Detection and diagnosis of oral cancer by light-induced fluorescence

Clinical efficacy of 5-aminolevulinic acid-mediated photodynamic therapy versus topical antifungal agent and surgical excision for the treatment of hyperplastic candidiasis

BACKGROUND

Hyperplastic candidiasis (HC) is a chronic infection of oral mucosa caused by Candida. Owing to its potential for malignant transformation, its intervention requires attention. Conventional surgical resection might lead to irreversible damage and impact the patient's quality of life. Hence, this study aimed to evaluate the clinical efficacy of 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT) alone and in combination with topical antifungal therapy (i.e., nystatin [combination therapy]) in comparison with nystatin and surgical resection for the treatment of HC.

METHODS

Forty subjects with clinical and histopathological diagnoses of HC were included in the study. Four study groups, with 10 participants each, were formed as follows: Group-I - receiving antifungal agent [nystatin]; Group-II - receiving surgical resection; Group-III - receiving PDT; and Group-IV - receiving 5-ALA-mediated PDT and nystatin [combination therapy]. Salivary and mucosal samples were collected for the quantification of Candida albicans and the treatment responses to different interventions were recorded at week-4, week-6, and week-8 after finishing therapies.

RESULTS

At the 3^rd follow-up (i.e., at end of the 8^th week after the interventions), complete improvement in 3 (30%), 2 (20%), 1 (10%), and 5 (50%) patients in group-I, group-II, group-III, and group-IV, respectively was observed. A statistically significant difference was obtained when the intervention responses were compared at week-4 (p<0.01), week-6 (p<0.01), and week-8 (p<0.0001) follow-ups in group-I, group-II, and group-IV subjects. At the 8-week follow-up regarding the salivary and mucosal samples, the lowest colony-forming units/milliliter score of C. albicans was observed in group-IV subjects.

CONCLUSION

The application of 5-ALA-mediated PDT in combination with nystatin gel possesses the potential as a well-tolerated and safe therapeutic modality for the treatment of patients with HC.

Mesoporous Silica-Coated Upconversion Nanoparticles Assisted Photodynamic Therapy Using 5-Aminolevulinic Acid: Mechanistic and In Vivo Studies

Exclusively red-emitting upconversion nanoparticles (UCNPs) with the composition NaErF₄:0.5%Tm as a core and NaYF₄ as a shell were synthesized for performing photodynamic therapy (PDT). A possible mechanism was proposed for core-shell UCNPs formation. For loading a maximum amount of 5-aminolevulinic acid (5-ALA), mesoporous silica coating was performed on UCNPs. Studies under dark conditions confirmed the biocompatibility of 5-ALA-loaded UCNPs formulation (UCNPs-5-ALA) with MCF-7 cells. Meanwhile, studies under light-exposed conditions exhibited effective cytotoxicity against MCF-7 cells. Studies employing D₂O-based cell cultured media and addition of DABCO in cell culture established that the cell death was due to oxidation of cellular components by reactive oxygen species (ROS) triggering the apoptosis. The formation of ROS was confirmed by DCF(H)DA-based ROS analysis via fluorescence microscopy to demonstrate the ROS production, which mediates the programmed cell death. Additionally, we have validated the apoptosis in MCF-7 cells with flow cytometry analyses. This was further confirmed by an electrophoretic mobility shift assay on nuclear extract and measurement of mitochondrial membrane potential. In the case of animal model studies, the formulation UCNPs-5-ALA without irradiation (980 nm) did not possess any in vivo cytotoxicity on tumor-induced SCID mice and there was a minimum migration of UCNPs-5-ALA to the vital organs but maximum retention at the tumor site only. Meanwhile, only the mice treated with UCNPs-5-ALA and irradiated on the tumor region with 980 nm laser (500 mW) for 20 min possessed a tumor with a size reduced to about 75% as compared with the corresponding control groups. To the best of our knowledge, this type of study was conducted for the first time employing exclusively red-emitting phosphors for effective PDT.

