Patent Publication Number: US-2021177487-A1

Title: Medical heater, treatment tool, and treatment tool manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application No. PCT/JP2018/033619, filed on Sep. 11, 2018, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a medical heater, a treatment tool, and a treatment tool manufacturing method. 
     2. Related Art 
     There is a known treatment tool that applies energy to a site as a target of treatment (hereinafter, referred to as a target site) in a biological tissue for treatment of the target site (refer to US 2015/0327909 A, for example). 
     The treatment tool described in US 2015/0327909 A includes a pair of gripping members to grip the target site. The gripping member includes a medical heater that generates heat when energized, and a treatment member that comes into contact with the target site when the target site is gripped by the pair of gripping members. The treatment tool allows the heat from the medical heater to be transferred to the target site gripped with the pair of gripping members via the treatment member. This achieves treatment of the target site. 
     Furthermore, a medical heater described in US 2015/0327909 A includes a substrate and a conductive portion provided on the substrate. The conductive portion includes first and second connecting portions to which individual wiring members are electrically connected, and a heat generating portion that generates heat when energized. The first and second connecting portions are disposed side by side in a width direction of the substrate on the proximal end side of the substrate. Furthermore, the heat generating portion has a substantially U-shape extending from the proximal end side toward the distal end side, folded back on the distal end side, and extending back to the proximal end side on the substrate. In addition, either end of the heat generating portion is electrically connected to the first and second connecting portions, individually. That is, the conductive portion has two electric paths parallel to each other in the width direction of the substrate. 
     SUMMARY 
     In some embodiments, a medical heater includes: a substrate having a first plate surface and a second plate surface forming front and back surfaces of the substrate, the substrate being electrically insulating and flexible; and a conductive portion provided on the first plate surface. The substrate is folded back in a state where the first plate surface forms an outer surface in a longitudinal direction of the substrate, the conductive portion includes: a pair of connecting portions to which wiring members are electrically connected, each connecting portion being provided at either end of the substrate in the longitudinal direction; a heat generating portion configured to generate heat when energized; and an electric path portion that is connected from the connecting portions to the heat generating portion so as to energize the heat generating portion, and the heat generating portion has a configuration in which a resistance value of the heat generating portion is higher than resistance values of other parts in the conductive portion, and a thickness measurement of at least a part of the heat generating portion is smaller than thickness measurements of other parts in the conductive portion. 
     In some embodiments, a treatment tool includes: a treatment member having a treatment surface on which treatment of a biological tissue is performed and an installation surface forming front and back surfaces of the treatment member with the treatment surface; and a medical heater configured to heat the treatment member. The medical heater includes: a substrate having a first plate surface and a second plate surface forming front and back surfaces of the substrate, the substrate being electrically insulating and flexible; and a conductive portion provided on the first plate surface, the substrate is folded back in a longitudinal direction of the substrate in a state where the first plate surface forms an outer surface of the substrate, the conductive portion includes: a pair of connecting portions to which wiring members are electrically connected, each connecting portion being provided at either end of the substrate in the longitudinal direction; a heat generating portion configured to generate heat when energized; and an electric path portion that is connected from the connecting portions to the heat generating portion so as to energize the heat generating portion, the heat generating portion has a configuration in which a resistance value of the heat generating portion is higher than resistance values of other parts in the conductive portion, and a thickness measurement of at least a part of the heat generating portion is smaller than thickness measurements of other parts in the conductive portion, and the medical heater is installed in a state where the heat generating portion faces the installation surface. 
     In some embodiments, a treatment tool manufacturing method includes: forming a conductive portion including a heat generating portion, on a first plate surface of a substrate; folding back the substrate in a longitudinal direction of the substrate in a state where the first plate surface forms an outer surface of the substrate so as to form a medical heater; and installing the medical heater on a treatment member having an installation surface on which treatment of a biological tissue is performed in a state where the heat generating portion faces the installation surface. The conductive portion includes: a pair of connecting portions to which wiring members are electrically connected, each connecting portion being provided at either end of the substrate in the longitudinal direction; the heat generating portion configured to generate heat when energized; and an electric path portion that is connected from the connecting portions to the heat generating portion so as to energize the heat generating portion, and formation of the conductive portion is performed in a state where a thickness measurement of at least a part of the heat generating portion is smaller than thickness measurements of other portions in the conductive portion. 
