Abstract:
The present disclosure relates to systems and methods for regulating, maintaining and/or controlling the temperature of fluids and tissues during therapeutic or ablative tissue treatment applications. In particular, the present disclosure relates to a multi-purpose subassembly that is easy to use, supports all infusion and fluid-cooled ablation systems, and readily and reliably accepts a variety of tubing designs to decrease preparation time and minimize user error during setup and use.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims benefit of U.S. Provisional Patent Application No. 62/238,299 filed Oct. 7, 2015 and is hereby incorporated by reference. 
     
    
     FIELD 
       [0002]    The present disclosure relates generally to systems and methods for therapeutic or ablative tissue treatment applications. Specifically, the present disclosure relates to systems and methods for regulating, maintaining and/or controlling the temperature of fluids and tissues during such applications. 
       BACKGROUND 
       [0003]    Using ablation technology to treat human tissue is currently known in the art. Ablation technology, such as radiofrequency (RF), microwave, and irreversible electroporation (IRE)—including thermal IRE and non-thermal IRE—are well-known for their applicability in treatment, coagulation and/or targeted ablation or treatment of tissue in the human body. During procedures using such technology, a treatment probe, commonly either an electrode or antenna, is typically advanced into the patient laproscopically, percutaneously or through an open surgical incision until the target tissue is reached. Once properly positioned at the target site, energy is transferred to the probe. The type, amount, and range of energy delivered to the probe varies and depends on the specific treatment modality. During transmission of treatment energy to the target tissue, the outer surface of the probe and/or the cables transmitting the energy may reach high temperatures specifically when the treatment energy is in the form of either RF or microwave energy. When exposed to such elevated temperatures, the treatment site, as well as the surrounding tissue, may be unintentionally heated beyond the desired treatment parameters or treatment zone. Cooling fluid may be circulated through the ablation system to remove excess heat from the probe and/or cable, prevent device malfunctioning and/or avoid unintended harm to the user or patient. To remove excess heat generated by the system, the cooling fluid may be circulated through the ablation system. Commonly, peristaltic pumps, or other similar type pumps known in the art, are used together with inflow and outflow tubing to circulate the cooling fluid. Typically, the cooling system is such that the cooling fluid travels to the probe through inflow tubing that passes through a peristaltic pump head, and returns through outflow tubing that bypasses the peristaltic pump head. Examples devices and apparatuses for thermal treatment of tissues and their operation are described in U.S Patent Application Publication Nos. 20130197504 and 20140207133 and U.S. Pat. Nos. 8,540,710 and 9,084,619, the contents of which are incorporated herein by reference as though set forth in full. 
         [0004]    In general, such treatment probes as discussed above fall within one of the following categories: 1) infusion probes, 2) fluid-cooled probes and 3) standard probes (i.e., no cooling/infusion). 
         [0005]    Infusion probes introduce saline, or other electrically conductive fluids, into the target site to increase the size of the tissue treatment zone. The infused saline increases tissue conductivity, allowing the energy to propagate farther into the target tissue to provide faster procedure times and larger treatment zones. The saline also minimizes tissue desiccation and charring by conducting energy away from the probe tip where it is most concentrated. This is important since charred and/or desiccated tissue tends to act as an insulator that hinders efficient ablation of the surrounding tissue. Because overheating is generally not an issue with infusion systems, the saline is delivered through a single-lumen tube at a much lower flow rate than required for a fluid-cooled ablation probe. Other infusion devices, such as IRE delivery probes deliver therapeutic agents (e.g., drug-coated nanoparticles, growth factors, etc.) into the target tissue, or require infusion of temperature controlling fluid (such as saline) to prevent unwanted sparking between electrodes that may short out the system and possibly harm the patient. 
         [0006]    Fluid-cooled ablation probes include a closed fluid channel through which saline or gas circulates to dissipate heat away from the probe tip where the treatment energy is concentrated. As with infusion probes, the circulating coolant prevents tissue desiccation and/or charring that would interfere with ablation of the target tissue. Since the circulating coolant does not enter the tissue there is no “enhanced conduction” of the treatment energy. 
         [0007]    The different flow rates and tubing designs required for infusion and fluid-cooled ablation systems often require specifically designed peristaltic pumps that are not amenable for multi-purpose use. Peristaltic pumps for infusion ablation systems may not be robust enough to support the higher fluid flow rates required for fluid-cooled ablation systems. For example, a typical infusion ablation system may require infusion fluid to be delivered at a flow rate of 0.05-0.7 ml/min, while a typical fluid-cooled ablation system may require coolant to be circulated at a flow rate in excess of 80 ml/min. Additionally, peristaltic pumps for fluid-cooled ablation systems include complex routing paths for inflow vs. outflow tubing, which complicates setup and increases the likelihood of user error. 
         [0008]    There is a need for a multi-purpose subassembly that is easy to use, supports all infusion and fluid-cooled ablation systems and readily and reliably accepts a variety of tubing designs to decrease preparation time and minimize user error during setup and use. 
       SUMMARY 
       [0009]    The present disclosure relates generally to a multiple-use subassembly that supports infusion and fluid-cooled ablation systems for the treatment or ablation of tissue. 
         [0010]    In one aspect, the present disclosure relates to a system for ablating a treatment site, comprising: a multiple-use subassembly comprising a housing that includes an energy source and a pump motor; an integrated pump head may be connected to the pump motor; and an ablation probe may be electrically connected to the energy source by one or more wires. The integrated pump head may include a roller assembly configured to support peristalsis. The system may further include a fluid source fluidly connected to the ablation probe by a length of tubing which passes through the integrated pump head. The integrated pump head may be configured to flow a fluid from the fluid source to the ablation probe through the length of tubing. The tubing may include single-lumen peristaltic tubing, multiple-lumen peristaltic tubing or multi-lumen tubing. The fluid source may include a cooling fluid. In addition, or alternatively, the fluid source may include an electrically conductive fluid, including, for example, sterile saline. The energy source may be capable of generating radiofrequency energy, microwave energy and/or electroporation energy. The multi-lumen tubing may include an inflow lumen and an outflow lumen, wherein the inflow lumen is configured to close when compressed by a roller of the roller assembly and the outflow lumen is configured to remain open when compressed by a roller of the roller assembly. The fluid may flow from the fluid source to the ablation probe through the inflow lumen and return to the fluid source through the outflow lumen. In one embodiment, the fluid may flow through the multi-lumen tubing at a flow rate of at least 60 ml/min; preferably at least 80 ml/min, more preferably at least 100 ml/min and even more preferably at least 120 ml/min. The single-lumen tubing may include an inflow lumen configured to close when compressed by a roller of the roller assembly. The fluid may flow from the fluid source to the ablation probe through the inflow lumen of the single-lumen tubing. The fluid may flow through the single lumen tubing at a flow rate of approximately 0.05 ml/min to approximately 0.7 ml/min. 
