Devices, Systems, and Methods for Release of a Releaseable Device

Abstract

A system and method for thermally severing a connector that couples a releasable device to an end of an elongate shaft using a resistive heating device adjacent to or in contact with the connector. The resistive heating device can be a surface mount chip resistor. First and second conductive elements made of dissimilar metals are coupled to first and second terminals of the resistive device, respectively. The first and second conductive elements serve two functions. The first function is to supply power to the resistive device. The second function is to form part of a split junction thermocouple that monitors the temperature of the resistive device. The temperature of the resistive device is controlled by alternately coupling the first and second conductive elements to a power source and a temperature sensing circuit.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit and priority of U.S. Patent Application No. 18 / 359,301, filed on July 26, 2023, which claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 369,499, filed on July 26, 2022, and the entire contents of each of these applications are incorporated herein by reference in their entirety.

[0002] The present disclosure relates to devices, systems, and methods for implanting a device into a patient's body. More specifically, the present disclosure relates to devices, systems, and methods for thermally severing a connector that couples a releasable device to an end of an elongate shaft using a resistive device / heater adjacent to or in contact with the connector.

Background Art

[0003] An aneurysm is a local bulge in the blood vessel wall caused by weakening of the blood vessel wall. As the size of the aneurysm increases, the risk of rupture increases. Aneurysms can occur in any artery, and particularly adverse examples include brain aneurysms and abdominal aortic aneurysms. Aneurysms can occur in the heart itself after a heart attack, including both ventricular septal aneurysms and atrial septal aneurysms.

[0004] Aneurysms can be treated in various ways, particularly depending on their size and location. Brain aneurysms are often treated using various methods or combinations of methods depending on the type of aneurysm and the individual patient. These methods can include microsurgical clipping, endovascular coiling embolization, endovascular stent - assisted coiling embolization, arterial occlusion and bypass surgery, shunting by stents, and tubular retractor systems. Some of these methods involve the use of interventional devices that are sent into the blood vessels.

[0005] The vascular intervention devices used in these procedures can have a wide variety of configurations, including detachable vascular occlusion balloons and embolization vascular occlusion devices. The embolization vascular occlusion device is placed within an aneurysm arising from a blood vessel to form an embolism within the aneurysm. The device induces coagulation (embolization) of the aneurysm, thus preventing further blood from flowing into the aneurysm and expanding it. Typically, the device comprises a vascular occlusion coil, such as a helical wire coil having windings dimensioned to engage the wall of the blood vessel. Other less rigidly coiled coil-shaped devices, as well as devices including braids, have been described.

[0006] The delivery of such vascular intervention devices has been accomplished by a variety of means, including means via a catheter (the device is pushed through an opening at the proximal end of the catheter by a pusher wire used to deploy the device). The device is radiopaque, and the physician visualizes the position of the device by using a fluoroscopic X-ray system when the device is being introduced. In some cases, the device is manufactured to pass through the lumen of the catheter in a straight shape and then assume a complex shape formed initially after being deployed in a region of interest, such as an aneurysm.

[0007] One conventional releasable endovascular treatment device used to embolize an aneurysm has a polymeric thread that acts as a tether for attaching a coil to a pusher wire. This allows the coil to be positioned within the aneurysm by pushing or pulling the coil via the pusher wire. The polymeric thread extends adjacent to a small electrical heater element at the distal tip of the pusher wire, such that when the heater is energized, the polymeric thread is melted and the coil is released. Once the coil is thus removed from the pusher wire, the coil remains at a predetermined position within the aneurysm, and the assembly of the pusher wire and heater is withdrawn from the body. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The problem with prior art devices is that the heater element is formed from a coil of metal wire, and the resulting resistance has a large tolerance due to variability in the manufacturing process. The high cost of manufacturing and the large tolerance in resistance values mean that the amount of electrical power dissipated in the heater also varies greatly from device to device. This adds further uncertainty to the temperature of the heater element that results when it is energized.

[0009] As shown in FIG. 1, in a prior art device, first and second conductive wires 15, 16 made of copper couple a coil of metal wire 11 to a power source 20. First ends 15a, 16a of wires 15, 16 are coupled to the power source 20, and second ends 15b, 16b of wires 15, 16 are coupled to electrical terminals 12, 13 located at opposite ends of the coil of metal wire 11, respectively. In use, when it is desirable to cut a thread located on or adjacent to the coil metal wire 11, a controller associated with the power source 20 turns the power on for a specified period to cause heating of the metal wire 11. Cutting of the thread generally involves melting of the thread.

Means for Solving the Problem

[0010] Devices, systems, and methods are provided for delivering a releasable device (e.g., a releasable implantable device). The system includes an elongate shaft having a proximal end and a distal end, the distal end being configured to advance into the body. A coupling element (e.g., a polymeric thread) holds the releasable device near the distal end of the elongate shaft until sufficient thermal energy applied thereto causes the coupling element to change and effect release of the releasable device. The coupling element can be any number of objects that are severable by application of heat. A heater (also referred to herein as a "resistive device") disposed within or otherwise coupled to the elongate shaft is configured to apply thermal energy to the coupling element, the thermal energy causing the coupling element to change in response to actuation and releasing the implantable device. A controller is configured to deliver an electrical drive signal to change the state of one or more switches between a first state and a second state to couple the heater to a power source or disconnect it from the power source. That is, when one or more switches are in the first state, power is supplied to the heater, and when one or more switches are in the second state, power is not supplied to the heater.

