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Difference between continuous wave and superpulse carbon dioxide laser in bladder surgery
DIFFERENCE
BETWEEN
SUPERPULSE
CARBON DIOXIDE
IN BLADDER
SURGERY*
WILLIAM
H. RATTNER,
SAMUEL
K. ROSEMBERG,
T. FULLER,
CONTINUOUS
WAVE AND
LASER
M.D. M.D.
PH.D.
From the Department Detroit, Michigan
of Urology,
Sinai Hospital
of Detroit,
ABSTRACT -Adult exteriorized rabbit bladders were treated with both continuous waue and rapid super-pulsed laser energy. A carbon dioxide laser was utilized in these studies. Time and power density were varied, and the effect in both acute and delayed preparations was noted. An additional group of animals treated with the carcinogen dibutylnitrosamine was studied in a similar manner. The depth of tissue ablated was monitored by the operating microscope and varied fi-om 1 to 2 mm., using the power-time grid we employed. Not only could the depth of destruction be controlled, but also re-epithelialization was apparent in one and one-half to three and one-half weeks after destruction Differences between superpulsed and continuous wave carbon dioxide laser energy are compared.
The use of laser energy as a surgical tool has been well documented in the literature. It has been useful in many areas of ophthalmologic, gynecologic, and otorhinologic surgery. l-5 It seemed most appealing to us as a method of applying a carefully controlled, predictable, and reproducible source of energy to the bladder. To explore its potential as an addition to the urologic procedures, the following experiment was structured. A SO-watt continuous wave and rapid super-pulsed laser was used on adult exteriorized rabbit bladders. The first portion of the experiment deals with the varying effects of this energy on the histologic structure of the bladder, the second portion with the changes consequent to the healing process, and the third portion with the effect of the laser on the bladder tumors induced with the carcinogen nitrosodibutylnitrosamine (DBN).6,7
*Supported by the Sinai Education Corp., Surgical Laboratory, Department of Research, pital of Detroit, and the National Institutes Carcinogens Laboratory.
264
the Laser Sinai Hosof Health
Material
and Methods
The laser used in this study was a continuous wave (CW) and rapid super-pulsed (RSP) laser. The continuous wave portion of the laser was variable from zero to 50 W of 10.6 p laser energy. The rapid superpulsed portion of the laser produces 4 kW. laser pulses with a repetition rate of 50 to 250 pulses per second and a pulse width of from 50 to 75 msec. Both modes were delivered through an articulated light guide and then into a Zeiss operating microscope. Visualization of the infrared beam was accomplished using a coaxial helium-neon laser beam. The laser energy was focused to a size of 0.03 cm.’ Initial studies were performed using a 14.03 inch focal length lens, yielding a selectable 2 and 7 mm. lesion. The preliminary observation and histopathologic evaluation led us to choose a 2 by 3 experimental matrix for CW and RSP power and times, i.e., energy. Individual lesions were chosen over broad-banded lesions because of the ability to quantify accurately the delivered energy. The continuous wave energy
UROLOGY
/ MARCH 1979 i
VOLUME
XIII,
NUMBER
3
TABLE
I.
Energy matrix in joules fw CW lesions
710
Watts
0.1 sec. 0.25 sec. 0.5 sec.
1 2.5 5
TABLE
II.
20 Watts 2 5 10
6.7
density of delivered energy (CW lesions)
Power (Watts)
Spot Size (mm.)
Power Density
10 20
2 2
323 W/cm.’ 474 W/cm.2
matrix is shown in Tables I and II. The rapid superpulse experimental matrix of repetition rate and pulse count is shown in Tables III and IV. The average delivered power is indicated and calculations of energy are based on these data. Twelve adult pigmented rabbits were anesthetized with intravenous pentobarbital under unsterile conditions. A vertical lower midline incision was then made, and the bladder identified, isolated, and exteriorized. A cystostomy was done, and the bladder mucosa was everted over a sterile sponge. Both RSP and CW carbon dioxide laser energy were focused on the bladder mucosa. As noted, a 2 by 3 matrix of power and time was generated, and the tissue exposed to varying energy levels. The lesions so produced were duplicated, one being removed immediately and the other left in situ to be studied when the animals were sacrificed at one, two, and four-week intervals to assess the healing process. The bladder was closed with 4-O chromic catgut suture, and the rest of the wound closed in one layer. The wound was TABLE III. Repetition rate - pulse count experimental matrix fw rapid superpulsed lesions
On-time (Sec.)
