Tissue modification systems and methods and signal generators for use therewith
Tissue treatment systems and methods are disclosed. In an embodiment, a tissue treatment system includes a LV signal generator, a HV signal generator, and a controller. The LV signal generator is used to produce a LV tissue impedance measurement signal, and the HV signal generator is used to produce a HV tissue treatment signal having a voltage that is at least five times greater than a voltage of the LV tissue impedance measurement signal. The controller controls when the HV tissue treatment signal produced using the HV signal generator, and when the LV tissue impedance measurement signal produced using the LV signal generator, are delivered to patient tissue via an active electrode and a return electrode. The LV tissue impedance measurement signal is used to estimate the impedance of the patient tissue, which is used to control the voltage and/or current of the HV tissue treatment signal.
1 . A tissue treatment system that is configured to deliver a predetermined target current to patient tissue during a treatment procedure, wherein the predetermined target current comprises a default target current specified prior to beginning the treatment procedure or is specified by a clinician using a user interface of the tissue treatment system prior to beginning the treatment procedure, the tissue treatment system comprising:
a low voltage (LV) signal generator used to produce a LV tissue impedance measurement signal;
a high voltage (HV) signal generator used to produce a HV tissue treatment signal having a voltage that is at least five times greater than a voltage of the LV tissue impedance measurement signal;
a current sense circuit configured to measure a current that is delivered to the patient tissue via an active electrode while the LV tissue impedance measurement signal, which is produced using the LV signal generator, is delivered to the patient tissue; and
a controller configured to
control when the HV tissue treatment signal produced using the HV signal generator, and when the LV tissue impedance measurement signal produced using the LV signal generator, are delivered to patient tissue via the active electrode and a return electrode;
produce an estimate of an impedance of the patient tissue based on the voltage of the LV tissue impedance measurement signal that is delivered to the patient tissue and based on the current measured by the current sense circuit; and
adjust the voltage of the HV tissue treatment signal produced using the HV signal generator during the treatment procedure, based on the estimate of the impedance of the patient tissue and one or more updates thereto, so that when the HV tissue treatment signal is delivered to the patient tissue during the treatment procedure the patient tissue is treated with a current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure.
2 . The tissue treatment system of claim 1 , wherein in-between each of a plurality of separate instances of the HV signal generator being used to produce the HV tissue treatment signal that is delivered to the patient tissue during the treatment procedure, the controller is configured to:
cause the LV signal generator to be used to produce the LV tissue impedance measurement signal that is delivered to the patient tissue;
produce an updated estimate of the impedance of the patient tissue based on the voltage of the LV tissue impedance measurement signal that is delivered to the patient tissue and based on an updated measure of the current that is delivered to the patient tissue, as measured using the current sense circuit; and
adjust the voltage of the HV tissue treatment signal that is produced using the HV signal generator, in response to the updated estimate of the impedance of the patient tissue differing from an immediately preceding estimate of the impedance of the patient tissue, so that when the HV tissue treatment signal is next delivered to the patient tissue the patient tissue is treated with a further current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure.
3 . The tissue treatment system of claim 1 , wherein:
the LV signal generator includes a LV power supply; and
the HV signal generator includes a HV power supply that is distinct from the LV power supply of the LV signal generator.
4 . The tissue treatment system of claim 3 , wherein:
the LV signal generator includes a LV waveform shaping circuit coupled between the LV power supply and the active and the return electrodes; and
the HV signal generator includes a HV waveform shaping circuit, which is distinct from the LV waveform shaping circuit, and is coupled between the HV power supply and the active and the return electrodes.
5 . The tissue treatment system of claim 3 , wherein:
the LV signal generator and the HV signal generator share a same waveform shaping circuit.
6 . The tissue treatment system of claim 1 , wherein:
the current sense circuit comprises a LV current sense circuit configured to measure the current that is delivered to the patient tissue via the active electrode while the LV tissue impedance measurement signal, which is produced using the LV signal generator, is delivered to the patient tissue; and
further comprising a HV current sense circuit, which is distinct from the LV current sense circuit, and is configured to measure a further current that is delivered to the patient tissue via the active electrode while the HV tissue treatment signal, which is produced using the HV signal generator, is delivered to the patient tissue;
wherein a resolution of measurements produced by the LV current sense circuit is tailored to a range of expected LV current measurements, and a resolution of measurements produced by the HV current sense circuit is tailored to a range of expected HV current measurements that differs from the range of expected LV current measurements.
