[Non-contact optical coherence tomography - an effective method for visualizing the exudate of the middle ear]

INTRODUCTION

Otitis media with effusion (OME) accounts for 15-17% of the total number of recorded diseases of the middle ear. Surgical methods have become much more common. One of the factors affecting the tactics and effectiveness of treatment OME is the degree of viscosity of the effusion. Modern diagnostic methods do not allow to reliably identify cases of OME with high effusion viscosity.

OBJECTIVE

To study the possibilities of optical coherence tomography (OCT) in the diagnosis of OME and a non-invasive study of effusion viscosity.

MATERIAL AND METHODS

An analysis of the results of the examination of 29 patients who underwent surgical treatment for OME - tympanostomy. A control group of 30 patients without middle ear pathology. The study used a spectral OCT with a non-contact probe designed specifically for studies of the structural middle ear. Quantitative analysis of the results using open source ImageJ. Objectification of the degree of viscosity of the effusion was carried out by means of viscometry. A comparative analysis of the intensity of the optical signal in the external auditory canal (EAC) and in the tympanic cavity (TC) was performed, as well as a comparison of the signal from viscous and fluid effusion.

RESULTS

In all patients with OME, during the OCT study, an optical signal with a higher intensity was recorded in TC than in the EAC. In all cases, in the control group in the TC, an optical signal was recorded that was identical in intensity with the signal in the EAC. When measuring the degree of viscosity of the effusion, 17 cases of OME were characterized as effusion of a low degree of viscosity, 12 cases - effusion of extreme viscosity. When comparing the average intensity of the optical signal of the OCT images of viscous and liquid effusion, a statistically significant difference was revealed, p<0.001.

DISCUSSION

OCT makes it possible to detect light scattering from large scatterers - cell structures characteristic of low viscosity effusion. In addition, OCT allows you to register an optical signal from small scatterers - high molecular weight structures that are present in large quantities in viscous effusion. A correlation was found between the intensity of the optical signal in the TC and the degree of viscosity of the middle ear effusion.

CONCLUSIONS

Based on OCT data, it is possible to determine the indications for surgical treatment of OME by detecting viscous exudate.

Optical coherence angiography for pre-treatment assessment and treatment monitoring following photodynamic therapy: a basal cell carcinoma patient study

Microvascular networks of human basal cell carcinomas (BCC) and surrounding skin were assessed with optical coherence angiography (OCA) in conjunction with photodynamic therapy (PDT). OCA images were collected and analyzed in 31 lesions pre-treatment, and immediately/24 hours/3-12 months post-treatment. Pre-treatment OCA enabled differentiation between prevalent subtypes of BCC (nodular and superficial) and nodular-with-necrotic-core BCC subtypes with a diagnostic accuracy of 78%; this can facilitate more accurate biopsy reducing sampling error and better therapy regimen selection. Post-treatment OCA images at 24 hours were 98% predictive of eventual outcome. Additional findings highlight the importance of pre-treatment necrotic core, vascular metrics associated with hypertrophic scar formation, and early microvascular changes necessary in both tumorous and peri-tumorous regions to ensure treatment success.

Accurate early prediction of tumour response to PDT using optical coherence angiography

Prediction of tumour treatment response may play a crucial role in therapy selection and optimization of its delivery parameters. Here we use optical coherence angiography (OCA) as a minimally-invasive, label-free, real-time bioimaging method to visualize normal and pathological perfused vessels and monitor treatment response following vascular-targeted photodynamic therapy (PDT). Preclinical results are reported in a convenient experimental model (CT-26 colon tumour inoculated in murine ear), enabling controlled PDT and post-treatment OCA monitoring. To accurately predict long-term treatment outcome, a robust and simple microvascular metric is proposed. It is based on perfused vessels density (PVD) at t = 24 hours post PDT, calculated for both tumour and peri-tumour regions. Histological validation in the examined experimental cohort (n = 31 animals) enabled further insight into the excellent predictive power of the derived early-response OCA microvascular metric. The results underscore the key role of peri-tumour microvasculature in determining the long-term PDT response.

[The value of optical coherence tomography and morphometry in evaluating the peripancreatic adipose tissue in infected pancreatic necrosis]

OBJECTIVE

To investigate the morphometric and optical coherence tomography (OCT) characteristics of the microstructure of retroperitoneal peripancreatic adipose tissue during passive drainage and active perfusion-aspiration drainage for infected pancreatic necrosis.

MATERIAL AND METHODS

The authors analyzed 74 samples of peripancreatic adipose tissue obtained from 37 patients with passive (Group 1) and active perfusion-aspiration drainage (Group 2) of a focus of peripancreatitis. The tissues were examined with OCT, then fixed in a formalin solution and underwent histological examination, including morphometric one.

