Patent Publication Number: US-2015073450-A1

Title: Liquid injection device and medical device

Description:
This application claims the benefit of Japanese Patent Application Nos. 2013-188261, filed on Sep. 11, 2013 and 2014-75011, filed on Apr. 1, 2014. The contents of the aforementioned applications are incorporated herein by reference in their entirety. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to injection of a liquid. 
     2. Related Art 
     In a liquid injection device used as a medical device, a method of measuring acceleration of an injection port and selecting a mode of liquid injection based on the acceleration is known (e.g., Patent Document 1 (JP-A-2012-143374)). 
     The related art is advantageous in exhibition of incision or excision performance according to intentions of an operator by switching an injection mode depending on the movement speed of the injection port. The inventors have further improved the technology and found a method of preferably changing the performance of incision or the like in response to the movement speed of the injection port. In addition, downsizing, lower cost, resource saving, facilitation of manufacture, improvement in usability of the device, etc. have been desired. The inventors have attempted to solve the problems. 
     SUMMARY 
     An advantage of some aspects of the invention is to solve at least one of the problems described above, and the invention can be implemented as the following forms. 
     (1) An aspect of the invention provides a liquid injection device. The liquid injection device includes a liquid injection mechanism having a liquid chamber and an air bubble generation unit provided in the liquid chamber and generating air bubbles, and a control unit that changes a drive signal for driving the air bubble generation unit in response to a movement speed of the liquid injection mechanism. According to this aspect, the drive signal is changed in response to the movement speed, and thereby, the condition of the air bubble generation unit may be adjusted in response to the movement speed and the depth of excision may be stabilized. 
     (2) In the aspect described above, the air bubble generation unit may adjust a volume of air bubbles generated per unit time in response to at least one of a voltage, a current, power, and a duty of the drive signal. In this case, the control unit may set the drive signal to a first state when the movement speed is a first speed, and set a voltage of the drive signal to a second state in which the volume of the generated air bubbles is larger than that in the first state when the movement speed is a second speed higher than the first speed. According to this aspect, the volume of the air bubbles generated per unit time may be easily controlled. This is because the volume of the air bubbles generated per unit time may be relatively easily increased. 
     (3) In the aspect described above, the control unit may change a frequency of the drive signal in response to the movement speed. According to this aspect, the volume of the air bubbles generated per unit time may be adjusted using other methods than changing the voltage, the current, the power, and the duty. 
     (4) In the aspect described above, the control unit may set the frequency of the drive signal to a first frequency when the voltage is in the first state or the second state, and set the frequency of the drive signal to a second frequency higher than the first frequency when the drive signal is in a third state in which the volume of the generated air bubbles is larger than that in the second state. According to this aspect, when the voltage is a first or second voltage, the output is controlled by changing of the voltage without changing of the frequency of the drive signal, and thereby, the values of the first and second voltages may be easily determined. 
     (5) In the aspect described above, the control unit may set the drive signal to the third state and sets the frequency of the drive signal to the second frequency when the movement speed is a third speed higher than the second speed, and set the drive signal to the third state and sets the frequency of the drive signal to a third frequency higher than the second frequency when the movement speed is a fourth speed higher than the third speed. According to this aspect, when the movement speed is the third or fourth speed, the output is controlled by changing of the frequency without changing of the voltage of the drive signal, and thereby, the values of the second and third frequencies may be easily determined. 
     (6) In the aspect described above, a liquid feed unit that feeds a liquid to the liquid chamber at a flow rate set by the control unit is provided, and the control unit sets the flow rate to a first flow rate when the movement speed is the first speed and sets the flow rate to a second flow rate higher than the first flow rate when the movement speed is the second speed. According to this aspect, the flow rate to be fed may be properly set. 
     (7) In the aspect described above, the control unit may change the state and the frequency of the drive signal in response to the movement speed. According to this aspect, the generation of the air bubbles by the air bubble generation unit may be changed by the state and the frequency of the drive signal. 
