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Electric discharge during electrosurgery


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Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating current with strongly contracted positive column with current densities reaching 10(3) A/cm(2). The plasma electron density and electrical conductivities in the channel were found be 10(16) cm(-3) and (1-2) Ohm(-1)cm(-1), respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown threshold.
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Electric discharge during electrosurgery
Alexey Shashurin
, David Scott
, Taisen Zhuang
, Jerome Canady
, Isak I. Beilis
& Michael Keidar
Department of Mechanical and Aerospace Engineering, School of Engineering and Applied Science, The George Washington
University, Washington, DC 20052, USA,
Jerome Canady Research Institute for Advanced Biological and Technological Sciences,
6930 Carroll Avenue, Suite 300, Takoma Park,MD 20912,
School of Electrical Engineering, Tel Aviv University, Ramat Aviv 69978.
Electric discharge utilized for electrosurgery is studied by means of a recently developed method for the
diagnostics of small-size atmospheric plasma objects based on Rayleigh scattering of microwaves on the
plasma volume. Evolution of the plasma parameters in the near-electrode sheaths and in the positive column
is measured and analyzed. It is found that the electrosurgical system produces a glow discharge of alternating
current with strongly contracted positive column with current densities reaching 10
. The plasma
electron density and electrical conductivities in the channel were found be 10
and (1-2) Ohm
respectively. The discharge interrupts every instance when the discharge-driving AC voltage crosses zero
and re-ignites again every next half-wave at the moment when the instant voltage exceeds the breakdown
lectrosurgery has been utilized for cutting and coagulating tissue for about 90 years
. Electrosurgical
coagulation has improved treatment of many gastrointestinal diseases such as radiation proctitis,
Barrett’s esophagus, gastric antral vascular ectasia, and arteriovenous malformations
. Additionally, it
may decrease postoperative swelling and inter-operative blood loss for other areas of the human body such as
knee joint replacement.
Electrosurgical Argon Plasma Coagulation (APC) utilizes plasma produced by the ionization of a few milli-
meter diameter argon flow exhausting into ambient air from the electrosurgical hand-piece. The intensity of
treatment and the effect induced in the living tissue strongly depends on the plasma properties
. Such atmo-
spheric pressure microplasmas are difficult to study using conventional diagnostics. Microwave interferometry
operating in the GHz frequency range fails due to the small size of the plasma compared to the microwave
wavelength causing diffraction and unsufficient phase change. Electrostatic probes introduce very strong per-
turbations once inserted into the plasmas, and are associated with difficulties of interpretation at strongly-
collisional atmospheric conditions
Recently a few methods for the measurement of atmospheric pressure plasma parameters were proposed.
This includes various spectroscopic techniques, namely passive optical emission spectroscopy, laser-induced
fluorescence spectroscopy, diode laser absorption spectroscopy and Rayleigh, Thomson and Raman scattering
of laser radiation on microplasmas
. These techniques are characterized by good spatial resolution (down to
10–50 mm) and minimal detectable values of plasma electron density of ,10
, but require great stability of
the discharge since they are based on averaging over large number of discharge events.
An alternative approach capable of detecting low plasma densities (down to 10
) at atmospheric
pressure is Rayleigh scattering of microwave radiation on microplasmas
. The concept of the method was first
proposed theoretically by Shneider
, and then implemented experimentally in studies of laser-induced avalanche
ionization in air, resonance-enhanced multi-photon ionization in argon and non-thermal atmospheric plasma
jets (widely utilized recently for biomedical applications)
. The method consists of measurements of radi-
ation scattered from microplasmas irradiated by microwaves in the GHz frequency range. In the Rayleigh regime,
the electric field amplitude of the scattered wave is proportional to total number of electrons in the microplasmas
and thus, the plasma electron density can be determined if the plasma volume is known
The type of discharge and the plasma parameters utilized during electrosurgical coagulation has not been
extensively studied, even though this type of plasma source probably has the widest practical application in
medicine thus far. In this work, we utilize an electrosurgical system produced by US Medical Innovations LLC,
and present for the first time, measurements of plasma discharge parameters and discuss processes developing in
the positive column and in the near-electrode sheath.
Experiment. Electrosurgical system. The experiments were conducted using the electrosurgical system SS-200E/
Argon 2 in combination with the electrosurgical Canady Vieira Hybrid Plasma scalpel by US Medical Innovations
LLC shown in Fig. 1 (see Ref. [29] for histological studies). The Canady Vieira Hybrid Plasma scalpel is comprised
29 October 2014
9 March 2015
16 April 2015
Correspondence and
requests for materials
should be addressed to
A.S. (shashur@gwu.
edu) or M.K. (keidar@
SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 1
of a flexible hose ending with a hand-piece
. The hose delivers argon
flow and electrical power produced by the electrosurgical generator
to the hand-piece. The hand-piece is nearly a cylindrical hollow
volume with a high-voltage tungsten electrode of about 1 mm in
diameter installed on the axis and surrounded by the argon flow.
The hand-piece is equipped with a 2.4 mm opening at its distal end
through which the argon flow exits into the ambient air. The
electrode was protruded about 5 mm from the distal end in the
experiments. The electrosurgical unit (ESU) was utilized in a range
of power settings from 15 to 60 Watt and 3 LPM argon flow rate.
Inorganic replica of the living tissue. The power produced by the ESU
is delivered into the biological tissue by means of an argon plasma
column producing an electrically conductive channel between the
high voltage electrode of the electrosurgical hand-piece and the tis-
sue. A photograph of the SS-200E/Argon 2 in operation in Argon
Plasma Coagulation (APC) mode with a fresh chicken liver sample is
shown in Fig. 2(a). Application of the ESU to the tissue sample
produces instant tissue burning, accompanied with smoke produc-
tion at the treated point [see Fig. 2(a)]. Additionally, the plasma
column attachment to the tissue is non-steady and characterized
by fluctuations and motion of the plasma column around the tissue.
