Confocal endoscopy | |
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Confocal endoscopy, or confocal laser endomicroscopy (CLE), is a modern imaging technique that allows the examination of real-time microscopic and histological features inside the body. In the word "endomicroscopy", endo- means "within" and -skopein means "to view or observe". CLE, also known as "optical biopsy", can analyse histology and cytology features of a tissue which otherwise is only possible by tissue biopsy. Similar to confocal microscopy, the laser in CLE filtered by the pinhole excites the fluorescent dye through a beam splitter and objective lens. The fluorescent emission then follows similar paths into the detector. A pinhole is used to select emissions from the desired focal plane. Two categories of CLE exist, namely probe-based (pCLE) and the less common endoscopy-based endoscopy (eCLE). [1]
CLE can be intubated to study the gastrointestinal (GI) tract and accessory digestive organs with a fluorescent dye. A variety of diseases, including inflammatory bowel disease (IBD) and Barrett's oesophagus, can be diagnosed by the magnified and in-depth view in combination with traditional endoscopy. [2]
CLE can identify the lesions with a small depths of view under the tissue, in contrast to the surface level in conventional endoscopy. [3] It also allows clinicians to discriminate benign or malignant lesions through real-time histological diagnosis by revealing the properties of the lamina at a cellular level. [3] [4]
An example is Whipple's disease. [5] Conventional endoscopy presents a whitish-patterned duodenal mucosa. CLE, in comparison, generates two images –– the superficial images show capillary leak in duodenal mucosa while the deep images show cells of duodenal mucosa, including goblet cells and foamy macrophages in lamina propria. Compared to histological examination of the same duodenal site after periodic acid-Schiff staining, CLE identifies similar patterns of goblet cells and foamy macrophages. [5]
Two types of CLE have been invented, namely probe-based (pCLE) and endoscope-based CLE (eCLE).
pCLE, developed by Mauna Kea Technologies, is a fibre bundle transit through the 2.8 mm working channel (the hollow hole) of the standard endoscope into the GI tract. [1] With a fixed plane of imaging, each fibre acts as a pinhole to filter unwanted noise. The frame rate lies between 9 and 12 images/second. [1]
pCLE Products | Usage |
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GastroFlex | Upper GI |
ConolFlex | Lower GI |
CholangioFlex | Cholangiopancreatography |
AQ-19 | Fine needle aspiration |
Needle-based CLE | Endoscopic ultrasound needle (EUS) |
eCLE, developed by Pentax, is a confocal microscopy fixed at the end of the endoscopic tube. The integrated machine of eCLE is larger than the pCLE in diameter, making GI tract endoscopic intubation more difficult. eCLE has ceased commercially due to the camera's inflexibility. [1]
CLE is effective in detecting premalignant, including Barrett's oesophagus, and malignant (cancerous) lesions in the upper GI tract. [3] [6] [7] The modifications of mucosa shown in histopathology as an index of malignancy can be identified under CLE, such as high-grade dysplasia. CLE can also be implemented to refer to the treatment of Barrett's oesophagus by measuring the lateral extent of neoplasia. [3] [7]
The Miami classification is the most popular system in oesophageal CLE diagnosis. [6] [8]
Similar to that of the oesophagus, CLE is able to detect early gastric cancer, as well as premalignant conditions, such as gastritis and intestinal metaplasia. [1] [2] [6] CLE can detect and distinguish the stomach pit patterns to identify the disease in accordance with the Miami classification, which was refined in 2016 to include both pit patterns and the architecture of blood vessels. [1] [2] [8] [9] The refined classification allows clinicians to differentiate between neoplastic and non-neoplastic lesions. [9]
The presence of Helicobacter pylori can also be identified using CLE by viewing the morphological changes in tissues. [10] [11]
CLE reveals "soccer ball-like pattern" of narrower capillaries in malignant lymphomas; distorted architecture and fluorescein leakage from lumen in colonic adenocarcinoma; and blunt-shaped villi and crypts and increased intraepithelial lymphocytes in coeliac disease. [1] [2] [12]
CLE can be utilized to identify adenoma and neoplasia in colorectal polyps and lesions. [13] [14] The Miami classification provides guidelines for clinicians to differentiate neoplastic and non-neoplastic lesions. [8]
CLE can be used for the identification of IBD and its subtypes (Crohn's disease and ulcerative colitis) based on the observation on morphological characteristics, such as architectural distortion, lowered crypt density, crypt irregularity and an abnormally high density of epithelial gaps. [1] [2] [15] The prediction of IBD progression on non-inflamed epithelium is achievable, too, making way for a novel "treat-to-target" therapeutic approach. [1] [2]
