BackgroundFinite 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.ResultsOf 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 K2HPO4 and 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.ConclusionsThis 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.
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