NEW IMAGING TECHNIQUES (A ATALA AND A RASTINEHAD, SECTION EDITORS)

Emerging Endoscopic Imaging Technologies for BladderCancer Detection

Aristeo Lopez & Joseph C. Liao

Published online: 23 March 2014# Springer Science+Business Media New York 2014

Abstract Modern urologic endoscopy is the result of contin-uous innovations since the early nineteenth century. White-light cystoscopy is the primary strategy for identification,resection, and local staging of bladder cancer. While highlyeffective, white light cystoscopy has several well-recognizedshortcomings. Recent advances in optical imaging technolo-gies and device miniaturization hold the potential to improvebladder cancer diagnosis and resection. Photodynamic diag-nosis and narrow band imaging are the first to enter the clinicalarena. Confocal laser endomicroscopy, optical coherence to-mography, Raman spectroscopy, UV autofluorescence, andothers have shown promising clinical and pre-clinical feasi-bility. We review their mechanisms of action, highlight theirrespective advantages, and propose future directions.

Keywords Optical imaging . Fluorescence imaging . In vivomicroscopy .Multimodal imaging . Cystoscopy . Bladdercancer

Introduction

Landmark innovations over the last two centuries have shapedmodern urologic endoscopy, and particularly, endoscopicmanagement of bladder tumors [1•]. Bozzini first conceptual-ized endoscopy with his lichleiter (‘light conductor’) to illu-minate various accessible body cavities including the bladder

[2]. Subsequent innovations include the first endoscopic sur-gery (i.e., extraction of a urethral papilloma) by Desormeauxin 1853, invention of the cystoscope by Nitze in 1894, and thedevelopment and refinement of the resectoscope by Stern andMcCarthy in the early 1930s [3]. The introduction of flexiblefiberoptic cystoscopes in the 1980s, and more recently, thedigital videoscopes further decreased the morbidity associatedwith diagnostic cystoscopy.

Today, white-light cystoscopy (WLC) is the cornerstone foroffice-based hematuria workup, bladder cancer detection andsurveillance, as well as the detection of numerous other benignlower urinary tract disorders. Transurethral resection (TUR)under WLC is the standard for excisional biopsy and localstaging of bladder cancer. While widely used,WLC has severalwell-recognized shortcomings. First, nonpapillary bladder can-cer such as carcinoma in situ (CIS) may be difficult to visualizeor differentiate from inflammation [4]. Second, smaller orsatellite tumors may be missed. Third, bladder cancer may beincompletely resected, and therefore understaged [5]. Lastly,cancer grading and staging require pathological analysis, whichhas a significant time delay. Suboptimal endoscopic manage-ment of early-stage bladder cancer increases the risk of cancerpersistence, recurrence, and progression [6].

To address the shortcomings of WLC, new optical imagingtechnologies to improve detection and characterization ofsuspected bladder tumors are being developed. Table 1 sum-marizes the characteristics and properties of the technologiesreviewed. Photodynamic diagnosis (PDD), narrow-band im-aging (NBI), confocal laser endomicroscopy (CLE), and op-tical coherence tomography (OCT) have been recentlyreviewed elsewhere [7], and their recent progress is highlight-ed below. Several promising new technologies at the initialclinical feasibility (e.g., Raman spectroscopy, UVautofluores-cence) or pre-clinical stage (e.g., scanning fiber endoscopy)will be introduced. Taken together, these technologies offer anexciting glimpse into future possibilities to improve opticaldiagnosis and endoscopic management of bladder cancer.

This article is part of the Topical Collection on New Imaging Techniques

A. Lopez : J. C. Liao (*)Department of Urology, Stanford University School of Medicine,300 Pasteur Dr., Room S-387, Stanford, CA 94305-5118, USAe-mail: jliao@stanford.edu

J. C. LiaoVeterans Affairs Palo Alto Health Care System, Palo Alto,CA 94304, USA

Curr Urol Rep (2014) 15:406DOI 10.1007/s11934-014-0406-5

Photodynamic Diagnosis (PDD)