     The aspects of the invention may be realized in various another forms. For example, the aspects of the invention may be realized in forms of a liquid injection method, a medical device, a surgery method, programs for realization of the methods, memory media storing the programs, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a configuration diagram of a liquid injection device of a first embodiment. 
         FIG. 2  is a sectional view showing inside of a liquid injection mechanism of the first embodiment. 
         FIG. 3  is a graph showing a waveform of a drive signal. 
         FIG. 4  is a flowchart showing injection processing of the first embodiment. 
         FIGS. 5A and 5B  are graphs showing relations between a drive voltage and a drive frequency and a movement speed. 
         FIG. 6  is a graph showing a relation between the drive frequency and the drive voltage. 
         FIG. 7  is a flowchart showing injection processing of a second embodiment. 
         FIG. 8  is a configuration diagram of a liquid injection device of a third embodiment. 
         FIG. 9  is a sectional view showing inside of a liquid injection mechanism of the third embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A. First Embodiment 
     An embodiment of the invention will be explained.  FIG. 1  shows a configuration of a liquid injection device  10  as the first embodiment. The liquid injection device  10  is a medical device used in medical institutions, and has a function of injecting a liquid to an affected part to incise or excise the affected part. 
     The liquid injection device  10  includes a liquid injection mechanism  20 , a liquid feed mechanism  50 , a control unit  70 , a controller  77 , and a liquid container  80 . The liquid feed mechanism  50  and the liquid container  80  are connected to each other by a connecting tube  51 . The liquid feed mechanism  50  and the liquid injection mechanism  20  are connected to each other by a liquid feed channel  52 . The connecting tube  51  and the liquid feed channel  52  are formed using resin. The connecting tube  51  and the liquid feed channel  52  may be formed using other materials (e.g., metal) than resin. 
     The liquid container  80  stores saline. In place of saline, pure water or chemical solution may be stored therein. The liquid feed mechanism  50  feeds a liquid suctioned from the liquid container  80  by driving of a pump inside via the connecting tube  51  to the liquid injection mechanism  20  via the liquid feed channel  52 . 
     The liquid injection mechanism  20  is a tool operated in hand by a user of the liquid injection device  10 . The user applies the liquid intermittently injected from the liquid injection mechanism  20  to the affected part, and thereby, incises or excises the affected part. 
     The control unit  70  controls the liquid feed mechanism  50  via a control cable  71 , and thereby, controls a flow rate of the liquid fed to the liquid injection mechanism (hereinafter, referred to as “feed flow rate”). A foot switch  75  is connected to the control unit  70 . When the user turns on the foot switch  75 , the control unit  70  controls the liquid feed mechanism  50  to execute feed of the liquid to the liquid injection mechanism  20  and transmit a drive signal to the controller  77  via a signal cable  72 . 
     The controller  77  supplies power to the liquid injection mechanism  20  via a signal cable  78  in response to the drive signal. By the power supply, as will be described later, air bubbles are generated in an air bubble generation unit, and the liquid is injected from the liquid injection mechanism  20 . 
       FIG. 2  is a sectional view showing inside of the liquid injection mechanism  20 . The liquid injection mechanism  20  forms a liquid chamber  25  inside. The liquid chamber  25  has openings on both a posterior end and an anterior end and the opening of the posterior end is connected to the liquid feed mechanism  50  via the liquid feed channel  52 . Accordingly, the liquid chamber  25  is filled with the liquid fed from the liquid feed mechanism  50 . On the other hand, the opening of the anterior end of the liquid chamber  25  is formed as an injection port  28 . 
