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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_605_Библиотеки_им_академика_М_И_Перельмана.pdf
161Diagnostic Procedures
Rigid endoscopes are commonly used in minimally invasive surgical
procedures like rhinoscopy (nose), cystoscopy (urinary bladder), and laparoscopy (abdomen).
Rigid endoscopes are made of metal tubes which contain the lenses, and
the light channel(s) and are available in a large range of external diameters,
from 1 to 12 mm.
Commonly, rigid endoscopes have a series of high-resolution optical
glass rod lenses. The endoscopes can be forward viewing (0 deg rees) or
angled (10120 degrees) to allow visualization out of the axis of the telescope and increase the FOV by rotating the instrument. The optical quality of lens-generated images of rigid endoscopes still surpasses that of the
fiber-optic or digital images produced by flexible scopes.
In gastrointestinal surgery, however, rigid endoscopy for diagnostic
purposes (diagnostic laparoscopy) completely lost its former role.
Nowadays, laparoscopy is performed almost exclusively as a therapeutic
procedure (see Chapter 7: Operative (Surgical) Laparoscopy).
In visceral medicine flexible endoscopy dominates now for the exploration of the whole GI tract from the interior (endoluminally).
5.7.2 Flexible Diagnostic Endoscopy
With flexible endoscopes, it is possible to advance through twisted paths of
the body. They consist of an elongated plastic-coated endoscope sheath containing optical components such as the objective lens and the image guide as
well as the light-transmitting glass fibers. There are two types of flexible
endoscopes: fiber-optic and video endoscopes. Video endoscopes use digital
image transmission, whereas fiber-optic endoscopes, also called fiberscopes
or fiber endoscopes, use glass fiber bundles to transmit images. These individual fibers have a diameter between 4 and 14 µm. Between 3000 and
50,000 fibers are used, depending on the diameter and field of use.
Flexible endoscopes are most commonly used in areas of the body
cavity that are difficult to access, like the gastrointestinal, respiratory, and
male urinary tracts. A special design of flexible endoscopes is the catheter
endoscope, which enables intravascular image acquisition. They are
mostly used during intravascular US and have a great potential in intravascular OCT image acquisition.
Flexible endoscopes are considerably more expensiv e and require more
maintenance than rigid endoscopes. One impr ovement in flexible endoscopy
is the creation of portable or handheld units. This has been possible due to
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Biomedical Engineering in Gastrointestinal Surgery
Figure 5.34 Portable unit for flexible endoscopy (Storz Gastropack) (TFT flat screen
folded down). It offers all basic functionalities, making it suitable for many applications
outside the endoscopy unit (intensive care unit, outpatient department, etc.). From MITI.
technical advancements in miniaturization. Due to its higher flexible usability,
it is beneficial, e.g., in emergencies and for intensive care units (
Fig. 5.34).
In principle, an endoscope is a hollow hose that is inserted into the
human body.
Most endoscopic procedures involve more than a simple visual examination. Diagnostic and therapeutic procedures demand a wide range of
specialized accessories. Besides the imaging equipment, numerous peripheral devices and instruments such as lights, insufflators, suction and irrigation equipment, forceps, snares, loops, drains, stents, balloons, dilators,
needles, blades, and many other tools are required.
Combination with other imaging modalities, like US or optical imaging systems, is generally possible. This requires a miniaturization of the
respective technology. In the following section, important and novel visualization technologies for endoscopes are presented. Promising new imaging techniques, including fluorescence endoscopy, OCT, confocal
microendoscopy, and molecular imaging, are briefly depicted.
5.7.2.1 Flexible Scopes
Standard video gastroscopes (for the examination of the esophagus, the
stomach, and the duodenum) or colonoscopes (for the examination of
the large bowel) have a direct forward view. The flexible shaft is not
Diagnostic Procedures
Figure 5.35 “ Classical” flexible gastroenterological endoscope with the main compo-
nents shaft, handle, and connecting cable. From MITI.
163
actively controlled, but the flexible tip can be bent in two axes by two
wheels at the handle (
5.7.2.1.1 The Handle
Fig. 5.35).