Of the new imaging technologies, PDD has the most extensiveclinical track record [8]. PDD is based on selective accumu-lation of heme-precursors, 5-aminolevulinic acid (5-ALA) orits ester derivative hexaminolevulinate (HAL), by cancer cellswhen introduced intravesically. Under blue fluorescence,bladder cancer appears red in contrast to the surroundingbenign urothelium (Fig. 1a) [9]. PDD requires a specialized

rigid cystoscope, light source, and camera head, which can beused in conjunction with sheaths of different sizes. Multi-institutional randomized clinical studies have demonstratedthat PDD improves detection of both papillary tumors andCIS compared to white light [10, 11] and patients treated withPDD-guided transurethral resection of bladder tumor(TURBT) had longer recurrence-free intervals [11, 12]. Lim-itations of PDD include false-positive fluorescence [10] frominflammatory lesions or previous biopsy sites. The contrast

Table 1 Characteristics and properties of emerging imaging modalities

*Spatial resolution and imaging depth were calculated from a custom-built upright multiphoton microscope

OCT and UV images reproduced with permission from Elsevier. Raman image reproduced with permission from American Chemical Society. SFEimage courtesy of Eric Seibel, University of Washington. MPM image reproduced with permission from National Academy of Sciences

406, Page 2 of 8 Curr Urol Rep (2014) 15:406

agent, HAL, is currently approved for single use and not forpatients who received intravesical immunotherapy or chemo-therapy within 90 days. More studies are needed to betterdefine the optimal indications for PDD use and strategies toimprove PDD’s diagnostic specificity.

Narrow-Band Imaging (NBI)

Similar to PDD, NBI is an endoscope-based imaging modalitythat the user can switch to dynamically from white-lightduring cystoscopy. NBI improves visualization of blad-der neoplasia through enhanced visualization of mucosaland submucosal vasculature without the need for exog-enous contrast agent. White light is filtered into blue(415 nm) and green (540 nm), which are wavelengthsthat hemoglobin absorbs (Fig. 1b). NBI is approved forclinical use, either in an integrated videocystoscope orthrough a camera head that can be attached to standardwhite-light cystoscopes. Both flat and papillary tumorsare more easily visualized with NBI compared to WLCdue to the increased and aberrant vascularity associatedwith bladder cancer. Single-center studies have found adetection rate of 94.7 vs. 79.2 % for WLC [13]. Studieshave shown the feasibility of NBI-assisted TUR [14]with decreased 1-year recurrence in comparison to stan-dard TUR [15]. The results from an ongoing multi-center international study comparing NBI- and WLC-assisted TUR are currently pending [16].

Confocal Laser Endomicroscopy (CLE)

Based on the well-established principle of fluorescence con-focal microscopy, CLE is an optical biopsy technology thatenables in vivo, high-resolution, subsurface imaging [17, 18•,19]. CLE is currently approved for gastrointestinal and pul-monary endoscopic applications and has been under investi-gational use in the urinary tract since 2009. Fluorescein, anFDA-approved drug with an established clinical safetyprofile, is required as the exogenous contrast agent [20].Reusable miniaturized imaging probes ranging from0.85-mm to 2.6-mm diameter are compatible with work-ing channels of standard cystoscopes [21]. Real-timemicroscopy of normal urothelium, inflammation, CIS,low-grade and high-grade urothelial carcinoma havebeen demonstrated with images comparable to conven-tional histopathology (Fig. 1c) [18•]. A recent studydemonstrated moderate interobserver agreement in im-age interpretation between novice and experienced CLEurologists with respect to cancer diagnosis [19]. Multi-center studies examining the CLE diagnostic accuracyfor real-time cancer diagnosis and grading remained tobe completed. An advantage of CLE is that it may becoupled with fluorescently-labeled peptides or antibodiesagainst cancer-specific surface antigens, as it has beendemonstrated in the gastrointestinal tract [22•, 23] Sim-ilar endoscopic molecular imaging strategies may bedeployed in the bladder to improve cancer diagnosiswith molecular specificity.

