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Publications (34)
Purpose:
In coronary angiography, the condition of myocardial blood supply is assessed by analyzing 2-D X-ray projections of contrasted coronary arteries. This is done using a flexible C-arm system. Due to the X-ray immanent dimensionality reduction projecting the 3-D scene onto a 2-D image, the viewpoint is critical to guarantee an appropriate vi...
We improve data extrapolation for truncated computed tomography (CT) projections by using Helgason-Ludwig (HL) consistency conditions that mathematically describe the overlap of information between projections. First, we theoretically derive a 2D Fourier representation of the HL consistency conditions from their original formulation (projection mom...
In this paper, we propose a multi-sensor super-resolution framework for hybrid imaging to super-resolve data from one modality by taking advantage of additional guidance images of a complementary modality. This concept is applied to hybrid 3-D range imaging in image-guided surgery, where high-quality photometric data is exploited to enhance range i...
Volume-of-interest (VOI) C-arm computed tomography (CT) imaging is a promising approach to acquire anatomical information in a pre-defined target volume at low dose, using both axial and trans-axial collimation. However, also the region outside the target volume, below referred to as peripheral region (PR), could contain some valuable information f...
In hybrid 3D endoscopy, range data is used to augment photometric information for minimally invasive surgery. As range sensors suffer from a rough spatial resolution and a low signal-to-noise ratio, subpixel motion between multiple range images is used as a cue for superresolution to obtain reliable range data. Unfortunately, this method is sensiti...
It is known that a reduction of the field-of-view in 3-D X-ray imaging is proportional to a reduction in radiation dose. The resulting truncation, however, is incompatible with conventional reconstruction algorithms. Recently, a novel method for region of interest reconstruction that uses neither prior knowledge nor extrapolation has been published...
Recently, a reconstruction algorithm for region of interest (ROI) imaging in C-arm CT was published, named Approximate Truncation Robust Algorithm for Computed Tomography (ATRACT). Even in the presence of substantial data truncation, the algorithm is able to reconstruct images without the use of explicit extrapolation or prior knowledge. However, t...
This paper focuses on stat ionary detect ion of the pedestrian's intention to enter the traffic lane at intersections. We use an Interacting Multiple Model Extended Kalman Filter (IMM-EKF) based tracking approach as basic method to recognize this. In addition, we propose a novel Motion Contour image based HOG-like descriptor (MCHOG) in combination...
3-D endoscopy is an evolving field of research with the intention to improve safety and efficiency of minimally invasive surgeries. Time-of-Flight (ToF) imaging allows to acquire range data in real-time and has been engineered into a 3-D endoscope in combination with an RGB sensor (640x480px) as a hybrid imaging system, recently. However, the ToF s...
Minimally invasive procedures are of growing importance in modern surgery. Navigation and orientation are major issues during these interventions as conventional endoscopes only cover a limited field of view. We propose the application of a Time-of-Flight (ToF) satellite camera at the zenith of the pneumoperitoneum to survey the operation situs. Du...
A novel real-time multi-sensor framework for range imaging (RI) based respiratory motion analysis in image guided interventions such as fractionated radiation therapy is presented. We constitute our method based upon real-time constraints in clinical practice and an analytic analysis of RI based elastic body surface deformation fields. For the latt...
Purpose:
The intraprocedural tracking of respiratory motion has the potential to substantially improve image-guided diagnosis and interventions. The authors have developed a sparse-to-dense registration approach that is capable of recovering the patient's external 3D body surface and estimating a 4D (3D + time) surface motion field from sparse sam...
The recent availability of dynamic, dense, and low-cost range imaging has gained widespread interest in health care. It opens up new opportunities and has an increasing impact on both research and commercial activities. This chapter presents a state-of-the-art survey on the integration of modern range imaging sensors into medical applications. The...
Modeling the deformable shape of the left atrium is of strong interest for many applications in cardiac diagnosis and intervention. In this paper, we propose a method for left atrium shape modeling using non-rigid point cloud registration. In particular, we build upon the concept of Coherent Point Drift (CPD) registration that considers the alignme...
Purpose
In diagnostic tomographic imaging, patient setup and scanner initialization is a manual, tedious procedure in clinical practice. A fully-automatic detection of the patient’s position, orientation, posture and pose on the patient table holds great potential for optimizing this part of the imaging workflow. We propose a markerless framework t...
To manage respiratory motion in image-guided interventions a novel sparse-to-dense registration approach is presented. We apply an emerging laser-based active triangulation (AT) sensor that delivers sparse but highly accurate 3-D measurements in real-time. These sparse position measurements are registered with a dense reference surface extracted fr...
