Classifications

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Definitions

• the invention relates to the medical field and in particular to the treatment of unwanted tissues.
• the invention has example application in treating lung diseases such as chronic obstructive pulmonary disease (COPD), one example of which is emphysema.
• COPD chronic obstructive pulmonary disease
• treatment can beneficially include destroying or affecting a non-desired tissue.
• Such treatments should ideally avoid harming normal tissues adjacent to the non-desired tissue.
• some lung conditions can benefit from treatments that involve destroying or affecting diseased lung tissue. Some of these treatments involve heating the lung tissue.
• Emphysema is a disease that damages the alevioli (air sacs) in a patient's lungs. Affected air sacs can rupture. This alters the distribution of air spaces in the lungs and reduces the surface area of the lungs available to take up oxygen. The lung damage caused by emphysema can trap stale air in the lungs and reduce the flow of fresh, oxygen-rich air into the lungs. In a patient suffering from emphysema, diseased parts of the patient's lungs cannot easily ventilate through the bronchi and trachea, thus preventing the lungs from fully deflating and inflating. Air trapped inside the lungs can prevent the diaphragm from moving up and down naturally.
• Some prior art approaches to heating diseased tissue within the lung involve inserting an ablation device through the trachea and bronchi into the diseased area (for example, see Brannan et al. US 2016/0184013).
• This approach has various shortcomings: only a small part of the lung is accessible, precise mapping of the diseased area is required, and the ablation device must be accurately guided to a precise location. It would be beneficial to provide a system that can automatically heat tissues in diseased areas without having to locate the diseased areas precisely. It would also be beneficial to be able to heat all diseased parts of the lung without excessively heating the healthy parts or the surrounding tissue.
• US4269199 discloses a method for inducing local hyperthermia in treatment of a tumor by short wave diathermy.
• the method involves moving an induction coil over the portion of the body containing the tumor such that the axis of the coil constantly transects different portions of the tumor.
• US5010897 discloses an apparatus for the deep heating of cancers.
• the apparatus employs two single turn coaxial coils which rotate synchronously in planes which are parallel to each other with the central axis of each coil lying in exactly the same line which is perpendicular to the plane of the coil.
• the summated magnetic field of the rotating coils continuously heats a tumor.
• Kasevich US6181970 discloses medical systems and instruments which utilize microwave energy to provide heat treatment and diagnostic imaging of tissue.
• Vertikov et al., US8467858 describes devices and techniques for thermotherapy based on optical imaging.
• This invention has a number of aspects. These aspects include, without limitation:
• An example and non-limiting application of methods and apparatus as described herein is treatment of diseased lung tissues, for example, lung tissues affected by emphysema or other forms of COPD.
• Medical thermal ablation apparatus useful for treatment of emphysema or COPD, the apparatus comprising:
• the plurality of electromagnetic signal applicators adapted to deliver electromagnetic energy to lung tissues for differential heating of diseased and healthier portions of the lung tissues
• the plurality of electromagnetic signal applicators comprising a first set of two or more first electromagnetic signal applicators positionable on one side of a body to be treated and at a second set of at least one second electromagnetic signal applicators positionable on a second side of the body to be treated opposed to the first side such that the body is between the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or any other aspect herein) wherein the first and second electromagnetic signal applicators (or
• a selector circuit connected to receive an output signal from the heating energy signal generator and to selectively apply the output signal between any of a plurality of pairs of the electromagnetic signal applicators, the pairs of the electromagnetic signal applicators each comprising one of the first electromagnetic signal applicators and one of the second electromagnetic signal applicators;
• the medical thermal ablation apparatus according to aspect 1 (or any other aspect herein) (or any other aspect herein) wherein the electromagnetic signal applicators each comprises an electrode.
• the medical thermal ablation apparatus according to aspect 2 (or any other aspect herein) comprising an impedance matching network between the heating energy signal generator and the electrodes.
• the medical thermal ablation apparatus according to aspect 3 (or any other aspect herein) wherein the impedance matching network comprises a plurality of settings, each of the settings provides impedance matching for at least one of the plurality of pairs of electrodes, each of the pairs of electrodes correspond to one of the settings and the controller is connected to control the impedance matching network to switch the impedance matching network to the setting corresponding to the currently selected one of the pairs of electrodes.
