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Dual-Energy X-ray Absorptiometry (DEXA) as an Instrument for Assessing Bone Mineral Density in Historic Human Remains / FREDERICK EVANS

Swansea University Author: FREDERICK EVANS

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Abstract

Dual-energy X-ray absorptiometry (DEXA) is the gold standard, non-invasive method for the measurement of bone mineral density (BMD). DEXA measures BMD using two X-ray beams of different energies. These beams are attenuated differently by bone and soft tissue, allowing for the determination of BMD. D...

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Published: Swansea, Wales, UK 2023
Institution: Swansea University
Degree level: Master of Research
Degree name: MSc by Research
Supervisor: Owen, N; Heffernan, S
URI: https://cronfa.swan.ac.uk/Record/cronfa65547
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Abstract: Dual-energy X-ray absorptiometry (DEXA) is the gold standard, non-invasive method for the measurement of bone mineral density (BMD). DEXA measures BMD using two X-ray beams of different energies. These beams are attenuated differently by bone and soft tissue, allowing for the determination of BMD. DEXA requires the presence of soft tissue and bone to measure BMD, but if a soft tissue proxy (STP), such as rice or gelatin, is used - DEXA can be used to scan human remains,specifically bones. The purpose of this study was twofold: develop a criterion method to measure BMD, using DEXA on historical human remains, then use the criterion method to investigate bilateral asymmetry and agreement (test re-test reliability) in a sample of historic human remains, specifically paired radii from the Mary Rose Trust’s collection of fairly complete skeletons (FCS). The study developed a criterion method initially, by testing the efficacy, in terms of reliability, of using a suspension bracket to position the radius in a consistent position. Machine capability was tested by DEXA scanning one radius 16 times without moving it and using these values to calculate precision error. Method capability was tested by scanning one radius 16 times, removing it and replacing between scans, and using these values to calculate precision error. Once the optimum method of positioning samples was established, the optimum STP was determined. To determine optimum STP, the machine capability of dry rice was compared to that of differing concentrations of gelatin. Upondetermination of the criterion method for measuring BMD using DEXA on historic human remains, agreement and bilateral asymmetry of BMD was measured in a population of 20 pairs of radii. This was done for samples in pronated and supinated orientation. Significant differences were tested for between dominant and nondominant arm BMD (dominant arm being assumed as the arm with higher BMD). The criterion method for measurement of BMD using DEXA within historic human remains was found to be the use of a suspension bracket to position the sample with 11.7% gelatin blocks as an STP. This method resulted in a mean ± standard error of the mean (SEM) of 0.751±0.00028 mass/cm2 (±0.037%), compared to the rice bed method (no suspension bracket and dry rice as an STP) which resulted in a mean ± SEM of 0.795±0.0015 mass/cm2 (±0.19%). Once established, the criterion method was applied to the full sample of 20 pairs of radii to establish reliability and bilateralasymmetry. Reliability was assessed using Bland and Altman limits of agreement iii (LOA) analysis which produced a sample mean = 0.762 mass/cm2, a systematic bias = 0.002 mass/cm2 (0.03%), upper LOA = 0.003 mass/cm2 (0.39%) and lower LOA = -0.0026 mass/cm2 (-0.34%). Significant differences were observed in pronated BMD, supinated BMD, and combined BMD values between dominant/non-dominant arm radii (p < 0.05, pronated: p = 0.018, supinated: p = 0.019, combined: p = 0.018). Of the 20 pairs of radii compared, 5 had bilateral asymmetry of BMD > 10% with the largest difference being 46.2%. To conclude, the criterion method for measuring BMD using DEXA on historic human remains is to position samples using a suspension bracket and use 11.7% gelatin blocks as an STP. Additionally, significant bilateral asymmetry was observed between dominant and non-dominant arm BMD in a population of 20 pairs of radii.
Item Description: Part of this thesis has been redacted to protect personal information
Keywords: Sport Science, Biomechanics, Dual-Energy X-ray Absorptiometry (DEXA), Historic Remains
College: College of Engineering

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