Photosensitizer-Functionalized Nanocomposites for Light-Activated Cancer Theranostics

Photosensitizers (PSs) have received significant attention recently in cancer treatment due to its theranostic capability for imaging and phototherapy. These PSs are highly responsive to light source of a suitable wavelength for image-guided cancer therapy from generated singlet oxygen and/or thermal heat. Various organic dye PSs show tremendous attenuation of tumor cells during cancer treatment. Among them, porphyrin and chlorophyll-based ultraviolet-visible (UV-Vis) dyes are employed for photodynamic therapy (PDT) by reactive oxygen species (ROS) and free radicals generated with 400-700 nm laser lights, which have poor tissue penetration depth. To enhance the efficacy of PDT, other light sources such as red light laser and X-ray have been suggested; nonetheless, it is still a challenging task to improve the light penetration depth for deep tumor treatment. To overcome this deficiency, near infrared (NIR) (700-900 nm) PSs, indocyanine green (ICG), and its derivatives like IR780, IR806 and IR820, have been introduced for imaging and phototherapy. These NIR PSs have been used in various cancer treatment modality by combining photothermal therapy (PTT) and/or PDT with chemotherapy or immunotherapy. In this review, we will focus on the use of different PSs showing photothermal/photodynamic response to UV-Vis or NIR-Vis light. The emphasis is a comprehensive review of recent smart design of PS-loaded nanocomposites for targeted delivery of PSs in light-activated combination cancer therapy.

Porphyrinoids in photodynamic diagnosis and therapy of oral diseases

Photodynamic methods have found application not only in the treatment process as photodynamic therapy but also for the early detection of neoplastic lesions and tumors as photodynamic diagnosis. Early detection of the disease allows not only to avoid the patient’s lifetime risk but also significantly reduce the costs of anticancer therapy, which are increasing every year. There is a constant search for new and more effective photosensitizers which will provide safety in therapy while maintaining efficiency. This paper summarizes recent reports focused on the photodynamic diagnosis of oral cancers. Moreover, it shows methods of the photodynamic treatment of oral verrucous hyperplasia, erythroleukoplakia, and oral leukoplakia. The treatment of choice for these diseases is a surgical excision, which always leads to scar formation. Photodynamic therapy provides a new scar-less tool for the treatment.

Topical application of Photofrin® for photodynamic diagnosis of malignant cutaneous neoplasms

OBJECTIVES

The prognosis of patients suffering from malignant cutaneous neoplasms can be improved by early diagnosis. Exact demarcation of tumor margins could contribute to optimum results in surgical excision and reconstruction. The purpose of our study is to evaluate Photofrin^® with a new diagnostic procedure, photodynamic diagnosis (PDD), for the detection of Bowen's disease (squamous cell carcinoma (SCC) in situ), SCC, and basal cell carcinoma (BCC).

MATERIALS AND METHODS

Sixty patients with cutaneous neoplasms received 2.5 mg/mL Photofrin^® solution topically. After a period of 3 hours, the patients underwent fluorescence illumination (λex = 370-450 nm). Guided by their visible fluorescence, lesions were biopsied at four suspicious sites in each patient. All specimens were analyzed and measured by a pathologist. A quantitative analysis of the fluorescence contrast between the neoplasms and healthy tissue was performed using the Red, Blue, and Green (RGB) Mode and Gray Scale (GS). Statistical analysis was performed by the analysis of variance (ANOVA) test for multiple comparisons.

RESULTS

Of the 60 patients (20 Bowen's disease, 20 SCC, and 20 BCC), malignant neoplasms could be clearly distinguished from adjacent healthy tissue under fluorescence illumination (P < 0.0001). The sensitivity of the malignant neoplasms evaluated using the RGB and GS modes combined showed 92.74% in image results. The specificity of the malignant neoplasms evaluated using the RGB and GS modes combined showed 95.77%.

CONCLUSION

Light-induced fluorescence detection using topical Photofrin^® provides a sensitive, noninvasive technique for the early identification of malignant cutaneous neoplasms.

Adjunctive Diagnostic Techniques for Oral and Oropharyngeal Cancer Discovery

The most important prognostic factor in predicting the outcome of oral and oropharyngeal cancer (OPC) is the stage at which it is diagnosed. Only 30% of patients are diagnosed with early-stage disease. The oral health care provider performs an important role in early diagnosis of oral cancer. The conventional oral examination consists of a visual and tactile assessment of accessible oral, and head and neck structures. Any suspicious or equivocal lesion should be reevaluated within 4 weeks. Evidence supporting the use of adjunctive devices to improve the ability to screen for and identify OPCs and oral premalignant lesions remains low.