Fig. 1 New bladder imaging technologies with corresponding white-light cystoscopy (WLC). a Bladder tumors appeared pink under bluefluorescence of photodynamic diagnosis (PDD); bNarrow-band imaging(NBI) enhances visualization of aberrant tumor vasculature; c Confocallaser endomicroscopy (CLE) enables in-vivo microscopy of a papillary

urothelial carcinoma; d Subsurface imaging of a papillary urothelialcancer using optical coherence tomography (OCT) showing loss ofnormal urothelial layers. Image reproduced with permission fromElsevier

Curr Urol Rep (2014) 15:406 Page 3 of 8, 406

Optical Coherence Tomography (OCT)

OCT is another optical biopsy technology that enables high-resolution, subsurface tissue interrogation. OCT is analogous toultrasound in that cross-sectional images are generated (Fig. 1d)using near-infrared light instead of sound waves as the source.Image resolutions of 10-20 μm and depths of penetration of2 mm can be achieved, thus enabling the possibility of real-time cancer diagnosis and staging (i.e., differentiation betweennon-muscle and muscle invasive cancer) [24–26]. Similar toCLE, there is a learning curve associated with image interpreta-tion, which is based on the loss of delineation between tissuelayers (e.g., lamina propria). Other recent studies have reportedan automated image-processing algorithm to detect bladder can-cer fromOCT images [27] and application in the upper tract [28].

Multimodal Imaging

Given the different imaging characteristics, a combination ofmacroscopic (e.g., PDD and NBI) and microscopic (e.g., CLEand OCT) imaging modalities used in concert may improvediagnostic accuracy [7]. For example, PDD and NBI could beused to identify suspicious lesions, while CLE and OCT providehigh-resolution characterization to provide grading or staginginformation. Feasibility of combining endoscope-based PDDand NBI with probe-based CLE has been reported (Fig. 2) [29,30]. A recent study showed that PDD combined with OCT hadincreased the specificity compared to PDD alone [31]. In anotherstudy, PDD in combination with standard OCT did not improvethe diagnostic accuracy significantly in detecting non-invasivebladder cancer, but the use of cross-polarization OCT and PDDdecreased overall false-positive and negative cases [32].

Raman Spectroscopy (RS)

RS is based on the principle of inelastic scattering of photonsfollowing interaction with intramolecular bonds. Near infraredlight (785–845 nm) is used to illuminate biological tissues andalter the vibrational state of molecules. The photons donateenergy to molecular bonds, and as a result, exit the tissue at adifferent wavelength from the incident light. The change inenergy level of the photons is known as a Raman shift [33].Detection of multiple Raman peaks from the target tissue isplotted to create a spectrum of peaks, achieving a molecular“fingerprint” of the tissue examined without the need for exog-enous contrast agent [34•]. In ex vivo settings, RS has beenshown to differentiate the normal bladder wall layers, identifylow- and high-grade bladder cancer, and assess invasiveness [35,36]. To evaluate the feasibility of in vivo bladder cancer diagno-sis, a prototype fiberoptic Raman probe compatible with theworking channels of endoscopes has been developed [34•, 37,

38]. In 38 patients suspected of having bladder cancer, thedifferentiation of cancerous tissue from normal urothelium wasfeasible in near real-time during cystoscopy [34•] Recent re-search led to the development of a non-contact Raman probethat detects signals even with imperfect centering of the probeand nonuniform topology of human tissue surface [39]. Recog-nized limitations of RS include time to obtain a spectrum (1–5 seconds), weak signals, and limited field of view. Surface-enhanced Raman scattering (SERS) nanoparticles have beendemonstrated to augment the relatively weak signals from Ra-man scattering. SERS substrates can be conjugated to cancer-specific antibodies to enablemultiplexed targeted imaging duringendoscopy [40].

Ultraviolet (UV) Autofluorescence

The basis of UV-induced autofluorescence is to differentiatenormal, inflammatory, and cancerous urothelium by differencesin their intrinsic molecular contents. UV light is used to exciteendogenous fluorophores (e.g., NAD and tryptophan) present inthe tissue of interest. A pilot clinical study composed of 14

Fig. 2 Multimodal imaging using narrow-band imaging and confocallaser endomicroscopy. a Endoscopic view of the confocal imaging probeadjacent to a papillary tumor at the bladder dome. Yellow tinge corre-sponds with intravesical fluorescein as contrast agent for CLE. bNarrow-band imaging highlights tissue and tumor vasculature. c Concomitantendomicroscopy image shows well-organized papillary border andmonomorphic urothelial cells consistent with a low-grade papillaryurothelial carcinoma