     An air bubble generation unit  60  is provided in the liquid chamber  25  of the liquid injection mechanism  20 . A heater  73  that generates heat by energization is provided on one end surface of the air bubble generation unit  60 . When a voltage is applied to the heater  73  by a voltage signal output from the controller  77 , the heater  73  promptly generates heat. The heat of the heater  73  is absorbed by the liquid filling the liquid injection mechanism.  20  and the liquid is vaporized. In the first embodiment, the heater  73  is intermittently energized, and the vaporization intermittently occurs (if the liquid is water, it instantaneously boils). The intermittently occurring vaporization instantaneously increases the pressure of the liquid within the liquid injection mechanism  20 . The instantaneously increased pressure injects the liquid from the injection port  28 . Incidentally,  FIG. 2  shows an operation principle of the liquid injection mechanism  20 , and the actual injection port  28  is formed to be thinner to emit a thin flow (pulsating flow) for surgery. When the heater  73  is energized and the liquid is vaporized, the liquid within the liquid chamber  25  subjected to the pressure spouts as a pulsating flow from the injection port  28 . 
     The liquid injection mechanism  20  includes an acceleration sensor  29 . The acceleration sensor  29  is a piezoresistive triaxial acceleration sensor. As shown in  FIG. 2 , the acceleration sensor  29  is provided near the injection port  28  and outside of a casing of the liquid injection mechanism  20 . Measurement results are input to the control unit  70  via an acceleration sensor cable  76 . The acceleration sensor cable  76  is fixed to the outside of the casing of the liquid injection mechanism  20  by bonding from the connecting part to the acceleration sensor cable  76  to the posterior end of the liquid injection mechanism.  20  (the opposite side to the injection port  28 ). 
     The three axes as the measuring objects of the acceleration sensor  29  are respective axes of XYZ shown in  FIG. 2 . The Z-axis is in parallel to the longitudinal axis directions of the liquid injection mechanism  20 , i.e., in parallel to the injection direction of the liquid, and the direction in which the liquid is injected is a negative direction. The X-axis is orthogonal to the Z-axis and a predetermined direction is a positive direction. The predetermined direction is upward in the vertical direction when the Z-axis is directed to be horizontal and the acceleration sensor  29  is located immediately below as shown in  FIG. 2 . The Y-axis is defined by the right-handed system with reference to the X-axis and the Z-axis. 
       FIG. 3  is a graph showing a waveform of the drive signal. The drive signal is input to the controller  77  for heating the heater  73  as described above. The vertical axis indicates the voltage and the horizontal axis indicates time. The waveform of the drive signal in the embodiment is pulsed as shown in  FIG. 3 . The maximum voltage of each pulsed wave (hereinafter, referred to as “drive voltage”) and the frequency of the pulsed wave (hereinafter, referred to as “drive frequency”) change depending on the injection processing, which will be described later with  FIG. 4 . 
       FIG. 3  exemplifies the case where the drive voltage takes a value between the maximum value (Vmax) and the minimum value (Vmin) and the drive period takes the maximum value, i.e., the drive frequency takes the minimum value (Fmin). When the drive voltage is larger, the controller  77  controls energization so that the amount of power supplied to the heater  73  by single heating may be larger. On the other hand, when the drive frequency is larger, the controller  77  controls energization so that the number of times of heating of the heater  73  per unit time may be larger. In either case, the amount of power for heating the heater  73  (energy per unit time) is larger. When the amount of power for heating the heater  73  is larger, excision performance is improved as will be described later. 
       FIG. 4  is a flowchart showing injection processing. The injection processing is repeatedly executed by the control unit  70  while the foot switch  75  is pushed. First, the speed S of the injection port  28  is calculated (step S 100 ). The speed S here refers to an absolute value of the speed in the XY-plane. That is, the speed is an absolute value of the velocity when the velocity in the Z-axis direction is ignored. The speed S is calculated based on the acceleration on the three axes measured by the acceleration sensor  29 . 
     The speed S is calculated as a parameter having an effect on the depth of the excision of the affected part. This is because the excision performance acting on the respective local areas of the affected part per unit time is influenced by the relative speed of the injection port  28  and the affected part. Accordingly, in consideration of the case where the affected part moves with breathing of a patient or the like, the speed S may be treated as the movement speed of the affected part and the injection port  28 , however, in the embodiment, on the assumption that the affected part remains stationary, the speed S is treated as the movement speed of the affected part and the injection port  28 . 