         [0011]    In another aspect, the present disclosure relates to dual-lumen tube comprising: an inflow tube comprising an inflow lumen; and an outflow tube comprising an outflow lumen, wherein the inflow lumen is configured to fully close within a peristaltic pump and the outflow lumen is configured to remain open with a peristaltic pump. One or more insulated wire(s) may extend along the length of the multi-lumen tubing between the inflow and outflow tubes. 
         [0012]    In one embodiment, the inflow and outflow tubes may include substantially identical outer diameters (e.g., at least 0.125 inch; at least 0.150 inch; at least 0.175 inch; at least 0.200 inch; at least 0.225 inch; at least 0.250 inch; at least 0.275 inch; at least 0.300 inch). The outer diameter of the inflow tube is equal to the inner diameter of the inflow lumen plus the wall thickness of the of the inflow tube. Similarly, the outer diameter of the outflow tube is equal to the inner diameter of the outflow lumen plus the wall thickness of the outflow tube. While the inflow and outflow tubes of the multi-lumen tubing may include a variety of different internal and external dimensions, the wall thickness of the inflow tube generally remains greater (i.e., larger) than the wall thickness of the outflow tube, and the inner diameter of the inflow lumen generally remains less (i.e., smaller) than the inner diameter of the outflow lumen. By way of non-limiting example, the inner diameter of the inflow lumen may be at least 0.050 inch; at least 0.060 inch; at least 0.070 inch; at least 0.080 inch; at least 0.090 inch. By way of non-limiting example, the wall of the inflow tube may include a thickness of at least 0.050 inch; at least 0.060 inch; at least 0.070 inch; at least 0.080 inch; at least 0.090 inch; at least 0.100 inch; at least 0.110 inch; at least 0.120 inch; at least 0.130 inch; at least 0.140 inch; at least 0.150 inch. By way of non-limiting example, the inner diameter of the outflow lumen may be at least 0.100 inch; at least 0.110 inch; at least 0.120 inch; at least 0.130 inch; at least 0.140 inch; at least 0.150 inch; at least 0.175 inch; at least 0.200 inch. By way of non-limiting example, the wall of the outflow tube may include a thickness of at least 0.010 inch; at least 0.020 inch; at least 0.030 inch; at least 0.040 inch. 
         [0013]    In another embodiment, the outer diameter of the inflow tube may be larger than the outer diameter of the outflow tube. The outer diameter of the inflow tube is equal to the inner diameter of the inflow lumen plus the wall thickness of the of the inflow tube (e.g., at least 0.125 inch; at least 0.150 inch; at least 0.175 inch; at least 0.200 inch; at least 0.225 inch; at least 0.250 inch; at least 0.275 inch; at least 0.300 inch). Similarly, the outer diameter of the outflow tube is equal to the inner diameter of the outflow lumen plus the wall thickness of the outflow tube (e.g., at least 0.050 inch; at least 0.075 inch; at least 0.100 inch). While the inflow and outflow tubes of the multi-lumen tubing may include a variety of different internal and external dimensions, the wall thickness of the inflow tube generally remains greater (i.e., larger) than the wall thickness of the outflow tube, and the inner diameter of the inflow lumen generally remains substantially the same as the inner diameter of the outflow lumen. By way of non-limiting example, the inner diameter of the inflow and outflow lumens may be at least 0.050 inch; at least 0.060 inch; at least 0.070 inch; at least 0.080 inch; at least 0.090 inch. By way of non-limiting example, the wall of the inflow tube may include a thickness of at least 0.050 inch; at least 0.060 inch; at least 0.070 inch; at least 0.080 inch; at least 0.090 inch; at least 0.100 inch; at least 0.110 inch; at least 0.120 inch; at least 0.130 inch; at least 0.140 inch; at least 0.150 inch. By way of example, the wall of the outflow tube may include a thickness of at least 0.010 inch; at least 0.020 inch; at least 0.030 inch; at least 0.040 inch. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and not intended to be drawn to scale. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures: 
           [0015]      FIG. 1  depicts a front view of a multiple-use subassembly, according to one embodiment of the present disclosure. 
           [0016]      FIG. 2  depicts a partial top cross-sectional view of the housing of the multiple-use subassembly of  FIG. 1 . 
           [0017]      FIGS. 3A-B  depict a partial front view of a multiple-use subassembly that includes an integrated pump head configured to circulate cooling fluid from a fluid source to a fluid-cooled ablation probe, according to one embodiment of the present disclosure. 
           [0018]      FIGS. 3C-D  depict a partial front view of a multiple-use subassembly that includes an integrated pump head configured to circulate cooling fluid from a fluid source to a fluid-cooled ablation probe, according to another embodiment of the present disclosure. 
           [0019]      FIG. 3E  depicts a partial front view of a multiple-use subassembly that includes an integrated pump head configured to circulate infusion fluid from a fluid source to an infusion ablation probe, according to yet another embodiment of the present disclosure. 
           [0020]      FIGS. 4A-B  depict a cross-sectional isometric view of a prior art multi-lumen tubing in the uncompressed ( FIG. 4A ) and compressed ( FIG. 4B ) configurations. 