Power (Avg. ) (Watts) Repetition Rate (Pulses/See.) Pulse Count (Pulses) 176 88 36
UROLOGY
9
6.7
I76
1 0.5 0.2
9 4.5 1.8
88
2 1 0.4
13.4 6.7 2.75
/ MARCH 1979 / VOLUME XIII, NUMBER 3
IV.
Average power density delivered to tissue (SP lesions)
Power Repetition Rate (Watts) (Pulseshec.) 9
Power
On-time (Sec.)
TABLE
Spot Size Power Density (mm.) (W/cm.2)
176 6.7
2 2
290 216
cleansed with hydrogen peroxide and sealed with collodion. A second group of 12 rabbits previously treated by subcutaneous weekly injections of 400 mg. of nitrosodibutylnitrosamine for a period of twenty-eight weeks was treated with operator controlled times of 323 W/cm.’ CW and 290 W/cm.2 RSP laser energy. Results Histology of the normal adult rabbit bladder closely resembles the adult human bladder except for the thin muscular layers (Fig. 1A). After the application of 4 to 6 joules of carbon dioxide laser energy, a zone of acute coagulative necrosis is seen that affects the entire thickness of the mucosa in a focal area (Fig. 1B). At times, the epithelium appears detached or vesiculated with shrunken atrophic appearing cells. In this figure, we can see a well-defined shallow ulcer in which the base shows a thin layer of necrosis. Some edema is present beneath the burn site and the penetration appears to be 0.2 cm. after immediate removal. After one week, epithelial regrowth is apparent and begins at the periphery of the lesion (Fig. 1C). Acute inflammatory changes are noted in some sections and may reflect the unsterile nature of the preparation. At two weeks, there appears to be almost complete granulation tissue in which small blood vessels appear slightly prominent and fibroblastic nuclei are still evident. The results of the continuous wave energy matrix demonstrates the depth of the vaporization zone is proportional to the total energy imparted, that is, 5 joules delivered as 10 W for 0.5 sec. have the same vaporization zone as 5 joules delivered as 20 W for 0.25 set (Table I). However, the zone of coagulative necrosis and edema was greatest when longer times were employed. The results of the superpulse energy matrix demonstrated similar results, that is, depth of lesion is proportional to power density and on-time while coagulation necrosis proportional to on-time only (Table III). It is important to note that the on-time for the rapid super-pulse mode of operation was significantly
265
FIGURE 1. (A) Histology of normal adult rabbit bladder showing thin muscular layers. ’. (B) Acute coagulative necrosis affecting entire thickness of .$ bladder mucosa. (C) Epithelial .“‘& <+. $ .zf_, regeneration after one week I.,*&&/ ‘c-, *.: c beginning at periphery of lesion. (D) Epithelial dysplasia as early as -eight weeks. after injection of DBN.
