Non-invasive cardiovascular magnetic resonance assessment of pressure recovery distance after aortic valve stenosis.

Background: Decisions in the management of aortic stenosis are based on the peak pressure drop, captured by Doppler echocardiography, whereas gold standard catheterization measurements assess the net pressure drop but are limited by associated risks. The relationship between these two measurements, peak and net pressure drop, is dictated by the pressure recovery along the ascending aorta which is mainly caused by turbulence energy dissipation. Currently, pressure recovery is considered to occur within the first 40-50 mm distally from the aortic valve, albeit there is inconsistency across interventionist centers on where/how to position the catheter to capture the net pressure drop.

Unlocking the Non-invasive Assessment of Conduit and Reservoir Function in the Aorta : The Obstructive Descending Aorta in HLHS.

Aortic surgeries in congenital conditions, such as hypoplastic left heart syndrome (HLHS), aim to restore and maintain the conduit and reservoir functions of the aorta. We proposed a method to assess these two functions based on 4D flow MRI, and we applied it to study the aorta in pre-Fontan HLHS. Ten pre-Fontan HLHS patients and six age-matched controls were studied to derive the advective pressure difference and viscous dissipation for conduit function, and pulse wave velocity and elastic modulus for reservoir function.

Dieldrin uptake by vegetable crops grown in contaminated soils.

The aim of these trials was to study the distribution of dieldrin in soil and its translocation to roots and the aerial parts of vegetable crops grown in greenhouses and fields. The main objectives were to characterize dieldrin accumulation in plant tissues in relation to the levels of soil contamination; uptake capability among plants belonging to different species, varieties and cultivars. The presence of the contaminant was quantified by gas chromatography-electron capture detector (GC-ECD) and confirmed by gas chromatography-mass spectrometer (GC-MS).

Online remeshing for soft tissue simulation in surgical training.

To graphically model and animate the realistic behavior of deformable tissue in surgical simulations, the authors' system adapts tetrahedra resolution by dynamically retessellating the mesh in and around the regions of interest. This technique overcomes limitations of previous methods that made it difficult to modify the mesh's topology online.

Soft tissue deformation using a nonlinear hierarchical finite element model with real-time online refinement.

Simulating soft tissue deformation in real-time is a requirement for realistically rendering the VR interaction between human organs and surgical tools. Finite Element Model (FEM) describes complex mechanical and physiological behaviour but it is computationally too demanding especially when a nonlinear model is to be implemented. For this reason, we introduce a multiresolution approach to FEM that only employs the region of the object under deformation to find the solution of the differential equations of motion.

Validation of soft tissue properties in surgical simulation with haptic feedback.

Numerous experiments are being conducted to extract soft tissue values for their integration into VR surgical simulations with haptic feedback. Haptic feedback has been shown to be relevant in laparoscopic surgery, however to date no experiments have been conducted to test user sensitivity to changes in soft tissue values in surgical simulations, and how users perception of 'reality' differs from experimentally determined soft tissue values. In this study we conduct a series of experiments investigating haptic sensitivity, haptic differentiation and comparing experimental and empirical values.

Segmentation and generation of patient-specific 3D models of anatomy for surgical simulation.

Patient-specific simulation requires detailed 3D anatomical models. This paper describes how using optimised MRI sequences and clear segmentation criteria, together with adequate segmentation tools can produce high fidelity models able to reflect anatomical variability and allow realistic simulation of operative techniques and conditions.

Soft tissue deformation using a Hierarchical Finite Element Model.

Simulating soft tissue deformation in real-time has become increasingly important in order to provide a realistic virtual environment for training surgical skills. Several methods have been proposed with the aim of rendering in real-time the mechanical and physiological behaviour of human organs, one of the most popular being Finite Element Method (FEM). In this paper we present a new approach to the solution of the FEM problem introducing the concept of parent and child mesh within the development of a hierarchical FEM.