           [0021]      FIGS. 5A-B  depict a cross-sectional isometric view of multi-lumen tubing that includes inflow and outflow tubes in the uncompressed ( FIG. 5A ) and compressed ( FIG. 5B ) configurations, according to one embodiment of the present disclosure. 
           [0022]      FIGS. 6A-B  depict a cross sectional isometric view of multi-lumen tubing that includes inflow and outflow tubes in uncompressed ( FIG. 6A ) and compressed ( FIG. 6B ) configurations, according to another embodiment of the present disclosure. 
           [0023]      FIGS. 7A-B  depict an isometric view of a pump assembly in a fully open configuration ( FIG. 7A ) and with a length of multi-lumen tubing positioned across the roller assembly ( FIG. 7B ), according to one embodiment of the present disclosure. 
           [0024]      FIGS. 8A-D  depict side ( FIGS. 8A, 8C ) and front ( FIGS. 8B, 8D ) cross-sectional views of the multi-lumen tubing of  FIGS. 5A-B  within a pump assembly in a fully closed configuration, according to one embodiment of the present disclosure. 
           [0025]      FIGS. 9A-D  depict side ( FIGS. 9A, 9C ) and front ( FIGS. 9B, 9D ) cross-sectional views of the multi-lumen tubing of  FIGS. 5A-B  within a pump assembly in a fully closed configuration, according to another embodiment of the present disclosure. 
           [0026]      FIG. 10  depicts a side view of a pump assembly in a fully open configuration, according to one embodiment of the present disclosure. 
           [0027]      FIG. 11  depicts a side view of a pump assembly in a partially open configuration, according to one embodiment of the present disclosure. 
           [0028]      FIG. 12  depicts a side view of the anti-swing mechanism of  FIG. 11B  in an unlocked configuration, according to another embodiment of the present disclosure. 
           [0029]      FIG. 13  depicts a side view of the pump assembly in a partially closed configuration, according to one embodiment of the present disclosure. 
           [0030]      FIG. 14  depicts a side view of the pump assembly in a fully closed configuration, according to one embodiment of the present disclosure. 
           [0031]      FIG. 15  depicts an isometric view of the pump assembly in a fully closed configuration, according to one embodiment of the present disclosure. 
           [0032]      FIG. 16  depicts an isometric view of a pump clip configured to engage the outer surface of the multi-lumen tubing, according to yet another embodiment of the present disclosure. 
           [0033]      FIGS. 17-18  depict another embodiment of an improved peristaltic pump design. 
           [0034]      FIGS. 19-20  depict a front view of a multiple-use subassembly, according to one embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    Before the present disclosure is described in further detail, it is to be understood that the disclosure is not limited to the particular embodiments described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting beyond the scope of the appended claims. Unless defined otherwise, all technical terms used herein have the same meaning as commonly understood by one or ordinary skill in the art to which the disclosure belongs. 
         [0036]    As illustrated in  FIG. 1 , the multiple-use subassembly  1  of the present disclosure may include a housing  10 , a power button  12 , a user interface screen  14 , a first set of probe connection points 16 , a second set of probe connection points  18 , a power indicator  20 , a pump connection  22  and a third probe connection points  13 . The pump connection  22  may include a drive shaft, a peristaltic pump or a piston style pump as commonly known in the art. The housing  10  may be made of metal or other suitable material capable of withstanding repeated and multiple uses, normal wear and tear and may be easily cleaned. The user interface screen  14  may include a touch screen computer that displays a GUI operating system designed to help guide the user through preparation and operation of the system. The first 16 , second  18 , and third  13  probe connection points may be either an RF, IRE or microwave energy connection point as commonly known in the art. Alternatively, any of the probe connection points may be used to electrically connect to grounding pads (not shown), as known in the art. Although only three probe connections are shown it is within the conception of this invention to include additional probe connections depending on the number of probes required during use. The power indicator  20  may include an LED or visual identification source to indicate that power has activated the system. 
         [0037]    Also illustrated in  FIG. 1 ., the single-use subassembly of the present disclosure may include a probe  42 , tubing for delivering fluid from the fluid source  52  to the probe  42 , a fluid spike  152  for gaining access to the fluid source, and a flow sensor  120  for giving accurate measurements of flow rate. The probe in the present disclosure is capable of delivering energy including, but not limited to microwave, RF, ultrasound, irreversible electroporation, and reversible electroporation. 
         [0038]      FIG. 2  provides a schematic top cross-section view of the housing  10 , which further includes a pump motor  24 , a power source  26 , an energy source  28  (e.g., energy generator), a circuit board  30  and an electrical connector (not shown). In one embodiment, the energy generator may provide microwave energy. In another embodiment, the energy generator may provide RF energy. In a third embodiment, the energy generator may provide either reversible or irreversible electroporation energy. In a fourth embodiment, the energy generator may provide a combination of RF, microwave, and either reversible and/or irreversible electroporation energy. The power source  26  is connected to a power cord (not shown) and is capable of generating the power required to run the entire multiple-use subassembly, including the interface screen  14 , the pump motor  24 , the circuit board  30  and the energy source  28 . The pump connection  22  ( FIG. 1 ) may be connected to the pump motor  24 , as known in the art. The pump motor  24  may be securely attached to the housing  10  such that at least a portion of the pump connection  22  extends beyond the housing  10  to receive the roller assembly  76  (not shown) of the pump head  70  (not shown), discussed below. The pump motor  24  may include any stepper motor, brushed motor or brushless motor as known in the art. In one embodiment, the pump motor may be a stepper motor that is directly connected to the pump connection. Alternatively, if a brushed or brushless motor (not shown) is used, then such motor may be connected to a gear box (not shown) within the housing. 
         [0039]    The circuit board  30  may include automatically set pre-programmed treatment parameters including, but not limited to, specific power settings, algorithms and flow rates depending on the type of ablation system connected to the multiple-use subassembly. To provide repeatable and reliable procedure endpoints, the circuit board  30  may be controlled by a user interface configured to monitor the temperature at the probe tip in real-time, and automatically adjust the treatment energy delivered to the ablation zone to maintain optimal temperatures during the ablation procedure. The energy source  28  may be configured to provide the electrical energy required for a variety of ablation systems, including, but not limited to, microwave ablation, RF ablation and thermal or non-thermal irreversible electroporation (IRE). For example, a 2.45 GHz microwave generator may supply electrosurgical RF energy for partial or complete coagulation and ablation of soft tissue. Energy is transferred from the energy source  28  to the microwave connection  13  or probe connection  18  connection points ( FIG. 1 ) of the multiple-use subassembly. 