     The above and other features, advantages and technical and industrial significance of this disclosure will be better understood by reading the following detailed description of presently preferred embodiments of the disclosure, when considered in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating a treatment system according to a first exemplary embodiment; 
         FIG. 2  is a view illustrating a gripping portion; 
         FIG. 3  is a view illustrating a gripping portion; 
         FIG. 4  is a view illustrating a medical heater; 
         FIG. 5  is a view illustrating a medical heater; 
         FIG. 6  is a view illustrating a medical heater; 
         FIG. 7  is a flowchart illustrating a method of manufacturing a treatment tool; 
         FIGS. 8A to 8D  are views illustrating a method of manufacturing a treatment tool; 
         FIG. 9  is a view illustrating a method of manufacturing a treatment tool; and 
         FIG. 10  is a view illustrating a medical heater according to a second exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, modes for carrying out the disclosure (hereinafter referred to as embodiments) will be described with reference to the drawings. The disclosure is not limited to the embodiments described below. In the drawings, same reference signs are attached to the same components. 
     Schematic Configuration of Treatment System 
       FIG. 1  is a view illustrating a treatment system  1  according to a first exemplary embodiment. 
     The treatment system  1  applies thermal energy to a site as a treatment target (hereinafter, referred to as a target site) in a biological tissue, and thereby achieves treatment of the target site. Here, the treatment typically includes coagulation and incision of the target site. As illustrated in  FIG. 1 , the treatment system  1  includes a treatment tool  2 , a control device  3 , and a foot switch  4 . 
     Configuration of Treatment Tool 
     The treatment tool  2  is a surgical treatment tool for performing the treatment of a target site through the abdominal wall, for example. As illustrated in  FIG. 1 , the treatment tool  2  includes a handle  5 , a shaft  6 , and a gripping portion  7 . 
     The handle  5  is a part held by a surgeon. As illustrated in  FIG. 1 , the handle  5  includes an operation knob  51 . 
     The shaft  6  has a substantially cylindrical shape. In the following, one side running along a central axis Ax of the shaft  6  will be referred to as a distal end side Ar 1  ( FIG. 1 ), while the other side will be referred to as a proximal end side Ar 2  ( FIG. 1 ). A part of the proximal end side Ar 2  of the shaft  6  is inserted into the handle  5  from the distal end side An of the handle  5 , whereby the shaft  6  is attached to the handle  5 . In addition, the shaft  6  internally includes a movable member  61  ( FIG. 1 ) that reciprocates along the central axis Ax in accordance with the operation of the operation knob  51  by the surgeon. Furthermore, an electric cable C ( FIG. 1 ) has one end connected to the control device  3  and the other end provided through the inside of the handle  5  and the shaft  6  to reach the gripping portion  7 . 
     Configuration of Gripping Portion 
       FIGS. 2 and 3  are views illustrating the gripping portion  7 . Specifically,  FIG. 2  is a cross-sectional view of the gripping portion  7  cut along a plane along the central axis Ax.  FIG. 3  is a cross-sectional view of the gripping portion  7  cut by a plane orthogonal to the central axis Ax. 
     The gripping portion  7  is a portion that is used for treatment of the target site while gripping the target site. As illustrated in  FIGS. 1 to 3 , the gripping portion  7  includes first and second gripping members  8  and  9 . 
     The first and second gripping members  8  and  9  are configured to be openable/closable in a direction of arrow Y 1  ( FIG. 1 ) in accordance with the operation of the operation knob  51  by the surgeon. 
     Configuration of First Gripping Member 
     In  FIGS. 2 and 3 , the first gripping member  8  is arranged on the lower side with respect to the second gripping member  9 . As illustrated in  FIG. 2 or 3 , the first gripping member  8  includes a support member  10 , a heat insulating member  11 , a treatment member  12 , and a medical heater  13 . 
     The support member  10  has an elongated shape extending in a longitudinal direction (left-right direction (direction along the central axis Ax) in  FIG. 2 ) connecting the distal end and the proximal end of the gripping portion  7 , with one end of the support member  10  being fixed to an end of the distal end side Ar 1  of the shaft  6 . In addition, the support member  10  uses its upper surface in  FIGS. 2 and 3  to support the heat insulating member  11 , the treatment member  12 , and the medical heater  13 . 
     Examples of the material constituting the support member  10  described above include a metal material such as stainless steel or titanium. 
     The heat insulating member  11  has an elongated shape extending in the longitudinal direction of the gripping portion  7 , and is fixed to the upper surface of the support member  10  in  FIGS. 2 and 3 . 
     There is provided a recess  111  on the upper surface of the heat insulating member  11  in  FIGS. 2 and 3 , extending from the proximal end of the heat insulating member  11  toward the distal end side Ar 1 . The heat insulating member  11  supports the treatment member  12  and the medical heater  13  in the recess  111 . 