     Subsequently, the drive voltage and the drive frequency are determined based on the calculated speed S (step S 200 ).  FIGS. 5A and 5B  are graphs showing relations between the drive voltage and the drive frequency and the speeds.  FIG. 5A  shows the drive voltage and  FIG. 5B  shows the drive frequency on the vertical axes. The horizontal axes indicate the speed S in common and the scales are the same in  FIGS. 5A and 5B . 
     As shown in  FIGS. 5A and 5B , in the respective speed ranges of Sa≦speed S≦Sb, Sb≦speed S≦Sc, the parameters with values to be changed are different. That is, Sa, Sb, and Sc are speeds predetermined as threshold values for switching the parameters to be changed. 
     If S≦Sa, the drive voltage is fixed to Vmin as the minimum value and the drive frequency is fixed to Fmin as the minimum value. When the parameters are set as described above, the excision performance is the lowest. 
     If Sa speed S≦Sb, the drive frequency is fixed to Fmin, and the drive voltage linearly increases with respect to the increase of the speed S. If speed S=Sb, the drive voltage is set to Vmax as the maximum value. Vmin is set so that the excision performance may not be too low. Vmax is set so that the heater  73  may not be excessively heated. When the drive voltage is larger, the amount of power per single energization to the heater  73  is larger, and the pressure fluctuations within the liquid injection mechanism  20  are larger. As a result, the liquid is energetically injected and the excision performance is greater, and, even when the speed S is higher, the depth of excision is stable. 
     If Sb≦speed S≦Sc, the drive voltage is fixed to Vmax, and the drive frequency linearly increases with respect to the increase of the speed S. If speed S=Sc, the drive frequency is set to Fmax as the maximum value. Fmin is set so that the excision performance may not be too low. Fmax is set so that the heater  73  may not be excessively heated. When the drive frequency is larger, the number of times of injection per unit time is larger. As a result, the excision performance is larger, and, even when the speed S is higher, the depth of excision is stable. If the period of the energization is shorter, the time taken for cooling the heater  73  at a high temperature by energization with the liquid is not sufficiently secured. The upper limit of the drive frequency is determined in consideration of the time taken for cooling the heater  73 . 
     The drive voltage and the drive frequency are determined as described above, and then, the feed flow rate is determined (step S 300 ). The feed flow rate is determined to be a sufficient value for replenishment of the liquid to be intermittently injected. When the value is larger in either case of the drive voltage or the drive frequency, the amount of liquid injected per unit time increases. Therefore, at least one of the drive voltage and the drive frequency is increased, and the feed flow rate is increased. Finally, the control is executed based on the determined drive voltage, drive frequency, and feed flow rate (step S 400 ). 
     As described above, the drive voltage is changed so that the excision performance may be improved with the increase of the speed S, and thereby, the drive voltage applied to the heater  73  may be changed and the depth of excision may be stabilized. The amount of power supplied to the heater  73  may be greatly controlled by the drive voltage, and is preferable as a parameter for controlling generation of air bubbles. Further, when the drive voltage reaches the maximum value, the drive frequency is changed, and thereby, the depth of excision may be stabilized. 
       FIG. 6  is a graph showing a relation between the drive frequency and the drive voltage. As described above, the drive frequency does not change in the range of the speed S (Sa≦speed S≦Sb) in which the drive voltage changes, but changes in the range of the speed S (Sb≦speed S≦Sc) in which the drive voltage is Vmax. The ranges of the speed S in which the drive voltage and the drive frequency are changed are separated, and thus, the values of the drive voltage and the drive frequency are easily determined in the respective speed ranges. 
     As shown in  FIGS. 5A to 6 , S1 to S4 are examples of first to fourth speeds, V1 to V3 are examples of first to third voltages, and F1 to F3 are examples of first to third frequencies in the appended claims. The heater  73  and the controller  77  are examples of an air bubble generation unit in the appended claims. 
