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Measurement of the efficiency of tissue removal with the cavitron ultrasonic surgical aspirator and the comparison with a new motor-driven probe
Ultrasound in Med. & Biol. Vol. 11, No. 3, pp. L533-L540. 0301-5629/85 $3.00 + .OO Printed in the U.S.A. Copyright (cl 1985 Pergamon Press Ltd. All rights reserved.
LETTERS TO THE EDITOR. MEASUREMENT OF THE EFFICIENCY OF TISSUE REMOVAL WITH THE CAVITRON* ULTRASONIC SURGICAL ASPIRATOR AND THE COMPARISON WITH A NEW MOTOR-DRIVEN PROBE. Sir, In recent years the Cavitron Ultrasonic Surgical Aspirator, which is produced by the Cooper Medical Corporation, has become a useful surgical tool in neurosurgery (Goldsmith 1983, Flamm et al 1979) and in general surgery as well (e.g. Hodgson et al 1982, Addonizio et al 1984).
In fact,
the Cavitron is a vibrating suction device which works on the principle of magnetostriction. is 2.1 cm.
The surgical handpiece is 30 cm long and its diameter
The handpiece is constructed with a water-cooled jacket inside
which magnetostrictive transducer is attached by a connecting body to a coneshaped titanium velocity transformer.
This velocity transformer is a hollow
tube of length 6.4 cm. inner diameter 1.85 mm and outer diameter 2.15 mm at the working end, through which the removed ti'ssueis sucked away by a vacuum pump (suction pressure of about 60 cm Hg).
The maximum vibration amplitude
is about 300 microns and the operation frequency is 23 KHz. is also equipped with an irrigation system.
The Cavitron
The rate of flow of sterile
irrigating solution into the surgical site can vary from approximately 1 to 50 c.c./min.
The irrigated sterile solution cleans the surgical field and
assists in the removal of tissue fragments.
The most prominent advantages
of using this surgical tool are that (1) blood vessels can be spared so that haemorrhage is minimized.
(2) Surgeons can feel tactile feedback from
different types of tissue in terms of different water content; (3) No electrical hazard to patients arises with this surgical method.
However,
its rate of tissue removal may be much lower than that with standard surgical tools, like surgical blades, or electrosurgicalunits.
And the
weight of this tool may also be a burden to the surgeon in prolonged surgery.
*
Cavitron Ultrasound Surgical Aspirator CUSATM is the trade mark of Cavitron Lasersonics division of Cavitron Corporation, Stamford, Connecticut 06904, U.S.A. L533
Letters
L534
to the Editor
Although the Cavitron has become a popular surgical tool, as far as we know,there are no quantitative reports of its efficiency at removing soft tissues.
We have carried out measurements with the Cavitron in the
Aberdeen Royal Infirmary.
We have quantified its efficiency in terms of
the mass of tissue removed from ox-liver per unit time. shown in figure 1.
The results are
The amount of removal is linear with time and approxi-
mately 7.4 grams per minute is removed when the Cavitron is operated at full power with maximum suction pressure.
Reside doing measurements with the Cavitron, we have developed a motor-driven probe equipped with an aspiration system and an irrigation system.
A hollow stainless steel tube is coupled to the shaft of a high
speed motor by an off-centre cam.
Suction is applied through the hollow
tip and the irrigation is applied through the space between the vibrating tip and the outer protective sleeve.
During the measurements of efficiency
of removing tissue with this motor-driven probe the motor was operated at 15,000 rpm and the suction pressure was normally kept at 60 cm Hg. vibration amplitude was about lmm.
The
In these series of experiments we have
found that the rate of removal strongly depends on the area of the vibrating tip and on the suction pressure.
The results are plotted in the figure 1.
We have observed that the larger blood vessels are also spared by this motordriven probe.
Picture 1 and 2 show the comparison between the ox-liver
after the Cavitron was applied to one sample and that after the motor-driven probe applied to another. In conclusion, when the motor-driven probe with a narrow tip is applied to ox-liver tissue, its efficiency of tissue removal is comparable to that of the Cavitron Ultrasonic Surgical Aspirator.
Sparing of larger
blood vessels can also be achieved with the motor-driven probe.
Our results
also show that vibration amplitude is at least as important as the vibration frequency in efficient removal of soft tissues.
On the other hand, magneto-
strictive transducers usually suffer from severe power loss and the production costs of the Cavitron is relatively high.
Moreover, the length of the velocity
transformer in the magnetostrictive transducer is of half-wavelength of the ultrasound wave propagating in that material in order to amplify the displacement amplitude, but the vibration tip of this motor-driven probe can be
Letters
L535
to the Editor
Picture 1. The photograph shows the piece of ox-liver tissue has been removed by the CUSA Cavitron
Picture 2. The photograph shows two pieces tissue has been removed by the motor-driven laboratory.
from which
of ox-liver from which device developed in our
Letters to the Editor
L536
Fiqure
88
1
70 -
60-
50-
tB-
38-
20-
10 -
)
%l
2
4
6
8
10
VfbrutfonThe
Figure 1.