406, Page 4 of 8 Curr Urol Rep (2014) 15:406

patients was recently published [41•]. A UV light-emitting probe(360 and 450 nm) was inserted via the working channel of astandard cystoscope and advanced in close proximity to theregion of interest for tissue interrogation. For image processing,the signals were converted into an intensity ratio between the twowavelengths and color-coded to facilitate real-time interpretation[41•]. In the pilot study, real-time differentiation of bladder cancerfrom benign/normal urothelium based on autofluorescence spec-trum was demonstrated (Fig. 3). Further studies are needed toinvestigate signal intensity across different tumor types (includingflat lesions), reproducibility, and potential for UV-inducedtoxicity.

Multiphoton Microscopy (MPM)

In MPM, fluorescence is achieved by the nonlinear excitation ofmolecules after the simultaneous absorption of two or more

photons of lesser energy [42]. MPM takes advantage of intrinsictissue fluorophores (i.e., NADH, FAD, and collagen) instead ofexogenous contrast agents. In addition to the autofluorescencesignals, MPM is also able to visualize non-centrosymmetricstructures (e.g., collagen) via second-harmonic generation(SHG). The exciting light is produced from a femtosecondpulsed Ti-Sapphire laser tuned to 780 nm, while the detectedautofluorescence and SHG signals are in the range of 420–530 nm and 355–420 nm, respectively [43]. The interpretationof acquired images is simplified by color-coding the detectedSHG and autofluorescence signals. Recent in vitro studies usingMPM demonstrated high-resolution images from fresh TURbladder tissues comparable to histopathology and differentiationof malignant and benign features. Similar to CLE, limitations ofMPM include limited depth of penetration not suitable for cancerstaging and a lack of nuclear morphology on the images. Currentresearch is focused on miniaturizing the MPM system into acompact probe suitable for in vivo use [44–46].

Fig. 3 Tumor autofluorescence with an ultraviolet (UV) imaging probe.a Cystoscopic view of the imaging probe adjacent to normal urotheliumand tumor; b Color-coding is integrated in real-time and facilitates inter-pretation of autofluorescence measurements and differentiation of normal

(green) and malignant (red) tissue; c Histogram of the autofluorescentmeasurements showing the calculated mean diagnostic ratios of healthytissue (0.91) and the papillary tumor (0.26). Image reproduced withpermission from Elsevier

Curr Urol Rep (2014) 15:406 Page 5 of 8, 406

Scanning Fiber Endoscopy (SFE)

SFE uses an ultrathin (1.2-mm tip) flexible endoscope thatprovides wide-angle, full-color high-resolution images [47].The tip contains a single-mode optical fiber that spirally scansred, green, and blue laser light that is focused onto tissue. Thebackscattered light is collected by multiple optical fibers and animage is generated pixel by pixel [48]. The small diameterdecreases the invasiveness and expands the versatility of howSFE may be deployed either as a standalone miniaturized endo-scope or as a probe in conjunction with other imaging modalities[49]. Currently, SFE has been demonstrated in the gastrointesti-nal tract and in ex vivo bladder models [50, 51•]. A provocativeapplication of SFE involves integrating an automated bladder-scanning device and an ‘image-stitching’ algorithm to generate a2-D panoramic view of the mucosa. Figure 4 shows examples ofsuch image mosaicing in a phantom model and ex vivo pigbladder [50, 51•]. With integration of automated scanning, SFEcystoscopy may be performed in the future by skilled technolo-gists with the urologist reviewing the images in real time oroffline. The panoramic view may also provide a systematicway for tumormapping and surveying the bladder longitudinally.

Telerobotic Cystoscopy—Cystoscope of the Future?