7 . The tissue treatment system of claim 6 , wherein the controller is further configured to:
produce the estimate of the impedance of the patient tissue based on the voltage of the LV tissue impedance measurement signal that is delivered to the patient tissue and based on the current measured by the LV current sense circuit;
set a voltage of the HV tissue treatment signal, which is produced using the HV signal generator, based on the estimate of the impedance of the patient tissue; and
adjust the voltage of the HV tissue treatment signal, which is produced using the HV signal generator, based on the further current measured by the HV current sense circuit.
8 . A tissue treatment system that is configured to deliver a predetermined target current to patient tissue during a treatment procedure, wherein the predetermined target current comprises a default target current specified prior to beginning the treatment procedure or is specified by a clinician using a user interface of the tissue treatment system prior to beginning the treatment procedure, the tissue treatment system comprising:
a pair of electrodes including an active electrode and a return electrode;
a plurality of capacitors;
a power supply configured to charge the plurality of capacitors;
a waveform shaping circuit coupled between the plurality of capacitors and the pair of electrodes;
a current sense circuit configured to measure a current that is delivered to the patient tissue via the active electrode while a low voltage (LV) tissue impedance measurement signal is delivered to the patient tissue; and
a controller configured to
cause a first subset of the plurality of capacitors to be coupled to the waveform shaping circuit during a first period of time during which the LV tissue impedance measurement signal is to be delivered to patient tissue via the pair of electrodes;
cause a second subset of the plurality of capacitors to be coupled to the waveform shaping circuit during a second period of time during which a high voltage (HV) tissue treatment signal is to be delivered to the patient tissue via the pair of electrodes;
produce an estimate of an impedance of the patient tissue based on a voltage of the LV tissue impedance measurement signal that is delivered to the patient tissue and based on the current measured by the current sense circuit; and
adjust a voltage of the HV tissue treatment signal during the treatment procedure, based on the estimate of the impedance of the patient tissue and one or more updates thereto, so that when the HV tissue treatment signal is delivered to the patient tissue during the treatment procedure the patient tissue is treated with a current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure;
wherein
the voltage of the HV tissue treatment signal is at least five times greater than the voltage of the LV tissue impedance measurement signal;
the first subset of the plurality of capacitors includes at least one of the plurality of capacitors; and
the second subset of the plurality of capacitors includes at least one of the plurality of capacitors and differs from the first subset of the plurality of capacitors.
9 . The tissue treatment system of claim 8 , wherein:
the power supply, the waveform shaping circuit, and the first subset of the plurality of capacitors are components of a LV signal generator configured to produce the LV tissue impedance measurement signal;
the power supply, the waveform shaping circuit, and the second subset of the plurality of capacitors are components of a HV signal generator configured to produce the HV tissue treatment signal; and
the power supply and the waveform shaping circuit are shared by both the LV signal generator and the HV signal generator.
10 . The tissue treatment system of claim 9 , wherein in-between each of a plurality of separate instances of the HV tissue treatment signal being produced and delivered to the patient tissue during the treatment procedure, the controller is configured to:
produce an updated estimate of the impedance of the patient tissue; and
adjust the voltage of the HV tissue treatment signal that is produced, in response to the updated estimate of the impedance of the patient tissue differing from an immediately preceding estimate of the impedance of the patient tissue, so that when the HV tissue treatment signal is next delivered to the patient tissue the patient tissue is treated with a further current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure.
