A Bayesian estimation method for cerebral blood flow measurement by area-detector CT perfusion imaging.

PURPOSE: Bayesian estimation with advanced noise reduction (BEANR) in CT perfusion (CTP) could deliver more reliable cerebral blood flow (CBF) measurements than the commonly used reformulated singular value decomposition (rSVD). We compared the efficacy of CBF measurement by CTP using BEANR and rSVD, evaluating both relative to N-isopropyl-p-[(123) I]- iodoamphetamine ((123)I-IMP) single-photon emission computed tomography (SPECT) as a reference standard, in patients with cerebrovascular disease. METHODS: Thirty-one patients with suspected cerebrovascular disease underwent both CTP on a 320 detector-row CT system and SPECT. We applied rSVD and BEANR in the ischemic and contralateral regions to create CBF maps and calculate CBF ratios from the ischemic side to the healthy contralateral side (CBF index). The analysis involved comparing the CBF index between CTP methods and SPECT using Pearson's correlation and limits of agreement determined with Bland-Altman analyses, before comparing the mean difference in the CBF index between each CTP method and SPECT using the Wilcoxon matched pairs signed-rank test. RESULTS: The CBF indices of BEANR and (123)I-IMP SPECT were significantly and positively correlated (r = 0.55, p  0.05). BEANR produced smaller limits of agreement for CBF than rSVD. The mean difference in the CBF index between BEANR and SPECT differed significantly from that between rSVD and SPECT (p < 0.001). CONCLUSIONS: BEANR has a better potential utility for CBF measurement in CTP than rSVD compared to SPECT in patients with cerebrovascular disease

Development and validation of an HPLC-MS method for the simultaneous quantification of key oxysterols, endocannabinoids, and ceramides: variations in metabolic syndrome

Oxysterols, ceramides, and endocannabinoids are three families of bioactive lipids suggested to be involved in obesity and metabolic syndrome. To facilitate the quantification of these potentially interconnected lipids, we have developed and validated a liquid chromatography coupled to mass spectrometry method allowing for their simultaneous quantification from tissues. Sample purification is of great importance when quantifying oxysterols due to the potential artifactual conversion of cholesterol into oxysterols. Therefore, we developed a novel solid-phase extraction procedure and demonstrated that it allowed for good recoveries of the three families of analytes without artifactual oxidation of cholesterol. The oxysterols, ceramides, and endocannabinoids and their respective internal standards were chromatographically separated by HPLC and ionized using the atmospheric pressure chemical ionization (APCI) source of an LTQ-orbitrap mass spectrometer. The repeatability and bias were within the acceptance limits for all 23 lipids of interest. The sensitivity (limit of detection (LOD) and limit of quantification (LOQ)) and specificity of the method allowed us to quantify all the analytes in the liver and adipose tissue of control and high-fat diet-fed C57BL/6 mice. We found that 16 weeks of high-fat diet strongly impacted the hepatic levels of several oxysterols, ceramides, and endocannabinoids. A partial least-squares discriminant analysis (PLS-DA) based on the variations of the hepatic levels of these 23 bioactive lipids allowed differentiating the lean mice from the obese mic