As new imaging technologies enter into clinical use, newmethods to integrate different imaging modalities with

endoscopic surgical interventions may be needed. A teleroboticcystoscopy system has recently been developed and tested inex vivo animal models (Fig. 5) [52•]. This system containsmultiple instrument channels and offers the potential to integrateoptical imaging, catheter-based ablative technologies, and a newgeneration of micro-surgical tools with additional degrees of

Fig. 4 Scanning fiber endoscopy (SFE) of a bladder phantom andexcised pig bladder to generate surface mosaics of the urothelium. a Abladder phantom with painted on vessels was imaged using a conven-tional endoscope from which a b 3D mosaic was constructed. c A multi-modal mosaic was generated by SFE imaging of the same phantom with

green fluorescent microspheres to mimic hotspots (arrows). Using theSFE, a mosaic d, ewas constructed from roughly a thousand frames takenwithin an excised pig bladder. Image courtesy of Eric Seibel, Universityof Washington

Fig. 5 A prototype telerobotic system for the bladder. a Schematic of thedexterous bladder telerobotic system. The central rigid stem contains anoptical scope and irrigation apparatus. b The dexterous end effector hasmultiple channels including its own optics and channels for laser andother tools such as tissue optical interrogation catheters. c The dexterousinstrumentation manipulated to various areas of an ex vivo bovine blad-der. Courtesy of Nabil Simaan and Duke Herrell, Vanderbilt University

406, Page 6 of 8 Curr Urol Rep (2014) 15:406

freedom. Such ‘smart’ endoscopic instruments may expand thespectrum of multi-modal endoscopic interventions that can beperformed in the urinary tract.

Conclusions

Modern endoscopy and endoscopic surgery of the urinarytract is the culmination of ingenuity and persistence by manyinnovators in urology, surgery, and engineering over the lasttwo centuries. These innovations introduced the concept ofminimally-invasive surgery and revolutionized the manage-ment of bladder cancer. Recent advances in optical imagingand instrument miniaturization are poised to usher in an era ofimage-guided surgery that holds the potential to improvecancer localization, delineation of surgical margins, and real-time tissue interrogation. Coupled with an improved under-standing of cancer biology, we hope that improved detectionwill lead to more effective endoscopic resection of bladdercancer, reduced cancer recurrence and progression, and cost-effective utilization of available health-care resources [53].

Acknowledgements The authors thank KathleenMach for critical reviewof the manuscript. A.L. is supported by the Stanford University School ofMedicine MedScholars Research Fellowship. J.C.L. is supported in part bygrant R01 CA160986 from the National Cancer Institute.

Compliance with Ethics Guidelines

Conflict of Interest Dr. Aristeo Lopez declares no potential conflicts ofinterest relevant to this article.

Dr. Joseph C. Liao received a research grant from the NationalInstitute of Health (NIH). Dr. Liao received travel support from MaunaKea Technologies, including expenses covered or reimbursed, and pay-ment for the development of educational presentations from Storz.

Human and Animal Rights and Informed Consent This article doesnot contain any studies with human or animal subjects performed by anyof the authors.

References

Papers of particular interest, published recently, have beenhighlighted as:• Of importance

1.• Herr H. Early history of endoscopic treatment of bladder tumorsfrom Grunfeld ’ s Polypenkneipe to the Stern-McCarthyResectoscope. J Endourol. 2006;20(2):85–91. This article high-lights the most noteworthy innovations that occurred in urologicendoscopy providing an overview of the history of endoscopy andthe endoscopic management of bladder tumors.

2. Natalin RA, Landman J. Where next for the endoscope? Nat RevUrol. 2009;6(11):622–8.

3. Samplaski MK, Jones JS. Two centuries of cystoscopy: the devel-opment of imaging, instrumentation and synergistic technologies.BJU Int. 2009;103(2):154–8.

4. Witjes JA. Bladder carcinoma in situ in 2003: state of the art. EurUrol. 2004;45(2):142–6.

5. Cheng L, Neumann RM, Weaver AL, Cheville JC, Leibovich BC,Ramnani DM, et al. Grading and staging of bladder carcinoma intransurethral resection specimens. Correlation with 105 matchedcystectomy specimens. Am J Clin Pathol. 2000;113(2):275–9.

6. Babjuk M. Transurethral resection of non–muscle-invasive bladdercancer. Eur Urol Suppl. 2009;8(7):542–8.

7. Liu J-J, Droller MJ, Liao JC. New optical imaging technologies forbladder cancer: considerations and perspectives. J Urol.2012;188(2):361–8.

8. Kausch I, Sommerauer M, Montorsi F, Stenzl A, Jacqmin D,Jichlinski P, et al. Photodynamic diagnosis in non-muscle-invasive bladder cancer: a systematic review and cumulative anal-ysis of prospective studies. Eur Urol. 2010;57(4):595–606.