Over the last years, range imaging (RI) techniques have been proposed for patient positioning and respiration analysis in motion compensation. Yet, current RI based approaches for patient positioning employ rigid-body transformations, thus neglecting free-form deformations induced by respiratory motion. Furthermore, RI based respiration analysis re...
This paper focuses on monocular-video-based stationary detection of the pedestrian's intention to enter the traffic lane. We propose a motion contour image based HOG-like descriptor, MCHOG, and a machine learning algorithm that reaches the decision at an accuracy of 99% within the initial step at the curb of smart infrastructure. MCHOG implicitly c...
In radiation therapy, the estimation of torso deformations due to respiratory motion is an essential component for real-time tu-mor tracking solutions. Using range imaging (RI) sensors for continuous monitoring during the treatment, the 3-D surface motion field is recon-structed by a non-rigid registration of the patient's instantaneous body surfac...
In the medical field, the demand for motion-robust 3D data acquisition is steadily growing, e.g. for capturing limbs to construct prostheses. For this purpose, an optical 3D sensor is required which enables a flexible and comfortable 3D capturing of body parts. A " Flying Triangulation " sensor enables such tasks. Two exemplary applications, one in...
In radiation therapy, tracking the patient's non-rigid torso deformation during dose delivery holds potential to improve accuracy and efficiency using model-based tumor motion compensation. Conventional solutions rely on a 1-D respiration sur-rogate and are subject to model uncertainties. Instead, the proposed system acquires sparse 3-D measurement...
Detection, analysis and compensation of respiratory motion is a key issue for a variety of medical applications, such as tumor tracking in fractionated radiotherapy. One class of approaches aims for predicting the internal target movement by correlating intra-operatively captured body surface deformations to a pre-operatively learned deformable mod...
Recent advances in range imaging (RI) have enabled dense 3-D scene acquisition in real-time. However, due to physical limitations and the underlying range sampling principles, range data are subject to noise and may contain invalid measurements. Hence, data preprocessing is a prerequisite for practical applications but poses a challenge with respec...
In radiation therapy, prior to each treatment fraction, the patient must be aligned to computed tomography (CT) data. Patient setup verification systems based on range imaging (RI) can accurately verify the patient position and adjust the treatment table at a fine scale, but require an initial manual setup using lasers and skin markers. We propose...
The management of intra-fractional respiratory motion is becoming increasingly important in radiation therapy. Based on in advance acquired accurate 3D CT data and intra-fractionally recorded noisy timeof-flight (ToF) range data an improved treatment can be achieved. In this paper, a variational approach for the joint registration of the thorax sur...
The recent introduction of low-cost devices for real-time acquisition of dense 3-D range imaging (RI) streams has attracted a great deal of attention. However, to date, there exists no open source framework that is explicitly dedicated to real-time processing of RI streams. In this paper, we present the Range Imaging Toolkit (RITK). The goal is to...
Methods for 2D/3D face recognition typically combine results obtained independently from the 2D and 3D data, respectively. There has not been much emphasis on data fusion at an early stage, even though it is at least potentially more powerful to exploit possible synergies between the two modalities. In this paper, we propose photogeometric features...
Time-of-Flight (ToF) imaging is a promising technology for real-time metric surface acquisition and has recently been proposed
for a variety of medical applications. However, due to limitations of the sensor, range data from ToF cameras are subject
to noise and contain invalid outliers. In this paper, we discuss a real-time capable framework for To...
In the field of image-guided liver surgery (IGLS), the initial registration of the intra-operative organ surface with preoperative
tomographic image data is performed on manually selected anatomical landmarks. In this paper, we introduce a fully automatic
scheme that is able to estimate the transformation for initial organ registration in a multi-m...
The modeling of three-dimensional scene geometry from temporal point cloud streams is of particular interest for a variety of computer vision applications. With the advent of RGB-D imaging devices that deliver dense, metric and textured 6-D data in real-time, on-the-fly reconstruction of static environments has come into reach. In this paper, we pr...
We present a real-time multi-sensor architecture for video-based pedestrian detection used within a road side unit for intersection assistance. The entire system is implemented on available PC hardware, combining a frame grabber board with embedded FPGA and a graphics card into a powerful processing network. Giving classification performance top pr...
In this paper we present a novel automatic system to supervise and support rehabilitation and fitness exercises. Goal of the system is to enable autonomous training of rehabilitation patients to support their recovery from movement restrictions as well as the prevention of age-related diseases such as osteoporosis. The system uses time-of-flight te...