Firearm Projectile in the Maxillary Tuberosity Located by Adjunctive Examination of Wide-Field Optical Fluorescence

OBJECTIVE

Demonstrate the use of wide-field optical fluorescence as an adjunctive examination in a clinical routine to oral diagnosis.

BACKGROUND DATA

Use of wide-field optical fluorescence in the oral cavity has been restricted to topics related to the detection and diagnosis of oral cancer.

MATERIALS AND METHODS

In a regular medical appointment, a 58-year-old female patient, without any complaint or oral symptom, underwent the complementary examination by wide-field optical fluorescence. A device with high-power light-emitting diode emitting light centered at a wavelength of (400 ± 10) nm and maximum irradiance of (0.040 ± 0.008) W/cm² was used for fluorescence visualization.

RESULTS

We report the location of a firearm projectile, intraosseous, in the maxillary tuberosity using wide-field optical fluorescence.

CONCLUSIONS

It is evidenced that wide-field optical fluorescence, within a clinical routine, can provide relevant images and data, with an immediate result, without the use of ionizing radiation, enabling an efficient oral diagnosis.

Development of thin skin mimicking bilayer solid tissue phantoms for optical spectroscopic studies

In vivo spectroscopic measurements have the proven potential to provide important insight about the changes in tissue during the development of malignancies and thus help to diagnose tissue pathologies. Extraction of intrinsic data in the presence of varying amounts of scatterers and absorbers offers great challenges in the development of such techniques to the clinical level. Fabrication of optical phantoms, tailored to the biochemical as well as morphological features of the target tissue, can help to generate a spectral database for a given optical spectral measurement system. Such databases, along with appropriate pattern matching algorithms, could be integrated with in vivo measurements for any desired quantitative analysis of the target tissue. This paper addresses the fabrication of such soft, photo stable, thin bilayer phantoms, mimicking skin tissue in layer dimensions and optical properties. The performance evaluation of the fabricated set of phantoms is carried out using a portable fluorescence spectral measurement system. The alterations in flavin adenine dinucleotide (FAD)-a tissue fluorophore that provides important information about dysplastic progressions in tissues associated with cancer development based on changes in emission spectra-fluorescence with varied concentrations of absorbers and scatterers present in the phantom are analyzed and the results are presented. Alterations in the emission intensity, shift in emission wavelength and broadening of the emission spectrum were found to be potential markers in the assessment of biochemical changes that occur during the progression of dysplasia.

A study of diagnostic criteria established for two oral mucous diseases by HMME-fluorescence spectroscopy

Malignant oral ulcers are common pathological occurrence in oral and maxillofacial tumors. A noninvasive method for diagnosis of malignant oral ulcers was developed in the study, which is based on hematoporphyrin monomethylether (HMME) fluorescence spectroscopy. The objective of this work is to determine the feasibility of this method in differentiating the malignant tissues from the inflammatory ones in the hamster cheek pouch model. Adult hamsters were used for the study and a cheek pouch model was established. For the malignant model, the 9, 10-dimethyl-1, 2-benzanthracene carcinogenesis was applied to one cheek pouch for 10 weeks (N = 35). The simple ulcers were created on buccal cheek mucosa in a simple manner (N = 10). Prior to sacrifice, HMME solution was injected into the tissues. The induced fluorescence spectra of the cheek tissues were recorded by a fiber spectrometer with excitation at 405 nm. A spectral algorithm was used to eliminate the effect of autofluorescence, and a spectral parameter S was selected as diagnostic criterion. After fluorescence measurement, the animals were sacrificed and the measured tissues were collected. Histological staining was performed and the results of histopathological evaluation were documented. The diagnostic criteria that reflected the fluorescence intensity were set as follows: normal, S ≤ 10; simple ulcer, 230 ≤ S ≤ 290; and malignant ulcer, 140 ≤ S ≤ 200. The sensitivity and specificity of this detection method was verified by scalpel biopsy, and the overall accuracy was over 90%. The results of this study showed that the fluorescence spectroscopic method implemented by HMME can accurately differentiate the two kinds of clinically indistinguishable diseases.