         [0040]    As described herein, the multiple use subassembly  1  may be compatible for use with a variety of fluid-cooled or infusion ablation systems. Depending on the type of ablation system, unique or dedicated probe connection points  18  may be required within the housing  10  of the multiple-use subassembly. For example, one embodiment may include a multiple-use subassembly with dedicated standard RF pin-type electrical connection points. Another embodiment may include a multiple-use subassembly with dedicated microwave electrical connection points. Yet another embodiment may include a multiple-use subassembly with dedicated high voltage electrical connection points (not shown). Alternatively, in another embodiment, the housing of the multiple-use subassembly may include a single universal electrical connection point configured to deliver RF, microwave or IRE ablation energy to the selected ablation probe. The circuit board  30  may be configured to recognize the specific type of ablation system probe as it is plugged into its respective connection point, and automatically set a pre-loaded computer driven software tissue protocol. The type of ablation probe used with the multiple-use subassembly may vary depending on the medical procedure being performed. 
         [0041]    It is a common problem known in the art that the insulated wire(s) transmitting microwave or RF energy from the probe connection points to the ablation probe may conduct heat and cause an increase in temperature that could burn skin and/or tissue or cause other unwanted/unintended damage to the patient and/or user. In one embodiment, the present disclosure provides a cooling system in which the insulated wire(s) are cooled and remain at a safe temperature by circulating a cooling fluid throughout the ablation delivery device using multi-lumen tubing. In addition to cooling the ablation probe the circulating fluid absorbs the heat generated by the wire(s), thereby cooling the wire(s) to prevent thermal injury to the user and/or patient. A minimum flow rate is required to maintain the cooling fluid at a temperature below the maximum permissible skin contact temperature of approximately 48° C. For example, prior to starting the ablation procedure, the temperature of the cooling fluid within the fluid source may range from approximately 5° C. (i.e., chilled) to approximately 22° C. (i.e., room temperature). This temperature may increase to approximately 30° C. during the ablation procedure as the fluid circulates through the system. Assuming a maximum temperature of 30° C., the cooling fluid must circulate through the multi-lumen tubing at a flow rate of approximately 80 ml/min to maintain the coolant below the maximum permissible temperature of 48° C. It is also a common problem known in the art that transmitting IRE energy at certain pulse parameters may cause sparking between electrodes that leads to unwanted complications during a procedure. One possible solution to this problem is the infusion or circulation of temperature controlled fluid through the IRE probe. The advantage of such a design is that the probe does not increase in temperature that would result in unwanted sparking that may short out the system. 
         [0042]    Referring to  FIG. 3A , in one embodiment the multiple-use subassembly of  FIG. 1  may include an integrated peristaltic pump head  70  configured to circulate a fluid  52   a , such as sterile saline at or below room temperature, from a fluid source  50  to an ablation probe  42  through a multi-lumen tubing  60  (i.e., dual-lumen fluid source line). The multi-lumen tubing  60  may be dual-lumen tubing as shown, but more than two lumens are within the conception of this invention. The multi-lumen tubing  60  may include an inflow tube  62  for flowing fluid  52   a  from the fluid source  50  to the fluid-cooled ablation probe  42 , and an outflow (i.e., return) tube  66  for returning the fluid  52   a  to the fluid source  50  for re-cooling and/or re-circulation. Alternatively, the outflow tube  66  may transfer the fluid  52   a  to a waste container (not shown). The fluid-cooled ablation probe  42  may be electrically connected to the probe connection points  18  by one or more insulated wires  46 . As depicted in the enlarged view of  FIG. 3B , at least a portion of the insulated wire(s)  46  coaxially extend along or next to the inflow  62  and outflow  66  tubes of the multi-lumen tubing  60 . In one embodiment, the insulated wire(s)  46  may split from the dual-lumen  60  tubing prior to entering the pump head  70 . In another embodiment, as shown in  FIGS. 3C-D , the wire(s)  46  may remain within multi-lumen tubing  60  along its entire length as it passes through the pump head  70  to the fluid-cooled ablation probe  42 . Referring to  FIG. 3E , in yet another embodiment, the multiple-use subassembly may be used with an infusion ablation system to flow infusion fluid  52   b  from the fluid source  50  to an infusion ablation probe  40  through a dual-lumen tubing  61 . 
         [0043]    Conventional fluid-cooled ablation systems require separate inflow and outflow tubes to circulate cooling fluid. The inflow tube typically passes through the peristaltic pump, as described above, but the cooling fluid returns to the fluid source through a separate outflow tube that bypasses the peristaltic pump. This requires the user to be cognizant of the inflow and outflow tubing as the latter is specifically routed through the system to avoid the peristaltic pump. Although dual-lumen peristaltic tubing is known in the art, the lumens of both tubes are subject to peristalsis and are therefore limited to unidirectional fluid flow. The ability to support unidirectional flow through two (or more) tubes may be beneficial for certain applications, including, for example infusion ablation systems with multiple (e.g., 5 or more) infusion tines each connected to a separate inflow tube. However, currently available multi-lumen tubing, for example, as shown in prior art  FIGS. 4 and 4A , cannot support bi-directional fluid flow (i.e., fluid circulation) without re-routing the outflow tube to bypass the peristaltic pump. If both the inflow and outflow tubing were to be routed through the peristaltic pump, both tubes would completely collapse when subjected to the pressure from the roller assembly  76  of the pump head  70 , also shown in prior art  FIGS. 4 and 4A . The multi-lumen tubing of the present disclosure is unlike previously described multi-lumen tubing in that it includes an inflow tube configured for peristalsis, and an outflow tube positioned within the pump that is not subject to peristalsis because it never fully collapses within the peristaltic pump head. 
