No abstract

Many substances of forensic interest are chiral and available either as racemates or pure enantiomers. Application of chiral analysis in biological samples can be useful for the determination of legal or illicit drugs consumption or interpretation of unexpected toxicological effects. Chiral substances can also be found in environmental samples and revealed to be useful for determination of community drug usage (sewage epidemiology), identification of illicit drug manufacturing locations, illegal discharge of sewage and in environmental risk assessment. Thus, the purpose of this paper is to provide an overview of the application of chiral analysis in biological and environmental samples and their relevance in the forensic field. Most frequently analytical methods used to quantify the enantiomers are liquid and gas chromatography using both indirect, with enantiomerically pure derivatizing reagents, and direct methods recurring to chiral stationary phases.

Optical coherence tomography (OCT) is becoming one of the most important imaging modalities in ophthalmology due to its non-invasiveness and by allowing the visualisation the human retina structure in detail. It was recently proposed that OCT data embeds functional information from the human retina. Specifically, it was proposed that blood-retinal barrier status information is present within OCT data from the human retina. Besides this ability, the authors present data supporting the idea of having the OCT data encoding the ageing of the retina in addition to the disease (diabetes) condition from the healthy status. The methodology followed makes use of a supervised classification procedure, the support vector machine (SVM) classifier -based solely on the statistics of the distribution of OCT data from the human retina (i.e. OCT data between the inner limiting membrane and the retinal pigment epithelium). Results achieved suggest that information on both the healthy status of the blood-retinal barrier and on the ageing process co-exist encoded within the optical properties of the human retina.

Purpose To demonstrate the presence of blood‐retinal barrier (BRB) function information within OCT data. Methods It was recently suggested that OCT data embeds functional information on BRB status. In this work a different approach was followed resorting to the use of support vector machines (SVM) to discriminate between healthy (N=31), ETDRS level 10 diabetic retinopathy (DR) (N=31) and diabetic macular edema (DME) eyes (N=31). Healthy volunteers and diabetic patients underwent Cirrus HD‐OCT (Carl Zeiss Meditec, Dublin, USA) using both the 512x128 and the 200x200 Macular Cube Protocols. Data was exported and the intensity distributions were computed for each eye, taking into consideration only the retina (between the inner limiting membrane ILM and the retinal pigment epithelium RPE), both on the logarithmic and linear spaces. A total of 43 parameters per eye were computed and labeled accordingly (healthy, DR and DME). A publicly available SVM toolbox (LIBSVM) was applied to assess the possibility of discriminating between each of these groups using a radial basis function (RBF) kernel and the leave‐one‐out approach for validation. Results Achieved results allow to conclude on the possibility of discriminating between healthy and DR eyes (level 10 ETDRS and DME eyes). Of added value is the fact the system is able to discriminate between healthy and ETDRS level 10 DR eyes. This suggests that optical properties of the retina are modified and that this change cannot be currently detected using any other available technique. Conclusion In this work, it was demonstrated the presence of early changes in the optical properties of the human retina related to diabetes, and that this information is embedded in OCT data. Support: FCT/PTDC/SAU‐BEB/103151/2008