In vivo optical coherence tomography in endoscopic diagnostics of bladder disease

Purpose: OCT is a new imaging method which produces a 3 mm wide × 2. 5 mm deep 2D picture with a resolution of 15 μm. Materials and Methods: We utilised the Tomograph Sirius 713, developed at the Medical Laser Centre in cooperation with 4-Optics AG, Lübeck, Germany. This apparatus uses a special Super-Luminescence-Diode (SLD) that produces light within the near infrared wavelength, with a central wavelength of 1300 nm. The coherence length is reduced to 15 μm. The light is introduced into a fiberglass optic which is several meters long and is easy to handle. To measure the depth of invasion and position of urothelial bladder tumours, the fibreglass optic is attached to a regular endoscope (Wolf, Knittlingen, Germany) via an OCT adapter. That way, in parallel to the regular endoscopic view of the bladder mucosa with or without pathologic findings, an OCT picture of the superficial as well as the deeper muscle layers is visible online. OCT was used to obtain 275 images from the bladder of 30 patients. Results: OCT of normal bladder mucosa produces an image with a cross section of up to 2.5 mm. It is possible to distinguish between transitional epithelium, lamina propria, smooth muscles and capillaries. In cystitis, the thickness of the mucosa is constant, but the distinction between the different layers is blurred. In squamous metaplasia there is thickening of the epithelial layer, with preservation of lamination of the lower layers. In transitional cell carcinoma there is a complete loss of the regular layered structure. Thus, the border between tumor and normal bladder tissue can be easily distinguished. Conclusions: This method can provide valuable information on tumor invasion and extension in real time and therefore influence therapeutic strategies.