To avoid problems with the non-reproducibility of the measure-
ments, due to non-steady motion of the plasma column over the
tissue, the experiments were conducted using an inorganic replica
of the tissue made of two metal electrodes separated by water gap [see
insert in Fig. 2 (b)]. A photograph of the ESU in operation in the APC
mode with the inorganic replica is shown in Fig. 2 (b). It was observed
that the discharge with the inorganic replica sample produced quasi-
steady, immovable diffusive attachment to the replica electrode tip as
shown Fig. 2 (b). All measurements were conducted at a separation
distance between the replica electrode tip and the electrosurgical
hand-piece tip of about d54.5 mm.
The water gap size in the replica sample was adjusted to obtain
current and voltage waveforms similar to that of the chicken liver
tissue samples. The waveforms of the voltage produced by the ESU
) and the discharge current (I
) were similar for both samples
(peak voltage of about 2 kV and peak current ,1 A for 60 W and
3-3.5 LPM) as shown in Fig. 2.
The details of the electrical schematics are shown in Fig. 2. The
electrical circuit was as follows: ESU (Accessory port) R electrosurgical
scalpel R tissue on patient pad/replica R ESU (Patient port). Note, for
experiments conducted with biological samples tissue was placed on the
standard patient pad, while inorganic replica experiment s were made
with no patient pad (see schematic in Fig. 2). The Patient port of the ESU
was grounded in all experiments as shown in Fig. 2.
Microwave scattering diagnostics. The schematics of the Rayleigh
Microwave System (RMS) are presented in Fig. 3. Linearly polarized
microwave radiation (10.58 GHz) was scattered on the collinearly-
oriented plasma channel and then the scattered signal was measured.
Microwaves were irradiated and detected using two horns shown in
Fig. 3. The detection of the scattered signal was accomplished using a
homodyne I/Q Mixer, providing in-phase (I) and quadrature (Q)
outputs. The total amplitude of the scattered microwave signal was
determined by: U
. The amplifiers and the mixer used
in the microwave system operated in a linear mode for the entire
Figure 1
Photograph of electrosurgical system SS-200E/Argon 2 with
connected electrosurgical Canady Vieira Hybrid Plasma Scalpel by US
Medical Innovations, LLC.
Figure 2
Photograph of the ESU in operation in Argon Plasma
Coagulation mode, electrical schematics and current/voltage waveforms
of the discharge for ESU power 60 W and flow rate - 3-3.5 LPM:
(a) chicken liver sample, (b) inorganic replica. Similar voltage and current
waveforms indicate good agreement of the electrical properties of tissue
sample and inorganic replica.
Figure 3
Schematics of the RMS system utilized in this work.
SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 2
range of the scattered signal amplitudes, thereby ensuring that the
output signal U
is proportional to the electric field amplitude of
scattered radiation E
at the detection horn location: U
The absolute value of the plasma electron density, conductivity
and electric field in the plasma channel were determined from
Eq. (4)–(6) according to the methodology developed in Methods.
A digital oscilloscope was used to simultaneously record signals for
the microwave system, along with the electrical parameters of the
discharge. In addition, the plasma column was simultaneously
photographed using an Intensified Charge-Coupled Device
(ICCD) camera: Andor USB iStar.
Fig. 4 presents the waveforms of the total voltage produced by the
) as well as the discharge current (I
). One can see that
the ESU produces a series of high voltage bursts, having a peak
amplitude of about 1 kV and a repetition frequency of about
60 kHz which are filled with sinusoidal oscillations at about
600 kHz. Two stages can be distinguished on the operation cycle,
namely the active and inactive stage as indicated on the Fig. 4 by the
darker and brighter bars, respectively. The active stage (t,0-4 ms) is
characterized by the presence of the non-zero discharge current
spikes (I
peak values up to 250-300 mA) and a bright plasma column
oscillating between the discharge electrodes as shown in the typical
discharge image in Fig. 4 (the image is taken at t50 ms). The inactive
stage (t,4–16 ms), is characterized by an absence of the discharge
50) and a dark inter-electrode gap.
The active discharge stage is shown in more details in Fig. 5. It was
observed that a bright discharge column develops between the elec-
trodes in the volume occupied by argon gas and oscillates overlap-
ping (covering) left and right discharge electrodes by turns (see e.g.
image T1 in Fig. 5 where plasma column covers the tip of the right
electrode; image T3 same for the left electrode). One can see that the
plasma column always overlaps the electrode that is negative at this
particular moment (instant cathode) - see images T1, T3 and T4 in
Fig. 5. Time intervals in vicinity of the voltage zeroes (U
,0) were
associated with the presence of the plasma column strictly between
the electrodes without any electrode overlapping - see image T2 in
Fig. 5.
The total AC voltage produced by the ESU (U
) represents the
sum of the discharge voltage (U
) and the voltage drop on the replica/
tissue sample (U
): U
5 U
. U
was determined by
subtracting the voltage measured at the surgical probe from that
measured at the replica electrode. Waveforms of the discharge volt-
age and current are shown in Fig. 6. One can see that breakdown
occurred at about 1.2 kV and afterwards the discharge voltage was
generally in the range ,300–400 V.
The diameter and length of the interelectrode plasma channel
and the area of its attachment to the discharge electrodes were
determined from processing of the instant discharge photographs
taken with an ICCD camera (see Fig. 5) and summarized in
Table 1. The length of the plasma column coincided with the size
of the interelectrode gap (plasma column length ,4.5 mm). The
diameter of the discharge column was ,0.3 mm and slightly
increased with ESU input power. Area of the attachment to the
instant cathode was measured from the clearly observed illuminated
part of the cathode surface at the moment of maximum discharge
current (see images T1 and T2 of Fig. 5). For the replica electrode, this
corresponded with the moment I
peaked during the 1st positive
Figure 4
Total AC voltage (
) and discharge current (
) produced by
the ESU system for an input power of 15 Watts and an argon flow rate of
3 LPM. The discharge-driving voltage represents a sequence of the high
frequency, high voltage pulses. The operation cycle has two stages, namely
the active (t,0–4 ms, darker bar) and inactive stage (t,4–16 ms, brighter
bar). Typical photographs of each stage are presented for time moments
t 5 0 and 9.8 ms respectively (exposure time 20 ns).
Figure 5
Temporal evolution of discharge voltage (
) and discharge
current (
) of the electrosurgical system SS-200E/Argon 2 for
and flow5 3 LPM. Photographs of the interelectrode gap at different
moments of time T1-T4 are shown on the right.