     Examples of the material constituting the heat insulating member  11  described above include a resin material having a low thermal conductivity such as polyetheretherketone (PEEK). That is, by arranging the heat insulating member  11  having a low thermal conductivity between the treatment member  12 , the medical heater  13 , and the support member  10 , it is possible to efficiently transfer the heat from the medical heater  13  to the treatment member  12 . 
     The treatment member  12  has an elongated shape extending in the longitudinal direction of the gripping portion  7  and is fixed in the recess  111 . 
     The upper surface of the treatment member  12  in  FIGS. 2 and 3  comes into contact with the target site while the target site is gripped by the first and second gripping members  8  and  9 . That is, the upper surface functions as a treatment surface  121  ( FIGS. 2 and 3 ) that applies thermal energy to the target site. In addition, “application of thermal energy to the target site” means transfer of the heat from the medical heater  13  to the target site. In the first embodiment, the treatment surface  121  is formed with a flat surface orthogonal to mutually opposing directions A 1  ( FIGS. 2 and 3 ) in the first and second gripping members  8  and  9  in a case where the first and second gripping members  8  and  9  are set to closed states of gripping the target site. 
     Although the first embodiment is an example in which the treatment surface  121  is formed of a flat surface, the treatment surface  121  is not limited to this and may be formed of other shapes such as a protruding shape or a recessed shape. The same applies to a gripping surface  91  described below. 
     Furthermore, on an installation surface  122  of the treatment member  12 , there is a recess  123  ( FIGS. 2 and 3 ) formed to extend from the proximal end to the distal end of the treatment member  12 . The installation surface  122  forms front and back surfaces of the treatment member  12  with the treatment surface  121 . The treatment member  12  supports the medical heater  13  by the bottom surface of the recess  123 . 
     Examples of the material constituting the treatment member  12  described above include materials with high thermal conductivity, such as copper, silver, aluminum, molybdenum, tungsten, graphite, or a composite material of these. 
       FIGS. 4 to 6  are views illustrating the medical heater  13 . Specifically,  FIG. 4  is a view of the medical heater  13  in a state before a substrate  14  is folded back, as viewed from a first plate surface  14   a  side of the substrate  14 .  FIG. 5  is a cross-sectional view of the medical heater  13  in a state before the substrate  14  is folded back, cut by a plane orthogonal to the width direction (left-right direction in  FIG. 3 ) of the substrate  14 .  FIG. 6  is a cross-sectional view of the medical heater  13  in a state after the substrate  14  is folded back, cut along a plane orthogonal to the width direction of the substrate  14 . 
     The medical heater  13  is a sheet-type heater that partially generates heat when energized. As illustrated in  FIGS. 4 to 6 , the medical heater  13  includes the substrate  14 , a conductive portion  15 , and a passivation film  16  ( FIGS. 5 and 6 ). 
     The substrate  14  is a sheet-like flexible substrate formed of a resin material having electrical insulation such as polyimide. The substrate  14  has an elongated shape, and includes: first and second wide portions  141  and  142  located at either end in the longitudinal direction (in  FIGS. 4 and 5  in the left-right direction); and a narrow portion  143  located between the first and second wide portions  141  and  142  and connecting the first and second wide portions  141  and  142 . 
     Here, the width measurement (length measurement in the up-down direction in  FIG. 4 ) of the narrow portion  143  is set to a substantially uniform measurement in the longitudinal direction. Furthermore, the width measurement in the narrow portion  143  is set smaller than that in the first and second wide portions  141  and  142 . 
     Among the first plate surface  14   a  ( FIGS. 4 to 6 ) and a second plate surface  14   b  ( FIGS. 5 and 6 ) forming front and back surfaces of the substrate  14 , the conductive portion  15  is provided on the first plate surface  14   a . As illustrated in  FIGS. 4 to 6 , the conductive portion  15  includes first and second connecting portions  151  and  152 , a heat generating portion  153 , and an electric path portion  154 . 
     The first and second connecting portions  151  and  152  correspond to the connecting portions according to the disclosure. As illustrated in  FIG. 4 , the first and second connecting portions  151  and  152  are provided on the first and second wide portions  141  and  142 , respectively. That is, the first and second connecting portions  151  and  152  are provided at either end in the longitudinal direction of the substrate  14 , individually. The first and second connecting portions  151  and  152  are individually electrically connected to a pair of lead wires C 1  ( FIG. 6 ) constituting the electric cable C. 
     The heat generating portion  153  is connected, at one end of the heat generating portion  153 , to the first connecting portion  151  and extends, on the other end side of the heat generating portion  153 , linearly toward the second connecting portion  152  side. 