[0011] In some embodiments, the heater comprises a coil of metal wire that heats sufficiently to sever a thread (e.g., a polymeric thread) or other severable connector when a sufficient amount of current flows through the coil.

[0012] According to other embodiments, the heater comprises a surface mount device resistor (also known as a "chip resistor"). A chip resistor is a passive electronic component designed to limit the flow of current. Conventionally, chip resistors have been used to reduce voltage within an electronic circuit or to maintain a constant current. Chip resistors are widely used in applications such as automotive and transportation, consumer electronics, industrial, and IT and telecommunications. The resistive element of a chip resistor can include, for example, thin film resistors, thick film resistors, and foil resistors. The present invention uses a chip resistor in a manner different from conventional uses, utilizing its resistive element to convert electrical energy into thermal energy so that the chip resistor functions as a heater.

[0013] Thick film and thin film chip resistors used in the electronics industry are available in a variety of package / case sizes such as 0201 (inch size) / 0510 (metric size) package / case size or 0.01005 (inch) / 0402 (metric) package / case size or package / case sizes below 009005 (inch) / 0301 (metric). One advantage of using these commercially available resistors as heaters is that they are available with narrow resistance value tolerances, typically tolerances of + / -1% or better, and as a result, the overall heater resistance value tolerance can be more tightly controlled.

[0014] When using a thermal detachment method to detach an implantable device, instead of raising the temperature of the heater to an approximate temperature depending on a certain amount of energy delivery (a certain power for a specific time, or a certain voltage or current for a specific time) to cut the thermally cuttable connector that moors the implantable device to its delivery platform, it is advantageous to control the heater directly to a specific temperature. This method is susceptible to changes in the ambient thermal environment and can vary the temperature of the heater depending on the circumstances even when the supplied electrical energy is the same. When a constant voltage or constant current is supplied to the heater, the resulting temperature is also susceptible to variations in the electrical resistance of the heater, which is a manufacturing variable that is not fully controllable, especially when the resistance element of the heater is a coiled metal wire.

[0015] Prior art designs using coiled metal resistance elements require adjustment of heater power and duration. If the power is too high or the duration is too long, the plastic delivery system (e.g., the surrounding microcatheter / delivery catheter) may be thermally damaged, thus making it difficult to withdraw the introducer. If the power is too low or the duration is too short, detachment may not necessarily be achievable. For these reasons, according to one aspect, the heater is controlled to a specific temperature or specific temperature range to ensure reliable detachment of the releasable implantable device without causing damage to the delivery system.

[0016] The method of heating to a specific temperature involves measuring the temperature of the heater in a feedback manner and controlling the power sent to the heater to drive the heater to a specific temperature. A feedback method for measuring the temperature of the heater and then controlling the power to the heater to control that temperature to a setpoint / target temperature is possible. The target temperature can be a temperature range such as 200°C ± 20°C.

[0017] According to one aspect of the present invention, first and second conductive elements (also referred to herein as "conductors") made of dissimilar metals (metals having different Seebeck coefficients) are coupled to first and second electrical terminals of a heater, respectively. According to some embodiments, disposed between the first conductive terminal and the second conductive terminal is a resistive element made of a conductive material that becomes hot when current passes through it. As described above, the resistive element can be a coiled metal wire or can be in the form of a thin film resistor, thick film resistor, or foil resistor associated with a chip resistor.

[0018] According to the present invention, the first and second conductive elements serve two functions. The first function is to supply power to a heating device. The second function is to form part of a split-junction thermocouple that monitors the temperature of the heater. The temperature of the heater is controlled by alternately coupling the first and second conductive elements to a power source and a temperature sensing electronic circuit. When a conductive element is coupled to the temperature sensing circuit, a controller associated with the temperature sensing circuit uses the sensed temperature to determine when to couple the first and second conductive elements to the power source. According to some embodiments, the temperature sensing circuit includes a voltage detector to which the ends of the first and second conductive elements can be electrically coupled. A correlation method well known in the art can be performed by the controller to determine the temperature of the heater based on the voltage difference detected by the voltage detector and the temperature of the electronic circuit.

[0019] According to some embodiments, the systems and methods disclosed herein are for delivering a therapeutic releasable device (e.g., an embolization coil) to a treatment site (e.g., the site of an aneurysm) inside a patient. A push wire and a delivery catheter are typically used in the delivery process, along with other tools, and the push wire is configured to convey the releasable device through the lumen of the delivery catheter to the treatment site.

