title: Restoration of Thickness, Density, and Volume for Highly Blurred Thin Cortical Bones in Clinical CT Images.
abstract: In clinical CT images containing thin osseous structures, accurate definition of the geometry and density is limited by the scanner's resolution and radiation dose. This study presents and validates a practical methodology for restoring information about thin bone structure by volumetric deblurring of images. The methodology involves 2 steps: a phantom-free, post-reconstruction estimation of the 3D point spread function (PSF) from CT data sets, followed by iterative deconvolution using the PSF estimate. Performance of 5 iterative deconvolution algorithms, blind, Richardson-Lucy (standard, plus Total Variation versions), modified residual norm steepest descent (MRNSD), and Conjugate Gradient Least-Squares were evaluated using CT scans of synthetic cortical bone phantoms. The MRNSD algorithm resulted in the highest relative deblurring performance as assessed by a cortical bone thickness error (0.18 mm) and intensity error (150 HU), and was subsequently applied on a CT image of a cadaveric skull. Performance was compared against micro-CT images of the excised thin cortical bone samples from the skull (average thickness 1.08 ± 0.77 mm). Error in quantitative measurements made from the deblurred images was reduced 82% (p < 0.01) for cortical thickness and 55% (p < 0.01) for bone mineral mass. These results demonstrate a significant restoration of geometrical and radiological density information derived for thin osseous features.
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada.
authors.forename: Amirreza
authors.initials: A
authors.lastname: Pakdel
authors.affiliation: Sunnybrook Health Sciences Center, Toronto, ON, Canada.
authors.forename: Michael
authors.initials: M
authors.lastname: Hardisty
authors.affiliation: Sunnybrook Health Sciences Center, Toronto, ON, Canada.|Division of Plastic and Reconstructive Surgery, University of Toronto, Toronto, ON, Canada.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Fialkov
authors.affiliation: Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, ON, Canada. cari.whyne@sunnybrook.ca.|Sunnybrook Health Sciences Center, Toronto, ON, Canada. cari.whyne@sunnybrook.ca.|Faculty of Medicine, University of Toronto, Toronto, ON, Canada. cari.whyne@sunnybrook.ca.
authors.forename: Cari
authors.initials: C
authors.lastname: Whyne
mesh_terms: D000465:Algorithms; D015519:Bone Density; D000071538:Cortical Bone / Q000000981:diagnostic imaging*; D006801:Humans; D021621:Imaging, Three-Dimensional; D012886:Skull / Q000000981:diagnostic imaging*; D055114:X-Ray Microtomography / Q000379:methods*
keywords: Computed tomography (CT); Cortical thickness and intensity; Deconvolution; Point spread function; Quantitative image analysis