• the medical thermal ablation apparatus according to any one of aspects 2 to 4 (or any other aspect herein) wherein the controller is configured to switch from applying the output signal from the currently selected one of the pairs of electrodes to a different one of the pairs of electrodes at a frequency of 100 Hz or less.
• the medical thermal ablation apparatus according to any one of aspects 2 to 5 (or any other aspect herein) wherein the electrode selector circuit comprises a first switch or network of switches switchable to connect a first output of the heat energy signal generator to one of the first electrodes.
• the medical thermal ablation apparatus according to any one of aspects 2 to 6 (or any other aspect herein) wherein the second electrodes comprise a plurality of second electrodes and the electrode selector circuit comprises a second switch or network of switches switchable to connect a second output of the heat energy signal generator to one of the plurality of second electrodes.
• the medical thermal ablation apparatus according to aspect 7 (or any other aspect herein) wherein one of the first and second outputs of the heat energy signal generator is a ground potential.
• the medical thermal ablation apparatus according to any one of aspects 1 to 8 (or any other aspect herein) wherein the heating energy signal generator comprises a radiofrequency (RF) signal generator.
• the medical thermal ablation apparatus according to any one of aspects 1 to 11 (or any other aspect herein) (or any other aspect herein) wherein the controller is connected to receive a temperature signal indicative of a temperature of tissue at one or more locations within the body and is configured to apply feedback control to regulate heating energy delivered into the body from the heat energy signal generator based at least in part on the temperature signal.
• the medical thermal ablation apparatus according to any one of aspects 1 to 12 (or any other aspect herein) (or any other aspect herein) wherein the controller is configured to apply time domain modulation to the output signal of the heat energy signal generator.
• the medical thermal ablation apparatus according to any one of aspects 1 to 13 (or any other aspect herein) (or any other aspect herein) wherein the controller is configured to control the heat energy signal generator to emit the output signal as a pulsed signal and the controller is configured to control widths of the pulses.
• the medical thermal ablation apparatus according to any one of aspects 12 to 14 (or any other aspect herein) further comprising a subcutaneous and/or invasive temperature sensor and the temperature signal comprises an output signal from the subcutaneous and/or invasive temperature sensor.
• the medical thermal ablation apparatus according to any one of aspects 12 to 16 (or any other aspect herein) wherein the controller comprises a thermal model of at least a portion of the body, the thermal model correlating temperature at one of the locations to temperature of a location of interest and the controller is configured to apply the thermal model using the temperature signal as an input and to regulate the heating energy based at least in part on an output of the thermal model.
• the thermal model models comprise some or all of: thermal conductivities of different tissue types in the body, distributions of the different tissue types in the body, geometries of the electromagnetic energy applicators, and blood circulation in the body.
• the medical thermal ablation apparatus according to any one of aspects 12 to 18 (or any other aspect herein) wherein the temperature signal is derived from a non- contact temperature measurement.
• the medical thermal ablation apparatus according to aspect 21 or 22 (or any other aspect herein) wherein the array is a two-dimensional array.
• the medical thermal ablation apparatus according to aspect 1 (or any other aspect herein) wherein the first and second sets of electromagnetic signal applicators respectively comprise first and second two-dimensional arrays of electrodes.
• the medical thermal ablation apparatus according to aspect 24 (or any other aspect herein) wherein the two-dimensional arrays of electrodes are each made up of an equal number of electrodes.
• the medical thermal ablation apparatus according to aspect 24 or 25 (or any other aspect herein) wherein each electrode of the first array of electrodes is positioned directly opposite a corresponding electrode of the second array of electrodes.
• the medical thermal ablation apparatus according to any one of aspects 24 to 26 (or any other aspect herein) wherein the first array of electrodes comprises a first column of electrodes axially spaced apart along the body and a second column of electrodes axially spaced apart along the body.
• the medical thermal ablation apparatus according to any one of aspects 24 to 29 (or any other aspect herein) wherein the first array of electrodes comprises at least four columns of electrodes with the electrodes of each column of electrodes axially spaced apart along the body.
