Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title> <jats:p> <jats:italic>Purpose</jats:italic>: In optic nerve radiotherapy, vital organs are very close to the target volume, they are highly sensitive to radiation and have low dose tolerance. In this regard, evaluating dose fall-off steepness around the target volume is required to assess various intensity-modulated radiation therapy (IMRT) plans in the treatment of the optic nerve sheath meningioma (ONSM) patients. <jats:italic>Materials and Methods</jats:italic>: Thirteen ONSM patients were analyzed with three IMRT techniques, including three (IMRT-3F), five (IMRT-5F), and seven fields (IMRT-7F). These plans were studied using D<jats:sub>mean</jats:sub>, D<jats:sub>max</jats:sub>, D<jats:sub>2%</jats:sub>, D<jats:sub>98%</jats:sub>, V<jats:sub>100%</jats:sub>, uniformity index (UI), homogeneity index (HI), conformity index (CI), and specifically the dose gradient indices (DGIs). <jats:italic>Results</jats:italic>: The values of D<jats:sub>max</jats:sub> and D<jats:sub>mean</jats:sub> for IMRT-3F, IMRT-5F and IMRT-7F were (5637.42 ± 57.08, 5322.84 ± 83.86), (5670.51 ± 67.87, 5383.00 ± 58.45), and (5692.99 ± 31.65, 5405.72 ± 51.73), respectively, which were increased with increment in the number of IMRT fields from 3 to 7. The UI and HI indices were significantly different between IMRT-3F and IMRT-7F (p = 0.010 and p = 0.005, respectively), and CI was close to the ideal value (0.99 ± 0.01) in IMRT-7F. The significant findings of the dose gradient indices represented smaller values in IMRT-7F, which led to a faster dose fall-off, particularly at the 70%-85% isodose levels around the target. <jats:italic>Conclusion</jats:italic>: Increasing the number of radiation fields in IMRT treatment plans of ONSM patients had a considerable difference in both the dosimetric parameters of the target volume and at-risk organs, as well as the dose gradient indices. Overall, IMRT-7F could be considered as a preferred technique in the treatment of this meningioma.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In this study, poly(2-hydroxyethyl methacrylate) [p(HEMA)] based hydrogels responsive to the pH, temperature and magnetic field were synthesized. The surface properties of p(HEMA) were improved by designing the stimuli-responsive hydrogels made of MAGA, NIPAAm and methacrylate-decorated magnetite nanoparticles as a function of pH-, thermo- and magnetic responsive cell culture surfaces. These materials were then modified an abundant extracellular matrix component, type I collagen, which has been considered as a biorecognition element to increase the applicability of hydrogels to cell viability. Based on results from scanning electron microscopy (SEM) and thermal gravimetric analysis (TGA), stimuli-responsive hydrogel demonstrated improved non-porous structures and thermal stability with a high degree of cross-linking. Mechanical analyses of the hydrogels also showed that stimuli-responsive hydrogels are more elastomeric due to the polymeric chains and heterogeneous amorphous segments compared to plain hydrogels. Furthermore, surface modification of hydrogels with collagen provided better biocompatibility, which was confirmed with L929 fibroblast cell adhesion. Produced stimuli-responsive hydrogels modulated cellular viability by changing pH and magnetic field.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>In long-term continuous driving, driving fatigue is the main cause of traffic accidents. Therefore, accurate and rapid detection of driver mental fatigue is of great significance to traffic safety. In our study, the electroencephalogram (EEG) signals of subjects were preprocessed to remove interference signals. The Butterworth band-pass filter is used to extract the EEG signals of <jats:italic>α</jats:italic> and <jats:italic>β</jats:italic> rhythms, and then the basic scale entropy of <jats:italic>α</jats:italic> and <jats:italic>β</jats:italic> rhythms is used as driving fatigue characteristics. In addition, combined with the fast multiple autoregressive (MVAR) model and phase slope index (PSI), short-term data is used to accurately estimate the effective connectivity of EEG signals between different channels, and analyzed the causality flow direction in the left and right prefrontal regions of drivers at different driving stages. Further comprehensive analysis of the driver’s driving fatigue state in the continuous driving phase. Finally, the