OCT is making epidurals less painful
Researchers have successfully combined optical coherence tomography (OCT) with other instruments in order to create a safer, less painful, and more effective care for women in labour or suffering from diabetic glaucoma and retinopathy.
Bioengineer Yu Chen of the University of Maryland and his colleagues have developed a way to integrate an OCT device with an 18-gauge epidural needle. Epidural administration, Chen notes, is traditionally done blindly, using anatomical landmarks. But the team’s newly miniaturised handheld device lets anaesthesiologists see tissue from the perspective of the tip of the epidural needle, which could help doctors to deliver spinal anaesthetic to patients with less pain and fewer complications.
‘Due to lack of visual feedback, failure rates are often high, leading to multiple needle insertions,’ he says. 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.
OCT uses scattered reflections of light waves to produce high-resolution images of biological tissues, similar to ultrasound imaging but with one order of magnitude improvement in the resolution. Ophthalmologists have been using OCT to examine the retina for years.
More recently, OCT has been applied to a number of other clinical specialties, including oncology for early cancer detection and staging in the gastrointestinal and urogenital tract as well as in cardiology, where it is used to study the formation of plaques in coronary arteries in situ.
A team at the University of California, Davis, led by biomedical engineer Vivek Srinivasan has shown how OCT can simultaneously measure blood flow and blood oxygenation in vessels, without the need for contrast agents. OCT directly determines the distance that light travels. Until now it was difficult to use OCT to measure oxygen saturation in blood, due to additional modelling 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 haemoglobin, 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.
Both research projects will be presented at CLEO 2014, being held 8-13 June in San Jose, California, USA.