Any child who has ever put a hand over a flashlight and seen the way the light shines through his skin can understand the basics of optical tomographic imaging (OTI). This relatively new technology relies on laser light and biomedical engineering expertise to measure the light that passes through tissues.
Columbia University Medical Center researchers who are conducting clinical trials of the technology say the approach holds promise for early detection of rheumatoid arthritis, among other disorders.
"Optical tomographic imaging may be able to detect rheumatoid arthritis earlier than other methods, such as X-ray imaging, because optical imaging is more sensitive to early changes that especially affect the joint fluid," says Andreas Hielscher, Ph.D., associate professor of biomedical engineering and radiology. Rheumatoid arthritis, which afflicts more than 6 million Americans, is a painful disease that causes inflammation and damage to the joints.
But that's just one example. OTI has the potential to fill some important gaps in medical imaging in the areas of breast cancer, stroke, functional brain imaging, and bedside imaging of newborns in intensive care units, adds Dr. Hielscher, who holds a doctorate in electrical and computer engineering.
Increasingly, radiology researchers are accepting optical imaging as a mainstream imaging technology along with the more established radiography, magnetic resonance imaging (MRI), ultrasound, and CT scanning, Dr. Hielscher says. Besides the small size of the machines, optical imaging's main advantages are its speed and relative lower cost. Optical technology systems cost only about a fifth of an MRI system yet provide images more quickly than MRI machines.
Dr. Hielscher and his colleagues use a machine that looks like a wheel with spokes to test for arthritis in a finger joint. The spokes are actually optical fibers that deliver light to the finger, which is placed in a hole in the middle. Using another set of optical fibers also in contact with the finger, the researchers measure the transmitted light intensities and, using computer algorithms they have developed, calculate cross-sectional views of the joints.
In an ongoing clinical study, they are comparing the optical imaging findings with those from MRI, ultrasound, and X-ray imaging to assess the performance of their optical system. Recently they analyzed OTI data from more than 30 patients and found good correlation with ultrasound and MRI findings. But more work is necessary to clearly prove clinical utility, he says.
With funds from a new $1.3 million NIH grant, Dr. Hielscher plans to develop a combined optical-MRI imaging system. He and colleagues at Columbia and SUNY Downstate Medical Center will use the equipment on mice and rats to study abnormal blood flow processes as they occur in diseases such as epilepsy, cancer, or stroke.
Besides studying disease processes in a controlled environment, the combined imaging equipment potentially could reduce the number of animals needed for research and the cost of research because more data could be gathered from each animal at different stages of the animal's life.
"This is an exciting, less invasive technology that has many possible applications," says Dr. Hielscher, who joined Columbia in 2001 from SUNY Downstate. "We hope to provide a range of early detection options including the use of molecular imaging techniques to detect diseases long before macroscopic, visible pathological changes occur."