• the medical thermal ablation apparatus according to any one of aspects 12 to 30 (or any other aspect herein) wherein the controller is configured to regulate the heating energy to raise a temperature at one of the one or more locations to a temperature of at least 50 C and to maintain the temperature at 50 C or higher for a selected time period.
• the medical thermal ablation apparatus according to any one of aspects 12 to 31 (or any other aspect herein) wherein the controller is configured to regulate the heating energy to prevent the temperature at one of the one or more locations from exceeding a safe temperature threshold.
• the medical thermal ablation apparatus according to aspect 32 wherein the safe temperature threshold is lower than 50 C.
• the medical thermal ablation apparatus according to aspect 32 or 33 (or any other aspect herein) wherein the controller is configured to discontinue application of the heating energy if the temperature at the one location exceeds the safe temperature threshold.
• the medical thermal ablation apparatus according to aspect 32 or 33 (or any other aspect herein) wherein the controller is configured to modulate application of heating energy from the heating energy signal generator if the temperature at the one location is rising toward the safe temperature threshold at a rate faster than a temperature rise threshold and/or is closer to the safe temperature threshold than a safety margin.
• the medical thermal ablation apparatus according to any one of aspects 2 to 35 (or any other aspect herein) wherein the apparatus comprises shields located between one or more of the electrodes and the body.
• the medical thermal ablation apparatus according to any one of aspects 2 to 39 (or any other aspect herein) wherein the electrodes of the first set of electromagnetic signal applicators are different in area from the electrodes of the second set of electromagnetic signal applicators.
• the medical thermal ablation apparatus according to aspect 41 (or any other aspect herein) wherein the apparatus comprises one or more pumps connected to evacuate the electrically-conductive fluid and the controller is configured to operate the one or more pumps to evacuate the electrically-conductive fluid from one or more of the bladders, when the electrically conductive fluid has been evacuated from the one or more bladders operate a MRI machine to acquire MRI data from the body.
• the medical thermal ablation apparatus according to aspect 42 (or any other aspect herein) wherein the controller is configured to process the MRI data to obtain information characterizing temperatures at one or more locations within the body.
• the medical thermal ablation apparatus according to aspect 1 (or any other aspect herein) wherein the electromagnetic signal applicators each comprises a coil.
• the medical thermal ablation apparatus according to any one of aspects 1 to 44 (or any other aspect herein) wherein the electromagnetic signal applicators are mounted to move relative to the body.
• electromagnetic signal applicators is stationary and the apparatus comprises an actuator controlled by the controller and operable to move the body relative to the at least one of the first and second electromagnetic signal applicators.
• the medical thermal ablation apparatus according to any one of aspects 1 to 48 (or any other aspect herein) comprising bias means for biasing one or more of the electromagnetic signal applicators toward the body.
• the medical thermal ablation apparatus comprising a source of a pressurized cool fluid in fluid communication with the inflatable chamber.
• Medical thermal ablation apparatus useful in the treatment of emphysema or COPD comprising:
• one or more electromagnetic energy signal applicators connected to receive an output signal from the heating energy signal generator and operative to couple electromagnetic energy from the signal generator into tissues of a body, the one or more electromagnetic energy signal applicators comprising one or more signal applicators selected from the group consisting of: electrodes; coils and antennas; and
• a controller connected to receive a connected to receive a temperature signal indicative of a temperature of the tissue at one or more locations within the body wherein the controller is configured to apply feedback control to regulate heating energy delivered into the body from the heat energy signal generator based at least in part on the temperature signal.
• the medical thermal ablation apparatus according to aspect 53 (or any other aspect herein) wherein the controller is configured to apply time domain modulation to the heat energy signal generator.
• the medical thermal ablation apparatus according to any one of aspects 53 to 54 (or any other aspect herein) wherein the controller is configured to control the heat energy signal generator to emit the output signal as a pulsed signal and the controller is configured to control widths of pulses in the pulsed signal.
• the medical thermal ablation apparatus according to any one of aspects 53 to 55 (or any other aspect herein) further comprising a subcutaneous and/or invasive temperature sensor wherein the temperature signal comprises an output signal from the subcutaneous and/or invasive temperature sensor.
• the medical thermal ablation apparatus according to aspect 56 (or any other aspect herein) wherein the subcutaneous and/or invasive temperature sensor comprises a thermistor.