     The electric path portion  154  is a portion provided as an energizing path to the heat generating portion  153 , and is connected, at one end side of the electric path portion  154 , to the other end of the heat generating portion  153 , while extends, on the other end side of the electric path portion  154 , linearly toward the second connecting portion  152  side. Here, one end of the electric path portion  154  connected to the heat generating portion  153  corresponds to a heat generating-side end  154   a  ( FIGS. 4 to 6 ) according to the disclosure. The other end of the electric path portion  154  is connected to the second connecting portion  152 . Note that the second connecting portion  152  and the electric path portion  154  may be formed separately or integrally. That is, the electric path portion  154  is connected from the first and second connecting portions  151  and  152  to the heat generating portion  153  and energizes the heat generating portion  153 . 
     As described above, the conductive portion  15  is provided on the first plate surface  14   a , in a state of being connected in series in the order of the first connecting portion  151 , the heat generating portion  153 , the electric path portion  154 , and the second connecting portion  152  in the longitudinal direction of the substrate  14 . 
     In addition, with the first and second connecting portions  151  and  152 , the heat generating portion  153 , and the electric path portion  154  set to have predetermined total lengths and cross-sectional areas, the heat generating portion  153  is set to have a resistance value that is higher than the values in the other parts in the conductive portion  15 , namely, the first and second connecting portions  151  and  152 , and the electric path portion  154 . Therefore, when a voltage is applied to the first and second connecting portions  151  and  152  via the pair of lead wires C 1  under the control of the control device  3 , the heat generating portion  153  mainly generates heat. 
     Specifically, in the first embodiment, the width measurements (length measurements in the up-down direction in  FIG. 4 ) of the first and second connecting portions  151  and  152 , the heat generating portion  153 , and the electric path portion  154  are set to be the same measurements. Here, the width measurement of the heat generating portion  153  is preferably half or more of the width measurement of the narrow portion  143 . Furthermore, the thickness measurement of the heat generating portion  153  (length measurement in the up-down direction in  FIG. 5 ) is set smaller than the thickness measurement of the first and second connecting portions  151  and  152  and the electric path portion  154 . The thickness measurements of the first and second connecting portions  151  and  152  and the electric path portion  154  are set to be the same. 
     Furthermore, in the first embodiment, by appropriately setting the material, the total length, and the cross-sectional area, the conductive portion  15  is set to have a resistance value (hereinafter, referred to as a heater resistance) 30 [Ω] to 150 [Ω] in the conductive portion  15  at room temperature. Here, the width measurement of the conductive portion  15  (length measurement in the up-down direction in  FIG. 4 ) and the total length of the conductive portion  15  (length measurement in the left-right direction in  FIG. 4 ) are restricted to some extent in accordance the specifications of the treatment tool  2  (specifications of the gripping portion  7 ). Therefore, by controlling the material and thickness measurement of the conductive portion  15  (length measurement in the up-down direction in  FIG. 5 ), the heater resistance at room temperature is set to the above-described value. Specifically, examples of the material constituting the conductive portion  15  include a material containing nickel, specifically, stainless steel, nickel, or a nickel alloy. Furthermore, an exemplary range of the thickness measurement of the heat generating portion  153  is several tens [nm] to several [μm]. 
     The passivation film  16  is constituted with nickel fluoride and covers a part of the surface of the conductive portion  15  as illustrated in  FIG. 5 or 6 . Specifically, the passivation film  16  covers the surface of the heat generating-side end  154   a  and extends from the surface of the heat generating-side end  154   a  to the first connecting portion  151  side so as to cover a part of the surface of the first connecting portion  151 . That is, the passivation film  16  covers the entire surface of the heat generating portion  153 . The passivation film  16  is not limited to the configuration of covering the entire surface of the heat generating portion  153 , and may be configured to cover the surface of the heat generating-side end  154   a  and a part of the surface of the heat generating portion  153 . 
     The medical heater  13  described above is fixed to the bottom surface of the recess  123  by an adhesive sheet  17  ( FIG. 3 ) in a state where the substrate  14  is folded back. 
     Here, the adhesive sheet  17  is located between the bottom surface of the recess  123  and the medical heater  13  so as to adhere the bottom surface and the medical heater  13 . The adhesive sheet  17  is formed by mixing a material having high thermal conductivity, high temperature resistance, and adhesiveness, for example, epoxy resin, with a ceramic having high thermal conductivity, such as alumina and aluminum nitride. 