[0020] One design includes first and second conductors that extend from the proximal end (power supply end) of the push wire to the distal end where the releasable implant and heater are disposed. As described above, according to some embodiments, the heater includes a resistive element disposed between first and second electrical terminals to which the first and second conductors are electrically coupled, respectively. Also, as described above, these conductors are made of dissimilar metals and may include, for example, a nickel conductor and a stainless steel conductor. According to some embodiments, a portion of the push wire itself, which may be made of stainless steel, is used for at least a portion of one of the first and second conductors. Advantageously, this allows for the use of only one additional conductive wire to connect the heater to a power source and to connect a thermocouple to a voltage detector that forms part of a temperature sensing circuit. According to this exemplary configuration, there is a dissimilar junction to a stainless steel conductive element on one side of the heater and another dissimilar junction to a nickel conductive element on the other side of the heater. At the proximal end of the push wire assembly, this combination, which acts like a thermocouple, can be measured by a well-known circuit that includes a voltage detector as described above. The reported temperature is intermediate the temperature at the electrical terminals of the heater where the dissimilar junctions occur. The material of the heater is not a problem as long as it is conductive. For example, it may be platinum or another metal or a thick film resistor material.

[0021] When the elongate shaft comprises a push wire, the push wire can be configured in a variety of ways. According to one embodiment, the push wire comprises a hypo tube along substantially its entire length, and the distal end of the hypo tube is electrically coupled to one of the electrical terminals of the heater. According to such an embodiment, the length of one additional conductive wire can pass through the lumen of the hypo tube or, alternatively, can extend entirely outside the hypo tube. According to another embodiment, the push wire comprises a solid core wire having a distal end electrically coupled to one of the electrical terminals of the heater, and one additional conductive wire extends outside the core wire. According to yet another embodiment, the push wire comprises a hypo tube having a distal end to which the solid core wire is mechanically and electrically coupled. According to one such embodiment, the distal end portion of the core wire is tapered and the distal end of the core wire is electrically coupled to one of the electrical terminals of the heater. It should be noted that the push wire used to deliver the embolization coil to the site of the aneurysm is relatively long (in some examples 180 cm) and has a very small diameter profile (e.g., 0.25 millimeters).

[0022] Note that adding a plurality of additional wires more than what is required to supply heater power can complicate the design, add cost to the delivery system, and may even be impossible since the wires have to fit within the very small diameter lumens involved.

[0023] The advantages in applications involving the implantation of a therapeutic device into the human body are that the starting temperature of the resistive device / heater and the conductive elements before energizing the heater is always at the temperature of the body temperature of about 37°C. Since it can be assumed that the starting temperature is within 3°C of 37°C, many errors can be eliminated when determining the temperature of the resistive device / heater. For example, the output of the temperature sensing circuit can be measured before applying power to the heater, which represents the initial value at about 37°C. Then, the set value can be determined as the delta from this initial value. This delta represents a specific temperature difference of the heater from about 37°C. When the heater continues to be powered and reaches the set value and is maintained at the set value, the heater is maintained at a specific absolute temperature that is the delta from about 37°C.

[0024] According to one embodiment, a system is provided that includes an elongated shaft having a distal end to which a releasable device is coupled by a thermally cuttable connector. The system further includes a resistive device / heater that includes a first terminal, a second terminal, and a resistive element disposed between the first terminal and the second terminal and electrically coupled to the first terminal and the second terminal. The thermally cuttable connector is disposed adjacent to or in contact with at least a portion of the resistive element. First and second conductive elements, each having a first end and a second end, are used when connecting the resistive device / heater to a power source or to a voltage detector that forms part of a temperature sensing circuit. The first ends of the first and second conductive elements are electrically coupleable to a power source, and the second ends of the first and second conductive elements are coupled to the first and second terminals of the resistive device / heater, respectively. The first conductive element is made of a first metal, and the second conductive element is made of a second metal different from the first metal. The first and second conductive elements are configured such that a voltage proportional to the temperature difference is induced between the first conductive element and the second conductive element when there is a temperature difference between their respective first ends and second ends.

[0025] The system may further include a control circuit configured to alternately and electrically couple first ends of first and second conductive elements to a power supply and a voltage detector, and by repeatedly electrically coupling the first ends to the voltage detector, control the temperature of a resistive device / heater to a target temperature. The control circuit maintains the first ends of the first and second conductive elements in an electrically coupled state to the voltage detector until the voltage detected by the voltage detector is below a target voltage, when the voltage detected by the voltage detector is greater than or equal to a target voltage corresponding to the target temperature of the resistive device / heater, and when the voltage falls below the target voltage, the first ends are configured to be electrically separated from the voltage detector and electrically coupled to the power supply. The target temperature of the resistive device / heater is selected to be a temperature sufficient to cause a thermally disconnectable connector to disconnect.

[0026] When the first and second conductive elements are electrically coupled to the power supply for the purpose of raising the temperature of the heater, thereafter, the control circuit instantaneously and repeatedly couples the first ends of the first and second conductive elements to the voltage detector to measure the heater temperature. The repeated instantaneous connection of the first ends to the voltage detector continues until the target temperature of the heater is achieved, and after the target temperature of the heater is achieved, the first ends remain connected to the voltage detector until the detected temperature of the heater again falls below the target temperature.

