Patient-specific bronchoscopy visualization through BRDF estimation and disocclusion correction

This paper presents an image-based method for virtual bronchoscope with photo-realistic rendering. The technique is based on recovering bidirectional reflectance distribution function (BRDF) parameters in an environment where the choice of viewing positions, directions, and illumination conditions are restricted. Video images of bronchoscopy examinations are combined with patient-specific three-dimensional (3-D) computed tomography data through two-dimensional (2-D)/3-D registration and shading model parameters are then recovered by exploiting the restricted lighting configurations imposed by the bronchoscope. With the proposed technique, the recovered BRDF is used to predict the expected shading intensity, allowing a texture map independent of lighting conditions to be extracted from each video frame. To correct for disocclusion artefacts, statistical texture synthesis was used to recreate the missing areas. New views not present in the original bronchoscopy video are rendered by evaluating the BRDF with different viewing and illumination parameters. This allows free navigation of the acquired 3-D model with enhanced photo-realism. To assess the practical value of the proposed technique, a detailed visual scoring that involves both real and rendered bronchoscope images is conducted.     

Biomechanical and structural changes following the decellularization of bovine pericardial tissues for use as a tissue engineering scaffold

To achieve natural scaffolds for tissue engineering applications we decellularized bovine pericardial (BP) tissues according to two different protocols: a novel treatment based on Triton(?) X-100 (12 h, 4 °C) (BP1) and a trypsin/EDTA treatment (37 °C, 48 h) (BP2). Results were compared with commercially available acellular xenogeneic biomaterials, Veritas(?) and Collamed(?). Biomechanical characteristics, high (E(h)) and low (E(l)) modulus of elasticity, of the fresh untreated tissue varied with the anatomical direction (apex to base (T) to transverse (L)) (mean ± SDEV): (41.63 ± 14.65-48.12 ± 10.19 MPa and 0.27 ± 0.05-0.30 ± 0.12 MPa respectively). BP1 had no mechanical effect (44.65 ± 19.73-52.67 ± 7.59 MPa and 0.37 ± 0.14-0.37 ± 0.11 MPa, respectively) but BP2 resulted in significant decrease in E(h) and E(l) (20.96 ± 8.17-36.82 ± 3.23 MPa and 0.20 ± 0.06-0.23 ± 0.06 MPa). Hysteresis ratio (h) varied (19-26 % of the loading energy) independently of anatomical direction. Glycosaminoglycans content was unaffected by BP1, while 22 % of chondroitin/dermatan sulphate and 60 % of hyaluronan were removed after BP2 treatment. Endothelial cell adhesion was achieved after 24 h and 3 days cell culture.     

Automated gaze-contingent objects elicit orientation following in 8-month-old infants.

The current study tested whether the purely amodal cue of contingency elicits orientation following behavior in 8-month-old infants. We presented 8-month-old infants with automated objects without human features that did or did not react contingently to the infants' fixations recorded by an eye tracker. We found that an object's occasional orientation toward peripheral targets was reciprocated by a congruent visual orientation following response by infants only when it had displayed gaze-contingent interactivity. Our finding demonstrates that infants' gaze-following behavior does not depend on the presence of a human being. The results are consistent with the idea that, in 8-month-old infants, the detection of contingent reactivity, like other communicative signals, can itself elicit the illusion of being addressed. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Electrodeposited Cu2ZnSnSe4 thin film solar cell with 7% power conversion efficiency

High performance Cu₂ZnSnSe₄ (CZTSe) photovoltaic materials were synthesized by electrodeposition of metal stack precursors followed by selenization. A champion solar cell with 7.0% efficiency is demonstrated. This is the highest efficiency among all of the CZTSe solar cells prepared from electrodeposited metallic precursors reported to‐date. Device parameters are discussed from the perspective of material microstructure and composition in order to improve performance. In addition, a high performance electrodeposited CZTS (S only) solar cell was demonstrated and its device characteristics were compared against the CZTSe (Se only) cell. Using secondary ion mass spectrometry for the analysis of the chemical composition of the absorber layer, a higher concentration of oxygen in the electrodeposited absorber is thought to be the root cause of the lower performance of the electrodeposited CZTS or CZTSe solar cells with respect to a solar cell fabricated by evaporation. The grain boundary areas of Sn‐rich composition are thought to be responsible for the lower shunt resistance commonly observed in CZTSe devices. We measured the longest minority carrier lifetime of 18 ns among all reported kesterite devices. This work builds a good baseline for obtaining higher efficiency earth‐abundant solar cells, while it highlights electrodepositon as a low cost and feasible method for earth‐abundant thin film solar cell fabrication. Copyright © 2013 John Wiley & Sons, Ltd.     