• the medical thermal ablation apparatus according to any one of aspects 53 to 58 (or any other aspect herein) wherein the controller comprises a thermal model of at least a portion of the body, the thermal model correlating temperature at one of the locations to temperature of a location of interest and the controller is configured to apply the thermal model using the temperature signal as an input and to regulate the heating energy based at least in part on an output of the thermal model.
• the thermal model comprises some or all of: thermal conductivities of different tissue types in the body, distributions of the different tissue types in the body, geometries of the electromagnetic energy applicators, and blood circulation in the body.
• the medical thermal ablation apparatus according to any one of aspects 53 to 55 (or any other aspect herein) wherein the temperature signal is derived from a non- contact temperature measurement.
• MRI magnetic resonance imaging
• the medical thermal ablation apparatus according to aspect 63 (or any other aspect herein) wherein the signal applicator comprises an antenna and at least one actuator coupled to movably position the antenna (or any other aspect herein) wherein the controller is configured to move the antenna to alter the direction of the electrical fields.
• the medical thermal ablation apparatus according to aspect 63 (or any other aspect herein) wherein the signal applicator comprises a plurality of pairs of electrodes and an electrode selector circuit and the controller is configured to operate the electrode selector circuit to apply an output of the heating energy signal generator across different ones of the pairs of electrodes at different times.
• the medical thermal ablation apparatus according to aspect 63 (or any other aspect herein) wherein the signal applicator comprises at least one pair of electrodes and at least one actuator operable to move the at least one pair of electrodes relative to a subject and the controller is connected to control the at least one actuator.
• the medical thermal ablation apparatus according to aspect 63 (or any other aspect herein) wherein the signal applicator comprises a plurality of pairs of coils and a selector circuit and the controller is configured to operate the selector circuit to apply an output of the heating energy signal generator to the coils of one of the pairs of coils at a time such that different ones of the pairs of coils are carrying the output signal from the heating energy signal generator at different times.
• the medical thermal ablation apparatus according to aspect 63 (or any other aspect herein) wherein the signal applicator comprises at least one pair of coils and at least one actuator operable to move the at least one pair of coils relative to a subject and the controller is connected to control the at least one actuator.
• the electromagnetic signal applicators adapted to deliver electromagnetic energy to lung tissues for differential heating of diseased and healthier portions of the lung tissues
• the pair of electromagnetic signal applicators comprising one electromagnetic signal applicator of a first set of two or more first electromagnetic signal applicators positionable on one side of a body to be treated and another electromagnetic signal applicator of a second set of at least one second electromagnetic signal applicators positionable on a second side of the body to be treated opposed to the first side;
• each different pair of the electromagnetic signal applicators comprising one of the first electromagnetic signal applicators and one of the second electromagnetic signal applicators .
• the method according to aspect 70 wherein the electromagnetic signal applicators each comprises an electrode and the method comprises matching an impedance of the heating energy signal generator to an impedance presented by each pair of the electromagnetic signal applicators.
• threshold temperature is at least 50 °C.
• a method for treating a lung disease such as emphysema or COPD comprising:
• applying the electromagnetic energy comprises matching an impedance of a source of the electromagnetic energy to an impedance presented by the first and second electromagnetic signal applicators.
• changing the field direction of the electromagnetic energy comprises moving the first and/or second electromagnetic signal applicators relative to the patient.
• electromagnetic signal applicators relative to the patient comprises moving the first and/or second electromagnetic signal applicators along a helical path relative to the patient.
• the second electromagnetic signal applicators is one of a second set of two or more electromagnetic signal applicators and changing the field direction of the electromagnetic energy comprises switching to apply the electromagnetic energy between a pair made up of one of the first set of electromagnetic signal applicators and one of the second set of electromagnetic signal applicators other than the second electromagnetic signal applicator.
• the second set of electromagnetic signal applicators comprises an array of electromagnetic signal applicators that includes a first ow of the electromagnetic signal applicators spaced apart along the patient's body adjacent to a first one of the patient's lungs and a second column of the electromagnetic signal applicators spaced apart along the patient's body adjacent to a second one of the patient's lungs.