Figure 6
Discharge voltage (
) and discharge current (
) for 60 Watts
and argon flow rate 3 LPM.
SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 3
half-wave and occurred at the surgical probe when I
peaked during
the 1st negative half-wave.
Temporal evolution of the average plasma electron density and
electric field in the interelectrode column measured using RMS sys-
tem is shown in Fig. 7. One can see that the peak values of the electric
field in the plasma channel and plasma electron density reached
about 350 V/cm and 8.10
respectively, at an ESU input power
of 15 Watts. Dependence of the maximum plasma electron density
with ESU power is shown in Fig. 8. n
increased with ESU power
reaching about (0.9-1)
for 60 Watts.
Temporal behavior. Let us discuss the evolution of the plasma
parameters in the positive column and in the near-electrode
sheath. The experimental data indicates that the discharge was not
continuous during the active stage. Instead, it was interrupted every
time the discharge-driving voltage crossed zero (U
,0) and was
re-ignited on the next voltage half-wave (see Fig. 5 showing that
moments when the voltage crosses zero were accompanied by sub-
microsecond, quiescent intervals when I
remained at ,0).
In order to analyze the nature of the discharge interruptions,
it is important to discuss plasma decay rates. When discharge
driving voltage is changing polarity and the cathode switches to
another electrode, the sheath formed near the ‘‘old’’ cathode starts
to decay. Photographing of the discharge demonstrates an almost
instantaneous termination of the cathode sheath when the discharge
driving voltage crosses zero (compare images T1 and T2 in Fig. 5),
which can be explained by fast recombination of plasma at the elec-
trode surface
. Instant sheath termination causes the discharge cur-
rent to remain low in the beginning of every next half-wave, until the
discharge-driving voltage reaches about V
,300 V and breakdown
occurs again. The breakdown restores the cathode sheath near the
‘‘new’’ cathode and causes an observed peak in the discharge current
(see Fig. 5)
. The discharge lasts until the discharge driving voltage
changes sign again and the process is repeated. When the amplitude
of U
oscillations decreases below 300 V (starting at the 6
cycle in Fig. 4), no further breakdown is possible and this indicates
the start of the inactive stage, which lasts for about t
,12 ms (brighter
bar in Fig. 4) when the plasma is decaying.
The positive column also experiences significant decay during the
discharge interruptions as one can see from the direct measurements
of the interelectrode plasma electron density shown in Fig. 7.
Both estimations (using typical electron-ion recombination coef-
ficient ,10
and experiments indicate that n
decays to
during the discharge interruption lasting about a fraction
of a microsecond, when discharge driving voltage is changing sign.
This remaining plasma causes a glow in the gap shown in photo-
graphs in Fig. 5 during the discharge interruptions in contrast with
almost instant termination of the glow around the cathode. It is
interesting to note that, in contrast with plasma electron density,
the conductivity of the plasma channel does not reduce significantly
during the discharge interruptions (see Fig. 7). This is related to the
simultaneous decrease of electron collisional frequency around zero
when the electric field in the column is crossing the zero
(see Fig. 7).
Therefore, the discharge produced by the electrosurgical system
SS-200/Argon 2 represents an AC discharge as opposed to an RF
discharge, where near electrode plasma sheaths are permanent and
do not decay significantly over the period of oscillation
. The
discharge is governed by an instant value of the applied AC voltage
and the amount of plasma remaining after the last breakdown event.
Table 1
Cross-sectional areas of the positive column and areas of attachment to the instant cathodes. The attachment areas to the instant
cathodes were measured at moment of the corresponding discharge current peaks (for the cathode at replica electrode I
peak at 1
positive half-wave and for the cathode at the surgical probe - I
peak at 1
negative half-wave). ESU argon flow rate was set to 3 LPM.
P515W P540W P560W
Cross-sectional area of positive column, cm
Area of attachment to the replica electrode, cm
Area of attachment to the surgical probe, cm
Figure 7
Temporal evolutions of electric field, collisional frequency,
plasma conductivity and plasma electron density in the positive column
produced by electrosurgical system SS-200E/Argon 2 at
515 W and
argon flow53 LPM.
Figure 8
Maximum electron density versus input power of the
electrosurgical system SS-200E/Argon 2 (flow53 LPM).
SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 4
The discharge interrupts every time when the discharge voltage
changes sign due to the decay of the near-cathode sheath and
re-ignites on the next voltage half-wave in the vicinity of the ‘‘new
cathode", when voltage increases above the breakdown threshold and
a cathode sheath is formed near the ‘‘new cathode’’.
Positive column and near-cathode sheath. Let us now discuss some
parameters of the cathode sheath determined in this work. As shown
in Fig. 5, the discharge re-ignites at around V
,300 V, which
corresponds to a well-known minimum voltage required for
self-sustained DC discharges (minimum breakdown voltage of
Paschen curve)
. The current density at the instant cathode was in
the range of 10–20 A/cm
on the stainless steel replica electrode and
5-10 A/cm
on the tungsten surgical probe electrode as show in Fig. 9
(based on measured I
and area of attachment shown in Table 1).
These current densities are close to previously measured normal
current densities in glow discharges, indicating that nearly normal
cathode layer is established
. The depth of the cathode sheath can be
now estimated from Paschen curve minimum (using (p d)
Torr for argon and thus d
[cm]51/p[Torr]) yielding cathode sheath
thickness d
<10 mm
It should be noted that higher breakdown voltage ,1 kV observed
during the first high voltage oscillation compared to that on the
following cycles when breakdown happens around Paschen’s curve
minimum ,300 V (see t,0 in Fig. 5 and Fig. 6) can be explained as
follows. This is caused by the fact that for the first oscillation the
entire gap has to breakdown, while on the following half-waves,
a well-conducting plasma channel remains after the discharge is
interrupted (see conductivity waveform in Fig. 7) and only the
near-cathode sheath needs to breakdown.
