Endoscope

Instrument to visually examine the interior of a hollow space

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Drawing of an endoscope for fetal detection, or "fetoscope"

An endoscope is an inspection instrument composed of image sensor, optical lens, light source and mechanical device, which is used to look deep into the body by way of openings such as the mouth or anus. A typical endoscope applies several modern technologies including optics, ergonomics, precision mechanics, electronics, and software engineering. With an endoscope, it is possible to observe lesions that cannot be detected by X-ray, making it useful in medical diagnosis. Endoscopes use tubes which are only a few millimeters thick to transfer illumination in one direction and high-resolution images in real time in the other direction, resulting in minimally invasive surgeries.[1] It is used to examine the internal organs like the throat or esophagus. Specialized instruments are named after their target organ. Examples include the cystoscope (bladder), nephroscope (kidney), bronchoscope (bronchus), arthroscope (joints) and colonoscope (colon), and laparoscope (abdomen or pelvis).[2] They can be used to examine visually and diagnose, or assist in surgery such as an arthroscopy.

Etymology

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"Endo-" is a scientific Latin prefix derived from ancient Greek &#;νδο- (endo-) meaning "within", and "-scope" comes from the modern Latin "-scopium", from the Greek σκοπε&#;ν (skopein) meaning to "look at" or "to examine".[3]

History

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Drawings of Bozzini's "Lichtleiter", an early endoscope

The first endoscope was developed in by German physician Philipp Bozzini with his introduction of a "Lichtleiter" (light conductor) "for the examinations of the canals and cavities of the human body".[4] However, the College of Physicians in Vienna disapproved of such curiosity.[5] The first effective open-tube endoscope was developed by French physician Antonin Jean Desormeaux.[6] He was also the first one to use an endoscope in a successful operation.[7]

After the invention of Thomas Edison, the use of electric light was a major step in the improvement of endoscope. The first such lights were external although sufficiently capable of illumination to allow cystoscopy, hysteroscopy and sigmoidoscopy as well as examination of the nasal (and later thoracic) cavities as was being performed routinely in human patients by Sir Francis Cruise (using his own commercially available endoscope) by in the Mater Misericordiae Hospital in Dublin, Ireland.[8] Later, smaller bulbs became available making internal light possible, for instance in a hysteroscope by Charles David in .[9]

Hans Christian Jacobaeus has been given credit for the first large published series of endoscopic explorations of the abdomen and the thorax with laparoscope () and thoracoscope ()[10] although the first reported thoracoscopic examination in a human was also by Cruise.[11]

Laparoscope was used in the diagnosis of liver and gallbladder disease by Heinz Kalk in the s.[12] Hope reported in on the use of laparoscopy to diagnose ectopic pregnancy.[13] In , Raoul Palmer placed his patients in the Trendelenburg position after gaseous distention of the abdomen and thus was able to reliably perform gynecologic laparoscope.[14]

Georg Wolf, a Berlin manufacturer of rigid endoscopes established in , produced the Sussmann flexible gastroscope in .[15][16] Karl Storz began producing instruments for ENT specialists in through his company, Karl Storz GmbH.[17]

Fiber optics

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A Storz endoscopy unit used for laryngoscopy exams of the vocal folds and the glottis

Basil Hirschowitz, Larry Curtiss, and Wilbur Peters invented the first fiber optic endoscope in .[18] Earlier in the s Harold Hopkins had designed a "fibroscope" consisting of a bundle of flexible glass fibres able to coherently transmit an image. This proved useful both medically and industrially, and subsequent research led to further improvements in image quality.

The previous practice of a small filament lamp on the tip of the endoscope had left the choice of either viewing in a dim red light or increasing the light output &#; which carried the risk of burning the inside of the patient. Alongside the advances to the optics, the ability to 'steer' the tip was developed, as well as innovations in remotely operated surgical instruments contained within the body of the endoscope itself. This was the beginning of "key-hole surgery" as we know it today.[19]

Rod-lens endoscopes

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There were physical limits to the image quality of a fibroscope. A bundle of say 50,000 fibers gives effectively only a 50,000-pixel image, and continued flexing from use breaks fibers and so progressively loses pixels. Eventually so many are lost that the whole bundle must be replaced (at considerable expense). Harold Hopkins realised that any further optical improvement would require a different approach. Previous rigid endoscopes suffered from low light transmittance and poor image quality. The surgical requirement of passing surgical tools as well as the illumination system within the endoscope's tube which itself is limited in dimensions by the human body left very little room for the imaging optics.[citation needed] The tiny lenses of a conventional system required supporting rings that would obscure the bulk of the lens' area. They were also hard to manufacture and assemble and optically nearly useless.[citation needed]

The elegant solution that Hopkins invented was to fill the air-spaces between the 'little lenses' with rods of glass. These rods fitted exactly the endoscope's tube making them self-aligning and requiring of no other support.[citation needed] They were much easier to handle and utilised the maximum possible diameter available.

