초록

Abstract ▼

1. Research Purpose
● Background
Because the proportion of the aged population is increasing worldwide, the health and quality of life of the elderly are currently of great concern in aging societies. Osteoporosis is a skeletal disease caused by the reduction of the bone mineral density (BMD)

1. Research Purpose
● Background
Because the proportion of the aged population is increasing worldwide, the health and quality of life of the elderly are currently of great concern in aging societies. Osteoporosis is a skeletal disease caused by the reduction of the bone mineral density (BMD) and micro-structural deterioration of bone quality (Fig. 1), with a consequent increase in bone fragility and susceptibility to fracture.

It is reported that osteoporosis is responsible for more than 1.5 million fractures per year in the Unites States. The current annual direct cost for the treatment of osteoporotic fractures in US is estimated to be $10-$18 billion and anticipated to at least double by 2020.

● Significance
Because a disconnection in a trabecular network due to osteoporosis is irreversible in nature, it is important to develop a reliable technique for early diagnosis of osteoporosis, which is critical for opportune clinical treatment. Currently, dual energy X-ray Absorptiometry (DXA), which provides the representative areal or volumetric BMD values, is considered as the gold standard for the diagnosis of osteoporosis. World Health Organization (WHO) recommends the T-score below -2.5 as the criteria for osteoporosis. However, recent clinical studies reveal that half of incident fractures occur in women who have T-scores above -2.5. Main reason for misdiagnosis is that BMD is not the sole measure to determine bone strength.

In principle, bone strength can be determined by both bone mass (e.g. BMD) and bone quality (e.g. bone microstructure). It has been reported that BMD comprises only 60–75% of bone strength, whereas bone microstructure can predict up to 94% of bone strength with the aid of finite element analysis (FEA). A recent study reported that a group of patients with fragility fracture have a lower apparent elastic modulus of the volume of interest (VOI) in the trabecular compartment compared to another group without fracture, although the two groups have no difference in BMD T-scores. Thus, the quantitative investigation of bone microstructure is critical for the reliable osteoporosis diagnosis. However, clinical assessments still remain fraught because in vivo skeletal images have a limited resolution to represent a bone microstructure due to excessive radiation doses for CT or low signal-to-noise ratio (SNR) for MRI. For example, the effective radiation dose of a multidetector CT is approximately 3 mSv, which is equivalent to 1.5 years of background radiation.

In order to overcome the aforementioned resolution issue, the PI recently proposed a new paradigm of resolution enhancement for skeletal images using topology optimization. Because topology optimization can determining an optimal structure through systematically and iteratively distributing material in a design domain, it can reconstruct a bone microstructure in the VOI from the low-resolution CT scan data. The PI’s previous research demonstrated the feasibility of topology optimization-based resolution enhancement, but a couple of issues related with phenomenological accuracy and computational cost remain to be resolved for the further clinical applications. Also, more thorough validation should be conducted for further clinical applications.

● Research objectives
The goal of the proposed research is to improve computational efficiency and accuracy in enhancing low-resolution CT scan data and to reconstruct bone microstructures in the VOIs for both numerical and experimental validation. The current clinical imaging devices such as CT and MRI have a limited spatial resolution of approximately 600 μm due to the radiation doses, SNRs, and/or scan times. The proposed method would become a key technique to provide HR skeletal images of 50–100 μm resolution for more accurate diagnoses of osteoporosis.

● Relevance to Khalifa University and UAE
The International Osteoporosis Foundation (IOF) estimated that 24% of the UAE population have osteopenia and 2.5% have osteoporosis based on a recent screening of healthy individuals aged 42. It was recommended by IOF that osteoporosis should be considered a major health problem in the UAE.

The counterpart at KU (Prof. Tae Yeon Kim) has recently proposed the feasibility of highly nonlinear solitary waves (HNSWs) to investigate bone strength. In this research collaboration, as a next step, both numerical and experimental validation will be conducted to measure in vivo bone strength, which can provide essential information on osteoporosis diagnosis. Therefore, this project can set a valuable benchmark for the research at KU and a healthcare issue in the UAE (particularly, Abu Dhabi 2030 Plan) will be further addressed through collaborative activities in this project year.

(출처 : 본문 1. Research Purpose 3p)

목차 Contents

• COVER ... 1
• 1. Research Purpose ... 3
• ■ Background ... 3
• ■ Significance ... 3
• ■ Research objectives ... 4
• ■ Relevance to Khalifa University and UAE ... 4
• 2. Research Target Using Progress Chart ... 5
• 3. Research Method ... 6
• 3.1. Step 1: Preprocessing the CT scan data ... 7
• 3.2. Step 2: Constructing a localized FE model for the volume of interest ... 8
• 3.3. Step 3: Conducting the topology optimization for trabecular bone reconstruction ... 8
• 2.4. Reconstructing bone microstructures from CT scan data for validation ... 10
• 4. Research Results ... 12
• ■ Characteristic pattern ... 12
• ■ Morphometric indices ... 12
• ■ Computational efficiency ... 14
• End of Page ... 18