Abstract:
An ultrasonic surgical apparatus comprises a treatment device with an ultrasonic transducer driven to generate ultrasonic vibration, an operation device outputting a signal commanding the transducer to start driving in response to an operator&#39;s operation, and a driver driving the transducer by supplying current thereto. The apparatus further comprises a controller controlling the driver. The controller controls the driver using selectively a first output control pattern and a second output control pattern. The first output control pattern is set to supply the current of a first current value under control of constant current control in response to the signal from the operation device, while the second output control pattern is set to supply the current of a second current value in response to the signal from the operation device and then the current is reduced in amount as the time counted from starting the supply elapses.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present application relates to and incorporates by reference Japanese Patent application No. 2004-184152 filed on Jun. 22, 2004.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Technical Field of the Invention  
         [0003]     This invention relates to an ultrasonic surgical apparatus for effecting treatment by ultrasonic vibration.  
         [0004]     2. Related Art  
         [0005]     Ultrasonic coagulation and incision apparatuses, one type of apparatuses utilizing ultrasonic vibration and constituting surgical devices, have been used. The ultrasonic coagulation and incision apparatuses comprise an ultrasonic probe and a holder which is driven for opening and closing of the ultrasonic probe. Coagulation and incision of living tissues have thus been carried out by giving ultrasonic vibration to the ultrasonic probe in the state where the living tissues are held between the ultrasonic probe and the holder.  
         [0006]     In such a conventional ultrasonic coagulation and incision apparatus, current control for maintaining the amplitude of an ultrasonic probe at a constant level, has been performed when ultrasonic waves are emitted.  
         [0007]     The ultrasonic coagulation and incision apparatuses have been used in two ways of manipulations. One is to effect treatment to living tissues with comparatively high ultrasonic output, in which incision is carried out immediately after coagulation of the living tissues. Therefore, before proceeding to incision, there has been no ample time and thus it has been difficult to visually confirm as to whether or not the coagulation satisfactorily took place.  
         [0008]     The other is to effect treatment to living tissues with comparatively low ultrasonic output of a level which would not incise the living tissues. In this manipulation, coagulation of living tissues can be visually confirmed, however, a problem has been that more time was required for the coagulation due to the low ultrasonic output.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention has been made in view of the circumstances described above, and has as its object to provide an ultrasonic surgical apparatus which reliably enables coagulation of living tissues in a short time.  
         [0010]     According to the present invention, as one aspect, there is provided an ultrasonic surgical apparatus comprising: a treatment device with an ultrasonic transducer driven to generate ultrasonic vibration in response to supply of current; an operation device outputting a signal commanding the ultrasonic transducer to start driving in response to an operator&#39;s operation; a driver driving the ultrasonic transducer by supplying the current thereto; and a controller controlling the driver to supply the current so that the current of a predetermined amount is supplied in response to the signal outputted from the operation device and then the current is reduced in amount as a time counted from starting the supply elapses.  
         [0011]     Preferably, in the ultrasonic surgical apparatus, the controller is configured to control the driver based on an output control pattern with which the current of the predetermined amount is supplied in response to the signal outputted from the operation device and then the current is reduced in amount as the time counted from starting the supply elapses.  
         [0012]     Still preferably, in the ultrasonic surgical apparatus according to the preferable configuration, the controller is configured to control the driver using selectively a first output control pattern and a second output control pattern, the first output control pattern being set to supply the current of a first current value under control of constant current control in response to the signal from the operation device and the second output control pattern being set to supply the current of a second current value in response to the signal outputted from the operation device and then the current is reduced in amount as the time counted from starting the supply elapses. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     In the accompanying drawings:  
         [0014]      FIG. 1  is a block diagram showing the configuration of an ultrasonic surgical apparatus according to a first embodiment of the present invention;  
         [0015]      FIG. 2  is an enlarged view of a treatment portion of the device;  
         [0016]      FIG. 3  is a block diagram showing the configuration of a control drive unit;  
         [0017]      FIG. 4  is a graph explaining a first output control pattern in a transducer drive circuit;  
         [0018]      FIG. 5  is a graph explaining a second output control pattern in a transducer drive circuit;  
         [0019]      FIG. 6  is a graph explaining a modification of the second output control pattern in a transducer drive circuit;  
         [0020]      FIG. 7  is a graph showing temperature changes of living tissues at the time of effecting ultrasonic treatment with respect to the output control patterns shown in  FIGS. 4 and 5 ;  
         [0021]      FIG. 8  is a graph explaining a modification of an output control pattern;  
         [0022]      FIG. 9  is a graph explaining another modification of an output control pattern;  
         [0023]      FIG. 10  is a graph explaining still another modification of an output control pattern;  
         [0024]      FIG. 11  is a graph explaining still another modification of an output control pattern;  
         [0025]      FIG. 12  is a block diagram showing the configuration of a control drive unit according to a second embodiment of the present invention;  
         [0026]      FIG. 13  is a rough flowchart explaining selection of control modes (output control patterns) implemented in the first embodiment;  
         [0027]      FIGS. 14A and 14B  are illustrations explaining coagulation and incision, respectively, of living tissues; and  
         [0028]      FIG. 15  is a rough flowchart explaining “being enable” and “being disenable” for ultrasonic driving based on monitoring of impedance, which is implemented in the second embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0029]     Various embodiments of the ultrasonic surgical apparatus according to the present invention are described hereinafter with referenced to the accompanying drawings.  
