Frits Post | Technical University of Delft, Netherlands (original) (raw)

Papers by Frits Post

Medical Imaging 2007: Visualization and Image-Guided Procedures, 2007

This paper explores new methods to visualize and fuse multi-2D bioluminescence imaging (BLI) data... more This paper explores new methods to visualize and fuse multi-2D bioluminescence imaging (BLI) data with structural imaging modalities such as micro CT and MR. A geometric, back-projection-based 3D reconstruction for superficial lesions from multi-2D BLI data is presented, enabling a coarse estimate of the 3D source envelopes from the multi-2D BLI data. Also, an intuitive 3D landmark selection is developed to enable fast BLI / CT registration. Three modes of fused BLI / CT visualization were developed: slice visualization, carousel visualization and 3D surface visualization. The added value of the fused visualization is demonstrated in three small-animal experiments, where the sensitivity of BLI to detect cell clusters is combined with anatomical detail from micro-CT imaging.

Flow visualization has been a very attractive part of visualization research for a long time. Usu... more Flow visualization has been a very attractive part of visualization research for a long time. Usually very large datasets need to be processed, which often consist of multivariate data with a large number of sample locations, often arranged in multiple time steps. Recently, the steadily increasing performance of computers again has be- come a driving factor for a reemergence in flow visualization, especially in techniques based on feature extraction, vector field clustering, and topology extraction. In this article and a companion paper 69, the state of the art in flow visualization (FlowVis) is presented. In this paper, direct (or global) flow visualization such as hedgehog plots, texture-based flow visualization such as line integral convolution, and geometric flow visualization such as stream lines is discussed. Part 2 of this report 69 focusses on feature-based flow visualization in detail. In this paper, also an attempt of categorizing FlowVis solutions is presented which is in...

Flow visualisation is an attractive topic in data visualisation, offering great challenges for re... more Flow visualisation is an attractive topic in data visualisation, offering great challenges for research. Very large data sets must be processed, consisting of multivariate data at large numbers of grid points, often arranged in many time steps. Recently, the steadily increasing performance of computers again has become a driving force for new advances in flow visualisation, especially in techniques based on texturing, feature extraction, vector field clustering, and topology extraction.

Flow visualization has been a very attractive component of scientific visualization research for ... more Flow visualization has been a very attractive component of scientific visualization research for a long time. Usually very large multivariate datasets require processing. These datasets often consist of a large number of sample locations and several time steps. The steadily increasing performance of computers has recently become a driving factor for a reemergence in flow visualization research, especially in texture-based techniques. In this paper, dense, texture-based flow visualization techniques are discussed. This class of techniques attempts to provide a complete, dense representation of the flow field with high spatio-temporal coherency. An attempt of categorizing closely related solutions is incorporated and presented. Fundamentals are shortly addressed as well as advantages and disadvantages of the methods.

Proceedings Visualization '98 (Cat. No.98CB36276), 1998

Vortices are important features in many research and engineering fields. Visualization is an impo... more Vortices are important features in many research and engineering fields. Visualization is an important step in gaining more understanding and control of vortices. Vortex detection criteria fall into two categories: point-based scalar quantities, calculated at single points, and curve-based geometric criteria, calculated for e.g. streamlines. The first category is easy to compute, but does not work in all cases. The second category is more intuitive and should work in all cases, but currently only works in 2D (or 3D projected) flows. We show applications of both approaches in hydrodynamic flows.

IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2003

The quality of volume visualization depends strongly on the quality of the underlying data. In vi... more The quality of volume visualization depends strongly on the quality of the underlying data. In virtual colonoscopy, CT data should be acquired at a low radiation dose that results in a low signal-to-noise ratio. Alternatively, MRI data is acquired without ionizing radiation, but suffers from noise and bias (global signal fluctuations). Current volume visualization techniques often do not produce good

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine

In shoulder arthroplasty, malpositioning of prostheses often leads to reduced postoperative range... more In shoulder arthroplasty, malpositioning of prostheses often leads to reduced postoperative range of motion (ROM) and complications such as impingement, loosening, and dislocation. Furthermore, the risk of impingement complications increases when reverse total prostheses are used. For this purpose a pre-operative planning system was developed that enables surgeons to perform a virtual shoulder replacement procedure. The present authors' pre-operative planning system simulates patient-specific bone-determined ROM meant to reduce the risk of impingement complications and to improve the ROM of patients undergoing shoulder replacement surgery. This paper describes a validation experiment with the purpose of ratifying the clinical applicability and usefulness of the ROM simulation module for shoulder replacement surgery. The experiment was performed on cadaveric shoulders. A data connection was set up between the software environment and an existing intra-operative guidance system to...

