Multispectral photoacoustic microscopy based on an optical–acoustic objective

AbstractWe have developed reflection-mode multispectral photoacoustic microscopy (PAM) based on a novel optical–acoustic objective that integrates a customized ultrasonic transducer and a commercial reflective microscope objective into one solid piece. This technical innovation provides zero chromatic aberration and convenient confocal alignment of the optical excitation and acoustic detection. With a wavelength-tunable optical-parametric-oscillator laser, we have demonstrated multispectral PAM over an ultrabroad spectral range of 270–1300nm. A near-constant lateral resolution of ∼2.8μm is achieved experimentally. Capitalizing on the consistent performance over the ultraviolet, visible, and near-infrared range, multispectral PAM enables label-free concurrent imaging of cell nucleus (DNA/RNA contrast at 270nm), blood vessel (hemoglobin contrast at 532nm), and sebaceous gland (lipid contrast at 1260nm) at the same spatial scale in a living mouse ear

Variability in concentrations of potentially toxic elements in urban parks from six European cities

Use of a harmonised sampling regime has allowed comparison of concentrations of copper, chromium, nickel, lead and zinc in six urban parks located in different European cities differing markedly in their climate and industrial history. Wide concentrations ranges were found for copper, lead and zinc at most sites, but for chromium and nickel a wide range was only seen in the Italian park, where levels were also considerably greater than in other soils. As might be expected, the soils from older cities with a legacy of heavy manufacturing industry (Glasgow, Torino) were richest in potentially toxic elements (PTEs); soils from Ljubljana, Sevilla and Uppsala had intermediate metal contents, and soils from the most recently established park, in the least industrialised city (Aveiro), displayed lowest concentrations. When principal component analysis was applied to the data, associations were revealed between pH and organic carbon content; and between all five PTEs. When pH and organic carbon content were excluded from the PCA, a distinction became clear between copper, lead and zinc (the "urban" metals) on the one hand, and chromium and nickel on the other. Similar results were obtained for the surface (0-10 cm depth) and sub-surface (10-20 cm depth) samples. Comparisons with target or limit concentrations were limited by the existence of different legislation in different countries and the fact that few guidelines deal specifically with public-access urban soils intended for recreational use

Ultrasound-aided multi-parametric photoacoustic microscopy of the mouse brain

High-resolution quantitative imaging of cerebral oxygen metabolism in mice is crucial for understanding brain functions and formulating new strategies to treat neurological disorders, but remains a challenge. Here, we report on our newly developed ultrasound-aided multi-parametric photoacoustic microscopy (PAM), which enables simultaneous quantification of the total concentration of hemoglobin (C(Hb)), the oxygen saturation of hemoglobin (sO(2)), and cerebral blood flow (CBF) at the microscopic level and through the intact mouse skull. The three-dimensional skull and vascular anatomies delineated by the dual-contrast (i.e., ultrasonic and photoacoustic) system provide important guidance for dynamically focused contour scan and vessel orientation-dependent correction of CBF, respectively. Moreover, bi-directional raster scan allows determining the direction of blood flow in individual vessels. Capable of imaging all three hemodynamic parameters at the same spatiotemporal scale, our ultrasound-aided PAM fills a critical gap in preclinical neuroimaging and lays the foundation for high-resolution mapping of the cerebral metabolic rate of oxygen (CMRO(2))—a quantitative index of cerebral oxygen metabolism. This technical innovation is expected to shed new light on the mechanism and treatment of a broad spectrum of neurological disorders, including Alzheimer’s disease and ischemic stroke

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Modelling techniques for 1-3 composite transducers

A selection of novel modelling techniques are presented for predicting the behaviour of a thickness mode composite piezoelectric transducer comprising an array of ceramic pillars embedded in a polymer matrix. Finite element analysis is employed to establish the vibrational and electromechanical characteristics of an arbitrary composite structure. Thereafter, the equivalent thickness mode transducer parameters are employed in a modified transducer model to establish the impedance, transmission and reception characteristics. A novel algorithm for calculating the acoustic pressure profile, resulting from an arbitrarily excited, rectangular aperture is employed to determine the field structure of the composite transducer. This algorithm is incorporated into an array model capable of predicting the field characteristics of steered and focused arrays. Theoretical and practical results, for composite, sliced and monolithic ceramic arrays are compared. Finally, low frequency, stacked composite structures are considered. A range of novel characteristics are obtained by using, to full advantage, the versatility of composite materials. It is believed that these modelling techniques, which have been verified experimentally, offer considerable insight into composite transducer behaviour and are conducive to effective, computer based, design.A selection of novel modelling techniques are presented for predicting the behaviour of a thickness mode composite piezoelectric transducer comprising an array of ceramic pillars embedded in a polymer matrix. Finite element analysis is employed to establish the vibrational and electromechanical characteristics of an arbitrary composite structure. Thereafter, the equivalent thickness mode transducer parameters are employed in a modified transducer model to establish the impedance, transmission and reception characteristics. A novel algorithm for calculating the acoustic pressure profile, resulting from an arbitrarily excited, rectangular aperture is employed to determine the field structure of the composite transducer. This algorithm is incorporated into an array model capable of predicting the field characteristics of steered and focused arrays. Theoretical and practical results, for composite, sliced and monolithic ceramic arrays are compared. Finally, low frequency, stacked composite structures are considered. A range of novel characteristics are obtained by using, to full advantage, the versatility of composite materials. It is believed that these modelling techniques, which have been verified experimentally, offer considerable insight into composite transducer behaviour and are conducive to effective, computer based, design

A multi-agent system for automated post-fault disturbance analysis

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