Laparoscopic Imaging Systems

INTRODUCTION
It is well-known that laparoscopy is the consequence of
advances made in the field of medical engineering. Each
surgical specialty has different requirement of instruments.
Laparoscopy was initially criticized owing to the cost of
specialized instruments and possible complications due
to these sharp long instruments. Also, it necessitated
difficult hand-eye coordination. Gradually, the technique
gained recognition and respect from the medical fraternity
since it drastically reduced many of the complications of
the open procedure. Minimal access surgery (MAS) has
developed rapidly only after grand success of laparoscopic
cholecystectomy. Computer-aided designing of laparo-
scopic instruments is an important branch of medical
engineering. It is now possible to control the access through
microprocessor controlled laparoscopic instruments. New
procedures and instruments are innovated regularly which
make it important for the surgeon to be familiar with the
developments. Laparoscopy is a technologically-dependent
surgery and it is expected that every surgeon should have
reasonably good knowledge of these instruments.
LAPAROSCOPIC TROLLEY
The mobile laparoscopic video cart is equipped with locking
brakes and has four antistatic rollers. The trolley has a drawer
and three shelves (Fig. 1).
The upper shelves have a tilt adjustment and used for
supporting the video monitor unit. Included on the trolley is
anelectricalsupplyterminalstrip,mountedontherearofthe
secondshelf(fromthetop).Recently,ceilingmountedtrolleys
are launched by many companies which are ergonomically
better and consume less space in operation theater.
IMAGING SYSTEMS

■ Light source

■ Light cable

■ Telescope

■ Laparoscopic camera

■ Laparoscopic video monitor
The imaging system is a chain of equipment that is link
together in place perfectly and functioning well to produce
Fig. 1: Laparoscopic trolley.
Laparoscopic Imaging Systems
an excellent laparoscopic image. The break in this sequential
pass of links of the chain will be rendered our imaging system
impotent.
The classic imaging chain starts with a light source and
ends in the monitor, requiring seven pieces of equipment,
known as the magnificent seven—light source, fiberoptic
light cable, laparoscope, camera head, video signal
processor, video cable, and monitor (Fig. 2). This imaging
chain is often supported by a cast of VCRs, photo printers,
or digital capture devices. The surgeon and the operating
room team must work together to ensure optimal
equipment function through careful handling of the
equipmentintheoperatingroomandduringthesterilization
process. Yet, when the image is poor, many operating teams
become paralyzed, unable to function without the aid of
a medical engineer—“understanding can overcome any
situation, however, mysterious or insurmountable, it may
appear to be”
. Accordingly, understanding the (imaging)
video system will allow the operating surgeon to do the
basic troubleshooting for his or her system and not be totally
dependent on nursing or technical staff, especially at night
when experienced personnel may not be available. The
advent of integrated operating suites has not changed the
principles of this basic idea.
Prof. Dr. R. K. Mishra
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10 SECTION 1: Essentials of Laparoscopy
Fig. 2: The magnificent seven of the basic imaging chain.
Fig. 3: Spectrum of light.
Light Source
It is clear and easy to say that life, recently, is impossible
without light and simply no light, no laparoscopy. The light
source is the often-overlooked soldier of the video laparoscopic
system.
High-intensity light is created with bulbs of halogen
gas, xenon gas, or mercury vapor. The bulbs are available
in different wattages “150 W and 300 W” and should be
chosen based on the type of procedure being performed.
Because light is absorbed by blood, any procedure
in which bleeding is encountered may require more
light. We use the stronger light sources for all advanced
laparoscopy. Availability of light is a challenge in many
bariatric procedures where the abdominal cavity is
large.
A good laparoscopic light source should emit light as
much as possible near the natural sunlight.
Three types of light source are in use today:
1. Halogen light source
2. Xenon light source
3. Metal halide light source.
The output from the light sources is conducted to the
telescope by light cables that contain either glass fiber
bundles or special fluid.
The halogen light source is used in the medical field since
last 20 years, but the spectral temperature of these lights is
3,200 K which makes it too different and too low from natural
sunlight. The midday sunlight has approximately 5,600 K
color temperature. In practice, the yellow light of the halogen
bulb is compensated in the video camera system by white
balancing.
A more suitable light source for laparoscopic cameras
involves the creation of an electrical arc in a metal halide
system or in xenon. This electrical arc is produced in same
way as in flash of photographic camera.
Xenon has a more natural color spectrum and a smaller
spot size than halogen. The xenon light source emits a
spectral temperature of color of approximately 6,000 K on
average for a power of 300 W (Fig. 3).
Arc generated lamps have a spectral temperature that
gradually decreases with use and white balance is required
before each use. The bulb needs replacing after 250–500
hours of usage, depending on the type of lamp.
One of the main advantages of the laparoscopy is that of
obtaining a virtually microsurgical view compared to that
obtained by laparotomy. Quality of the image obtained very
much depends on the quantity of light available at each step
of optical and electronic system.
The interface of the laparoscopic team works with a
standard light source.
It is essential for the laparoscopic team, particularly the
surgeons, to know about all the switch and function of the
light source. All essential details of the equipment and all the
action required on the part can be found on the operating
manual of the product.
Many light sources record and display the hours of
service and alert the biomedical or medical engineer (or the
well-informed surgeon) when it is time to make a change.
When the lifetime rating of the bulb has been exceeded,
the subsequent performance of the light source becomes
unpredictable, often slowly dwindling until the surgeon just
cannot produce a well-lit scene, despite the fact that a bright
light seems to emanate from the laparoscope (Fig. 4).
A typical light source consists of:

■ A lamp (bulb)