     As illustrated in  FIG. 6 , the substrate  14  is folded back with reference to a folding line Ln ( FIG. 4 ) which is orthogonal to the longitudinal direction of the substrate  14  and is located substantially in the center of the same longitudinal direction in a state where the first plate surface  14   a  forms an outer surface of the medical heater  13 . In other words, the substrate  14  is folded back in a state where the second plate surface  14   b  is located inside with reference to the folding line Ln. In this state, the first and second wide portions  141  and  142  face each other. The folding line Ln is not limited to a line that is exactly orthogonal to the longitudinal direction of the substrate  14 , but also includes a line that intersects the longitudinal direction within a predetermined angle range. 
     In the following, for convenience of explanation, the region on the first connecting portion  151  side with respect to the folding line Ln will be referred to as a treatment-side region Sp 1 , and the region on the second connecting portion  152  side with respect to the folding line Ln will be referred to as a back-side region Sp 2 . 
     As illustrated in  FIG. 4 , the electric path portion  154  is provided across the folding line Ln. Therefore, the first connecting portion  151 , the heat generating portion  153 , and the heat generating-side end  154   a  are located in the treatment-side region Sp 1 . Furthermore, the second connecting portion  152  and regions of the electric path portion  154  other than the heat generating-side end  154   a  are located in the back-side region Sp 2 . 
     The substrate  14  is folded back with reference to the folding line Ln as described above and is fixed to the bottom surface of the recess  123  with the adhesive sheet  17  in a state where the treatment-side region Sp 1  faces the bottom surface. 
     Configuration of Second Gripping Member 
     The second gripping member  9  has an elongated shape extending in the longitudinal direction of the gripping portion  7 . In the second gripping member  9 , the proximal end side Ar 2  is pivotably supported with respect to the shaft  6  about a fulcrum P 1  ( FIGS. 1 and 2 ). Furthermore, in the second gripping member  9 , the proximal end side Ar 2  is pivotably supported with respect to the movable member  61  about a fulcrum P 2  ( FIGS. 1 and 2 ). That is, the second gripping member  9  pivots about the fulcrum P 1  together with the reciprocation of the movable member  61  along the central axis Ax in accordance with the operation of the surgeon on the operation knob  51 . This operation allows the second gripping member  9  to perform open/close operation with respect to the first gripping member  8 . 
     Here, the lower surface in  FIG. 2  of the second gripping member  9  functions as the gripping surface  91  to grip the target site, together with the treatment surface  121 . In the first embodiment, the gripping surface  91  is formed as a flat surface orthogonal to the directions A 1 . 
     The first embodiment has described an exemplary configuration in which the first gripping member  8  (support member  10 ) is fixed to the shaft  6 , and the second gripping member  9  is pivotally supported by the shaft  6 . However, the disclosure is not limited to this configuration. For example, it is allowable to adopt a configuration in which both the first and second gripping members  8  and  9  are pivotally supported with respect to the shaft  6 , and the first and second gripping members  8  and  9  perform open/close operation by pivot movements individually. Furthermore, for example, it is also allowable to adopt a configuration in which the first gripping member  8  is pivotally supported with respect to the shaft  6  while the second gripping member  9  is fixed to the shaft  6 , and the first gripping member  8  performs open and close operations with its pivot movement with respect to the second gripping member  9 . 
     Configuration of Control Device and Foot Switch 
     The foot switch  4  is a part operated by the surgeon with own foot. Treatment control performed by the control device  3  is executed in accordance with the operation on the foot switch  4 . 
     Note that, the device used for execution of the treatment control is not limited to the foot switch  4 , and other devices such as manual operation switches or the like may be employed. 
     The control device  3  includes a central processing unit (CPU) or the like, and executes treatment control of controlling the treatment tool  2  to operate in accordance with a predetermined program, thereby performing treatment of a target site. 
     Operation of Treatment System 
     Next, operations of the treatment system  1  described above will be described. 
     The surgeon holds the treatment tool  2  by hand and inserts the distal end (a part of the gripping portion  7  and the shaft  6 ) of the treatment tool  2  into the abdominal cavity through the abdominal wall using a trocar, for example. The surgeon also operates the operation knob  51 . The surgeon grips the target site by the gripping portion  7 . Thereafter, the surgeon operates the foot switch  4 . Subsequently, the control device  3  executes the following treatment control. 
     The control device  3  applies a voltage to the first and second connecting portions  151  and  152  via the pair of lead wires C 1 . Here, the control device  3  measures the heater resistance based on the voltage value and the current value supplied to the conductive portion  15  by using a voltage drop test method, for example. Furthermore, the control device  3  refers to resistance temperature characteristics measured in advance. The resistance temperature characteristics are characteristics indicating a relationship between the heater resistance and the temperature of the heat generating portion  153  (hereinafter referred to as the heater temperature). The control device  3  controls the heater resistance to a target resistance value corresponding to the target temperature in the resistance temperature characteristics while changing the electric power supplied to the conductive portion  15 . With this control, the heater temperature is controlled to the target temperature. That is, the heat from the heat generating portion  153  controlled to the target temperature is transferred to the target site through the treatment member  12 . 