correlation coefficient value between the parameter pairs (basic scale entropy, clustering coefficient, global efficiency) is calculated. The results showed that the causality flow outflow degree of prefrontal lobe decreased during the transition from sober driving state to tired driving state. The left and right prefrontal lobes were the source of causality in sober driving state, and gradually became the target of causality with the occurrence of driving fatigue. The results showed that when transitioning from a waking state to a fatigued driving state, the causal flow direction out-degree value of the prefrontal cortex on a declining curve, and the left and right prefrontal cortex exhibited the causal source in the awake driving state, which gradually changed into the causal target along with the occurrence of driving fatigue. The three parameters of basic scale entropy, clustering coefficient and global efficiency are used as driving fatigue characteristics, and every two parameters have strong correlation. It shows that the combination of basic scale entropy and MVAR-PSI method can effectively detect the driver’s long-term driving fatigue state in continuous driving mode.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> <jats:italic>Purpose.</jats:italic> C-arm linac-based radiotherapy has seen a recent interest in 4<jats:italic>π</jats:italic> methods of delivery using simultaneous rotations of couch and gantry to reduce doses to organs-at-risk (OARs) and increase dose compactness. While many methods use heuristics to generate trajectories that avoid OARs, combined with arbitrary trajectory restrictions to prevent oversampling, a quantity has not yet been developed to succinctly compare sampling of the 4<jats:italic>π</jats:italic> space for candidate trajectories as a surrogate for dosimetric compactness. <jats:italic>Methods.</jats:italic> Evenly spaced sampling points were distributed across a 4<jats:italic>π</jats:italic> sphere centred on isocentre. A metric, mean arc distance (MAD), was defined that quantifies the average arc distance between all sampling points and their nearest field in a radiotherapy trajectory. The relationship between isodose volume and MAD was examined in 2,047 plans: 900 unique trajectories of fixed port DCA plans, 900 unique trajectories of contiguous field DCA plans, 192 VMAT plans (eight volumes in four locations, each with six trajectories) in matRad with 5 VMAT plans repeated for validation in a clinical planning system, and 10 clinical VMAT cases replanned with five trajectories in a clinical treatment planning system. <jats:italic>Results.</jats:italic> All isodose volumes greater than 10% of the prescription dose decreased with decreasing MAD in all comparisons. In the range of 10% to 100% of the prescription dose, the rate of isodose volume decrease was exponential as a function of MAD in all comparisons. Reduction of absolute isodose volume is seen with increased 4<jats:italic>π</jats:italic> sampling, with larger target volumes exhibiting larger absolute reductions. Very low isodoses (0% to 10% of prescription) increased with decreasing MAD. <jats:italic>Conclusions.</jats:italic> MAD is a 4<jats:italic>π</jats:italic> sampling quantity useful in quantifying the decrease of isodose volume, relevant for sparing normal tissues. By quantifying this feature, candidate dynamic trajectories can be efficiently compared for 4<jats:italic>π</jats:italic> sampling. This quantity is explored here for single target cranial radiotherapy but may have applications to other radiotherapy treatment sites.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Cardiac arrhythmias represent about 50% of the cardiovascular diseases which are the first cause of mortality in the world. Implantable medical devices play a major role for treating these arrhythmias. Nevertheless the leads induce an unwanted biological phenomenon called fibrosis. This phenomenon begins at a cellular level and is effective at a macroscopic scale causing tissue remodelling with a local modification of the active cardiac tissue. Fibrosis mechanism is complex but at the cellular level, it mainly consists in cardiac fibroblasts activation and differentiation into myofibroblasts. We developed a simplified <jats:italic>in vitro</jats:italic> model of cardiac fibrosis, with human cardiac fibroblasts whom differentiation into myofibroblasts was promoted with TGF-<jats:italic>β</jats:italic>1. Our