Do we need MRI and/or CEUS for diagnosis of prostate center?

Abstract only

Modelling selective activation of small myelinated nerve fibres using a monopolar point electrode

The aim of this study is to investigate theoretically the possibility for activation of small myelinated nerve fibres without activating larger ones when stimulating a nerve fibre bundle using a monopolar point electrode. Therefore, the sensitivity of excitation and blocking threshold currents of nerve fibres to fibre diameter, electrode-fibre distance and pulse duration has been simulated by a computer model. A simple infinite, homogeneous volume conductor and a cathodal point source were used in combination with a model representing the electrical properties of a myelinated nerve fibre. The results show that selective activation of small myelinated fibres may be possible in a region at some distance from the electrode

Observed cumulative time delay between second harmonic and fundamental component of pressure wave fields propagating through ultrasound contrast agentss

Several studies on the propagation velocity of pressure wave fields through ultrasound contrast agents (UCAs) have been reported in the literature. However, the variation of propagation velocity between the fundamental and the second harmonic component generated during the propagation of ultrasound through UCAs has, to our knowledge, not been studied yet. To this scope, dedicated transmission and backscattering measurements of pressure wave fields propagating through SonoVue and Definity contrast agents, are analyzed. Results show the occurrence of a cumulative delay between the time signals related to the second harmonic and fundamental component, suggesting a smaller propagation velocity for the second harmonic as compared to the fundamental component. Moreover, this time delay increases with increasing UCA concentration and propagation path length of ultrasound trough microbubbles, depends on mechanical index and frequency, and, most importantly, is not observed in the absence of UCAs. These results may be relevant to contrast-enhanced ultrasonography, opening up to new possibilities to increase contrast-to-tissue ratios and to quantify UCA concentration

Towards dynamic contrast specific ultrasound tomography

We report on the first study demonstrating the ability of a recently-developed, contrast-enhanced, ultrasound imaging method, referred to as cumulative phase delay imaging (CPDI), to image and quantify ultrasound contrast agent (UCA) kinetics. Unlike standard ultrasound tomography, which exploits changes in speed of sound and attenuation, CPDI is based on a marker specific to UCAs, thus enabling dynamic contrast-specific ultrasound tomography (DCS-UST). For breast imaging, DCS-UST will lead to a more practical, faster, and less operator-dependent imaging procedure compared to standard echo-contrast, while preserving accurate imaging of contrast kinetics. Moreover, a linear relation between CPD values and ultrasound second-harmonic intensity was measured (coefficient of determination = 0.87). DCS-UST can find clinical applications as a diagnostic method for breast cancer localization, adding important features to multi-parametric ultrasound tomography of the breast.</p

Upper airway pressure distribution during nasal high-flow therapy

Two working mechanisms of Nasal High-Flow Therapy (NHFT) are washout of anatomical dead space and provision of positive end-expiratory pressure (PEEP). The extent of both mechanisms depends on the respiration aerodynamics and the corresponding pressure distribution: at end-expiration the onset of uniform pressure indicates the jet penetration length, and the level of the uniform pressure is the PEEP. The clinical problem is that adequate measurements in patients are presently impossible. In this study, the respiratory pressure distribution is therefore measured in 3D-printed anatomically correct upper-airway models of an adult and an infant. Assuming that elastic fluctuations in airway anatomy are sufficiently small, the aerodynamics in these rigid models will be very similar to the aerodynamics in patients. It appears that, at end-expiration, the jet penetrates into or slightly beyond the nasal cavity, hardly depending on cannula size or NHFT flow rate. PEEP is approximately proportional to the square of the flow rate: it can be doubled by increasing the flow rate by 40%. In the adult model, PEEP is accurately predicted by the dynamic pressure at the prong-exits, but in the infant model this method fails. During respiration, large pressure fluctuations occur when the cannula is relatively large compared to the nostrils