BACKGROUND: Contemporary biological observations have revealed a large variety of mechanisms acting during the expansion of a tumor. However, there are still many qualitative and quantitative aspects of the phenomenon that remain largely unknown. In this context, mathematical and computational modeling appears as an invaluable tool providing the means for conducting in silico experiments, which are cheaper and less tedious than real laboratory experiments. RESULTS: This paper aims at developing an extensible and computationally efficient framework for in silico modeling of tumor growth in a 3-dimensional, inhomogeneous and time-varying chemical environment. The resulting model consists of a set of mathematically derived and algorithmically defined operators, each one addressing the effects of a particular biological mechanism on the state of the system. These operators may be extended or re-adjusted, in case a different set of starting assumptions or a different simulation scenario needs to be considered. CONCLUSION: In silico modeling provides an alternative means for testing hypotheses and simulating scenarios for which exact biological knowledge remains elusive. However, finer tuning of pertinent methods presupposes qualitative and quantitative enrichment of available biological evidence. Validation in a strict sense would further require comprehensive, case-specific simulations and detailed comparisons with biomedical observations.

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Prophylactic cranial irradiation (PCI) is a standard treatment technique for small cell lung cancer patients. However, there is evidence that this technique may contribute to neurocognitive deficits. Therefore the study of anatomical and functional connectivity in patients undergoing PCI as well as their neurocognitive functionality, depending on the type of disease and the phase of treatment and time of clinical examination, is of considerable interest. In this context, we investigate whether there are any differentiations in brain function during resting state and task-related functional magnetic resonance imaging (fMRI) in patients with cancer before PCI compared to healthy subjects. During a finger tapping task, the brain regions that were activated bilaterally for both groups are consistent with previous studies. During rest, the Default Mode Network (DMN) was identified in both groups. The preliminary results presented herein are subject to further investigation with larger patient and control group.

Large biomolecules and proteins associated with brain functions and human diseases, as Alzheimer's disease, exhibit unique fingerprints in the THz spectrum. As a result, THz biomedical imaging with near-field probes is a promising solution for medical diagnosis and brain study. Ultimately, antennas with significantly enhanced performance are required for in-vivo THz biomedical applications. In this work, a THz rectangular patch antenna on a metamaterial substrate operating at 1 THz is presented. The metamaterial substrate based on split-ring resonators improves the antenna's gain and directivity. Finally, measurements at the microwave regime of a scaled version of the proposed antenna have been performed to experimentally verify the theoretically estimated metamaterial effect on the antenna performance.

Terahertz technology is considered a viable option for medical imaging, since many biological and chemical agents exhibit signatures in this spectral domain. Ultimately, large biomolecules and protein strands will be accessible, enabled by the coupling of THz science with near-field probes. In this paper, we present the recent advances of our research regarding a novel 2-D THz imaging system that it is intended to be used for imaging and characterization of tissue and biomolecule samples associated to brain functionality. Herein, we specifically focus on the emitting elements of the system, by studying two types of THz planar antennas for THz emission: a rectangular and a bow-tie patch antenna working at 1 THz. The aim and novelty of this work is to present an effective THz antenna with high gain and to this end we use left-handed materials for the substrate.

This paper presents the latest progress made concerning a hybrid diagnostic and therapeutic system able to provide focused microwave radiometric temperature and/or conductivity variation measurements and hyperthermia treatment. Previous experimental studies of our group have demonstrated the system performance and focusing properties in phantom as well as human experiments. The system is able to detect temperature and conductivity variations with frequency-dependent detection depth and spatial sensitivity. Numerous studies have also demonstrated the improvement of the system focusing properties attributed to the use of dielectric and left handed matching layers. In this study, similar experimental procedures are performed but this time using an anatomical head model as phantom aiming to achieve a more accurate modeling of the system's future real function. This way, another step is made toward the deeper understanding of the system's capabilities, with the view to further use it in experimental procedures with laboratory animals and human volunteers.

In this study, new aspects of our research regarding a novel hybrid system able to provide focused microwave radiometric temperature and/or conductivity measurements and hyperthermia treatment via microwave irradiation are presented. On one hand, it is examined whether the system is capable of sensing real-time progressive local variations of temperature and/or conductivity in customized phantom setups; on the other hand, the focusing attributes of the system are explored for different positions and types of phantoms used for hyperthermia in conjunction with dielectric matching layers surrounding the areas of interest. The main module of the system is an ellipsoidal cavity, which provides the appropriate focusing of the electromagnetic energy on the area of interest. The system has been used for the past few years in experiments with different configuration setups including phantom, animal, and human volunteer measurements yielding promising outcome. The present results show that the system is able to detect local concentrated gradual temperature and conductivity variations expressed as an increase of the output radiometric voltage. Moreover, when contactless focused hyperthermia is performed, the results show significant temperature increase at specific phantom areas. In this case, the effect of the dielectric matching layers placed around the phantoms is critical, thus resulting in the enhancement of the energy penetration depth.