Visual observations indicate that attachment of the discharge
channel to the living tissue sample may differ from the quasi-steady,
diffusive attachment observed at the surgical probe. Instead, the
attachment of the plasma column to the tissue was non-steady,
accompanied with random motion over the tissue while the plasma
column at the point of contact with the tissue was contracted. It
should be noted that the scenario of the non-steady contracted
attachment can be mimicked with the replica at low ESU powers
and flow rates. Visual observations of the attachment to the replica
electrode indicate that a decrease of power and flow rate causes
sporadic transitions from quasi-steady, diffusive to non-steady, con-
tracted attachment. This transition is captured in Fig. 10 for an ESU
power of 20 W and an Ar flow rate 2.5 LPM. It was observed that
transition to the non-steady, constricted attachment was accompan-
ied by an abrupt increase of I
and a decrease of U
,100V which
indicates transition to arc.
Experiments indicate that current density and electrical conduct-
ivities in the positive column were up to 10
and (1-2)
, respectively. These values of the current density sig-
nificantly exceed normal current densities of glow discharges, and
along with high measured plasma electron density in the channel
are typical for contracted (filamented) positive col-
. Typically, plasmas at such conditions are nearly thermal
and therefore, gas temperatures of about several thousand K might
be expected in electrosurgical plasmas
. Note, since measured
plasma electron density is relatively high, other diagnostic techniques
such as Stark broadening and Thomson scattering can be potentially
utilized for testing of such plasmas.
Let us now discuss how utilization of the inorganic replica instead
of the living tissue affects the discharge. Experiments indicate that
discharge attachment was different in these cases, namely non-steady
attachment to the living tissue versus quasi-steady attachment to the
replica. This can be explained by the fact that application of the ESU
to the living tissue causes instant localized burning of the tissue
which leads to a change in its local physical properties (electrical
conductivity, thermal conductivity etc.) and causes a shift of the
discharge column to the new unburnt location. In other words, the
tissue can be considered as an electrode with constantly fluctuating
properties. Since tissue burning causes carbonization, it may be
hypothesized that averaged over time, the surface layer of the living
tissue in contact with the plasma would exhibit properties similar to
the electrode made of carbon. Also, since the effect of the cathode
material on the discharge characteristics (such as cathode fall, break-
down voltage, plasma properties in the positive column etc.) is fairly
, it can be concluded that the properties of the discharges with
the inorganic replica and the living tissue are similar. Similarity of the
discharge current and voltage measured with the inorganic replica
and with the living tissue also supports this conclusion.
The discharge produced by the electrosurgical system SS-200E/
Argon 2 was studied experimentally. The plasma electron density
was measured in the range of (7.5-9.5)
for applied powers
of 15-60 Watts. The discharge can be classified as a glow discharge of
the alternating current with contracted positive column. The dis-
charge ignites every half-wave of the driving voltage when voltage
increases above the breakdown threshold and is interrupted at the
end of each half-wave when the voltage approaches zero.
Electron density measurements. A methodology for electron density measurement
by means of microwave scattering on elongated atmospheric pressure plasma
channels will be developed. It should be noted that this consideration differs from that
conducted by Shneider in Ref. [23] for short plasma channels when the restoring force
produced by the channel ends with non-compensated charges is significant. In
contrast, the case for when channels have large aspect ratios (when the contribution of
the channel ends is negligible) will be presented. The method described in this section
considers the general case of both free-standing plasma channels and those attached
to the discharge electrodes. Furthermore, it presents an approach to determine the
electric field and takes into account the depolarization effect and dependence of
collision frequency on the magnitude of the electric field, in contrast with simplified
description in Ref. [22].
Figure 9
Current densities at cathode and in positive column.
Figure 10
Discharge voltage and current waveforms indicating sporadic
transition between modes with steady and non-steady attachment to
the cathode on the positive half-wave (ESU power - 20 W, Ar flow
rate - 2.5LPM).
SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 5
Let us consider the scattering of microwaves on the conductive or dielectric
channel having slender prolate shape when channel length (l) significantly exceeds
the diameter (d). An incident microwave radiation oriented along the channel excites
oscillations of the electric current along the channel. The amplitude of the microwave
electric field in the channel for the general case of scatterers with dielectric permit-
tivity e and conductivity s when channels are thin compared to skin depth
mm for microwave frequency ,10.58 GHz use in this work) can be
written as:
where k - depolarization factor governed by the channel geometry, E
- incident
microwave electric field at the channel location
. The depolarization factor k for the
channels with large aspect ratio m5l/d?1 is small: k<
ln (m)=1
For the plasma considered in this work, the skin depth d,0.5 mm (s,1 V
according to experimental data) exceeds plasma channel diameter d,0.2 mm and
m,20 which yields depolarization factor ,7.10
. Thus, the electric field inside the
channel is close to E
. The amplitude of the resultant electrical current excited in the
plasma channel can be written as I5s E
S for a pure conductor and I5e
(e21) v E
for a pure dielectric. The distribution of the current along the channel can be con-
sidered nearly uniform if the distance to the radiating horn is large, therefore the front
of the incident wave is nearly flat on the channel length: r
/l where l - wavelength
of microwave (channel is in a far zone).
Electrical current in the channel oscillates at the frequency of the incident micro-
wave field and therefore, it represents a radiating antenna. In the far-field, when the
distance from the detecting horn to the radiating channel r
/l, the radiation
pattern coincides with radiation from a Herzt dipole with oscillating current I.The
overall power radiated by the channel averaged over the microwave period can be
written as follows: P~
The output signal measured by the linear microwave detection system described in
the Experimental Details section is proportional to the electric field in the radiated
wave at the location of the detecting horn E
and thus: U
. For a
microwave system with fixed operational parameters (such frequency, horn locations
etc.), the dependence of U
is governed by the following propertied of the scatterer
l: ð1Þ
Combining Eq. (1) with the above expressions for current excited in the channel it
can be found that the dependence of output RMS signal on parameters of the scat-
tering channel can be expressed as follows:
~AsV {for conductor ð2Þ
~A e
(e{1) v V {for dielectric ð3Þ
where A –proportionality coefficient and V - channel volume (V5 Sl).
The proportionality coefficient A is a property of the specific microwave system
(utilized elements, geometry, microwave power, etc.) while independent of scatterer
properties and it can be found using scatterers with known properties. Utilization of
prolate-shaped metal cylinders to determine A is problematic due to smallness of skin
layer depth in metals for microwave frequencies (, 1 mm for 10 GHz for copper).
Therefore, utilization of dielectric scatterers is preferable to determine A using
Eq. (3). The constant A was found to be 214 V V/cm
using dielectric scatterers
with known volume and dielectric permittivity similar to that described in details
in Ref. [22].