The handle is held by the endoscopist’s left hand at the grip. The fingers
of his left hand additionally activate the suction and instillation pins
(
Fig. 5.36).
The fingers of his right hand usually move the smaller steering wheel
(for the x-axis) whereas the larger, inner steering wheel is turned by
the thumb of the left hand. This sounds more complicated as it is.
Experienced endoscopists are able to perform most sophisticated manipulations with ease.
If the suction pin is pressed, aspiration into the working channel is initiated. If the hole in the air/water pin is gently occluded by a fingertip,
gas/air will be insufflated. If it is pressed down, water will be flushed to
clear the view or to clean the working site.
The challenge is to integrate the maximum of functionality into a
minimal diameter of the tip/shaft and to facilitate the navigation
(
Fig. 5.37A, B).
5.7.2.1.2 Connection to the Control/Supply Unit
A key issue of flexible endoscopy is a fast and safe connection of the flexible endoscope to the control/supply unit.
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Biomedical Engineering in Gastrointestinal Surgery
Figure 5.36 Close-up view of the handle of a standard video endoscope. From MITI.
Figure 5.37 Tip of the flexible endoscope: (A) Standard diagnostic endoscope. A
biopsy forceps is inserted through the working channel. (B) Two-channel endoscope.
All from MITI.
Multiple functionalities have to be transferred though this needle hole
(
Fig. 5.38).
5.7.2.2 Control/Support Unit
In opposition to the architecture of laparoscopy units, the necessary
peripheral functionality of the control/support units are integrated into
one entity.
These compact units of only two or three elements provide the deci-
sive functions of a state-of-the-art flexible endoscope (
5.7.2.2.1 Imaging/Illumination
Fig. 5.39).
The main components of the control/support unit are the image processor and the light source (
Fig. 5.40).
Diagnostic Procedures
Figure 5.38 Connector: Light, vacuum, optical transmission, irrigation have to be
provided to the tip of the endoscope. From MITI.
165
Figure 5.39 Control/support peripheral unit for flexible gastroenterological endoscopy. From MITI.
5.7.2.2.2 Suction/Irrigation/Insufflation
In flexible endoscopy, the necessary conditions have to be created by
insufflating gas into the respective part of the gastrointestinal tract to get
the overview. Usually, normal air is suitable, since the danger of air
embolism (as in laparoscopy) is practically nonexistent in flexible diagnostic endoscopy. However, the use of CO
is becoming increasingly popular
2
since it is assumed to be more patient-friendly (in particular during colonoscopy), since it is reabsorpted faster. The pump is integrated with the
processor into one common housing.
Water is required to wash the mucosa of the gastrointestinal tract and/
or the lens of the endoscope to get a better visualization (“flushing”).
Flushing pumps are mostly provided as roller pumps. Technically more
simple are pressurized bottles (
Fig. 5.41A). Aspiration can be achieved by
using the vacuum line of the OR. The aspirated fluid is stored in bottles
or disposable bags (
Fig. 5.41B).
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Biomedical Engineering in Gastrointestinal Surgery
Figure 5.40 Various functions are available: White balancing adapts the ima ge sensor to the color temperature of the light at the pickup location and ensures a correct representation of the colors. Since light emission differs between the various
endoscopes, and is also caused by different numbers of fibers for light transmission, white balancing has to be performed before every examination and after a
change of the endoscope. Image enhancement: Fine patterns or edges in the
image can be enhanced electronically. Modern processors even provide a fog-free
function. From MITI.
5.7.2.3 Instruments
The most important instrument in flexible diagnostic endoscopy is the
biopsy forceps for tissue sampling (
Fig. 5.42). Biopsy forceps are available
with various jaws and in all diameters.
Because of their simple functioning (
Fig. 5.43), production costs are
low and they are offered as disposables. The required force at the jaws is
comparatively low.
Diagnostic Procedures
167
Figure 5.41 (A) Irrigation water bottle with connecting hose; (B) suction: disposable
bag for the aspirated fluid. All from MITI.
