FLUORESCENCE GUIDED OPTICAL COHERENCE TOMOGRAPHY FOR THE DIAGNOSIS OF EARLY BLADDER CANCER IN A RAT MODEL

Initial Study for the Determination of the Sequence of Intersecting Lines between Gel Pens and Seals by Optical Coherence Tomography

Determining the sequence of intersecting lines is a significant issue in the forensic document examination that can reveal the fraud or distinguish between different allegations. Optical coherence tomography (OCT) is a high-resolution cross-sectional imaging technique that has been introduced into forensic science field recently. The potential of OCT as a novel method to determine the sequence of intersecting lines was examined for the first time. In this study, a spectral-domain OCT system with a center wavelength of 900 nm was employed to perform nondestructive examination on determining the sequence of 18 heterogeneous intersecting line samples produced using three types of gel pens and three brands of stamp pad ink seals. Two-dimensional (2D) cross-sectional, and three-dimensional (3D) volumetric images of the intersecting lines were obtained by the OCT system. Several features were noted and analyzed to successfully determine the sequence of all the 18 samples. Blind tests were also conducted to demonstrate the effectiveness of OCT technique. The results illustrate that OCT technology can provide an effective and accurate method for sequencing intersecting lines of gel pen ink and seal ink, which may complement the conventional methods used in the examination of questioned documents.

Optical Microscopy and Coherence Tomography of Cancer in Living Subjects

Intravital microscopy (IVM) and optical coherency tomography (OCT) are two powerful optical imaging tools that allow visualization of dynamic biological activities in living subjects with subcellular resolutions. Recent advances in labeling and label-free techniques empower IVM and OCT for a wide range of preclinical and clinical cancer imaging, providing profound insights into the complex physiological, cellular, and molecular behaviors of tumors. Preclinical IVM and OCT have elucidated many otherwise inscrutable aspects of cancer biology, while clinical applications of IVM and OCT are revolutionizing cancer diagnosis and therapies. We review important progress in the fields of IVM and OCT for cancer imaging in living subjects, highlighting key technological developments and their emerging applications in fundamental cancer biology research and clinical oncology investigation.

Gabor domain optical coherence microscopy combined with laser scanning confocal fluorescence microscopy

We report on the development of fluorescence Gabor domain optical coherence microscopy (Fluo GD-OCM), a combination of GD-OCM with laser scanning confocal fluorescence microscopy (LSCFM) for synchronous micro-structural and fluorescence imaging. The dynamic focusing capability of GD-OCM provided the adaptive illumination environment for both modalities without any mechanical movement. Using Fluo GD-OCM, we imaged ex vivo DsRed-expressing cells in the brain of a transgenic mouse, as well as Cy3-labeled ganglion cells and Cy3-labeled astrocytes from a mouse retina. The self-registration of images taken by the two different imaging modalities showed the potential for a correlative study of subjects and double identification of the target.

Revealing brain pathologies with multimodal visible light optical coherence microscopy and fluorescence imaging

We present a multimodal visible light optical coherence microscopy (OCM) and fluorescence imaging (FI) setup. Specification and phantom measurements were performed to characterize the system. Two applications in neuroimaging were investigated. First, curcumin-stained brain slices of a mouse model of Alzheimer's disease were examined. Amyloid-beta plaques were identified based on the fluorescence of curcumin, and coregistered morphological images of the brain tissue were provided by the OCM channel. Second, human brain tumor biopsies retrieved intraoperatively were imaged prior to conventional neuropathologic work-up. OCM revealed the three-dimensional structure of the brain parenchyma, and FI added the tumor tissue-specific contrast. Attenuation coefficients computed from the OCM data and the florescence intensity values were analyzed and showed a statistically significant difference for 5-aminolevulinic acid (5-ALA)-positive and -negative brain tissues. OCM findings correlated well with malignant hot spots within brain tumor biopsies upon histopathology. The combination of OCM and FI seems to be a promising optical imaging modality providing complementary contrast for applications in the field of neuroimaging.

