Assessment of liver fibrosis by variable flip angle T1 mapping at 3.0T.

PURPOSE: To evaluate the possibility of using a variable flip angle (VFA) T1 mapping technique to diagnose liver fibrosis. MATERIALS AND METHODS: Liver fibrosis was induced in rabbits by repetitive administration of carbon tetrachloride (CCl4 ). T1 -weighted magnetic resonance imaging (MRI) was performed in 29 animals (liver fibrosis, n = 18; control, n = 11) using a series of nonenhanced liver acquisition volume acceleration (LAVA) with VFAs at 3.0T. Hepatic T1 relaxation times were measured via regions of interest, which were correlated with subsequent histologic confirmation. The results of T1 mapping in assessment of liver fibrosis were compared with that of apparent diffusion coefficient (ADC) values. RESULTS: The mean T1 relaxation time of the control group was the lowest (250.07 ± 88.12 msec), followed by the nonadvanced fibrosis group (387.83 ± 166.58 msec) and the advanced fibrosis group (496.90 ± 291.24 msec). T1 relaxation time measurements differed significantly between the liver fibrosis group and control group (P < 0.05), with a trend of increased mean T1 relaxation times as the fibrotic stage increased. Statistically significant differences were observed between the control group and the nonadvanced fibrosis group (P < 0.05), however with much overlap between the less severe stages. In discriminating between the control group and liver fibrosis group, stage F0-1 (control and stage F1) and stage F2-3, stage F0-2 (control and stage F1-2) and stage F3, area under the receiver operating characteristic (ROC) curves were 0.803 (cutoff value 273.01 msec), 0.712 (cutoff value 371.54 msec), and 0.696 (cutoff value 276.99 msec), respectively. No difference was found between T1 relaxation times and ADC values in assessment of liver fibrosis in our study. CONCLUSION: VFA T1 mapping may become a noninvasive imaging tool for the diagnosis of liver fibrosis.

Assessment of liver fibrosis in rats by MRI with apparent diffusion coefficient and T1 relaxation time in the rotating frame.

PURPOSE: To explore the value of T1 relaxation times in the rotating frame (T1 ρ or T1 rho) for evaluating liver fibrosis stage, compared to apparent diffusion coefficients (ADCs). MATERIALS AND METHODS: Liver fibrosis in model rats (n = 50) was produced by carbon tetrachloride (CCl4 ) injection. Five rats died during the experiment. Surviving model rats (n = 45) and controls (n = 15) were subjected to 3.0T MRI and the ADCs (b-values: 0, 800 s/mm(2) ) and T1 ρ values were determined. Liver fibrosis stage (F0-F4) was defined based on METAVIR scoring. Nonparametric statistical methods and receiver operating characteristic (ROC) curve analyses were employed to determine diagnostic accuracy. RESULTS: Mean ADC and T1 ρ associated negatively (r = -0.732 P < 0.001) and positively (r = 0.863 P < 0.001), respectively, with severity of fibrosis stage. Analysis of ROC curves for fibrosis staging showed that the area under the curve (AUC) for T1 ρ (stage F0 vs. F1-F4 = 0.976, stage F0-F1 vs. F2-F4 = 0.920, stage F0-F2 vs. F3-F4 = 0.938, and stage F0-F3 vs. F4 = 0.931) was larger than that for ADCs (0.917, 0.924, 0.842, and 0.781, respectively). CONCLUSION: ADC and T1 ρ values correlate with liver fibrosis stage. The performance of the T1 ρ parameter was superior to that of the ADC parameter in the differentiation of liver fibrosis stages in a CCl4 rat model.

On the performance of Cu-BTC metal organic framework for carbon tetrachloride gas removal.

The performance of Cu-BTC metal organic framework for carbon tetrachloride removal from air has been studied using molecular simulations. According to our results, this material shows extremely high adsorption selectivity in favour of carbon tetrachloride. We demonstrate that this selectivity can be further enhanced by selective blockage of the framework.

Isotopic and geochemical assessment of in situ biodegradation of chlorinated hydrocarbons.

Currently there is no in situ method to detect and quantify complete mineralization of chlorinated hydrocarbons (CHCs) to CO2. Combined isotopic measurements in conjunction with traditional chemical techniques were used to assess in situ biodegradation of trichloroethylene (TCE) and carbon tetrachloride (CT). Vadose zone CHC, ethene, ethane, methane, O2, and CO2 concentrations were analyzed using gas chromatography over 114 days at the Savannah River Site. delta13C of CHC and delta13C and 14C of vadose zone CO2, sediment organic matter, and groundwater dissolved inorganic carbon (DIC)were measured. Intermediate metabolites of TCE and CT accounted for < or = 10% of total CHCs. Delta13C of cis-1,2-dichloroethylene (DCE) was always heavier than TCE indicating substantial DCE biodegradation. 14C-CO2 values ranged from 84 to 128 percent modern carbon (pMC), suggesting that plant root-respired CO2 was dominant. 14C-CO2 values decreased over time (up to 12 pMC), and contaminated groundwater 14C-DIC (76 pMC) was substantially depleted relative to the control (121 pMC). 14C provided a direct measure of complete CHC mineralization in vadose zone and groundwater in situ and may improve remediation strategies.

Efficient assessment of modified nucleoside stability under conditions of automated oligonucleotide synthesis: characterization of the oxidation and oxidative desulfurization of 2-thiouridine.

In order to efficiently assess the chemical stability of modified nucleosides to the reagents and conditions of automated oligonucleotide synthesis, we designed, developed and tested a scheme in which the modified nucleoside, directly attached to a solid support, is exposed to the cyclic chemistry of the instrument. Stability of 2-thiouridine against different oxidizers was investigated. Tertbutyl hydroperoxide (1 M) in anhydrous acetonitrile was a more effective oxidizer for the incorporation of 2-thiouridine into oligonucleotide chains than the same oxidizer in methylene chloride. Carbon tetrachloride/water in the presence of a basic catalyst was superior in maintaining the thiocarbonyl function, but its utility for RNA synthesis has yet to be fully tested, whereas 2-phenylsulfonyloxaziridine was a very efficient reagent for oxidative desulfurization of 2-thiouridine.

Monte Carlo simulation of the influence of solvent on nucleic acid base associations.

The results of Monte Carlo calculations of the association between nucleic acid bases in a nonpolar solvent (CCl4) are described. The influence of the solvent on planar and stacked associations of bases was examined by analyzing the total energy of the system, including solute-solute, solute-solvent, and solvent-solvent contributions. Good quantitative agreement with the available experimental data was obtained. Solute-solvent interactions are primarily determined by dispersion forces; consequently, solute-solvent interactions vertical to the solute plane that maximize dispersion interactions are most favored, and a rough proportionally between solute-solvent energy and the surface of the solute was observed. Analysis of solvent-solvent energy is not necessarily reduced when surface area decreases, contrary to the simple cavity concept. "Single molecule probe" calculations were performed to explain the differences in base associations in H2O and CCl4. In CCl4 dispersion forces dominate and planar complexes are stabilized by maximum exposure of molecular planes to the solvent. In H2O electrostatic forces dominate so that the most stable structures are stacked association that allow the maximum number of hydrophilic centers to be exposed to the solvent.