       FIRST EMBODIMENT  
       [0030]     The ultrasonic surgical apparatus according to a first embodiment is described with reference to FIGS.  1  to  7 .  
         [0031]     As shown in  FIG. 1 , the ultrasonic surgical apparatus according to the first embodiment comprises a control drive unit  1  as a device body, a hand piece  2 , and a foot switch (FSW)  3  as switching means. The hand piece  2  and the foot switch  3  are physically and electrically connected to the control drive unit  1 .  
         [0032]     The hand piece  2  is provided with a treatment portion  5  which is disposed at the tip of an elongated and cylindrical sheath  4 , and with a handling portion  6  which is disposed at the base of the sheath  4 . It should be noted that, in the present embodiment, the end of the sheath  4 , which is located near the control drive unit  1  is referred to as a base or base portion (or base side), and the opposite end of the sheath  4  is referred to as a tip or a tip portion (or tip side).  
         [0033]     The handling portion  6  comprises a case  7  for accommodating an ultrasonic transducer UT which generates ultrasonic vibration, and a handle  8  disposed at the case  7 . An operator can operate the treatment portion  5  by operating the handle  8 .  
         [0034]     The sheath  4  is provided therein with a probe  9  for transferring ultrasonic vibration from the ultrasonic transducer UT to the treatment portion  5 . The tip portion of the probe  9  is exposed outside from the tip of the sheath  4 .  
         [0035]     As shown in  FIG. 2 , the probe  9  is provided with a holder  10  which is driven for opening and closing of an exposed tip portion  9   a  of the probe  9 . The holder  10  is linked to the tip of the sheath  4  so as to be rotatable about a rotating pin  11 . Upon operation of the handle  8  by an operator, the holder  10  is driven for opening and closing of the exposed tip portion  9   a . As a result, living tissues can be held between the probe  9  and the holder  10 .  
         [0036]     The foot switch  3  comprises a switch body  12 , and two operation pedals  13  and  14  set up on a floor or the like, which are independently operated from the switch body  12 .  
         [0037]     A control panel  15  is provided at the front face of the control drive unit  1 . The control panel  15  is provided with a power switch  16 , an operation display panel  17 , and a connecting portion  18 . One end of a cable  19  is linked to the handling portion  6  of the hand piece  2 . A connector  20 , which is disposed at the other end of the cable  19 , is detachably connected to the connecting portion  18  mentioned above.  
         [0038]     The operation display panel  17  is provided with a setting device  21  for setting a pattern for output control (hereinafter referred to “output control pattern”) of ultrasonic waves when effecting ultrasonic treatment; a first display  22   a  for indicating a first output control pattern set at the setting device  21 ; and a second display  22   b  for indicating a second output control pattern set at the setting device  21 .  
         [0039]     As shown in  FIG. 3 , an transducer drive circuit  23  is incorporated into the control drive unit  1 . In the present embodiment, the drive circuit  23  is configured to operate by employing a PLL control system as a resonance tracking system, and employing a current control system as an amplitude control system.  
         [0040]     Particularly, the transducer drive circuit  23  comprises an output circuit having a phase-locked loop (PLL) circuit  24 , a voltage control amplifier (VCA)  25  serving as an adder, a power amplifier (AMP)  26  which produces current for imparting power to an ultrasonic transducer, voltage/current detector (DET)  27  and an output transformer  28 , which are connected in series in this order. The hand piece  2  is connected to an output port of the output transformer  28  through the connecting cable  19 . The transducer drive circuit  23  is separated from the hand piece  2  in a fashion that a direct current is not passed therebetween.  