A phase I trial of aminolevulinic acid-photodynamic therapy for treatment of oral leukoplakia

BACKGROUND

Photodynamic therapy with aminolevulinic acid (ALA PDT) for oral leukoplakia has shown promising effects in regression of oral leukoplakia. Although ALA has been extensively studied and is an ideal photosensitizer, the optimal light dose for treatment of oral leukoplakia has not been determined. We conducted a phase I study to determine MTD and DLT of PDT in patients treated with ALA for leukoplakia.

METHODS

Patients with histologically confirmed oral leukoplakia received a single treatment of ALA PDT in cohorts with escalating doses of light (585nm). Clinical, histologic, and biologic markers were assessed.

RESULTS

Analysis of 11 participants is reported. No significant toxicity from ALA PDT was observed in patients who received ALA with a light dose of up to 4J/cm(2). One participant experienced transient grade 3 transaminase elevation due to ALA. One participant had a partial clinical response 3months after treatment. Biologic mucosal risk markers showed no significant associations. Determination of MTD could not be accomplished within a feasible timeframe for completion of the study.

CONCLUSIONS

ALA PDT could be safely administered with a light dose up to 4J/cm(2) and demonstrated activity. Larger studies are needed to fully elucidate the MTD and efficacy of ALA-PDT.

Diagnostic aids for detection of oral precancerous conditions

Oral cancer has a tendency to be detected at late stage which is detrimental to the patients because of its high mortality and morbidity rates. Early detection of oral cancer is therefore important to reduce the burden of this devastating disease. In this review article, the most common oral precancerous lesions are discussed and the importance of early diagnosis is emphasized. In addition, the most common non-invasive oral cancer devices that can aid the general practitioners in early diagnosis are also discussed.

Unique diagnostic and therapeutic roles of porphyrins and phthalocyanines in photodynamic therapy, imaging and theranostics

Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review.

Multimodality approach to optical early detection and mapping of oral neoplasia

Early detection of cancer remains the best way to ensure patient survival and quality of life. Squamous cell carcinoma is usually preceded by dysplasia presenting as white, red, or mixed red and white epithelial lesions on the oral mucosa (leukoplakia, erythroplakia). Dysplastic lesions in the form of erythroplakia can carry a risk for malignant conversion of 90%. A noninvasive diagnostic modality would enable monitoring of these lesions at regular intervals and detection of treatment needs at a very early, relatively harmless stage. The specific aim of this work was to test a multimodality approach [three-dimensional optical coherence tomography (OCT) and polarimetry] to noninvasive diagnosis of oral premalignancy and malignancy using the hamster cheek pouch model (nine hamsters). The results were compared to tissue histopathology. During carcinogenesis, epithelial down grow, eventual loss of basement membrane integrity, and subepithelial invasion were clearly visible with OCT. Polarimetry techniques identified a four to five times increased retardance in sites with squamous cell carcinoma, and two to three times greater retardance in dysplastic sites than in normal tissues. These techniques were particularly useful for mapping areas of field cancerization with multiple lesions, as well as lesion margins.

Gold nanorods for intravital vascular imaging of preneoplastic oral mucosa

We explore the feasibility of using gold nanorods with efficient two-photon luminescence properties as contrast agents for intravital imaging of neoplasia. This investigation spanned ex vivo characterization in cells/tissue to in vivo implementation in an oral carcinogenesis model. GNRs were >40 times brighter than surrounding tissue. Intravital imaging revealed 3D microvasculature, and in dysplasia, abnormal vessels (dense and tortuous) compared to normal. GNRs were diffusely distributed in lesions after 24 hours. No known previous study has revealed abnormal vessel structure in dysplasia by imaging. Results suggest GNRs can function as high-contrast agents for in vivo visualization of carcinogenesis features.

Optical diagnostics in the oral cavity: an overview

As the emphasis shifts from damage mitigation to disease prevention or reversal of early disease in the oral cavity, the need for sensitive and accurate detection and diagnostic tools become more important. Many novel and emergent optical diagnostic modalities for the oral cavity are becoming available to clinicians with a variety of desirable attributes including: (i) non-invasiveness, (ii) absence of ionizing radiation, (iii) patient-friendliness, (iv) real-time information (v) repeatability, and (vi) high-resolution surface and subsurface images. In this article, the principles behind optical diagnostic approaches, their feasibility and applicability for imaging soft and hard tissues, and their potential usefulness as a tool in the diagnosis of oral mucosal lesions, dental pathologies, and other dental applications will be reviewed. The clinical applications of light-based imaging technologies in the oral cavity and of their derivative devices will be discussed to provide the reader with a comprehensive understanding of emergent diagnostic modalities.