     The treatment control described above makes it possible to achieve incision with coagulation in the target site. 
     Treatment Tool Manufacturing Method 
     Next, a method for manufacturing the above-described treatment tool  2  will be described. 
       FIG. 7  is a flowchart illustrating a method of manufacturing a treatment tool  2 .  FIGS. 8A to 8D  and  FIG. 9  are views illustrating a method of manufacturing the treatment tool  2 . Specifically,  FIGS. 8A to 8D  are views that correspond to  FIG. 5 .  FIG. 9  is a view that corresponds to  FIG. 4 . 
     First, as illustrated in  FIG. 8A , an operator performs electroless plating to form a first metal film  101  extending in the longitudinal direction of the substrate  14  on the first plate surface  14   a  of the substrate  14  (step S 1 ). The first metal film  101  is constituted with a material containing nickel, specifically, stainless steel, nickel, or nickel alloy. 
     After step S 1 , the operator uses masking tape MT 1  ( FIG. 8B ) to mask a second region MA 1  ( FIG. 8B ) between first regions Sp 3  and Sp 4  ( FIG. 8B ) on the first metal film  101  spaced apart from each other in the longitudinal direction of the substrate  14  (step S 2 ). 
     After step S 2 , as illustrated in  FIG. 8C , the operator uses electroplating to form a pair of second metal films  102  onto the first regions Sp 3  and Sp 4  on the first metal film  101  (step S 3 ). Thereafter, the operator removes the masking tape MT 1  as illustrated in  FIG. 8D . 
     The first and second metal films  101  and  102  are constituted as the conductive portion  15  as illustrated in  FIG. 8D . Furthermore, the second region MA 1  on the first metal film  101  is constituted as the heat generating portion  153 . Furthermore, the first regions Sp 3  and Sp 4  and the pair of second metal films  102  on the first metal film  101  are constituted as the first and second connecting portions  151  and  152  and the electric path portion  154 , respectively. The second connecting portion  152  and the electric path portion  154  may be formed separately or integrally as described above. 
     After step S 3 , the operator uses masking tape MT 2  ( FIG. 9 ) to mask the regions excluding the region where the passivation film  16  is provided, specifically in the present embodiment, regions excluding the surface of the heat generating portion  153  and the surface of the heat generating-side end  154   a  (step S 4 ). In  FIG. 9 , for convenience of explanation, a third region MA 2  masked by the masking tape MT 2  is represented by hatched lines. 
     After step S 4 , the operator places the substrate  14  in an atmosphere of a gas containing fluorine and performs heating at a predetermined temperature so as to perform surface modification of the region on the surface of the conductive portion  15  other than the masked third region MA 2  (step S 5 ). With this process, as illustrated in  FIG. 5 , the passivation film  16  constituted with nickel fluoride is formed in the regions other than the masked third region MA 2 , that is, on the surface of the heat generating portion  153  and the surface of the heat generating-side end  154   a . Thereafter, the operator removes the masking tape MT 2 . 
     Note that in a case of forming the passivation film  16  on a part of the surface of the heat generating portion  153  and the surface of the heat generating-side end  154   a , it is only needed to mask regions excluding a part of the surface of the heat generating portion  153  and the surface of the heat generating-side end  154   a.    
     After step S 5 , as illustrated in  FIG. 6 , the operator folds back the substrate  14  in a state where the first plate surface  14   a  constitutes the outer surface with reference to the folding line Ln so as to achieve formation of the medical heater  13 . Furthermore, with a posture in which the folding line Ln is located on the distal end side Ar 1  and in a state where the treatment-side region Sp 1  faces the bottom surface of the recess  123 , the operator fixes the medical heater  13  onto the bottom surface by the adhesive sheet  17  (step S 6 ). 
     According to the first embodiment described above, the following effects are obtained. 
     In the medical heater  13  according to the first embodiment, the conductive portion  15  is provided on the first plate surface  14   a , in a state of being connected in series in the order of the first connecting portion  151 , the heat generating portion  153 , the electric path portion  154 , and the second connecting portion  152  in the longitudinal direction of the substrate  14 . Furthermore, the substrate  14  is folded back with reference to the folding line Ln in a state where the first plate surface  14   a  constitutes the outer surface of the medical heater  13 . 