International Journal of Computer Assisted Radiology and Surgery

Segmentation of rheumatoid joints from CT images is a complicated task. The pathological state of... more Segmentation of rheumatoid joints from CT images is a complicated task. The pathological state of the joint results in a non-uniform density of the bone tissue, with holes and irregularities complicating the segmentation process. For the specific case of the shoulder joint, existing segmentation techniques often fail and lead to poor results. This paper describes a novel method for the segmentation of these joints. Given a rough surface model of the shoulder, a loop that encircles the joint is extracted by calculating the minimum curvature of the surface model. The intersection points of this loop with the separate CT-slices are connected by means of a path search algorithm. Inaccurate sections are corrected by iteratively applying a Hough transform to the segmentation result. As a qualitative measure we calculated the Dice coefficient and Hausdorff distances of the automatic segmentations and expert manual segmentations of CT-scans of ten severely deteriorated shoulder joints. For ...

Virtual colonoscopy is a non-invasive technique for the detection of polyps. Currently, a clean c... more Virtual colonoscopy is a non-invasive technique for the detection of polyps. Currently, a clean colon is required; as without cleansing the colonic wall cannot be seg- mented. Enhanced bowel preparation schemes opacify intraluminal remains to enable colon segmentation. Computed cleansing (as opposed to physical cleansing of the bowels) allows removal of tagged intraluminal remains. This paper describes a model that

Virtual colonoscopy or 'colonography' is a patient-friendly, modern screening technique f... more Virtual colonoscopy or 'colonography' is a patient-friendly, modern screening technique for polyps. Automatic detection of polyps can serve to assist the radiologist. This paper presents a method based on clustering the principal curvatures. Via automatic polyp detection 5/6 polyps (>5 mm) were detected at the expense of 9 false positive findings per case. For visualization, the bowel sur- face is

Lecture Notes in Computer Science, 2001

Virtual colonoscopy or 'colonography' is a patient-friendly, modern screening technique for polyp... more Virtual colonoscopy or 'colonography' is a patient-friendly, modern screening technique for polyps. Automatic detection of polyps can serve to assist the radiologist. This paper presents a method based on clustering the principal curvatures. Via automatic polyp detection 5/6 polyps (>5 mm) were detected at the expense of 9 false positive findings per case. For visualization, the bowel surface is presented to the physician in a 'panoramic' way as a sequence of unfolded cubes. Conventionally, only 93% of the colon surface is available for examination. In our approach the area in view is increased to 99.8%. The unfolded cube visualization is another step to optimize polyp detection by visual examination. Experiments show a sensitivity of 10/10 (on a per patient basis) for any polyp. The specificity was 7/10.

Lecture Notes in Computer Science, 2002

Visualization of medical data requires the extraction of surfaces that represent the boundaries o... more Visualization of medical data requires the extraction of surfaces that represent the boundaries of objects of interest. This paper describes a method that combines nding these boundaries accurately and ensuring that this surface consists of high quality triangles. The latter is important for subsequent visual- ization and simulation. We show that the surfaces created using this method are both accurate

Lecture Notes in Computer Science, 2000

... PhD thesis, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, 1999. Sof... more ... PhD thesis, School of Computer Science, Carnegie Mellon University, Pittsburgh, PA, 1999. Software and thesis available at: http://www.cs.cmu.edu/~garland/quadrics/. [6] Gibson, S. Constrained elastic surfacenets: generating smooth surfaces from binary sampled data. ...

Mathematics and Visualization, 2007

Flow visualization research has made rapid advances in recent years, especially in the area of to... more Flow visualization research has made rapid advances in recent years, especially in the area of topology-based flow visualization. The ever increasing size of scientific data sets favors algorithms that are capable of extracting important subsets of the data, leaving the scientist with a more manageable representation that may be visualized interactively. Extracting the topology of a flow achieves the goal of obtaining a compact representation of a vector or tensor field while simultaneously retaining its most important features. We present the ...