Potential of optical coherence tomography for early diagnosis of oral malignancies

With nearly 1,500,000 new patients diagnosed every year in the USA, cancer poses a considerable challenge to healthcare today. Oral cancer is responsible for a sizeable portion of deaths due to cancer, primarily because it is diagnosed at a late stage when the prognosis is poor. Current methods for diagnosing oral cancer need to be augmented by better early detection, monitoring and screening modalities. A new approach is needed that provides real-time, accurate, noninvasive diagnosis. The results of early clinical trials using in vivo optical coherence tomography for the diagnosis of oral dysplasia and malignancy are encouraging.

Multiphoton autofluorescence microscopy and second harmonic generation microscopy of oral epithelial neoplasms

The objective of this study was to evaluate the nonlinear optical microscopy techniques of multiphoton autofluorescence microscopy (MPAM) and second harmonic generation microscopy (SHGM) for noninvasive imaging of oral epithelial carcinogenesis. In vivo imaging was performed in a hamster model for oral carcinogenesis to characterize optical and morphometric alterations during neoplastic transformation. Data is presented showing alterations in morphometry and collagen density during the precancerous phase of neoplastic transformation.

Sufficient PpIX production for PDT even with short contact time of topically applied 5-ALA in rabbit tongues

Although effectiveness of photodynamic therapy (PDT) after application of 5-aminolevulinic acid ointment to oral mucosal lesions has been reported, a consensus regarding recontact time of ALA applied to a lesion has been unreached. Hence, we determined the contact time of ALA required for protoporphyrin IX (PpIX) production efficient for full-blown PDT reaction. ALA ointment was topically applied to healthy rabbits' tongues for different periods and then washed out. On the surface of the tongue, 10-min contact of ALA maximized the PpIX-derived fluorescence. PpIX yield in a tissue specimen with 10-min contact of ALA reached 73% of that in a tissue specimen with 240-min contact. Histological observation showed that PpIX accumulation predominated in the basal layer, and the PDT effects were confined in the mucosal epithelium regardless of contact time. These results suggest that 5-aminolevulinic-acid-ointment-mediated PDT with short contact of ALA is potentially applicable for treating tongue epithelial lesions.

Use of polar decomposition for the diagnosis of oral precancer

The Mueller matrix describes all the polarizing properties of a sample and, therefore, the optical differences between noncancerous and precancerous tissue that may be present within the matrix elements. A high-speed polarimetry system that generates 16 (4x4) full Mueller matrices to characterize tissues is presented. Feature extraction is done on the Mueller matrix elements resulting in depolarization and retardance images by polar decomposition. These are used to detect and classify early oral cancers and precancerous changes in epithelium such as dysplasia. These images are compared with orthogonal polarization images and analyzed in an attempt to identity useful factors for the differentiation between cancerous lesions and their benign counterparts. Our results indicate that polarimetry has potential as a method for the in vivo early detection and diagnosis of oral premalignancy.

Correlation coefficient mapping in fluorescence spectroscopy: tissue classification for cancer detection

Correlation coefficient mapping has been applied to intrinsic fluorescence spectra of colonic tissue for the purpose of cancer diagnosis. Fluorescence emission spectra were collected of 57 colonic tissue sites in a range of 4 physiological conditions: normal (29), hyperplastic (2), adenomatous (5), and cancerous tissues (21). The sample-sample correlation was used to examine the ability of correlation coefficient mapping to determine tissue disease state. The correlation coefficient map indicates two main categories of samples. These categories were found to relate to disease states of the tissue. Sensitivity, selectivity, predictive value positive, and predictive value negative for differentiation between normal tissue and all other categories were all above 92%. This was found to be similar to, or higher than, tissue classification using existing methods of data reduction. Wavelength-wavelength correlation among the samples highlights areas of importance for tissue classification. The two-dimensional correlation map reveals absorption by NADH and hemoglobin in the samples as negative correlation, an effect not obvious from the one-dimensional fluorescence spectra alone. The integrity of tissue was examined in a time series of spectra of a single tissue sample taken after tissue resection. The wavelength-wavelength correlation coefficient map shows the areas of significance for each fluorophore and their relation to each other. NADH displays negative correlation to collagen and FAD, from the absorption of emission or fluorescence resonance energy transfer. The wavelength-wavelength correlation map for the decay set also clearly shows that there are only three fluorophores of importance in the samples, by the well-defined pattern of the map. The sample-sample correlation coefficient map reveals the changes over time and their impact on tissue classification. Correlation coefficient mapping proves to be an effective method for sample classification and cancer detection.