[0027] Some of the metal conductors used in conventional thermocouple applications are not suitable for use in some of the devices and systems disclosed herein. In the applications of the present invention, the first and second conductive elements that form part of the split-junction thermocouple are used not only to carry a current on the order of microamperes when measuring temperature, but also to supply power to a heater, much larger currents (e.g., 10 to 200 milliamperes) must also be carried. Further, when the conductive element is in the form of a wire, the gauge of the wire used is very small (typically 43 AWG or less). Metal conductors with high electrical resistivity (e.g., 0.5 microohm-meter) such as constantan are not suitable for conducting the larger heater currents seen in a thermal plug coil delivery system where the wire length is long and the wire diameter is very small. For example, one concern with using one copper wire and one constantan wire is that the electrical resistivity of constantan is about 30 times that of copper. This means that the constantan wire would need to have about 5 times the diameter of the copper wire to have the same electrical resistance as its adjacent copper wire and carry the current required for the heater. Very thin, high-gauge copper wire (e.g., 43 ga.) is already used to power such heaters in order to fit into a small catheter lumen, and the resistance of existing technology copper wire (half of a two-wire circuit) is typically 12 ohms. Therefore, there is a problem fitting a constantan wire if it has a much larger diameter. For these reasons, in some embodiments, the conductive element for supplying power to the heater is made from another lower resistivity metal such as nickel, which has a resistivity about 4 times that of copper.

[0028] To apply thermal energy to a thread to cut the thread, a winding heater and a chip resistor are suitable, but the chip resistor has many advantages over the winding heater. First, since the coil of the coiled wire heater is usually made of a platinum alloy, the material cost is high, and the manufacturing cost when winding it is also high. The chip resistor is much cheaper and typically costs only a small amount. Another advantage is that the chip resistor is available in a huge number of resistance values that facilitate optimization when designing a system incorporating such a device. The chip resistor can also be made significantly shorter than the winding platinum alloy heater. The winding heaters currently on the market have a length of 0.6 to 1.1 millimeters. On the other hand, the chip resistor can have a length (including its terminals) of 0.3 to 0.4 millimeters. Furthermore, a larger resistance is possible with the chip resistor, which means that less power is wasted in the resistance of the connected wire and more power is delivered to the heater itself. This is very beneficial when the power source is a battery.

[0029] These and other advantages and features will become apparent from the drawings and the detailed description.

Brief Description of the Drawings

[0030]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9A

Figure 9B

[0031] The following description relates primarily to thermally cutting a connector that couples a plug coil to an end of a push wire using a resistive device adjacent to or in thermal contact with the connector. It should be understood that the scope of the present invention is not limited to a plug coil delivery system and is applicable to any system where it is desirable to release a device from the end of an elongate shaft.

[0032] It is important to note that the drawings are not intended to show the system components precisely in detail, but rather to show the general arrangement of the components for the purpose of conveying how the components function collectively to thermally cut a connector that holds a releasable device at the end of an elongate shaft. Also, note that the components shown in the drawings are not to scale.

[0033] In the following description, several types of heaters are disclosed for use in thermally cutting a connector (e.g., a polymer thread / wire) that moors a releasable device (e.g., a plug coil) to the end of an elongate shaft (e.g., a push wire). According to some embodiments, the heater is a wound heater 30 having a coiled resistive element 32 disposed between and electrically coupled to a first conductive terminal 33 and a second conductive terminal 34, as shown in FIG. 2. According to some embodiments, the resistive element includes a platinum alloy wire. According to other embodiments, the heater is a surface mount device resistor (referred to herein as a "chip resistor"). FIGS. 3A and 3B show an exemplary chip resistor 40 including a ceramic substrate 41 having an upper surface on which a resistive layer 42 is supported. As described above, the resistive layer can include any of a number of configurations. At both ends of the resistive layer 42, first and second conductive terminals 43, 44 are disposed, which are electrically coupled to the resistive layer by electrodes 45, 46, respectively. The chip heater further typically includes a protective electrically insulating protective film 47 over the resistive layer 42. An example of a chip resistor suitable for the applications disclosed herein is one manufactured by Yageo with the part number RC0075FS-7N200RP. As will be described in more detail below, in use, the first and second conductive terminals of each of the heaters 30, 40 can be coupled to a power source 120, which passes a current through the resistive elements 32, 42 when the conductive terminals are coupled to the power source.

[0034] FIG. 4 shows a portion of a plug coil delivery system 100 that utilizes a wound heater 30 as shown in FIG. 2. The system includes a conductive push wire 102 that includes a hypo tube 103 having a distal end 103a to which a solid core wire 104 is mechanically and electrically coupled. The distal end of the core wire 104 may or may not be tapered, but in any case includes a distal end 104a that is electrically coupled to a first conductive terminal 33 of the heater 30. An additional conductive element 105 in the form of a wire has a distal end 105a that is electrically coupled to a second conductive terminal 34 of the heater 30. The push wire 102 and the wire 105 are electrically insulated from each other and include proximal ends that are each connected to a control circuit 700 configured to control the temperature of the heater 30. Further, according to some embodiments, at least a portion of the length of the wire 105 preferably passes through the lumen of the hypo tube 103 and enters the lumen through an aperture 103b that is disposed along the distal end of the hypo tube. According to other embodiments, the wire 105 may be entirely outside of the hypo tube 103.