Incorporating an EUS, CLE can accurately diagnose pancreatic cystic lesions, including mucinous and non-mucinous lesions. [2] [16] Special needles are used to collect fluid and cyst wall tissues for testing. [16] Pancreatic ductal adenocarcinoma (PDAC) can also be viewed by CLE. [4] Observing cystic lesions and PDAC, clinicians can identify early chronic pancreatitis and determine the malignancies of lesions. [4]
Biliary stricture can be viewed by CLE. [1] The Miami and Paris classifications can be adapted to differentiate cancerous and inflammatory causes. [17]
The discrimination of inflammation and malignant tumor in lung and the urinary system may be done by using CLE and this is currently under research. [10] [18] Some usages such as oral and other head-and-neck cancer diagnosis have been proposed. [19] [20]
Antibodies of molecular targets are used to diagnose GI diseases by histology. [21] [22] CLE captures the fluorescence produced by specific antibodies binding to vascular endothelial growth factor (VEGF). Comparing the significant difference in fluorescent strength, clinicians can differentiate normal and neoplastic tissue. Molecular imaging with antibodies may be applied to CLE as a diagnostic benchmark due to high correlation with ex vivo microscopy. [21]
The molecular imaging technique can be used in a similar manner in the examination of head and neck cancer using CLE, though the diagnostic targets may be different from those in the gastrointestinal tract. [20] [23]
The laser emitted by CLE through a pinhole is reflected by the beam splitter or a dichroic mirror and focused by an objective lens. The fluorescent dye in targeted tissue is excited and emits a specific wavelength. The emission from the focal plane of the tissue then is collected by the objective lens and the beam splitter. The laser is eventually filtered by a pinhole to reduce out-of-focus noise to enter the detector or photomultiplier tube. [1]
Cresyl violet and acriflavine can be used as topical dyes. Cresyl violet is a common stain in histology used for light microscopy sections, especially brain sections. In CLE, it can enhance the viewing of the cytoplasm, yet it limits tissue penetration and does not show anything about vasculature. Acriflavine is an antiseptic and dye. In CLE, it can stain the nuclei of GI surface epithelial cells. It is however subjected to cytotoxic and mutagenic properties, in addition to common side effects of irritation. [1]
Fluorescein is the most popular IV dye for CLE. Fluorescein is an FDA-cleared dye that is used in ophthalmology clinics in routine as it appears green under cobalt blue light. [12] It is commonly applied topically to identify corneal diseases with slit lamp microscopes including corneal abrasion, ulcers, and infections; or intravenously to identify retinal diseases with angiography including macular degeneration and diabetic retinopathy. In CLE, it is usually administered intravenously immediately before the intubation of an endoscopic tube. The fluorescence is reported to be the most prominent from a few seconds to 8 minutes. [1] Fluorescein is slowly eliminated; thus the fluorescence slowly decays up to a minimal detectable level after 1 hour, giving a time window for clinicians to investigate. [1]
CLE's narrow field of vision makes it difficult for clinicians to identify the location and path of the probe, making it challenging to correspond the image obtained and the lesion location and direction. Research has proposed a crypt recognition algorithm, which predicts the pixel displacement by the moving angle and distance. By restoring the exploration path of CLE, clinicians can locate the sites of interest and improve diagnostic efficiency. [24]
Research has proposed a new assessment method for filtering images yielded from CLE. As CLE often encounters image distortions, the degradation of image quality and loss of image information, eventually increase the difficulty of accurate diagnosis. [25] A new image quality assessment (IQA) utilising Weber's Law and local descriptors assesses the quality and filters images with low diagnostic value. [25]
The variety of pathology conditions identifiable by CLE is limited. [3] The histological diagnosis is limited to cancerous lesions and inflammation where the number of specific diseases identifiable is not numerous. Moreover, it requires specific training to operate CLE and correctly interpret CLE images, which are rarely used skills by experts in endoscopy. [10] [14] Owing to the narrow field of view, the applications of CLE might be restricted. [1] Computer-aided diagnosis with AI technology may be beneficial in diagnosing CLE images. [2]
Fluorescein is the only safe dye approved while cresyl violet and acriflavine are commonly used agents. The lack of choice of contrast agents may limit the application of CLE. [2] For instance, patients allergic to fluorescein should never undergo CLE that involves the use of this intravenous dye. [4]
The optical system consists of complex microscopic optical instruments, which are difficult to manufacture and assemble. [2] Therefore, the tool is expensive. [3]
CLE is mostly used in combination with other techniques instead of replacing conventional endoscopy with biopsy. [7] CLE can only serve as a complementary to the traditional biopsy. By sharing the same working channel, conventional biopsy and CLE can be done alternatively by single intubation. [2]