RESULTS

The examined groups showed qualitative and quantitative differences in the tissue microstructure. In Group 1 samples, the proportion (median (upper quartile; lower quartile)) of interlobular connective tissue was 5.6 (3.9; 6.1)%; and that of adipocytes was 44.6 (41.2; 51.6)%. Necrotic tissue occupied 46.2 (35.6; 56.1)% of the area of specimens. The OCT images of necrotic tissue displayed a preponderance of unstructured regions with a high signal level while the parenchymal areas showed a cellular structured pattern. In Group 2 samples, the proportion of interlobular connective tissue was 16.2 (11.4; 19.7)%, and that of adipocytes was 68.5 (59.7; 71.2)%. At the same time, Group 2 exhibited necrosis - 14.4 (11.5; 19.2%) that was 3.2 times less than in Group 1. The OCT images of Group 2 samples showed a preponderance of cellular structured regions characteristic of the parenchyma, with pronounced stromal elements, which corresponded to the histological pattern.

CONCLUSION

Active perfusion-aspiration drainage of peripancreatic adipose tissue versus passive drainage is associated with a smaller proportion of necrotic tissue (14.4% versus 46.2%; p≤0.05) and a larger proportion of a stromal vascular component (16.2% vs. 5.6%; p≤0.05). OCT could qualitatively distinguish viable fat tissue parenchyma from necrotic areas, without specially preparing the samples, which was confirmed by histomorphometric results.

In-vivo longitudinal imaging of microvascular changes in irradiated oral mucosa of radiotherapy cancer patients using optical coherence tomography

Mucositis is the limiting toxicity of radio(chemo)therapy of head and neck cancer. Diagnostics, prophylaxis and correction of this condition demand new accurate and objective approaches. Here we report on an in vivo longitudinal monitoring of the oral mucosa dynamics in 25 patients during the course of radiotherapy of oropharyngeal and nasopharyngeal cancer using multifunctional optical coherence tomography (OCT). A spectral domain OCT system with a specially-designed oral imaging probe was used. Microvasculature visualization was based on temporal speckle variations of the full complex signal evaluated by high-pass filtering of 3D data along the slow scan axis. Angiographic image quantification demonstrated an increase of the vascular density and total length of capillary-like-vessels before visual signs or clinical symptoms of mucositis occur. Especially significant microvascular changes compared to their initial levels occurred when grade two and three mucositis developed. Further, microvascular reaction was seen to be dose-level dependent. OCT monitoring in radiotherapy offers a non-invasive, convenient, label-free quantifiable structural and functional volumetric imaging method suitable for longitudinal human patient studies, furnishing fundamental radiobiological insights and potentially providing useful feedback data to enable adaptive radiotherapy (ART).

Photodynamic therapy monitoring with optical coherence angiography

Photodynamic therapy (PDT) is a promising modern approach for cancer therapy with low normal tissue toxicity. This study was focused on a vascular-targeting Chlorine E6 mediated PDT. A new angiographic imaging approach known as M-mode-like optical coherence angiography (MML-OCA) was able to sensitively detect PDT-induced microvascular alterations in the mouse ear tumour model CT26. Histological analysis showed that the main mechanisms of vascular PDT was thrombosis of blood vessels and hemorrhage, which agrees with angiographic imaging by MML-OCA. Relationship between MML-OCA-detected early microvascular damage post PDT (within 24 hours) and tumour regression/regrowth was confirmed by histology. The advantages of MML-OCA such as direct image acquisition, fast processing, robust and affordable system opto-electronics, and label-free high contrast 3D visualization of the microvasculature suggest attractive possibilities of this method in practical clinical monitoring of cancer therapies with microvascular involvement.

[Optical coherence tomography in surgical treatment of esophageal cancer]

The authors present an analysis of possibilities of optical coherence tomography in preoperative determination of the proximal interface of the tumor. Under investigation there were 24 patients (14 of them with squamous cell carcinoma and 10 with adenocarcinoma), with localization of the process not more than 5 cm the from z-line.

[Optic coherent tomography in evaluation of the buccal mucosa status. Communication 1. Normal mucosa]

The potentialities of optic coherent tomography (OCT) in the diagnosis of the buccal mucosa status were studied and the results are presented in two communications. Communication 1 demonstrates the tomograms of various parts of normal buccal mucosa and methods of their identification as exemplified by analysis of 1180 in vivo and 43 ex vivo OCT images. Using parallel histo-tomographic comparison, the authors distinguished the main signs of optic images, depending on the type of epithelium and characteristic features of the connective tissue stroma in various parts of the buccal mucosa. These signs are essential for understanding the optic images of the mucosa in disease, which will be shown in communication 2.