With the appropriate curvature and coatings to the rod ends and optimal choices of glass-types, all calculated and specified by Hopkins, the image quality was transformed even with tubes of only 1mm in diameter. With a high quality 'telescope' of such small diameter the tools and illumination system could be comfortably housed within an outer tube. Once again, it was Karl Storz who produced the first of these new endoscopes as part of a long and productive partnership between the two men.[20]

Whilst there are regions of the body that will always require flexible endoscopes (principally the gastrointestinal tract), the rigid rod-lens endoscopes have such exceptional performance that they are still the preferred instrument and have enabled modern key-hole surgery.[citation needed] (Harold Hopkins was recognized and honoured for his advancement of medical-optic by the medical community worldwide. It formed a major part of the citation when he was awarded the Rumford Medal by the Royal Society in .)

Composition

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The insertion tip of an endoscope

A typical endoscope is composed of following parts:

• A rigid or flexible tube as a body.
• A light transmission system that illuminates the object to be inpsected. For the light source, it is usually located outside the scope body.
• A lens system that transmits the image from the objective lens to the observer, usually a relay lens system in the case of a rigid endoscope or a bundle of optical fibers in the case of a fiberoptic endoscope.
• An eyepiece which transmits the image to the screen in order to capture it. However, modern videoscopes require no eyepiece.
• An additional channel for medical instruments or manipulators (only for a multi-function endoscope, see below in "Classification").[

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Besides, patients undergoing endoscopy procedure may be offered sedation in to avoid discomfort.

Laparoscopic surgery

Clinical application

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An endoscopy room in a hospital

Endoscopes may be used to investigate symptoms in the digestive system including nausea, vomiting, abdominal pain, difficulty swallowing, and gastrointestinal bleeding.[21] It is also used in diagnosis, most commonly by performing a biopsy to check for conditions such as anemia, bleeding, inflammation, and cancers of the digestive system. The procedure may also be used for treatment such as cauterization of a bleeding vessel, widening a narrow esophagus, clipping off a polyp or removing a foreign object.[citation needed]

Health care workers can use endoscopes to review the following body parts:

Classification

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A rigid endoscope A flexible endoscope

There are many different types of endoscopes for medical examination, so are their classification methods. Generally speaking, the following three classifications are more common:

• According to functions of the endoscope:
  • single-function endoscope: A single-function endoscope refers to an observation mirror that only has an optical system with it.
  • multi-function endoscope: For a multi-functional endoscope, in addition to the function of observation, it also has at least one working channel like lighting, surgery, flushing and other functions.
• According to detection areas reached by the endoscope:
  • enteroscope
  • otoscope
  • colonoscope
  • rhinoscope
  • arthroscope
  • laparoscope
  • etc.
• According to rigidity of the endoscope:
  • rigid endoscope: A rigid endoscope is a prismatic optical system with advantages of clear imaging, multiple working channels and multiple viewpoints.
  • flexible endoscope: A flexible endoscope is an optical-fiber-based system. Notable features of a flexible endoscope include that the lens can be manipulated by the operator to change direction, but the imaging quality is not as good as a rigid one.

Recent developments

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A capsule endoscope

With the development and application of robotic systems, especially surgical robotics, remote surgery has been introduced, in which the surgeon could be at a site far away from the patient. The first remote surgery was called the Lindbergh Operation.[22] And a wireless oesophageal pH measuring devices can now be placed endoscopically, to record ph trends in an area remotely.[23]

• Endoscopy VR simulators

Virtual reality simulators are being developed for training doctors on various endoscopy skills.[24]

• Disposable endoscopy

Disposable endoscopy is an emerging category of endoscopic instruments. Recent developments[25] have allowed the manufacture of endoscopes inexpensive enough to be used on a single patient only. It is meeting a growing demand to lessen the risk of cross contamination and hospital acquired diseases. A European consortium of the SME is working on the DUET (disposable use of endoscopy tool) project to build a disposable endoscope.[26]

• Capsule endoscopy

Capsule endoscopes are pill-sized imaging devices that are swallowed by a patient and then record images of the gastrointestinal tract as they pass through naturally. Images are typically retrieved via wireless data transfer to an external receiver.[27]

The endoscopic images can be combined with other image sources to provide the surgeon with additional information. For instance, the position of an anatomical structure or tumor might be shown in the endoscopic video.[28]

• Image enhancement

Emerging endoscope technologies measure additional properties of light such as optical polarization,[29] optical phase,[30] and additional wavelengths of light to improve contrast.[31]

A low-cost waterproof USB endoscope for non-medical use

Non-medical Use

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• Industrial endoscopic nondestructive testing technology

