Underdetermined source separation using a sparse STFT framework and weighted laplacian directional modelling

The instantaneous underdetermined audio source separation problem of K-sensors, L-sources mixing scenario (where K < L) has been addressed by many different approaches, provided the sources remain quite distinct in the virtual positioning space spanned by the sensors. This problem can be tackled as a directional clustering problem along the source position angles in the mixture. The use of Generalised Directional Laplacian Densities (DLD) in the MDCT domain for underdetermined source separation has been proposed before. Here, we derive weighted mixtures of DLDs in a sparser representation of the data in the STFT domain to perform separation. The proposed approach yields improved results compared to our previous offering and compares favourably with the state-of-the-art.Comment: EUSIPCO 2016, Budapest, Hungar

Προσομοιώσεις μοριακής δυναμικής για τη μελέτη της μηχανικής συμπεριφοράς του γραφένιου υπό θλίψη

Εθνικό Μετσόβιο Πολυτεχνείο--Μεταπτυχιακή Εργασία. Διεπιστημονικό-Διατμηματικό Πρόγραμμα Μεταπτυχιακών Σπουδών (Δ.Π.Μ.Σ.) “Επιστήμη και Τεχνολογία Υλικών

Therapeutic Applications of Monte Carlo Calculations in Nuclear Medicine

This book examines the applications of Monte Carlo (MC) calculations in therapeutic nuclear medicine, from basic principles to computer implementations of software packages and their applications in radiation dosimetry and treatment planning. It is written for nuclear medicine physicists and physicians as well as radiation oncologists, and can serve as a supplementary text for medical imaging, radiation dosimetry and nuclear engineering graduate courses in science, medical and engineering faculties. With chapters is written by recognised authorities in that particular field, the book covers the entire range of MC applications in therapeutic medical and health physics, from its use in imaging prior to therapy to dose distribution modelling targeted radiotherapy. The contributions discuss the fundamental concepts of radiation dosimetry, radiobiological aspects of targeted radionuclide therapy and the various components and steps required for implementing a dose calculation and treatment planning methodology in radioimmunotherapy. Some computer programmes (for example MIRDOSE, MABDOS, 3D-ID) are described and illustrated with some useful features and clinical applications. Other potential applications of MC techniques are also discussed together with computing aspects of radiation transport calculations Key Features - Contributions from leading experts in their field - Several introductory chapters to introduce the Monte Carlo method and nuclear medical imaging techniques as well as radiation biology concepts to allow a better understanding. - Many chapters in the book summarise scientific developments in the last couple of decades and others deal with completely new techniques fully developed in recent years. Readership Medical and health physicists, computationa

Perspective rectification of integral images produced using arrays of circular lenses

There are many different three-dimensional (3D) techniques to capture and deliver autostereoscopic 3D content. A promising technique that provides two-dimensional parallax as well as high-quality, full-color 3D content is integral imaging (InI). Misalignments between the lens arrays (LAs) and the camera charged coupled device, however, introduce geometric distortions in the acquired image that propagate through the different image processing stages and deteriorate the 3D effect. Here, we propose a method to accurately rectify the perspective distortion of integral images (InIms) generated using circular lenses. Using an edge-linking approach, we extracted elliptically shaped contours of elemental images in the perspectively distorted InIm. To calculate the rectification matrix, we used the images of the circular points. Subsequently, we applied a triangulation scheme followed by a statistical approach to accurately estimate the grid structure of the LA. Finally, we provided experimental results over a wide range of InIms to evaluate the robustness and accuracy of the proposed method using objective metrics

Perspective rectification of integral images produced using hexagonal lens arrays

Nowadays a plethora of three-dimensional (3D) systems claim users' increasing preference for delivering 3D content. In recent years an increasing number of systems utilize autostereoscopic techniques and hence provide glasses free viewing and adequate resolutions in full color. In addition certain autostereoscopic techniques like Integral Imaging provide two-dimensional (2D) parallax and further increase anticipation for high fidelity 3D content viewing to professional and home users. In this paper we extend the results of previous research to provide perspective distortion rectification for Integral Images generated using hexagonal instead of square lenses. In the proposed method we demonstrate the utilization of a fundamental property of distorted coplanar hexagonal lattices in the image rectification framework that improve the rectification accuracy and robustness. Finally we provide experimental results over a number of images to evaluate the accuracy of the method using objective metrics

Grid reconstruction and skew angle estimation in integral images produced using circular microlenses