Feasibility of three-dimensional optical coherence tomography and optical Doppler tomography of malignancy in hamster cheek pouches

OBJECTIVE

Hamster cheek pouches (HCP) with various degrees of 9,10-dimethyl-1,2-benzanthracene (DMBA)-induced dysplasia and malignancies were imaged with OCT/ODT in vivo and in vitro to assess the potential for three-dimensional high-resolution optical localization of airway malignancy.

BACKGROUND DATA

Optical coherence tomography (OCT)/optical doppler tomography (ODT) provide potential capability for real-time in vivo high-resolution (2-20 microm) cross-sectional imaging of tissues and spatially resolved blood flow in microvasculature for pathology diagnostics.

METHODS

DMBA was applied to the right side of the cheek pouch (HCP), and mineral oil (control) to the left side three times weekly for 10-18 weeks in Syrian Golden Hamsters using a standard protocol for malignancy induction. HCP were imaged in vivo with OCT/ODT as well as in vitro post-excision, using a prototype 1310-nm broadband superluminescent diode-based OCT/ODT device constructed in our laboratory. Three-dimensional images were constructed, and compared to standard and three-dimensional histology hematoxylin and eosin staining.

RESULTS AND CONCLUSION

OCT imaging offered exceptional resolution of the HCP to depths of 1-2 mm and confirmed ability to detect dysplasia and malignancy. Three-dimensional OCT images were readily constructed, allowing visualization of extent and localization of tumor margins. ODT demonstrated increased vascularity in the area of neoplasia. OCT/ODT is a promising new technology for oral airway diagnostics.

Topical application of photofrin for photodynamic diagnosis of oral neoplasms

BACKGROUND

The prognosis of patients with oral cancer can be improved by early diagnosis. Exact demarcation of tumor margins could contribute to optimum results in surgical excision and reconstruction. Therefore, the purpose of this study was to evaluate Photofrin (Quadra Logic Technologics, Inc., Vancouver, British Columbia, Canada) with protoporphyrin IX fluorescence as a new diagnostic procedure: photodynamic diagnosis for the detection of hyperplastic and malignant changes in oral tissue.

METHODS

Twenty patients with oral neoplasms received 2.5 mg/ml Photofrin solution topically. After a period of 3 hours, the patients underwent fluorescence illumination (lambdaex = 370 to 450 nm). Guided by their visible fluorescence, lesions were biopsied at four suspicious sites for each patient. All specimens were analyzed and measured by a pathologist. A quantitative analysis of the fluorescence contrast between the neoplastic and healthy tissue was performed using the red, green, and blue mode and the gray scale mode. Statistical analysis was performed by means of the analysis of variance test for multiple comparisons.

RESULTS

The sensitivity of the neoplastic tissue evaluated using the red, green, and blue and the gray scale modes combined was 92.45 percent in the macroscopic study and 93.75 percent in the microscopic study. The specificity of the neoplastic tissue evaluated using the red, green, and blue and gray scale modes combined was 95.65 percent in the macroscopic study and 97.50 percent in the microscopic study. Five patients (25 percent) displayed hyperkeratosis, nine (45 percent) displayed squamous hyperplasia, and six (30 percent) displayed squamous cell carcinoma. It is likely that Photofrin induced the visible red fluorescence. Some fluorescence could be detected in the surrounding healthy tissue. The intensity of the light was much lower than that from the lesions. The difference between healthy tissue and the lesions as a group was statistically significant.

CONCLUSIONS

Light-induced fluorescence detection using topical Photofrin provides a sensitive, noninvasive technique for the early identification of malignant neoplasms in the oral cavity. Further study by the authors will evaluate fluorescence-guided photodynamic therapy for oral cancers in early stages.

