Adaptive Model-Based Visual Stabilization of Image Sequences Using Feedback

Visual stabilization proposed in this paper compensates changes of the scene caused by motion and deformation of an observed object. This is of high importance in computer-assisted beating heart surgery, where the views of the beating heart should be stabilized. The proposed model-based method defines visual stabilization as a transformation of the current image sequence to a stabilized image sequence. This transformation incorporates physical model of the observed object and model of the measurement process. In contrast to standard approaches, the quality of the visual stabilization is continuously evaluated and improved in two aspects. On the one hand, discretization errors are reduced. On the other hand, the parameters of the underlying models are adjusted. The performance of the proposed method is evaluated in an experiment with a pressure-regulated artificial heart. Compared with standard methods, the model-based method provides higher accuracy, which is additionally improved by a feedback mechanism

Simultaneous State and Parameter Estimation for Physics-Based Tracking of Heart Surface Motion

Most existing approaches for tracking of the beating heart motion assume known cardiac kinematics and material parameters. However, these assumptions are not realistic for application in beating heart surgery. In this paper, a novel probabilistic tracking approach based on a physical model of the heart surface is presented. In contrast to existing approaches, the physical information about heart kinematics and material properties is incorporated and considered in an estimation of the heart behavior. An additional advantage is that the time-dependencies and uncertainties of the heart parameters are efficiently handled by exploiting simultaneous state and parameter estimation. Furthermore, by decomposing the state into linear and nonlinear substructures, the computational complexity of the estimation problem is reduced. The experimental results demonstrate the high performance of the method proposed in this paper. The solution of the parameter identification problem allows a personalized physical model and opens up possibilities to apply the physics-based tracking of the heart surface motion in a clinical environment

Efficient Physics-Based Tracking of Heart Surface Motion for Beating Heart Surgery Robotic Systems

Purpose: Tracking of beating heart motion in a robotic surgery system is required for complex cardiovascular interventions. Methods: A heart surface motion tracking method is developed, including a stochastic physics-based heart surface model and an efficient reconstruction algorithm. The algorithm uses the constraints provided by the model that exploits the physical characteristics of the heart. The main advantage of the model is that it is more realistic than most standard heartmodels. Additionally, no explicit matching between the measurements and the model is required. The application of meshless methods significantly reduces the complexity of physics-based tracking. Results: Based on the stochastic physical model of the heart surface, this approach considers the motion of the intervention area and is robust to occlusions and reflections. The tracking algorithm is evaluated in simulations and experiments on an artificial heart. Providing higher accuracy than the standardmodel-based methods, it successfully copes with occlusions and provides high performance even when all measurements are not available. Conclusions: Combining the physical and stochastic description of the heart surface motion ensures physically correct and accurate prediction. Automatic initialization of the physics-based cardiac motion tracking enables system evaluation in a clinical environment

Visual Stabilization of Beating Heart Motion by Model-based Transformation of Image Sequences

In order to assist a surgeon by operating on a beating heart, visual stabilization makes the beating heart appear still to a surgeon by providing the current heart view as stationary and non-moving. In this way, the surgeon is not disturbed during an operation by a motion of the heart and can get an impression of performing conventional surgery. In contrast to existing methods for visual stabilization, the proposed approach involves a model-based transformation of image sequences provided by a camera system. This transformation incorporates the knowledge of physical characteristics of the heart in form of a mathematical model of the heart surface. Its main advantage is that the uncertainties of the model and measurements are considered. This occurs by estimating the parameters of the transformation. Furthermore, the quality of the visual stabilization is additionally improved by adapting the parameters of the underlying physical model. A performance of the proposed approach is evaluated in an experiment with a pressure-regulated artificial heart. In comparison to standard approaches, it provides superior results illustrating the high quality of the visual stabilization