The above is mainly about the application of endoscopes in medical inspection. In fact, endoscopes are also widely used in industrial field, especially in non-destructive testing and hole exploration. If internal visual inspection of pipes, boilers, cylinders, motors, reactors, heat exchangers, turbines, and other products with narrow, inaccessible cavities and/or channels is to be performed, then the endoscope is an important, if not an indispensable instrument.[32] In such applications they are commonly known as borescopes, [1]

See also

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References

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5.2.1 Endoscopes

Successive improvements in endoscopic technology progressively revolutionized skull base surgery. First generations of endoscopes required cumbersome large lenses, and provided low-definition images with poor illumination. These limitations were gradually surpassed by continuous technological advances, allowing currently available endoscopes and high-definition cameras to render an unprecedented wide, high-definition image of the operative field. Endoscope diameter can be as small as 2.7 mm, which can be extremely useful in young children given the small size of the nostrils and sinus cavities. 3

Currently, most endoscopes used for skull base surgery are rigid rod-lens type and are 18 or 30 cm in length and 2.7 or 4.0 mm in diameter. As light is better transmitted through large-diameter endoscopes because of the larger lens, the 4-mm-diameter endoscopes are the most frequently used. Anatomically, when compared to adults, nasal aperture is significantly narrower in children younger than 7 years. This can significantly limit the endoscopic route in younger patients. 4 In these situations, the narrower 2.7-mm endoscope can be of use. Nonetheless, some authors have reported effective use of the 4-mm endoscope in infants whose body weight was in excess of 2.2 kg. 5 Given the small size of the nasal passages, when using a 4-mm endoscope, the instruments are generally passed solely through the contralateral nostril and not in the same nostril as the endoscope, as is often done in adults. The longer length (30 mm) of the endoscope is helpful in situations where an endoscopic holder is used. The holder arm usually attaches to the shaft of the endoscope, and the long length keeps the bulk of the holding apparatus away from the nares. This allows the surgeon adequate room to maneuver the surgical instruments without hindrance from the holder arm.

The lack of depth perception while using classical 2D endoscopes is now mendable using 3D endoscopes. 6 The visualization of spatial relationships between anatomical structures improves surgical dexterity while shortening the learning curve for endoscopic surgeons. 6 The first-generation 3D endoscopes suffered multiple limitations: large shaft diameter, lack of angled lenses, and decreased resolution. Currently, innovative technology is overcoming these limitations with new generation of endoscopes capable of rendering unprecedented 3D view of the surgical field. 6 The better depth perception facilitates anatomical understanding and safe maneuvering of instruments inside the nasal cavity, which is crucial in pediatric patients with unusual anatomic landmarks, and limited intranasal room. The Visionsense 3D-endoscope, (Visionsense, Philadelphia, PA) has been the most frequently used for endonasal surgery given its 4-mm diameter. However, a new 3D endoscope designed by Karl Storz offers a similar diameter with a dual-lens technology that may provide improved color and optics (&#; Fig. 5.1).

Fig. 5.1 The 30-degree Karl Storz Full HD 3D Endoscope. (This image is provided courtesy of KARL STORZ Endoscopy-America, Inc.)

Several angled endoscope lenses are commercially available. The standard set usually includes 0-, 30-, and 45-degree objective lenses. The 0-degree lens provides a frontal view of the operative field and is the most commonly used. The 30-degree lens is helpful to operate around corners, and rotating the lens brings a larger surface area of the operative field into view. The 45- and 70-degree endoscopes are mostly helpful for inspection. Operating at such acute angles is not only technically challenging, but also very disorienting for most surgeons. The development of adjustable viewing angle endoscopes, such as the EndoCAMeleon (Karl Storz, Tuttlingen, Germany), allows the surgeon to quickly change the lens angle from 0 to 120° by dialing an adjustment knob, providing instantaneous panoramic visualization of the surgical field (&#; Fig. 5.2).

Fig. 5.2 (a) The EndoCAMeleon: the adjustable viewing angle endoscope from Karl Storz. (b) Close-up of the variable viewing angle lens. (These images are provided courtesy of KARL STORZ Endoscopy-America, Inc.)

For illumination, endoscopes are usually coupled to the light source via a fiberoptic cable. Different types of light sources are available (tungsten, halogen, xenon), although currently xenon is the preferred light source for endoscopic skull base surgery, as its spectral characteristics allow for a whiter light than the classic yellow halogen light. 3 The use of fluorescence imaging through the endoscope is possible to visualize fluorescein, 5-aminolevulinic acid (5-ALA), and indocyanine green (ICG). Fluorescein is often used to appreciate cerebrospinal fluid (CSF) leaks, 7 ,&#; 8 ,&#; 9 while 5-ALA and ICG have been used experimentally to distinguish tumor from the normal gland. 10 ,&#; 11 ,&#; 12

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