Let us first apply this method to determine the electric field E in the tested plasma
channel. Note: E is assumed here to be governed by the processes developing in the
tested plasmas, rather than the amplitude of the microwave electric field in the plasma
channel. This imposes a condition on the maximum microwave power level that can
be utilized for the diagnostic system to ensure that the entire microwave system is
non-invasive with respect to the processes developing in the tested plasmas.
The amplitude of the microwave field used in this work can be estimated to be
, 1 V/cm which is significantly lower than E caused by the discharge (see Fig. 7).
If the current flowing through the plasma channel is known (e.g. for the case of a
discharge initiated between two electrodes), the average electric field in the plasma
channel can be determined using Eq. (2) as follows:
, ð4Þ
where j
discharge current density and I
–discharge current.
Now let us apply the developed methodology to determine the plasma conductivity
and electron density in the plasma channel. For many practical cases, the two
following conditions are satisfied for atmospheric plasmas. First, plasma ionization
degree is low enough so that electron collisions are governed by collisions with gas
particles (n
). Second, electron collisional frequency is significantly larger than
microwave frequency v, meaning that the plasma channel can be treated as
a conductor since the ratio of conductivity current
to the polarization current
excited in the plasma channel
?1 ?1
. Both of these conditions
are satisfied for typical atmospheric plasmas (n
compared with v,10
ionization degrees ,10
. In this case, plasma conductivity can be found
from Eq (2):
Plasma electron density can be found from s and electron collision frequency n
2:82 10
Generally speaking, electron collision frequency depends on the electric field in the
channel (E) and thus n
in Eq. (6) is not constant, but instead n
5 n
(E). This
dependence for argon utilized in this work is plotted in Fig. 11 (determined from data
in Ref. [30]). Note, static collisional frequencies shown in Fig. 11 can be utilized if the
electric field changes weakly on the time between the collisions (up to frequencies
of E oscillations ,10
GHz). Therefore, the electric field found from Eq. (4) has to be
used in combination with dependence n
(E) in order to determine the plasma
electron density using Eq. (6).
It is important to make a few notes on the applicability of the methodology
developed here. First, the method can be applied for both free-standing plasma
channels, when radiating antenna size coincides with the size of the plasma channel
(such as laser-induced plasma)
, as well as for plasmas in contact with the discharge
electrodes, when radiating antenna is comprised of plasma column along with pieces
of adjacent electrodes. Indeed, since the excitation of the electric current in the
channel is driven by the amplitude of the incident wave, microwave scattering from
the stationary discharge electrodes contributes to the DC component of the output
signal U
(similar to the contribution from other surroundings) which is filtered
out from the transient signal scattered from the plasma. Second, since it is typical that
near electrode sheaths, which form at the contact of the plasma channel with the
electrodes, be short compared to the plasma channel length, their contribution to the
resultant scattered signal is small. In this case, Eq. (4)-(6) is applicable for measure-
ments of average values of plasma electron density, electrical conductivity and electric
field in the positive column.
Summarizing the above spatially-averaged plasma electron density in small
atmospheric plasma objects can be determined using scattering of microwaves on the
plasmas. In the case of elongated plasma channels, the radiation has to be polarized
along the channel and the microwave frequency has to be chosen so that
f ½GH
to ensure that channel is thin compared to the skin layer depth.
This method measures the total number of electrons in the plasma volume and the
current setup has sensitivity down to ,10
electrons. The error of the plasma density
measurement is governed by the accuracy of the plasma volume determinations, and
it was 10-15% in current experiments. If the electrical current in the plasma channel is
measured independently, this method can be also utilized for the determination of the
electric field.
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This research was supported by US Medical Innovations. L.L.C. Authors would like to thank
Dr. M.N. Shneider for very fruitful discussions.
Author contribuions
A.S. conceived and designed the experiments, performed research, analyzed the data and
wrote the manuscript. D.S performed research and analyzed the data. T.S. and I.I.B
discussed results of the study, provided assistance in manuscript writing. M.K. and J.C.
conceived the project, discussed results of the study, provided assistance in manuscript
Additional information
Competing financial interests: The authors declare no competing financial interests.
How to cite this article: Shashurin, A. et al. Electric discharge during electrosurgery.
Sci. Rep. 4, 9946; DOI:10.1038/srep09946 (2014).
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SCIENTIFIC REPORTS | 4 : 9946 | DOI: 10.1038/srep09946 7
... PlasmaDerm was approved as a medical device in Europe in 2013 following a one-year clinical study on 14 patients for chronic wound therapy [38]. Another plasma device with considerable clinical promise is the Canady Helios Plasma 1 Scalpel (US Medical Innovations, LLC, USA) [39], [40], which is a plasma electrosurgical device [41] [device in top of its generator shown in Fig. 4(b)]. It has been proven to reduce tissue damage, blood loss, surgery time, and transfusion rate in late-stage cancer patients while also promoting survival with no adverse effects. ...
... (A) Plasmology4, Inc., Scottsdale, AZ, USA, developed the Plaz4 plasma jet and reproduced, with permission, from [33]. (B) Canady Vieira Plasma 1 Scalpel with SS-200E/Argon 2 (US Medical Innovations, LLC) linked electrosurgical system and reproduced under a Creative Commons CCBY license from[41]. ...
Cancer is a devastating and life-threatening disease. It is the second leading cause of death worldwide after heart diseases. While science has significantly advanced to improve the treatment outcome and quality of life in cancer patients, there are still many issues with the current therapies, such as toxicity and the development of resistance to treatment. Among the novel tools to overcome these limitations is nonthermal plasma (NTP) and its treatment regimens. Recent progress in NTP devices with ion temperatures close to room temperature demonstrated significant potential in cancer therapy. NTP devices provide a unique combination of reactive oxygen species (ROS), reactive nitrogen species (RNS), photons, and electric fields that exhibit desirable properties of triggering cell death pathways, selectively for cancer cells. While in principle NTP is nonnecrotic and gentle to the tissue, but reactive oxygen and nitrogen species (RONS)-triggered tumor cell death exhibited to have pro-immunogenic properties. Many in vitro and in vivo experiments have demonstrated antitumor effects of direct NTP, synergistic applications of NTP with anticancer drugs/treatments, and plasma-conditioned medium (PCM) applications against a variety of cancer cells. The latest results and findings in this field are the subject of this review along with a brief lay-reader-explanation of cancer and immunology. In this review, initially, we give an overview of the literature that deals with studies on the use of NTP for cancer treatment. Subsequently, we present typical results from that literature to illustrate the advances of NTP in oncology. Finally, we discuss some challenges and future scopes offered by NTP for cancer treatment.