Review of optical coherence tomography in oncology

The application of optical coherence tomography (OCT) in the field of oncology has been prospering over the past decade. OCT imaging has been used to image a broad spectrum of malignancies, including those arising in the breast, brain, bladder, the gastrointestinal, respiratory, and reproductive tracts, the skin, and oral cavity, among others. OCT imaging has initially been applied for guiding biopsies, for intraoperatively evaluating tumor margins and lymph nodes, and for the early detection of small lesions that would often not be visible on gross examination, tasks that align well with the clinical emphasis on early detection and intervention. Recently, OCT imaging has been explored for imaging tumor cells and their dynamics, and for the monitoring of tumor responses to treatments. This paper reviews the evolution of OCT technologies for the clinical application of OCT in surgical and noninvasive interventional oncology procedures and concludes with a discussion of the future directions for OCT technologies, with particular emphasis on their applications in oncology.

Depth-resolved imaging of colon tumor using optical coherence tomography and fluorescence laminar optical tomography

Early detection of neoplastic changes remains a critical challenge in clinical cancer diagnosis and treatment. Many cancers arise from epithelial layers such as those of the gastrointestinal (GI) tract. Current standard endoscopic technology is difficult to detect the subsurface lesions. In this research, we investigated the feasibility of a novel multi-modal optical imaging approach including high-resolution optical coherence tomography (OCT) and high-sensitivity fluorescence laminar optical tomography (FLOT) for structural and molecular imaging. The C57BL/6J-Apc^Min/J mice were imaged using OCT and FLOT, and the correlated histopathological diagnosis was obtained. Quantitative structural (scattering coefficient) and molecular (relative enzyme activity) parameters were obtained from OCT and FLOT images for multi-parametric analysis. This multi-modal imaging method has demonstrated the feasibility for more accurate diagnosis with 88.23% (82.35%) for sensitivity (specificity) compared to either modality alone. This study suggested that combining OCT and FLOT is promising for subsurface cancer detection, diagnosis, and characterization.

Multimodal optical coherence tomography and fluorescence lifetime imaging with interleaved excitation sources for simultaneous endogenous and exogenous fluorescence

Multimodal imaging probes a variety of tissue properties in a single image acquisition by merging complimentary imaging technologies. Exploiting synergies amongst the data, algorithms can be developed that lead to better tissue characterization than could be accomplished by the constituent imaging modalities taken alone. The combination of optical coherence tomography (OCT) with fluorescence lifetime imaging microscopy (FLIM) provides access to detailed tissue morphology and local biochemistry. The optical system described here merges 1310 nm swept-source OCT with time-domain FLIM having excitation at 355 and 532 nm. The pulses from 355 and 532 nm lasers have been interleaved to enable simultaneous acquisition of endogenous and exogenous fluorescence signals, respectively. The multimodal imaging system was validated using tissue phantoms. Nonspecific tagging with Alexa Flour 532 in a Watanbe rabbit aorta and active tagging of the LOX-1 receptor in human coronary artery, demonstrate the capacity of the system for simultaneous acquisition of OCT, endogenous FLIM, and exogenous FLIM in tissues.

Multiphoton microscopy: a potential intraoperative tool for the detection of carcinoma in situ in human bladder

CONTEXT

Urothelial carcinoma in situ (CIS) is a precursor of invasive bladder cancer, which if left untreated, will likely progress to more aggressive disease. Approximately 50% of CIS lesions are missed on routine cystoscopy owing to their flat architecture. Furthermore, many benign but abnormal-appearing areas may be biopsied owing to lack of cellular resolution of cystoscopes. Multiphoton microscopy (MPM) is an optical imaging technique that generates subcellular-resolution three-dimensional images from unfixed tissue without using exogenous dyes.

OBJECTIVE

To assess the diagnostic potential of MPM in identifying and differentiating benign from malignant flat bladder lesions, especially CIS.

DESIGN

Seventy-eight specimens (benign = 46, CIS = 23, invasive = 9, as diagnosed on histopathology) were obtained from flat bladder mucosa via transurethral resection of bladder, cold cup biopsy, or cystectomy, imaged fresh with a commercial benchtop MPM, and submitted for routine histopathology. Multiphoton microscopy and hematoxylin-eosin diagnoses were compared.

RESULTS

In 77 of 78 specimens (99%), accurate MPM diagnoses (benign/malignant) were given on the basis of their architectural and cytologic features (nuclear to cytoplasmic ratio, pleomorphism, polarity/organization of urothelial layers, etc). The sensitivity and specificity were 97% and 100%, respectively, with positive (malignant) and negative (benign) predictive values of 100% and 98%, respectively. The interobserver agreement, κ, was 0.93.