9. Mark JR, Gelpi-Hammerschmidt F, Trabulsi EJ, Gomella LG. Bluelight cystoscopy for detection and treatment of non-muscle invasivebladder cancer. Can J Urol. 2012;19(2):6227–31.

10. Lapini A, Minervini A, Masala A, Schips L, Pycha A, Cindolo L,et al. A comparison of hexaminolevulinate (Hexvix(®)) fluores-cence cystoscopy and white-light cystoscopy for detection of blad-der cancer: results of the HeRo observational study. Surg Endosc.2012;26(12):3634–41.

11. RinkM, BabjukM, Catto JWF, Jichlinski P, Shariat SF, Stenzl A, et al.Hexyl aminolevulinate-guided fluorescence cystoscopy in the diagnosisand follow-up of patients with non-muscle-invasive bladder cancer: acritical review of the current literature. Eur Urol. 2013;64(4):624–38.

12. Grossman HB, Stenzl A, Fradet Y, Mynderse LA, Kriegmair M,Witjes JA, et al. Long-term decrease in bladder cancer recurrencewith hexaminolevulinate enabled fluorescence cystoscopy. J Urol.2012;188(1):58–62.

13. Cauberg ECC, Kloen S, VisserM, de la Rosette JJMCH, BabjukM,Soukup V, et al. Narrow band imaging cystoscopy improves thedetection of non-muscle-invasive bladder cancer. Urology.2010;76(3):658–63.

14. Naselli A, Introini C, Bertolotto F, Spina B, Puppo P. Feasibility oftransurethral resection of bladder lesion performed entirely bymeans ofnarrow-band imaging. J Endourol Endourol Soc. 2010;24(7):1131–4.

15. Naselli A, Introini C, Timossi L, Spina B, Fontana V, Pezzi R, et al.A randomized prospective trial to assess the impact of transurethralresection in narrow band imagingmodality on non-muscle-invasivebladder cancer recurrence. Eur Urol. 2012;61(5):908–13.

16. Naito S, van Rees Vellinga S, de la Rosette J. Global randomizednarrow band imaging versus white light study in nonmuscle inva-sive bladder cancer: accession to the first milestone-enrollment of600 patients. J Endourol Endourol Soc. 2013;27(1):1–3.

17. Sonn GA, Jones S-NE, Tarin TV, Du CB, Mach KE, Jensen KC,et al. Optical biopsy of human bladder neoplasia with in vivoconfocal laser endomicroscopy. J Urol. 2009;182(4):1299–305.

18.• Wu K, Liu J-J, Adams W, Sonn GA, Mach KE, Pan Y, et al.Dynamic real-time microscopy of the urinary tract using confocallaser endomicroscopy. Urology. 2011;78(1):225–31. This articlecompiled representative confocal images from the urinary tract intoan imaging atlas. The atlas was used to develop the diagnosticimaging criteria for benign and neoplastic conditions of the urinarytract to facilitate the use and enable adaptation of CLE.

19. Chang TC, Liu J-J, Hsiao ST, Pan Y, Mach KE, Leppert JT, et al.Interobserver agreement of confocal laser endomicroscopy for blad-der cancer. J Endourol Endourol Soc. 2013;27(5):598–603.

20. Wallace MB, Meining A, Canto MI, Fockens P, Miehlke S, RoeschT, et al. The safety of intravenous fluorescein for confocal laserendomicroscopy in the gastrointestinal tract. Aliment PharmacolTher. 2010;31(5):548–52.

Curr Urol Rep (2014) 15:406 Page 7 of 8, 406

21. Adams W, Wu K, Liu J-J, Hsiao STT, Jensen KC, Liao JC.Comparison of 2.6- and 1.4-mm imaging probes for confocal laserendomicroscopy of the urinary tract. J Endourol Endourol Soc.2011;25(6):917–21.

22.• Hsiung P-L, Hsiung P-L, Hardy J, Friedland S, Soetikno R, Du CB,et al. Detection of colonic dysplasia in vivo using a targetedheptapeptide and confocal microendoscopy. Nat Med. 2008;14(4):454–8. This study identified and synthesized a peptide, VRPMPLQ,that bound more strongly to dysplastic colonocytes than to normalcells. By conjugating the peptide to fluorescein the fluorescentsignals were detected with CLE.