Noninvasive imaging of oral premalignancy and malignancy

Early detection of cancer and its precursors remains the best way to ensure patient survival and quality of life. Our specific aim is to test a multimodality approach to noninvasive diagnostics of oral premalignancy and malignancy. In the hamster cheek pouch model (120 hamsters), in vivo optical coherence tomography (OCT) and optical Doppler tomography (ODT) map epithelial, subepithelial, and vascular change throughout carcinogenesis. In vivo multiwavelength multiphoton (MPM) and second-harmonic generated (SHG) fluorescence techniques provided parallel data on surface and subsurface tissue structure, specifically collagen presence and structure, cellular presence, and vasculature. Images are diagnosed by two blinded, prestandardized investigators using a scale from 0 to 6 for all modalities. After sacrifice, histopathology is evaluated on a scale of 0 to 6. Imaging data are reproducibly obtained with good accuracy. Carcinogenesis-related structural and vascular changes are clearly visible to tissue depths of 2 mm. Sensitivity (OCT/ODT alone, 71 to 88%; OCT+MPMSHG, 79 to 91%) and specificity (OCT alone, 62 to 83%; OCT+MPMSHG, 67 to 90%) compare well with conventional techniques. Our conclusions are that OCT/ODT and MPM/SHG are promising noninvasive in vivo diagnostic modalities for oral dysplasia and malignancy.

Biophotonic and Other Physical Methods for Characterizing Oral Mucosa

This article discusses biophotonic and other physical methods for characterizing oral mucosa.

Optical coherence tomography of malignancy in hamster cheek pouches

Optical coherence tomography (OCT)/optical Doppler tomography (ODT) provides real-time in vivo high-resolution (10-microm) imaging of tissues and real-time spatially resolved blood flow in microvasculature. Hamster cheek pouches with induced dysplasia and malignancies were imaged with OCT/ODT to assess the potential for application to airway malignancy. In 22 Golden Syrian hamsters, 0.5% 9,10-dimethyl-1,2-benzanthracene induces carcinogenesis over 10 weeks in right side cheek pouches; the left side three served as controls. The cheek pouches are imaged in vivo prior to sacrifice, and in vitro after excision, using a prototype 1310-nm broadband superluminescent diode based OCT/ODT device. Images are compared to standard histopathology. OCT imaging offers good resolution of the hamster cheek pouches to depths of 1 to 3 mm and paralleled histologic images. The feasibility of high-resolution functional imaging is demonstrated in this hamster cheek pouch tumor model. ODT accurately detects vascular change associated with carcinogenesis.

The use of digitized endoscopic imaging of 5-ALA-induced PPIX fluorescence to detect and diagnose oral premalignant and malignant lesions in vivo

5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PPIX) fluorescence has shown an outstanding sensitivity for the assessment of oral lesions, but its application was hampered by low specificity due to the high false-positive rates. The purpose of our study was to explore the feasibility of quantifying PPIX fluorescence images to improve the diagnostic specificity for detecting early oral lesions in vivo. A digitized 5-ALA-mediated endoscopic imaging system was utilized to acquire PPIX fluorescence images from in vivo oral tissues. Forty-nine patients (118 biopsies) with known or suspected premalignant or malignant oral lesions were recruited for ALA-PPIX fluorescence endoscopic imaging. The red and blue channels of PPIX fluorescence images were digitized and stored for fluorescence quantification. The red-to-blue intensity ratios were calculated from the fluorescence images to correlate with histologic findings of the biopsies. The results showed that normal oral mucosa exhibited blue color of the back-scattered excitation light in the fluorescence images, whereas the suspicious lesions displayed bright reddish fluorescence. Applying the red-to-blue intensity ratio (I(R)/I(B)) as a diagnostic algorithm yielded a sensitivity of 92% and 98%, and specificity of 96% and 96%, for separating benign tissue from dysplasia, and cancer tissue, respectively, and a sensitivity and specificity of 98% and 92%, respectively, for differentiating cancer tissue from dysplasia in the oral cavity. Our study demonstrates that quantifying ALA-PPIX fluorescence endoscopic images associated with the red-to-blue intensity ratio as a diagnostic algorithm can provide good differentiation between the different stages of oral premalignancy and malignancy (p<0.0001, unpaired 2-sided Student's t-test), and thus has a potential to significantly improve the noninvasive diagnosis and evaluation of early oral neoplasia in vivo.