title: Backprojection-filtration reconstruction without invoking a spatially varying weighting factor.
abstract: OBJECTIVE
  To develop a backprojection-filtration (BPF) algorithm with improved noise properties over the existing BPF algorithm through utilizing (approximate) redundant information in circular cone-beam or fan-beam scans.
  
  
  METHODS
  The backprojection steps in the existing filtered-backprojection (FBP) and BPF algorithms for fan-beam and cone-beam projections invoke spatially varying weighting factors, which may not only increase the computational load in image reconstruction but also, more importantly, result in reconstruction artifacts. Redundant information in fan-beam projections has been exploited for eliminating the weighting factor in the existing FBP algorithm. However, the new FBP algorithm cannot be applied to image reconstruction in a region of interest from transversely truncated data. In this work, the authors identify approximate data redundancy in circular cone-beam projections and propose a new BPF algorithm in which the approximate data redundancy is exploited for eliminating the spatially varying weighting factor in the existing BPF algorithm.
  
  
  RESULTS
  The authors have implemented and evaluated the proposed BPF algorithm in numerical studies of reconstructing 3D images from both the nontruncated and truncated projection data in a circular cone-beam scan. The results of numerical studies demonstrate that the proposed BPF algorithm retains the resolution property of the existing BPF algorithm, and that it can also reconstruct accurately ROI images from truncated data. More importantly, the results also indicate that the proposed BPF algorithm not only is computationally more efficient but also yields generally lower image variances than the existing BPF algorithm.
  
  
  CONCLUSIONS
  A BPF algorithm was proposed that not only retains the desirable properties of the existing BPF algorithm but also possesses improved computational and noise properties over the latter.
authors.affiliation: Department of Radiology, The University of Chicago, 5841 South Maryland Avenue, Chicago, Illinois 60637, USA.
authors.forename: Dan
authors.initials: D
authors.lastname: Xia
authors.forename: Seungryong
authors.initials: S
authors.lastname: Cho
authors.forename: Xiaochuan
authors.initials: X
authors.lastname: Pan
mesh_terms: D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D019047:Phantoms, Imaging; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
references.citation: IEEE Trans Med Imaging. 2004 Sep;23(9):1109-16
references.pmid: 15377120
references.citation: Med Phys. 1997 Sep;24(9):1375-84
references.pmid: 9304565
references.citation: Phys Med Biol. 2004 Dec 21;49(24):5489-503
references.pmid: 15724538
references.citation: Med Phys. 2004 Jun;31(6):1348-56
references.pmid: 15259638
references.citation: Med Phys. 2003 Apr;30(4):590-600
references.pmid: 12722811
references.citation: Med Phys. 2005 Mar;32(3):673-84
references.pmid: 15839339
references.citation: Phys Med Biol. 2005 May 7;50(9):2099-111
references.pmid: 15843739
references.citation: Phys Med Biol. 2004 Sep 21;49(18):4349-69
references.pmid: 15509070
references.citation: IEEE Trans Med Imaging. 2007 Oct;26(10):1328-44
references.pmid: 17948724
references.citation: J Opt Soc Am A Opt Image Sci Vis. 2005 Nov;22(11):2372-84
references.pmid: 16304723
references.citation: Phys Med Biol. 2004 Mar 21;49(6):941-59
references.pmid: 15104318
references.citation: IEEE Trans Med Imaging. 2008;27(7):887-96
references.pmid: 18599394
references.citation: IEEE Trans Med Imaging. 2006 Jul;25(7):869-81
references.pmid: 16827488
references.citation: Med Phys. 2003 Nov;30(11):2869-77
references.pmid: 14655933
references.citation: Med Phys. 2006 Feb;33(2):475-81
references.pmid: 16532955
references.citation: Int J Radiat Oncol Biol Phys. 2002 Aug 1;53(5):1337-49
references.pmid: 12128137
references.citation: Med Phys. 2005 Nov;32(11):3389-94
references.pmid: 16372414
references.citation: Phys Med Biol. 2004 Nov 21;49(22):5059-72
references.pmid: 15609558
references.citation: Phys Med Biol. 2003 Dec 7;48(23):3787-818
references.pmid: 14703159
references.citation: Phys Med Biol. 2007 Jun 7;52(11):3227-40
references.pmid: 17505099
references.citation: IEEE Trans Med Imaging. 2005 Jan;24(1):70-85
references.pmid: 15638187