This paper presents simulation results demonstrating the performance of OFDM system over vehicular ad-hoc networks, based on IEEE 802.11p specifications, employing turbo coding. The system is focused on vehicle safety applications using ad-hoc communication and networking. IEEE 802.11p defines modifications to IEEE 802.11 to enhance road transport and traffic applications. The standard is based on IEEE 802.11a and intends to support both public safety and licensed private operations over communication channels. The current contribution presents results of system performance evaluation of IEEE 802.11p turbo coding scheme and compares it to the already specified scheme. The turbo coding scheme achieves significant improvement to the performance compared to other techniques. The FEC system model with and without the turbo scheme is later implemented in a Field Programmable Gate Array (FPGA) from Xilinx using an Electronic System Level (ESL) methodology.

This work presents the performance analysis and optimization of the IEEE 802.11p Physical layer and the implementation of the forward error correction (FEC) coding chain on Xilinx FPGA hardware. A MATLAB simulation is carried out in order to analyze baseband processing of the transceiver. IEEE 802.11p wireless access in the vehicular environment defines modifications to IEEE 802.11 to support intelligent transportation systems applications. Performance analysis of physical layer model has been estimated into different propagation conditions (AWGN, Ricean and Rayleigh fading). Two different coding schemes and a different value of guard interval has been employing in the model in order to optimize its performance. The coding chain in the transmitter with and without the two coding schemes has been implemented in a FPGA from Xilinx using the System Generator tool-flow for fast prototyping.

Mathematical and computational tumor dynamics models can provide considerable insight into the relative importance and interdependence of related biological mechanisms. They may also suggest the existence of optimal treatment windows in the generic setting. Nevertheless, they cannot be translated into clinical practice unless they undergo a strict and thorough clinical validation and adaptation. In this context one of the major actions of the EC funded project ldquoAdvancing Clinico-Genomic Trials on Cancerrdquo (ACGT) is dedicated to the development of a patient specific four dimensional multiscale tumor model mimicking the nephroblastoma tumor response to chemotherapeutic agents according to the SIOP 2001/GPOH clinical trial. Combined administration of vincristine and dactinomycin is considered. The patient#x2019;s pseudoanonymized imaging, histopathological, molecular and clinical data are carefully exploited. The paper briefly outlines the basics of the model developed by the In Silico Oncology Group and particularly stresses the effect of stem/clonogenic, progenitor and differentiated tumor cells on the overall tumor dynamics. The need for matching the cell category transition rates to the cell category relative populations of free tumor growth for an already large solid tumor at the start of simulation has been clarified. A technique has been suggested and succesfully applied in order to ensure satisfaction of this condition. The concept of a nomogram matching the cell category transition rates to the cell category relative populations at the treatment baseline is introduced. Convergence issues are addressed and indicative numerical results are presented. Qualitative agreement of the modelpsilas behavior with the corresponding clinical trial experience supports its potential to constitute the basis for an optimization system within the clinical environment following completion of its clinical validation and optimization. In silico treatment experimentation in the patient individualized context is expected to constitute the primary application of the model.

In this work, a novel hybrid system able to provide focused microwave radiometric temperature and/or conductivity measurements and hyperthermia treatment via microwave irradiation is experimentally tested. The main module of the system is an ellipsoidal cavity, which provides the appropriate focusing of the electromagnetic energy on the area of interest. The system has been used the past few years in experiments with different configuration setups including phantom, animal and human volunteer measurements yielding promising outcome. New aspects of our research are presented in this paper regarding both radiometry and hyperthermia modules. On one hand, it is examined whether the system is capable of sensing real time progressive local variations of temperature and/or conductivity in customized phantom setups; on the other, the focusing attributes of the system are explored for different positions and types of phantoms used for hyperthermia. The results show that the system is able to detect local concentrated gradual temperature and conductivity variations expressed as an increase of the output radiometric voltage. When contactless focused hyperthermia is performed, the results show significant temperature increase at specific phantom areas. In this case, the effect of a dielectric matching layer placed around the phantoms has been also tested resulting in the enhancement of the energy penetration depth.