         [0041]     The phase-locked loop circuit  24  is a circuit which tracks the resonant frequency of an ultrasonic transducer and drives it at the resonance frequency. The voltage/current detector (DET)  27  is connected to the phase-locked loop circuit  24 . Further, the voltage/current detector (DET)  27  includes a circuit for detecting phase signals of voltage and current for performing a PLL operation, or for detecting the magnitude of a current that flows through an ultrasonic transducer.  
         [0042]     The transducer drive circuit  23  further comprises a differential amplifier  29 , a D/A converter  30 , and a computer  31  which at least has a CPU  31 A and a memory  31 B. The computer  31  is connected with the D/A converter  30 , the foot switch (FSW)  3 , and the operation display panel  17 . The voltage/current detector (DET)  27  is connected to one input terminal of the differential amplifier  29 , and the D/A converter  30  is connected to the other input terminal.  
         [0043]     A program data effective as a soft ware procedure for controlling ultrasonic output is stored beforehand in the memory  31 B. Thus, the CPU  31 A reads the program data at the time of starting up from the memory  31 B to execute the program. The execution also includes reading of the information on the operation that has been performed by an operator for the operation display panel  17  and the foot switch  3 .  
         [0044]     As a result, with the execution of such a control, the CPU  31 A outputs a command current (digital signal) to the D/A converter  30 , by which the magnitude of a current corresponding to the output control pattern that has been set through the setting device  21  and the foot switch  3  is indicated.  
         [0045]     The D/A converter  30  converts the command current for driving into an analogue signal for output to a noninverting input terminal of the differential amplifier  29 . A current absolute value |I|, which has been detected by the voltage/current detector (DET)  27 , is being given to an inverting input terminal of the differential amplifier  29 , as a reference input. Further, an output terminal of the differential amplifier  29  is connected to the voltage control amplifier (VCA)  25 . Accordingly, the differential amplifier (VCA)  29  compares the command current outputted from the D/A converter  30  with the magnitude |I| of the current detected by the voltage/current detector (DET)  27 , and supplies a differential output to the voltage control amplifier (VCA)  25 , so that the values of the command current and the magnitude |I| of the current are equalized. Thus, the magnitude of the voltage added to the ultrasonic transducer is adjusted, so that the value of a current that passes through the ultrasonic transducer is controlled to be the same as the preset output control pattern.  
         [0046]     In the memory  31 B of the computer  31 , various kinds of output control patterns are stored in advance. The CPU  31 A produces a command current for driving which is indicative of the magnitude of a current that passes through the ultrasonic transducer, based on the output control patterns which are stored in the memory  31 B. Examples of such command currents are shown in FIGS.  4  to  6 , where the output control patterns are defined by the magnitude of the current |I| that passes through the ultrasonic transducer.  
         [0047]     In the treatment portion  5 , an amplitude of the ultrasonic vibration of the probe  9  is in proportion to the current |I| that passes through the ultrasonic transducer. Further, the magnitude of ultrasonic energy which effects in the coagulation and incision of living tissues is closely correlated with to the amplitude of the ultrasonic vibration of the probe  9  in the treatment portion  5 . In other words, definition of the magnitude of the current |I| that flows through the ultrasonic transducer also defines the magnitude of the ultrasonic energy that effects in the coagulation and incision of living tissues.  
         [0048]     The output control patterns shown in FIGS.  4  to  6  are described hereunder.  
         [0049]      FIG. 4  shows an output control pattern in which a constant first current I 1  is allowed to pass through an ultrasonic transducer (i.e. constant current control) during an ON-operation (from time t 0  to t 1 ) of the operation pedal  13  or the operation pedal  14  of the foot switch  3 .  
         [0050]      FIG. 5  shows a output control pattern in which: on an ON-operation (time t 0 ) of the operation pedal  13  or the operation pedal  14  of the foot switch  3 , a second current I 2  is allowed to flow; after lapse of a preset time t 2 , a third current I 3 , which is smaller than the second current I 2 , is allowed to flow; and when a preset time t 3  has been reached, current is allowed to be zero (the ultrasonic output is switched OFF). In short, this control pattern shows output conditions where the current I is reduced stepwise.  
