Comparative study of protoporphyrin IX fluorescence image enhancement methods to improve an optical imaging system for oral cancer detection

Virtual-freezing fluorescence imaging flow cytometry with 5-aminolevulinic acid stimulation and antibody labeling for detecting all forms of circulating tumor cells

Circulating tumor cells (CTCs) are precursors to cancer metastasis. In blood circulation, they take various forms such as single CTCs, CTC clusters, and CTC-leukocyte clusters, all of which have unique characteristics in terms of physiological function and have been a subject of extensive research in the last several years. Unfortunately, conventional methods are limited in accurately analysing the highly heterogeneous nature of CTCs. Here we present an effective strategy for simultaneously analysing all forms of CTCs in blood by virtual-freezing fluorescence imaging (VIFFI) flow cytometry with 5-aminolevulinic acid (5-ALA) stimulation and antibody labeling. VIFFI is an optomechanical imaging method that virtually freezes the motion of fast-flowing cells on an image sensor to enable high-throughput yet sensitive imaging of every single event. 5-ALA stimulates cancer cells to induce the accumulation of protoporphyrin (PpIX), a red fluorescent substance, making it possible to detect all cancer cells even if they show no expression of the epithelial cell adhesion molecule, a typical CTC biomarker. Although PpIX signals are generally weak, VIFFI flow cytometry can detect them by virtue of its high sensitivity. As a proof-of-principle demonstration of the strategy, we applied cancer cells spiked in blood to the strategy to demonstrate image-based detection and accurate classification of single cancer cells, clusters of cancer cells, and clusters of a cancer cell(s) and a leukocyte(s). To show the clinical utility of our method, we used it to evaluate blood samples of four breast cancer patients and four healthy donors and identified EpCAM-positive PpIX-positive cells in one of the patient samples. Our work paves the way toward the determination of cancer prognosis, the guidance and monitoring of treatment, and the design of antitumor strategies for cancer patients.

Intra-Oral Photograph Analysis for Gingivitis Screening in Orthodontic Patients

This study aimed to confirm the presence of gingival inflammation through image analysis of the papillary gingiva using intra-oral photographs (IOPs) before and after orthodontic treatment and to confirm the possibility of using gingival image analysis for gingivitis screening. Five hundred and eighty-eight (n  =  588) gingival sites from the IOPs of 98 patients were included. Twenty-five participants who had completed their orthodontic treatments and were aged between 20 and 37 were included. Six points on the papillary gingiva were selected in the maxillary and mandibular anterior incisors. The red/green (R/G) ratio values were obtained for the selected gingival images and the modified gingival index (GI) was compared. The change in the R/G values during the orthodontic treatment period appeared in the order of before orthodontic treatment (BO), mid-point of orthodontic treatment (MO), three-quarters of the way through orthodontic treatment (TO), and immediately after debonding (IDO), confirming that it was similar to the change in the GI. The R/G value of the gingiva in the image correlated with the GI. Therefore, it could be used as a major index for gingivitis diagnosis using images.

Use of autofluorescence and fluorescent probes as a potential diagnostic tool for oral cancer: A systematic review

INTRODUCTION

The prognosis of patients with Oral squamous cell carcinoma (OSCC) are directly related to the stage of development of the tumor at the time of diagnosis, but it is estimated an average delay in diagnosis of 2-5 months. New non-invasive techniques for the early diagnosis of OSCC are being developed, such as methodologies to detect spectral changes of tumor cells. We conducted a systematic review to analyze the potential use of autofluorescence and/or fluorescent probes for OSCC diagnosis.

MATERIAL AND METHODS

Four databases (PubMed, Scopus, Embase and Web of Science) were used as research sources. Protocol was registered with PROSPERO. It was included studies that evaluated tissue autofluorescence and/or used fluorescent probes as a method of diagnosing and/or treatment of oral cancer in humans.

RESULTS

Forty-five studies were selected for this systematic review, of which 28 dealt only with autofluorescence, 18 on fluorescent probes and 1 evaluated both methods. The VELscope® was the most used device for autofluorescence, exhibiting sensitivity (33%-100%) and specificity (12%-88.6%). 5-Aminolevulinic acid (5-ALA) was the most used fluorescent probe, exhibiting high sensitivity (90%-100%) and specificity (51.3%-96%). Hypericin, rhodamine 6 G, rhodamine 610, porphyrin and γ-glutamyl hydroxymethyl rhodamine green have also been reported.

CONCLUSION

Thus, the autofluorescence and fluorescent probes can provide an accurate diagnosis of oral cancer, assisting the dentist during daily clinical activity, but it is not yet possible to suggest that this method may replace histopathological examination.

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.