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Technical Brief

Influence of scan resolution, thresholding and smoothing on computed tomography (CT) based kinematic measurements.

[+] Author and Article Information
Christopher Tan

The University of Sydney, NSW 2006 Australia, Sydney School of Veterinary Science; Surgical and Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW, Australia; University Veterinary Teaching Hospital, Sydney. Evelyn Williams Building (B10) Faculty of Veterinary Science, University of Sydney, NSW, Australia 2006
chris.tan@sydney.edu.au

William C H Parr

Surgical and Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW, Australia
parr.will@googlemail.com

William R Walsh

Surgical and Orthopaedic Research Laboratories, Prince of Wales Clinical School, UNSW, Australia
wrwalshau@gmail.com

Mariano Makara

The University of Sydney, NSW 2006 Australia, Sydney School of Veterinary Science
mariano.makara@sydney.edu.au

Kenneth A Johnson

The University of Sydney, NSW 2006 Australia, Sydney School of Veterinary Science
kenneth.johnson@sydney.edu.au

1Corresponding author.

ASME doi:10.1115/1.4037558 History: Received November 02, 2016; Revised August 04, 2017

Abstract

Radiographic data, including CT and planar x-ray, is increasingly used for human and animal kinematic studies. There is a tendency towards using as high resolution imaging as possible, which increases the precision of reconstructed 3d surface models of bone. However, to date no study has tested the effects of scan resolution, threshold and 3d model reconstruction parameters on the accuracy of bone kinematic results. The present study uses a novel method to do this where canine tarsal bones were positioned on a radiolucent LegoTM board and scanned before and after undergoing known translations and/or rotations. The DICOM images were acquired using two different CT scanning resolutions and processed using three different segmentation threshold levels and three different smoothing protocols. Using one bone as the reference bone, an iterative closest point (ICP) algorithm was used to register bones to a global co-ordinate system and allow measurement of other bone kinematics in terms of translations and rotations in and around the x, y, z axes. The measured kinematics were compared to the 'known' kinematics, which were obtained from the LegoTM board's manufacturing standards and tolerances, to give accuracy error metrics for all bones. The results showed error in accuracy of measured kinematics was at sub voxel levels (less than 0.5mm). Despite altering the volume and surface area of the 3D bone models, variation in resolution, segmentation threshold and smoothing had no significant influence upon the accuracy of the calculated bone kinematics.

Copyright (c) 2017 by ASME
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