CONCLUSIONS

Our study demonstrates the capability of MPM to identify and differentiate benign from malignant flat bladder lesions, especially CIS. With the advent of MPM endoscopes, we foresee their potential as a biopsy guidance tool for early detection and treatment of CIS, thus reducing the rate of biopsies with benign diagnoses and their associated complications.

N-Methyl-N-nitrosourea as a mammary carcinogenic agent

The administration of chemical carcinogens is one of the most commonly used methods to induce tumors in several organs in laboratory animals in order to study oncologic diseases of humans. The carcinogen agent N-methyl-N-nitrosourea (MNU) is the oldest member of the nitroso compounds that has the ability to alkylate DNA. MNU is classified as a complete, potent, and direct alkylating compound. Depending on the animals' species and strain, dose, route, and age at the administration, MNU may induce tumors' development in several organs. The aim of this manuscript was to review MNU as a carcinogenic agent, taking into account that this carcinogen agent has been frequently used in experimental protocols to study the carcinogenesis in several tissues, namely breast, ovary, uterus, prostate, liver, spleen, kidney, stomach, small intestine, colon, hematopoietic system, lung, skin, retina, and urinary bladder. In this paper, we also reviewed the experimental conditions to the chemical induction of tumors in different organs with this carcinogen agent, with a special emphasis in the mammary carcinogenesis.

Simultaneous optical coherence tomography and lipofuscin autofluorescence imaging of the retina with a single broadband light source at 480nm

We accomplished spectral domain optical coherence tomography and auto-fluorescence microscopy for imaging the retina with a single broadband light source centered at 480 nm. This technique is able to provide simultaneous structural imaging and lipofuscin molecular contrast of the retina. Since the two imaging modalities are provided by the same group of photons, their images are intrinsically registered. To test the capabilities of the technique we periodically imaged the retinas of the same rats for four weeks. The images successfully demonstrated lipofuscin accumulation in the retinal pigment epithelium with aging. The experimental results showed that the dual-modal imaging system can be a potentially powerful tool in the study of age-related degenerative retinal diseases.

Novel endoscopic diagnosis for bladder cancer

Advances in endoscopic imaging technology may improve sensitivity for the detection of bladder cancer and provide a more complete understanding of the urothelial landscape, and it also may lead to improved short-term and long-term cancer control. Fluorescence cystoscopy requires intravesical administration of a photosensitizing agent (5-aminolevulinic acid or hexaminolevulinate), and imaging with a blue-light endoscopy system demonstrably improves the detection of papillary and flat bladder lesions compared with conventional white-light cystoscopy. Prospective phase 3 clinical trials have demonstrated improved diagnostic ability, enhanced tumor resection, and a small but significant reduction in recurrence-free survival. Optical coherence tomography delineates subsurface microarchitecture information about bladder lesions in real time and has the ability to discriminate between noninvasive and invasive cancers. Narrow-band imaging may augment white-light cystoscopy by providing increased contrast between normal and abnormal tissue on the basis of neovascularity. Confocal laser endoscopy has been applied to the urinary tract using thinner probes adapted from use in gastrointestinal malignancies and provides exquisite images at microscopic resolution. More technology is on the horizon that may further enhance our ability to detect and accurately stage bladder tumors and distinguish benign from malignant or dysplastic lesions.

Coregistered autofluorescence-optical coherence tomography imaging of human lung sections

Autofluorescence (AF) imaging can provide valuable information about the structural and metabolic state of tissue that can be useful for elucidating physiological and pathological processes. Optical coherence tomography (OCT) provides high resolution detailed information about tissue morphology. We present coregistered AF-OCT imaging of human lung sections. Adjacent hematoxylin and eosin stained histological sections are used to identify tissue structures observed in the OCT images. Segmentation of these structures in the OCT images allowed determination of relative AF intensities of human lung components. Since the AF imaging was performed on tissue sections perpendicular to the airway axis, the results show the AF signal originating from the airway wall components free from the effects of scattering and absorption by overlying layers as is the case during endoscopic imaging. Cartilage and dense connective tissue (DCT) are found to be the dominant fluorescing components with the average cartilage AF intensity about four times greater than that of DCT. The epithelium, lamina propria, and loose connective tissue near basement membrane generate an order of magnitude smaller AF signal than the cartilage fluorescence.