■ A heat filter

■ A condensing lens

■ Manual or automatic intensity control circuit (shutter).
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CHAPTER 2: Laparoscopic Imaging Systems
Fig. 4: Xenon light source: Bulb-life display is shown. Fig. 5: New generation light source bulb.
Lamp (Bulb)
Lamp or bulb is the most important part of the light source.
When the bulb fails, the entire system is out of commission
until either the bulb is replaced or a new light is brought to
bear.
The quality of light depends on the lamp used. Several
modern types of light sources are currently available
(Fig. 5). These light sources mainly differ on the type of bulb
used.
Three types of lamp are used more recently:
1. Quartz halogen incandescent lamp
2. Xenon lamp
3. Metal halide vapor arc lamp
Halogen bulbs (150 W) or tungsten-halogen bulb: It is an
incandescent lamp with a transparent quartz bulb and a
compressed gas filling that includes a halogen. Quartz is
used instead of glass to permit higher temperatures, higher
currents, and therefore greater light output. The lamp gives
brilliant light. The halogen combines with the tungsten
evaporated from the hot filament to form a compound that is
attracted back to the filament, thus extending the filament’s
life. The halogen gas also prevents the evaporated tungsten
from condensing on the bulb and darkening it, an effect that
reduces the light output of ordinary incandescent lamps.
First used in the late 1960s in motion-picture production,
halogen lamps are now also used in automobile headlights,
underwater photography, and residential lighting.
Incandescent (to begin to glow): It is so hot to the point of
glowing or emitting intense light rays, as an incandescent
light bulb.
Quartz, one of the most common of all rock-forming
minerals and one of the most important constituents of the
earth’s crust. Chemically, it is silicon dioxide (SiO2). It occurs
in crystals of the hexagonal system, commonly having the
form of a six-sided prism terminating in a six-sided pyramid;
the crystals are often distorted and twins are common.
Quartz may be transparent, translucent, or opaque; it may
be colorless or colored.
The halogen lamp takes its name from the halogens
included in the gas within its tungsten-filament bulb, added
to prolong filament life and increase brightness.
Halogen:Anyoftheelementsofthehalogenfamily,consisting
of fluorine, chlorine, bromine, iodine, and astatine. They are
all monovalent and readily form negative ions.
Halogen bulbs provide highly efficient crisp white light
source with excellent color rendering. Electrodes in halogen
lamps are made of tungsten filament. This is the only metal
with a sufficiently high melting temperature and sufficient
vapor pressure at elevated temperatures. They use a halogen
gas that allows bulbs to burn (light) more intensely. Halogen
bulbs use low voltages and have an average life of 2,000
hours. The color temperature of halogen lamp is around
5,000–5,600 K. These lamps are economical and can be used
for laparoscopic surgery if low budget setup is required.
Xenon lamps (300 W):
Xenon (symbol Xe): A colorless, odorless, and highly
unreactive gaseous nonmetallic element found in minute
quantities in the atmosphere and extracted commercially
from liquefied air. Atomic number is 54. The radioactive
isotope 133
Xe, having a half-life of 5.3 days, is used for
diagnostic imaging in assessment of pulmonary function,
lung imaging, and cerebral blood flow studies.
Xenon lamps consist of a spherical or ellipsoidal
envelope made of quartz glass, which can withstand high
thermal loads and high internal pressure. For ultimate image
quality, only the highest-grade clear fused silica quartz is
used. It is typically doped, although not visible to the human
eye, to absorb harmful ultraviolet (UV) radiation generated
during operation. The color temperature of xenon lamp is
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about 6,000–6,400 K. The operating pressures are tens of
atmospheres at times, with surface temperatures exceeding
600°C.
The smaller, pointed electrode is called the cathode, which
supplies the current to the lamp and facilitates the emission
of electrons. To supply a sufficient amount of electrons,
the cathode material is doped with thorium. The optimum
operating temperature of the cathode tip is approximately
2,000°C. To obtain this precise operating temperature, the
cathode tip is pointed and in many cases, it has a groove on
the pointed tip to act as a heat choke. This heat choke causes
the tip to run at a higher temperature. This configuration of
the cathode tip allows for a very high concentration of light
from the cathode tip and a very stable arc.
The anode, the larger electrode, receives electrons
emitted by the cathode. Once the electrons penetrate the
anode face, the resulting energy is converted to heat, most
of which radiates away. The large, cylindrical shape of the
anode helps to keep the temperature low by radiating the
heat from the anode surface.
The advantage of xenon bulb is that it used two electrodes
(cathode and anode) and there is no filament as in halogen
bulb, so it has somewhat a fixed lifetime with an average of
1,500 hours.
The two most frequently used types of lamps are
halogen and xenon. The main difference between them is
in the colors obtained. The xenon lamp has a slightly bluish
tint. The light emitted by xenon lamp is more natural as
compared to halogen lamp. However, most of the cameras
at present analyze and compensate these variations by
means of automatic “equalization of whites” (2,100–
10,000 K), which allows the same image to be obtained with
both light sources.
A proper white balancing before start of the operation
is essential for obtaining a natural color. The white light is
composedofequalproportionofred,blue,andgreencolor.At
the time of white balancing, the camera sets its digital coding
for these primary colors to equal proportion, assuming that
the target is white. If at the time of white balancing, the
telescope is not seeing a perfectly white object, the setup of
the camera will be incorrect, and the color perception will
be poor.
The newer light source of xenon is defined as a cool light,
but practically it is not completely heat free and it should be
cared for ignition hazard.
Metal halide vapor arc lamp (250 W):
Halide: A halide is a binary compound, of which one part is
a halogen atom and the other part is an element or radical
that is less electronegative (or more electropositive) than
the halogen, to make a fluoride, chloride, bromide, iodide,
or astatide compound. Many salts are halides. All group 1
metals form halide compounds which are white solids at
room temperature.
A halide ion is a halogen atom bearing a negative charge.
The halide ions are fluoride (F–
), chloride (Cl–
), bromide
(Br–
), iodide (I–
), and astatide (At–
). Such ions are present in
all ionic halide salts.
Metal halides are used in high-intensity discharge lamps
called metal halide lamps such as those used in modern
street lights. These are more energy efficient than mercury-
vapor lamps and have much better color rendition than
orange high-pressure sodium lamps. Metal halide lamps are
also commonly used in green houses or in rainy climates to
supplement natural sunlight.
Examples of halide compounds are: sodium chloride
(NaCl), potassium chloride (KCl), potassium iodide (KI),
lithium chloride (LiCl), copper (II) chloride (CuCl2), silver
chloride (AgCl), and chlorine fluoride (ClF).
Metal halide lamps, a member of the high-intensity
discharge (HID) family of lamps, produce high light output
fortheirsize,makingthemacompact,powerful,andefficient
light source. By adding rare earth metal salts to the mercury-
vapor lamp, it improved luminous efficacy and light color is
obtained. Originally created in the late 1960s for industrial
use, metal halide lamps are now available in numerous
sizes and configurations for commercial and residential
applications (Figs. 6 to 8).
Like most HID lamps, metal halide lamps operate under
high pressure and temperature and require special fixtures
to operate safely.
In metal halide lamp, a mixture of compounds
(comprising mostly salts of rare earths and halides as well as
the mercury which provides the conduction path) is carefully
chosen to produce an output which approximates to “white”
light as perceived by the human eye (Fig. 9).
There are two types of metal halide lamp generally used.
They are iron iodide lamp and gallium iodide lamp. Iron
iodide is a broad emitter and enhances the spectral output
of the lamp in the 380 nm. Gallium iodide has the effect
of introducing spectral lines at 403 nm and 417 nm of the
electromagnetic spectrum (Fig. 10).
The intensity of the light delivered by any lamp also
depends on the power supply of the source. However,
increasing the power poses a real problem as it generates
more heat. At present, the improvements made to the
cameras means that it is possible to return to reasonable
power levels of 250 W. However, 400 W units are preferable
in order to obtain sufficient illumination of the abdomen
even when bleeding causes strong light absorption. It is
important to remember that a three-chip camera requires
more light than single-chip camera, so a 400 W light source
is recommended for three-chip camera.
Light-emitting diode light source: Light-emitting diode (LED)
technology is rapidly becoming the modern-day benchmark
for illumination. New range of LED light source units is
available offering high performance, quality, durability, and
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Fig. 6: A metal halide gas discharge lighting system provides illumination
for a college baseball game. Note the various colors of the lights as they
warm up.
Fig. 7: A low-bay light fixture using a high wattage metal halide lamp of
the type used in factories and warehouses.
Fig. 8: A linear/tubular metal halide lamp lit up at half power. Fig. 9: Metal halide bulb.
Fig. 10: Internal structure of metal halide tube. (1) ARC tube; (2) Tungsten electrodes; (3) Stem; (4) Ceramic heat shield; (5) Stainless steel frame;
(6) Spring supports; (7) Button getter and strip getters; (8) Ceramic spacer; (9) Nickel-plated brass base; (10) EN weld; (11) Ceramic insulator; (12) Deep
eyelet; (13) Resistor; (14) Bimetal switch; (15) Starter assembly; (16) HPS ARC tube; (17) End coat.
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Fig. 11: Light-emitting diode (LED) light source.
economy. The economy is due to the longevity of the lamp
units. For example, at an average of 30,000 hours operating
life, the LED units offer years of trouble-free performance
as well as the inherent cost saving of replacement bulbs. At
an average of 30,000 hours, the operating life of LED light
sources exceeds the standard life of high-performance light
sources. 250 workdays per year at 10 hours each equals an
operating life of approximately 10–12 years (Fig. 11). Most
incandescent and halogen bulbs are in the Kelvin range
(2,700–3,000 K). Fluorescent, metal halide, and LED bulbs
can be purchased with color temperature options from 2,700
to 6,500 K.
Why LED Light Source?
Light-emitting diodes offer definite advantages over
conventional lamps:

■ Purchase costs are quickly justified due to the long life
(30,000 hours) and minimal power consumption

■ Extremely economical

■ Ultra-low maintenance

■ Clear return on investment

■ High energy efficiency with 90% reduced power
consumption over conventional bulb types

■ Ready to go, instantly (full light intensity available as
soon as the unit is powered on)