Carbon nanotubes reinforced chitosan films: mechanical properties and cell response of a novel biomaterial for cardiovascular tissue engineering

Carbon nanotubes have been proposed as fillers to reinforce polymeric biomaterials for the strengthening of their structural integrity to achieve better biomechanical properties. In this study, a new polymeric composite material was introduced by incorporating various low concentrations of multiwalled carbon nanotubes (MWCNTs) into chitosan (CS), aiming at achieving a novel composite biomaterial with superior mechanical and biological properties compared to neat CS, in order to be used in cardiovascular tissue engineering applications. Both mechanical and biological characteristics in contact with the two relevant cell types (endothelial cells and vascular myofibroblasts) were studied. Regarding the mechanical behavior of MWCNT reinforced CS (MWCNT/CS), 5 and 10 % concentrations of MWCNTs enhanced the mechanical behavior of CS, with that of 5 % exhibiting a superior mechanical strength compared to 10 % concentration and neat CS. Regarding biological properties, MWCNT/CS best supported proliferation of endothelial and myofibroblast cells, MWCNTs and MWCNT/CS caused no apoptosis and were not toxic of the examined cell types. Conclusively, the new material could be suitable for tissue engineering (TE) and particularly for cardiovascular TE applications.     

Detachment strength of human osteoblasts cultured on hydroxyapatite with various surface roughness. Contribution of integrin subunits

Hydroxyapatite (HA) has been widely used as a bone substitute in dental, maxillofacial and orthopaedic surgery and as osteoconductive bone substitute or precoating of pedicle screws and cages in spine surgery. The aim of the present study was to investigate the osteoblastic adhesion strength on HA substrata with different surface topography and biochemistry (pre-adsorption of fibronectin) after blocking of specific integrin subunits with monoclonal antibodies. Stoichiometric HA was prepared by precipitation followed by ageing and characterized by SEM, EDX, powder XRD, Raman spectroscopy, TGA, and specific surface area analysis. Human bone marrow derived osteoblasts were cultured on HA disc-shaped substrata which were sintered and polished resulting in two surface roughness grades. For attachment evaluation, cells were incubated with monoclonal antibodies and seeded for 2 h on the substrata. Cell detachment strength was determined using a rotating disc device. Cell detachment strength was surface roughness, fibronectin preadsorption and intergin subunit sensitive.     

Deep learning for automatic segmentation of thigh and leg muscles

Objective

In this study we address the automatic segmentation of selected muscles of the thigh and leg through a supervised deep learning approach.

Material and methods

The application of quantitative imaging in neuromuscular diseases requires the availability of regions of interest (ROI) drawn on muscles to extract quantitative parameters. Up to now, manual drawing of ROIs has been considered the gold standard in clinical studies, with no clear and universally accepted standardized procedure for segmentation. Several automatic methods, based mainly on machine learning and deep learning algorithms, have recently been proposed to discriminate between skeletal muscle, bone, subcutaneous and intermuscular adipose tissue. We develop a supervised deep learning approach based on a unified framework for ROI segmentation.

Results

The proposed network generates segmentation maps with high accuracy, consisting in Dice Scores ranging from 0.89 to 0.95, with respect to “ground truth” manually segmented labelled images, also showing high average performance in both mild and severe cases of disease involvement (i.e. entity of fatty replacement).

Discussion

The presented results are promising and potentially translatable to different skeletal muscle groups and other MRI sequences with different contrast and resolution.

     

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

Objective

The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve.

Materials and methods

15 healthy subjects (M/F: 9/6; age: 21–62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison.

Results

There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68–0.7; inter-rater 0.70–0.72) and the related aT2* measures (intra-inter reader ICC 0.95–0.97; 0.66–0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo.

Discussion

Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.

     

Development of piezoelectric thick-film sensors to be embedded into adhesively bonded joints

Techniques have been developed for making a unique type of piezoelectric thick-film strain sensor in the form of a ‘piezoelectric adhesive’ to be embedded into a bonded joint. Lead zirconate titanate (PZT) powder is used as the active ingredient of the piezoelectric composite and epoxy resin as the matrix. The sensors have been fully characterised (i.e. type of piezoelectric powder, the surface area of the sensor, its thickness, weight fraction and the poling field) through an extensive testing programme in order to determine the optimum formulation for enhancing the sensitivity of the sensor. One of the main challenges was to effectively incorporate those sensors into the adhesive layer of a lap joint without greatly affecting the joint's mechanical properties. This application would allow the direct measurement of the stress field in a joint along the bond area, aiming at the optimisation of the adhesively bonded joint design as well as serving as an in-service structural health monitoring device. In the present work, the sensors were tested using the dynamic four-point bending test and preliminary results demonstrate the feasibility of this approach, achieving a satisfactory performance of the piezoelectric sensors applied on a metal substrate.