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Report of improved performance in Talbot–Lau phase‐contrast computed tomography
Author(s) -
Weber Thomas,
Pelzer Georg,
Rieger Jens,
Ritter André,
Anton Gisela
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4921022
Subject(s) - imaging phantom , attenuation , contrast (vision) , contrast to noise ratio , phase (matter) , projection (relational algebra) , computed tomography , coherence (philosophical gambling strategy) , physics , tomography , phase contrast imaging , mathematics , nuclear medicine , phase contrast microscopy , optics , image quality , computer science , image (mathematics) , algorithm , medicine , statistics , radiology , artificial intelligence , quantum mechanics
Purpose: Many expectations have been raised since the use of conventional x‐ray tubes on grating‐based x‐ray phase‐contrast imaging. Despite a reported increase in contrast‐to‐noise ratio (CNR) in many publications, there is doubt on whether phase‐contrast computed tomography (CT) is advantageous in clinical CT scanners in vivo . The aim of this paper is to contribute to this discussion by analyzing the performance of a phase‐contrast CT laboratory setup. Methods: A phase‐contrast CT performance analysis was done. Projection images of a phantom were recorded, and image slices were reconstructed using standard filtered back projection methods. The resulting image slices were analyzed by determining the CNRs in the attenuation and phase image. These results were compared to analytically calculated expectations according to the already published phase‐contrast CT performance analysis by Raupach and Flohr [Med. Phys. 39 , 4761–4774 (2012)]. There, a severe mistake was found leading to wrong predictions of the performance of phase‐contrast CT. The error was corrected and with the new formulae, the experimentally obtained results matched the analytical calculations. Results: The squared ratios of the phase‐contrast CNR and the attenuation CNR obtained in the authors’ experiment are five‐ to ten‐fold higher than predicted by Raupach and Flohr [Med. Phys. 39 , 4761–4774 (2012)]. The effective lateral spatial coherence length deduced outnumbers the already optimistic assumption of Raupach and Flohr [Med. Phys. 39 , 4761–4774 (2012)] by a factor of 3. Conclusions: The authors’ results indicate that the assumptions made in former performance analyses are pessimistic. The break‐even point, when phase‐contrast CT outperforms attenuation CT, is within reach even with realistic, nonperfect gratings. Further improvements to state‐of‐the‐art clinical CT scanners, like increasing the spatial resolution, could change the balance in favor of phase‐contrast computed tomography even more. This could be done by, e.g., quantum‐counting pixel detectors with four‐fold smaller pixel pitches.