■ Environmentally friendly.
Heat Filter
For 100% of energy consumed, a normal light source
(a light bulb) converts approximately 2% to light and 98% as
heat. This heat is mainly due to the infrared spectrum of light
and due to obstruction in the pathway of light. If infrared
travels through the light cable, the cable will become hot.
A heat filter is introduced to filter this infrared in fiberoptic
cable. A cool light source lowers this ratio by creating
more light, but does not reduce the heat produced to zero.
This implies a significant dissipation of heat, which increases
as the power rating increases. A cold light is light emitted at
low temperatures from a source that is not incandescent
such as fluorescence or phosphorescence. Incandescence is
the emission of light (visible electromagnetic radiation) from
a hot body as a result of its temperature.
The sources are protected against transmitting too much
heatatpresent.Theheatisessentiallydissipatedintransport,
along the cable, in the connection with the endoscope and
along the endoscope.
While it is remarkable how little heat is delivered to the
tip of the laparoscope, the effects are cumulative. A lighted
laparoscope or fiberoptic bundle in direct contact with paper
drapes or the patient’s skin will cause a burn after 20 or
30 seconds and must be avoided.
Some accidents have been reported due to burning
caused by the heat of the optics system. It is therefore
important to test the equipment, particularly if assemblies of
different brands are used.
Condensing Lens
The purpose of condensing lens is to converge the light
emitted by lamp to the area of light cable input. In most of
the light source, it is used for increasing the light intensity
per square cm of area.
Manual or Automatic Intensity
Control Circuit (Shutter)
Manual adjustment allows the light source to be adjusted
to a power level defined by the surgeon. In video cameras,
close-up viewing is hampered in too much light whereas
more distant view is too dark. To address this, the luminosity
of most of the current light sources is adjustable.
The advanced light source system is based on the
automatic intensity adjustment technology. The video
camera transforms the signal into an electronic signal.
This electronic signal is coded in order to be transported.
The coding dissociates the luminance and chrominance
of the image. The luminance is the quantity of light of the
signal (black and white) that dictates the quality of the final
image. When there is too much light for the image (when
the endoscope is near to the tissue), the luminance signal
of the oscilloscope increases. On the other hand, when the
luminosity is low (distant view or red surroundings), the
luminance is low and the electronic signal is much weaker.
A good quality luminance signal is calibrated to 1 mV.
Overexposed images make the electronic signal pass above
1 mV whereas underexposed images make the signal drop
below 1 mV. Light sources equipped with adjustment analyze
the luminance. If the signal is significantly higher than 1 mV,
they lower the power and bring the signal back within the
standards. Conversely, if the signal is too weak, they increase
their intensity.
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TABLE 1: Troubleshooting of light source.
Probable cause Remedy
• Loose connection at source or
scope
• Light is on“manual-minimum”
• Bulb is burned out
• Fiberoptics are damaged
• Automatic iris adjusting to bright
• Reflection from instrument
• Adjust connector
• Go to“automatic”
• Replace bulb
• Replace light cable
• Dim room lights
• Reposition instruments or
switch to“manual”
These systems are extremely valuable, permitting work
to be performed at different distances from the target in
good viewing conditions. However, the cameras currently
available are often equipped with a regulation system, which
is capable of automatic gain control in poor light condition
andthepurchaseofalightsourcewithadjustmentassociated
with a camera equipped with an adjustment system is a
double purchase that is unnecessary.
Troubleshootingoflaparoscopiclightsource:Troubleshooting
for inadequate lighting is shown in Table 1.
A laparoscopic surgeon should be technically well-
acknowledged of the principle of the instrument they are
using. The purchase of a costly instrument is not an answer
for achieving a good task, ability to handle them is equally
important.
Infrared light source: The new infrared LED light source
provides real-time endoscopic visibility and near-infrared
fluorescence imaging. This enables surgeon to perform
minimally invasive surgery (MIS) using standard endoscopic
visible light as well as visual assessment of vessels, blood
flow, related tissue perfusion, and biliary anatomy near-
infrared imaging. In addition, this infrared visualization
technology is very useful to transilluminate the ureters with
fiberoptic ureteric kit (IRIS U-kits) available (Fig. 12).
Fig. 12: Light-emitting diode (LED) light source with
infrared emission capability.
Fig. 13: Fiberoptic light cable.
Light Cable
Minimal access surgery depends on the artificial light
available in closed body cavity and before the discovery
of light source and light cable; mirrors were used to reflect
the light on to the subject where direct light access was not
possible.
In 1954, a major breakthrough in technology occurred in
the development of fiberoptic cables (Fig. 13). The principle
of fiberoptic cable was based on the total internal reflection
of light. Light can be conducted along a curved glass rod due
to multiple total internal reflections. Light would enter at one
end of the fiber and emerge at the other end after numerous
internal reflections with virtually all of its intensity.
Total Internal Reflection
An effect that combines both refraction and reflection is
total internal reflection (Fig. 14). Consider light coming
from a dense medium like water into a less dense medium
like air. When the light coming from the water strikes the
surface, part will be reflected and part will be refracted.
Measured with respect to the normal line perpendicular to
the surface, the reflected light comes off at an angle equal
to that at which it is entered while that for the refracted
light is larger than the incident angle. In fact, the greater
the incident angle, the more the refracted light bends away
from the normal. Thus, increasing the angle of incidence
from path “1” to “2” will eventually reach a point where
the refracted angle is 90o
, at which point the light appears
to emerge along the surface between the water and air. If
the angle of incidence is increased further, the refracted
light cannot leave the water. It gets completely reflected.
The interesting thing about total internal reflection is that
it is really total. That is 100% of the light gets reflected back
into the more dense medium, as long as the angle at which it
is incident to the surface is large enough.
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Fig. 15: Fiberoptic cable, total internal reflection.
Fig. 14: Refraction of light from water into air.
Fiberoptics uses this property of light to keep light beams
focused without significant loss (Fig. 15).
The light enters the glass cable and as long as the bending
is not too sudden, it will be totally internally reflected when
it hits the sides and thus is guided along the cable. This is
used in telephone and TV cables to carry the signals. Light
as an information carrier is much faster and more efficient
than electrons in an electric current. Also, since light rays do
not interact with each other (whereas electrons interact via
their electric charge), it is possible to pack a large number of
different light signals into the same fiberoptics cable without
distortion. You are probably most familiar with fiberoptics
cables in novelty items consisting of thin, multicolored
strands of glass which carry light beams. Nowadays, there
are two types of light cable available:
1. Fiberoptic cable
2. Liquid crystal gel cable
Fiberoptic Cable
Fiberoptic is the science or technology of light transmission
through (a bundle of optical fibers) a very fine, flexible glass
or plastic fibers.
Fiberoptic cables are made up of a bundle of optical
fiber glass threads waged at both ends. The fiber size used
is usually 20–150 µ in diameter. A good fiberoptic cable will
transmit all the spectrum of light without loss (Fig. 16). They
have a very high quality of optical transmission, but are
fragile.
The light inside these fibers travels on the principle of
total internal reflection without losing much of its intensity.
The multimode fiber maintains the intensity of light and the
light can be passed in a curved path of light cable (Fig. 17).
As the light cables are used progressively, some optical
fibers break (Fig. 18). The loss of optical fibers may be seen
when one end of the cable is viewed in daylight. The broken
fibers are seen as black spots. To avoid the breakage of these
fibers, the curvature radius of light cable should be respected
and in any circumstances it should not be <15 cm in radius.
If the heat filter or cooling system of light source does
not work properly, the fibers of these light cables are burnt
(melt) and it will decrease the intensity of light dramatically
(Fig. 19). If poor quality fibers are used, it might burn just
within a few months of use.
Liquid Crystal Gel Cable
These cables are made up of a sheath that is filled with a clear
optical gel (liquid crystal).
Crystal (a clear, transparent mineral or glass resembling
ice)isapieceofsolidsubstance,suchasquartz,witharegular
shape in which plane faces intersect at definite angles, due to
the regular internal structure of its atoms, ions, or molecules.
Within a crystal, many identical paralleled-piped unit cells,
each containing a group of atoms, are packed together to
fill all space (see illustration). In scientific nomenclature,
the term crystal is usually short for single crystal, a single
periodicarrangementofatoms.Mostgemsaresinglecrystals.
However, many materials are polycrystalline, consisting
of many small grains, each of which is a single crystal. For
example, most metals are polycrystalline (Fig. 20).
Liquidcrystal:Substancethatflowslikealiquid,butmaintains
some of the ordered structure characteristic of a crystal.
Some organic substances do not melt directly when heated,
but instead turn from a crystalline solid to a liquid crystalline
state. When heated further, a true liquid is formed. Liquid
crystals have unique properties. The structures are easily
affected by changes in mechanical stress, electromagnetic
fields, temperature, and chemical environment.
Liquid crystal gel cables are capable of transmitting up
to 30% more light than optic fibers. Due to lighter and better
color temperature transmission, this cable is recommended
in those circumstances, where documentation (movie,
photography, or TV) is performed.
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Fig. 18: Broken fibers showing significant loss of light.
Fig. 19: Burnt fiber causes significant reduction in intensity of light.
Fig. 20: Structure of a simple crystal.
optical fiber cables, which are as fragile as the gel cables but
their flexibility makes them much easier to maintain.
Attachment of the Light Cable to the Light Source
Conventional attachment has a right angle connection for
light source and camera. Recently, new attachment for light
cable is available known as display control interface (DCI)
(Fig. 21). The benefit of this is that it maintains upright
orientation regardless of angle of viewing, using autorotation
system. It also provides single-handed control of the entire
endoscope camera system.
Maintenance of Light Cable
The following points should be followed for the maintenance
of light cable:

■ Handle them carefully

■ Avoid twisting them
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Fig. 21: Display control interface (DCI) attachment of light cable. Fig. 22: Negligence with light cable can result in burn.