         [0044]    Referring to  FIG. 5A , in one embodiment, the multi-lumen tubing  60  of the present disclosure includes an inflow tube  62  and an outflow tube  66  with a substantially identical outer diameter d 1  (e.g., approximately 0.188 in.-0.199 in.). The inflow tube  62  includes an inflow lumen  64  with an inner diameter d 3  (e.g., approximately 0.079 in.) and a wall thickness t 1  (e.g., approximately 0.050-0.060 in.). The outflow tube  66  includes an outflow lumen  68  with an inner diameter d 4  (e.g., approximately 0.125 in.) and a wall thickness t 2  (e.g., approximately 0.031-0.032 in.). An insulated wire(s)  46  may extend along the length of the multi-lumen tubing  60  between the inflow  62  and outflow  66  tubes. It should be appreciated that these tubing dimensions are provided by way of non-limiting example. A variety of tubing dimensions are contemplated by the present disclosure wherein: 1) the outer diameter d 1  of the inflow tube  62  is equal to the inner diameter d 3  of the inflow lumen plus the wall thickness t 1  of the inflow tube; 2) the outer diameter d 1  of the outflow tube  66  is equal to the inner diameter d 4  of the outflow lumen plus the wall thickness t 2  of the outflow tube; 3) the wall thickness t 1  of the inflow tube is greater than the wall thickness t 2  of the outflow tube and 4) the inner diameter d 3  of the inflow lumen is less than the inner diameter d 4  of the outflow lumen. 
         [0045]    Referring to  FIG. 5B , the roller assembly (discussed below) may compress the inflow  62  and outflow  66  tubes from the first outer diameter d 1  to a second outer diameter d 2  (e.g., approximately 0.100 in.). The thicker wall t 1  of the inflow tube  62  causes the inflow lumen  64  to completely collapse, thereby pumping cooling fluid from the fluid source to the ablation probe. By contrast, the thinner wall t 2  of the outflow tube  66  does not cause the outflow lumen  68  to completely collapse, thereby maintaining a continuously open lumen through which the cooling fluid may return from the ablation probe to the fluid source. Accordingly, the tubing configuration shown in  FIGS. 5A and 5B  also provides the ability to support bi-directional flow through the inflow and outflow tubes, both of which can be positioned within the pump head. 
         [0046]    Referring to  FIG. 6A , in another embodiment, the multi-lumen tubing  60  may include an inflow tube  62  with an outer diameter d 1  (e.g., 0.188 in.-0.199 in.) and outflow tube  66  with smaller outer diameter d 2  (e.g., approximately 0.100 in.). The inflow tube  62  includes an inflow lumen  64  with an inner diameter d 3  (e.g., approximately 0.079 in.) and a wall thickness t 1  (e.g., approximately 0.060 in.). The outflow tube  66  includes an outflow lumen  68  with an inner diameter d 4  that is substantially the same as the inner diameter d 3  of the inflow lumen  64  (e.g., approximately 0.079 in.) and a wall thickness t 2  (e.g., approximately 0.031 in.). An insulated wire(s)  46  may extend along the length of the multi-lumen tubing  60  between the inflow  62  and outflow  66  tubes. It should be appreciated that these tubing dimensions are provided by way of non-limiting example. A variety of tubing dimensions are contemplated by the present disclosure wherein: 1) the outer diameter d 1  of the inflow tube  62  is equal to the inner diameter d 3  of the inflow lumen plus the wall thickness t 1  of the outflow tube; 2) the outer diameter d 1  of the outflow tube  66  is equal to the inner diameter d 4  of the outflow lumen plus the wall thickness t 2  of the outflow tube; 3) the wall thickness t 1  of the inflow tube is greater than the wall thickness t 2  of the outflow tube and 4) the inner diameter d 3  of the inflow lumen is substantially the same as the inner diameter d 4  of the outflow lumen. 
         [0047]    Referring to  FIG. 6B , the roller assembly (discussed below) may compress the inflow tube  62  to a second outer diameter d 2  (e.g., 0.100 in.) that forces the inflow lumen  64  to completely collapse, thereby pumping cooling fluid from the fluid source to the ablation probe. The smaller outer diameter d 2  (e.g., 0.100 in.) of the outflow tube  66  is not substantially compressed by the roller assembly, thereby maintaining an open outflow lumen  68  through which fluid may return from the ablation probe to the fluid source. Accordingly, the tubing configuration shown in  FIGS. 6A and 6B  also provides the ability to support bi-directional flow through the inflow and outflow tubes, both of which can be positioned within the pump head. 
         [0048]    As will be understood by those of skill in the art, the multi-lumen tubing described herein may be made from a variety of polymer-based materials of different durometer (i.e., hardness or compressibility), thickness and/or pliability. Non-limiting examples of such materials may include silicone, synthetic or natural rubbers, nylon, vinyl, polyurethanes and polyethylenes, among others. Each tube of the multi-lumen tubing may be simultaneously formed from the same material by a dual-extrusion process. Alternatively, each tube of the multi-lumen tubing may be formed from the same or different materials by a separate single-extrusion process and then bonded together. A wide assortment of reinforcing material may be incorporated within the inflow and/or outflow tube during the extrusion process to increase its durability and/or flexibility. By way of non-limiting example, the tubing may be reinforced with a braided, woven, spiral and/or knitted arrangement of fibers, steel cord or other suitable structures. The wire(s)  46  extending within multi-lumen tubing  60  may be co-extruded along with the inflow  62  and outflow  66  tubes. Alternatively, the multi-lumen tubing  60  may be co-extruded to include a third smaller lumen between the inflow  62  and outflow  66  tubes. The wire(s)  46  may then be inserted into the third lumen after the tubing has been formed. 