Ignition and properties of RF capacitive discharge in acetylene

In the present work, we measured breakdown and extinction curves of radio-frequency discharge in acetylene as well as dependences of active current, power and gas pressure on the discharge burning time, and also optical emission spectra. It was found that in the region of low acetylene pressures (to the left of the minimum of the breakdown curve), the discharge can cover only a part of the electrode surface. Immediately after the ignition of the discharge, due to the intense deposition of the polymer film and the formation of dust particles in the plasma volume, the gas pressure decreases sharply (by the factor of 2-5), while the active current and power increase and then reach saturation. In the discharge with intense polymerization, the lines of atomic and molecular hydrogen dominate in the emission spectrum of the discharge. The film deposited on the surface of the electrodes and the tube walls, as well as the dust particles formed, are amorphous, the maximum peak of XRD spectrum is observed at 2θ = 18°, and the light absorption by the deposited films is highest at 440 nm wavelength.Виміряні криві запалювання та згасання, залежності активних струму, потужності та тиску газу від часу горіння розряду, а також спектри випромінювання високочастотного розряду в ацетилені. Отримано, що в області низьких значень тиску ацетилену (зліва від мінімуму кривої запалювання) розряд може покривати тільки частину поверхні електродів. Відразу після запалювання розряду через інтенсивне осадження полімерної плівки і утворення пилових частинок у плазмовому об’ємі різко (в 2-5 разів) зменшується тиск газу, а активні струм і потужність зростають і потім виходять на насичення. У процесі інтенсивної полімеризації в спектрі випромінювання розряду домінують лінії атомарного і молекулярного водню. Плівка, що осаджується на поверхню електродів і стінок трубки, а також пилові частинки, що формуються, є аморфними, для них максимальне дифракційне розсіювання рентгенівських променів спостерігається при 2θ = 18°, а поглинання видимого світла є найбільшим при 440 нм.Измерены кривые зажигания и погасания, зависимости активных тока, мощности и давления газа от времени горения разряда, а также спектры излучения высокочастотного разряда в ацетилене. Получено, что в области низких давлений ацетилена (слева от минимума кривой зажигания) разряд может покрывать только часть поверхности электродов. Сразу после зажигания разряда из-за интенсивного осаждения полимерной пленки и образования пылевых частиц в плазменном объеме резко (в 2-5 раз) уменьшается давление газа, а активные ток и мощность возрастают и затем выходят на насыщение. В процессе интенсивной полимеризации в спектре излучения разряда доминируют линии атомарного и молекулярного водорода. Осаждаемая на поверхность электродов и стенок трубки пленка, а также формирующиеся пылевые частицы являются аморфными, для них максимальное дифракционное рассеяние рентгеновских лучей наблюдается при 2θ = 18°, а поглощение видимого света является наибольшим при 440 нм

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions

Математическое моделирование огибающей реверберационного процесса с помощью алгоритма Шредера

Стаття присвячена дослідженню алгоритму оберненого інтегрування (метод Шредера) який використовується при побудові огинаючої ревербераційного процесу. Ґрунтуючись на різні методи вимірювання була розроблена програма для моделювання процесу реверберації в закритому приміщенні та проведений модельний експеримент. Аналіз отриманих результатів показав, що огинаюча ревербераційного процесу, побудованого за методом зворотного інтегрування, має мінімальне середньоквадратичне відхилення від заданого експериментального спадання, а це означає, що використовуючи його можна отримати більш точне значення часу реверберації.The article is devoted to research of reverse integration algorithm (Schroder’s method) which is used for the construction of reverberation prosess circumflex. Based on the different methods of measuring, the program for reverberation process design in the closed room was developed and a model experiment was carried out. The analysis of the results showed that reverberation process circumflex built by reverse integration method has minimum standard deviation from the set experimental downturn, and it means that it is possible to get more exact meaning of reverberation time using this program.Статья посвящена исследованию алгоритма обратного интегрирования (метод Шредера) который используется при построении огибающей реверберационного процесса. Основываясь на различные методы измерения была разработана программа для моделирования процесса реверберации в закрытом помещении и проведен модельный эксперимент. Анализ полученных результатов показал, что огибающая реверберационного процесса, построенного за методом обратного интегрирования, имеет минимальное среднеквадратическое отклонение от заданного экспериментального спада, а это значит, что используя его можно получить более точное значение времени реверберации