■ After the operation has been completed, the cable should
preferably be first disconnected from the endoscope and
then disconnected from the light source. In fact, most of
the sources currently available have a plug for holding
the cable until it cools down.

■ The end of the crystal of cable should be periodi-
cally cleaned with a cotton swab moistened with
alcohol.

■ The outer plastic covering of the cable should be cleaned
with a mild cleaning agent or disinfectant.

■ Distal end of fiberoptic cable should never be placed on
or under drapes or next to the patient, when connected
to an illuminated light source. The heat generated from
the intensity of light may cause burns to the patient or
ignite the drapes (Fig. 22).

■ The intensity of light source is so high that there is chance
of retinal damage if the light will fall directly on eye. Never
try to look directly on light source when it is lighted.
Telescope
There are two types of telescope: (1) rigid and (2) flexible.
The rigid laparoscopic and thoracoscopic telescopes
come in a variety of shapes and sizes and offering several
different angles of view. The standard laparoscope consists
of a metal shaft between 24 and 33 cm in length.
There are three important structural differences in telescope
available in the market:
1. Number of the rod lens: From 6 to 18 rod lens system
telescopes
2. Angle of view: Between 0 and 120° telescopes
3. Diameter: 1.5–15 mm of telescopes.
Angle of View
Telescopes offer either a straight-on view with the 0° or can
be angled at 25–30° or 45–50°. The 30° telescope provides a
Fig. 23: The 30° telescope provides a total field of view of 152° compared
with the 0° telescope, which provides a field of view of only 76°.
total field of view of 152° compared with the 0° telescope,
which only provides a field of view of 76° (Fig. 23). The 30°
forward oblique angle permits far greater latitude for viewing
underlying areas under difficult anatomical conditions
(Fig. 24).
Diameter
The most commonly used telescope has a diameter of 10 mm
and provides the greatest light and visual acuity. The next
most commonly used telescope is the 5 mm laparoscope,
which can be placed through one of the working ports for an
alternative view. Smaller-diameter laparoscopes, down to a
1.1-mm scope, are available and are used mostly in children.
They are not used commonly in adult patients because of
an inability to direct enough light into the larger abdominal
cavity. Laparoscopes as small as 1 mm have been produced
for diagnostic use. The field of view and picture brightness
are dramatic improvements over early designs. Mini or
micro 2 mm laparoscopy is reported for diagnostic and even
advanced procedures.
One of the problems with working with these smaller
laparoscopes (particularly those <3.4 mm) is that they tend
to bend easily, leading to potential damage during surgery.
Full screen 5 mm laparoscopes with images comparable
to many 10 mm systems are now available.
PDFelement

Fig. 24: Angle of laparoscope. Fig. 25: Different types of laparoscope.
Fig. 26: Inside view of laparoscope.
Lens System
There are two lens system designs used with the
laparoscopy—(1) the conventional thin lens system and
(2) the Hopkins rod-lens system design. The thin lens
system, which uses a series of objective lenses to transport
the image down the laparoscope, is used less commonly.
The Hopkins rod-lens system containing a series of quartz
rod lenses that carry the image through the length of the
scope to the eyepiece. Rigid rod lens system provides good
resolution and better depth perception (Fig. 25). The
Hopkins rod-lens system uses more glass than air, so it
has improved light transmission (Fig. 26). Normally used
telescope is the Hopkins Forward-Oblique Telescope (30°).
Its diameter is 10 mm, length is 33 cm, and is autoclavable.
At the distal end, it is a front lens complex [inverting real-
image lens system (IRILS)] which creates an inverted and
real image of the subject. A number of IRILS transport the
image to the eyepiece containing a magnifying lens. In the
Hopkins rod-lens system, light is transmitted through glass
columns and refracted through intervening air lenses. The
camera is attached to the eyepiece of the laparoscope for
processing.
Digital laparoscopes, in which the laparoscope and
camera head are a single unit with the imaging sensor at
the end of the laparoscope, have been available since
the early 1990s. This (chip on stick technology) has been
introduced in which charge-coupled device (CCD) chip will
be at the tip inside the abdominal cavity. One of the popular
brands of digital laparoscope is Olympus ENDOEYE. The
ENDOEYE comes with the fog-free feature, providing clear
views throughout the procedure. The advanced multi-CCD
chip on the tip technology enables bright, clear images and
narrow band imaging (NBI) further enhances visualization
of vessels and other tissues on the mucosal surface. The
flexible tip can articulate in all directions up to 100° and
the focus-free optical design provides greater depth of field,
eliminating the need for manual focusing (Fig. 27).
Telescope Fiber Bundle
The telescope also contains parallel optical fibers bundle
that transmits light into the abdomen from the light source
via a light cable attached to the side of the telescope. The
fiber bundle in the laparoscope and the fiberoptic light
cable must be in excellent working order, so as to achieve
an optimal well-lighted picture. The fiber bundle located
along a tract on the periphery of the telescope and occupies
less than half of the circumference of the telescope. It is exit
at the inner tip of the telescope that is corresponding to the
attachment of the light cable to the side of the telescope.
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Fig. 28: Stereoscope for three-dimensional (3D) laparoscopic view.
and tissues, creating an augmented reality environment that
has been proven to improve the performance of the surgeon.
These new 3D technologies, also used to create completely
virtual scenes for surgical preparation and training, are
rendered from volumetric data that are obtained from
preoperative scans (Fig. 28).
The Olympus VISERA 3D platforms (Olympus, Shinjuku,
Tokyo, Japan), for instance, include stereovideoscopes that
can bend their tip of 100° in four directions and providing 3D
videosin4Kresolutionandofferingflexibilityforapplications
in laparoscopy and endoscopy. Another example is the
3D-Eye-Flex, developed by Nishiyama et al., an endoscopic
video system, that offers a wide angle of view for minimally
invasive neurosurgery. This type of technology is already
commercially available and has undergone clinical trials,
yielding improved performance, shorter learning curve, and
greater accuracy and precision (Fig. 29).
Laparoscopic Camera
First medical camera was introduced by Circon Corporation
in 1972. Laparoscopic camera is one of the very important
instruments and should be of good quality (Fig. 30).
Laparoscopic camera available is either of single chip or
three chips. We all know that there are three primary colors
[red, green, and blue (RGB)]. All the colors are mixture of
these three primary colors in different proportion.
The CCD chip or complementary metal oxide
semiconductor(CMOS)isanelectronicmemorythatrecords
the intensity of light as a variable charge. Widely used in
still cameras, camcorders, and scanners to capture images,
CCDs are analog devices. Their charges equate to shades of
light for monochrome images or shades of RGB when used
with color filters. Three-chip camera uses three CCDs, one
for each of the RGB colors (Figs. 31A and B).
Three-dimensional Stereoscope
One of the main problems associated with video-assisted
MIS is the loss of stereopsis, meaning the perception of
depth and three-dimensionality. This occurs when a three-
dimensional (3D) image is projected on a two-dimensional
(2D) screen and is often the cause of impeded hand-eye
coordination and erroneous movements of the tools.
Modern laparoscopic stereoscope with dual cameras can
provide 3D images in ultra-high definition (UHD) resolution
and offer a binocular stereoscopic vision of the operative
field comparable to open surgery, making up for the loss of
stereovision and representing a definite improvement. There
are flexible 3D videoscopes also available which allow the
surgeon to reach hidden targets even through tortuous paths
and have permitted the emergence of novel techniques
that exploit the body’s natural openings. In addition, video
images can be enhanced with virtual models of structures
Fig. 27: Chip on stick technology.
PDFelement