11 . A method for delivering a predetermined target current to patient tissue during a treatment procedure, wherein the predetermined target current comprises a default target current specified prior to beginning the treatment procedure or is specified by a clinician using a user interface prior to beginning the treatment procedure, the method comprising:
(a) producing a low voltage (LV) tissue impedance measurement signal and delivering the LV tissue impedance measurement signal to patient tissue via an active electrode and a return electrode;
(b) measuring a current that is delivered to the patient tissue via the active electrode while the LV tissue impedance measurement signal is delivered to the patient tissue;
(c) producing an estimate of an impedance of the patient tissue based on a voltage of the LV tissue impedance measurement signal that is delivered to the patient tissue and based on the current that is measured; and
(d) producing a high voltage (HV) tissue treatment signal and delivering the HV tissue treatment signal via the active and return electrodes, wherein a voltage of the HV tissue treatment signal is at least five times greater than the voltage of the LV tissue impedance measurement signal, and wherein the producing the HV tissue treatment signal includes adjusting the voltage of the HV tissue treatment signal during the treatment procedure based on the estimate of the impedance of the patient tissue and one or more updates thereto so that when the HV tissue treatment signal is delivered to the patient tissue during the treatment procedure the patient tissue is treated with a current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure.
12 . The method of claim 11 , wherein steps (a), (b), (c) and (d) are performed in that order, and after being performed in that order, are repeated in that order such that when step (c) is repeated an updated estimate of the impedance of the patient tissue is produced, and such that when step (d) is repeated the voltage of the HV tissue treatment signal is controlled based on the updated estimate of the impedance of the patient tissue so that the patient tissue is treated with a further current that is approximately equal to the predetermined target current.
13 . The method of claim 11 , wherein steps (a), (b), (c) and (d) are performed in that order, and after being performed in that order, steps (a), (b) and (c) are repeated in that order to produce an updated estimate of the impedance of the patient tissue, and the method further comprising:
determining, based on the updated estimate of the impedance of the patient tissue, whether treatment of the patient tissue was sufficient or whether additional treatment of the patient tissue should be performed at an additional instance of step (d).
14 . The method of claim 13 , wherein when the additional treatment of the patient tissue is to be performed at the additional instance of step (d), then the producing the HV treatment signal at the additional instance of step (d) includes controlling the voltage of the HV tissue treatment signal based on the updated estimate of the impedance of the patient tissue so that the patient tissue is treated with a further current that is approximately equal to the predetermined target current.
15 . The method of claim 11 , wherein:
the producing the LV tissue impedance measurement signal at step (a) is performed using a LV signal generator; and
the producing the HV tissue treatment signal at step (c) is performed using a HV signal generator that is distinct from the LV signal generator.
16 . The method of claim 11 , further comprising:
using a power supply to charge a plurality of capacitors;
using a waveform shaping circuit, coupled between the plurality of capacitors and the active and return electrodes, to shape the LV tissue impedance measurement signal and the HV tissue treatment signal;
wherein
the producing and the delivering the LV tissue impedance measurement signal at step (a) includes coupling a first subset of the plurality of capacitors to the waveform shaping circuit during a first period of time;
the producing and the delivering the HV tissue treatment signal at step (c) includes coupling a second subset of the plurality of capacitors to the waveform shaping circuit during a second period of time;
the first subset of the plurality of capacitors includes at least one of the plurality of capacitors; and
the second subset of the plurality of capacitors includes at least one of the plurality of capacitors and differs from the first subset of the plurality of capacitors.
17 . A tissue treatment system that is configured to deliver a predetermined target current to patient tissue during a treatment procedure, wherein the predetermined target current comprises a default target current specified prior to beginning the treatment procedure or is specified by a clinician using a user interface of the tissue treatment system prior to beginning the treatment procedure, the tissue treatment system comprising:
one or more voltage signal generators;
a current sense circuit configured to measure a current that is delivered to the patient tissue via an active electrode while one of the one or more voltage signal generators is delivering a voltage signal to the patient tissue; and
a controller configured to
produce an estimate of an impedance of the patient tissue based on the current measured by the current sense circuit; and adjust a voltage of the voltage signal produced during the treatment procedure using one of the one or more voltage signal generators, based on the estimate of the impedance of the patient tissue, so that during the treatment procedure the patient tissue is treated with a current that is approximately equal to the predetermined target current that was specified prior to beginning the treatment procedure.