An ordered mesoporous silica ( OMS ) was synthesized through hydrothermal process. The synthesized material was characterized by different techniques such as X-ray diffraction, nitrogen adsorption-desorption and transmission electron microscope. The electrochemical characteristics of the OMS modified carbon paste electrode ( OMS/CPE ) were investigated by using cyclic voltammetry and electrochemical impedance spectroscopy. Compared with bare carbon paste electrode ( CPE ) , the OMS/CPE exhibited a larger electrode surface and a faster electron-transfer rate. Electrochemical behaviors and kinetic properties of L-tryptophan ( L-Trp) at the OMS/CPE in the presence of sodium dodecylsulphate ( SDS) were studied. The results showed that the voltammetric response of L-Trp at OMS/CPE was improved due to the synergistic effect of OMS and SDS. The electrochemical oxidation of L-Trp at OMS/CPE in the presence of SDS was an irreversible process involved two electrons and two protons, and the electrode process was controlled by the adsorption step. Some parameters such as SDS concentration, accumulation time, accumulation potential and pH were optimized. Under optimal conditions, the oxidation peak current was linearly proportional to L-Trp concentration in the range of 8. 0×10-8 to 4. 0×10-6 mol/L, with a detection limit of 7. 0×10-8 mol/L (S/N=3 ) . The proposed method was applied for the determination of L-Trp in oral liquid with the recoveries of 99 . 6%-102 . 6%.

OBJECTIVETo assess the value of contrast-enhanced ultrasonography (CEUS) and fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET/CT) in evaluating the stability of carotid atherosclerosis.

METHODSSeventeen patients with 21 carotid artery plaques received examinations with CEUS. According to the nature of the plaques, the patients were divided into soft and mixed plaque group and hard and calcified plaque group. The maximal enhancement intensity of the plaques (I(MAX)) and maximal plaque density (D(MAX)) were measured to quantify the neovasculature. The patients also underwent concurrent ¹⁸F-FDG PET/CT, and ¹⁸F-FDG uptake was quantified by the mean standard uptake values (SUV(mean)), an index reflecting the inflammatory activity in the plaque. The findings in CEUS and PET/CT were comparatively analyzed for these cases.

RESULTSThe D(MAX) of the plaque in soft and mixed plaque group was significantly greater than that in hard and calcified plaque group (4.26±3.65 vs 1.41±1.47, P<0.05); the I(MAX) was also greater in the former group, but this difference was not statistically significant (26.83±19.61 vs 24.73±29.85, P=0.869). The soft and mixed plaques tended to have higher SUVmean than the hard and calcified plaques (1.70±0.45 vs 1.47±0.12, P=0.099). The values of I(MAX) and D(MAX) were not found to correlate to SUV(mean) in these patients.

CONCLUSIONCEUS can sensitively show the status of neovascularization within the carotid atherosclerosis plaques, and PET/CT reflects the inflammatory activity in the plaques. The combination of these two imaging modalities allows the evaluation of plaque stability in terms of neoangiogenesis and inflammatory activity.

Aged ; Aged, 80 and over ; Carotid Stenosis ; diagnostic imaging ; Female ; Fluorodeoxyglucose F18 ; Humans ; Male ; Middle Aged ; Positron-Emission Tomography ; Tomography, X-Ray Computed