Fig. 30: Laparoscopic camera.
Fig. 29: Olympus VISERA 3D platform.
Why Coupled?
The “coupled” in the name is because the CCD is comprised
of an array of imaging pixels and a matching array of storage
pixels that are coupled together. After the imaging array is
exposed to light, its charges are quickly transferred to the
storage array. While the imaging CCDs are being exposed
to the next picture, the storage CCDs from the last picture
are being read out a row at a time to the analog-to-digital
(A/D) converters that transform the charges into binary data
(0/1) to be processed (Fig. 32). CCD and CMOS are both
image sensors found in digital laparoscopic cameras. They
are what is responsible for converting light into electronic
signals. The first digital cameras used CCD to turn images
from analog light signals into digital pixels. They are made
through a special manufacturing process that allows the
conversion to take place in the chip without distortion. This
creates high quality sensors that produce excellent images.
But, because they require special manufacturing, they are
more expensive than their newer CMOS counterparts.
CMOS chips use transistors at each pixel to move the charge
through traditional wires. This offers flexibility because each
pixel is treated individually. Traditional manufacturing
processes are used to make CMOS. It is the same as creating
microchips. Because they are easier to produce, CMOS
sensors are cheaper than CCD sensors. Because CMOS
technology came after CCD sensors and are cheaper to
manufacture,CMOSsensorsarethereasonthatlaparoscopic
cameras have dropped in price.
The biggest difference is that CCD sensors create high
quality images with low noise. CMOS images tend to be
higher in noise. CCD sensors are more sensitive to light.
CMOS sensors need more light to create a low noise image
at proper exposure. This does not mean that CMOS sensors
are completely inferior to CCD. CCD has been around for
a lot longer in digital cameras and the technology is more
advanced. CMOS sensors are catching up and will soon
match CCD in terms of resolution and overall quality. They
can be manufactured on any standard silicon production
line and are much more inexpensive when compared to
CCD sensors. Eventually economics will someday make
every camera CMOS when the final advances in quality are
made. In fact, CMOS sensors are already superior to CCD
sensors in terms of power consumption.
The camera system has two components: (1) the head of
the camera (Fig. 33), which is attached to the ocular of the
telescope and (2) the controller, which is usually located on
the trolley along with the monitor.
Within the head of camera is an objective zoom lens that
focuses the image of the object on the chip and a CCD chip
that “sees” an image taken by telescope (Fig. 34). All modern
miniature cameras used in minimal access surgery are based
on the CCD chip. The CCD then converts optical image into
an electrical signal that is sent through the camera cable
to camera control unit (CCU). The chip has light-sensitive
photoreceptors that generate pixels by transforming the
incoming photons into electronic charges. The electronic
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23
A B
Figs. 31A and B: In a camera, CCD or CMOS takes the place of film. They are exposed to light, recording the intensities, or shades of light as variable
charges. In the digital camera above, the variable analog charges in the CCD or CMOS are converted to binary data (0/1) by analog-to-digital converter
(ADC) chip.
(CCD: charge-coupled device; CMOS: complementary metal oxide semiconductor; DSP: digital single processing)
Fig. 32: The storage CCDs are either a separate array (frame transfer)
or individual photosites (interline transfer) coupled to each imaging
photosite. The charges can be transferred faster with the interline
method because each storage component is closer to its imaging
counterpart.
(A/D: analog-to-digital; CCDs: charged-coupled devices)
Fig. 33: Head of camera 4K.
charges are then transferred from the pixels into a storage
element on the chip. A subsequent scanning at defined time
intervals results in a black and white image with gray tones.
Pixel: PIX (picture) + EL (element), picture element is the
smallest element of a light-sensitive device, such as cameras
thatuseCCDs.Itisthesmallestresolvedunitofa videoimage
that has specific luminescence and color. Its proportions
are determined by the number of lines making up the
scanning raster (the pattern of dots that form the image) and
the resolution along each line. In the most common form
of computer graphics and the CCDs, the thousands of tiny
pixels that make up an individual image are projected onto
a display screen as illuminated dots that from a distance
appear as a continuous image. An electron beam creates the
grid of pixels by tracing each horizontal line from left to right,
one pixel at a time, from the top line to the bottom line.
The number of pixels determines the resolution.
Screen resolution is rated by the number of horizontal and
vertical pixels; for example, 1,024 × 768 means 1,024 pixels
are displayed in each row and there are 768 rows (lines).
PDFelement

Fig. 34: Charge-coupled device (CCD) camera.
Likewise, bitmapped images are sized in pixels: a 350 × 250
image has 350 pixels across and 250 pixels down. You have
probably already noticed the jump from predigital “standard
definition” television up to “HD” and “full HD” services that
are now available on digital TV, online streaming, and Blu-
Ray disks. Compared to earlier standards, this HD footage
is detailed, crisp, and it even looks good when viewed on a
large TV. But even the best quality, “1,080 pixels” HD footage
is only across 1,920 pixels. Recently, 4K or UHD laparoscopic
cameras are available. 4K is significantly more detailed, since
it has twice as many pixels horizontally and four times as
many pixels in total.
Pixels and subpixels: In monochrome systems, the pixel
is the smallest addressable unit. With color systems,
each pixel contains RGB subpixels and the subpixel is
the smallest addressable unit for the screen’s electronic
circuits. On a display screen, pixels are either phosphorus
or liquid crystal elements. For monochrome, the element
is either energized fully or not. For grayscale, the pixel is
energized with different intensities, creating arrange from
light to dark. For color displays, the RGB subpixels are each
energized to a particular intensity and the combination of
the three color intensities creates the perceived color to the
eye. The average chip contains 250,000–380,000 pixels, but
4K video is poised to become the new benchmark for both
recording and watching laparoscopic video and it brings a
whole host of benefits, right away.
Cameras are classified according to the number of chips.
These differ among other things, in the way they relay color
information to the monitor. Color separation is used to create
a colored video image from the original black and white. In
single-chip cameras, color separation is achieved by adding
a stripe filter that covers the whole chip. Each stripe accepts
one of the complementary colors (magenta, green, cyan, or
yellow) and each pixel is assigned to one stripe.
In single-chip camera, these three primary colors are
sensed by single chip. In three-chip camera, there are
three CCD chips for separate capture and processing of
three primary colors (RGB). In three-chip cameras, color
separation is achieved with a prism system that overlies
the chips. Each chip receives only one of the three primary
colors (RGB). This system gives a higher resolution and
better image quality because the pixel number is three times
greater.
The video information, color, and light are scanned
at a rate of 525 lines per frame and 30 frames per second.
Picture resolution determines the clarity and detail of
the video image. Higher the resolution, the better will be
quality of image. The resolution of picture is ascertained by
the number of distinct vertical line that can be seen in the
picture. The higher the resolution numbers, the sharper and
cleaner image will form. The CCU of camera is connected
with monitor and monitor converts the electrical image back
to the original optical image.
These three-chip camera has unprecedented color
reproduction and highest degree of fidelity. Three-chip
cameras have high horizontal image resolution of >750 lines.
Chip on Stick Technology
Currently, chip on stick technology has been introduced
in which CCD will be at the tip inside the abdominal cavity.
It is proved that the resolution of picture will be >250K pixels
(Fig. 27).
Focusing of Laparoscopic Camera
Laparoscopic camera needs to be focused before inserting
inside the abdominal cavity. At the time of focusing, it should
be placed at a distance of approximately 10 cm away from
the target for the 10 mm telescope, 5 cm for 5 mm telescope,
and 4 cm for 4 mm telescope, with an average distance of
approximately 5 mm for all telescopes. This distance is
optimum for focusing because at the time of laparoscopic
surgery, most of the time we keep the telescope at this
distance.
White Balancing of Camera
White balancing should be performed before inserting
camera inside the abdominal cavity. White balancing
is required to remove added impurities of light which
unknowingly we add. During white balancing, digital
laparoscopic camera will added counter color to neutralize
our added impurity. White balancing is necessary every
time before start of surgery because every time there is some
added impurities of color due to following variables:

■ Difference in voltage

■ Differences in color temperature of light sources

■ Different cleaning material used to clean the tip of
telescope which can stain the tip