• the array of electromagnetic signal applicators comprises a plurality of columns of the electromagnetic signal applicators spaced apart along the patient's body adjacent to each one of the patient's lungs, each of the columns comprising a plurality of the electromagnetic signal applicators.
• Figure 1 is a cross section of a patient's chest being exposed to an electromagnetic field.
• Figure 2 is a view of the electrodes on the patient's back.
• Figures 3A, 3B, 3C and 3D are cross sectional views of the patient's chest being exposed to an electromagnetic field, showing an alternative electrode arrangement.
• Figure 4 is a side view of the patient, showing a method of electrode switching.
• Figures 5 A and 5B are cross sectional views of a patient's chest showing the electrodes being supported by an inflatable vest.
• Figure 5A illustrates a deflated vest.
• Figure 5B shows an inflated vest.
• Figure 6 is a cross section of a patient's chest being exposed to an electromagnetic field being generated by coils.
• Figures 7A and 7B are cross sectional views of a patient's chest showing a pair of electrodes being actuated to move in a helical path around a patient's thorax as electromagnetic energy is being delivered.
• Figure 8 is a flow chart showing an exemplary method of treating unwanted tissues in a patient.
• Methods and apparatus according to certain embodiments of the invention may be applied to selectively heat a diseased area of tissue in a patient while minimizing heating of other tissues in the patient. Heating may be achieved by exposing the diseased tissues to an electromagnetic field to cause dielectric or eddy current heating.
• the electromagnetic field may comprise radiofrequency (RF) energy.
• RF energy comprises microwave radiation.
• selected diseased tissues may be heated to temperatures above a threshold temperature.
• diseased tissues may be heated to temperatures in the range of about 55 degrees C to about 65 degrees C.
• the exact temperature to which diseased tissues are heated is often not critical. In many cases, heating to a slightly lower maximum temperature can be compensated for by maintaining the temperature for a longer duration. It is desirable to avoid heating of healthy tissues because overheating healthy tissues can damage the healthy tissues. The maximum temperature to which healthy tissue can be subjected without lasting damage is not known.
• Certain embodiments of the invention are advantageously applied to treat diseased tissues that have reduced blood flow as compared to nearby healthier tissues.
• the diseased area(s) may be heated rapidly while the healthier tissues will be cooled by the blood flow and will therefore experience reduced increase in temperature as compared to the diseased tissues.
• Emphysema is an example of a condition for which diseased area(s) have reduced blood flow. Certain embodiments of the invention can be particularly effective for treating emphysema because of the low mass (density) of the lungs and the high blood flow in healthy tissues within the lungs.
• the diseased tissues are tissues in the lungs of a patient.
• the patient may suffer from emphysema.
• electromagnetic energy may be applied to heat diseased areas to temperatures of about 50 degrees C or more. While this is done the temperatures of surrounding healthier lung tissue may be kept below a threshold temperature.
• the inventors estimate that healthy tissues in the lungs and organs in the vicinity of the lungs should not be subjected to temperatures in excess of about 40 degrees C or about 45 degrees C.
• Figure 1 illustrates apparatus 10 according to an example embodiment of the invention being applied to treat diseased tissues within lungs 12 and 14 of a patient P.
• Lungs 12 and 14 are surrounded by rib cage 16 inside the patient's body 1.
• a plurality of electrodes 22 (Figure 1 shows four electrodes individually identified as 22A, 22B, 22C and 22D.
• apparatus 10 includes additional electrodes 22.
• the additional electrodes 22 may, for example be located on one or both sides of the plane of the cross-section of Figure 1.
• Electrodes 22 are dimensioned and placed to create an electric field 24 covering as much of lungs 12 and 14 as possible while minimizing penetration of electric field 24 into adjacent organs. Fortunately, the human anatomy allows such a placement.
• a saline solution 26 may optionally be introduced by tubes 28 between body 1 and electrodes 22. Such a liquid coupling can greatly improve the consistency of the coupling of the RF energy delivered by way of some or all of electrodes 22 into body 1.
• electrodes 22 comprise baths of electrically- conductive fluid such as, for example, saline solution.
• Saline solution 26 may, for example, comprise about 1 wt% NaCl in water.
• an electrically-conductive gel is provided between electrodes 22 and body 1.
