Optical Coherence Tomography - A New Point Of Care Imaging Tool

Optical Coherence Tomography (OCT) is on the verge of becoming the 6th imaging modality (x-ray, ultrasound, CT, MRI, Nuclear Imaging). Similar to B-mode ultrasound, OCT produces two dimensional, cross-sectional, high resolution images of tissue and microstructure utilizing near infrared light, instead of sound. OCT, marketed in the US and globally as the Niris™ Imaging System from Imalux™ Corporation, produces these images in real-time at the point of care. The spatial resolution is 10 – 20 micrometers, which is near cellular imaging, and approximately 50 to100x better than ultrasound. OCT does not require any coupling medium, unlike ultrasound, since mucosal tissues typically have good intrinsic contrast.

OCT provides a solution to a previously unmet need as physicians can now visualize in real time below the tissue surface at a spatial resolution better than that currently available in point-of-care imaging systems, such as ultrasound. The Niris Imaging System (Figure 1.) depth range of up to 1.6 mm is comparable to the depth of many biopsies, which is the gold standard in the diagnosis of many diseases, including cancer. This depth is adequate to visualize most epithelial linings such as the urinary and gastrointestinal tracts where dysplastic changes begin.

What are some key OCT Applications?
Beginning in the mid-1990's OCT has been experimentally used for multiple medical applications including Barrett's esophagus detection and surveillance, inflammatory bowel diseases and GI cancers, vascular stent and plaque visualization, cervical cancer, bladder cancer, infertility, nerve-sparing radical prostatectomies, ablation therapy, mucositis and vocal cord cancer.

OCT was first used in ophthalmology to visualize structure of both the posterior and anterior chambers of the eye. OCT systems which have FDA clearance for ophthalmic use include products from Zeiss and Ophthalmic Technologies Incorporated. The Niris Imaging System is FDA cleared for visualizing and evaluating human tissue microstructure. Niris also holds CE mark registration for Europe and Therapeutic Goods Administration (TGA) approval which provides market clearance in Australia and New Zealand.

OCT systems (such as the Niris Imaging System) which utilize a miniature imaging probe, can be inserted into the working channel of commercial endoscopes, making surfaces of virtually all internal organs accessible for examination. Niris employs a 2.7 mm outer diameter reusable probe that can be inserted through the working channel of a rigid cystoscope, as well as flexible endoscopes, colonoscopes, and gastroscopes. A thinner probe is in development for use in flexible cystoscopes.

The probe can also be used with a Probe Sheath which provides a sterile barrier during open procedures such as examinations of the oral cavity or cervix.

Endourology may benefit from OCT as an adjunct to cystoscopy and laparoscopy (Figure 2). Studies suggest that OCT-guided TURBT can virtually eliminate local recurrences and minimize the amount of normal tissue resected. OCT can be used to guide biopsies and can help in differentiating superficial from invasive bladder cancer, potentially reducing number of biopsies and improving the diagnostic yield.

Because of its ability to visualize mucosal structures, OCT is very promising to help guide and potentially replace biopsies, to guide resection lines during surgery and as a means to aid in diagnosis and staging of diseases, for monitoring therapy and follow-up.

Current clinical studies of laparoscopic OCT use include, but are not limited to: identification of the neurovascular bundle during radical prostatectomy (Figure 3), evaluation of renal tumors during partial nephrectomy, and intraoperative identification of nerve during nerve-sparing retroperitoneal lymph node dissection for testicular cancer. Other possible uses include the evaluation of margins during partial cystectomy, cystoureterectomy and cystectomy. The 2.7 mm probe is easily inserted through a laparoscopic port and guided to areas of interest using standard laparoscopic instruments (Figure 4).

The Niris Imaging System is intended to be used by the physician or medical personnel, at the point-of-care, and does not require an additional interpretation by a radiologist. Image interpretation training modules have been developed and presented to physicians worldwide by Imalux. Future courses are being scheduled. Please contact Imalux Corporation www.imalux.com at 866-628-6474 for more information.

Figure 2
OCT imaging during cystoscopy. 2a) OCT probe applied to bladder surface during cystoscopy. 2b) OCT image of benign bladder showing three distinct layers: dark urothelium, bright lamina propria and dark muscularis propria. There is a sharp contrast border between the urothelium and the lamina propria. 2c) OCT image of carcinoma in situ. The border between the urothelium and lamina propria is diffuse and blurred and there is no contrast between the two layers. Images courtesy of Dr. Lo (Hong Kong Sanatorium and Hospital), Dr. Manyak (GWU, Washington DC), Dr. Bodner (UHHS, Cleveland).

Figure 3 OCT image of neurovascular bundle during radical prostatectomy. The image shows a bright oval structure in the left upper corner, consistent with nerve (N). Fat (F) and connective tissue surround the nerve. Image courtesy of Dr. Kaouk (CCF, Cleveland).

Figure 4 OCT used during robotic assisted surgery. The OCT image reveals an underlying blood vessel (V). Image courtesy of Intuitive Surgical, Sunnyvale, CA.

SOURCE: Imalux Corporation