■ Scratches, wear, and tear of the telescopes eyepiece,
object piece, and CCD of camera.
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White balancing is done by keeping any white object in
front of telescope attached with camera that senses white
object as reference. It adjusts its primary color (RGB) to
make a pure natural white color.
Laparoscopic Video Monitor
Surgical monitors are slightly different from the TV which we
watch at home (Fig. 35). Monitor lasts long so a surgeon gets
high-end product with at least 600 lines resolution. The size
of the screen varies generally from 8 to 29 inches. The closure
the laparoscopic surgeon is to the monitor, the smaller the
monitor should be to get better picture. The basic principle
of image reproduction is horizontal beam scanning on
the face of the picture tube. This plate is coated internally
with a fluorescent substance containing phosphorus. This
generates electrons when struck by beams from the electron
gun. As the beam sweeps horizontally and back, it covers all
the picture elements before reaching its original position.
This occurs repetitively and rapidly. This method is called
horizontal linear scanning. Each picture frame consists of
several such lines depending on the type of system used.
Distanceofmonitorfromtheeyeofthesurgeonshouldbefive
times to the diagonal length of monitor screen. It means that
if the monitor is 21 inch it should be kept 105 inch away from
the eye of the surgeon. Nowadays, 4K laparoscopic monitor
is preferred. It is also known as an ultra-high definition or
UHD monitor, is one that supports 4K resolution. This brings
up another common question: what is 4K resolution? The
answer is simple. Standard HD or 1,080 pixels (as found on
Blu-Ray disks and HD televisions) is made up of a picture
that is 1,920 pixels in width and 1,080 pixels in height. In
total, this results in a picture with more than two million
pixels. The width of a picture that has 4K resolution contains
almost 4,000 pixels (3,840 pixels to be precise—twice that of
1,080 pixels). With 2,160 pixels along the vertical side, the
total number of pixels on a 4K monitor is four times that of a
traditional HD monitor.
Endoscopic Vision (Video) Technology Evolution
In the past, endoscopic procedures were done without the
aid of monitors. The operator visualized the interiors of
the patient directly through the eyepiece of the scope. This
method was associated with many difficulties. He was the
onlypersonwhocouldobservetheprocedureleadingtopoor
coordination with other members of the team. As a result,
extensive and difficult procedures could not be performed.
The magnification was very poor. Surgeons had to face
problems with posture leading to discomfort and strain as
his eye was always glued to the eyepiece. He had difficulties
in orientation due to visualizing with only one eye.
As better methods of communication developed, the
introduction of television brought about a significant
impact. A good magnification of the image was reproduced.
All members of the team could visualize the procedure.
Surgeons could operate more comfortably. Complex
procedures began to be undertaken and were even recorded.
Soulas in France first used television for endoscopic
procedures in 1956. He demonstrated the first televised
bronchoscopy. A rigid bronchoscope was attached to a black
and white camera that weighed about 100 lbs.
In 1959, a laparoscopic procedure was demonstrated
usingaclosedcircuittelevisionprogramusingthe“Fourestier
method”
. This method was developed by transmitting an
intense beam of light along a quartz rod from the proximal to
distal ends of the laparoscope.
The first miniature endoscopic black and white
television camera was developed in Australia in 1960
(Fig. 36). It weighed 350 g, was 45 mm wide, and 120 mm
long. Because of its small dimensions, it could be attached
to the eyepiece.
Fig. 35: Laparoscopic 4K monitor. Fig. 36: Endoscopic camera.
PDFelement

TABLE 2: Different types of monitor systems.
System PAL SECAM NTSC
Number of lines 625 625 525
Visible lines (maximum) 575 575 486
Field frequency cycles per second (cps) 50 50 60
Frames per second 25 25 30
(NTSC: National Television System Committee; PAL: Phase Alternating
Line; SECAM: Sequential Color and Memory)
TELEVISION SYSTEMS
The existing television systems in use differ according to
the country. The USA uses the National Television System
Committee(NTSC)system.InEuropeancountries,thePhase
Alternating Line (PAL) system is in use. There is also a French
system called Sequential Color and Memory (SECAM). The
broadcasting standards for each are summarized in Table 2.
The final image depends upon the number of lines of
resolution, scanning lines, pixels, and dot pitch. The number
of black and white lines a system can differentiate gives the
lines of resolution. These can be horizontal and vertical.
Horizontal resolution is the number of vertical lines that can
be seen and vice versa. Pixels denote the picture elements
and they are responsible for picture resolution. The more
number of pixels is, the better the resolution. They are
representedonthecamerachipbyanindividualphotodiode.
The restricting factor of information on a scan line is the “dot
pitch” that represents phosphorus element size.
The NTSC system has certain drawbacks. Not all the lines
of resolution are used. The maximum number of lines visible
is reduced by 40. Improving the resolution of the camera will
not improve monitor resolution. This is due to a fixed vertical
resolution. In addition to these problems, if the phase angle
is disturbed even a little, it produces unwanted hues.
The PAL system is superior in certain aspects. It can
overcome this problem by producing alternations over the
axis of modulation of the color signed by line. This system
also deals with problems of flickering. It involves a process
called “interlacing” where odd and even lines in a field are
scanned alternatively.
The SECAM system is similar to PAL in these aspects,
except that the signals are transmitted in sequence.
Formation of the Color Image
Another important aspect one has to keep in mind is the
formation of the color image. This is done by superimposing
the data for color on the existing black and white picture.
The black and white signal is monochromatic signal and
combines with the composite color signal. This gives the
final color signal.
Luminance (brightness) is delivered by the black and
white signal. Chrominance (color) is delivered by the color
signal. It is called composite as it contains the three primary
color information (RGB). A system that combines luminance
and chrominance into one signal is called a compound
system.
Color values can be problematic as they can go out
of phase. This is due to their high sensitivity. Applying a
reference mark for the signal on the scanning line is called
as color burst and it can prevent this sensitivity. The color
on a monitor can be calibrated. This can be done manually
by using the standard color bars of NTSC or by using other
methods like “blue gun”
. New monitors do not require this,
as calibration can be done automatically.
Monitor Connecting Cables
Images cannot be visualized on the monitor unless they
are wired. Monitor cables are of three types. The RGB cable
has three wires, one for each primary color. The Y/C cable
has two wires, one for the luminance (Y) and one for the
chrominance (C) component. The composite cable consists
of one pair of wires. An important factor to realize is that
no matter what type of cable is used, whether it has better
bandwidth or other advantages, the final resolution depends
upon the monitor used. For HD and UHD system, we should
always use Digital Visual Interface (DVI) or HDMI cable.
DVI, which stands for Digital Visual Interface, is the older
of the two and arguably on its way out. Functionally, HDMI
and DVI cords are basically identical. The DVI video signal
is basically the same as HDMI, just without the audio. In
laparoscopic surgery, we do not use audio so DVI is used
more.
Frames of Reference in Vision
We face many problems with monitors in regard to minimal
access surgery. But before dealing with them, a mention of
the frames of reference in vision would be apt. NJ Wade’s
paper on “Frames of Reference in Vision” mentions various
frames namely retinocentric, egocentric, geocentric, and
pattern centric. He applies the set of minimal access surgery
and finds a dissociation of pattern centric motion (seen
on the monitor) and the area of manipulation. Any visual
motor task requires a match between the coordinate systems
operating in both vision and motor control. Knowledge of
these frames can alter our perspective of the way things
happen in minimal access surgery with respect to vision.
Drawbacks with the Monitor
After routine use, we encounter many drawbacks with
the monitor. Only a 2D image can be seen on present
day monitors. The operative field is represented only by
monocular depth cues. Monitor positioning is such that the
visual motor axis is disrupted. The monitor distance from
the surgeon is also quite far. As a result, the efficiency of the
surgeon decreases.
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Apart from pictorial depth cues, the picture can be
further disturbed by anticues. These may originate from
the monitor. Glaring effect due to reflection is one of these
important anticues.
Imaging Technical Terms
Resolution means the degree of sharpness of a displayed or
printed image; simply, the ability of a television or film image
to reproduce fine detail.
Resolution is defined as (pixels per inch) the maximum
number of pixels that can be displayed on a screen monitor,
expressed as (number of horizontal pixels) × (number of
vertical pixels), i.e., 1,024 × 768 pixels. The ratio of horizontal
to vertical resolution is usually 4:3, the same as that of
conventional television sets.
For a monitor, a screen resolution of 1,920 × 1,200 means
1,920 pixels horizontally across each of 1,200 lines, which
run vertically from top to bottom.
For printers and scanners, resolution is expressed as the
number of dots per linear inch [printed dots per inch (dpi)].
300 dpi means 300 × 300 or 90,000 dots per square inch.
Laser printers and plotters have resolutions from 300 to 1,200
dpi and more whereas most display screens provide <100 dpi
(Figs. 37 and 38).
Gain controls the brightness of the image under
conditions of low light by recruiting pixels to increase signal
strength. Clearly, this step results in some loss of image
resolution. This increases light but results in a grainy picture
with poorer resolution. It also may create a loss of color
accuracy owing to amplification of the noise-to-signal ratio.
The gain should be off at the beginning of a routine
procedure (not needed in routine situations). There are two
good reasons for this. First, inadequate light at the beginning
of the procedure is an indication that a piece of equipment
is malfunctioning, a situation that should be rectified before
getting too involved with the procedure. Second, the use of
“gain” comes at the expense of picture resolution, resulting
in a somewhat grainy image on the monitor while turning
the brightness knob to maximum produces a very washed-
out picture. A good general rule of thumb to follow is to
look in the right upper quadrant and visualize the space
over the liver. The entire dome of the liver and right lateral
diaphragm should be well-lit and easily seen. If not, then the
lighting system should be evaluated and optimized prior to
beginning the dissection (Figs. 39A and B).
Fig. 38: Wide and larger screen resolution (16:9) aspect ratio, i.e., the width is more than the height.
(QWXGA: Quad Wide Extended Graphics Array; WQSXGA: Wide Quad Super Extended Graphics Array; WQUXGA: Wide Quad Ultra Extended Graphics
Array; WSXGA: Wide Super Extended Graphics Array; WUXGA: Wide Ultra Extended Graphics Array; WXGA: Wide Extended Graphics Array)
Fig. 37: Standard screen resolution (4:3) aspect ratio, i.e., the height is
somewhat approximates to the width.
(QXGA: Quad Extended Graphics Array; SVGA: Super Video Graphics
Array; SXGA: Super Extended Graphics Array; UXGA: Ultra Extended
Graphics Array; VGA: Video Graphics Array)
PDFelement