... They have been in use for about 90 years and have a direct impact on clinical results [1][2][3][4]. By allowing for hemostasis during surgery, electrosurgical units give the surgical team better visual access to the area under surgery [2], reduce the need for blood transfusion, curtail the length of anesthesia and surgery, and prevent local hematomas after surgery [2][3][4][5][6]. ...
... The statistically signi cant difference between the pretest and posttest performance of the operating room nurses with regard to items 2, 3,5,9,11,12,16,21,25,26,27, 28, and 30 shows that they were in uenced by the educational content of the poster: the nurses' mean score was signi cantly higher after intervention. With regard to the other items of the checklist, absence of a statistically signi cant change in the nurses' performance indicates that the educational intervention had not been effective, which can be attributed to various factors, including lack of specialized equipment in operating rooms or nonstandardization of operating rooms for application of the latest equipment and facilities. ...
Full-text available
Background: An electrosurgical unit is one of the most essential pieces of equipment in operating rooms. Over 80% of operations today make use of electrosurgical units. Training operating room nurses in correct application of electrosurgical units and evaluation of their application play a key role in making optimal use of the units and extending their lifetime, reducing occupational hazards for surgical teams, and enhancing the safety of patients. The present study aims to investigate the effects of an educational intervention on operating room nurses' application of electrosurgical units. Methods: The present study is a quasi-experimental work of research conducted in all the operating rooms of the hospitals located in Shiraz, Iran. Data were collected from 200 observations of 200 surgeries (100 before intervention and 100 after). The content of education was derived from a literature review and standard guidelines and was presented as a poster in the operating rooms. The data collection instruments consisted of a Demographic Information Questionnaire, a surgery checklist, and the checklist for operating room Nurses' application of electrosurgical units. Data were collected once before the intervention and then again one month after the intervention. The collected data were analyzed using the descriptive statistics of chi-square test and paired t-test at a significance level of 0.05 in SPSS v. 18. Results: The average age of the participating nurses was 31.540±6.772 years. The majority of the participants were female. The results showed a statistically significant difference between the means and standard deviations of the nurses' application of electrosurgical units scores before (18.330±2.666) and after (20.820±3.400) intervention. Conclusion: Introducing operating room nurses to the standard guidelines for application of electrosurgical units can improve the quality of services provided by the nurses, increase the safety of patients, and reduce occupational hazards. Thus, to improve operating room nurses' professional performance in application of electrosurgical units, medical managers and policy-makers should attach more importance to on-the-job training programs.
... Saat ini terdapat dua pilihan untuk pengobatan kanker plasma yang tersedia yaitu secara langsung dan tidak langsung. Uji klinis pengobatan kanker menggunakan plasma non-termal (pengobatan plasma langsung; direct plasma treatments) sedang berlangsung di Jerman (8) dan Amerika Serikat (9). Terdapat 2 (dua) jenis pengobatan plasma tidak langsung (indirect plasma treatments) telah diusulkan, yaitu: (1) Plasma-assisted immunotherapy (PAI) (10); dan (2) Plasma-activated medium (PAM) (11,12). ...
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Plasma pharmacy or “Plasma medicine”, is currently getting better developments in its application in the field of medicine, especially pharmaceuticals, but this time the discussion will concentrate on cancer treatment. Various new plasma diagnostic techniques have been developed in an effort to understand the physics of CAP, including convincing evidence that the selectivity of CAP against cancer cells has been widely produced. This review summarizes and presents the application of CAP in cancer specifically on the interaction of plasma with cancer cells which include: (1) The role of plasma atmospheric reactive species (Reactive Oxygen Nitrogen Species; RONS); and (2) Plasma-based cancer treatments. The CAP used is generally produced by 2 (two) main types of devices as plasma sources, namely: (1) Plasma jets (PJ); and (2) Dielectric-barrier discharges (DBDs). The active pharmaceutical agent that plays a role in treatment using this method is Reactive Oxygen Nitrogen Species (RONS), which the layman knows as free radical compounds but this is where it becomes interesting. While the latest technique in the application of this technology is indirect plasma treatments, which use a medium containing plasma-activated water so that it no longer relies on the use of plasma sources during treatment and can penetrate better than the previous technique, namely Direct plasma treatments
... The main reason for this is the low cost of equipment for generation such discharges, the relative ease of their use and the compact design of plasma devices based on them [1][2][3]. This leads to a wide range of applications of such systems: various sources of radiation, in plasma assisted ignition [4,5], plasma synthesis of nanostructures [6][7][8], devices for surface treatment and coating [9], creation of miniature ionization detectors for analyzing the composition substances [10][11][12][13], the development of devices for plasma biomedicine [14][15][16] and many others. At present, various types of alternative current (AC) discharges * Author to whom any correspondence should be addressed. ...
Full-text available
In this work, on the basis of a unified model from the point of view of describing the gas discharge gap and electrodes for 2D geometry, numerical calculations were carried out to study various modes of direct current (DC) discharges in argon at atmospheric pressure. The influence of the cooling conditions of the electrodes on the current-voltage characteristic of the discharge is shown: the transition from normal glow to arc discharge with the formation of an abnormal glow mode and without it. It is shown that, depending on the cooling conditions of the electrodes, two forms of arc discharge can be obtained: with a diffuse or contracted current spot. In the low-current mode, current and voltage oscillations were obtained during the transition from the Townsend to the normal glow discharge.
... By allowing for hemostasis during surgery, electrosurgical units provide the surgeon with a better view of the surgical field, reduce the need for blood transfusion, curtail the length of anesthesia and surgery, and prevent local hematomas after surgery. [2][3][4][5][6] There are risks to using electrosurgery for the patient and surgical team. These risks include skin burns and disruption to the function of cardiac Abbreviations: AST, Association of Surgical Technologists; AORN, Association of periOperative Registered Nurses; AFPP, Association for PeriOperative Practice. ...
