scholarly journals Preliminary magnetic resonance relaxometric analysis of Fricke gel dosimeters produced with polyvinyl alcohol and glutaraldehyde

2017 ◽  
Vol 32 (3) ◽  
pp. 242-249 ◽  
Author(s):  
Salvatore Gallo ◽  
Giorgio Collura ◽  
Giuseppina Iacoviello ◽  
Anna Longo ◽  
Luigi Tranchina ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Polyvinyl Alcohol ◽  
Dose Range ◽  
Relaxation Times ◽  
Ion Concentration ◽  
Nuclear Magnetic Resonance Relaxometry ◽  
New Formulation ◽  
Nuclear Magnetic

This work describes the preliminary analysis of Fricke gels dosimeters characterized by a new formulation making use of a matrix of polyvinyl alcohol cross-linked by adding glutaraldehyde and analyzed by means of nuclear magnetic resonance relaxometry. In previous optical studies, these gels have shown promising dosimetric features in terms of photon sensitivity and low diffusion of ferric ions produced after irradiation. In this work, we used a portable nuclear magnetic resonance relaxometer to measure the relaxation times (which are important for dosimetric applications) of these gel materials. For this purpose, we performed a study for optimizing the acquisition parameters with a nuclear magnetic resonance relaxometer. Gel samples were exposed to clinical 6 MV photons in the dose range between 0 and 20 Gy. Nuclear magnetic resonance relaxometry measurements were per- formed and the sensitivity to photon beams was measured for various values of the Fe2+ ion concentration. The analyses pointed out that the MR signal increases as the Fe2+ content in- creases and the increase is about 75 % when the concentration of Fe2+ ions is increased from 0.5 mM to 2.5 mM. Furthermore, the sensitivity improvement achieved with increasing the Fe2+ concentration is about 60 %. This paper shows that the portable nuclear magnetic resonance relaxometer used for analysis of porous materials can be used for characterization of these dosimetric gels and this study can be considered as the first step for the characterization of these dosimeters which in future could be used for 3-D dose mapping in clinical applications.

scholarly journals Characterization of moisture in acetylated and propionylated radiata pine using low-field nuclear magnetic resonance (LFNMR) relaxometry

Holzforschung ◽  
2018 ◽  
Vol 72 (3) ◽  
pp. 225-233 ◽  
Author(s):  
Greeley Beck ◽  
Emil Engelund Thybring ◽  
Lisbeth Garbrecht Thygesen ◽  
Callum Hill
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Cell Wall ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Radiata Pine ◽  
Saturation Point ◽  
Weight Percentage ◽  
Low Field ◽  
Nuclear Magnetic

AbstractMoisture in radiata pine (Pinus radiataD. Don) earlywood (EW), which was acetylated or propionylated to various degrees, was measured by low-field nuclear magnetic resonance (LFNMR) relaxometry. Spin-spin relaxation times (T2) were determined for fully saturated samples at 22 and −18°C.T2values for EW lumen water increased with increasing acetylation weight percentage gain (WPG), perhaps caused by the less hydrophilic acetylated wood (AcW) surface. Cell wall water (WCW) and the water in pits and small voids also showed increasingT2values as a function of WPG but with a weaker tendency. A possible explanation is the counteracting effects of decreased hydrophilicity and reduced moisture content (MC) of these water populations at higher levels of acetylation. The evaluation of propionylation on WCWT2data was complicated by peak splitting in the relaxation spectrum. ConstantT2values for void water populations at various WPG levels for propionylated samples indicate a modification gradient in the cell wall. Fiber saturation point (FSP) was significantly reduced by both modifications. Slightly higher FSP values for propionylated samples suggest that physical bulking is not the only factor causing moisture exclusion in AcW. But this interpretation is tentative because of the possibility of cell wall damage caused by propionylation.

scholarly journals Nuclear Magnetic Resonance (NMR) Characterization of a Polymerized Ionic Liquid Electrolyte Material

2012 ◽  
Vol 1440 ◽  
Author(s):  
A.L. Michan ◽  
G.T.M. Nguyen ◽  
O. Fichet ◽  
F. Vidal ◽  
C. Vancaeyzeele ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Field Gradient ◽  
Diffusion Coefficients ◽  
Polymer Network ◽  
Relaxation Times ◽  
Solid Polymer ◽  
Pulsed Field ◽  
Nuclear Magnetic

