title: A fast and pragmatic approach for scatter correction in flat-detector CT using elliptic modeling and iterative optimization.
abstract: Scattered radiation is a major source of artifacts in flat detector computed tomography (FDCT) due to the increased irradiated volumes. We propose a fast projection-based algorithm for correction of scatter artifacts. The presented algorithm combines a convolution method to determine the spatial distribution of the scatter intensity distribution with an object-size-dependent scaling of the scatter intensity distributions using a priori information generated by Monte Carlo simulations. A projection-based (PBSE) and an image-based (IBSE) strategy for size estimation of the scanned object are presented. Both strategies provide good correction and comparable results; the faster PBSE strategy is recommended. Even with such a fast and simple algorithm that in the PBSE variant does not rely on reconstructed volumes or scatter measurements, it is possible to provide a reasonable scatter correction even for truncated scans. For both simulations and measurements, scatter artifacts were significantly reduced and the algorithm showed stable behavior in the z-direction. For simulated voxelized head, hip and thorax phantoms, a figure of merit Q of 0.82, 0.76 and 0.77 was reached, respectively (Q = 0 for uncorrected, Q = 1 for ideal). For a water phantom with 15 cm diameter, for example, a cupping reduction from 10.8% down to 2.1% was achieved. The performance of the correction method has limitations in the case of measurements using non-ideal detectors, intensity calibration, etc. An iterative approach to overcome most of these limitations was proposed. This approach is based on root finding of a cupping metric and may be useful for other scatter correction methods as well. By this optimization, cupping of the measured water phantom was further reduced down to 0.9%. The algorithm was evaluated on a commercial system including truncated and non-homogeneous clinically relevant objects.
authors.affiliation: Institute of Medical Physics, University of Erlangen-Nürnberg, Germany. michael.meyer@imp.uni-erlangen.de
authors.forename: Michael
authors.initials: M
authors.lastname: Meyer
authors.forename: Willi A
authors.initials: WA
authors.lastname: Kalender
authors.forename: Yiannis
authors.initials: Y
authors.lastname: Kyriakou
mesh_terms: D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D003198:Computer Simulation; D005260:Female; D006257:Head / Q000000981:diagnostic imaging; D006615:Hip / Q000000981:diagnostic imaging; D006801:Humans; D008962:Models, Theoretical; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D013902:Radiography, Thoracic / Q000295:instrumentation / Q000379:methods; D012542:Scattering, Radiation; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014867:Water
chemical_list: D014867:Water