The impact of real-time 3d imaging by ultra-high speed optical coherence tomography in urothelial carcinoma

BACKGROUND

Optical coherence tomography (OCT) has become a promising diagnostic tool in many medical fields. In particular, noninvasive real-time optical biopsy of internal organs is one of the most attractive applications of OCT, enabling in situ diagnosis of carcinoma at an early stage. We used an ultra-high speed OCT system for real-time three-dimensional (3D) imaging of three excised specimens of advanced urothelial carcinoma (UC) and investigated the association of the images with results from histopathological examination.

CASE PRESENTATIONS

Case 1 was a 69-year-old man underwent radical cystectomy for muscle-invasive UC (pT2). Case 2 was a 53-year-old man underwent laparoscopic nephroureterectomy and partial cystectomy for left ureter carcinoma (pT2) and case 3 was a 77-year-old woman underwent radical cystectomy for advanced bladder carcinoma (pT3b). Real-time 3D OCT images of normal bladder wall and ureter showed three layers, including the urothelium, lamina propria, and muscularis layer. In contrast, normal structure was not seen in the muscle-invasive UC area or the scar tissue area.

CONCLUSIONS

This study highlighted a new diagnostic method with potential application for UC diagnosis. We will investigate more cases in the future and expect improvement in the diagnosing efficiency of carcinoma in situ or organ-confined muscle-invasive cancer by cystoscopy or ureteroscopy with ultra-high speed OCT.

Simultaneous optical coherence tomography and autofluorescence microscopy with a single light source

We have accomplished simultaneous spectral domain optical coherence tomography (SD-OCT) and autofluorescence (AF) microscopy with a broadband light source centered at 415 nm. The light source was provided by frequency-doubling of an ultra-fast broadband Ti:Sapphire laser. With a bandwidth of 8 nm, the visible SD-OCT achieved a depth resolution of ~12  μm. Since the two imaging modalities are provided by the same group of photons, their images are intrinsically registered. The dual-modal system is capable of providing OCT imaging and molecular contrasts simultaneously. The imaging system was tested on imaging biological samples ex vivo and in vivo.

Emerging optical techniques in advanced cystoscopy for bladder cancer diagnosis: A review of the current literature

BACKGROUND AND OBJECTIVE

The current standard for the diagnosis and followup of bladder cancer remains white light cystoscopy, despite its well-known limitations. The aim of this paper is to review the current literature on three optical diagnostics that have been developed to improve the performance of white light cystoscopy: photodynamic diagnosis, narrow-band imaging and optical coherence tomography.

MATERIALS AND METHODS

A PubMed search was performed for all articles on bladder cancer and photodynamic diagnosis, narrow-band imaging, and optical coherence tomography. Relevant papers on the working mechanism or clinical performance of the techniques were selected.

RESULTS

Photodynamic diagnosis and narrow-band imaging both aim to improve the visualization of bladder cancer. Both techniques have demonstrated an improved detection rate of bladder cancer. For photodynamic diagnosis, decreased residual tumor rates and increased recurrence free survival after photodynamic diagnosis-assisted transurethral resection have been shown. Both techniques have a relatively high false positive rate. Optical coherence tomography is a technique aiming at real-time noninvasive pathological diagnosis. Studies have shown that optical coherence tomography can accurately discriminate bladder cancer from normal bladder mucosa, and even suggest that a reliable estimation of the stage of a bladder tumor can be made.

CONCLUSIONS

Photodynamic diagnosis is the technique with most evidence of clinical effectiveness to date, but low specificity is limiting a widespread use. For the novelties, narrow-band imaging, and optical coherence tomography, more evidence is needed before these techniques can be implemented in daily urological practice.