The allergic properties of fluorescein, the common intravenous fluorescent dye for CLE, is the major culprit for the mild adverse events. [13]
CLE, similar to other diagnostic endoscopic techniques, may give rise to pancreatitis when used to examine the pancreas. [13] [26] The likelihood for pancreatitis is especially high in needle-based CLE. The incidence can be minimized by shortening the inspection time and avoiding excessive needle movement within the pancreatic cyst wall. [13]
Mild side effects, which are rare, include [1]
These effects are manageable unless patients have prior experiences of them. [1]
Cases of anaphylaxis are reported by ophthalmological uses of fluorescein. Prophylactic use of antihistamines can reduce the chances of allergic reactions or skin prick tests can identify the risk of allergic reactions. [1]
Acriflavine, another contrast agent for CLE, is potentially carcinogenic to humans due to its known mutagenic ability. The dye is therefore not approved by the FDA. [13]
CLE is a modern, in vivo adaptation of confocal microscopy, the microscopic technique invented by Marvin Minsky in 1957. [10]
Since 2004, CLE has been used for observing histopathological changes in gastrointestinal tissues. [10]
Pathology is the study of disease. The word pathology also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatment, the term is often used in a narrower fashion to refer to processes and tests that fall within the contemporary medical field of "general pathology", an area that includes a number of distinct but inter-related medical specialties that diagnose disease, mostly through analysis of tissue and human cell samples. Idiomatically, "a pathology" may also refer to the predicted or actual progression of particular diseases. The suffix pathy is sometimes used to indicate a state of disease in cases of both physical ailment and psychological conditions. A physician practicing pathology is called a pathologist.
Coeliac disease or celiac disease is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barley. Classic symptoms include gastrointestinal problems such as chronic diarrhoea, abdominal distention, malabsorption, loss of appetite, and among children failure to grow normally. Non-classic symptoms are more common, especially in people older than two years. There may be mild or absent gastrointestinal symptoms, a wide number of symptoms involving any part of the body, or no obvious symptoms. Coeliac disease was first described in childhood; however, it may develop at any age. It is associated with other autoimmune diseases, such as Type 1 diabetes mellitus and Hashimoto's thyroiditis, among others.
Barrett's esophagus is a condition in which there is an abnormal (metaplastic) change in the mucosal cells lining the lower portion of the esophagus, from stratified squamous epithelium to simple columnar epithelium with interspersed goblet cells that are normally present only in the small intestine and large intestine. This change is considered to be a premalignant condition because of its potential to further transition to esophageal adenocarcinoma, an often-deadly cancer.
A biopsy is a medical test commonly performed by a surgeon, an interventional radiologist, or an interventional cardiologist. The process involves the extraction of sample cells or tissues for examination to determine the presence or extent of a disease. The tissue is then fixed, dehydrated, embedded, sectioned, stained and mounted before it is generally examined under a microscope by a pathologist; it may also be analyzed chemically. When an entire lump or suspicious area is removed, the procedure is called an excisional biopsy. An incisional biopsy or core biopsy samples a portion of the abnormal tissue without attempting to remove the entire lesion or tumor. When a sample of tissue or fluid is removed with a needle in such a way that cells are removed without preserving the histological architecture of the tissue cells, the procedure is called a needle aspiration biopsy. Biopsies are most commonly performed for insight into possible cancerous or inflammatory conditions.
MALT lymphoma is a form of lymphoma involving the mucosa-associated lymphoid tissue (MALT), frequently of the stomach, but virtually any mucosal site can be affected. It is a cancer originating from B cells in the marginal zone of the MALT.
Eosinophilic esophagitis (EoE) is an allergic inflammatory condition of the esophagus that involves eosinophils, a type of white blood cell. In healthy individuals, the esophagus is typically devoid of eosinophils. In EoE, eosinophils migrate to the esophagus in large numbers. When a trigger food is eaten, the eosinophils contribute to tissue damage and inflammation. Symptoms include swallowing difficulty, food impaction, vomiting, and heartburn.
Surgical pathology is the most significant and time-consuming area of practice for most anatomical pathologists. Surgical pathology involves gross and microscopic examination of surgical specimens, as well as biopsies submitted by surgeons and non-surgeons such as general internists, medical subspecialists, dermatologists, and interventional radiologists.