         [0051]     In the output control pattern shown in  FIG. 5 , the second current I 2  is set, as an example, at a value which is slightly larger (e.g., I 2 =I 1 ×1.2) than the first current I 1 , and the third current I 3  is set at a smaller value (e.g., I 3 =I 1 ×0.6) than the first current I 1  (see  FIG. 4 ). Further, the time from t 0  to t 2  is set for approximately four seconds, and the time from t 2  to t 3  is set for approximately six seconds. In the control drive unit  1 , display means  33  and sonic means  34  are provided, which notify at the time t 3  that the ultrasonic output has been switched OFF (see  FIG. 1 ).  
         [0052]     The output control pattern shown in  FIG. 6  is a modification of the one shown in  FIG. 5 . The output control pattern shown in  FIG. 6  provides conditions in which the current: increasingly becomes larger after the ON-operation (time t 0 ) of the operation pedal  13  or the operation pedal  14  of the foot switch  3 ; reaches the value of the second current I 2 ; is then gradually (continuingly) reduced, after lapse of the preset time t 2 , from the value of the second current I 2  to the value of the third current I 3 ; and is controlled so that the current value becomes zero (the ultrasonic output is switched OFF).  
         [0053]     In the present embodiment, the currents have been described as satisfying a relation I 3 &lt;U 1 &lt;I 2 , however, the relation should not necessarily be limited to this relation. Further, the times t 2  and t 3  may be set at optimized values which mach the magnitudes of the currents I 2  and I 3 , respectively.  
         [0054]     The CPU  31 A of the computer  31  is also in charge of display processing as follows. Specifically, in the setting device  21  of the operation display panel  17 , on selection of a first output control pattern (e.g., the output control pattern shown in  FIG. 4 ) as a first setting value, which has been stored in the memory  31 B, letters or symbols (e.g., “COAG/CUT: 100%”) for representing the selected first output control pattern, are displayed at the first display  22   a . In the setting device  21 , when a second output control pattern (e.g., the output control pattern shown in  FIG. 5 ) is selected as a second setting value, the CPU  31 A displays at the second display  22   b , letters or symbols (e.g., “COAG: 100%”) representing the selected second output control pattern.  
         [0055]     The CPU  31 A is set such that, upon ON-operation of the first operation pedal  13  of the foot switch  3  by an operator, it detects this ON-operation to drive the ultrasonic transducer UT with the first output control pattern, and that, on the other hand, upon ON-operation of the second operation pedal  14  of the foot switch  3 , it drives the ultrasonic transducer UT with the second output control pattern, along its soft ware processing.  
         [0056]     The effects of the ultrasonic surgical apparatus according to the present embodiment are described hereunder with reference to  FIGS. 13 and 14 , in the context of the operation of ultrasonic treatment.  
         [0057]     A power switch  16  of the control drive unit  1  is firstly switched ON to set an output control pattern (output conditions) (step S 1  of  FIG. 13 ). The setting of this output control pattern is performed by operating the setting device  21  of the operation display panel  17 .  
         [0058]     When an operator selects the first output control pattern (e.g., the output control pattern shown in  FIG. 4 ) as the first set value through the setting device  21 , letters or symbols for representing the selected first output control pattern are displayed (steps S 2  and S 3 ) at the first display  22   a . Further, when the operator selects the second output control pattern (e.g., the output control pattern shown in  FIG. 5 ) as the second set value through the setting device  21 , letters or symbols representing the selected second output control pattern are displayed (steps S 2  and S 4 ) at the display  22   b.    
         [0059]     Then, the operator can have the living tissues be placed between the probe  9  and the holder  10  of the hand piece  2 . In this state, the handle  8  of the handling portion  6  is operated in a closing direction to hold the tissues between the probe  9  and the holder  10 .  
         [0060]     After holding of the tissues, the operator can perform an ON-operation through the first operation pedal  13  of the foot switch  3 , so that the ultrasonic transducer UT is driven (a first control mode: steps S 5  to S 8 ) with the first output control pattern. On the other hand, with an ON-operation of the second operation pedal  14  of the foot switch  3 , the ultrasonic transducer UT is driven (a second control mode: Steps S 5 , S 6 , S 9  and S 10 ) with the second output control pattern.  