Nowadays a number of different three-dimensional (3D) systems compete in the field of capturing and delivering autostereoscopic (ASt) 3D content. Integral Imaging (InI) is a promising ASt technique that provides both horizontal and vertical parallax as well as high quality realistic 3D content. In this work we propose an InI preprocessing method for identification and accurate segmentation of the grid structure in Integral Images (InIms) generated using lens arrays (LAs) containing circular lenses. In the proposed method we utilize the gradient augmented circular hough transform to accurately detect circular regions in the acquired integral image (InIm). Subsequently by using a triangulation scheme followed by a statistical approach we accurately estimate the grid line structure of the utilized LA. This results in the accurate segmentation of the circular shaped elemental images (EIs) contained in the InIm, a process vital for the effectiveness of the InI methodology. We provide experimental results over artificial as well as optically acquired InIms to evaluate the accuracy of the method using objective metrics

Robust integral image rectification framework using perspective transformation supported by statistical line segment clustering

In most integral image analysis and processing tasks, accurate knowledge of the internal image structure is required. In this paper we present a robust framework for the accurate rectification of perspectively distorted integral images based on multiple line segment detection. The use of multiple line segments increases the overall fault tolerance of our framework providing strong statistical support for the rectification process. The proposed framework is used for the automatic rectification, metric correction, and rotation of distorted integral images. The performance of our framework is assessed over a number of integral images with varying scene complexity and noise levels

Redefining relative biological effectiveness in the context of the EQDX formalism: implications for alpha-particle emitter therapy.

Alpha-particle radiopharmaceutical therapy (αRPT) is currently enjoying increasing attention as a viable alternative to chemotherapy for targeting of disseminated micrometastatic disease. In theory, αRPT can be personalized through pre-therapeutic imaging and dosimetry. However, in practice, given the particularities of α-particle emissions, a dosimetric methodology that accurately predicts the thresholds for organ toxicity has not been reported. This is in part due to the fact that the biological effects caused by α-particle radiation differ markedly from the effects caused by traditional external beam (photon or electron) radiation or β-particle emitting radiopharmaceuticals. The concept of relative biological effectiveness (RBE) is used to quantify the ratio of absorbed doses required to achieve a given biological response with alpha particles versus a reference radiation (typically a beta emitter or external beam radiation). However, as conventionally defined, the RBE varies as a function of absorbed dose and therefore a single RBE value is limited in its utility because it cannot be used to predict response over a wide range of absorbed doses. Therefore, efforts are underway to standardize bioeffect modeling for different fractionation schemes and dose rates for both nuclear medicine and external beam radiotherapy. Given the preponderant use of external beams of radiation compared to nuclear medicine in cancer therapy, the more clinically relevant quantity, the 2 Gy equieffective dose, EQD2(α/β), has recently been proposed by the ICRU. In concert with EQD2(α/β), we introduce a new, redefined RBE quantity, named RBE2(α/β), as the ratio of the two linear coefficients that characterize the α particle absorbed dose-response curve and the low-LET megavoltage photon 2 Gy fraction equieffective dose-response curve. The theoretical framework for the proposed new formalism is presented along with its application to experimental data obtained from irradiation of a breast cancer cell line. Radiobiological parameters are obtained using the linear quadratic model to fit cell survival data for MDA-MB-231 human breast cancer cells that were irradiated with either α particles or a single fraction of low-LET (137)Cs γ rays. From these, the linear coefficient for both the biologically effective dose (BED) and the EQD2(α/β) response lines were derived for fractionated irradiation. The standard RBE calculation, using the traditional single fraction reference radiation, gave RBE values that ranged from 2.4 for a surviving fraction of 0.82-6.0 for a surviving fraction of 0.02, while the dose-independent RBE2(4.6) value was 4.5 for all surviving fraction values. Furthermore, bioeffect modeling with RBE2(α/β) and EQD2(α/β) demonstrated the capacity to predict the surviving fraction of cells irradiated with acute and fractionated low-LET radiation, α particles and chronic exponentially decreasing dose rates of low-LET radiation. RBE2(α/β) is independent of absorbed dose for α-particle emitters and it provides a more logical framework for data reporting and conversion to equieffective dose than the conventional dose-dependent definition of RBE. Moreover, it provides a much needed foundation for the ongoing development of an α-particle dosimetry paradigm and will facilitate the use of tolerance dose data available from external beam radiation therapy, thereby helping to develop αRPT as a single modality as well as for combination therapies