Experimental implementation of a polyenergetic statistical reconstruction algorithm for a commercial fan-beam CT scanner.
OBJECTIVE
To present a framework for characterizing the data needed to implement a polyenergetic model-based statistical reconstruction algorithm, Alternating Minimization (AM), on a commercial fan-beam CT scanner and a novel method for assessing the accuracy of the commissioned data model.


METHODS
The X-ray spectra for three tube potentials on the Philips Brilliance CT scanner were estimated by fitting a semi-empirical X-ray spectrum model to transmission measurements. Spectral variations due to the bowtie filter were computationally modeled. Eight homogeneous cylinders of PMMA, Teflon and water with varying diameters were scanned at each energy. Central-axis scatter was measured for each cylinder using a beam-stop technique. AM reconstruction with a single-basis object-model matched to the scanned cylinder's composition allows assessment of the accuracy of the AM algorithm's polyenergetic data model. Filtered-backprojection (FBP) was also performed to compare consistency metrics such as uniformity and object-size dependence.


RESULTS
The spectrum model fit measured transmission curves with residual root-mean-square-error of 1.20%-1.34% for the three scanning energies. The estimated spectrum and scatter data supported polyenergetic AM reconstruction of the test cylinders to within 0.5% of expected in the matched object-model reconstruction test. In comparison to FBP, polyenergetic AM exhibited better uniformity and less object-size dependence.


CONCLUSIONS
Reconstruction using a matched object-model illustrate that the polyenergetic AM algorithm's data model was commissioned to within 0.5% of an expected ground truth. These results support ongoing and future research with polyenergetic AM reconstruction of commercial fan-beam CT data for quantitative CT applications.
Department of Radiation Oncology, Virginia Commonwealth University, 401 College St., Box 980037, Richmond, VA 23298, USA. jevans2@mcvh-vcu.edu
Joshua D
JD
Evans
Bruce R
BR
Whiting
David G
DG
Politte
Joseph A
JA
O'Sullivan
Paul F
PF
Klahr
Jeffrey F
JF
Williamson
D000465:Algorithms; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D061089:Radiotherapy, Image-Guided; D013223:Statistics as Topic / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*; D035501:Uncertainty
Alternating Minimization; Model-based statistical iterative reconstruction; Polyenergetic statistical reconstruction; Quantitative computed tomography