23. Sturm MB, Joshi BP, Lu S, Piraka C, Khondee S, Elmunzer BJ,et al. Targeted imaging of esophageal neoplasia with a fluorescentlylabeled peptide: first-in-human results. Sci Transl Med.2013;5(184):184ra61.

24. Hermes B, Spöler F, Naami A, Bornemann J, Först M, Grosse J,et al. Visualization of the basement membrane zone of the bladderby optical coherence tomography: feasibility of noninvasive evalu-ation of tumor invasion. Urology. 2008;72(3):677–81.

25. Goh AC, Tresser NJ, Shen SS, Lerner SP. Optical coherence tomogra-phy as an adjunct to white light cystoscopy for intravesical real-timeimaging and staging of bladder cancer. Urology. 2008;72(1):133–7.

26. Willmann E. Optical coherence tomography for bladder cancer-ready as a surrogate for optical biopsy? -Results of a prospectivemono-centre study. pp. 131–4; 2010.

27. Lingley-Papadopoulos CA, Loew MH, Manyak MJ, Zara JM.Computer recognition of cancer in the urinary bladder using opticalcoherence tomography and texture analysis. J Biomed Opt.2013;13(2):024003.

28. Bus MTJ, Muller BG, de Bruin DM, Faber DJ, Kamphuis GM, vanLeeuwen TG, et al. Volumetric in vivo visualization of upperurinary tract tumors using optical coherence tomography: a pilotstudy. J Urol. 2013;190(6):2236–42.

29. Bonnal J-L, Rock A, Gagnat A, Papadopoulos S, Filoche B,Mauroy B. Confocal laser endomicroscopy of bladder tumors as-sociated with photodynamic diagnosis: an ex vivo pilot study.Urology. 2012;80(5):1162.e1–5.

30. Chang TC, Liu J-J, Liao JC. Probe-based confocal laserendomicroscopy of the urinary tract: the technique. J Vis Exp.2013;(71):e4409.

31. Schmidbauer J, Remzi M, Klatte T, Waldert M, Mauermann J,Susani M, et al. Fluorescence cystoscopy with high-resolutionoptical coherence tomography imaging as an adjunct reducesfalse-positive findings in the diagnosis of urothelial carcinoma ofthe bladder. Eur Urol. 2009;56(6):914–9.

32. Gladkova N, Kiseleva E, Streltsova O, Prodanets N, Snopova L,Karabut M, et al. Combined use of fluorescence cystoscopy andcross-polarization OCT for diagnosis of bladder cancer and corre-lation with immunohistochemical markers. J Biophotonics.2013;6(9):687–98.

33. Rao AR, Hanchanale V, Javle P, Karim O, Motiwala H.Spectroscopic view of life and work of the Nobel Laureate SirC.V. Raman. J Endourol Endourol Soc. 2007;21(1):8–11.

34.• Draga ROP, Grimbergen MCM, Vijverberg PLM, van Swol CFP,Jonges TGN, Kummer JA, et al. In vivo bladder cancer diagnosis byhigh-volume Raman spectroscopy. Anal Chem. 2010;82(14):5993–9. This study showed the feasibility of in vivo RS for diagnosis ofbladder cancer using a Raman probe. Bladder cancer and normalurothelium had characteristic Raman spectra that were used todiscriminate healthy and cancerous bladder tissue.

35. de Jong BWD, Bakker Schut TC, Wolffenbuttel KP, Nijman JM,KokDJ, Puppels GJ. Identification of bladder wall layers by Ramanspectroscopy. J Urol. 2002;168(4 Pt 2):1771–8.

36. Crow P, Uff JS, Farmer JA,WrightMP, Stone N. The use of Ramanspectroscopy to identify and characterize transitional cell carcinomain vitro. BJU Int. 2004;93(9):1232–6.

37. Grimbergen MCM, van Swol CFP, Draga ROP, van Diest P,Verdaasdonk RM, Stone N, et al. Bladder cancer diagnosis duringcystoscopy using Raman spectroscopy. Proc SPIE. 2009;7161:716114–716114–6.