[0035] According to one embodiment, each of the hypo tube 103 and the core wire 104 of the push wire 102 includes stainless steel, and the additional conductive element 105 includes nickel. The plug coil 120 is mechanically coupled to the distal end of the core wire 104 by a thermally cuttable connector 110 (e.g., a polymer thread) that extends through a retention ring 111 associated with the plug coil. In FIG. 4, the cuttable connector 110 is positioned adjacent to the resistive element 32 of the heater 30. According to other embodiments, the cuttable connector 110 is in physical contact with the resistive element 32. The purpose is to control the temperature of the heater 30 to a target temperature (or temperature range) sufficient to cause the thermally cuttable connector 110 to be cut when the plug coil 120 is introduced into the aneurysm.

[0036] A prominent feature of the systems and methods disclosed herein is that the conductive element that supplies power to the heater is made of dissimilar metals. This allows the conductor to perform two functions. The first function is to supply power to the heater terminals. The second function is to form part of a split-junction thermocouple used to monitor the temperature of the heater. This enables the temperature of the heater to be controlled by a control circuit 700 as shown in FIGS. 9A and 9B. The control circuit 700 is configured to alternately couple the proximal ends of the conductive elements 102, 105 to a power source 720 and a voltage detector 710.

[0037] Referring particularly to FIGS. 4 and 9A - 9B, the proximal ends (or proximal end portions) 102b, 105b of the push wire 102 and the wire 105 are coupled to the inlet terminals 704a, 705a of switches 704, 705 within the control circuit 700, respectively. The switches 704, 705 are controlled by a controller 702 to transition between a first state and a second state. The first state is shown in FIG. 9A, in which the switches 704, 705 couple the proximal ends 102b, 105b of the push wire 102 and the wire 105 to the terminals 720a, 720b of the power source 720, respectively. The second state is shown in FIG. 9B, in which the switches 704, 705 couple the proximal ends 102b, 105b of the push wire 102 and the wire 105 to the terminals 710a, 710b of the voltage detector 710, respectively.

[0038] The control circuit 700 is configured to repeatedly and electrically couple the push wire 102 and the wire 105 to the voltage detector 710 so that it can monitor the temperature of the heater 30 and determine whether the heater 30 is operating at a temperature higher than or lower than the target temperature. The control circuit 700 is configured such that when the voltage detected by the voltage detector 710 is equal to or higher than the target voltage corresponding to the target temperature, the switches 704, 705 take a second state for connecting the push wire 102 and the wire 105 to the voltage detector 710. The switches 704, 705 remain in their second state until the voltage detected by the voltage detector drops below the target voltage. When the voltage detected by the voltage detector drops below the target voltage, the switches transition to the first state and electrically couple the push wire 102 and the wire 105 to the power supply 720.

[0039] When the switches 704, 705 take the first state, the control circuit 700 is configured to instantaneously and repeatedly transition the switches to the second state to monitor the temperature of the heater 30 as the temperature rises. The repeated and instantaneous transition of the switches 704, 705 to the second state continues until the target temperature of the heater is achieved. After the target temperature of the heater is achieved, the switches 704, 705 remain in the second state until the detected temperature of the heater drops below the target temperature.

[0040] In the embodiments of FIGS. 9A and 9B, when switches 704, 705 are in the second state, conductive elements 102, 105 are coupled to a voltage amplifier 711 that amplifies the voltage induced between the proximal end of push wire 102 and the proximal end of wire 105. The output of voltage amplifier 711 is input to a voltage detector 710, and the amplified voltage is compared, for example, to a target voltage corresponding to the target temperature of heater 30. According to one embodiment, when the input voltage to voltage detector 710 becomes lower than the target voltage (which indicates that the temperature of heater 30 is lower than the target temperature), an output signal 750 is generated and sent to controller 702, where output signal 750 is processed such that the controller outputs a control signal 752 that causes switches 704, 705 to assume the first state and enables the power source to operate heater 30. On the other hand, when the input voltage to voltage detector 710 becomes greater than or equal to the target voltage (which indicates that the temperature of heater 30 is greater than or equal to the target temperature), another output signal 751 is generated and sent to controller 702, where output signal 751 is processed such that the controller outputs a control signal 753 that causes switches 704, 705 to assume the second state or to remain in the second state.

[0041] According to some embodiments, controller 702 includes a processor 702a and a memory 702b that stores instructions executed by the processor. Processor 702a uses the data and / or instructions stored in memory 702b to process signals 750 / 751 and determine the type of control signal 752 / 753 output by the controller. According to some embodiments, controller 702 further includes a clock 702c that can be used by the controller to switch switches 704, 705 between the first state and the second state at a fixed rate (e.g., a 200 Hz rate) in a duty cycle such that the power source is coupled to push wire 102 and wire 105 for 4.5 milliseconds of each duty cycle and the thermocouple (formed by push wire 102 and wire 105) is coupled to the voltage detector for 0.5 milliseconds of each duty cycle. Other duty cycles and intervals are contemplated.

