The PASCAL Visual Object Classes Challenge

The effect of the width to length ratios of corrosion defects on the burst pressures of transmission pipelines

In industrial settings, X-ray computed tomography scans are a common tool for inspection of objects. Often the object can not be imaged using standard circular or helical trajectories because of constraints in space or time. Compared to medical applications the variance in size and materials is much larger. Adapting the acquisition trajectory to the object is beneficial and sometimes inevitable. There are currently no sophisticated methods for this adoption. Typically the operator places the object according to his best knowledge. We propose a detectability index based optimization algorithm which determines the scan trajectory on the basis of a CAD-model of the object. The detectability index is computed solely from simulated projections for multiple user defined features. By adapting the features the algorithm is adapted to different imaging tasks. Performance of simulated and measured data was qualitatively and quantitatively assessed.The results illustrate that our algorithm not only allows more accurate detection of features, but also delivers images with high overall quality in comparison to standard trajectory reconstructions. This work enables to reduce the number of projections and in consequence scan time by introducing an optimization algorithm to compose an object specific trajectory.

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Object Specific Trajectory Optimization for Industrial X-ray Computed Tomography

To compare the outcomes of colonic splenic flexure tumours treated by extended right colectomy versus left colectomy. Stage I–III splenic flexure tumours, treated either by extended right colectomy or left colectomy between 1996 and 2011, were identified in a prospective database, and the short- and long-term outcomes compared. The survival analyses were performed using the Kaplan–Meier method and adjusted using a Cox-proportional hazard model. A total of 30 (44 %) splenic flexure tumours were resected by left colectomy and 38 (56 %) by right colectomy. Emergency operations were more common (74 versus 20 %, p < 0.001) in the right colectomy group. In the univariate analysis, the 5-year overall survival (55 % for right colectomy versus 60 % for left colectomy, p = 0.197) and 5-year recurrence-free survival (41 versus 54 %, p = 0.180, respectively) showed a trend towards a non-significant survival benefit for left colectomy. However, when adjusted for age, gender, ASA classification, tumour stage, urgency and year of surgery, this trend disappeared. Patients undergoing extended right or left colectomy for splenic flexure tumours seemed to have comparable short- and long-term outcomes.

The short- and long-term outcomes for patients with splenic flexure tumours treated by left versus extended right colectomy are comparable: a retrospective analysis

In this work we study the relation between the quality of a binary tomographic reconstruction and the choice of angles of the projections. We conduct experiments on a set of software phantoms by reconstructing them from different projection sets using three different discrete tomography reconstruction algorithms, and compare the accuracy of the corresponding reconstructions with suitable approaches. To validate our results for possible real-world applications, we conduct the experiments by adding random noise of different characteristics to the simulated projection data, and by applying small topological changes on the phantom images as well. In addition, we also discuss some consequences of the angle-selection dependency and possible practical applications arising from the field of non-destructive testing, too.

Direction-dependency of binary tomographic reconstruction algorithms

Automatic segmentation of hyperreflective foci in OCT images

In this paper we study how the choice of projection angles affect the quality of the discrete tomographic reconstruction of an object. We supply four different strategies for selecting projection angle sets and compare them by conducting experiments on a set of software phantoms. We also discuss some consequences of our observations. Furthermore, we introduce a possible application of the proposed angle selection algorithms as well.

/pdf/projection-selection-algorithms-for-discrete-tomography-12rb6mh9b6.pdf

Projection Selection Algorithms for Discrete Tomography

It has already been shown that the choice of projection angles can significantly influence the quality of reconstructions in discrete tomography. In this contribution we summarize and extend the previous results by explaining and demonstrating tile effects of projection selection dependency, in a set of experimental software tests. We perform reconstructions of software phantoms, by using different binary tomography reconstruction algorithms, from different equiangular and non-equiangular projections sets, under various conditions (i.e., when the objects to be reconstructed undergo slight topological changes, or the projection data is affected by noise) and compare the results with suitable approaches. Based on our observations, we reveal regularities in the resulting data and discuss possible consequences of such projection selection dependency in binary tomography.

/pdf/projection-selection-dependency-in-binary-tomography-4g191qnvcz.pdf

Projection selection dependency in binary tomography

There is a wide range of algorithms for binary
and non-binary (called multivalued) discrete tomography. For example, the DART, Discrete Algebraic
Reconstruction Technique (4) is capable of producing
highly accurate reconstructions by thresholding a continuous reconstruction and then adjusting the object
boundaries. Also, there are reconstruction algorithms
based on minimizing an energy function by deterministic (13; 15; 16; 18) or randomized (1; 2; 8; 14)
optimization strategies.

/pdf/an-energy-minimization-reconstruction-algorithm-for-posxqsci77.pdf

László Varga

Papers

Direction-dependency of binary tomographic reconstruction algorithms

Automatic segmentation of hyperreflective foci in OCT images

Projection Selection Algorithms for Discrete Tomography

Projection selection dependency in binary tomography

An energy minimization reconstruction algorithm for multivalued discrete tomography