     B. Second Embodiment 
     Next, the second embodiment of the invention will be explained. The second embodiment executes injection processing shown in  FIG. 7  in place of the injection processing shown in  FIG. 4 . The hardware configuration is the same as that of Embodiment 1 and the explanation will be omitted. Step S 100 , step S 300 , and step S 400  in the injection processing in Embodiment 2 are the same as those of Embodiment 1 and the explanation will be omitted. In Embodiment 2, step S 210  to step S 240  are executed in place of step S 200  of Embodiment 1. 
     The speed S is calculated (step S 100 ), and then, the drive voltage is determined based on the calculated speed S (step S 210 ). The method of determining the drive voltage is the same as that of Embodiment 1. The drive voltage is fixed to Vmin if speed S≦Sa, linearly increases with the increase of the speed S if Sa≦speed S≦Sb, and fixed to Vmax if speed Sb≦speed S. 
     Then, whether or not the drive voltage is set to the maximum value (Vmax) is determined (step S 220 ). If the drive voltage is set to a value less than the maximum value (step S 220 , NO), the drive frequency is set to the minimum value (Fmin) (step S 240 ). The fact that the drive voltage is set to a value less than the maximum value means that the excision performance may be further improved by changing of the drive voltage. Accordingly, it is not necessary to improve the excision performance by changing of the value of the drive frequency, and the drive frequency is set to the minimum value. 
     On the other hand, if the drive voltage is set to the maximum value (step S 220 , YES), the drive frequency is determined based on the speed S (step S 230 ). The method of determining the drive frequency is the same as that of Embodiment 1. The drive frequency is fixed to Fmin if speed S≦Sb, linearly increases with the increase of the speed S if Sb≦speed S≦Sc, and fixed to Fmax if speed Sc≦speed S. 
     The fact that the drive voltage is set to the maximum value means that the excision performance may not be further improved by changing of the drive voltage. Accordingly, in order to improve the excision performance by changing the value of the drive frequency, step S 230  is executed. According to Embodiment 2, the same control result as that of Embodiment 1 may be obtained. 
     C. Third Embodiment 
     The third embodiment of the invention will be explained.  FIG. 8  is a schematic configuration diagram of a liquid injection device  110  of the third embodiment. The liquid injection device  110  is also a medical device used in medical institutions, and has a function of injecting a liquid to an affected part to incise or excise the affected part. 
     The liquid injection device  110  includes a liquid injection mechanism  120 , a liquid feed mechanism  150 , a control unit  170 , an output unit  173 , a controller  177 , and a liquid container  180 . The liquid feed mechanism  150  and the liquid container  180  are connected to each other by a connecting tube  151 . The liquid feed mechanism  150  and the liquid injection mechanism  120  are connected to each other by a liquid feed channel  152 . The connecting tube  151  and the liquid feed channel  152  are formed using resin. The connecting tube  151  and the liquid feed channel  152  may be formed using other materials (e.g., metal) than resin. 
     The liquid container  180  stores saline. In place of saline, pure water or chemical solution may be stored. The liquid feed mechanism  150  feeds a liquid suctioned from the liquid container  180  by driving of a pump inside via the connecting tube  151  to the liquid injection mechanism  120  via the liquid feed channel  152 . 
     The liquid injection mechanism  120  is a tool operated in hand by a user of the liquid injection device  110 . The user applies the liquid intermittently injected from the liquid injection mechanism  120  to the affected part, and thereby, incises or excises the affected part. 
     The control unit  170  controls the liquid feed mechanism  150  via a control cable  171 , and thereby, controls a flow rate of the liquid fed to the liquid injection mechanism  120  (hereinafter, referred to as “feed flow rate”). A foot switch  175  is connected to the control unit  170 . When the user turns on the foot switch  175 , the control unit  170  controls the liquid feed mechanism  150  to execute feed of the liquid to the liquid injection mechanism  120  and transmit a drive signal to the controller  177  via a signal cable  172 . 