[0042] The system of FIG. 5 is similar to the system of FIG. 4, except that the heater is the chip resistor 40 as shown in FIGS. 3A and 3B, the distal end 104a of the core wire is coupled to the conductive terminal 43, and the distal end 105a of the wire 105 is coupled to the conductive terminal 44.

[0043] The system of FIG. 6 is a variant of the system of FIG. 5. The push wire 102 comprises a hypodermic tube 203 substantially along its entire length, and the distal end 203a is coupled to the conductive terminal 43 of the heater 40. Further, the distal end 105a of the wire 105 is coupled to the conductive terminal 44 of the heater 40. According to such an embodiment, the length of the wire 105 may pass through the lumen of the hypodermic tube 203, or alternatively, may extend completely outside the hypodermic tube. When at least a portion of the length of the wire 105 passes through the lumen of the hypodermic tube 203, the wire can enter the lumen through a side opening 203b or other opening of the hypodermic tube.

[0044] According to another embodiment, as shown in FIG. 7, the entire push wire 102 comprises a solid core wire 204 having a distal end 204a that is coupled to the conductive terminal 43 of the heater 40. Further, the distal end 105a of the wire 105 is coupled to the conductive terminal 44 of the heater 40.

[0045] In the above example, the push wire 102 is conductive because its distal end is coupled to one of the conductive terminals of the heater 30 (FIG. 4) or the heater 40 (FIGS. 5-7). However, according to other embodiments, as in the system shown in FIG. 8, a pair of conductive wires 205, 105 made of dissimilar metals are coupled to heater terminals 43, 44 that are connected to inlet terminals 704a, 705a of switches 704, 705 located within the control circuit 700, respectively. In the embodiment of FIG. 8, wire 205 is used instead of push wire 102 to supply power to heater 40 when switches 704, 705 are in the first state. Wire 205 is further used instead of push wire 102 to form a thermocouple with wire 105 when switches 704, 705 are in the second state. In all other respects, the temperature of heater 40 is adjusted according to one or more of the control methods described above.

[0046] It should be understood that the scope of the present invention is not limited to the specific embodiments disclosed herein and that various modifications can be made without departing from the spirit and scope of the present invention. For example, the present invention is not limited to the conductive materials disclosed herein, nor is it limited to the arrangements shown in the drawings. Further, the present invention encompasses heater types other than the coil type and the chip resistor type. Further, it is understood that the control methods disclosed herein can be implemented using controllers other than the types disclosed herein.

[0047] The following sections disclose additional implementation aspects.

[0048] (1) An elongated shaft having a distal end, A releasable device coupled to the distal end of the elongated shaft by a thermally cuttable connector, A resistor device including a first terminal, a second terminal, and a resistor element disposed between the first terminal and the second terminal and electrically coupled to the first terminal and the second terminal, wherein a thermally cuttable connector is adjacent to or in thermal contact with at least a portion of the resistor, preferably in thermal contact with the resistor element (thermal contact means that the thermally cuttable connector is in contact with a part of the resistor device, or more precisely, in contact with the resistor element, and further means that the thermally cuttable connector is thermally coupled to a part of the resistor device, or more precisely, thermally coupled to the resistor element, and being thermally coupled is understood to include heat transfer by any of conduction, convection, and radiation), the resistor device, First and second conductive elements each having a first end and a second end, wherein the first ends of the first and second conductive elements are electrically connectable to a power source, the second ends of the first and second conductive elements are coupled to the first and second terminals of the resistor device respectively, the first conductive element is made of a first metal, the second conductive element is made of a second metal different from the first metal, and the first and second conductive elements are configured such that a voltage proportional to the temperature difference is induced between the first conductive element and the second conductive element when there is a temperature difference between their respective first ends and second ends, the first and second conductive elements A system comprising.

[0049] (2) The system according to claim 1, further comprising a control circuit configured to control the temperature of the resistive device to a target temperature by alternately electrically coupling first ends of the first and second conductive elements to a power supply and a voltage detector, the first ends being repeatedly electrically coupled to the voltage detector (wherein "repeatedly electrically coupled" means that the first ends are coupled to and separated from the voltage detector at a time interval that can be a predetermined time interval), the control circuit maintaining the first ends of the first and second conductive elements in an electrically coupled state to the voltage detector until the voltage detected by the voltage detector is less than a target voltage corresponding to the target temperature when the voltage detected by the voltage detector is greater than or equal to the target voltage, and when the voltage falls below the target voltage, the first ends are configured to be electrically separated from the voltage detector and electrically coupled to the power supply, the target temperature of the resistive device being a temperature sufficient to cut a thermally disconnectable connector.

[0050] (3) When the first and second conductive elements are electrically coupled to a power supply for the purpose of raising the temperature of the heater, the control circuit is configured to instantaneously and repeatedly couple the first ends of the first and second conductive elements to a voltage detector to measure the heater temperature, and the repeated instantaneous connection of the first ends of the first and second conductive elements to the voltage detector continues until the target temperature of the heater is achieved, and after the target temperature of the heater is achieved, the first ends of the first and second conductive elements are maintained in a connected state to the voltage detector until the detected temperature of the heater falls below the target temperature, the system according to claim 2.