• RF generator 30 supplies RF energy to electrodes 22 via an impedance matching network 32 and electrode selector circuit 34. The RF energy is applied between two or more of electrodes 22 via wires 36.
• the RF generator 30 has a maximum power output in the range of about lkW to about 5 kW. In some example embodiments, the RF energy output by RF generator 30 has a frequency or frequencies in the range of about 1 MHz to about 100MHz or about 10 MHz to about 100MHz.
• RF generator 30 may have an output frequency of 13.56 MHz or 27 MHz.
• Impedance matching network 32 is provided to match the output impedance of RF generator 30 to the impedance of body 1. This facilitates the efficient delivery of energy into body 1. Impedance matching networks are well known in the art.
• impedance matching network 32 may comprise an LC circuit such as a capacitor connected in series between one output terminal of RF generator 30 and electrode selector 38 followed by an inductor connected in parallel with electrode selector 38. The values of the capacitor and inductor may be determined after measuring the resistance and capacitance between pairs of electrodes 22 on body 1.
• impedance matching network 34 may match a pure resistive impedance (e.g. 50 Ohms) of RF generator 30 to a complex impedance of a human or animal body.
• the impedance matching network may be adjustable to provide a best matching of impedance for each of a plurality of electrode pairs.
• the impedance matching network is self-adjusting (i.e. auto- tuning) to maximize delivery of power into the body. Technologies that can be used to auto-tune the matching network for optimal power delivery (based for example on measurements of reflected radiation) are described for example in: US patent Nos.
• Electrodes 22 and body 1 To avoid resistive currents going through body 1 , and for electrical safety, it is desirable to provide capacitive coupling between electrodes 22 and body 1. For example, one can coat electrodes 22 with a very thin layer of an insulating material. For example, a thin layer of KaptonTM tape may be applied between electrodes 22 and body 1.
• Diseased tissues within one or both lungs 12, 14 may be heated by applying the output of RF generator 30 between two of electrodes 22 located on either side of the lung to be treated. Heating may be continued for sufficient time to raise the diseased tissues to temperatures above a threshold temperature for a time sufficient to achieve a desired treatment outcome.
• the direction of electromagnetic field 24 may be changed periodically. This may be achieved by applying the output of RF generator 30 between different pairs of electrodes 22. Different pairs of electrodes 22 may be selected such that the electric field changes direction but always passes through the portion(s) of lungs 12, 14 containing the diseased tissue to be treated. When this is done, the diseased lung tissues will be heated continuously while surrounding tissues will be heated only intermittently.
• electrode selector 38 switches the output of RF generator 30 to be applied between different pairs of electrodes 22. The switching frequency can be low. For example, electrode selector 38 may switch electrodes once every few seconds. In some non-limiting examples, electrode selector 38 switches electrodes to use a different pair of electrodes deliver of heating energy once every 30 to 300 seconds. In some non-limiting examples electrode selector 38 switches electrodes to use a different pair of electrodes at a frequency of 100 Hz or less.
• the different pairs of electrodes 22 are selected such that a direction of alignment of the electric field within tissues of the patient is changed through an angle of at least 15 degrees (at least 10 degrees, at least 20 degrees and at least 25 degrees are also options) at least every few seconds (e.g. at least every 1 to 30 seconds). In some cases the different pairs of electrodes 22 are selected such that the direction of alignment of the electric field does not remain in the same plane for more than a few seconds. This may be facilitated by providing a two dimensional array of electrodes 22 adjacent each of the patient's lungs on at least one side of the patient.
• Pairs of electrodes may be selected such that a volume of tissue (e.g. lung tissue) that includes diseased areas to be treated lies between electrodes of the selected pairs.
• tissue e.g. lung tissue
• the diseased areas within the volume of tissue may be heated consistently while surrounding tissues may be heated only some of the time.
• heating energy is delivered by way of one selected pair of electrodes at a time.
• delivery of heating energy is rotated among three or four or more selected pairs of electrodes.
• any one selected pair of electrodes may be active approximately 1/N of the time where N is the number of selected pairs of electrodes being used to apply heating energy to a particular lung or other volume of tissue.
• an array of electrodes that substantially covers an area of a patient's lung is provided on a patient's chest and back.
