Measurement of Optical Scattering Coefficient of the Individual Layers of the Human Urinary Bladder Using Optical Coherence Tomography

The author reports measurement of the optical attenuation of the urinary bladder using Optical Coherence Tomography. This method uses the exponential relationship that exists between the intensity of the back-scattered infrared light and the penetration depth. The method is applied to Optical Coherence Tomography images of the human urinary bladder and the scattering coefficients of the top three layers (urothelium, lamina propria, and muscle layers, resp.) are extracted. An optical attenuation ratio of 1？:？6.2？:？4.2 for the three layers is reported. 1. Introduction Bladder cancer is the fourth most common cancer among men. The current method for bladder cancer detection after the patient has reported symptoms that may be related to cancer is visual inspection of the bladder surface using endoscopic methods followed by biopsy. However, it is possible for cancerous and precancerous lesions to go undetected by urologists using conventional visual inspection. A sensitivity of 78% for bladder lesion detection using white light cystoscopy has been reported by Schmidbauer et al. [1]. Biopsies of these undetected cancer lesions are not taken simply because they are not visible to the urologist. Failure to biopsy these lesions may result in a false negative diagnosis, delaying cancer detection, and increasing mortality risk. High resolution images of the subsurface structures of the bladder will greatly enhance the urologist’s ability to diagnose pathological conditions previously undetected by conventional visual inspection. Optical Coherence Tomography (OCT) has shown significant potential in this regard. Recently, Optical Coherence Tomography (OCT), an imaging modality that measures the intensity of back-scattered infrared light and produces subsurface images with micrometer resolution, has shown significant promise in early detection of bladder cancer [2–4]. The major disadvantage of OCT is the high level of scattering of near-infrared light in biological tissues, which limits penetration depth to 1-2？mm [4]. However, bladder cancer tends to arise within 600？μm of the tissue surface. This makes endoscopic OCT imaging systems suitable for bladder cancer detection. Several studies using OCT for detection, diagnosis, and staging of bladder cancer have been conducted and shown promising results [3, 4]. It is still unclear how closely the changes in the optical properties of the tissue can be correlated with progression of the disease. de Reijke et al. examined human bladder tissue specimens ex vivo by 850？nm OCT using dynamic focusing and presented scattering