Cross-polarization optical coherence tomography for early bladder-cancer detection: statistical study

The capabilities of cross-polarization optical coherence tomography (CP OCT) for early bladder-cancer detection are assessed in statistical study and compared with the traditional OCT. Unlike the traditional OCT that demonstrates images only in copolarization, CP OCT acquires images in cross-polarization and copolarization simultaneously. 116 patients with localized flat suspicious lesions in the bladder were enrolled, 360 CP OCT images were obtained and analyzed. CP OCT demonstrated sensitivity 93.7% (vs. 81.2%, <0.0001), specificity 84% (vs. 70.0%, <0.001) and accuracy 85.3% (vs. 71.5%, <0.001) in detecting flat malignant bladder lesions, which is significantly better than with the traditional OCT. Higher diagnostic efficacy of CP OCT in detecting early bladder cancer is associated with the ability to detect changes in epithelium and connective tissues.

In vivo simultaneous morphological and biochemical optical imaging of oral epithelial cancer

Early detection of cancer is key to reducing morbidity and mortality. Morphological and chemical biomarkers presage the transition from normal to cancerous tissue. We have developed a noninvasive imaging system incorporating optical coherence tomography (OCT) and fluorescence lifetime imaging microscopy (FLIM) into a single optical system for the first time, in order to acquire both sets of biomarkers. OCT can provide morphological images of tissue with high resolution, while FLIM can provide biochemical tissue maps. Coregistered OCT volumes and FLIM images have been acquired simultaneously in an in vivo hamster cheek pouch model of oral cancer. The OCT images indicate morphological biomarkers for cancer including thickening of the epithelial layer and loss of the layered structure. The FLIM images indicate chemical biomarkers including increased nicotinamide adenine dinucleotide and reduced collagen emission. While both sets of biomarkers can differentiate normal and cancerous tissue, we believe their combination will enable the discrimination of benign lesions possessing some of the indicated biomarkers, e.g., scarring or inflammation.

A dual-modality optical coherence tomography and fluorescence lifetime imaging microscopy system for simultaneous morphological and biochemical tissue characterization

Most pathological conditions elicit changes in the tissue optical response that may be interrogated by one or more optical imaging modalities. Any single modality typically only furnishes an incomplete picture of the tissue optical response, hence an approach that integrates complementary optical imaging modalities is needed for a more comprehensive non-destructive and minimally-invasive tissue characterization. We have developed a dual-modality system, incorporating optical coherence tomography (OCT) and fluorescence lifetime imaging microscopy (FLIM), that is capable of simultaneously characterizing the 3-D tissue morphology and its biochemical composition. The Fourier domain OCT subsystem, at an 830 nm center wavelength, provided high-resolution morphological volumetric tissue images with an axial and lateral resolution of 7.3 and 13.4 µm, respectively. The multispectral FLIM subsystem, based on a direct pulse-recording approach (upon 355 nm laser excitation), provided two-dimensional superficial maps of the tissue autofluorescence intensity and lifetime at three customizable emission bands with 100 µm lateral resolution. Both subsystems share the same excitation/illumination optical path and are simultaneously raster scanned on the sample to generate coregistered OCT volumes and FLIM images. The developed OCT/FLIM system was capable of a maximum A-line rate of 59 KHz for OCT and a pixel rate of up to 30 KHz for FLIM. The dual-modality system was validated with standard fluorophore solutions and subsequently applied to the characterization of two biological tissue types: postmortem human coronary atherosclerotic plaques, and in vivo normal and cancerous hamster cheek pouch epithelial tissue.

Optical coherence tomography for bladder cancer -- ready as a surrogate for optical biopsy? Results of a prospective mono-centre study

INTRODUCTION

New modalities like Optical Coherence Tomography (OCT) allow non-invasive examination of the internal structure of biological tissue in vivo. The potential benefits and limitations of this new technology for the detection and evaluation of bladder cancer were examined in this study.

MATERIALS AND METHODS

Between January 2007 and January 2008, 52 patients who underwent transurethral bladder biopsy or TUR-BT for surveillance or due to initial suspicion of urothelial carcinoma of the bladder were enrolled in this study. In total, 166 lesions were suspicious for malignancy according to standard white light cystoscopy. All suspicious lesions were scanned and interpreted during perioperative cystoscopy using OCT. Cold cup biopsies and/or TUR-B was performed for all these lesions. For this study we used an OCT-device (Niris, Imalux, Cleveland, US), that utilizes near-infrared light guided through a flexible fibre-based applicator, which is placed into the bladder via the working channel of the cystoscope. The technology provides high spatial resolution on the order of about 10-20 microm, and a visualization of tissue to a depth of about 2 mm across a lateral span of about 2 mm in width. The device used received market clearance from the FDA and CE approval in Germany. The diagnostic and surgical procedure was videotaped and analyzed afterwards for definitive matching of scanned and biopsied lesion. The primary aim of this study was to determine the level of correlation between OCT interpretation and final histological result.

