Evaluation of patient tissue selection methods for deriving equivalent density calibration for femoral bone quantitative CT analyses

Winsor, C.; Li, X.; Qasim, M.; Henak, C. R.; Pickhardt, P. J.; Ploeg, H.; Viceconti, M.

Affiliations

¹Mechanical Engineering, University of Wisconsin, USA

²Mechanical Engineering, University of Sheffield, UK

³INSIGNEO Institute for in silico Medicine, University of Sheffield, UK

⁴Radiology, University of Wisconsin, USA

⁵Mechanical and Materials Engineering, Queen’s University, Canada

⁶Department of Industrial Engineering, Alma Mater Studiorum – University of Bologna, Italy

⁷Medical Technology Lab, IRCCS Rizzoli Orthopaedic Institute, Italy

Abstract and keywords

Osteoporosis affects an increasing number of people every year and patient specific finite element analysis of the femur has been proposed to identify patients that could benefit from preventative treatment. The aim of this study was to demonstrate, verify, and validate an objective process for selecting tissues for use as the basis of phantomless calibration to enable patient specific finite element analysis derived hip fracture risk prediction. Retrospective reanalysis of patient computed tomography (CT) scans has the potential to yield insights into more accurate prediction of osteoporotic fracture. Bone mineral density (BMD) specific calibration scans are not typically captured during routine clinical practice. Tissue-based BMD calibration can therefore empower the retrospective study of patient CT scans captured during routine clinical practice. Together the method for selecting tissues as the basis for phantomless calibration coupled with the post-processing steps for deriving a calibration equation using the selected tissues provide an estimation of quantitative equivalent density results derived using calibration phantoms. Patient tissues from a retrospective cohort of 211 patients were evaluated. The best phantomless calibration resulted in a femoral strength (FS) [N] bias of 0.069 ± 0.07% over FS derived from inline calibration and a BMD [kg/cm³] bias of 0.038 ± 0.037% over BMD derived from inline calibration. The phantomless calibration slope for the best method presented was within the range of patient specific calibration curves available for comparison and demonstrated a small bias of 0.028 ± 0.054 HU/(mg/cm³), assuming the Mindways Model 3 BMD inline calibration phantom as the gold standard. The presented method of estimating a calibration equation from tissues showed promise for CT-based femoral fracture analyses of retrospective cohorts without readily available calibration data.

Keywords: Bone strength; Finite element analysis; Phantomless calibration; Internal tissue calibration; Bone mineral density; Hip fractures; Osteoporosis

Links

DOI: 10.1016/j.bone.2020.115759

PubMed: 33212317

WoS: 000604736100006

History

Received: 2020-07-28

Revised: 2020-11-13

Accepted: 2020-11-13

Online: 2020-11-17

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Cited By (4)

Year	Entry
2022	Bartenschlager S, Dankerl P, Chaudry O, Uder M, Engelke K. BMD accuracy errors specific to phantomless calibration of CT scans of the lumbar spine. Bone. April 2022;157:116304.
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2022	Winsor C. Femoral Bone Quantitative CT Analyses With Internal Tissue-Based Phantomless Densitometric CT Calibration [PhD thesis]. University of Wisconsin – Madison; 2022.