In this paper a new SAR data processing algorithm denoted with Extended Omega-K (EOK) is analytically presented and formulated. EOK algorithm combines the advantages of the high accurate focusing of the wavenumber domain algorithms with high precision motion compensation. The new EOK algorithm integrates a two-step range adaptive motion compensation correction in the general formulation of the wavenumber domain algorithm, leading to a new SAR processing scheme, which is much more robust concerning long synthetic apertures and squint angle than for example the chirp-scaling method. Additionally it offers the possibility of processing wideband low-frequency airborne SAR data up to near-wavelength resolution. The performance and the accuracy of the new EOK SAR data processing algorithm is demonstrated using simulated data.

The design and development of two novel dual-band coplanar waveguide (CPW)-fed slot antennas for broadband wireless applications is presented. The first antenna operates in GSM (1.7-1.9 GHz) and IEEE 802.11b (2.4-2.5 GHz WLAN) frequency bands, while the second antenna operates in the 802.11b (2.4-2.5 GHz) and 802.11b (5.1-5.9 GHz) frequency bands. These antennas are aimed to cover the gap in the multiband wireless applications domain. Simulation work has been performed using commercially available three-dimensional electromagnetic tools and prototypes have been built in order to explore the actual performance of these two antennas. Satisfactory agreement in simulation and experimental results is shown. These antennas can easily be attached on the backplane of PDAs, smartphones or notebooks, to meet users' needs for wireless connectivity in a small form factor.

The concept of in silica radiation oncology is clarified in this paper. A brief literature review points out the principal domains in which experimental, mathematical, and three-dimensional (3-D) computer simulation models of tumor growth and response to radiation therapy have been developed. Two paradigms of 3-D simulation models developed by our research group are concisely presented. The first one refers to the in vitro development and radiation response of a tumor spheroid whereas the second one refers to the fractionated radiation response of a clinical tumor in vivo based on the patient's imaging data. In each case, a description of the salient points of the corresponding algorithms and the visualization techniques used takes place. Specific applications of the models to experimental and clinical cases are described and the behavior of the models is two- and three-dimensionally visualized by using virtual reality techniques. Good qualitative agreement with experimental and clinical observations strengthens the applicability of the models to real situations. A protocol for further testing and adaptation is outlined. Therefore, an advanced integrated patient specific decision support and spatio-temporal treatment planning system is expected to emerge after the completion of the necessary experimental tests and clinical evaluation.

A simplified three-dimensional Monte Carlo simulation model of in vitro tumor growth and response to fractionated radiotherapeutic schemes is presented in this paper. The paper aims at both the optimization of radiotherapy and the provision of insight into the biological mechanisms involved in tumor development. The basics of the modeling philosophy of Duechting have been adopted and substantially extended. The main processes taken into account by the model are the transitions between the cell cycle phases, the diffusion of oxygen and glucose, and the cell survival probabilities following irradiation. Specific algorithms satisfactorily describing tumor expansion and shrinkage have been applied, whereas a novel approach to the modeling of the tumor response to irradiation has been proposed and implemented. High-performance computing systems in conjunction with Web technologies have coped with the particularly high computer memory and processing demands. A visualization system based on the MATLAB software package and the virtual-reality modeling language has been employed. Its utilization has led to a spectacular representation of both the external surface and the internal structure of the developing tumor. The simulation model has been applied to the special case of small cell lung carcinoma in vitro irradiated according to both the standard and accelerated fractionation schemes. A good qualitative agreement with laboratory experience has been observed in all cases. Accordingly, the hypothesis that advanced simulation models for the in silico testing of tumor irradiation schemes could substantially enhance the radiotherapy optimization process is further strengthened. Currently, our group is investigating extensions of the presented algorithms so that efficient descriptions of the corresponding clinical (in vivo) cases are achieved.

Long latency evoked potentials (EP's) are electrical potentials related to brain information processing mechanisms. In this paper, three-layered neurophysiologically based artificial neural network model is presented whose neurons obey to Dale's law. The first two layers of the network can memorize and recall sparsely coded patterns, oscillating at biologically plausible frequencies. Excitatory low-pass filtering synapses, from the second to the third layer, create evoked current dipoles, when the network retrieves memories related to stimuli. Based on psychophysiological indications, simulated intracranial dipoles are straightforwardly transformed into long latency EP components such as N100 and P300 that match laboratory-measured scalp EP's.

This paper describes innovative software for catheter localization and three-dimensional (3-D) reconstruction in stepping source brachytherapy applications. Patient information is a set of computed tomography (CT) slices scanned during the implantation of brachytherapy catheters. Catheter geometry and patient anatomy are exported for use with dose calculation software modules. The errors produced by the system are also encouragingly low. Time saving was achieved, in terms of other traditional reconstruction techniques. Various automated procedures, 3-D graphics and a user-friendly GUI, have contributed to providing a powerful, comprehensive software tool, directly useable in the clinical practice.