study addresses an unreported impedance-based method for real-time monitoring of <jats:italic>in vitro</jats:italic> cardiac fibrosis. The objective was to study whether the differentiation of cardiac fibroblasts in myofibroblasts had a specific signature on the cell index, an impedance-based feature measured by the xCELLigence system. Primary human cardiac fibroblasts were cultured along 6 days, with or without laminin coating, to study the role of this adhesion protein in cultures long-term maintenance. The cultures were characterized in the presence or absence of TGF-<jats:italic>β</jats:italic>1 and we obtained a significant cell index signature specific to the human cardiac fibroblasts differentiation.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Electro-spinnable polymeric materials can easily form two-dimensional (2D) nanofibrous scaffolds improving biochemical functionalities specially in the area of skin wound healing and nanomedicine, but it has been hard to achieve this on a highly mechanically stable biopolymer, Poly ether ether ketone (PEEK), due to its intrinsic hydrophobicity and chemical inertness. Herein, we demonstrated a novel nanomedicine healing system consisting of sulphonated poly ether ether ketone combined with <jats:italic>resveratrol</jats:italic> (SPEEK + RSV), which could act as an effective 2D nano bio-material <jats:italic>in vitro</jats:italic> and <jats:italic>in vivo</jats:italic>, without observable cytotoxicity. The fabricated nanocomposites exhibited enriched skin cell proliferation and adhesion as confirmed from the results of MTT, cell adhesion and live-dead assay. Results of SEM analysis showed a uniform nano-sized distribution with adequate pore size and porosity % facilitating a desired breathable environment at the wound site. The results of FT-IR, tensile studies and TGA analyses confirmed the presence of appropriate bonds and improved mechanical stability of the <jats:italic>RSV</jats:italic> incorporated nanofibrous scaffold. Results of anti-microbial analysis portrayed good potentiality of the fabricated nanofibers in treating wounds colonized with bacterial infections. Controlled drug release of resveratrol established the bio-compatibility of the nanofibers in skin wound regeneration. <jats:italic>In vivo</jats:italic> analysis assessed in female Wistar rats enabled complete wound closure with 100% wound contraction within 16 days. Results of histopathology analysis through H-E and MT staining presented the re-surfing of the wound environment with regeneration of epithelium, granulation tissue and collagen. Thus, the fabricated 2D nanofibrous scaffold incorporated with pharmaceutical RSV bio-medicine perceptively mimicked skin ECM convincingly aiding the progression of skin wound regeneration mechanism.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Radiation can be visualized using a scintillator and a digital camera. If the amount of light emitted by the scintillator increases with dose, the dose estimation can be obtained from the amount of light emitted. In this study, the basic performance of the scintillator and digital camera system was evaluated by measuring computed tomography dose index (CTDI). A circular plastic scintillator plate was sandwiched between polymethyl methacrylate (PMMA) phantoms, and x-rays were irradiated to them while rotating the x-ray tube to confirm changes in light emission. In addition, CTDI was estimated from the amount of light emitted by the scintillator during the helical scan and compared with the value measured from dosimeter. The scintillator emitted light while changing its distribution according to the movement of the x-ray tube. The measured CTDI<jats:sub>vol</jats:sub> was 33.20 mGy, the CTDI<jats:sub>vol</jats:sub> estimated from the scintillation light was approximately 46 mGy, which was 40% larger. In particular, when the scintillator was directly irradiated, the dose was overestimated compared with the value measured from the dosimeter. This overestimation can be because of the reproducibility of the position and the difference between the sensitivity of the scintillator to detect light emission and the sensitivity of the dosimeter, and the non-uniformity of position sensitivity due to the wide-angle lens.