A Spatio-Temporal Ageing Atlas of the Proximal Femur.

Mohsen Farzi,Alejandro F Frangi,Richard Eastell,Eugene Mccloskey,Nicholas Harvey,J Mark Wilkinson,Jose M Pozo

doi:10.1109/tmi.2019.2945219

Abstract

Osteoporosis is an age-associated disease characterised by low bone mineral density (BMD) and micro-architectural deterioration leading to enhanced fracture risk. Conventional dual-energy X-ray absorptiometry (DXA) analysis has facilitated our understanding of BMD reduction in specific regions of interest (ROIs) within the femur, but cannot resolve spatial BMD patterns nor reflect age-related changes in bone microarchitecture due to its inherent averaging of pixel BMD values into large ROIs. To address these limitations and develop a comprehensive model of involutional bone loss, this paper presents a fully automatic pipeline to build a spatio-temporal atlas of ageing bone in the proximal femur. A new technique, termed DXA region free analysis (DXA RFA), is proposed to eliminate morphological variation between DXA scans by warping each image into a reference template. To construct the atlas, we use unprocessed DXA data from Caucasian women aged 20-97 years participating in three cohort studies in Western Europe ( ,000). A novel calibration procedure, termed quantile matching regression, is proposed to integrate data from different DXA manufacturers. Pixel-wise BMD evolution with ageing was modelled using smooth quantile curves. This technique enables characterisation of spatially-complex BMD change patterns with ageing, visualised using heat-maps. Furthermore, quantile curves plotted at different pixel coordinates showed consistently different rates of bone loss at different regions within the femoral neck. Given the close relationship between spatio-temporal bone loss and osteoporotic fracture, improved understanding of the bone ageing process could lead to enhanced prognostic, preventive and therapeutic strategies for the disease.

Highlights

A GEING is associated with a gradual and progressive bone loss, which predisposes to osteoporosis
In conventional Dual-energy X-ray Absorptiometry (DXA) analysis, bone mineral density (BMD) data is acquired at the individual pixel level but at the analysis stage these values are averaged in a priori specified regions of interest (ROIs) to compensate for shape variation between scans (Fig. 1)
This paper offers solutions to these challenges: To maintain fidelity to high-resolution pixel BMD values, we have previously proposed a region free analysis (RFA) approach and demonstrated its application to analysing periprosthetic BMD changes for patients who received a hip prosthesis [10]–[12]

Summary

Introduction

A GEING is associated with a gradual and progressive bone loss, which predisposes to osteoporosis. Osteoporosis is a bone disease characterised by low bone mass and microarchitectural deterioration, and improving the understanding of the bone ageing process interests the osteoporosis research community [1], [2]. To facilitate this understanding, we propose a method to develop a spatio-temporal atlas of ageing bone in the femur. Developing a comprehensive model of involutional bone loss is a challenging task This requires a robust and accurate quantification technique for bone mineral density (BMD) measurement and its spatial distribution. Data averaging reduces the ability of the technique to quantitate local variation in textural BMD patterns of clinical relevance to disease progression with ageing

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