     In order to output optical maser in response to the drive signal, the controller  177  outputs a control signal to the output unit  173  via a signal cable  178 . The output unit  173  includes holmium:YAG optical maser, and outputs optical maser according to the control signal. The wavelength of the optical maser is 2.06 The output optical maser passes through an optical maser cable  174  formed using an optical fiber and is guided into the liquid injection mechanism  120 . 
       FIG. 9  is a sectional view showing inside of the liquid injection mechanism  120 . The liquid injection mechanism  120  forms a liquid chamber  125  inside. The liquid chamber  125  is filled with the liquid fed from the liquid feed mechanism  150 . The optical maser guided by the optical maser cable  174  is emitted within the liquid injection mechanism  120 . The emitted optical maser is absorbed by the liquid filling the liquid injection mechanism  120 . The part in which the optical maser is absorbed is shown as an air bubble generation unit  160  in  FIG. 8 . The liquid that has absorbed the optical maser is vaporized by the absorbed energy and forms air bubbles. In the embodiment, the optical maser is intermittently output, and the vaporization intermittently occurs. The intermittently generated air bubbles instantaneously increase the pressure of the liquid within the liquid injection mechanism  120 . The instantaneously increased pressure injects the liquid from an injection port  128 . The condition in which the pressure acts on the liquid by the generated air bubbles in the direction of the injection port  128  is shown by an arrow EZ in  FIG. 9 . 
     The liquid injection mechanism  120  includes an acceleration sensor  129 . The acceleration sensor  129  is a piezoresistive triaxial acceleration sensor. As shown in  FIG. 9 , the acceleration sensor  129  is provided near the injection port  128  and outside of a casing of the liquid injection mechanism  120 . Measurement results are input to the control unit  170  via an acceleration sensor cable  176 . The acceleration sensor cable  176  is fixed to the outside of the casing of the liquid injection mechanism  120  by bonding from the connecting part to the acceleration sensor cable  176  to the posterior end of the liquid injection mechanism  120  (the opposite side to the injection port  128 ). 
     The three axes as the measuring objects of the acceleration sensor  129  are respective axes of XYZ shown in  FIG. 9 . The Z-axis is in parallel to the longitudinal axis directions of the liquid injection mechanism  120 , i.e., in parallel to the injection direction of the liquid, and the direction in which the liquid is injected is a negative direction. The X-axis is orthogonal to the Z-axis and a predetermined direction is a positive direction. In the third embodiment, the relation among the respective axes is the same as that of the first embodiment such that the Y-axis is defined by the right-handed system with reference to the X-axis and the Z-axis. 
     In the third embodiment, the air bubbles are generated in the liquid chamber  125  by energy injection using the optical maser as described above, in place of heating by the heater  73  of the first embodiment. When the optical maser is output from the output unit  173 , the optical maser is guided by the optical fiber  174  and emitted from the end thereof. The liquid within the liquid chamber  125  absorbs the optical maser and forms air bubbles. The waveform of the drive signal with respect to the output unit  173  is the same as that shown in the graph of  FIG. 3 . As described above, the drive signal is input to the controller  177  for outputting the optical maser. The drive signal that intermittently operates the optical maser is output as pulsed wave. The maximum voltage of each pulsed wave (hereinafter, referred to as “drive voltage”) and the frequency of the pulsed wave (hereinafter, referred to as “drive frequency”) change depending on injection processing. 
     The injection processing in the third embodiment is the same as that of the first embodiment ( FIG. 4 ) and the drive voltage output from the control unit  170  is the same as the drive voltage of the first embodiment ( FIG. 3 ). The control ranges of the drive voltage and the drive frequency output from the control unit  170  are the same as those of the first embodiment ( FIGS. 5A and 5B ). Further, the relation between the drive frequency and the drive voltage is the same as that of the first embodiment ( FIG. 6 ). Therefore, also, in the third embodiment, when one of the drive voltage and the drive frequency output from the control unit  170  to the controller  177  is larger, the output of the emitted optical maser (energy per unit time) is larger. When the output of the emitted optical maser is larger, the excision performance is improved. 
