Soft tissue variations influence HR-pQCT density measurements in a spatially dependent manner

Wu, Po-hung<sup>1</sup>; Gupta, Tanvi<sup>1</sup>; Chang, Hanling<sup>2,3</sup>; Petrenko, Dimitry<sup>2,3</sup>; Schafer, Anne<sup>2,3,4</sup>; Kazakia, Galateia<sup>1</sup>

Affiliations

¹Department of Radiology and Biomedical Imaging at China Basin, University of California – San Francisco, 185 Berry Street, Suite 190, Lobby 6, San Francisco, CA 94107, USA

²Department of Medicine, University of California – San Francisco, 505 Parnassus Avenue, San Francisco, CA 94143, USA

³Endocrine Research Unit, San Francisco Veterans Affairs Health Care System, 4150 Clement St, San Francisco, CA 94121, USA

⁴Department of Epidemiology and Biostatistics, University of California -San Francisco, 550 16th St 2nd floor, San Francisco, CA 94158, USA

Abstract and keywords

Objective: Significant weight loss following treatments for obesity undermines bone metabolism and increases bone turnover and fracture incidence. High resolution peripheral quantitative computed tomography (HR-pQCT) is widely used in skeletal heath assessment research to provide noninvasive bone parameter measurement (e.g. volumetric bone mineral density (vBMD)) with minimal radiation exposure. However, variation in body composition among study groups or longitudinal variations within individuals undergoing significant weight change will generate artifacts and errors in HR-pQCT data. The purpose of this study is to determine the influence of these artifacts on the measurement of vBMD.

Methods: We designed a custom-made hydroxyapatite (HA)-polymer phantom surrounded by layers of reusable gel pack and hydrogenated fat to mimic the distal tibia and the surrounding lean and fat tissue. Four different thicknesses of fat were used to mimic the soft tissue of increasingly overweight individuals. We then evaluated how a change in soft tissue thickness influenced image quality and vBMD quantification within total, trabecular, and cortical bone compartments. Based on these data, we applied a data correction to previously acquired clinical data in a cohort of gastric bypass patients.

Results: In the phantom measurements, total, trabecular, and cortical vBMD increased as soft tissue thickness decreased. The impact of soft tissue thickness on vBMD varied by anatomic quadrant. When applying the soft tissue data correction to a set of clinical data, we found that soft tissue reduction following bariatric surgery can lead to a clinically significant underestimation of bone loss in longitudinal data, and that the effect is most severe in the cortical compartment.

Conclusion: HR-pQCT-based vBMD measurement accuracy is influenced by soft tissue thickness and is spatially inhomogeneous. Our results suggest that variations in soft tissue thickness must be considered in HR-pQCT studies, particularly in studies enrolling cohorts with differing body composition or in studies of longitudinal weight change.

Keywords: Bone mineral density; HR-pQCT; Obesity; Beam-hardening; Scatter; Bariatric surgery; Weight loss

Links

DOI: 10.1016/j.bone.2020.115505

PubMed: 32599223

WoS: 000557876000033

History

Received: 2020-03-10

Revised: 2020-06-11

Accepted: 2020-06-11

Online: 2020-06-27

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Cited By (1)

Year	Entry
2021	Whittier DEW. The Assessment of Fragility Fracture Risk Using HR-PQCT as a Novel Tool for Diagnosis of Osteoporosis [PhD thesis]. Calgary, AB: University of Calgary; August 2021.