Background Electrosurgical units are used in over 80% of operations worldwide. The consequences of incorrect use of electrosurgical units for patients and the surgical team include skin burns, inhalation of electrosurgical smoke, fire, and disruption to the functioning of cardiac pacemakers. Training operating room personnel in the correct use of electrosurgical units and evaluating their performance plays a crucial role in making optimal use of the units and extending their lifetime, reducing occupational hazards for surgical teams, and enhancing the safety of patients. Therefore, the present study was done to investigate the effects of an educational intervention on electrosurgical units by operating room nurses. Methods In this quasi-experimental research, the performance of 100 operating room nurses concerning their application of electrosurgical units in 200 operations (100 before and 100 one month after the educational intervention) was observed and evaluated. The data collection instruments consisted of a Demographic Information Questionnaire, a surgery checklist, and the checklist for the use of electrosurgical units by operating room nurses. The content of the poster was based upon the standard principles of using electrosurgical units based on the guidelines by the Association of periOperative Registered Nurses (AORN), Association of Surgical Technologists (AST), and the Association for PeriOperative Practice (AFFP). Results The average age of the participating nurses were 31.540±6.772 years. Before (18.330±2.666) and after (20.820±3.400) the educational intervention, the results showed a statistically significant difference between the means and standard deviations of the scores of electrosurgical units by operating room nurses. Conclusion Introducing operating room nurses to the standard guidelines for applying electrosurgical units can improve the quality of services provided by the nurses, increase the safety of patients, and reduce occupational hazards. Thus, medical managers and policymakers should pay more attention to on-the-job training programs to improve the professional performance of operating room nurses in the use of electrosurgical units.
... Electrosurgical units (ESUs) are among the most frequently-used devices in surgeries since they conduct electricity through a surgical tool to the patient's body (1)(2)(3)(4). By creating hemostasis during surgery, ESUs enable the surgical team to make a surgical incision without causing bleeding and, thus, have a better view of the area under operation (1). ...
Full-text available
Abstract Background: Today, electrosurgical units are an indispensable part of surgeries. Yet, inappropriate application of this equipment can result in dire consequences for both the patient and the surgical team. Objectives: The present study aimed at developing the psychometric properties of a checklist to evaluate the application of electrosurgery units by operating room personnel. Methods: The present methodological study was performed in two stages: first, the items of the checklist were developed based on a literature review and search in relevant websites; and second, the psychometric properties of the checklist were measured using the methods to evaluate face, content, and construct validities. The reliability was measured through an assessment of the internal consistency of the checklist, based on the degree of inter-rater agreement. To assess construct validity, the researchers compared known groups; 40 surgeries were observed in two university hospitals in the intervention and control groups. Results: The content validity index (CVI) of all the items was over 0.79. The average CVI (S-CVI/Ave) of the checklist with 32 items was 0.97. The results of the Wilcoxon test showed that the posttest performance scores of the personnel in the intervention group were significantly higher than their pretest scores (P value = 0.005). The internal consistency (the Kuder-Richardson coefficient) of the checklist was 0.66. Conclusions: Due to the great importance of appropriate application of electrosurgery units, a reliable instrument is needed to assess personnel’s performance in this area. The results of the current study showed that the present instrument is sufficiently valid and reliable to evaluate the application of electrosurgical units by the operating room personnel. Keywords: Electrosurgical Units, Operating Room, Nursing, Checklist Development, Psychometric Evaluation
... Cold plasma has been studied as a next-generation cancer therapy [1][2][3]. Although cancer cells in vitro or tumorous tissues in vivo can be treated directly with cold plasma, the indirect cold plasma treatments have also been developed over the past years [4][5][6]. The indirect cold plasma treatments include the cold plasma-assisted immunotherapy [7] and the cold plasma-activated solutions (PAS) [8]. ...
Cold plasma-activated solution (PAS), particularly the cold plasma-activated medium (PAM), is a type of chemotherapy used in the cold plasma-based cancer treatment. Compared with the direct cold plasma treatment, PAM can be stored for a long time and can then be used without dependence on cold plasma sources or devices. Many in vitro and in vivo experiments have demonstrated anti-tumor effects of PAM against a variety of cancer cells. PAM contains a variety of reactive oxygen species (ROS), reactive nitrogen species (RNS), other cold plasma-activated species, and the generated compounds. These species either interact with the cellular membrane or the intracellular function to activate signal pathways and the expression of many genes. Several important signaling pathways are affected by PAM. The effectiveness of PAM has been demonstrated in animal studies using peritoneal metastasis model mice.
... Absolute measurements of the electron plasma density by means of the microwave scattering technique were proposed by Shashurin and demonstrated with several plasma objects including non-equilibrium atmospheric pressure plasma jets (APPJ), microdischarges used for electrosurgery, nanosecond repetitive pulsed discharges in air, and laser-induced plasmas [6] [7] [8] [9] [10] [11] [12] [13] . ...
This work proposes a novel method of Thomson microwave scattering for electron number density measurements of miniature plasmas at pressures < 10 Torr. This method is applied to determine electron number density in a positive column of glow discharge initiated at 5 Torr in air with a plasma column diameter of 3.4 mm. The Thomson Microwave Scattering(TMS) system measured the electron number density to be 3.36*10^10 cm^-3. The result obtained using the TMS system was validated against the measurements made using the well-known technique of microwave quarter-wave hairpin resonator. Measurements with the hairpin resonator yielded an electron number density of 2.07*10^10 cm^-3 providing adequate agreement with the TMS system.
... Currently, two options for plasma cancer treatment are available: direct and indirect ( Figure 1). Clinical trials of cancer treatments using non-thermal plasma (direct plasma treatments) are ongoing in Germany [6] and the USA [7]. Two different types of indirect plasma treatment have been proposed: plasma-assisted immunotherapy [8] and plasma-activated medium (PAM) [9,10]. ...
Full-text available
Non-thermal plasma represents a novel approach in cancer treatment. Both direct and indirect plasma treatments are available, with clinical trials of direct plasma treatment in progress. Indirect treatments involve chemotherapy (i.e., plasma-activated medium) and immunotherapy. Recent studies suggest that integrated plasma treatments could be an extremely effective approach to cancer therapy.