ABSTRACTSolid electrolyte materials have the potential to improve performance and safety characteristics of lithium-ion batteries by replacing conventional solvent-based electrolytes. A candidate solid polymer electrolyte, AMLi/PEGDM, has been synthesized by crosslinking an anionic monomer AMLi, with poly(ethylene glycol) dimethacrylate. The main goal of the synthesis is to produce a single-ion conducting polymer network where lithium cations can move freely and fluorinated anions are immobilized as part of the polymer network. A comprehensive characterization of anion and cation mobility in the resulting material is therefore required. Using pulsed-field gradient nuclear magnetic resonance (PFG-NMR), we are able to measure and quantify the individual diffusion coefficients of mobile species in the material (19F and 7Li) and confirm the extent to which the fluorinated anionic component is immobilized. We have characterized dry (σ~3.0 x10-7 S/cm at 30°C) and propylene carbonate (PC) saturated gel (σ~1.0x10-4 S/cm at 30°C) samples. Experimental results include NMR spin-spin and spin-lattice relaxation times in addition to diffusion coefficient measurements over a temperature range up to 100°C. Practically, the diffusion measurements are extremely challenging, as the spin-spin (T2) relaxation times are very short, necessitating the development of specialized pulsed-field gradient apparatus. Diffusion coefficients for the most mobile components of the lithium cations and fluorinated anions at 100°C in dry membranes have been found to be 3.4 x10-8 cm2/s and 2.1 x10-8 cm2/s respectively. These results provide valuable insight into the conduction mechanisms in these materials, and will drive further optimization of solid polymer electrolytes.

Characterization of ferrous-methylthymol blue-polyvinyl alcohol gel dosimeters using nuclear magnetic resonance and optical techniques

2018 ◽  
Vol 148 ◽  
pp. 25-32 ◽  
Author(s):  
Khalid A. Rabaeh ◽  
Molham M. Eyadeh ◽  
Tariq F. Hailat ◽  
Feras M. Aldweri ◽  
Samer M. Alheet ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Polyvinyl Alcohol ◽  
Optical Techniques ◽  
Methylthymol Blue ◽  
Nuclear Magnetic

PERFIDI FILTERS VALIDATION: FROM NUCLEAR MAGNETIC RESONANCE RELAXOMETRY TO MAGNETIC RESONANCE IMAGING

2015 ◽  
Vol 15 (02) ◽  
pp. 1540018
Author(s):  
LUCA BALBI ◽  
VILLIAM BORTOLOTTI ◽  
LEONARDO BRIZI ◽  
PAOLA FANTAZZINI ◽  
DANILO GRECO ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Inversion Recovery ◽  
Time Inversion ◽  
Resonance Imaging ◽  
Electronic Band ◽  
Nuclear Magnetic Resonance Relaxometry ◽  
Nuclear Magnetic

In order to well distinguish different tissues of the human body by magnetic resonance imaging (MRI), it is of great importance to find procedures to improve the image contrast. In particular, a valuable feature is to image only specific parts of organs and/or tissues while ignoring all the others. Dedicated MRI sequences able to filter the 1 H nuclei signals based on the different longitudinal relaxation times (T1) of the tissues have been developed. Standard signal selection/attenuation sequences, such as the Short Time Inversion Recovery and Multiple Inversion Recovery, have the effect to zero the signal for a discrete number of T1 values. Parametrically Enabled Relaxation Filters with Double and multiple Inversion (PERFIDI) sequences act on a range of T1 values and behave as an electronic band-pass or high-pass or low-pass filters. PERFIDI filters are therefore primarily focused on the components that pass through, rather than on those that are blocked. These filters have been developed and tested by nuclear magnetic resonance relaxometry. Here, these sequences have been validated for MRI on phantom samples to mimic T1 distributions present in tissues. Preliminary applications show that PERFIDI filters can effectively work on a range of T1 values to give well contrasted images.

Nuclear magnetic resonance relaxometry characterization of D2-mdx mice

2017 ◽  
Vol 27 ◽  
pp. S124
Author(s):  
A. Martins-Bach ◽  
E. Araujo ◽  
B. Matot ◽  
Y. Fromes ◽  
P. Baudin ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Mdx Mice ◽  
Nuclear Magnetic Resonance Relaxometry ◽  
Nuclear Magnetic

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

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