Figure 5.42 Typical biopsy forceps for flexible endoscopy. The sharp tip of the upper
one facilitates the stable positioning of the jaws. From MITI.
Figure 5.43 Handle of a biopsy forceps: the open/close function is activated by moving the cylindrical structure forward and backward with two fingers. The thumb is
positioned within the ring. From MITI.
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Biomedical Engineering in Gastrointestinal Surgery
5.7.2.4 The Endoscopic Trolley
The whole range of electromechanical devices is mostly stored in mobile
workstations (
Fig. 5.44). They also incorporate the monitor. By moving
the trolley, the video screen can be positioned for convenience. The
devices are controlled by the central switch, allowing all equipment to be
powered up simultaneously for time-saving.
5.7.2.5 Instrument Reprocessing
Flexible endoscopes are complex devices which require careful reprocessing before being used in subsequent patients. The normal reprocessing
procedures used for surgical instruments would inevitably lead to complete destruction.
Accordingly, adequate reprocessing procedures had to be developed
with the aim to obtain decontamination and high-level disinfection.
Flexible endoscopes should first be completely cleaned to remove any
bioburden, in particular proteins.
Subsequently, high-level disinfection is achieved by exposure to 2% glutaraldehyde solution at B25˚C. Glutaraldehyde has an excellent biocidal
activity and is relatively inexpensive. It does not degrade endoscopes, since
it is noncorrosive to metal, rubbers, and plastics. However, the endoscopes
Figure 5.44 Mobile endoscopy unit. From MITI.
Diagnostic Procedures
Figure 5.45 Automated endoscope reprocessor. From MITI.
169
have to be thoroughly rinsed after treatment with glutaraldehyde since it is
highly irritating on human mucosa and eyes. It fixes proteins which allows
for biofilm formation if the endoscope had not been meticulously cleaned
before disinfection. Alternatives to glutaraldehyde are ortho-phthalaldehyde
(does not coagulate blood or fix tissue to the surface), peracetic acid, and
hydrogen peroxide.
Manual high-level disinfection is possible, but usually specially
designed machines are used today. Automated endoscope reprocessors
provide the whole disinfection cycle which saves time and limits the
exposure of personnel to the chemical disinfectants (
Fig. 5.45).
After high-level disinfection, each internal channel must be flushed
with 70% alcohol and dried with forced air before it can be used on
another patient or stored. The alcohol flush enhances the drying process
and, thus, protects from recontamination.
Reprocessing of flexible endoscopes is challenging. The presence of
crevices, hinges, channels, valves, etc. makes it extremely difficult to
remove all bioburden without endangering the normal life cycle of the
endoscope. A (partly) disposable endoscope could overcome the problems
of reprocessing, but up to date, reusable designs still prevail.
5.7.2.6 Clinical Applications
Flexible gastroenterological endoscopy is used to examine the interior of
the gastrointestinal tract to detect (or to exclude) diseases and to classify
them. Upper GI endoscopy encompasses the exploration of the esophagus,
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Biomedical Engineering in Gastrointestinal Surgery
the stomach, and parts of the duodenum (descending duodenum)
(
Fig. 5.46). Typical indications are cancer screening or cancer staging
(classification of the severity), the detection of inflammation (e.g., reflux
esophagitis, gastritis), or the identification of sources of gastrointestinal
bleedin gs.
Gastroscopies are performed in high numbers all over the world. In
the United States, about 600,000 procedures are performed per year.
Figure 5.46 (A) Esophagus: A look into the middle part of the esophagus.
Anterograde view into the muscular hose. The wall is covered by squamous cell epithelium (schematic drawing of the position of the endoscope on the right).
(B) Cardia/Z-Line: The entrance into the stomach. Note: The squamous cell epithelium ends and the typical mucosa of the stomach begins (Z-line). (C) Cardia/Fundus/
Corpus: The endoscope is in retroflexion. A look from beneath onto the gastric cardia. (D) Antrum with pylorus: Anterograde view of the pylorus—a valve-like structure
between stomach and duodenum. (E) Bulbus duodeni: A look into the first part of
the duodenum (bulbus). All from MITI, M. Scholle.