[0051] (4) The system according to any one of claims 1 to 3, wherein the resistive element is a coiled metal wire.

[0052] (5) The system according to any one of claims 1 to 4, wherein the resistive device is a surface mount device resistor.

[0053] (6) The system according to any one of claims 1 to 5, wherein the first conductive element contains stainless steel and the second conductive element contains nickel.

[0054] (7) The control circuit includes a controller configured to control the states of the first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, and the first and second electrically actuated switches electrically coupling the first ends of the first and second conductive elements to a power source in the first state and electrically coupling the first ends of the first and second conductive elements to a voltage detector in the second state, the system according to claim 2.

[0055] (8) The controller is configured to cause the first and second electrically actuated switches to assume the first state when the voltage detected by the voltage detector is less than a target voltage, the system according to claim 7.

[0056] (9) The controller is configured to cause the first and second electrically actuated switches to maintain the second state when the voltage detected by the voltage detector is greater than or equal to the target voltage, the system according to claim 7.

[0057] (10) The controller is configured to cause the first and second electrically actuated switches to maintain the second state when the voltage detected by the voltage detector is greater than or equal to the target voltage, the system according to claim 8.

[0058] (11) The elongated shaft is at least part of one of the first and second conductive elements, the system according to any one of claims 1 to 10.

[0059] (12) The elongated shaft is the push wire of a plug coil delivery device, and the releasable device is a plug coil, the system according to any one of claims 1 to 11.

[0060] (13) A method of thermally cutting a connector that couples a releasable device to the end of an elongated shaft using a resistive device adjacent to or in thermal contact with the connector, the resistive device including a first terminal, a second terminal, and a resistive element disposed between the first terminal and the second terminal and electrically coupled to the first and second terminals, wherein the first and second terminals have the second ends of the first and second conductive elements electrically coupled thereto respectively, the first ends of the first and second conductive elements being electrically connectable to a power source, the first conductive element being made of a first material, the second conductive element being made of a second material different from the first metal, and the first and second conductive elements being configured to induce a voltage proportional to the temperature difference between the first and second conductive elements when there is a temperature difference between their respective first and second ends, the cutting method comprising: Controlling the temperature of the resistive device to a target temperature by alternately electrically coupling the first ends of the first and second conductive elements to a power source and a voltage detector; Repeatedly coupling the first ends of the first and second conductive elements to the voltage detector; When the voltage detected by the voltage detector is equal to or higher than a target voltage corresponding to the target temperature, maintaining the first ends of the first and second conductive elements in a state of being coupled to the voltage detector until the voltage detected by the voltage detector is lower than the target voltage. After the voltage detected by the voltage detector is lower than the target voltage, the first end is electrically separated from the voltage detector and electrically coupled to the power source; A cutting method comprising the steps of.

[0061] (14) The method according to item 13, wherein the resistive element is a coiled metal wire.

[0062] (15) The system according to item 13, wherein the resistive device is a surface mount device resistor.

[0063] (16) The method according to any one of items 13 to 15, wherein the first conductive element includes stainless steel and the second conductive element includes nickel.

[0064] (17) The control circuit includes first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, the first and second electrically actuated switches electrically coupling a first end of the first and second conductive elements to a power supply in the first state and electrically coupling the first end of the first and second conductive elements to a voltage detector in the second state, the method according to item 13 including the step that the first and second electrically actuated switches assume the first state when the voltage detected by the voltage detector is less than a target voltage.

[0065] (18) The control circuit includes first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, the first and second electrically actuated switches electrically coupling a first end of the first and second conductive elements to a power supply in the first state and electrically coupling the first end of the first and second conductive elements to a voltage detector in the second state, the method according to item 13 including the step that the first and second electrically actuated switches assume the second state when the voltage detected by the voltage detector is greater than or equal to a target voltage.

[0066] (19) The method according to item 17 further includes the step that the first and second electrically actuated switches assume the second state when the voltage detected by the voltage detector is greater than or equal to a target voltage.

[0067] (20) The method according to any one of items 13 to 19, wherein the elongated shaft is a push wire of a plug coil delivery device and the releasable device is a plug coil.

Claims

1. An elongated shaft having a distal end, A releasable device coupled to the distal end of the elongated shaft by a thermally cuttable connector, A resistance device including a first terminal, a second terminal, and a resistance element disposed between the first terminal and the second terminal and electrically coupled to the first terminal and the second terminal, wherein the thermally cuttable connector is positioned adjacent to or in thermal contact with at least a portion of the resistance element, the resistance device; First and second conductive elements each having a first end and a second end, wherein the first ends of the first and second conductive elements are electrically connectable to a power source, and the second ends of the first and second conductive elements are coupled to the first and second terminals of the resistance device, respectively, the first conductive element is made of a first metal, the second conductive element is made of a second metal different from the first metal, and the first and second conductive elements are configured such that when there is a temperature difference between their respective first ends and second ends, a voltage proportional to the temperature difference is induced between the first conductive element and the second conductive element, the first and second conductive elements; A system comprising.