     Therefore, in the third embodiment, the same advantages as those of the first embodiment may be obtained. Further, in the third embodiment, the optical maser is used for the output unit  173  and, in the air bubble generation unit  160 , the liquid absorbs the energy of the optical maser and forms air bubbles. Thus, the output unit  173  as the energy generation unit is not within the liquid injection mechanism  120  and, even when the liquid injection mechanism  120  is contaminated, replacement of the output unit  173  is unnecessary. 
     The invention is not limited to the embodiments, examples, modified examples of the specification, and may be realized in various configurations without departing from the scope thereof. For example, the technological features in the embodiments, examples, modified examples corresponding to the technological features in the respective embodiments described in Summary of the Invention may be appropriately replaced or combined in order to solve part or all of the above described problems or achieve part or all of the above described advantages. If the technological features are not explained as essential features in the specification, they may be appropriately deleted. For example, the following features are exemplified. 
     The drive voltage and the drive frequency may be determined using functions. 
     The speed range in which the drive voltage is varied and the speed range in which the drive frequency is varied may overlap. 
     The waveform of the drive signal is not limited to the pulsed wave, but may be a sine curve or the like, for example. 
     The relations between the respective drive voltage and drive frequency and the speed of the injection port may be specified by a curve or steps. 
     Only one of the drive voltage and the drive frequency may be changed. 
     When the drive voltage is changed, not limited to the change of the maximum voltage, but voltages equal to or more than a predetermined value or voltages in a predetermined period may be changed. 
     At least one of the drive voltage and the drive frequency may be changed in response to the distance between the injection port and the affected part. This is because the distance between the injection port and the affected part is considered as a parameter relating to the depth of excision like the movement speed of the injection port and the affected part. Specifically, as the distance between the injection port and the affected part is larger, at least one of the drive voltage and the drive frequency may be changed for improvement of the excision performance. 
     The output of the optical maser may be adjusted by changing of a pulse width. The pulse width is a time in which the drive signal reaches the maximum voltage. 
     The speed of the injection port may be calculated using image processing. For example, the speed of the injection port may be calculated by providing a marker near the injection port and capturing the movement of the marker with a camera. 
     When a robot operates the liquid injection device, it is not necessary to calculate the speed of the injection port because the robot may grasp the speed. The grasped value may be used. 
     The movement speed of the injection port may be calculated in consideration of the movement speed of the affected part. The measurement of the movement speed of the affected part may be realized by prediction or measurement of the movement due to breathing and pulsing. 
     Further, the movement speed may be detected not only in the injection port but also in a part moving with the movement of the injection port. The movement speed of the liquid injection mechanism may be detected. 
     The type of the acceleration sensor may be a capacitance type or heat detection type. Further, a sensor that may indirectly or directly detect the speed, not the acceleration may be employed. 
     The liquid injection device may be used for others than the medical device. 
     For example, the liquid injection device may be used for a cleansing device that removes dirt with the injected liquid. 
     The liquid injection device may be used for a drawing device that draws lines etc. with the injected liquid. 
     To generate air bubbles in the air bubble generation unit, other configurations than the heater of the first, second embodiments or the optical maser of the third embodiment may be employed. For example, microwave or the like may be used. Further, for the heater, not limited to a metal type including nichrome and tungsten, but a ceramic type may be used. 
     Further, the type of the optical maser may be another solid type than holmium: YAG or a semiconductor type, a liquid type, or a gas type optical maser may be used. 
     When the kind of the liquid to be injected is changed, the wavelength of the optical maser or the like may be changed to a wavelength that is easily absorbed by the changed liquid. 
     The method of feeding the liquid is not limited to that using driving of the pump, but may be a method using the liquid&#39;s own weight, for example.