Intra-operative application of confocal endomicroscopy using a rigid endoscope

Development, Implementation and Application of Confocal Laser Endomicroscopy in Brain, Head and Neck Surgery—A Review

When we talk about visualization methods in surgery, it is important to mention that the diagnosis of tumors and how we define tumor borders intraoperatively in a correct way are two main things that would not be possible to achieve without this grand variety of visualization methods we have at our disposal nowadays. In addition, histopathology also plays a very important role, and its importance cannot be neglected either. Some biopsy specimens, e.g., frozen sections, are examined by a histopathologist and lead to tumor diagnosis and the definition of its borders. Furthermore, surgical resection is a very important point when it comes to prognosis and life survival. Confocal laser endomicroscopy (CLE) is an imaging technique that provides microscopic information on the tissue in real time. CLE of disorders, such as head, neck and brain tumors, has only recently been suggested to contribute to both immediate tumor characterization and detection. It can be used as an additional tool for surgical biopsies during biopsy or surgical procedures and for inspection of resection margins during surgery. In this review, we analyze the development, implementation, advantages and disadvantages as well as the future directions of this technique in neurosurgical and otorhinolaryngological disciplines.

Diagnostic Accuracy of Confocal Laser Endomicroscopy for the Diagnosis of Oral Squamous Cell Carcinoma: A Systematic Review and Meta-Analysis

Background: Advances in treatment approaches for patients with oral squamous cell carcinoma (OSCC) have been unsuccessful in preventing frequent recurrences and distant metastases, leading to a poor prognosis. Early detection and prevention enable an improved 5-year survival and better prognosis. Confocal Laser Endomicroscopy (CLE) is a non-invasive imaging instrument that could enable an earlier diagnosis and possibly help in reducing unnecessary invasive surgical procedures. Objective: To present an up to date systematic review and meta-analysis assessing the diagnostic accuracy of CLE in diagnosing OSCC. Materials and Methods. PubMed, Scopus, and Web of Science databases were explored up to 30 June 2021, to collect articles concerning the diagnosis of OSCC through CLE. Screening: data extraction and appraisal was done by two reviewers. The quality of the methodology followed by the studies included in this review was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. A random effects model was used for the meta-analysis. Results: Six studies were included, leading to a total number of 361 lesions in 213 patients. The pooled sensitivity and specificity were 95% (95% CI, 92–97%; I² = 77.5%) and 93% (95% CI, 90–95%; I² = 68.6%); the pooled positive likelihood ratios and negative likelihood ratios were 10.85 (95% CI, 5.4–21.7; I² = 55.9%) and 0.08 (95% CI, 0.03–0.2; I² = 83.5%); and the pooled diagnostic odds ratio was 174.45 (95% CI, 34.51–881.69; I² = 73.6%). Although risk of bias and heterogeneity is observed, this study validates that CLE may have a noteworthy clinical influence on the diagnosis of OSCC, through its high sensitivity and specificity. Conclusions: This review indicates an exceptionally high sensitivity and specificity of CLE for diagnosing OSCC. Whilst it is a promising diagnostic instrument, the limited number of existing studies and potential risk of bias of included studies does not allow us to draw firm conclusions. A conclusive inference can be drawn when more studies, possibly with homogeneous methodological approach, are performed.

Identification of Bronchoalveolar Lavage Components Applying Confocal Laser Endomicroscopy

BACKGROUND In many studies, confocal laser endomicroscopy (CLE) has proven to be a useful tool in pulmonology; nevertheless, the application in this field is still experimental. By contrast, CLE is almost a standard technique in gastroenterology. The aim of the present study was to demonstrate the identification of bronchoalveolar lavage (BAL) components applying CLE, using a dye. MATERIAL AND METHODS In 21 patients with various underlying diseases a bronchoscopy with BAL was performed. As in routine clinical practice common, BAL fluid (BALF) was analyzed in terms of cytologic, virologic, and microbiologic aspects. To one fraction of BALF, we added acriflavine. After centrifugation CLE was applied and the video sequences were analyzed by an experienced investigator. RESULTS Using CLE, BALF components (such as alveolar macrophages or leucocytes) could be easily identified. A further subdivision of leucocytes (neutrophilic, eosinophilic granulocytes, and lymphocytes) was not possible. Analogous to conventional cytology, a precise distinction of lymphocyte subpopulation (cd 4/cd 8 ratio) was not feasible. In terms of quantification, this is still the application field of flow cytometry and immunohistochemistry. CONCLUSIONS Using CLE, alveolar macrophages and leucocytes in stained BALF can be differentiated independent of smoking status. Further studies should be initiated in order to subclassify leucocytes in eosinophilic, neutrophilic granulocytes, and lymphocytes, which is important for routine clinical practice.