• the electrode arrays may be mirror images of one another.
• Each of the electrode arrays may be shaped to conform to a shape of the patient's lung.
• each of the arrays is two dimensional and comprises plural columns each containing plural electrodes and plural rows each containing plural electrodes. .
• such arrays are provided for one of a patient's lungs.
• such arrays are provided for both of a patient's lungs.
• Such arrays may be applied as described herein to deliver heating energy to tissues of either or both of the patient's lungs.
• the electrodes of a pair of electrodes may be energized with opposite polarities.
• one electrode of a pair is grounded and the other electrode is connected to an output of RF signal generator 30.
• one electrode of a pair is connected to one output terminal of an RF signal generator and the other electrode is connected to another output terminal of the RF signal generator 30.
• Healthier tissues of lungs 12, 14 may be protected from being heated to damaging temperatures by the fact that healthy lung tissue has much larger blood circulation than diseased tissue.
• a non-contact heat source such as radio-frequency (RF) energy
• RF radio-frequency
• heating energy may be applied to cause the diseased areas of lung tissue to be heated to temperatures in the range of 50-70 degrees C while healthy lung areas will only heat up a few degrees above normal body temperature.
• patient P may be breathing chilled air during the procedure.
• the diseased parts of lungs 12, 14 will not get a sufficient amount of chilled air to keep them cool. Cooling may also be facilitated by means of an aerosol of liquefied air.
• Methods as described herein may be implemented in ways that provide the advantage that the location(s) of diseased area(s) does not need to be precisely known in advance. Heating energy can be directed at the whole lung, but only the diseased areas will have their temperatures raised significantly.
• Treatment methods as described herein may be applied to achieve various desired outcomes.
• a single treatment in which a diseased tissue is heated to above a threshold temperature may be sufficient to achieve a desired outcome.
• the desired outcome may be a reduction of the volume of diseased tissue.
• a single treatment may achieve sufficient volume reduction via fibrosis, ablation or other processes.
• the treatment may be repeated two or more times over the course of hours, days, weeks or months to achieved a desired reduction of volume of diseased tissues or other desired outcome.
• a treatment method may comprise heating diseased lung tissue (e.g. tissue affected by COPD or emphysema) in a lung, collapsing the lung and then re-inflating the lung.
• diseased lung tissue e.g. tissue affected by COPD or emphysema
• Heating the lung may be performed quickly (e.g. in seconds or minutes).
• Collapsing the lung may be performed by inserting a hypodermic needle into the pleural space and allowing air to leak into the pleural space. Supplying the lung with pure oxygen will speed up the collapse as it oxygen fully absorbed in the blood.
• the lung may be kept in a collapsed state for long enough to allow the diseased area(s) to collapse into a small volume.
• the lung may be re-inflated by evacuating the pleural space. This may be done, for example via the same needle used to collapse the lung. The procedure can be done on one lung at a time. The patient can breathe with the remaining lung. Collapsing and inflating lungs is done routinely in pulmonary medicine and need not be detailed here.
• This treatment may cause the areas affected by emphysema to collapse and stay collapsed so that these areas are prevented from interfering with normal operation of the healthy parts of the lung, this may achieve results similar to those that can be achieved by surgically removing the diseased lung tissues without the risks of surgery.
• Other mechanisms may exist that do not require pneumothorax: the heated diseased area can lose volume through ablation, fibrosis or other mechanisms and allow healthy lung tissue to fill the voids.
• apparatus 10 includes a controller that automatically controls one or more of: the power output of RF generator 30, the electrodes between which the output of RF generator 30 is applied, a duty cycle of RF generator 30 and a duration of a period during which RF generator 30 applies heating energy to a body 1 based at least in part on real time measurements of temperature(s) at one or more locations in tissues in a patient.
• Temperature sensing may be performed using one or more sensors 36 placed in the patient's body and/or any suitable non-contact temperature sensing technology.
• temperature of tissues within a patient is sensed using small temperature sensors such as thermistors,
• thermistors For example, a prototype embodiment used miniature glass encased thermistors such as DigikeyTM part number 495-5820-ND to measure temperatures of lung tissues.