     That is, the substrate  14  having electrical insulation is present between the treatment-side region Sp 1  in the conductive portion  15  and the back-side region Sp 2  in the conductive portion  15 . This makes it possible to prevent an occurrence of short circuit between the treatment-side region Sp 1  in the conductive portion  15  and the back-side region Sp 2  in the conductive portion  15 . 
     Furthermore, the conductive portion  15  has a configuration extending in the longitudinal direction (left-right direction in  FIG. 4 ) of the substrate  14 . The substrate  14  is folded back with reference to the folding line Ln, thereby allowing the treatment-side region Sp 1  in the conductive portion  15  and the back-side region Sp 2  in the conductive portion  15  to be arranged in parallel to each other in the directions A 1 . That is, there is no need to arrange the two electric paths in parallel in the width direction of the substrate  14 , making it possible to reduce the width measurement of the substrate  14 . 
     Meanwhile, in the medical heater described in US 2015/0327909 A, the heat generating portion has a shape extending while meandering in a wavy shape in order to increase the resistance value of the heat generating portion. That is, the known technique has a reduced width measurement of the heat generating portion with the elongated total length of the heat generating portion. In such a configuration, when the heat generating portion is covered with the adhesive sheet, a void might be formed between the peaks or between valleys of the wavy shape in the heat generating portion. Heating the heat generating portion with the void might produce a state in which the heat is trapped in the void, causing overheating in the part of the heat generating portion in proximity to the void, leading to disconnection of the part. 
     Fortunately, however, in the medical heater  13  according to the first embodiment, the thickness measurement of the heat generating portion  153  is smaller than that of the first and second connecting portions  151  and  152  and the electric path portion  154 . That is, it is possible to reduce the cross-sectional area of the heat generating portion  153 , eliminating the need to have a wavy shape of the heat generating portion as described in US 2015/0327909 A, enabling the width measurement of the heat generating portion  153  to be set to the large width measurement same as the measurements of the first and second connecting portions  151  and  152  and the electric path portion  154 . Therefore, by achieving the setting of large width measurement of the heat generating portion  153 , it is possible to avoid disconnection of the heat generating portion  153 . 
     Furthermore, in the medical heater  13  according to the first embodiment, the heat generating portion  153  is constituted with a material containing nickel. 
     Furthermore, the surface of the heat generating portion  153  is covered with the passivation film  16  constituted with nickel fluoride. 
     Here, it is assumed a case where in the course of the use of the treatment tool  2 , a part of the medical heater  13  has been removed from the bottom surface of the recess  123 , leading to a state where a part of the treatment-side region Sp 1  on the first plate surface  14   a  is exposed in the recess  123 . Even in this case, since the surface of the heat generating portion  153  is covered with the passivation film  16 , it is possible to suppress the corrosion or oxidation of the heat generating portion  153  or occurrence of rusting on the heat generating portion  153  that would cause a change in the resistance temperature characteristics measured in advance. That is, even when the treatment tool  2  is used for a long period of time, the heater temperature can be controlled to the target temperature by using the resistance temperature characteristics measured in advance. 
     In particular, the heat generating portion  153  is constituted with a material containing nickel. The passivation film  16  is constituted with nickel fluoride. 
     Therefore, by exposing the surface of the heat generating portion  153  to an atmosphere containing fluorine, the passivation film  16  is formed by surface modification of the heat generating portion  153 . That is, there is no need to provide a special device using a chemical vapor deposition or the like in the formation of the passivation film  16 , making it possible to reduce the manufacturing cost of the medical heater  13 . Furthermore, since the passivation film  16  is formed by surface modification of the heat generating portion  153 , the passivation film  16  can be a dense film, and this enables an extremely small thickness measurement of the passivation film  16 . Therefore, the passivation film  16  would not deteriorate the thermal conductivity from the heat generating portion  153  to the treatment member  12 . That is, the treatment performance of the target site would not deteriorate. 
     Furthermore, in the medical heater  13  according to the first embodiment, the electric path portion  154  is provided across the folding line Ln. That is, in the state where the substrate  14  is folded back with reference to the folding line Ln, the electric path portion  154  is folded back. Here, the electric path portion  154  has a larger thickness measurement than the heat generating portion  153 . Therefore, as compared with the case where the heat generating portion  153  is folded back, it is possible to suppress the disconnection of the conductive portion  15 , and thus possible to sufficiently ensure the durability of the conductive portion  15 . 
     Furthermore, in the medical heater  13  according to the first embodiment, the passivation film  16  covers not merely the surface of the heat generating portion  153  but also the surface of the heat generating-side end  154   a  of the electric path portion  154 . Here, the heat generating-side end  154   a  is a portion connected to the heat generating portion  153 , and thus, likely to have a high temperature. That is, in the course of use of the treatment tool  2 , corrosion or oxidation of the heat generating-side end  154   a  and rusting at the heat generating-side end  154   a  are likely to occur. 
