A comparative study between 1.3-µm optical coherence tomography (OCT) and 40-MHz high-frequency ultrasound (HFUS) is presented to enhance imaging of bladder cancers ex vivo. A standard rat bladder cancer model in which transitional cell carcinoma (TCC) was induced by intravesical instillation of AY-27 cells was followed independently with both OCT and HFUS, and the image identifications were compared to histological confirmations. Results indicate that both OCT and HFUS were able to delineate the morphology of rat bladder [e.g., the urothelium (low backscattering/echo) and the underlying lamina propria and muscularis (high backscattering/echo]. OCT differentiated inflammatory lesions (e.g., edema, infiltrates and vasodilatation in lamina propria, hyperplasia) and TCC based on characterization of urothelial thickening and enhanced backscattering or heterogeneity (e.g., papillary features), which HFUS failed due to insufficient image resolution and contrast. On the other hand, HFUS was able to stage large T2 tumors that OCT failed due to limited imaging depth. The results suggest that multimodality cystoscopy combining OCT and HFUS may have the potential to enhance the diagnosis and staging of bladder cancers and to guide tumor resection, in which both high resolution (~10 µm) and enhanced penetration (>3mm) are desirable.
We report the recent technical improvements in our microelectromechanical systems (MEMS)-based spectral-domain endoscopic OCT (SDEOCT) and applications for in vivo bladder imaging diagnosis. With the technical advances in MEMS mirror fabrication and endoscopic light coupling methods, the new SDEOCT system is able to visualize morphological details of the urinary bladder with high image fidelity close to bench-top OCT (e.g., 10 µm/12 µm axial/lateral resolutions, >108 dB dynamic range) at a fourfold to eightfold improved frame rate. An in vivo animal study based on a porcine acute inflammation model following protamine sulfate instillation is performed to further evaluate the utility of SDEOCT system to delineate bladder morphology and inflammatory lesions as well as to detect subsurface blood flow. In addition, a preliminary clinical study is performed to identify the morphological features pertinent to bladder cancer diagnosis, including loss of boundary or image contrast between urothelium and the underlying layers, heterogeneous patterns in the cancerous urothelium, and margin between normal and bladder cancers. The results of a human study (91% sensitivity, 80% specificity) suggest that SDEOCT enables a high-resolution cross-sectional image of human bladder structures to detect transitional cell carcinomas (TCC); however, due to reduced imaging depth of SDEOCT in cancerous lesions, staging of bladder cancers may be limited to T1 to T2a (prior to muscle invasion).
A fluorescence-image-guided OCT (FIG-OCT) system is described, and its ability to enhance the sensitivity and specificity is examined in an animal bladder cancer model. Total 97 specimens were examined by fluorescence imaging, OCT and histological microscopy. The sensitivity and specificity of FIG-OCT is 100% and 93% respectively, compared to 79% and 53% for fluorescence imaging, while the OCT examination time has been dramatically decreased by 3~4 times. In combination of endoscopic OCT, FIG-OCT is a promising technique for effective early bladder cancer diagnosis.
This paper summarizes the development of new 2D MEMS mirrors and the pertinent modification to improve OCT endoscopic catheter packaging suitable for in vivo imaging diagnosis of bladder cancers. Comparative study of the newly developed endocopic OCT versus the bench-top OCT is presented. Results of in vivo OCT cystoscopy based on a porcine acute inflammation model are presented to compare time-domain OCT and spectral-domain OCT for in vivo imaging. In addition, results of spectral-domain Doppler OCT are presented to image blood flow in the lamina propria of the bladder. The results of our in vivo animal study using the presented OCT endoscope are discussed for potential problems in the future clinical applications.
This paper summarizes the engineering development of our lab for endoscopic optical coherence tomography toward the ultimate goal to image bladder micro architecture and to diagnose bladder cancers. To test the utility and potential limitations of OCT setups for bladder tumor diagnosis, we used a rat bladder cancer model to track the morphological changes following tumor growth. Image results are presented, suggesting that OCT is able to differentiate cancerous lesions from inflammatory lesions based on OCT characterizations of epithelial thickness and backscattering changes of bladder tissue.
In this paper, a fiber OCT system illumined by a superluminescent diode in the 940 nm wavelength region is reported. To test the 940nm OCT system, ex-vivo rabbit bladder, porcine bladder and rat bladder with tumor were imaged and compared with 1320nm OCT. The results demonstrate that the 940nm OCT system provides higher axial resolution up to 5 μm and less speckle noise, but the experimental results showed that the image depth for bladder samples in the 940 nm OCT system is slightly lower than the 1300nm OCT due to water absorption. During experiments, it was found that the fiber caused more dispersion at the wavelength of 940 nm than 1320 nm.
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