         [0061]     Thus, for the first control mode (i.e., in the case of  FIG. 4 ), the probe  9  undergoes ultrasonic vibration, so that the living tissues held between the probe  9  and the holder  10  are coagulated by the frictional heat generated by the ultrasonic vibration, and then are incised. Meanwhile, for the second control mode (i.e., in the case of  FIG. 5 ), the probe  9  undergoes ultrasonic vibration, so that the living tissues held between the probe  9  and the holder  10  are firmly coagulated by the frictional heat generated by the ultrasonic vibration. In case of this second control mode, the processing of the living tissues is finished with the coagulation by an appropriate energy control. The reasons for this are described hereunder.  
         [0062]      FIG. 7  shows temperature changes of living tissues at the time of the ultrasonic treatment. A line A shows the temperature changes when the treatment is effected with the first output control pattern (the output control pattern along the current waveform shown in  FIG. 4 ). A line B shows the temperature changes when the treatment is effected with the second output control pattern (the output control pattern along the current waveform shown in  FIG. 5 ).  
         [0063]     In case of the first output control pattern, the temperature of the living tissues increases with the commencement (time t 0 ) of the ultrasonic output triggered by the ON-operation of the first operation pedal  13  of the foot switch  3 . Thereafter, the temperature increase declines once at about 100 to 150 degrees centigrade, where the electric power supplied to the ultrasonic transducer is consumed as energy for evaporating moisture contained in the living tissues. In the meantime, the living tissues are sufficiently coagulated. The state of coagulation is illustratively shown in  FIG. 14A . In the figure, indicated by a reference T are tissues, by a reference B is a blood vessel (blood flow), and by a reference BW is a blood vessel wall.  
         [0064]     Upon completion of the evaporation of moisture contained in the living tissues, the temperature of the living tissues begins increasing again. When the temperature has reached an incision-operative temperature (, for example, of about 200 degrees centigrade), incision of the living tissues is commenced. After the incision, the ultrasonic output is switched OFF with an OFF-operation (time t 1 ) of the first operation pedal  13 . In this way, incision is carried out in the state where the living tissues are coagulated, with the first output control pattern. The processes from the coagulation to the incision are shown in  FIGS. 14A and 14B .  FIG. 14B  shows a state where living tissues have been incised.  
         [0065]     In case of the second control pattern, the temperature of the living tissues increases with the commencement (time t 0 ) of the ultrasonic output triggered by the ON-operation of the second operation pedal  14  of the foot switch  3 , where the current I 2  of the second output control pattern is slightly larger than the current I 1  of the first output control pattern. For this reason, the temperature of the living tissues changes slightly faster than in the case of the first output control pattern. The temperature increase is also declined at about 100 to 150 degrees centigrade.  
         [0066]     In this case, as in the case of the first output control pattern, moisture contained in the living tissues are evaporated. After lapse of time t 2 , the current flowing through the ultrasonic transducer is switched to I 3 . Since the current I 3  is sufficiently smaller than the current I 1  of the first output control pattern, the temperature of the living tissues continues slightly increasing.  
         [0067]     When time t 3  is reached, the ultrasonic output is switched OFF. The fact that the ultrasonic output has been switched OFF is notified through the display means  33  or the sonic means  34  of the control drive unit  1 .  
         [0068]     After lapse of time t 3 , the temperature of the living tissues never reaches the incision-operative temperature. As shown in  FIG. 7 , for the second output control pattern, the time maintained at a coagulation-operative temperature is longer than in the case of the first output control pattern. Accordingly, for the second output control pattern, the living tissues are more fully coagulated in a short time before being incised.  
         [0069]     When the output control pattern shown in  FIG. 6  is selected as the second output control pattern, the living tissues are more firmly coagulated in a short time before being incised as in the case of the output control pattern shown in  FIG. 5 .  
         [0070]     As described above, treatment of living tissues with the second output control pattern as shown in  FIG. 5  or  6  enables firm coagulation in a short time.  
         [0071]     Selective operation of the operation pedal  13  or  14  of the foot switch  3  enables treatment that matches the states of the living tissues to be treated using the single hand piece  2 . For example, when living tissues including a blood vessel of a comparatively small diameter are treated, the operation pedal  13  is operated to perform coagulation and incision with the first output control pattern. Conversely, when living tissues including a blood vessel of a comparatively larger diameter are treated, the operation pedal  14  is operated to perform firm coagulation with the second output control pattern.  
