Scanner influence on the mechanical response of QCT-based finite element analysis of long bones

Yekutiel Katz, Gal Dahan, Jacob Sosna, Ilan Shelef, Evgenia Cherniavsky, Zohar Yosibash*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Patient-specific QCT-based finite element (QCTFE) analyses enable highly accurate quantification of bone strength. We evaluated CT scanner influence on QCTFE models of long bones. A femur, humerus, and proximal femur without the head were scanned with K 2 HPO 4 phantoms by seven CT scanners (four models) using typical clinical protocols. QCTFE models were constructed. The geometrical dimensions, as well as the QCT-values expressed in Hounsfield unit (HU) distribution was compared. Principal strains at representative regions of interest (ROIs), and maximum principal strains (associated with fracture risk) were compared. Intraclass correlation coefficients (ICCs) were calculated to evaluate strain prediction reliability for different scanners. Repeatability was examined by scanning the femur twice and comparing resulting QCTFE models. Maximum difference in geometry was 2.3%. HU histograms before phantom calibration showed wide variation between QCT scans; however, bone density histogram variability was reduced after calibration and algorithmic manipulation. Relative standard deviation (RSD) in principal strains at ROIs was <10.7%. ICC estimates between scanners were >0.9. Fracture-associated strain had 6.7%, 8.1%, and 13.3% maximum RSD for the femur, humerus, and proximal femur, respectively. The difference in maximum strain location was <2 mm. The average difference with repeat scans was 2.7%. Quantification of strain differences showed mean RSD bounded by ∼6% in ROIs. Fracture-associated strains in “regular” bones showed a mean RSD bounded by ∼8%. Strains were obtained within a ±10% difference relative to the mean; thus, in a longitudinal study only changes larger than 20% in the principal strains may be significant. ICCs indicated high reliability of QCTFE models derived from different scanners.

Original languageAmerican English
Pages (from-to)149-159
Number of pages11
JournalJournal of Biomechanics
Volume86
DOIs
StatePublished - 27 Mar 2019

Bibliographical note

Funding Information:
The study was funded in part by a grant from the Milgrom Foundation for Science grant. The authors thank Dr. Gabriel Bartal and Mr. Isaac Yunes at Meir Medical Center, Mr. David Shushan at the Soroka Medical Center, and Mrs. Nathalie Greenberg from the Hadassah-Hebrew University Medical Center for their help and collaboration on the acquisition of the QCT scans. The authors thank Prof. Joyce Keyak from the University of California at Irvine in the USA and Dr. Nir Trabelsi from the Shamoon College of Engineering in Israel for interesting discussions. The authors thank Dr. Lena Novack from Ben Gurion University of the Negev and Prof. Malka Gurfine from Tel-Aviv University for their assistance on the statistical analysis and Mrs. Shifra Fraifeld from the Hadassah-Hebrew University Medical Center for helpful editorial assistance.

Publisher Copyright:
© 2019 Elsevier Ltd

Keywords

  • Femur
  • Finite element analysis
  • Humerus
  • Patient-specific
  • Personalized medicine
  • QCT

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