A novel 2D/3D transformation for radiosurgery of ocular tumors: computer simulation and phantom validation

Noninvasive stereotactic radiosurgery with the Cyberknife system has been seen as a promising treatment platform for ocular tumors in clinical practice. However, due to the unpredictable eye movement during treatment, 6D skull tracking cannot account for random ocular tumor positions and therefore compromise treatment delivery precision. A real-time ocular tumor tracking system is highly desirable.We designed a novel “pupil tracking” approach that uses a derived 2D/3D transformation to relate the pupil’s 2D coordinate captured by a video camera in the image plane with the tumor’s 3D location in the CT space. To simulate and demonstrate the process of the 2D/3D transformation, a computer graphical model was created by using an interactive interface to mimic both tumor (size and location inside the eyeball) and eyeball (movement parameters). A mechanical phantom was also fabricated to validate the approach.Experimental data from computer simulation and phantom validation under the CT simulator were obtained. For eight testing points in the validation experiment by the mechanical phantom, the maximum root-sum-squared error (RSSE) of three coordinates (X, Y, Z) is less than 0.70 mm and the mean-squared error is 0.44 mm.Error analysis indicates that this pupil tracking technique has a potential application for radiosurgery of ocular tumors by the Cyberknife system

Measuring Emotion in Parliamentary Debates with Automated Textual Analysis

<div><p>An impressive breadth of interdisciplinary research suggests that emotions have an influence on human behavior. Nonetheless, we still know very little about the emotional states of those actors whose daily decisions have a lasting impact on our societies: politicians in parliament. We address this question by making use of methods of natural language processing and a digitized corpus of text data spanning a century of parliamentary debates in the United Kingdom. We use this approach to examine changes in aggregate levels of emotional polarity in the British parliament, and to test a hypothesis about the emotional response of politicians to economic recessions. Our findings suggest that, contrary to popular belief, the mood of politicians has become more positive during the past decades, and that variations in emotional polarity can be predicted by the state of the national economy.</p></div

A mechanical eyeball phantom for uveal melanoma radiosurgery by cyberknife

A treatment option for uveal melanoma has been investigated using the Cyberknife system, due to its advantage of real-time image guidance during therapy. However, unpredictable eyeball movement imposes challenges to the state-of-art technology. As a solution, we derived a 2D/3D transformation algorithm that is based on the pupil’s 2D coordinates captured by an optical tracking system to predict the tumor’s 3D positions in real-time. In order to validate our developed algorithm and other methods, a mechanical phantom that can simulate the eyeball’s movement is highly desirable.We designed a mechanical phantom that consists of a camera module, an eyeball module with an embedded “tumor", an eyeball holder module, and an eyeball moving module. All materials are made with acrylic or nylon plastics with the exception of the linear motion stages and the camera.In the calibration procedure, the phantom is scanned using a CT scanner. By using the recorded pupil’s coordinates and extracted tumor coordinates, the 2D/3D transformation model yields 0.39 ± 0.09 mm root-sum-squared error for five calibration positions between the actual 3D coordinates and the predicted coordinates. In the validation procedure, the eyeball is rotated to 11 different positions through the mechanical phantom. The 2D/3D transformation model yields 0.58 ± 0.27 mm root-sum-squared error for these positions between the Cyberknife-identified 3D coordinates and the predicted coordinates. The eyeball’s position can be controlled within millimeter accuracy.The designed mechanical phantom is suitable for validating image-guided radiosurgery methods. Further dynamic evaluations can confirm these methods for clinical applications