         [0049]    In yet another embodiment, the flow of fluid in the inflow and outflow tubes are controlled by varying the durometer of the tubes. For example, the inflow tube may be made of a material with a softer durometer and as such will compress more readily, thereby more easily collapsing the lumen of the inflow tube. Conversely, the outflow tube may be made of a material with a harder durometer that will not compress as easily as the lower durometer material of the inflow tube, thereby allowing the lumen of the outflow tube to remain open when placed under the same pressure as the inflow tube. It is also appreciated that the dimensions of the inflow tubing and outflow tubing can remain the same, but the difference in hardness of the material used on the outflow tubing can have the same effect as the embodiment of  FIGS. 5A /B and  6 A/B. Another advantage of this embodiment would be ease of manufacture of the tubing, as the dimensions of both the inflow and outflow tubing would be identical. 
         [0050]    Referring to  FIG. 7A-14 , one embodiment of the pump head  70  is shown. The pump head  70  may include a body  72 , a face plate  74 , a roller assembly  76 , an occlusion bed  78  and a front cover  82 . The roller assembly  76  is housed within the body  72  and is configured to receive the pump connection  22  of the multiple-use subassembly ( FIG. 1 ). Although the roller assembly  76  includes six rollers  77  (e.g.,  FIG. 7A ), it will be appreciated that the number of rollers may range from two rollers up to nine rollers, or more. The occlusion bed  78  may include a bottom surface  80  comprising a concave portion  80   a  flanked by substantially planar portions  80   b . The concave portion  80   a  includes a substantially hemi-spherical shape configured to align with the corresponding convex profile of the roller assembly  76 . As discussed in greater detail below, the occlusion bed  78  is pivotally coupled to the body  72  of the pump head  70  by a first hinge  84 , and to the front cover  82  by a second hinge  86 . 
         [0051]    Referring to  FIG. 7B , the pump head  70  provides an easy-to-load layout when the occlusion bed  78  and front cover  82  are in the fully open configuration, such that single (not shown) or multi-lumen tubing  60  may be placed across the roller assembly  76  without obstruction. 
         [0052]    Referring to the side cross-sectional view of  FIG. 8A , the pump head  70  may be moved into a fully closed configuration such that the multi-lumen tubing of  FIGS. 4A-B  is in direct contact with the roller assembly  76  and the concave bottom portion  80   a  ( FIG. 7B ) of the occlusion bed  78 . As depicted by the front cross-sectional view of  FIG. 8B  taken about line X 1  ( FIG. 8A ), the inflow  62  and outflow  66  tubes are disposed within the clearance space  71  between the roller assembly  76  and bottom surface  80   a  of the occlusion bed  78 . One or more rollers  77  of the roller assembly  76  may be in direct contact with the inflow  62  and outflow  66  tubes. Importantly, in the configuration depicted in  FIGS. 8A-B , the roller(s)  77  do not substantially compress either of the inflow  62  or outflow  66  tubes, thereby maintaining the respective inflow  64  and outflow  68  lumens in the fully open configuration. Referring to  FIG. 8C-D , as the roller assembly  76  rotates (e.g., in a clockwise direction; see arrow) the roller  77  taken about the line X 2  moves along and compresses each of the inflow  62  and outflow  66  tubes, which are disposed within the clearance space  71  between the roller assembly  76  and bottom surface  80   a  of the occlusion bed  78 . As one of the rollers  77  rotates in to position directly in line with X2, the clearance space  71  between the roller assembly  76  and the bottom surface  80   a  of the occlusion bed is reduced causing contact between the roller and the multi-lumen tubing assembly  60 . As shown in  FIG. 8D , contact pressure from the roller  77  causes the smaller inflow lumen  64  of the inflow tube  62  to completely collapse, thereby pumping cooling fluid from the fluid source to the ablation probe. By contrast, the thinner wall of the outflow tube  66  does not cause the outflow lumen  68  to completely collapse, thereby maintaining a continuously open lumen through which the cooling fluid may return from the ablation probe to the fluid source. As the rollers  77  of the roller assembly  76  repeatedly move along the multi-lumen tubing, the repeated collapsing and re-opening of the inflow lumen  64  pumps cooling fluid throughout the ablation system. Since the outflow lumen  68  never fully collapses, it remains not subjected to the peristaltic effect thereby allowing the cooling fluid to return to the fluid source. 
         [0053]    Referring to the side cross-sectional view of  FIG. 9A , in another embodiment the pump head  70  may be moved into a fully closed configuration such that the inflow tube  62  of the multi-lumen tubing of  FIGS. 5A-B  is in direct contact with the roller assembly  76  and the concave bottom portion  80   a  ( FIG. 9B ) of the occlusion bed  78 . As depicted by the front cross-sectional view of  FIG. 9B  taken about line X 1  ( FIG. 9A ), the inflow  62  and outflow  66  tubes are disposed within the clearance space  71  between the roller assembly  76  and bottom surface  80   a  of the occlusion bed  78 . One or more rollers  77  of the roller assembly  76  may be in direct contact with the inflow  62  tube but not the smaller diameter outflow tube  66 . Importantly, in the configuration depicted in  FIGS. 9A-B , the roller(s)  77  do not substantially compress either of the inflow  62  or outflow  66  tubes, thereby maintaining the respective inflow  64  and outflow  68  lumens in the fully open configuration. Referring to  FIG. 9C , as the roller assembly  76  rotates (e.g., in a clockwise direction; see arrow) the roller  77  taken about the line X 2  moves along and compresses the inflow tubing  62 . The roller  77  may contact, but does not substantially compress, the outflow tube  66 . As discussed above, the larger outer diameter of the inflow tube  62  causes the inflow lumen  64  to completely collapse, thereby pumping cooling fluid from the fluid source to the ablation probe. By contrast, the smaller outer diameter of the outflow tube  66  does not cause the outflow lumen  68  to completely collapse, thereby maintaining a continuously open lumen through which the cooling fluid may return from the ablation probe to the fluid source. As the rollers  77  of the roller assembly  76  repeatedly move along the multi-lumen tubing, the repeated collapsing and re-opening of the inflow lumen  64  pumps cooling fluid throughout the ablation system. Since the outflow tube  66  is not substantially compressed the outflow lumen  68  remains open thereby allowing the cooling fluid to return to the fluid source. 