Confocal laser endomicroscopy in head and neck malignancies using FITC-labelled EpCAM- and EGF-R-antibodies in cell lines and tumor biopsies

Intraoperative detection of residual malignant cells at tumor margins following excision of primary tumors could help improving surgery and thus patients' outcome. The feasibility of the tumor antigens epidermal growth factor receptor (EGF-R) and epithelial cell adhesion molecule (EpCAM) for antibody-dependent confocal laser scanning endomicroscopy (CLE)-mediated visualization of malignant cells was addressed. Both tumor antigens are highly and frequently expressed in the majority of carcinomas, including head and neck squamous cell carcinomas (HNSCC), and represent prognostic and therapeutic tumor target molecules. FITC-conjugated EGF-R- and EpCAM-specific antibodies served as molecular tools for the detection of antigen-positive cells using the CLE technology. Specificity of both antibodies and their ability to discriminate tumor from non-tumor cells were assessed in vitro with human fibroblasts and PCI-1 HNSCC cell lines, and ex vivo on primary HNSCC samples (n = 11) and healthy mucosa (n = 5). Antigen specificity of the used EpCAM-specific antibody was superior to that of the EGF-R-specific antibody both in vitro and ex vivo (100% vs. 31.25%), and allowed visualization of cellular structures in CLE measurements. These results hold promise for possible future applications in humans.

Feasibility and reliability of pancreatic cancer staging using a new confocal non-fluorescent microscopy probe: a double-blind study in rats

BACKGROUND

Surgical management of pancreatic cancer depends on tumor resectability and staging. Lymph node (LN) metastases represent an important decision-making factor when it comes to surgical treatment.

AIMS

To evaluate a new in vivo, endoscopic confocal microscopy (CM) system not requiring fluorescence markers, for detection and staging of pancreatic cancer in rats.

METHODS

A confocal system consisting of a confocal scanning laser operating in reflection mode and a dedicated rigid Hopkins rod-lens endoscope were used for in vivo imaging in a rat model of pancreatic ductal adenocarcinoma. A double-blind study compared CM to standard histology in (1) the detection of tumors in rat bearing cancer (n = 11) and controls (n = 6), and (2) in the detection of local nodal involvement at 3 and 6 weeks after tumor induction.

RESULTS

CM detected all pancreatic tumors with 100 % sensitivity and specificity and identified 15 metastatic LNs with an average adenocarcinoma nodule diameter of 2.3 mm (range from 1 to 4.2 mm) out of the 66 examined. CM demonstrated a sensitivity of 87.5 % and a specificity of 98 % in LN detection. The Spearman's rank correlation/rho calculator was of 0.87. CM demonstrated a negative predictive value of 96.1 % and a positive predictive value of 93.3 % in the detection of metastatic LNs.

CONCLUSIONS

Interpretation of confocal images has a high concurrence rate with histopathology examination for primary tumor and lymphatic involvement detection making it a promising technique for in vivo real-time detection and staging of pancreatic cancer. Larger studies are warranted to confirm these preliminary results.

Noninvasive histological imaging of head and neck squamous cell carcinomas using confocal laser endomicroscopy

Confocal laser endomicroscopy (CLE) is an imaging technique that uses miniaturized fiberoptic probes to allow real-time histological imaging of human tissue. An application of CLE in otorhinolaryngology has hardly been investigated so far. In our study, we analyzed the applicability of CLE to visualize cancerous and healthy tissue of the head and neck region. Formalin-fixed tissue specimens from 135 head and neck squamous cell carcinoma (HNSCC) patients and 50 healthy controls were investigated using CLE with and without topical application of acriflavine. Four head and neck surgeons, four pathologists, and four laymen evaluated the CLE images of the HNSCC cases regarding the tumor localization and its border to healthy tissue. The tumor localization and the tumor border were correctly identified in 97 % by the pathologists, 85 % by the head and neck surgeons, and 70 % by the laymen. The main difference in evaluation results was seen in the correct identification of the tumor site (p < 0.05), while there was no significant difference in the identification of the tumor border. CLE is a valuable tool for real-time histological imaging of HNSCCs. It can help to visualize the tumor border and, thereby, facilitate a more precise tumor surgery.

Confocal Laser Endomicroscopy in the Detection of Head and Neck Precancerous Lesions

Objective

This study aimed to determine the feasibility of using probe-based confocal laser endomicroscopy (pCLE) in the diagnostic differentiation of non-neoplastic lesions from precancerous and cancerous lesions of head and neck patients.

Study Design

Diagnostic test evaluation.

Setting

Louisiana State University Health Shreveport.

Subjects and Methods

Intravenous injection of fluorescein was given to patients with precancerous and cancerous head and neck lesions (n = 21) followed by the use of a 1.8-mm GastroFlex probe in the oral cavity with subsequent biopsies of selected areas. Probe-based confocal laser endomicroscopy images were compared to histologic evaluation of visualized sites using sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV).

Results

The dorsal surface of the tongue was not well visualized. The remaining nonkeratinized subsites, including the buccal mucosa, floor of mouth, and ventral tongue, were well visualized. Diagnoses based on pCLE images correlated well with the gold standard diagnoses based on tissue histology. The overall sensitivity for diagnosis of dysplasia versus nondysplasia was 80.0% (95% confidence interval [CI], 62.0-98.0), specificity and PPV were 100%, and the NPV was 80.0% (95% CI, 60.0-100.0). The overall specificity, sensitivity, PPV, and NPV for pCLE diagnosis of carcinoma versus nondysplasia were 100%. The overall sensitivity for diagnosis of carcinoma versus dysplasia was 85.7% (95% CI, 73.0-99.0), specificity and PPV were 100%, and the NPV was 80.0% (95% CI, 60.0-100.0).

Conclusion

The pCLE is a promising method for differentiating between nondysplastic, precancerous, and cancerous lesions of the head and neck.