[Optic coherent tomography: a new high-resolution technology of visualization of tissue structures. Part 1. Principle of the technique. Objects of OCT applications and technical decisions for their study]

The authors present a series of three papers dedicated to studies made in Russia in the field of optic coherent tomography (OCT), the latest noninvasive high-resolution technology of visualization of the structure of biological tissues. A group of medical specialists of different disciplines has been examined over 2,000 patients for 8 years of the use of an original class of the Russian OCT devices developed at the Institute of Applied Physics, Russian Academy of Sciences, and awarded a RF State Prize in the field of science and technology in 1999. The first paper discusses the basic aspects of OCT, the objects of study, and technical decisions for the clinical application of the technique. The paper shows a place of OCT, whose resolving capacity is close to the cellular level (approximately 10-15 microns), among classical methods for imaging biological tissues. The optical images of different types of normal tissues and the method of their identification are demonstrated. It has been found that different optical properties of investing tissues and dentin permit their tomographic differentiation by showing their regular bedded structure. The tomographic pattern of investing tissues is affected by their specific features, such as the type of the lining epithelium, its keratosic processes, and the architecture of the basilar membrane.

In vivo optical coherence tomography imaging of human skin: norm and pathology

BACKGROUND/AIMS: Since the majority of skin diseases are known to be accompanied by structural alterations, research efforts are focused on the development of various novel diagnostic techniques capable of providing in vivo information on the skin structure. An essential parameter here is spatial resolution. In this paper we demonstrate the capabilities of optical coherence tomography (OCT) in detecting in vivo specific features of thin and thick skin. A particular focus is made on the identification of OCT patterns typical of certain pathological processes in skin, by performing parallel histological and tomographical studies. METHODS: To obtain images of the skin, we used a compact fiber OCT system developed at the Institute of Applied Physics of the Russian Academy of Sciences. A low coherence source (superluminescent diode) operated at a wavelength of 1280 nm; the output power was 0.5-2 mW. This power is low enough to conform to the ANSI safety standards for light exposure. The in-depth resolution limited by the spectral bandwidth (40-50 nm) of the probing light was approximately 20 &mgr;m. The lateral resolution determined by the probe light focusing ranged from 15 to 30 &mgr;m. In this series of experiments the maximum depth of imaging did not extend beyond 1.5 mm. Obtaining images of skin regions 2-6 mm long took 2-4 s. OCT capabilities for imaging normal skin of different localization and some skin diseases were studied in 12 healthy volunteers and 24 patients. RESULTS: OCT imaging of the skin can detect in vivo such general pathological reactions of the human body as active inflammation and necrosis. OCT is useful for in vivo diagnosis of some specific processes in the skin, including hyperkeratosis, parakeratosis and formation of intradermal cavities. OCT imaging is noninvasive and therefore allows frequent multifocal examination of skin without any adverse effects. OCT can perform monitoring of disease progress and recovery in the course of therapy. Morphometric studies, measurements of the depth and extension of skin pathology within the human body can be easily performed by OCT. CONCLUSIONS: OCT allows imaging of subsurface soft tissues with the spatial resolution of 15-20 &mgr;m, a resolution one order of magnitude higher than that provided by other clinically available noninvasive diagnostic techniques. An imaging depth of up to 1.5-2 mm, given by current OCT technology, is sufficient to examine the skin. Real time OCT imaging can provide information not only on the structure, but also on some specific features in the functional state, of tissues. OCT imaging is a noninvasive technique, i.e., OCT does not cause trauma and has no side effects since it utilizes radiation in the near infrared wavelength range at a power as low as 1 mW.

In vivo detection of experimentally induced cortical dysgenesis in the adult rat neocortex using optical coherence tomography

Imaging cerebral structure in vivo can be accomplished by many methods, including MRI, ultrasound, and computed tomography. Each offers advantages and disadvantages with respect to the others, but all are limited in spatial resolution to millimeter-scale features when used in routine applications. Optical coherence tomography (OCT) is a new, high resolution imaging technique which uses light to directly image living tissue. Here, we investigate the potential use of OCT for structural imaging of the fully developed mammalian cerebral cortex. In particular, we show that OCT can perform in vivo detection of neocortex and differentiate normal and abnormal cortical anatomy. We present the results of detailed optical coherence tomographic (OCT) observations of both normal and abnormal rat neocortex obtained in vivo. Comparative histologic analysis shows excellent correlation with the OCT tomograms.