New techniques in plasma cutting cause far less collateral damage at incision surfaces and a higher surgical precision than previous methods.
Full-text available
We present an experimental method that makes possible in-situ measurements of the electron loss rate in arbitrary gas mixtures. A weakly ionized plasma is induced via resonant multiphoton ionization of trace amounts of nitric oxide seeded into the gas, and homodyne microwave scattering detection is used to study the dynamics of the electron loss mechanisms. Using this approach, the attachment rate for electrons to molecular oxygen in room temperature, atmospheric pressure air is determined. The measured 0.76 × 108 s-1 attachment rate is in very good agreement with predictions based on literature data.
Full-text available
This work presents a simplified model of microwave scattering during the avalanche ionization stage of laser breakdown and corresponding experimental results of microwave scattering from laser breakdown in room air. The model assumes and measurements confirm that the breakdown regime can be viewed as a point dipole scatterer of the microwave radiation and thus directly related to the time evolving number of electrons. The delay between the laser pulse and the rise of the microwave scattering signal is a direct measure of the avalanche ionization process.
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Recent progress in atmospheric plasmas has led to the creation of cold plasmas with ion temperature close to room temperature. This paper outlines recent progress in understanding of cold plasma physics as well as application of cold atmospheric plasma (CAP) in cancer therapy. Varieties of novel plasma diagnostic techniques were developed recently in a quest to understand physics of CAP. It was established that the streamer head charge is about 108 electrons, the electrical field in the head vicinity is about 107 V/m, and the electron density of the streamer column is about 1019 m−3. Both in-vitro and in-vivo studies of CAP action on cancer were performed. It was shown that the cold plasma application selectively eradicates cancer cells in-vitro without damaging normal cells and significantly reduces tumor size in-vivo. Studies indicate that the mechanism of action of cold plasma on cancer cells is related to generation of reactive oxygen species with possible induction of the apoptosis pathway. It is also shown that the cancer cells are more susceptible to the effects of CAP because a greater percentage of cells are in the S phase of the cell cycle.
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The use of a low energy, high peak intensity (>100 TW/cm{sup 2}) femtosecond laser pulse is investigated for guiding and control of a sub-microsecond high voltage discharge. Study of the laser induced plasma channel and measurements of the field required for breakdown in air and nitrogen at atmospheric pressure are presented. Direct imaging of the dynamics of the discharge breakdown shows effective laser guiding. The effectiveness of laser guiding is shown to be critically dependent on the laser focusing geometry, timing, and location relative to the electrodes.
Argon plasma coagulation (APC) is a thermoablative technique increasingly being used in endoscopy. Since its introduction, the flexible APC probe has been employed by endoscopists throughout the world. APC has helped change the endoscopic management of many gastrointestinal (GI) diseases, including hemorrhagic proctitis, watermelon stomach, bleeding peptic ulcer, and colonic varices. Endoscopists and surgeons are creatively combining standard and new electrosurgical techniques with APC. For instance,. APC used in combination with piecemeal polypectomy, endoscopic mucosal resection, balloon dilatation for strictures, and plasma welding of bleeding vessels after sclerotherapy injection are among the recent innovative techniques reported. Other emerging innovations using APC that are being considered include endoscopic en bloc resection of mucosal and submucosal tumors of the GI tract, endoscopic mucosal resection supplemented with APC for high-grade dysplasia and early GI cancers, endoscopic repair of anastomotic strictures, and welding GI fistula tracts. As such, endoscopists require more efficient and cost-effective multifunctional thermoablative probes. This review discusses the development and the potential application of dual-mode plasma endoscopic probes in fulfilling these emerging needs.
Plasma and injury properties produced by US Medical Innovations (USMI) elec­trosurgical systems were characterized using an explant pig’s liver samples. It was observed that plasma length, tissue temperature, and injury size increases with applied power increase. Transition from conventional to argon coagulation mode (<0.5 L/min) leads to redistribution of the discharge power over the larger tissue area causing abrupt decrease of injury depth and increase of eschar diameter. Flow rate is not a primary factor affecting the tissue temperature. The depth and diameter of injury was minimal for the case of hybrid argon plasma cut opera­tional mode.
A series of instant photographs of a discharge produced by the electrosurgical system SS-200E/Argon-2 by U.S. Medical Innovations is presented and analyzed.
Here is both a textbook for beginners and a handbook for specialists in plasma physics and gaseous electronics. The book contains much useful data: results of experiments and calculations, and reference data. It provides estimates of typical parameters and formulas in forms suitable for computations. Gas discharges of all important types are discussed: breakdown, glow, arc, spark and corona at radio frequency, microwave and optical frequences. The generation of plasma, and its application to high power gas lasers are treated in detail.
This review focuses on one of the fundamental phenomena that occur upon application of sufficiently strong electric fields to gases, namely the formation and propagation of ionization waves–streamers. The dynamics of streamers is controlled by strongly nonlinear coupling, in localized streamer tip regions, between enhanced (due to charge separation) electric field and ionization and transport of charged species in the enhanced field. Streamers appear in nature (as initial stages of sparks and lightning, as huge structures—sprites above thunderclouds), and are also found in numerous technological applications of electrical discharges. Here we discuss the fundamental physics of the guided streamer-like structures—plasma bullets which are produced in cold atmospheric-pressure plasma jets. Plasma bullets are guided ionization waves moving in a thin column of a jet of plasma forming gases (e.g., He or Ar) expanding into ambient air. In contrast to streamers in a free (unbounded) space that propagate in a stochastic manner and often branch, guided ionization waves are repetitive and highly-reproducible and propagate along the same path—the jet axis. This property of guided streamers, in comparison with streamers in a free space, enables many advanced time-resolved experimental studies of ionization waves with nanosecond precision. In particular, experimental studies on manipulation of streamers by external electric fields and streamer interactions are critically examined. This review also introduces the basic theories and recent advances on the experimental and computational studies of guided streamers, in particular related to the propagation dynamics of ionization waves and the various parameters of relevance to plasma streamers. This knowledge is very useful to optimize the efficacy of applications of plasma streamer discharges in various fields ranging from health care and medicine to materials science and nanotechnology.