Reference Tissue-Based Kinetic Evaluation of 18F-AV-1451 for Tau Imaging.

The goal of this paper was to evaluate the in vivo kinetics of the novel tau-specific PET radioligand 18F-AV-1451 in cognitively healthy control (HC) and Alzheimer disease (AD) subjects, using reference region analyses. METHODS: 18F-AV-1451 PET imaging was performed on 43 subjects (5 young HCs, 23 older HCs, and 15 AD subjects). Data were collected from 0 to 150 min after injection, with a break from 100 to 120 min. T1-weighted MR images were segmented using FreeSurfer to create 14 bilateral regions of interest (ROIs). In all analyses, cerebellar gray matter was used as the reference region. Nondisplaceable binding potentials (BPNDs) were calculated using the simplified reference tissue model (SRTM) and SRTM2; the Logan graphical analysis distribution volume ratio (DVR) was calculated for 30-150 min (DVR30-150). These measurements were compared with each other and used as reference standards for defining an appropriate 20-min window for the SUV ratio (SUVR). Pearson correlations were used to compare the reference standards to 20-min SUVRs (start times varied from 30 to 130 min), for all values, for ROIs with low 18F-AV-1451 binding (lROIs, mean of BPND + 1 and DVR30-150 < 1.5), and for ROIs with high 18F-AV-1451 binding (hROIs, mean of BPND + 1 and DVR30-150 > 1.5). RESULTS: SRTM2 BPND + 1 and DVR30-150 were in good agreement. Both were in agreement with SRTM BPND + 1 for lROIs but were greater than SRTM BPND + 1 for hROIs, resulting in a nonlinear relationship. hROI SUVRs increased from 80-100 to 120-140 min by 0.24 ± 0.15. The SUVR time interval resulting in the highest correlation and slope closest to 1 relative to the reference standards for all values was 120-140 min for hROIs, 60-80 min for lROIs, and 80-100 min for lROIs and hROIs. There was minimal difference between methods when statistical significance between ADs and HCs was calculated. CONCLUSION: Despite later time periods providing better agreement between reference standards and SUVRs for hROIs, a good compromise for studying lROIs and hROIs is SUVR80-100. The lack of SUVR plateau for hROIs highlights the importance of precise acquisition time for longitudinal assessment.

Evaluation of the residual solvent content of counterfeit tablets and capsules.

A group of counterfeit samples of Viagra and Cialis were screened for their residual solvent content and compared to the content of the genuine products. It was observed that all counterfeit samples had higher residual solvent contents compared to the genuine products. A more diverse range of residual solvents was found as well as higher concentrations. In general these concentrations did not exceed the international imposed maximum limits. Only in a few samples the limits were exceeded. A Projection Pursuit analysis revealed clusters of samples with similar residual solvent content, possibly enabling some future perspectives in forensic research.

Analysis of counterfeit Cialis® tablets using Raman microscopy and multivariate curve resolution.

Counterfeit medicines have become a serious global problem. Consequently, analytical and pharmaceutical scientists have been active in developing and applying new methodologies to detect and analyze counterfeit medicines. Vibrational spectroscopy combined with chemometric methods is becoming a popular choice in this area of research. In this study, Raman microscopy was used to collect chemical images of counterfeit tadalafil tablets and multivariate curve resolution (MCR) was used to analyze the Raman spectra and reveal the identities of the excipients and active pharmaceutical ingredients (API) in each tablet. Resolved counterfeit tablet spectra were compared to the resolved genuine tablet spectra. Both similarities and dissimilarities were revealed by the analysis in terms of the identity of the excipients, the quantity of the API, and the distribution of the components. It was concluded that Raman microscopy combined with MCR is a powerful method to detect and analyze counterfeit tablets.