Skin biopsy is a biopsy technique in which a skin lesion is removed to be sent to a pathologist to render a microscopic diagnosis. It is usually done under local anesthetic in a physician's office, and results are often available in 4 to 10 days. It is commonly performed by dermatologists. Skin biopsies are also done by family physicians, internists, surgeons, and other specialties. However, performed incorrectly, and without appropriate clinical information, a pathologist's interpretation of a skin biopsy can be severely limited, and therefore doctors and patients may forgo traditional biopsy techniques and instead choose Mohs surgery.
Cytomegalovirus esophagitis is a form of esophagitis associated with cytomegalovirus. Symptoms include dysphagia, upper abdominal pain, diarrhea, nausea, vomiting, and sometimes hematemesis. This condition occurs in the setting of patients with a weakened immune system who are susceptible to both infections by CMV and the manifestation of symptoms. A large majority of patient that have CMV Esophagitis are diagnosed with HIV. Another significant segment of the population have weakened immune systems through transplant surgery, diabetes, or due to medication. Diagnosis is done primarily by endoscopy with biopsy, as CMV Esophagitis has a distinctive pathology pattern of linear ulcers.
Indocyanine green (ICG) is a cyanine dye used to diagnostics. It is used for determining cardiac output, hepatic function, liver and gastric blood flow, and for ophthalmic and cerebral angiography. It has a peak spectral absorption at about 800 nm. These infrared frequencies penetrate retinal layers, allowing ICG angiography to image deeper patterns of circulation than fluorescein angiography. ICG binds tightly to plasma proteins and becomes confined to the vascular system. ICG has a half-life of 150 to 180 seconds and is removed from circulation exclusively by the liver to bile.
Blue rubber bleb nevus syndrome is a rare disorder that consists mainly of abnormal blood vessels affecting the skin or internal organs – usually the gastrointestinal tract. The disease is characterized by the presence of fluid-filled blisters (blebs) as visible, circumscribed, chronic lesions (nevi).
Mauna Kea Technologies is a global medical device company focused on endomicroscopy, the field of microscopic imaging during endoscopy procedures. The company researches, develops and markets tools to visualize, detect, and rule out abnormalities including malignant and pre-malignant tumors or lesions in the gastrointestinal and pulmonary tracts.
Endoexoenteric refers to a specific radiographic manifestation of lymphoma of the bowel.
Herpes esophagitis is a viral infection of the esophagus caused by Herpes simplex virus (HSV).
An inflammatory fibroid polyp(IFP) is an uncommon digestive system tumor. J. Vanek initially identified it as a separate pathological entity in 1949 when he reported six case reports of eosinophilic infiltration in gastric submucosal granulomas. It is a single, non-encapsulated polypoid lesion that is typically submucosal. It is characterized by a large number of small blood vessels, oedematous connective tissue, and an inflammatory eosinophilic infiltrate.
Endomicroscopy is a technique for obtaining histology-like images from inside the human body in real-time, a process known as ‘optical biopsy’. It generally refers to fluorescence confocal microscopy, although multi-photon microscopy and optical coherence tomography have also been adapted for endoscopic use. Commercially available clinical and pre-clinical endomicroscopes can achieve a resolution on the order of a micrometre, have a field-of-view of several hundred μm, and are compatible with fluorophores which are excitable using 488 nm laser light. The main clinical applications are currently in imaging of the tumour margins of the brain and gastro-intestinal tract, particularly for the diagnosis and characterisation of Barrett’s Esophagus, pancreatic cysts and colorectal lesions. A number of pre-clinical and transnational applications have been developed for endomicroscopy as it enables researchers to perform live animal imaging. Major pre-clinical applications are in gastro-intestinal tract, toumour margin detection, uterine complications, ischaemia, live imaging of cartilage and tendon and organoid imaging.
Gastrointestinal intraepithelial neoplasia is also known as gastrointestinal dysplasia. Gastrointestinal dysplasia refers to abnormal growth of the epithelial tissue lining the gastrointestinal tract including the esophagus, stomach, and colon. Pancreatic, biliary, and rectal Intraepithelial Neoplasia are discussed separately. The regions of abnormal growth are confined by the basement membrane adjacent to the epithelial tissue and are thought to represent pre-cancerous lesions.
The gluten challenge test is a medical test in which gluten-containing foods are consumed and (re-)occurrence of symptoms is observed afterwards to determine whether and how much a person reacts to these foods. The test may be performed in people with suspected gluten-related disorders in very specific occasions and under medical supervision, for example in people who had started a gluten-free diet without performing duodenal biopsy.
Michel Kahaleh is an American gastroenterologist and an expert in therapeutic endoscopy.
Colonic ulcer can occur at any age, in children however they are rare. Most common symptoms are abdominal pain and hematochezia.