Integration of patient-specific myocardial perfusion in CT-based FFR computations

Computed Tomography based Fractional Flow Reserve (FFRCT) is a non-invasive simulation based measure for diagnosing ischaemia causing arterial stenoses. One drawback of simulation based measures are the assumptions made that are usually based on population studies that may not apply to all patients. This study describes the fundamental characteristics to FFRCT simulations and how the simulations can be simplified where it can and where assumptions break down. The investigation starts with assessing whether the simulations can be simplified to a steady flow, whilst uncharacteristic of typical coronary blood flow, it was demonstrated that with regards to the diagnostic measures of FFR, and its variants dFFR or iFR, that steady flow was applicable, which reduces the complexity of the simulation, saving computational time and resources as well as removing uncertainty in the input assumptions.[1] The next phase of the study explored the downstream conditions of the FFRCT simulation scheme. The microvasculature is too small to resolve in CT imaging and therefore assumptions are made regarding its form and function. Whilst form function relationships of the microvasculature are well established in the literature for the structure of microvessels at rest, assumptions regarding stress or hyperaemia are used for FFRCT to simulate maximal blood flow through the coronary arteries. The investigation utilised perfusion imaging to assess the validity of this assumption and showed how variable the microvascular response to hyperaemia is, and the effect that has on FFRCT.[2][3] The last part of the study produced a novel method of estimating the microvascular response using patient metrics such as age, sex, diabetes, smoker status etc, from a training dataset of 101 patients. By using the patient-specific microvascular response, FFRCT simulations better represent the coronary artery health of the patient. On a separate dataset of 10 patients, the FFRCT measurements using this novel method was also validated against the gold standard invasive FFR and has demonstrated a better diagnostic performance (94% accuracy) than the conventional method (82% accuracy). Secondly the novel method also created a probabilistic spread of FFRCT values that may provide better utility than a strict binary measure. Whilst this novel method will require further validation with larger studies, it nevertheless has potential to address some of the current drawbacks of FFRCT methods when applied to a varied patient demographic

Energy-Efficient Power Allocation in OFDM Systems with Wireless Information and Power Transfer

This paper considers an orthogonal frequency division multiplexing (OFDM) downlink point-to-point system with simultaneous wireless information and power transfer. It is assumed that the receiver is able to harvest energy from noise, interference, and the desired signals. We study the design of power allocation algorithms maximizing the energy efficiency of data transmission (bit/Joule delivered to the receiver). In particular, the algorithm design is formulated as a high-dimensional non-convex optimization problem which takes into account the circuit power consumption, the minimum required data rate, and a constraint on the minimum power delivered to the receiver. Subsequently, by exploiting the properties of nonlinear fractional programming, the considered non-convex optimization problem, whose objective function is in fractional form, is transformed into an equivalent optimization problem having an objective function in subtractive form, which enables the derivation of an efficient iterative power allocation algorithm. In each iteration, the optimal power allocation solution is derived based on dual decomposition and a one-dimensional search. Simulation results illustrate that the proposed iterative power allocation algorithm converges to the optimal solution, and unveil the trade-off between energy efficiency, system capacity, and wireless power transfer: (1) In the low transmit power regime, maximizing the system capacity may maximize the energy efficiency. (2) Wireless power transfer can enhance the energy efficiency, especially in the interference limited regime.Comment: 6 pages, Accepted for presentation at the IEEE International Conference on Communications (ICC) 201

Energy-Efficient Resource Allocation in Multiuser OFDM Systems with Wireless Information and Power Transfer

In this paper, we study the resource allocation algorithm design for multiuser orthogonal frequency division multiplexing (OFDM) downlink systems with simultaneous wireless information and power transfer. The algorithm design is formulated as a non-convex optimization problem for maximizing the energy efficiency of data transmission (bit/Joule delivered to the users). In particular, the problem formulation takes into account the minimum required system data rate, heterogeneous minimum required power transfers to the users, and the circuit power consumption. Subsequently, by exploiting the method of time-sharing and the properties of nonlinear fractional programming, the considered non-convex optimization problem is solved using an efficient iterative resource allocation algorithm. For each iteration, the optimal power allocation and user selection solution are derived based on Lagrange dual decomposition. Simulation results illustrate that the proposed iterative resource allocation algorithm achieves the maximum energy efficiency of the system and reveal how energy efficiency, system capacity, and wireless power transfer benefit from the presence of multiple users in the system.Comment: 6 pages. The paper has been accepted for publication at the IEEE Wireless Communications and Networking Conference (WCNC) 2013, Shanghai, China, Apr. 201

The therapeutic potential of migrastatin-core analogs for the treatment of metastatic cancer

Tumor metastasis is a complex process in which cells detach from the primary tumor and colonize a distant organ. Metastasis is also the main process responsible for cancer-related death. Despite the enormous efforts made to unravel the metastatic process, there is no effective therapy, and patients with metastatic tumors have poor prognosis. In this regard, there is an urgent need for new therapeutic tools for the treatment of this disease. Small molecules with the capacity to reduce cell migration could be used to treat metastasis. Migrastatin-core analogs are naturally inspired macrocycles that inhibit pathological cell migration and are able to reduce metastasis in animal models. Migrastatin analogs can be synthesized from a common advanced intermediate. Herein we present a review of the synthetic approaches that can be used to prepare this key intermediate, together with a review of the biological activity of migrastatin-core analogs and current hypotheses concerning their mechanism of action

The angular distribution of diffuse photosynthetically active radiation under different sky conditions in the open and within deciduous and conifer forest stands of Quebec and British Columbia, Canada

The angular distribution of diffuse photosynthetically active radiation (PAR) was characterised in the open and beneath deciduous and conifer forests in Quebec and British Columbia, Canada, under overcast and clear sky conditions, using a restricted field of view light sensor and hemispherical canopy photographs. The angular distribution of PAR was described by the relative light reading (RLR). In the open on overcast days, light was best characterized using the standard overcast sky distribution with the light intensity at the zenith set to four to five times greater than the light intensity at the horizon. RLR under forest stands was found to decrease with decreasing elevation angles under both overcast and clear sky conditions. Aspen (Populus tremuloides Michx.) and Jack pine (Pinus banksiana Lamb.) stands transmitted more light from a relatively wider angle around the zenith than the spruce (Picea glauca (Moench) Voss and Picea mariana (Mill.) BSP) stands, which transmitted light mainly from the zenith. RLR estimated with the hemispherical canopy photographs (RLR hc_corr) generally provided a comparable prediction of the effect of the canopy composition on the angular distribution of PAR