title: Quantitative Computed Tomography (QCT) derived Bone Mineral Density (BMD) in finite element studies: a review of the literature.
abstract: BACKGROUND
  Finite element modeling of human bone provides a powerful tool to evaluate a wide variety of outcomes in a highly repeatable and parametric manner. These models are most often derived from computed tomography data, with mechanical properties related to bone mineral density (BMD) from the x-ray energy attenuation provided from this data. To increase accuracy, many researchers report the use of quantitative computed tomography (QCT), in which a calibration phantom is used during image acquisition to improve the estimation of BMD. Since model accuracy is dependent on the methods used in the calculation of BMD and density-mechanical property relationships, it is important to use relationships developed for the same anatomical location and using the same scanner settings, as these may impact model accuracy. The purpose of this literature review is to report the relationships used in the conversion of QCT equivalent density measures to ash, apparent, and/or tissue densities in recent finite element (FE) studies used in common density-modulus relationships. For studies reporting experimental validation, the validation metrics and results are presented.
  
  
  RESULTS
  Of the studies reviewed, 29% reported the use of a dipotassium phosphate (K2HPO4) phantom, 47% a hydroxyapatite (HA) phantom, 13% did not report phantom type, 7% reported use of both K2HPO4and HA phantoms, and 4% alternate phantom types. Scanner type and/or settings were omitted or partially reported in 31% of studies. The majority of studies used densitometric and/or density-modulus relationships derived from different anatomical locations scanned in different scanners with different scanner settings. The methods used to derive various densitometric relationships are reported and recommendations are provided toward the standardization of reporting metrics.
  
  
  CONCLUSIONS
  This review assessed the current state of QCT-based FE modeling with use of clinical scanners. It was found that previously developed densitometric relationships vary by anatomical location, scanner type and settings. Reporting of all parameters used when referring to previously developed relationships, or in the development of new relationships, may increase the accuracy and repeatability of future FE models.
authors.affiliation: Graduate Program in Biomedical Engineering, The University of Western Ontario, 1151 Richmond St, London, ON, Canada. nknowle@uwo.ca.|Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON, Canada. nknowle@uwo.ca.|Collaborative Training Program in Musculoskeletal Health Research, and Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON, Canada. nknowle@uwo.ca.
authors.forename: Nikolas K
authors.initials: NK
authors.lastname: Knowles
authors.affiliation: Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON, Canada.|Collaborative Training Program in Musculoskeletal Health Research, and Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON, Canada.|Department of Mechanical and Materials Engineering, The University of Western Ontario, 1151 Richmond St, London, ON, Canada.
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Reeves
authors.affiliation: Graduate Program in Biomedical Engineering, The University of Western Ontario, 1151 Richmond St, London, ON, Canada.|Roth|McFarlane Hand and Upper Limb Centre, Surgical Mechatronics Laboratory, St. Josephs Health Care, 268 Grosvenor St, London, ON, Canada.|Collaborative Training Program in Musculoskeletal Health Research, and Bone and Joint Institute, The University of Western Ontario, 1151 Richmond St, London, ON, Canada.
authors.forename: Louis M
authors.initials: LM
authors.lastname: Ferreira
keywords: Bone density; Finite element analysis; Mechanical properties; QCT