2. Further comprising a control circuit configured to control the temperature of the resistance device to a target temperature by alternately electrically coupling the first ends of the first and second conductive elements to the power source and a voltage detector, the first end is repeatedly electrically coupled to the voltage detector, and the control circuit is configured such that when the voltage detected by the voltage detector is greater than or equal to a target voltage corresponding to the target temperature, the first ends of the first and second conductive elements are maintained in an electrically coupled state to the voltage detector until the voltage detected by the voltage detector falls below the target voltage corresponding to the target temperature, and when the voltage falls below the target voltage corresponding to the target temperature, the first end is electrically separated from the voltage detector and electrically coupled to the power source, and the target temperature of the resistance device is a temperature sufficient to cause the thermally cuttable connector to be cut, the system according to claim 1.

3. When the first and second conductive elements are electrically coupled to the power source for the purpose of raising the temperature of the heater, the control circuit is configured to instantaneously and repeatedly couple the first ends of the first and second conductive elements to the voltage detector to measure the temperature of the heater, and the first ends of the first and second conductive elements are repeatedly and instantaneously connected to the voltage detector until the target temperature of the heater is achieved. After the target temperature of the heater is achieved, the first ends of the first and second conductive elements are maintained connected to the voltage detector until the detected temperature of the heater falls below the target temperature. The system according to claim 2.

4. The system according to claim 1, wherein the resistive element is a coiled metal wire.

5. The system according to claim 1, wherein the resistive device is a surface mount device resistor.

6. The system according to claim 1, wherein the first conductive element includes stainless steel and the second conductive element includes nickel.

7. The control circuit includes a controller configured to control the states of first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, and the first and second electrically actuated switches electrically coupling the first ends of the first and second conductive elements to the power source in the first state and electrically coupling the first ends of the first and second conductive elements to the voltage detector in the second state. The system according to claim 2.

8. The system according to claim 7, wherein the controller is configured to cause the first and second electrically actuated switches to assume a first state when the voltage detected by the voltage detector is less than the target voltage.

9. The system according to claim 7, wherein the controller is configured to cause the first and second electrically actuated switches to maintain a second state when the voltage detected by the voltage detector is greater than or equal to the target voltage.

10. The system according to claim 8, wherein the controller is configured to cause the first and second electrically actuated switches to maintain a second state when the voltage detected by the voltage detector is greater than or equal to the target voltage.

11. The system according to claim 1, wherein the elongated shaft is at least partially one of the first and second conductive elements.

12. The system according to claim 1, wherein the elongated shaft is a push wire of a plug coil delivery device, and the releasable device is a plug coil.

13. A method of thermally cutting a connector that couples a releasable device to an end of an elongated shaft using a resistive device adjacent to or in thermal contact with the connector, the resistive device including a first terminal, a second terminal, and a resistive element disposed between the first terminal and the second terminal and electrically coupled to the first terminal and the second terminal, wherein second ends of first and second conductive elements are electrically coupled to the first and second terminals respectively, first ends of the first and second conductive elements are electrically connectable to a power source, the first conductive element is made of a first metal, the second conductive element is made of a second metal different from the first metal, and the first and second conductive elements are configured such that when there is a temperature difference between the respective first ends and second ends, a voltage proportional to the temperature difference is induced between the first conductive element and the second conductive element, the method comprising: Controlling the temperature of the resistive device to a target temperature by alternately electrically coupling the first ends of the first and second conductive elements to the power source and a voltage detector; Repeatedly coupling the first ends of the first and second conductive elements to the voltage detector; When the voltage detected by the voltage detector becomes equal to or higher than a target voltage corresponding to the target temperature, maintaining the first ends of the first and second conductive elements in a state of being coupled to the voltage detector until the voltage detected by the voltage detector falls below the target voltage, and after the voltage detected by the voltage detector falls below the target voltage, electrically separating the first ends from the voltage detector and electrically coupling them to the power source; The cutting method comprising the above steps.

14. The method according to claim 13, wherein the resistive element is a coiled metal wire.

15. The system according to claim 13, wherein the resistive device is a surface mount device resistor.

16. The method according to claim 13, wherein the first conductive element comprises stainless steel and the second conductive element comprises nickel.

17. The control circuit includes first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, the first and second electrically actuated switches electrically coupling the first ends of the first and second conductive elements to the power supply in the first state and electrically coupling the first ends of the first and second conductive elements to the voltage detector in the second state, the method according to claim 13, comprising the step of the first and second electrically actuated switches assuming the first state when the voltage detected by the voltage detector is less than the target voltage.

18. The control circuit includes first and second electrically actuated switches, each of the first and second electrically actuated switches transitioning between a first state and a second state, the first and second electrically actuated switches electrically coupling the first ends of the first and second conductive elements to the power supply in the first state and electrically coupling the first ends of the first and second conductive elements to the voltage detector in the second state, the method according to claim 13, comprising the step of the first and second electrically actuated switches assuming the second state when the voltage detected by the voltage detector is greater than or equal to the target voltage.

19. The method according to claim 17, further comprising the step of the first and second electrically actuated switches assuming the second state when the voltage detected by the voltage detector is greater than or equal to the target voltage.

20. The method according to claim 13, wherein the elongated shaft is a push wire of a plug coil delivery device and the releasable device is a plug coil.

Images