Contour reconstruction directly from helical cone-beam projections for non-destructive evaluation application of X-ray CT
In non-destructive evaluation or medical imaging, X-ray computed tomography (CT) is a well-established visualisation technique. Detection of the contours of different contrast image regions are an essential and necessary requirement (for example the defect recognition and measurement in non-destructive evaluation). The two-step approach, reconstructing images from projections first and then detecting the contours from the reconstructed images, is time-consuming and the post-processing of a reconstructed image is often difficult. In recent years, helical cone-beam CT has been widely used because of its faster scanning speed, efficient utilisation of the X-ray dose and a natural manner to scan long objects. This paper presents an algorithm for reconstructing contours directly from helical cone-beam projections based on the single-slice rebinning algorithm and wavelet analysis. The algorithm can be briefly summarised as: (1) using the single-slice rebinning algorithm to convert the helical cone-beam projection set to a stack of fan-beam sinograms; (2) using a convolution back-projection operation to obtain the wavelet coefficients, where the convolution filter is the combination of the fan-beam projection of a 2D wavelet with ramp filter; and (3) detecting zero crossings of the wavelet coefficients to obtain the contours. Simulation results show the usefulness and high efficiency of the presented algorithm. For some cases of noisy projection data, the contour detection outcome by our algorithm is obviously better than that of the two-step approach. Moreover, the run-time is less than that of the two-step approach.
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Document Type: Research Article
Publication date: 2012-10-01
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- Official Journal of The British Institute of Non-Destructive Testing - includes original research and devlopment papers, technical and scientific reviews and case studies in the fields of NDT and CM.
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