A B
Figs. 39A and B: Gallbladder lighting scene. (A) Poorly lit right upper quadrant. The diaphragm is barely visible;
(B) Same patient after faulty light cable is replaced.
Fig. 40: Changes in the amount of contrast in a photo, left side of the
image has low contrast and the right side of the image has higher
contrast.
Contrast: The extent to which adjacent areas of an optical
image, on a monitor screen, differ in brightness. It is the
difference in visual properties that makes an object (or its
representation in an image) distinguishable from other
objects and the background. In visual perception of the real
world, contrast is determined by the difference in the color
and brightness of the object and other objects within the
same field of view. Because the human visual system is more
sensitive to contrast than absolute luminescence, we can
perceive the world similarly regardless of the huge changes
in illumination over the day or from place-to-place (Fig. 40).
Luminescence is a general term applied to all forms
of cool light, i.e., light emitted by sources other than a hot,
incandescent body. It is a process by which an excited
material emits light in a process not caused solely by a rise
in temperature. The excitation is usually achieved with
ultraviolet radiation, X-rays, electrons, alpha particles,
electrical fields, or chemical energy. The color or wavelength
of the light emitted is determined by the material while
the intensity depends on both the material and the input
energy. Examples of luminescence include light emissions
from neon lamps, luminescent watch dials, television and
computer screens, fluorescent lamps, and fireflies.
Modulation Transfer Function
The endoscopes transmit resolution and contrast to the
monitor. The efficacy by which this occurs determines the
more delicate aspects of the image. Resolution and contrast
can be measured on an especially designed optical bench
and expressed as modulation transfer function (MTF). If
there is excessive glare in the picture, then contrast and
resolution decrease. Distortions of the image can occur and
if these lines seem to curve outward they are called barrel
distortion. Field curvature occurs when there is improper
focus of the center from other parts. Astigmatism can occur
when some lines of different orientation are present in focus
and others are not.
Temporal Aliasing
When a moving object is shown on a monitor, unless the
speed with which it is moving is similar to the refresh rate,
then jerky movements will occur. This is called temporal
aliasing. This can be prevented by the use of filters or by
performing slow movements. Fatigue and headache can
occur due to disturbance of saccadic eye movements. These
are rapid eye movements used to visualize the borders of a
field.
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Gaze-down Position
When a surgeon has to constantly look in a different
direction and operate in another, his efficiency to perform
declines. The job becomes even more difficult if the
monitor is positioned at a further distance, giving rise to
spatial disorientation. A surgeon can perform optimally if
he can look and operate in the same direction as in open
surgery. This can also be called the gaze-down position.
THREE-DIMENSIONAL VISION
One of the major limitations of minimal access surgery is the
loss of depth perception. The surgeon works with an artificial
2D video pictures available on the monitor. There is a need
to develop some mechanism to improve depth perception
or stereoscopic vision. Stereoscopic vision is needed for
precise and fast complex manipulations because perception
of space and depth are necessary in surgery.
Stereopsis (Three-dimensional Perception)
Stereopsis refers to perception of 3D shape from any
source of depth information. Unlike horses, humans have
two eyes located side-by-side in the front of their heads.
Due to the close side-by-side positioning, each eye takes
a view of the same area from a slightly different angle
(Fig. 41).
The two eyes have different views of the visual world
and these different views setup disparities that give us
information about relative depth of the image that is third
dimension of vision. Binocular disparity results when
image of an object falls on different areas of the two retinas
and binocular vision or stereopsis is impression of depth
resulting from differences in the images on these two retinas.
We lose stereoscopic vision in laparoscopy because both
eyes see same 2D pictures available on the monitor.
Fig. 41: Difference in angle of light on different retinas.
Stereoscopic vision is simultaneous vision with two eyes
(binuclear vision), producing a visual experience of the
third-dimension (the depth), i.e., a vivid perception of the
relative distances of objects in space. In this experience, the
observer seems to see the space between the objects located
at different distances from the eyes (the three-dimensions
are width, length, and depth).
It is present in normal binocular vision because the two
eyes view objects in space from two points, so that the retinal
image patterns of the same object points in space are slightly
different in the two eyes. The stereoscope, with which
differentpicturescanbepresentedtoeacheye,demonstrates
thefundamentaldifferencebetweenstereoscopicperception
of depth (third-dimension) and the conception of depth and
distance from the monocular view.
Humans normally have binocular vision, i.e., separate
images of the visual field are formed by each eye; the two
images fuse to form a single impression. Because each
eye forms its own image from a slightly different angle, a
stereoscopic effect is obtained and depth, distance, and
solidity of an object are appreciated. Stereoscopic color
vision is found primarily among the higher primates and it
developed fairly late on the evolutionary scale.
Binocular Vision
It refers to vision with two eyes. In binocular vision, the
visual axes of the eyes are arranged in such a manner that the
images of the object viewed strike the identical portions of
the retinas of both eyes. This produces a single stereoscopic
image—a view of the world in relief. Binocular vision also
makes it possible to determine visually the relative location
of objects in space and to judge their distance from each
other. When looking with one eye—i.e., with monocular
vision—the distance of objects can likewise be judged, but
not as accurately as with binocular vision.
Physiology of Three-dimensional Vision
Human eye is sensitive to the electromagnetic wavelength
between 400 and 700 nm. The “electromagnetic energy” in
the range of approximately “400–700 nm”
, which the human
eye can transduce, is called “light”
. The eyes transduce light
energy in the electromagnetic spectrum into nerve impulses.
In 1838, Charles Wheatstone published the first paper
on stereopsis entitled “On some remarkable and hitherto
unobserved, phenomena of binocular vision”
. In this, he
pointed out that the positional differences in the two eye’s
images due to their horizontal separation yielded depth
information. Prior to this time, the principal problem in the
study of binocular vision was “how the world seen as single
when we have two different views of it?” People thought
that only objects with the same visual directions, falling on
corresponding points, would be seen as single, all other
points would be double by means of the stereoscope that
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he invented. Wheatstone demonstrated that the stimulation
of noncorresponding points yield singleness of vision and
results in the perception of depth.
Cells in visual cortex are sensitive for binocular
vision. Some cells are sensitive for corresponding areas
of the left and right retinas and some have sensation for
noncorresponding areas of the two retinas. The difference
in image on the two retinas of eye is perceived by cortex as
a depth. Binocular disparity provides the visual system with
information concerning the 3D layout of the environment.
Recent physiological studies in the primary visual cortex
provide a successful account of the mechanisms by which
single neurons are able to signal disparity.
Recent studies of visual perception have begun to
reveal the connection between neuronal activity in the
brain and conscious visual experience. Transcranial
magnetic stimulation of the human occipital lobe disrupts
the normal perception of objects in ways suggesting
that important aspects of visual perception are based on
activity in early visual cortical areas. Recordings made
with microelectrodes in animals suggest that the perception
ofthelightnessanddepthofvisualsurfacesdevelopsthrough
computations performed across multiple brain areas.
Even though the picture on the monitor is 2D, the
operator can assume some depth due to different cues form
on ocular vision. This is known as depth cue (Fig. 42).
Among the entire depth cue mentioned above, only few
monocular are available on the monitor screen. Oculomotor
binocular depth cue such as convergence, accommodation,
and stereopsis is lost in 2D monitor screen.
Even though the picture is 2D, these depth cues help our
brain to interpret a 2D image into virtual 3D feeling. Today,
the picture on the screen is 2D but our brain is continuously
converting this 2D image in 3D by the help of different
monocular depth cues. This conversion of 2D pictures into
3D pictures by brain helps the surgeon to perform a task in
laparoscopic surgery.
Fig. 42: Different depth cues: The depth cues which are crossed are lost
in minimal access surgery.
Fig. 43: Shadow telescope by Schurr.
A telescope with light delivering through a separate
illumination cannula was developed by Schurr in 1996
(Fig. 43).
With slight modification, the section for minimally inva-
sivesurgery,UniversityofTübingenandMGBEndoskopische
Geräte GmbH Berlin Company have introduced a new
shadow telescope in 1999 (Fig. 44).
Shadow telescope is a rigid 10 mm endoscope with
30° view direction and uses additional illumination fibers
ending in an optimized distance behind the front lens. This
arrangement of illumination fibers creates a more natural
and more plastic appearance, a better balanced contrast, and
a well-dosed visible shadow. The shadow gives additional
secondary space clues and, therefore, improves orientation
and judgment of the 3D properties.
In shadow telescope, angle between the first and second
source of illumination is fixed and due to this shadow is also
fixed. The second problem with this telescope is that the light
which is creating shadow comes from below, but we do not
usually experience getting illuminated from the floor. All the
light in our day-to-day life is coming from above and most of
Fig. 44: Shadow telescope of Tübingen University.
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31
Fig. 45: Shadow in laparoscopy.
(MAS: minimal access surgery)
the time, the shadow we are seeing lies below the object. But
in this telescope, the shadow is above the object and so the
shadow seems to be unnatural.
INVENTION OF IDEAL SHADOW IN
LAPAROSCOPIC SURGERY
The first ideal shadow was introduced in laparoscopic
surgery by Dr RK Mishra in the University of Dundee, UK
(Fig. 45). This is based on the introduction of one additional
light source through a separate port for the generation of
natural shadow in minimal access surgery.
Due to the limitations of currently present shadows
producing techniques, necessity was felt for development
of some newer methods of shadow production. Shadow
can play a very powerful role in defining form by giving the
object a 3D feel and it is easy to generate. Although shadow
is an important depth cue, but too much shadow may cause
blurred working field for surgeons and shadow in wrong
direction may have adverse effect on the performance of
surgeon.
To increase the task performance in minimal access
surgery, we recommend certain general rules about
shadows. First, light which will cast shadow ideally should
come from above. Second, to enhance the task performance
with shadow, the contrast of shadow should be mild (22–
42%). This useful percentage of contrast can be achieved by
equal intensity setting and equal distance of both the light
sources from the operating field. Third, too much shadow
(>60%) should be avoided because very dark shadow can
increase the error rate by interfering with the view of plane
of dissection.
THREE-DIMENSIONAL VIDEO SYSTEMS
Three-dimensional Technology Systems
The most commonly used systems depend on rapid time
sequential imaging with two cameras and one monitor
and are based on the physiological phenomenon of retinal
persistence. Both channels alternate (open/close) with
sufficient speed (50–60 Hz) to avoid detection of flicker by
the human eye. The monitors must therefore have double
the frequency (100–120 Hz). Sequential switching between
the two eyes is necessary to ensure that the correct image
(left and right) falls on the corresponding retina otherwise
picture will overlap. This is achieved by wearing special
optical glasses that act as alternating shutters to each eye.
The current problem with these optical shutters, especially
the active battery operated liquid crystal display type shutter
is loss of brightness and color degradation. There is no
clinically proved evidence that current 3D systems improve
performance of laparoscopic surgery.
The current 3D technology is harmful to the surgeon on
prolonged use as it gives incorrect depth perception and
results in headache and eyestrain.
Another way in which 3D images can be obtained is a
mechanism by which the surgeon wears a polarized glass.
The shutter mechanism is present in the monitor. The final
image, however, occurs by the fusion of the two images in the
brain. The current 3D systems can only be operated from a
very close distance and if placed further will not produce the
desired 3D effect.
New Three-dimensional Techniques
Withtheincreasingdemandsfortechnologicaldevelopment,
many new techniques are currently under trial. These seem
to eliminate some of the problems encountered, but only
time and repeated use will tell.
Head-mounteddisplay(HMD)isaninterestingtechnique
that aims at normalizing the visual-motor axis. It consists of
a monitor and the necessary connections mounted to the
surgeon’s head with the power supply pack attached to
the back of the surgeon’s shirt. It is not very heavy and also
allows the surgeon to view peripherally.
The optical characteristics are:

■ Lines of resolution—420 × 320 lines

■ Contrast ratio—100:1

■ Horizontal field of vision—22°

■ Diagonal field—27.5°

■ Vertical field—19°.
The surgeon using the display will have to make
adjustments to the interpupillary distance, focus, and the
distance from his eyes each time. Studies have shown HMD
to have certain advantages. It is lightweight, comfortable
to position, reduces mental stress, is cheaper than monitor
systems, and decreases eyestrain. It allows the surgeon
to visualize the operative field directly (the abdomen
and ports). The problems, however, are that the picture is
granular, definition is not very good, and nausea can occur.
As mentioned before, the gaze-down position is said to
improve the performance of the surgeon as it brings the
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in 2D pictures. This improves the sense of depth and it does
not require binocular depth cues. It is also said to reduce
fatigue and eyestrain. However, this system does not bring
about any changes to resolution, brightness, and color.
Augmented reality (AR) is a 3D computer vision
technique that is characterized by the real-time fusion
of virtual elements on a real space. Currently, AR offers
enormous potential in many fields such as education,
simulation, architecture, advertising, navigation devices,
medicine, and rehabilitation. Minimal access surgery
is the branch of medicine where AR has more potential
for application. New innovations such as Microsoft
HoloLens and the emerging mass market of VR headsets
would indicate that these technologies will become
familiar to surgeons and inevitability we will find a way
to integrate them into our day-to-day practice. The challenge
of identifying compelling and valuable experiences for
these modalities now begins along with validation of their
benefits in all aspects of surgical care. The digital surgical
environment is about to drastically change in near future.
Advancement in TV System Technology
High-definition and Ultra-high Definition Television
Another remarkable advancement in technology is the high-
definition television (HDTV) and 4K TV. It uses component
signals, the resolution of the picture is much better, and there
are no distortions.
PALplus
The alternatives to HDTV are the PALplus which is an
advanced modification of PAL and D2-MAC, HD-MAC which
are used for satellite transmissions.
These systems, however, require large amounts of space
and can cause problems during transmission. Due to the
increased definition, small unwanted movements can be
magnified and visual stress can be increased.
Some systems are currently under evaluation and their
requirements are given in Table 3.
Fig. 46: Projection systems in minimal access surgery.
alignment between his hands and eyes to normal.
This principle has been used in a project called “view-site”
.
This mechanism is used to project the operative field image
onto a sterile screen placed on the patient’s abdomen close
to the original area of surgery. However, it cannot be used for
extensive procedures as the image field is small, resolution
is not up to the mark, and separation and identification of
tissue planes become difficult if bleeding was to occur.
Image display systems are now available which project
the image onto a sterile screen overlying the chest of the
patient. This aids both cerebral processing of the image and
endoscopic manipulations and improves both quality and
efficiency of performance (Fig. 46). The limitations of the
current “gaze-down” image display systems are diminished
resolution and encroachment of the operative field by the
sterile screen.
Suspended Image System
An experimental system [suspended image system (SIS)]
being developed at the University of Dundee and the Central
Research Laboratory (EMI) projects the image in air on top of
the patient, which means that there is no screen to obstruct
the surgeon’s movement. This is called the SIS. It consists
of two components: (1) a high precision retroreflector and
(2) a beam splitter. With the help of these, the system can
produce images with good resolution and can suspend them
on top of the patient in close vicinity to the operative site.
The advantages of this method are that there is no distortion,
object can be placed anywhere, focal length is not specific,
and the image is similar to the original in size. This system
is also said to improve the sense of depth, as there are no
anticues. Also, the visual-motor axis is correctly aligned for
optimal performance.
VISTRAL is a system currently under trial. The advantage
of this system is that it does not allow flatness cues to occur
TABLE 3: Different types of TV system.
System
Japan
(NHK/Sony)
Europe
(EUREKA 95) USA
Number of lines 1,125 1,250 1,050
Visible lines (92%) 1,035 1,150 966
Pixels per line 1,831 2,035 1,709
Total number of pixels 1,895,085 2,340,250 1,650,894
Field frequency [cycles per
second (cps)]
60 50 59
Luminance 20 20 20
Chrominance 7 7 7
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