         [0054]    Referring to  FIGS. 10 and 11 , a side view of the pump head  70  is shown with the occlusion bed  78  being pivotally coupled to the body  72  of the pump head  70  by a first hinge  84 , and to the front cover  82  by a second hinge  86 . The occlusion bed  78  may rotate approximately 90 degrees about the first hinge  84  to move the pump head  70  from a fully open ( FIG. 9 ) to a partially closed ( FIG. 10 ) configuration. In the partially closed configuration the concave portion  80   a  of the occlusion bed  78  encloses the corresponding convex profile of the roller assembly  76 , but the front cover  82  remains in an open configuration. 
         [0055]    Referring to  FIG. 12A , the second hinge  86  includes an anti-swing mechanism that prevents the front cover  82  from being moved to a fully closed configuration until after the occlusion bed  78  is positioned above the roller assembly  76 . As depicted in the enlarged view of  FIG. 12B , the anti-swing mechanism includes a piston  88  slidably disposed within a first cavity  81  on the planar bottom portion  80   a  of the occlusion bed  78 . The top surface  98  of the piston  88  includes a second cavity  89  configured to receive a compression spring  92 . As will be understood by those of skill in the art, the compression spring  92  includes an unconstrained length (not shown) that exceeds the length of the second cavity  89 . The compression spring  92  is disposed within the second cavity  89  of the piston  88  in a partially constrained configuration such that the first end  94  of the compression spring  92  presses against an upper portion  79  of the occlusion bed  78  and the second end  96  of the compression spring  92  presses against an inner surface  89   a  of the piston  88  defined by the second cavity  89 . The force applied by the partially constrained compression spring  92  urges the piston  88  to slide within the first cavity  81  such that a tab  90  on the bottom surface  99  of the piston  88  extends beyond the planar bottom portion  80   a  of the occlusion bed  78 . When the occlusion bed  78  and front cover  82  are in the fully or partially open configuration, the piston  88  is retained within the first cavity  81  by a finger-like projection  91  (e.g., lip, edge, hook etc.) that includes a substantially planar bottom surface  91   a  configured to engage a corresponding planar surface  86   a  of the second hinge  86 . The opposing planar surfaces  91   a ,  86   a  serve as a locking mechanism that prevents the front cover  82  from pivoting about the second hinge  86 . The locking mechanism also retains the piston  88  within the first cavity  81  such that only the tab  90  extends beyond the planar bottom surface  80   a  of the occlusion bed  78 . 
         [0056]    Referring to  FIG. 12 , as the occlusion bed  78  is lowered into position over the roller assembly, the tab  90  of piston  88  contacts a top surface  73  of the face plate  74 . The downward force exerted against the tab  90  forces the piston  88  to slide into the first cavity  81  as the compression spring  92  moves into a more constrained configuration. As the piston  88  slides into the first cavity  81 , the planar bottom surface  91   a  of the finger-like projection  91  disengages the corresponding planar surface  86   a  of the second hinge  86 . As depicted in the cross-sectional ( FIG. 13 ) and isometric ( FIG. 14 ) views, the front cover  82  may rotate at least approximately 90 degrees about the unlocked second hinge  86  to place the pump head  70  in a fully closed configuration. 
         [0057]    As discussed above, peristaltic tubing is designed to compress to the point that the lumen of the inflow tube completely collapses/closes every time a roller passes over its surface. The elastic nature of the peristaltic tubing allows the lumen to re-open as the roller moves off its surface. The repeated collapsing and re-opening creates pressure within the inflow lumen that forces the cooling fluid to flow from the fluid source to the fluid-cooled ablation probe. The cooling fluid then returns to the fluid source for re-cooling and re-circulation through an outflow lumen. The fluid flow rate through the multi-lumen tubing may be controlled by varying the rate at which the roller assembly rotates. Because the multiple-use subassembly is configured for use with infusion and fluid-cooled ablation systems, the pump motor is configured to drive rotation of the pump connection at speeds capable of generating fluid flow rates ranging from 0.05 ml/min to 100 ml/min. 
         [0058]    Infusion ablation systems typically deliver infusion fluid (e.g., sterile saline) to the tissue ablation site at rate of approximately 0.05-0.7 ml/min. Single-lumen peristaltic tubing may be used to deliver the infusion fluid to the ablation probe because there is no need to circulate cooling fluid throughout the system. Although multi-lumen tubing is not required to circulate cooling fluid, infusion ablation systems may still include multiple-lumen peristaltic tubing. For example, infusion ablation probes may include five (or more) infusion tines, with each tine having a dedicated inflow lumen. An advantage of the integrated pump head disclosed herein is the ability of the easy-to-load layout to accept various tubing arrangements across the roller assembly prior to closing the occlusion bed. For example, the dedicated inflow lumens for each of the five separate infusion tines may include multiple tubes attached in a side-by-side configuration for placement across the roller assembly as a single multi-tube unit. Alternatively, the dedicated inflow lumens for each infusion tine may include individual tubes that are placed next to each other across the roller assembly prior to closing the occlusion bed. In one embodiment, the ability of the integrated pump head to receive various tubing configurations may allow the multiple-use subassembly to perform multiple infusion and/or ablation procedures simultaneously. 
         [0059]    Referring again to  FIG. 8B  and/or  FIG. 9B , a clearance space  71  of approximately 0.1-0.2 inches is created between the roller assembly  76  and bottom surface  80   a  of the occlusion bed  78  when the pump head is in the fully closed configuration. As the roller assembly  76  rotates it generates a “pulling” force that tends to draw the multi-lumen tubing through the clearance space  71  in the direction of rotation (i.e., towards the ablation probe). To prevent the tubing from moving (i.e., sliding) within the clearance space  71 , and potentially disrupting the procedure and/or harming the patient, the multiple-use subassembly may further include a pump clip that engages (i.e., locks onto) the outer surface of the tubing adjacent to the pump head. Referring to  FIG. 16 , in one embodiment a dual-lumen pump clip  100  may include opposing planar elements  102  with corresponding apertures  104  configured to receive and frictionally engage the outer surface of the multi-lumen tubing. As shown in  FIG. 1 , the pump clip  100  may be disposed about a portion of the multi-lumen tubing that extends immediately between the pump head and the fluid source (not shown). As the roller assembly rotates, the multi-lumen tubing is pulled in a distal direction, e.g., towards the patient. The pump clip  100  includes a thickness that exceeds that clearance space  71  between the roller assembly and occlusion bed (e.g., greater than 0.2 inches), and therefore serves as a stopping mechanism that prevents the multi-lumen tubing from being drawn through the pump head during the ablation procedure. Other embodiments of the pump clip  100  may be designed to accommodate other tubing configurations such as single or multiple lumen tubing. 
