Researchers from Duke University have developed a way to use optical coherence tomography (OCT) in hard-to-reach areas of the body such as joints. The method may allow the technique to see use in further surgical and medical applications. The researchers used a rigid borescope, essentially a thin tube of lenses, to deliver the infrared light necessary to perform OCT. Measuring just 4 mm in diameter, the borescope makes the beam delivery portion of the device very slim without sacrificing imaging performance. Researchers used a new endoscopic OCT system to visualize variances in pig cartilage thickness. The image shows a sketch of a femur and processed OCT images with thin regions shown in dark red and thicker regions more yellow and white. Scale bar is 250 μm. Courtesy of Evan T. Jelly, Duke University. “We saw a need for OCT image guidance in arthroscopic surgery, a minimally invasive procedure that uses an endoscope to address joint damage,” said research team leader Evan T. Jelly. “We took the low-cost OCT imaging platform we previously developed and adapted it to meet the requirements of this application.” Working with Duke researcher Adam Wax, Jelly and the research team previously developed OCT systems that are a fraction of the cost of traditional models. To make an OCT system that could be used to assess the health of cartilage in a joint, they created an endoscopic delivery system that uses a prototype rigid borescope to relay the image from the tissue to a fiber optic connection. The instrument’s narrow front viewing section allows it to reach structures and cavities that aren’t accessible with the larger portion of the device that scans the patient. The researchers tested the device by using it to measure the thickness of cartilage in pig knees. The system was able to accurately identify the bone-cartilage interface for samples that were less than 1.1 mm thick. Because pig cartilage is similar to that of humans, the test provided a preliminary idea of how the device might perform when imaging human tissue. “By developing a new, portable, low-cost version of OCT, we show that the success of this imaging approach will no longer be limited to ophthalmology applications,” Jelly said. “With some engineering expertise, this OCT platform can be adapted to fit a wide range of clinical needs.” With further development, the instrument is expected to provide less invasive treatment of joint problems, though the researchers must first show that the device is able to image thicker samples because human cartilage is slightly thicker than pig cartilage. The researchers also plan to improve the ergonomics for use during surgery. The research was published in Optics Letters (www.doi.org/10.1364/OL.44.005590).