38. Magee ND, Villaumie JS, Marple ET, Ennis M, Elborn JS,McGarvey JJ. Ex vivo diagnosis of lung cancer using a Ramanminiprobe. J Phys Chem B. 2009;113(23):8137–41.

39. Zavaleta CL, Garai E, Liu JTC, Sensarn S, Mandella MJ, Van deSompel D, et al. A Raman-based endoscopic strategy formultiplexed molecular imaging. Proc Natl Acad Sci U S A.2013;110(25):E2288–97.

40. Vendrell M, Maiti KK, Dhaliwal K, Chang Y-T. Surface-enhancedRaman scattering in cancer detection and imaging. TrendsBiotechnol. 2013;31(4):249–57.

41.• Schäfauer C, Ettori D, Rouprêt M, Phé V, Tualle J-M, Tinet E, et al.Detection of bladder urothelial carcinoma using in vivo noncontact,ultraviolet excited autofluorescence measurements converted into sim-ple color coded images: a feasibility study. J Urol. 2013;190(1):271–7.This feasibility study demonstrated that bladdercancercould be detect-ed using ultraviolet laser-induced autofluorescence measurements(AM). Converting the AMs into color-coded images, red indicatingtumor and green indicating normal tissue, facilitated interpretation.

42. Zipfel WR, Williams RM, Webb WW. Nonlinear magic: multiphotonmicroscopy in the biosciences. Nat Biotechnol. 2003;21(11):1369–77.

43. Jain M, Robinson BD, Scherr DS, Sterling J, Lee M-M, Wysock J,et al. Multiphoton microscopy in the evaluation of human bladderbiopsies. Arch Pathol Lab Med. 2012;136(5):517–26.

44. Yadav R, Mudalair K, Srivastava A, Rubin MA. Multiphotonmicroscopy for structure identification in human prostate andperiprostatic tissue: implications in prostate cancer surgery. BJUInt. 2012;108(9):1421–9.

45. Xu C. Multiphoton imaging for deep tissue penetration and clinicalendoscopy. Proc SPIE. 2011;7891:78910H–78910H–4.

46. Rivera DR, Brown CM, Ouzounov DG, Pavlova I, Kobat D, WebbWW, et al. Compact and flexible raster scanning multiphotonendoscope capable of imaging unstained tissue. PNAS.2011;108(43):17598–603.

47. Seibel EJ, Brentnall TA, Dominitz JA. New endoscopic and cyto-logic tools for cancer surveillance in the digestive tract. GastrointestEndosc Clin N Am. 2009;19(2):299–307.

48. Seibel EJ, Brown CM, Dominitz JA, KimmeyMB. Scanning singlefiber endoscopy: a new platform technology for integrated laserimaging, diagnosis, and future therapies. Gastrointest Endosc ClinN Am. 2008;18(3):467–78. viii.

49. Yoon WJ, Park S, Reinhall PG, Seibel EJ. Development of anautomated steering mechanism for bladder urothelium surveillance.J Med Devices. 2009;3(1):011004.

50. Soper TD, Porter MP, Seibel EJ. Surface mosaics of the bladderreconstructed from endoscopic video for automated surveillance.IEEE Trans Biomed Eng. 2012;59(6):1670–80.

51.• Soper TD, Chandler JE, Porter MP, Seibel EJ. Constructing spher-ical panoramas of a bladder phantom from endoscopic video usingbundle adjustment. 2011;7964:796417–796417–12, Mar. Thisstudy shows that stitching software is able to create a complete360° panoramic image of a bladder phantom from video framesobtained with an SFE endoscope.

52.• GoldmanRE, Bajo A,MacLachlan LS, Pickens R, Herrell SD, SimaanN. Design and performance evaluation of a minimally invasivetelerobotic platform for transurethral surveillance and intervention.IEEE Trans Biomed Eng. 2013;60(4):918–25. This study demonstratesthe design and evaluation of a prototype telerobotic system that providesa dexterous manipulator with access channels for the deployment ofmultiple tools, and is compatible with current resectoscope sheaths.

53. Botteman MF, Pashos CL, Redaelli A, Laskin B, Hauser R. Thehealth economics of bladder cancer: a comprehensive review of thepublished literature. PharmacoEconomics. 2003;21(18):1315–30.

406, Page 8 of 8 Curr Urol Rep (2014) 15:406