The mass of ox-liver removal is plotted against the duration of applying vibration.
(+I :
measurements with the Cavitron which is operated at full power with maximum suction pressure (60 cm Hg)
(0) :
measurements with a motor-driven vibrating hollow tip of outer diameter 3mm.
The thickness of the wall is
is about 0.13 mm. suction pressure is kept at 60 cm Hg and the motor is operated at 15,000 rpm.
The data shown
in the graph are the averaged values from three sets of measurements.
#w-) :
same experimental conditions as that of (0) except that the thickness of the wall is relatively larger, 0.4mm.
(0) :
same experimental conditions as that of (0) except that the suction pressure is kept at 20 cm Hg and its wall is relatively thicker.
Letters
to the Editor
of any length to suit surgeons' purposes.
We are intending to further improve
the mechanical design of our probe and it is hoped to achieve even higher efficiency. Yours etc., K.K.Chan, D.J.Watmough, and K.Moir
D.T.Hope
Department of Bio-Medical Physics
Consultant in Neurosurgery
and Bio-Engineering
Aberdeen Royal Infirmary
University of Aberdeen
Aberdeen AB9 2ZD
Foresterhill
United Kingdom
Aberdeen AB9 2ZD United Kingdom References Addonizio J.C., Choudhury, M.S., Sayegh N, Chopp, R.T. (1984) "Cavitron Ultrasonic Surgical Aspirator, Applications in Urologic Surgery" in Urology 23, 417-420. Flamm, E.S., Ransohoff, J (1979) "Ultrasonic Aspiration of Intracranial Tumours" in the paper presented at the 47th Annual meeting of the American Association of Neurological Surgeons, April, 1979. Goldsmith, M.F. (1983) "Ultrasonic Device Wins Neurosurgeons Praise" in JAMA Dee 23130, 1983 vol. 250, No. 24, p.3270. Hodgson, J.B., McElhinney, A.J. (1982) "Ultrasonic Partial Splenectomy" in Surgery vol. 91, No. 3, 346-348.
JOHANN CHRISTIAN DOPPLER. Sir: In the course of my researches into the works of Christian Doppler I have chanced upon an article entitled 'Johann Christian Doppler and his effect - a brief history' by Professor D.N. White, published in your journal in 1982 (5). The author starts out by stating that little is known about Doppler as a person and then, as though to prove this, makes a number of factual errors within half a page of biography. In doing so, he is in excellent company, havins inherited some error5 ZLOIO ilormaliy impeccable sources. Since I know your journal to be justifiably proud of its reputation for accuracy, may I be allowed to set the historical record straight?
L537
LETTERS TO THE EDITOR. MEASUREMENT OF THE EFFICIENCY OF TISSUE REMOVAL WITH THE CAVITRON* ULTRASONIC SURGICAL ASPIRATOR AND THE COMPARISON WITH A NEW MOTOR-DRIVEN PROBE. Sir, In recent years the Cavitron Ultrasonic Surgical Aspirator, which is produced by the Cooper Medical Corporation, has become a useful surgical tool in neurosurgery (Goldsmith 1983, Flamm et al 1979) and in general surgery as well (e.g. Hodgson et al 1982, Addonizio et al 1984).
In fact,
the Cavitron is a vibrating suction device which works on the principle of magnetostriction. is 2.1 cm.
The surgical handpiece is 30 cm long and its diameter
The handpiece is constructed with a water-cooled jacket inside
which magnetostrictive transducer is attached by a connecting body to a coneshaped titanium velocity transformer.
This velocity transformer is a hollow
tube of length 6.4 cm. inner diameter 1.85 mm and outer diameter 2.15 mm at the working end, through which the removed ti'ssueis sucked away by a vacuum pump (suction pressure of about 60 cm Hg).
The maximum vibration amplitude
is about 300 microns and the operation frequency is 23 KHz. is also equipped with an irrigation system.
The Cavitron
The rate of flow of sterile
irrigating solution into the surgical site can vary from approximately 1 to 50 c.c./min.
The irrigated sterile solution cleans the surgical field and
assists in the removal of tissue fragments.
The most prominent advantages
of using this surgical tool are that (1) blood vessels can be spared so that haemorrhage is minimized.
(2) Surgeons can feel tactile feedback from
different types of tissue in terms of different water content; (3) No electrical hazard to patients arises with this surgical method.
However,
its rate of tissue removal may be much lower than that with standard surgical tools, like surgical blades, or electrosurgicalunits.
And the
weight of this tool may also be a burden to the surgeon in prolonged surgery.
*
Cavitron Ultrasound Surgical Aspirator CUSATM is the trade mark of Cavitron Lasersonics division of Cavitron Corporation, Stamford, Connecticut 06904, U.S.A. L533
Letters
L534
to the Editor
Although the Cavitron has become a popular surgical tool, as far as we know,there are no quantitative reports of its efficiency at removing soft tissues.
