Dr. Henning Friis Poulsen Profile

Dr. Henning Friis Poulsen

Senior Researcher at Technical Univ of Denmark

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Publications (6)

SPIE Journal Paper | 30 June 2022

Significance of the spectral correction of photon counting detector response in material classification from spectral x-ray CT

Doniyor Jumanazarov, Jakeoung Koo, Henning Poulsen, Ulrik Olsen, Mihai Iovea

JMI, Vol. 9, Issue 03, 034504, (June 2022) https://doi.org/10.1117/12.10.1117/1.JMI.9.3.034504

KEYWORDS: Sensors, Photon counting, Reconstruction algorithms, Signal attenuation, X-ray computed tomography, Detection and tracking algorithms, X-rays, Aluminum, X-ray detectors, Silicon

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Proceedings Article | 18 April 2021 Presentation + Paper

The significance of the spectral correction of photon counting detector response in material classification from spectral x-ray CT

Doniyor Jumanazarov, Ja-Keoung Koo, Henning Poulsen, Ulrik Olsen, Mihai Iovea

Proceedings Volume 11771, 117710J (2021) https://doi.org/10.1117/12.2589290

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Photon counting imaging detectors (PCD) has paved the way for the emergence of Spectral X-ray Computed Tomography (SCT), which simultaneously measures a material’s linear attenuation coefficient (LAC) at multiple energies defined by the energy thresholds. In previous work SCT data was analysed with the SIMCAD method for material classifications. The method measures system-independent material properties such as electron density, ρ_e and effective atomic number, Z_eff to identify materials in security applications. The method employs a spectral correction algorithm that reduce the primary spectral distortions from the raw data that arise from the detector response: charge sharing and weighting potential cross-talk, fluorescence radiation, scattering radiation, pulse pile up and incomplete charge collection. In this work, using real experimental data we analyze the influence of the spectral correction on material classification performance in security applications. We use a vectorial total variation (L∞-VTV) as a convex regularizer for image reconstruction of the spectral sinogram. This reconstruction algorithm employs a L∞ norm to penalize the violation of the inter energy bin dependency, resulting in strong coupling among energy bins. Due to the strong inter-bin correlation, L∞-VTV leads to noticeably better performance compared to bin-by-bin reconstructions including SIRT and total variation (TV) reconstruction algorithms. The image quality was evaluated with the correlation coefficient that is computed relative to ground-truth images. A positive weighting parameter defines the strength of the L∞-VTV regularization term and thus controls the trade-off between a good match to spectral sinogram data and a smooth reconstruction in both the spatial and spectral dimension. The classification accuracy both for raw and corrected data is analyzed over a set of weighting parameters. For material classification, we used 20 different materials for calibrating the SIMCAD method and 15 additional materials in the range of 6 ≤ Zeff ≤ 15 for evaluating the classification performance. We show that the correction algorithm accurately reconstructs the measured attenuation curve, and thus gives higher detection rates. We show that using the spectral correction leads to an accuracy increase of 1.6 and 3.8 times in estimating ρ_eand Z_eff, respectively

SPIE Journal Paper | 1 November 2006

Optimized algebraic reconstruction technique for generation of grain maps based on three-dimensional x-ray diffraction (3DXRD)

Xiaowei Fu, Erik Knudsen, Henning Poulsen, Gabor Herman, Bruno Carvalho, Hstau Liao

OE, Vol. 45, Issue 11, 116501, (November 2006) https://doi.org/10.1117/12.10.1117/1.2390680

KEYWORDS: Reconstruction algorithms, Diffraction, Sensors, Optical engineering, X-ray diffraction, X-rays, Computer simulations, Data acquisition, Crystals, Crystallography

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Proceedings Article | 26 October 2004 Paper

Measurement of the components of plastic displacement gradients in three dimensions

Soeren Nielsen, Felix Beckmann, Rasmus Godiksen, Kristoffer Haldrup, Henning Poulsen, John Wert

Proceedings Volume 5535, (2004) https://doi.org/10.1117/12.559641

KEYWORDS: Particles, Tomography, X-rays, Aluminum, Spatial resolution, Absorption, 3D metrology, Image compression, Metals, Nondestructive evaluation

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Proceedings Article | 26 October 2004 Paper

Optimization of an algebraic reconstruction technique for generation of grain maps based on diffraction data

Xiaowei Fu, Erik Knudsen, Henning Poulsen, Gabor Herman, Bruno Carvalho, Hstau Liao

Proceedings Volume 5535, (2004) https://doi.org/10.1117/12.559602

KEYWORDS: Reconstruction algorithms, Diffraction, Sensors, X-rays, Computer simulations, Algorithm development, Fourier transforms, Positron emission tomography, Hard x-rays, X-ray diffraction

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