetter
Keyword(s):  
Rat Brain ◽  
Spin Echo ◽  
Relaxation Times ◽  
Single Spin ◽  
Cerebral Metabolites
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