Using an IBM Blue Gene/L supercomputer, scientists of the ETH Zurich (Swiss Federal Institute of Technology) and the IBM Zurich Research Laboratory demonstrated the most extensive simulation yet of real human bone structures, providing doctors with a ''high-definition'' view of fragility or strength of bones they never had before. This achievement could lead to better clinical tools to improve the diagnosis and treatment of osteoporosis, a widespread disease that affects 1 in 3 women and 1 in 5 men over the age of 50.1
The early detection of osteoporosis is crucial in order to prevent its progress. This breakthrough simulation could greatly enhance a clinician's ability to better treat fractures and analyze and detect osteoporotic fragility, in order to take preventative measures before osteoporosis advances in patients.
|Photo: ETH Zurich, IBM Research|
Researchers of ETH Zurich and the IBM Zurich Research Laboratory have demonstrated the most extensive simulations of a real human bone structure ever achieved. In order to analyze bone strength, the researchers used massively parallel simulations to obtain a ''heat map'' of strain, which changes with the load applied to the bone. The image shows the effective strain on a 5 by 5 by 5 mm human vertebra specimen under a load corresponding to the person's weight when standing. The areas in blue show stronger parts of the bone whereas weaker parts are shown in red. The simulations are based on a high-resolution scan (6 microns) using peripheral quantitative computer tomography (pQCT). The researchers created a very detailed mathematical model that required more that 400 million elements-called "voxels"-in order to capture faithfully the intricate bone microstructure. In the next step, researchers computed the strain on the bone by applying different loads that simulate real-life conditions. The specimen in this image shows a healthy human bone.
Osteoporosis is the most widespread bone disease worldwide, affecting 75 million people in the US, Europe and Japan alone, and causing health costs second only to those associated with cardiovascular diseases. Literally ''porous bone'', this disease is characterized by loss of bone density, resulting in a high risk of fractures, and is a major cause of pain, disability and death in older persons.Unfortunately, in many cases, osteoporosis is not diagnosed until a fracture has occurred, but by then the disease is already in an advanced stage, requiring implants or surgical plates to treat or prevent further fractures (source: Prevention and Management of Osteoporosis, WHO Technical Report Series, No. 921.).
Today, osteoporosis is diagnosed by measuring bone mass and density using specialized x-ray or computer tomography techniques?a highly empirical process.
Studies have shown, however, that bone mass measurements are only a moderately accurate way to determine the strength of the bone because bones are not solid structures. Inside the compact outer shell, bones have a sponge-like center. This complex microstructure accounts for the bone's capability to bear loads and therefore represents a better indicator of a bone's true strength.
Aiming for an accurate, powerful and fast method to automate the analysis of bone strength, scientists of the Departments of Mechanical and Process Engineering and Computer Science at ETH Zurich teamed up with supercomputing experts of IBM's Zurich Research Laboratory. The breakthrough method they developed combines density measurements with a large-scale mechanical analysis of the inner-bone microstructure.
Using large-scale, massively parallel simulations, the researchers were able to obtain a dynamic ''heat map'' of strain, which changes with the load applied to the bone. This map shows the clinician exactly where and under what load a bone is likely to fracture.
''Knowing when and where a bone is likely to fracture, a clinician can also detect osteoporotic damage more precisely and, by adjusting a surgical plate appropriately, can determine its optimal location,'' explains Dr. Costas Bekas of IBM's Computational Sciences team in Zurich. ''This work is an excellent example of the dramatic potential that supercomputers can have for our everyday lives.''
Utilising the massively large-scale capabilities of the 8-rack IBM Blue Gene/L supercomputer, the research team was able to conduct the first simulations on a 5 by 5 mm specimen of real bone. In just 20 minutes of computing time, the supercomputer simulation generated 90 Gigabytes of output data.
|Photo: ETH Zurich|
This computer tomography (CT) shows a healthy bone (left) and a fragile, osteoporotic bone (right). Such CTs provide detailed information obout bone structure and are the basis of today's analysis of bone strength and fracture risk in diseases such as osteoporosis. However, they do not take into account the microstructure of the bone, which contributes significantly to the load-bearing capacity of the human skeleton. By coupling CT scans with an analysis of the microstructural strain, researchers aim to improve individual fracture risk prediction, which is important in the diagnosis and treatment of osteoporosis.
''It is this combination of increased speed and size that will allow solving clinically relevant cases in acceptable time and unprecedented detail,'' says Professor Ralph Müller, the director of the Institute for Biomechanics at ETH Zurich.
''Ten years from now, the performance of today's supercomputers will become available in desktop systems, making such simulations of bone strength a routine practice in computer tomography,'' predicts Dr. Alessandro Curioni, manager of the Computational Sciences group at IBM's Zurich Research Laboratory.
Professor Peter Arbenz of the Institute of Computational Science, who initiated the collaboration among the involved groups, explains that state of the art numerical algorithms were also necessary to solve these extremely large problems in this surprisingly short time. This work is the first fundamental step towards a clinical use of large scale bone simulations. ''We are at the beginning of an exciting journey and we need to further continue this line of research in order to achieve this goal," he states.
In future work, IBM and ETH scientists plan to aim to advance their simulation techniques to go beyond the calculation of static bone strength and to be able to simulate the actual formation of the fractures for individual patients, thereby taking another step towards achieving a fast, reliable and early detection of people with high fracture risk.
The work ''Extreme Scalability Challenges in Analyses of Human Bone Structures'' by ETH scientists Peter Arbenz, Cyril Flaig, Harry van Lenthe, Ralph Mueller, Andreas Wirth and ZRL researchers Costas Bekas and Alessandro Curioni was presented at the IACM/ECCOMAS 2008 conference in Venice, Italy, on July 2.
ETH Zurich (Swiss Federal Institute of Technology) has a student body of 14,000 students from 80 nations. Nearly 360 professors teach mainly in engineering sciences and architecture, system-oriented sciences, mathematics and natural sciences, as well as carry out research that is highly valued worldwide. On a yearly basis, ETH Zurich applies for 80-100 patents and directly supports the founding of up to 20 spin-off companies. Distinguished by the successes of 21 Nobel laureates, and with members in the IPCC (Intergovernmental Panel for Climate Control) that was awarded the 2007 Nobel Peace Prize, ETH Zurich is committed to providing its students with unparalleled education and outstanding leadership skills.
The IBM Zurich Research Laboratory is the European branch of IBM Research. This worldwide network of more than 3500 employees in eight laboratories around the globe is the largest industrial IT research organization in the world. ZRL, which was established in 1956, currently employs some 330 persons, representing more than 30 nationalities. ZRL's spectrum of research activities includes nanoscience, future chip technology, supercomputing, advanced storage and server technologies, security and privacy, risk and compliance, as well as business optimization and transformation. World-class research and outstanding scientific achievements-most notably two Nobel Prizes-are associated with the Zurich Lab.