RESULTS

Of 166 scanned OCT images, 102 lesions (61.4%) matched to the same site where the biopsy/TUR-BT was taken according to videoanalysis. Only these video-verified lesions were used for further analysis. Of all analyzed lesions 88 were benign (inflammation, edema, hyperplasia etc.) and 14 were malignant (CIS, Ta, T1, T2) as shown by final histo?pathology. - All 14 malignant lesions were detected correctly by OCT. Furthermore all invasive tumors were staged correctly by OCT regarding tumor growth beyond the lamina propria. There were no false negative lesions detected by OCT. Sensitivity of OCT for detecting the presence of a malignant lesion was 100% and sensitivity for detection of tumor growth beyond the lamina propria was 100% as well. Specificity of OCT for presence of malignancy was 65%, due to the fact that a number of lesions were interpreted as false positive by OCT.

CONCLUSION

As a minimally invasive technique, OCT proved to have extremely high sensitivity for detection of malignant lesions as well as estimation of whether a tumor has invaded beyond the lamina propria. However, specificity of OCT within the bladder was impaired (65%), possibly due to a learning curve and/or the relatively low spatial resolution and visualization depth of the OCT technology. Further studies and technical development are needed to establish an adequate surrogate for optical biopsy.

Co-registered optical coherence tomography and fluorescence molecular imaging for simultaneous morphological and molecular imaging

Optical coherence tomography (OCT) provides high-resolution, cross-sectional imaging of tissue microstructure in situ and in real time, while fluorescence molecular imaging (FMI) enables the visualization of basic molecular processes. There is a great deal of interest in combining these two modalities so that the tissue's structural and molecular information can be obtained simultaneously. This could greatly benefit biomedical applications such as detecting early diseases and monitoring therapeutic interventions. In this research, an optical system that combines OCT and FMI was developed. The system demonstrated that it could co-register en face OCT and FMI images with a 2.4 x 2.4 mm(2) field-of-view. The transverse resolutions of OCT and FMI of the system are both approximately 10 microm. Capillary tubes filled with fluorescent dye Cy 5.5 in different concentrations under a scattering medium are used as the phantom. En face OCT images of the phantoms were obtained and successfully co-registered with FMI images that were acquired simultaneously. A linear relationship between FMI intensity and dye concentration was observed. The relationship between FMI intensity and target fluorescence tube depth measured by OCT images was also observed and compared with theoretical modeling. This relationship could help in correcting reconstructed dye concentration. Imaging of colon polyps of the APC(min) mouse model is presented as an example of biological applications of this co-registered OCT/FMI system.

Time- and Spectral-resolved two-photon imaging of healthy bladder mucosa and carcinoma in situ

Combined non-linear imaging techniques were used to deeply image human ex-vivo fresh biopsies of bladder as well as to discriminate between healthy bladder mucosa and carcinoma in situ. Morphological examination by two-photon excited fluorescence and second-harmonic generation has shown a good agreement with corresponding common routine histology performed on the same samples. Tumor cells appeared slightly different in shape and with a smaller cellular-to-nuclear dimension ratio with respect to corresponding normal cells. Further differences between the two tissue types were found in both spectral emission and fluorescence lifetime distribution by performing temporal- and spectral- resolved analysis of fluorescence. This method may represent a promising tool to be used in a multi-photon endoscope, in a confocal endoscope or in a spectroscopic probe for in-vivo optical diagnosis of bladder cancer.

Multimodal optical imaging for simultaneous in-vivo morphological and biochemical characterization of oral epithelial cancer

Early detection of cancer is key to reducing morbidity and mortality. Morphological and chemical biomarkers presage the transition from normal to cancerous tissue. We have developed a noninvasive imaging system incorporating optical coherence tomography and fluorescence lifetime imaging to acquire both sets of biomarkers. Here we report early favorable results from an animal study designed to measure the capacity of this approach for early diagnosis of oral cancer.