We have carried out measurements with the Cavitron in the
Aberdeen Royal Infirmary.
We have quantified its efficiency in terms of
the mass of tissue removed from ox-liver per unit time. shown in figure 1.
The results are
The amount of removal is linear with time and approxi-
mately 7.4 grams per minute is removed when the Cavitron is operated at full power with maximum suction pressure.
Reside doing measurements with the Cavitron, we have developed a motor-driven probe equipped with an aspiration system and an irrigation system.
A hollow stainless steel tube is coupled to the shaft of a high
speed motor by an off-centre cam.
Suction is applied through the hollow
tip and the irrigation is applied through the space between the vibrating tip and the outer protective sleeve.
During the measurements of efficiency
of removing tissue with this motor-driven probe the motor was operated at 15,000 rpm and the suction pressure was normally kept at 60 cm Hg. vibration amplitude was about lmm.
The
In these series of experiments we have
found that the rate of removal strongly depends on the area of the vibrating tip and on the suction pressure.
The results are plotted in the figure 1.
We have observed that the larger blood vessels are also spared by this motordriven probe.
Picture 1 and 2 show the comparison between the ox-liver
after the Cavitron was applied to one sample and that after the motor-driven probe applied to another. In conclusion, when the motor-driven probe with a narrow tip is applied to ox-liver tissue, its efficiency of tissue removal is comparable to that of the Cavitron Ultrasonic Surgical Aspirator.
Sparing of larger
blood vessels can also be achieved with the motor-driven probe.
Our results
also show that vibration amplitude is at least as important as the vibration frequency in efficient removal of soft tissues.
On the other hand, magneto-
strictive transducers usually suffer from severe power loss and the production costs of the Cavitron is relatively high.
Moreover, the length of the velocity
transformer in the magnetostrictive transducer is of half-wavelength of the ultrasound wave propagating in that material in order to amplify the displacement amplitude, but the vibration tip of this motor-driven probe can be
Letters
L535
to the Editor
Picture 1. The photograph shows the piece of ox-liver tissue has been removed by the CUSA Cavitron
Picture 2. The photograph shows two pieces tissue has been removed by the motor-driven laboratory.
from which
of ox-liver from which device developed in our
Letters to the Editor
L536
Fiqure
88
1
70 -
60-
50-
tB-
38-
20-
10 -
)
%l
2
4
6
8
10
VfbrutfonThe
Figure 1.
The mass of ox-liver removal is plotted against the duration of applying vibration.
(+I :
measurements with the Cavitron which is operated at full power with maximum suction pressure (60 cm Hg)
(0) :
measurements with a motor-driven vibrating hollow tip of outer diameter 3mm.
The thickness of the wall is
is about 0.13 mm. suction pressure is kept at 60 cm Hg and the motor is operated at 15,000 rpm.
The data shown
in the graph are the averaged values from three sets of measurements.
#w-) :
same experimental conditions as that of (0) except that the thickness of the wall is relatively larger, 0.4mm.
(0) :
same experimental conditions as that of (0) except that the suction pressure is kept at 20 cm Hg and its wall is relatively thicker.
Letters
to the Editor
of any length to suit surgeons' purposes.
We are intending to further improve
the mechanical design of our probe and it is hoped to achieve even higher efficiency. Yours etc., K.K.Chan, D.J.Watmough, and K.Moir
D.T.Hope
Department of Bio-Medical Physics
Consultant in Neurosurgery
and Bio-Engineering
Aberdeen Royal Infirmary
University of Aberdeen
Aberdeen AB9 2ZD
Foresterhill
United Kingdom
Aberdeen AB9 2ZD United Kingdom References Addonizio J.C., Choudhury, M.S., Sayegh N, Chopp, R.T. (1984) "Cavitron Ultrasonic Surgical Aspirator, Applications in Urologic Surgery" in Urology 23, 417-420. Flamm, E.S., Ransohoff, J (1979) "Ultrasonic Aspiration of Intracranial Tumours" in the paper presented at the 47th Annual meeting of the American Association of Neurological Surgeons, April, 1979. Goldsmith, M.F. (1983) "Ultrasonic Device Wins Neurosurgeons Praise" in JAMA Dee 23130, 1983 vol. 250, No. 24, p.3270. Hodgson, J.B., McElhinney, A.J. (1982) "Ultrasonic Partial Splenectomy" in Surgery vol. 91, No. 3, 346-348.
JOHANN CHRISTIAN DOPPLER. Sir: In the course of my researches into the works of Christian Doppler I have chanced upon an article entitled 'Johann Christian Doppler and his effect - a brief history' by Professor D.N. White, published in your journal in 1982 (5). The author starts out by stating that little is known about Doppler as a person and then, as though to prove this, makes a number of factual errors within half a page of biography. In doing so, he is in excellent company, havins inherited some error5 ZLOIO ilormaliy impeccable sources. Since I know your journal to be justifiably proud of its reputation for accuracy, may I be allowed to set the historical record straight?
L537