Optical Coherence Tomography Used to Image Pain Management in Labor and Diabetic Retinopathy and Glaucoma

The research was presented at CLEO 2014, the Conference on Lasers and Electro-Optics, which was held June 8–13, 2014, in San Jose (CA, USA). OCT uses scattered “echoes” or reflections of light waves to create high-resolution images of biologic tissues, similar to ultrasound imaging but with one order of magnitude improvement in the resolution. Ophthalmologists have long been using OCT to study the retina. More recently, OCT has been applied to a range of other clinical specialties, including cardiology, where it is used to examine the formation of plaques in coronary arteries in situ, and oncology for early cancer detection and staging in the gastrointestinal and urogenital tract.

Bioengineer Dr. Yu Chen, from the University of Maryland (College Park, USA), and his colleagues have developed a way to integrate an OCT device with an 18-gauge epidural needle. Epidural administration, Dr. Chen noted, is traditionally performed blindly, using anatomic landmarks. However, the investigators newly miniaturized handheld device lets anesthesiologists see tissue from the perspective of the tip of the epidural needle, which could help doctors to deliver spinal anesthetic to patients with less pain and fewer complications.

“Due to lack of visual feedback, failure rates are often high, leading to multiple needle insertions,” Dr. Chen said. Side effects of these failures can include trauma to blood vessels and punctures in the dura, the outermost membrane surrounding the brain and spinal cord. “An OCT forward-imaging probe can provide anesthesiologists with real-time visualization of the microarchitecture of tissues and important landmarks, and thus could significantly improve the accuracy and the safety of the needle-based procedure,” Dr. Chen said.

The researchers have been successful in testing needle-guidance research on pig swine samples and hope to conduct a preclinical study of the device by 2015.

In another study presented at the conference June 12, investigators from the University of California, Davis (UC Davis; USA), led by biomedical engineer Dr. Vivek Srinivasan, have shown how OCT can simultaneously measure blood flow and blood oxygenation in vessels, without the need for contrast agents.

OCT, similar to ultrasound, can provide structural information, but it can also be used to determine flow rates and for angiography, visualizing the interior of blood vessels, according to Shau Poh Chong, a postdoctoral researcher in the Srinivasan lab. “Conventional pulse oximetry measures oxygen saturation using transmitted light,” Dr. Chong stated. “Performing these measurements quantitatively with reflected light has traditionally been difficult due to the unknown distance traveled by the light through scattering tissue.”

OCT directly determines the distance that light travels. Until now, however, it was challenging to use OCT to gauge oxygen saturation in blood, due to additional modeling errors introduced by light scattering. At visible wavelengths, scattering is much lower relative to blood absorption than at infrared wavelengths, where OCT is typically performed. The OCT system developed in the Srinivasan lab uses broadband visible light to measure the amounts of both oxygenated and deoxygenated hemoglobin, the oxygen-carrying protein of blood, thus revealing oxygen saturation levels. In addition, the team developed new methods to further reduce modeling errors caused by light scattering.

“The broad set of measurements provided by the system, including angiography, oximetry, and red blood cell flow rates enables the direct assessment of tissue oxygen metabolism, which is essential for understanding the evolution of oxygen supply and demand in numerous disease models,” Dr. Chong concluded. “In the future, these techniques could be applied to study metabolic changes in diseases that affect the human retina, such as diabetic retinopathy and glaucoma.”

Related Links:
University of Maryland
University of California, Davis