Optical Imaging Advancements Enable Better Diagnoses
Optical frequency domain imaging will shine a brighter light on acute coronary thrombosis.
Imaging is a vital part of diagnosing and treating patients, particularly when using non-invasive treatment methods. Guillermo J. Tearney, MD, PhD, an Associate Professor of Pathology at the Massachusetts General Hospital in Boston, discussed exciting imaging options and what they offer the field of cardiology.
Evaluation of observations
Developing technology to understand a disease before an acute coronary event happens is important, he said in an interview with TCT-TV. Cardiologists must have a thorough multifactorial understanding of vulnerable plaque and its structural anomalies, composite changes and biomechanical properties that may confer risk of developing acute coronary thrombosis, Tearney said.
Assessing the biomechanical constituents of lesions to determine their relationship to acute coronary events requires the proper tools, he said. High-resolution, optical frequency domain imaging on a 10-µm scale allows a cardiologist to see individual cells such as macrophages and track these cells over time in patients.
The research mission of Tearney’s institution is to develop and test methods that use light to increase the understanding of disease and improve medical practice.
Imaging diagnostics
Optical coherence tomography (OCT), for example, can provide such clarity that in one study of patients with acute coronary syndromes, OCT images were able to detect an elevated level of macrophages in the coronary arteries compared with the coronary lesions. At the plaque rupture sites, there was also an elevated level of macrophages, suggesting a correlation between the sites because the inflammation had spread from one location to another.
Optical frequency domain imaging is derived from OCT. Optical frequency domain imaging uses light the way ultrasound uses sound waves. The light-based technology has a resolution down to 10 or fewer microns. A cross section clearly depicts the arterial wall and the individual cells. This makes measuring the cap thickness of fewer than 20 microns an easier task.
“Optical frequency domain imaging is faster to process than OCT and therefore is useful in the clinical setting. It is the detection of the subsystem that has set this imaging method aside from OCT,” Tearny said.
From 2002 to 2003, Tearney’s institution began using optical frequency domain imaging more regularly than other methods. The imaging technology allows the physician to see different layers of vessels and 3-D volumes of structures.
Ramen spectroscopy is another method commonly used. It directs light into tissue, scattering it on wavelengths that are mainly of equal size. A miniscule amount of light, however, couples with molecules in the tissue, allowing these wavelengths to scatter with a slightly different energy.
Physicians are then able to look at the spectra and determine chemical composition of the tissue.