longer than that of the continuous wave mode and that the resulting coagulation necrosis and edema was the same as in the continuous wave mode. Comparison between superpulse and continuous wave laser energies used in this portion of the study revealed the same amount of tissue vaporization and coagulation necrosis. In the tumor-bearing models (twenty-eight weeks of subcutaneous injection of nitrosodibutylnitrosamine), epithelial dysplasia was evident as early as eight weeks in 5 animals of dysplasia or frank (Fig. 1D); no evidence neoplastic changes was demonstrated in the remaining group of animals. Acute changes were similar to the control group, but in the twenty-five-day delay preparation the bladders treated with continuous wave as well as rapid super-pulsed laser energy showed vigorous and almost complete re-epithelialization despite the presence of severe inflammatory changes. Comment This type of destructive coagulating energy would appear to be an attractive method of control or eradication of at least superficial or multiple bladder tumors. Control of depth of destruction of tissue would appear to offer a significant advantage over electrocautery. In addition, it is apparent that epithelial regrowth is
266
rapid and tends to be morphologically normal. Absence of scar in the healing process would appear to be a desirable feature of laser therapy. With the ability of the rapid super-pulsed laser to vaporize comparable volumes of tissue with a lower average power density and yield similar zones of coagulation necrosis and edema, it is apparent that by using comparable power densities between the two modes, the resulting necrosis and edema would be reduced. The ontime would be reduced yielding a smaller zone of coagulation necrosis and edema. 29279 Franklin Hills Dr. Southfield, Michigan 48034 (DR. ROSEMBERG) References 1. Bellina JH: Carbon dioxide laser in gynecology, Obstet. Gynecol. Annul. 6: 371 (1977). 2. Staehler G, et al: Endoscony in experimental urology -. using_ an Argon laser, Endoscopy 8: 1 ii976). _ 3. Landers MB, III: The current status of laser wane in ophthalmology, Ann. N.Y. Acad. Sci. 267: 239 (1976). 4. Goldman L: Laser medical instrumentation, Med. Instrumen. 10: 125 (1976). 5. Fuller T, and Beckman H: Carbon dioxide laser surgery of the eye, Int. Symp. Laser Surg., Tel Aviv, Israel, 1976. 6. Cohen AE: Cystoscopy of chemically induced bladder neoplasms in rabbits administered the carcinogen dibutylnitrosamine, Invest. Urol. 12: 262 (1976). 7. Jacobs JB; Chemically induced smooth muscle tumors of the mouse urinary bladder, Cancer Res. 36: 2396 (1976).
UROLOGY
/
MARCH 1979
/
VOLUME XIII,
NUMBER3
BETWEEN
SUPERPULSE
CARBON DIOXIDE
IN BLADDER
SURGERY*
WILLIAM
H. RATTNER,
SAMUEL
K. ROSEMBERG,
T. FULLER,
CONTINUOUS
WAVE AND
LASER
M.D. M.D.
PH.D.
From the Department Detroit, Michigan
of Urology,
Sinai Hospital
of Detroit,
ABSTRACT -Adult exteriorized rabbit bladders were treated with both continuous waue and rapid super-pulsed laser energy. A carbon dioxide laser was utilized in these studies. Time and power density were varied, and the effect in both acute and delayed preparations was noted. An additional group of animals treated with the carcinogen dibutylnitrosamine was studied in a similar manner. The depth of tissue ablated was monitored by the operating microscope and varied fi-om 1 to 2 mm., using the power-time grid we employed. Not only could the depth of destruction be controlled, but also re-epithelialization was apparent in one and one-half to three and one-half weeks after destruction Differences between superpulsed and continuous wave carbon dioxide laser energy are compared.
The use of laser energy as a surgical tool has been well documented in the literature. It has been useful in many areas of ophthalmologic, gynecologic, and otorhinologic surgery. l-5 It seemed most appealing to us as a method of applying a carefully controlled, predictable, and reproducible source of energy to the bladder. To explore its potential as an addition to the urologic procedures, the following experiment was structured. A SO-watt continuous wave and rapid super-pulsed laser was used on adult exteriorized rabbit bladders. The first portion of the experiment deals with the varying effects of this energy on the histologic structure of the bladder, the second portion with the changes consequent to the healing process, and the third portion with the effect of the laser on the bladder tumors induced with the carcinogen nitrosodibutylnitrosamine (DBN).6,7
*Supported by the Sinai Education Corp., Surgical Laboratory, Department of Research, pital of Detroit, and the National Institutes Carcinogens Laboratory.