         [0060]    Compared to conventional systems, the multiple-use subassembly described herein includes a small footprint that takes up less space in the procedure room and supports all infusion and fluid-cooled ablation systems. Unlike conventional pump heads that include restricted openings and/or special routing paths, the integrated pump head  70  includes an easy-to-load layout that readily accepts a variety of single and multi-lumen tube designs. The unique multi-lumen tubing  60  design eliminates the need for the user to remain cognizant of which tube is the inflow tube  62  or outflow tube  66  when placing the tubing within the pump head. The spring-loaded front cover  82  and the locking-cam action ( FIGS. 9-13 ) also generates a significant amount of compression force on the relatively hard, multi-lumen tubing  60  with little input force from the end user. Taken together, the easy-to-load layout of the pump head  70  and multi-lumen tubing  60  provide superior performance and ease-of-use, which decreases preparation time and minimizes user error during setup and use. 
         [0061]    Referring to  FIGS. 17-20 , another embodiment of the pump head is shown. This pump head design is intended to work with either single or multiple lumen peristaltic pump tubing, such as the innovative tubing described above. Key features of this new pump design include, solid pump rollers to compress the tubing, self-locking handle that hinges to open and close the bottom-loading occlusion bed, wide opening when occlusion bed  78  is in the open position for easy loading of the tubing onto the occlusion bed  78 , a high torque precision speed direct drive motor  24  with integrated motor controller, and an integrated sensor to detect the status of the pump door in either an open or closed position. Advantages of this new pump head design include increased longevity, reduced noise, high speed operation, improved occlusion bed opening and closing. 
         [0062]    This pump is designed with solid rollers which omit the typical rollers supported on ball bearings that are commonly found in the art. Such solid rollers will improve reliability and reduce the noise of the pump  70  during use. Another advantage of using solid rollers is longevity of the rollers and the ball bearings for the rollers. The increase in longevity will decrease the amount of maintenance of the pump, giving more time and money to the operator. The pump  70  may also have a self-locking handle to open and close the occlusion bed  78  mechanism. This handle may hinge relative to the pump  70  in an up and down, or an in and out direction. The handle provides the user with an ease of use during the operation of loading and unloading the tubing. Commonly known pumps in the art require precise placement of tubing and are often difficult to load, requiring the user to spend additional procedure time with the patient. By providing an easy to use handle that automatically raises and lowers the occlusion bed  78  away from the rollers this will increase ease of set-up and use and also reduce overall procedure time. 
         [0063]    Additionally, the occlusion bed  78  of this pump design may be supported by linear brushings that results in a simple design with few moving parts to increase the reliability and cost effectiveness of the pump design. The occlusion bed  78  may also be grooved to support axisymmetric multi-lumen tubing lateral motion. Axial tracking of dual lumen tubing may lead to pinching and or binding of the dual lumen tube into the rollers, resulting in high wear and/or failure of the tubing material or even stalling of the pump motor. By creating a grooved support in the occlusion bed  78  to reduce this axial tracking such concerns may be alleviated. 
         [0064]    The pump design may also include a rotor assembly that is a direct drive using a servo motor to create a high-torque, low speed pumping mechanism. Such a design will advantageously remove the need for a gear box or a high-speed motor, allowing lower speed operation for a lower, more precise flow rates and quieter operation. Additionally, the motor may be used with an integrated onboard motor controller/driver to enable programmable motor functions, such as ramp up/down, motor actuation profiles, precision speed control. This integrated motor controller/drive may be able to created unique flow rate schemes and/or maintain precision flow rates. The motor controller/drive may be integrated into the capital equipment used in conjunction with the pump  70 , such as a device with bi-directional communication of inputs and outputs. Additionally, a stepper motor could also be used with the integrated controller/driver. The stepper motor would similarly be able to provide a high-torque, low speed solution. 
         [0065]    This pump  70  design may also include integrated sensors. Such sensors may be used to provide the user and system with key information, such as when the occlusion bed  78  is open or closed. Additionally, a flow sensor  120  can be added to the pump design to detect the flow rate of the fluid through the tubing, if there is air in the system, if priming is requiring, or if there is any axial tracking of the dual lumen tubing  60 . The flow sensor  120  can be integrated into the system in several different ways. The flow sensor  120  could be placed solely in fluid communication with the inflow tubing  62 , giving the user accurate flow rates of fluid that is entering the patient or probe  42 , depending on the type of probe  42  being used in conjunction with the system. In another variation, the flow sensor  120  could be placed solely in fluid communication with the outflow tubing  66 , giving the user accurate flow rates of fluid that is leaving the patient or probe  42 , depending on the type of probe  42  being used in conjunction with the system. Finally, there could be a flow sensor  120  placed in fluid communication with both the inflow tubing  62  and the outflow tubing  66 . This variation is beneficial because it gives the user much more information in terms of flow rate. The user would now know the flow rate of fluid going into the patient or probe  42 , as well as the flow rate leaving the patient or probe  42 . Additionally, the user could get an accurate measurement of the flow rate of fluid that was actually delivered to the patient by subtracting the flow rate from the outflow tubing  66  from the flow rate of the inflow tubing  62 . 
         [0066]    All of the systems, assemblies and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the present disclosure has been described in terms of preferred embodiments, it will be apparent to those of skill in the art that variations can be applied to the systems, assemblies and/or methods described herein without departing from the concept, spirit and scope of the disclosure. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the disclosure as defined by the appended claims. 
         [0067]    While embodiments of the disclosure have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the disclosure. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure.