■ FUNDAMENTAL PRINCIPLE
Bones mainly serve as supporting columns which transfer body weight, or levers which permit the various motions of the body. In daily activities, bones are subject to a variety of axial, bending, and torsional loads which cause mechanical stresses. Wolff(1892) stated that the functional adaptation of bones reorients the trabeculae, so that they align with the new principal stress trajectories when the environmental loads on the bone are changed by trauma or a life pattern. He also suggested that the bone obtains the “maximum” mechanical efficiency with the “minimum” mass; this theory is well known as Wolff’s law. Based on this theory, a bone structure is referred as an “optimal” structure.
■ RESEARCH AREA
- The goal of this research group is to investigate the governing principles of bone metabolism and to apply them to biomechanical and biomedical engineering through implementing design optimization.
- First, biomechanical simulation focuses on the development of computational bone remodeling simulations which phenomenologically estimate bone microstructure alternation.
- Second, skeletal image processing proposes a new resolution enhancement method that can reconstruct high-resolution skeletal images from low-resolution images based on topology optimization.
- Third, biomimetic structural design applies the optimal characteristic of a bone microstructure to lightweight designs for automobile, railway, and aerospace vehicles.
■ AREA 1: BIOMECHANICAL SIMULATION
- Osteoporosis is a metabolic bone disease which degrades a bone microstructure and therefore increases bone fragility. Osteoporotic fractures lead to ever-decreasing mobility and quality of life as well as growing financial costs. If the morphological changes of a bone structure can be estimated, osteoporosis can be properly managed with clinical treatments,
- This research develops a computational bone remodeling simulation which can reflect the morphological changes in a bone structure over time. The proposed method can contribute to the development of early diagnosis tool for osteoporosis and patient-specific models for various clinical purposes.
- * I. G. Jang and I. Y. Kim, “Computational study of Wolff’s law with trabecular architecture in the human proximal femur using topology optimization,” J. Biomech., vol. 41, no. 11, pp. 2353-2361, 2008.
* I. G. Jang and I. Y. Kim, “Computational simulation of trabecular adaptation progress in human proximal femur during growth.,” J. Biomech., vol. 42, no. 5, pp. 573-80, 2009.
* Y. H. Lee, Y. Kim, J. J. Kim, and I. G. Jang, “Homeostasis-based aging model for trabecular changes and its correlation with age-matched bone mineral densities and radiographs,” Eur. J. Radiol., 2015.
■ AREA 2: SKELETAL IMAGE PROCESSING
- Clinical high-resolution skeletal images which can represent a bone microstructure are essential for accurate bone strength assessment. However, they are still unavailable because the current in vivo high-resolution imaging modalities have a limited resolution due to high radiation doses, low signal-to-noise ratios, and/or long scan times. As an alternative, computational bone remodeling simulation proves that it can reconstruct a bone microstructure. In particular, topology optimization-based simulation successfully reconstructs a bone a LR image using topology optimization based on Wolff’s law. Note that topology optimization is mathematically matched well with phenomenological bone remodeling simulation.
- This research proposes a novel image resolution enhancement method that can reconstruct a high-resolution image from a low-resolution one in order to improve the accuracy of bone strength assessment. This will be a key technique to bridge a gap in current translational medicine.
- * J. J. Kim and I. G. Jang, “Image resolution enhancement for healthy weight-bearing bones based on topology optimization.,” J. Biomech., 2016, doi: 10.1016/j.jbiomech.2016.06.012.
* J. J. Kim, Y, Kim and I. G. Jang, “Estimation of Local Bone Loads for Volumes of Interest within Cancellous Metaphyses.,” J. Biomech. Eng., vol. 138, no. 7, pp. 071004 2016
■ AREA 3: BIOMIMETIC STRUCTURAL DESIGN
- Due to the reinforced environmental regulation, automotive industry has recently focused on developing a lightweight design, thereby improving fuel efficiency and reducing emissions. The lightweight design can be effectively and efficiently determined by mimicking a bone structure which has the maximum mechanical efficiency with the minimum mass. It is interesting to note that a metallic microlattice, which is inspired by a bone micro structure, was recently introduced as a ultralight structure.
- This research aims at a lightweight design for vehicular components by reflecting the structural characteristics of bones. For the purpose, topology optimization is conducted in order to generate a porous, fine structure under the given loading conditions. With the aid of state-of-the-arts additive manufacturing, this research can contribute to various fields such as automotive, railway, and aerospace as a fundamental research for lightweight designs.