The National Institute of Standards and Technology (NIST) has awarded Robert Chang, Ph.D., an assistant professor in the Department of Mechanical Engineering at the Stevens Institute of Technology (Hoboken, NJ), with a grant to develop a standard calibration tool for depth-resolving optical imaging modalities. Changâs Biomodeling and Biomeasurement Lab is working to advance the technology with a standard calibration tool so that new optical imaging devices can be applied to measure depth with precision in clinical settings.
"Providing accurate depth resolution standards will ensure confidence in high-resolution medical imaging modalities capable of detecting tumors at much earlier stages of development," says Dr. Frank Fisher, Interim Director of the Department of Mechanical Engineering. "These standards are crucial for the establishment of cross-validated optical measurements necessary for future technological innovation in the screening and diagnosis of many human disease states."
Just as there is a need to routinely zero a scale for quantitative weight measurements, scientists need to calibrate microscopes so that they can produce accurate and precise spatial measurements. Established standards have made lateral optical imaging devices extremely precise, widely accepted clinical tools, but axial (depth) optical imaging devices have no widely accepted standard. Chang has therefore proposed the design and fabrication of a tissue phantom (or tissue-simulating object) to serve as a test target for the calibration of promising depth-resolving optical imaging modalities, including optical coherence tomography (OCT) and near-infrared (NIR) fluorescence imaging.
The establishment of a calibration standard is crucial for fields like ophthalmology, in which quantitative thickness measurements of reflective eye tissue layers using OCT can aid the diagnosis and treatment of numerous diseases. Doctors can use OCT to get a cross-sectional image of retina and look for microstructural abnormalities down to the micron scale. Doctors can also check the size and shape of the cornea to determine if a patient is a good candidate for LASIK surgery.
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Micron-scale depth imaging with OCT can also help in the study of certain cancers. Materials have different refractive indexes and scatter light differently. Doctors know how cancer cells and healthy cells differ in reflective index, so they can use OCT to detect cancerous cells. Endoscopic-based OCT has also been used to study the initial stages of the invasion of mucosal layers into submucosal layers of the gastrointestinal lining, which can be an early indicator of colon cancer. The same principle can also be applied for earlier detection of atherosclerosis, a risk factor for heart attacks in which fatty material accumulates on blood vessel walls. The fatty materials begin to cause protrusions at minute scales, and OCT can detect these abnormalities at early stages.
Chang received a National Research Council (NRC) Research Fellowship to work as a biomechanical engineer in the Physical Measurement Laboratory at the National Institute of Standards and Technology (NIST), where he has engineered novel tissue models towards the validation of depth-resolving optical modalities such as OCT and confocal microscopy for dimensional metrology, as well as hyperspectral imaging for wound healing applications and surgical scenes. His research interests include biofabrication, biomodeling, and measurement of biotissues.
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