264
the Laser Sinai Hosof Health
Material
and Methods
The laser used in this study was a continuous wave (CW) and rapid super-pulsed (RSP) laser. The continuous wave portion of the laser was variable from zero to 50 W of 10.6 p laser energy. The rapid superpulsed portion of the laser produces 4 kW. laser pulses with a repetition rate of 50 to 250 pulses per second and a pulse width of from 50 to 75 msec. Both modes were delivered through an articulated light guide and then into a Zeiss operating microscope. Visualization of the infrared beam was accomplished using a coaxial helium-neon laser beam. The laser energy was focused to a size of 0.03 cm.’ Initial studies were performed using a 14.03 inch focal length lens, yielding a selectable 2 and 7 mm. lesion. The preliminary observation and histopathologic evaluation led us to choose a 2 by 3 experimental matrix for CW and RSP power and times, i.e., energy. Individual lesions were chosen over broad-banded lesions because of the ability to quantify accurately the delivered energy. The continuous wave energy
UROLOGY
/ MARCH 1979 i
VOLUME
XIII,
NUMBER
3
TABLE
I.
Energy matrix in joules fw CW lesions
710
Watts
0.1 sec. 0.25 sec. 0.5 sec.
1 2.5 5
TABLE
II.
20 Watts 2 5 10
6.7
density of delivered energy (CW lesions)
Power (Watts)
Spot Size (mm.)
Power Density
10 20
2 2
323 W/cm.’ 474 W/cm.2
matrix is shown in Tables I and II. The rapid superpulse experimental matrix of repetition rate and pulse count is shown in Tables III and IV. The average delivered power is indicated and calculations of energy are based on these data. Twelve adult pigmented rabbits were anesthetized with intravenous pentobarbital under unsterile conditions. A vertical lower midline incision was then made, and the bladder identified, isolated, and exteriorized. A cystostomy was done, and the bladder mucosa was everted over a sterile sponge. Both RSP and CW carbon dioxide laser energy were focused on the bladder mucosa. As noted, a 2 by 3 matrix of power and time was generated, and the tissue exposed to varying energy levels. The lesions so produced were duplicated, one being removed immediately and the other left in situ to be studied when the animals were sacrificed at one, two, and four-week intervals to assess the healing process. The bladder was closed with 4-O chromic catgut suture, and the rest of the wound closed in one layer. The wound was TABLE III. Repetition rate - pulse count experimental matrix fw rapid superpulsed lesions
On-time (Sec.)
Power (Avg. ) (Watts) Repetition Rate (Pulses/See.) Pulse Count (Pulses) 176 88 36
UROLOGY
9
6.7
I76
1 0.5 0.2
9 4.5 1.8
88
2 1 0.4
13.4 6.7 2.75
/ MARCH 1979 / VOLUME XIII, NUMBER 3
IV.
Average power density delivered to tissue (SP lesions)
Power Repetition Rate (Watts) (Pulseshec.) 9
Power
On-time (Sec.)
