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

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

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

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

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

Study of the impact of tissue density heterogeneities on 3-dimensional abdominal dosimetry: comparison between dose kernel convolution and direct monte carlo methods.

Dose kernel convolution (DK) methods have been proposed to speed up absorbed dose calculations in molecular radionuclide therapy. Our aim was to evaluate the impact of tissue density heterogeneities (TDH) on dosimetry when using a DK method and to propose a simple density-correction method. METHODS: This study has been conducted on 3 clinical cases: case 1, non-Hodgkin lymphoma treated with (131)I-tositumomab; case 2, a neuroendocrine tumor treatment simulated with (177)Lu-peptides; and case 3, hepatocellular carcinoma treated with (90)Y-microspheres. Absorbed dose calculations were performed using a direct Monte Carlo approach accounting for TDH (3D-RD), and a DK approach (VoxelDose, or VD). For each individual voxel, the VD absorbed dose, D(VD), calculated assuming uniform density, was corrected for density, giving D(VDd). The average 3D-RD absorbed dose values, D(3DRD), were compared with D(VD) and D(VDd), using the relative difference Δ(VD/3DRD). At the voxel level, density-binned Δ(VD/3DRD) and Δ(VDd/3DRD) were plotted against ρ and fitted with a linear regression. RESULTS: The D(VD) calculations showed a good agreement with D(3DRD). Δ(VD/3DRD) was less than 3.5%, except for the tumor of case 1 (5.9%) and the renal cortex of case 2 (5.6%). At the voxel level, the Δ(VD/3DRD) range was 0%-14% for cases 1 and 2, and -3% to 7% for case 3. All 3 cases showed a linear relationship between voxel bin-averaged Δ(VD/3DRD) and density, ρ: case 1 (Δ = -0.56ρ + 0.62, R(2) = 0.93), case 2 (Δ = -0.91ρ + 0.96, R(2) = 0.99), and case 3 (Δ = -0.69ρ + 0.72, R(2) = 0.91). The density correction improved the agreement of the DK method with the Monte Carlo approach (Δ(VDd/3DRD) < 1.1%), but with a lesser extent for the tumor of case 1 (3.1%). At the voxel level, the Δ(VDd/3DRD) range decreased for the 3 clinical cases (case 1, -1% to 4%; case 2, -0.5% to 1.5%, and -1.5% to 2%). No more linear regression existed for cases 2 and 3, contrary to case 1 (Δ = 0.41ρ - 0.38, R(2) = 0.88) although the slope in case 1 was less pronounced. CONCLUSION: This study shows a small influence of TDH in the abdominal region for 3 representative clinical cases. A simple density-correction method was proposed and improved the comparison in the absorbed dose calculations when using our voxel S value implementation

Trafficking of High Avidity HER-2/neu-Specific T Cells into HER-2/neu-Expressing Tumors after Depletion of Effector/Memory-Like Regulatory T Cells

Cancer vaccines are designed to activate and enhance cancer-antigen-targeted T cells that are suppressed through multiple mechanisms of immune tolerance in cancer-bearing hosts. T regulatory cell (Treg) suppression of tumor-specific T cells is one barrier to effective immunization. A second mechanism is the deletion of high avidity tumor-specific T cells, which leaves a less effective low avidity tumor specific T cell repertoire available for activation by vaccines. Treg depleting agents including low dose cyclophosphamide (Cy) and antibodies that deplete CD25-expressing Tregs have been used with limited success to enhance the potency of tumor-specific vaccines. In addition, few studies have evaluated mechanisms that activate low avidity cancer antigen-specific T cells. Therefore, we developed high and low avidity HER-2/neu-specific TCR transgenic mouse colonies specific for the same HER-2/neu epitope to define the tolerance mechanisms that specifically affect high versus low avidity tumor-specific T cells.High and low avidity CD8(+) T cell receptor (TCR) transgenic mice specific for the breast cancer antigen HER-2/neu (neu) were developed to provide a purified source of naïve, tumor-specific T cells that can be used to study tolerance mechanisms. Adoptive transfer studies into tolerant FVB/N-derived HER-2/neu transgenic (neu-N) mice demonstrated that high avidity, but not low avidity, neu-specific T cells are inhibited by Tregs as the dominant tolerizing mechanism. High avidity T cells persisted, produced IFNγ, trafficked into tumors, and lysed tumors after adoptive transfer into mice treated with a neu-specific vaccine and low dose Cy to deplete Tregs. Analysis of Treg subsets revealed a Cy-sensitive CD4(+)Foxp3(+)CD25(low) tumor-seeking migratory phenotype, characteristic of effector/memory Tregs, and capable of high avidity T cell suppression.Depletion of CD25(low) Tregs allows activation of tumor-clearing high avidity T cells. Thus, the development of agents that specifically deplete Treg subsets should translate into more effective immunotherapies while avoiding autoimmunity

Under the influence::Using natural language in interactive storytelling

Interacting in natural language with virtual actors is an important aspect of the development of future Interactive Storytelling systems. We describe a paradigm for speech interfaces in interactive storytelling based on the notion of influence. In this paradigm, the user is mainly a spectator who is however able to interfere with the course of action by issuing advice to the characters. This is achieved by recognising corresponding speech acts and mapping them to the plans which implement characters' behaviours in the story. We discuss some examples based on a preliminary, yet fully implemented, prototype

Suboccipital craniotomy in the surgical treatment of Chiari I malformation

The object of this study was to present craniotomy for Chiari type I patients. Six patients with Chiari type I underwent suboccipital craniotomy. All patients showed clinical improvement, and none had any complications. Two patients had syringomyelia; it disappeared in entirety. We describe the procedure for posterior fossa decompression. Three-dimensional volumetric analysis using Vitrea workstation for postoperative posterior fossa volumes was calculated and was seen to have been increased on an average, from pre-operative (168 cc) to postoperative volume (192 cc). We thus conclude that suboccipital craniotomy results in resolution of the Chiari symptoms yet achieves effective expansion of posterior fossa