         [0072]     As described above, according to the present embodiment, reliable coagulation of living tissues can be performed in a short time. Further, treatment depending on the states and kinds of the living tissues to be treated, is enabled using a single hand piece. Thus, according to the present embodiment, time can be saved which would otherwise have been required in making plural kinds of hand pieces be ready and in changing these hand pieces depending on the kinds or the like of living tissues. This may contribute to reducing time for surgery.  
         [0073]     (Modifications)  
         [0074]     Hereinafter, several modifications of the first embodiment described above are described with reference to FIGS.  8  to  11 .  
         [0075]     These modifications are associated with other examples of output control patterns than the ones that may be given to the ultrasonic transducer UT by the computer  31 .  
         [0076]     These output control patterns are stored in advance in the memory  31 B of the computer  31 . Thus, the CPU  31 A reads the pattern data from the memory  31 B to output a command current for driving to the D/A converter  30 , based on the ever-changing pattern data. In this way, current controls along the output control patterns shown in FIGS.  8  to  11  can be executed.  
         [0077]     While the command currents based on the output control patterns may be ensured to issue from the CPU  31 A, a function generator in which such patterns are stored in advance may be provided separately from the CPU, so that the outputs from the function generator may be ensured to be directed to the D/A converter  30  or the differential amplifier  29 .  
         [0078]      FIG. 8  shows an output control pattern of a first modification. In case of this output control pattern, upon an ON-operation (time t 0 ) of the operation pedal  13  or the operation pedal  14  of the foot switch  3 , the constant current I 1  is flowed. The pattern is ensured to be of a waveform for altering the current |I| into the form of pulses after lapse of preset time t 1 .  
         [0079]     In this modification, high level of pulsed output is represented by Ih, and its low level by IL, and an output duty of the high level Ih is set as Δta/Δtb. It is arranged such that when preset time t 2  has been reached, the current |I| is rendered to be zero (i.e. the ultrasonic output is switched OFF).  
         [0080]     In the control drive unit  1 , the display means  33  and the sonic means  34  are provided to switch OFF the ultrasonic output when time t 2  has been reached, as in the first embodiment.  
         [0081]     In the present embodiment, although I 1 &gt;Ih and IL&gt;0, they may be I 1 =Ih and IL=0, respectively.  
         [0082]      FIG. 9  shows an output control pattern of a second modification. In the output control pattern shown in  FIG. 9 , upon the ON-operation (time t 0 ) of the operation pedal  13  or the operation pedal  14  of the foot switch  3 , the current |I| is altered into the form of pulses from the very beginning. In this modification, a high level of pulsed output is represented by Ih, and its low level by IL, and an output duty of the high level Ih is set as Δta/Δtb. Unlike the previous modification, it is arranged such that the low level IL and the duty Δta/Δtb are fixed at constant values and that the high level Ih gradually reduces with the lapse of output time. Further, when preset time t 2  is has been reached, the current |I| is ensured to be zero (i.e. the ultrasonic output is switched OFF).  
         [0083]      FIG. 10  shows an output control pattern of a third modification. In the output control pattern shown in  FIG. 10 , the high level Ih and the duty Δta/Δtb are fixed at constant values, and the low level IL is set to be gradually reduced with the lapse of output time.  
         [0084]      FIG. 11  shows an output control pattern of a fourth modification. In the output control pattern shown in  FIG. 11 , the high level Ih and the low level IL are fixed at constant values, and the duty Δta/Δtb is set to be gradually reduced with the lapse of output time.  
         [0085]     Modifications other than those shown in FIGS.  9  to  11  may be provided, in which set values of each of the parameters Ih, IL and Δta/Δtb of output control patterns may be altered. For example, the high level Ih may be set at a constant value, and the low level IL and the duty Δta/Δtb may be set to be gradually reduced with the lapse of output time.  
         [0086]     In any of the output control patterns shown in FIGS.  8  to  11 , the magnitude of the current |I| that flows through the ultrasonic transducer per unit time, i.e. the ultrasonic energy which effects in the coagulation and incision of living tissues, reduces with the lapse of output time. Accordingly, by giving ultrasonic treatment with the output control patterns shown in FIGS.  8  to  11 , firm coagulation can be ensured in a short time before incising the living tissues, as in the case of the output control patterns shown in  FIGS. 5 and 6  related to the first embodiment. As a result, the effects similar to those in the first embodiment may be obtained in these modifications.  
       SECOND EMBODIMENT  
       [0087]     A second embodiment of the ultrasonic surgical apparatus is described hereinafter with reference to  FIG. 12 .  