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Segmentation of bone regions allows for enhanced diagnostics, disease characterisation and treatment monitoring in CT imaging. In contrast enhanced whole-body scans accurate automatic segmentation is particularly difficult as low dose whole body protocols reduce image quality and make contrast enhanced regions more difficult to separate when relying on differences in pixel intensities. This paper outlines a U-net architecture with novel preprocessing techniques, based on the windowing of training data and the modification of sigmoid activation threshold selection to successfully segment bone-bone marrow regions from low dose contrast enhanced whole-body CT scans. The proposed method achieved mean Dice coefficients of 0.979 ± 0.02, 0.965 ± 0.03, and 0.934 ± 0.06 on two internal datasets and one external test dataset respectively. We have demonstrated that appropriate preprocessing is important for differentiating between bone and contrast dye, and that excellent results can be achieved with limited data.</jats:p>

<jats:title>Abstract</jats:title> <jats:p> <jats:italic>Objective.</jats:italic> In this paper we propose and investigate a new detector with multiple strip detector arrays (SDA) for monitoring MLC shaped x-ray beams for radiotherapy treatment. <jats:italic>Approach.</jats:italic> Each SDA measures 1D dose profiles equivalent to dose projections. The goal of such a detector is to determine individual MLC leaf positions as well as the Monitor Units (MU) per MLC segment during radiotherapy. In the present work we investigate an optimal SDA detector configuration and reconstruction algorithm. We determine the accuracy of SDA for different treatment sites (spine, pelvis, retroperitoneum, prostate, brain SRT, SRS, lung and head and neck). We perform a simulation study accounting for different type of MLC leaf positional errors: random MLC leaf, systematic for the whole leaf bank and systematic for an individual leaf. In a similar fashion, we also account for errors in Monitor Units per segment. <jats:italic>Main results.</jats:italic> We demonstrate that for a broad range of IMRT treatment plans a robust reconstruction of errors is achievable with only 3 projections (3 sets of SDA oriented at at 0°, 45° and 135°). The SDA is capable of capturing both systematic errors in leaf banks and individual leaves as well as random errors sufficient for practical clinical purposes. <jats:italic>Significance.</jats:italic> These features of the SDA detector makes it suitable for real-time Quality Control of MLC collimated linac output.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Shear wave elastography (SWE) is a promising technique for characterizing carotid plaques and assessing local arterial stiffness. The mechanical stress to which the tissue is subjected during SWE using acoustic radiation force (ARF), leading to strain at a certain strain rate, is still relatively unknown. Because SWE is increasingly used for arterial applications where the mechanical stress could potentially lead to significant consequences, it is important to understand the risks of SWE-induced strain and strain rate. The aim of this study was to investigate the safety of SWE in terms of induced arterial strain and strain rate <jats:italic>ex-vivo</jats:italic> and in a human carotid artery <jats:italic>in-vivo</jats:italic>. SWE was performed on six porcine aortae as a model of the human carotid artery using different combinations of ARF push parameters (push voltage: 60/90 V, aperture width: f/1.0/1.5, push length: 100/150/200 <jats:italic>μ</jats:italic>s) and distance to push position. The largest induced strain and strain rate were 1.46% and 54 s<jats:sup>−1</jats:sup> (90 V, f/1.0, 200 <jats:italic>μ</jats:italic>s), respectively. Moreover, the SWE-induced strains and strain rates increased with increasing push voltage, aperture, push length, and decreasing distance between the region of interest and the push. In the human carotid artery, the SWE-induced maximum strain was 0.06% and the maximum strain rate was 1.58 s<jats:sup>−1</jats:sup>, compared with the maximum absolute strain and strain rate of 12.61% and 5.12 s<jats:sup>−1</jats:sup>, respectively, induced by blood pressure variations in the cardiac cycle. Our results indicate that <jats:italic>ex-vivo</jats:italic> arterial SWE does not expose the artery to higher strain rate than normal blood pressure variations, and to strain one order of magnitude higher than normal blood pressure variations, at the push settings and distances from the region of interest used in this study.</jats:p>