Diagnosis of bladder cancer with microelectromechanical systems-based cystoscopic optical coherence tomography

OBJECTIVES

To examine the utility and potential limitations of microelectromechanical systems-based spectral-domain cystoscopic optical coherence tomography (COCT) so as to improve the diagnosis of early bladder cancer.

METHODS

An optical coherence tomography catheter was integrated into the single instrument channel of a 22F cystoscope to permit white-light-guided COCT over a large field of view (4.6 mm wide and 2.1 mm deep per scan at 8 frames/s) and 10-microm resolution. Intraoperative COCT diagnosis was performed in 56 patients, with a total of 110 lesions examined and compared with biopsied histology.

RESULTS

The overall sensitivity of COCT (94%) was significantly higher than cystoscopy (75%, P = .02) and voided cytology (59%, P = .005); the major enhancement over cystoscopy was for low-grade pTa-1 cancer and carcinoma in situ (P < .018). The overall specificity of COCT (81%) was comparable to voided cytology (88.9%, P = .49), but significantly higher than cystoscopy (62.5%, P = .02).

CONCLUSIONS

The microelectromechanical systems-based COCT, owing to its high resolution and detection sensitivity and large field of view, offers great potential for "optical biopsy" to enhance the diagnosis of nonpapillary bladder tumors and their recurrences and to guide bladder tumor resection.

A new generation of optical diagnostics for bladder cancer: technology, diagnostic accuracy, and future applications

CONTEXT

New developments in optical diagnostics have a potential for less invasive and improved detection of bladder cancer.

OBJECTIVE

To provide an overview of the technology and diagnostic yield of recently developed optical diagnostics for bladder cancer and to outline their potential future applications.

EVIDENCE ACQUISITION

A PubMed literature search was performed, and papers on Raman spectroscopy (RS), optical coherence tomography (OCT), photodynamic diagnosis (PDD) and narrow-band imaging (NBI) regarding bladder cancer were reviewed. Technology, clinical evidence, and future applications of the techniques are discussed.

EVIDENCE SYNTHESIS

With RS, the molecular components of tissue can be measured objectively in qualitative and quantitative ways. The first studies demonstrating human in vivo applicability are still awaited. OCT produces high-resolution, cross-sectional images of tissue, comparable with histopathology, and provides information about depth of tumour growth. The first in vivo studies of OCT demonstrated promising diagnostic accuracy. RS and OCT are not suitable for scanning the entire bladder. PDD is a technique using fluorescence to indicate pathologic tissue. Several studies have shown that PDD increases the detection rate of bladder tumours and improves resection, resulting in fewer early recurrences. The relatively low specificity of PDD remains a problem. NBI enhances contrast of mucosal surface and microvascular structures. The NBI technique has clear advantages over PDD, and the two studies published to date have shown promising preliminary results. PDD and NBI do not contribute to histopathologic diagnosis.

CONCLUSIONS

RS and OCT aim at providing a real-time, minimally invasive, objective prediction of histopathologic diagnosis, while PDD and NBI aim at improving visualisation of bladder tumours. For RS, OCT, and NBI, more research has to be conducted before these techniques can be implemented in the management of bladder cancer. All techniques might be of value in specific clinical scenarios.

Optical coherence tomography (OCT): ready for the diagnosis of a nephrogenic adenoma of the urinary bladder?

The feasibility of Optical Coherence Tomography (OCT) as a non-invasive technique was shown in different fields. We investigated OCT's potential to detect nephrogenic adenoma (NA) within the human bladder. Clinically non-invasive methods like ultrasonography or CT have significant limitations. We applied our experience from OCT-analyses to one case of NA. OCT in vivo examination was performed using an optical fiber which was positioned cystoscopically. Characteristic structures of NA were compared in the OCT-images and the hematoxylin and eosin histological samples. Indeed, the structure and exact position of NA could be defined in relation to surrounding layers. However, a definite classification as NA by OCT only could not be reached in this single case. The examination of more NA cases would be necessary to base well-founded conclusions on. Further development of this technology could lead to an optical substitute for biopsies: especially apt for the field of endourology.