TABLE
Spot Size Power Density (mm.) (W/cm.2)
176 6.7
2 2
290 216
cleansed with hydrogen peroxide and sealed with collodion. A second group of 12 rabbits previously treated by subcutaneous weekly injections of 400 mg. of nitrosodibutylnitrosamine for a period of twenty-eight weeks was treated with operator controlled times of 323 W/cm.’ CW and 290 W/cm.2 RSP laser energy. Results Histology of the normal adult rabbit bladder closely resembles the adult human bladder except for the thin muscular layers (Fig. 1A). After the application of 4 to 6 joules of carbon dioxide laser energy, a zone of acute coagulative necrosis is seen that affects the entire thickness of the mucosa in a focal area (Fig. 1B). At times, the epithelium appears detached or vesiculated with shrunken atrophic appearing cells. In this figure, we can see a well-defined shallow ulcer in which the base shows a thin layer of necrosis. Some edema is present beneath the burn site and the penetration appears to be 0.2 cm. after immediate removal. After one week, epithelial regrowth is apparent and begins at the periphery of the lesion (Fig. 1C). Acute inflammatory changes are noted in some sections and may reflect the unsterile nature of the preparation. At two weeks, there appears to be almost complete granulation tissue in which small blood vessels appear slightly prominent and fibroblastic nuclei are still evident. The results of the continuous wave energy matrix demonstrates the depth of the vaporization zone is proportional to the total energy imparted, that is, 5 joules delivered as 10 W for 0.5 sec. have the same vaporization zone as 5 joules delivered as 20 W for 0.25 set (Table I). However, the zone of coagulative necrosis and edema was greatest when longer times were employed. The results of the superpulse energy matrix demonstrated similar results, that is, depth of lesion is proportional to power density and on-time while coagulation necrosis proportional to on-time only (Table III). It is important to note that the on-time for the rapid super-pulse mode of operation was significantly
265
FIGURE 1. (A) Histology of normal adult rabbit bladder showing thin muscular layers. ’. (B) Acute coagulative necrosis affecting entire thickness of .$ bladder mucosa. (C) Epithelial .“‘& <+. $ .zf_, regeneration after one week I.,*&&/ ‘c-, *.: c beginning at periphery of lesion. (D) Epithelial dysplasia as early as -eight weeks. after injection of DBN.
longer than that of the continuous wave mode and that the resulting coagulation necrosis and edema was the same as in the continuous wave mode. Comparison between superpulse and continuous wave laser energies used in this portion of the study revealed the same amount of tissue vaporization and coagulation necrosis. In the tumor-bearing models (twenty-eight weeks of subcutaneous injection of nitrosodibutylnitrosamine), epithelial dysplasia was evident as early as eight weeks in 5 animals of dysplasia or frank (Fig. 1D); no evidence neoplastic changes was demonstrated in the remaining group of animals. Acute changes were similar to the control group, but in the twenty-five-day delay preparation the bladders treated with continuous wave as well as rapid super-pulsed laser energy showed vigorous and almost complete re-epithelialization despite the presence of severe inflammatory changes. Comment This type of destructive coagulating energy would appear to be an attractive method of control or eradication of at least superficial or multiple bladder tumors. Control of depth of destruction of tissue would appear to offer a significant advantage over electrocautery. In addition, it is apparent that epithelial regrowth is
266
rapid and tends to be morphologically normal. Absence of scar in the healing process would appear to be a desirable feature of laser therapy. With the ability of the rapid super-pulsed laser to vaporize comparable volumes of tissue with a lower average power density and yield similar zones of coagulation necrosis and edema, it is apparent that by using comparable power densities between the two modes, the resulting necrosis and edema would be reduced. The ontime would be reduced yielding a smaller zone of coagulation necrosis and edema. 29279 Franklin Hills Dr. Southfield, Michigan 48034 (DR. ROSEMBERG) References 1. Bellina JH: Carbon dioxide laser in gynecology, Obstet. Gynecol. Annul. 6: 371 (1977). 2. Staehler G, et al: Endoscony in experimental urology -. using_ an Argon laser, Endoscopy 8: 1 ii976). _ 3. Landers MB, III: The current status of laser wane in ophthalmology, Ann. N.Y. Acad. Sci. 267: 239 (1976). 4. Goldman L: Laser medical instrumentation, Med. Instrumen. 10: 125 (1976). 5. Fuller T, and Beckman H: Carbon dioxide laser surgery of the eye, Int. Symp. Laser Surg., Tel Aviv, Israel, 1976. 6. Cohen AE: Cystoscopy of chemically induced bladder neoplasms in rabbits administered the carcinogen dibutylnitrosamine, Invest. Urol. 12: 262 (1976). 7. Jacobs JB; Chemically induced smooth muscle tumors of the mouse urinary bladder, Cancer Res. 36: 2396 (1976).
UROLOGY
/
MARCH 1979
/
VOLUME XIII,
NUMBER3