     Therefore, by covering the surface of the heat generating-side end  154   a  with the passivation film  16 , it is possible to suppress corrosion or oxidation of the heat generating-side end  154   a  or occurrence of rusting on the heat generating-side end  154   a  that can cause a change in the resistance temperature characteristics measured in advance. That is, even when the treatment tool  2  is used for a long period of time, the heater temperature can be controlled to the target temperature by using the resistance temperature characteristics measured in advance. 
     Furthermore, in the first embodiment, formation of the conductive portion  15  is performed by forming the first metal film  101  on the first plate surface  14   a  by electroless plating (step S 1 ), and by forming the pair of second metal films  102  on the first metal film  101  by electroplating (step S 3 ). 
     This facilitates formation of the heat generating portion  153 , the first and second connecting portions  151  and  152 , and the electric path portion  154  having different thickness measurements from each other. 
     Second Embodiment 
     Next, a second embodiment will be described. 
     In the following description, identical reference numerals are given to the components similar to those in the first embodiment described above, and detailed description thereof will be omitted or simplified. 
       FIG. 10  is a view illustrating a medical heater  13 A according to the second embodiment. Specifically,  FIG. 10  is a view that corresponds to  FIG. 6 . 
     As illustrated in  FIG. 10 , the medical heater  13 A according to the second embodiment has a difference in that a cover member  18  is added, compared with the medical heater  13  in the first embodiment described above. 
     The cover member  18  is provided across the folding line Ln on the first plate surface  14   a  of the substrate  14 . Specifically, the cover member  18  extends from a position at which a predetermined gap is provided toward the second connecting portion  152  side from the passivation film  16 , onto the second connecting portion  152  side so as to cover the surface of the electric path portion  154 . That is, the cover member  18  covers regions of the electric path portion  154  other than the heat generating-side end  154   a.    
     Examples of the cover member  18  described above include a material having electrical insulation, such as a coverlay film, a sealing material, a melt layer of polyimide. 
     According to the second embodiment described above, the following effects are obtained in addition to the effects similar to the case of the first embodiment described above. 
     The medical heater  13 A according to the second embodiment includes the cover member  18 . 
     Therefore, with the presence of the cover member  18 , it is possible to improve the watertightness of the back-side region Sp 2  in the conductive portion  15 . Furthermore, since the cover member  18  has electrical insulation, it is possible to prevent an occurrence of a short circuit between the treatment-side region Sp 1  in the conductive portion  15  and the back-side region Sp 2  in the conductive portion  15  even when a liquid enters the recess  111 . 
     Furthermore, the cover member  18  covers regions of the electric path portion  154  other than the heat generating-side end  154   a . That is, since the cover member  18  is provided at a position avoiding the heat generating-side end  154   a , which is likely to have a high temperature, there will be no concern about a case where the cover member  18  has a high temperature, making it possible to prevent the removal of the cover member  18  from the first plate surface  14   a.    
     Other Embodiments 
     While the above is description of the modes for carrying out the disclosure, the disclosure should not be limited by only the first and second embodiments described above. 
     Although, in the above-described first and second embodiments, a configuration in which thermal energy is applied to the target site is adopted, the disclosure is not limited to this. It is also allowable to adopt a configuration in which high frequency energy or ultrasonic energy is applied in addition to the thermal energy. Note that, “applying high frequency energy to the target site” means sending a radio frequency current through the target site. Furthermore, “applying ultrasonic energy to the target site” means applying ultrasonic vibration to the target site. 
     In the above-described first and second embodiments, the medical heaters  13  or  13 A according to the disclosure is provided only on the first gripping member  8 . However, the disclosure is not limited to this, and the medical heaters  13  or  13 A according to the disclosure may be provided on both of the first and second gripping members  8  and  9 . 
     In the above-described first and second embodiments, an example in which a material containing nickel is used as the material constituting the conductive portion  15  is exemplified. However, the disclosure is not limited to this, and another material can be adopted as long as it is any of stainless steel, nickel, nickel alloy, palladium, platinum, gold, and silver, or a combination of these. 
     In the above-described first and second embodiments, the first and second metal films  101  and  102  are formed by electroless plating and electroplating, respectively. However, the film formation is not limited to this and the films may be formed by sputtering. 
     According to the medical heater, the treatment tool, and the treatment tool manufacturing method according to the disclosure, it is possible to reduce a width measurement of a substrate, while preventing the short circuit of the conductive portion provided on the substrate. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.