         [0088]     In the ultrasonic surgical apparatus of the present embodiment, like or the same components as those of the first embodiment are referred to by the same reference numbers, and description therefore is omitted or simplified.  
         [0089]      FIG. 12  shows the transducer drive circuit  23  which is loaded on the control drive unit  1  of the ultrasonic surgical apparatus.  
         [0090]     As shown, the transducer drive circuit  23  is provided with an A/D converter  32 . The A/D converter  32  is connected between an output terminal of the differential amplifier  29  and the computer  31 , so that the A/D converter  32  converts output signals from the differential amplifier  29  into digital data and imparts the resultant to the computer  31 .  
         [0091]     The other portions of the configuration are the same with those described in the first embodiment.  
         [0092]     Upon ON-operation of the power switch  16  of the control drive unit  1 , the computer  31  in the drive circuit  23  performs control (step S 21  of  FIG. 15 ) so that a weak monitoring current Im of a constant level is constantly flowed.  
         [0093]     In the present embodiment, the magnitude of an output voltage from the output transformer  28  is in proportion to an input of an adder in the voltage control amplifier  25 . This means that an output signal to the voltage control amplifier  25  indicates the magnitude of loading (i.e. impedance) for ultrasonic vibration.  
         [0094]     In the present embodiment, a signal outputted from the differential amplifier  29 , i.e. an input signal to the voltage control amplifier  25 , is inputted to the computer  31  through the A/D converter  32 . As a result, the computer  31  constantly monitors the magnitude of the impedance for the ultrasonic vibration (step S 22  of  FIG. 15 ).  
         [0095]     An operator then carries out an ON-operation through the operation pedal  13  or the operation pedal  14  of the foot switch  3  (step S 23  of  FIG. 15 ) in an attempt to begin ultrasonic treatment under the output conditions (the output control patterns shown in the first embodiment or in their modifications) set through the setting device  21 . In this case, the CPU  31 A of the computer  31  exerts control, so that the ultrasonic output under the output conditions set through the setting device  21  is allowed to initiate only when the impedance |Z| being monitored is within a preset range (Zmin&lt;|Z|&lt;Zmax) (step S 24 ), whereby the treatment of living tissues is effected by using the ultrasonic vibration (i.e., the output is enable: step S 25 ). In contrast, when the impedance |Z| being monitored is outside the preset range (Zmin&lt;|Z|&lt;Zmax) (step S 25 ), the treatment of living tissues is not effected by using the ultrasonic vibration (i.e., the output is disenable: step S 26 ).  
         [0096]     The threshold values Zmin and Zmax for the impedance are determined based on impedance values at the time when comparatively soft living tissues to be treated are held by the treatment portion  5  of the hand piece  2 . Specifically, when no living tissues are being held by the treatment portion  5 , the impedance is: |Z|&lt;Zmin. In this state, no ultrasonic output is initiated under the output conditions set through the setting device  21  if an ON-operation is attempted through the operation pedal  13  or the operation pedal  14  of the foot switch  3 . Further, when a metal hemostatic clamp or hard living tissues, such as bone is being held, the impedance is: Zmax&lt;|Z|. In this state as well, no ultrasonic output is initiated under the output conditions set through the setting device  21  if an ON-operation is attempted through the operation pedal  13  or the operation pedal  14  of the foot switch  3 .  
         [0097]     In this way, the ultrasonic output is initiated only when the holding of the living tissues to be treated is ensured. Therefore, when treatment is effected under the output conditions where the magnitude of the ultrasonic waves is altered with the lapse of output time as shown in  FIG. 5 , for example, tissues can be reliably coagulated. In addition, since no ultrasonic output is initiated in the state of holding a metal hemostatic clamp or the like, the probe  9  can be prevented from being damaged.  
         [0098]     It should be noted that the monitoring current Im may be permitted to flow for only At seconds (e.g., several hundreds milliseconds) after the ON-operation of the operation pedal  13  or the operation pedal  14  of the foot switch  3 . In this case, the ultrasonic output is initiated after Δt seconds provided that the impedance |Z| is: Zmin&lt;|Z|&lt;Zmax.  
         [0099]     As described above, in the present embodiment, coagulation of living tissues can be reliably carried out as in the first embodiment. In addition, since damages on a probe can be prevented, good durability is ensured and repeated use is enabled, which, as a result, ensures realization of low costs.  
         [0100]     Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the present invention. Thus the scope of the present invention should be determined by the appended claims.