Assessment of dermal wound repair after collagen implantation with optical coherence tomography

We present an animal study to examine the utility and potential limitations of optical coherence tomography (OCT) for noninvasive evaluation of biomaterial scaffold-assisted wound healing. The transverse and axial resolutions of the OCT system at the wavelength of 1.3 microm were 12 and 10 microm, respectively. A murine full-thickness transcutaneous wound model was employed, in which a phi 10 mm full-thickness wound was created on the back of each male Balb/cJ mouse and a porous collagen scaffold was implanted in the wound bed followed by coverage with a Tegaderm film. Sequential cross-sectional OCT scans were performed at different time points postsurgical intervention to track morphological changes during wound recovery, and the captured OCT images were validated by their corresponding histological specimens. The results indicated that with removal of the high-scattering skin, OCT was capable of imaging to a depth of over 1.5 mm into the wound bed and differentiating various features evolved during wound healing at a high resolution approaching histopathology. OCT was able to not only delineate the epidermis and dermis of normal mouse skin, but also differentiate collagen implant from the underlying subcutaneous tissue; besides, it could track the wound size changes in both lateral and vertical directions. More importantly, OCT was able to detect inflammation, early re-epithelialization, and resorption of the collagen scaffold. These findings suggested the potential of OCT for noninvasive and high-resolution monitoring of assisted wound healing in vivo, longitudinally, and instantaneously.

Optical coherence tomography: a review of clinical development from bench to bedside

Since its introduction, optical coherence tomography (OCT) technology has advanced from the laboratory bench to the clinic and back again. Arising from the fields of low coherence interferometry and optical time- and frequency-domain reflectometry, OCT was initially demonstrated for retinal imaging and followed a unique path to commercialization for clinical use. Concurrently, significant technological advances were brought about from within the research community, including improved laser sources, beam delivery instruments, and detection schemes. While many of these technologies improved retinal imaging, they also allowed for the application of OCT to many new clinical areas. As a result, OCT has been clinically demonstrated in a diverse set of medical and surgical specialties, including gastroenterology, dermatology, cardiology, and oncology, among others. The lessons learned in the clinic are currently spurring a new set of advances in the laboratory that will again expand the clinical use of OCT by adding molecular sensitivity, improving image quality, and increasing acquisition speeds. This continuous cycle of laboratory development and clinical application has allowed the OCT technology to grow at a rapid rate and represents a unique model for the translation of biomedical optics to the patient bedside. This work presents a brief history of OCT development, reviews current clinical applications, discusses some clinical translation challenges, and reviews laboratory developments poised for future clinical application.

In vivo bladder imaging with microelectromechanical-systems-based endoscopic spectral domain optical coherence tomography

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 mum12 mum 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).

Imaging the cavernous nerves in the rat prostate using optical coherence tomography

INTRODUCTION

Improvements in identification, imaging, and visualization of the cavernous nerves (CNs) during radical prostatectomy, which are responsible for erectile function, may improve nerve preservation and post-operative potency. Optical coherence tomography (OCT) is capable of real-time, high-resolution, cross-sectional, in vivo tissue imaging. The rat prostate serves as an excellent model for studying the use of OCT for imaging the CNs, as the rat CN is a large, visible, and distinct bundle allowing for easy identification with OCT in addition to histologic confirmation.

MATERIALS AND METHODS

Imaging was performed with the Niris OCT system and a handheld 8 Fr probe, capable of acquiring real-time images with 11-microm axial and 25-microm lateral resolution in tissue. Open surgical exposure of the prostate was performed on a total of six male rats, and OCT images of the prostate, CN, pelvic plexus ganglion, seminal vesicle, blood vessels, and periprostatic fat were acquired. CN electrical stimulation with simultaneous intracorporeal pressure measurements was performed to confirm proper identification of the CNs. The prostate and CNs were also processed for histologic analysis and further confirmation.

RESULTS

Cross-sectional and longitudinal OCT images of the CNs were acquired and compared with histologic sections. The CN and ganglion could be differentiated from the surrounding prostate gland, seminal vesicle, blood vessels, bladder, and fatty tissue.

CONCLUSIONS

We report preliminary results of OCT images of the rat CNs with histologic correlation and erectile stimulation measurements, thus providing interpretation of prostate structures as they appear in OCT images.