• Other example ways to measure temperatures of tissues include:
• hypodermic temperature sensors (these may for example comprise an electronic temperature sensor carried in a very fine gage needle (e.g. a needle about 0.6mm in diameter);
• MRI magnetic resonance imaging
• a controller may implement any of various control algorithms.
• a controller of system 10 may implement a PID control loop.
• a controller may implement simple algorithms such as shutting off or reducing the power output of RF generator 30 when a desired temperature has been reached (e.g. a temperature in the range of about 55- 65 degrees C).
• the controller both modulates the power output of RF generator 30 as the temperature of a tissue is raised toward a desired temperature and shuts of delivery of power by RF generator 30 when the desired temperature has been reached.
• Feedback control can prevent the target temperature from being exceeded.
• Embodiments that apply open-loop temperature control may optionally calculate a current temperature within a tissue of interest based on a mathematical model of the heat absorbed in the tissue and the cooling rate of the tissue.
• An output of the model may be applied to control power output of RF generator 30 and/or to stop RF generator 30 from further raising temperature of tissues after the model predicts that a threshold temperature has been reached.
• one or more temperature sensors are applied to sense temperatures of non-targeted tissues.
• non-targeted organs identified as being likely to heat up the most, or as being the organs most sensitive to heat may be identified and the temperatures within these organs may be monitored during treatment.
• a simple temperature sensor installed in a hypodermic needle provides accurate temperature measurements when the needle is inserted into the organ.
• a controller for apparatus 10 may be configured to discontinue treatment if a temperature of a non-targeted tissue exceeds a safe temperature threshold and/or to modulate application of heating energy from RF generator 30 if the temperature of the non-targeted tissue is rising toward or close to the safe temperature threshold.
• Non-target temperature sensors which sense temperature of non-target tissues may be used on their own or combined with temperature sensors that measure temperature of targeted tissues.
• the same temperature sensor e.g. an MRI-based temperature sensor or another non-contact temperature sensor
• Some embodiments modify the system described in US8444635 to include a temperature sensor, a controller connected to receive a temperature signal from the temperature sensor and configured to control delivery of radiation to heat tissues in a patient by a closed loop control algorithm.
• a temperature sensor in target tissues. For example, inserting a temperature sensor into certain areas of lung tissue could risk puncturing the lung.
• a model of the patient's anatomy may be used to estimate how temperature at a specific point in a targeted tissue and/or at a specific point in a non-targeted tissue relates to temperature at an alternative location in the patient.
• the alternative location may be selected to be a location at which a temperature sensor may be placed with lower risk and/or reduced adverse consequences.
• the other location may comprise one or more of muscle surrounding the lungs, exhaled air temperature, blood temperature at a certain location or the like.
• a thermal model of the patient's anatomy may be generated from pre-operative images.
• Known thermal conductivities of different tissue types may be combined with known distributions of those tissue types in the patient, known geometries of electrodes, coils or other structures to be used to deliver heating energy to the tissues and a circulation model to estimate how temperatures at the alternative location(s) correlate to temperatures at the locations of interest. Temperatures measured at the alternative location(s) can then be used as proxies for temperatures at the locations of interest using the correlations determined using the model.
• the patient's orientation is taken into consideration.
• Lower parts of the lung typically contain more blood due to the effect of gravity than parts of the lung at higher elevations. This is called 'differential perfusion'.
• the parts of the lung that contain the most blood can vary with patient orientation.
• the amount of blood at a location to be treated can affect the rate at which the temperature of tissue at that location increases when electromagnetic energy is delivered to the tissue.
• a patient is moved into different postures (e.g. by rotating and/or tilting the patient and or rolling the patient over) as treatment is delivered.
• Apparatus may provide a couch, chair, bed or other patient support that moves by tilting rotating or the like in coordination with the delivery of treatments.
• motions of the patient support are controlled by a controller that also controls application of heating energy to the patient.
• Apparatus provides instructions (e.g. on a display) to change the posture of the patient at selected points during a treatment.
• Apparatus estimates an effect of differential perfusion on properties of tissues in different parts of the lung (or other part of the anatomy). Such estimates may be based for example on information regarding the patient's anatomy (e.g. from pre-operative images).
• a profile for delivering energy to target tissues may take into account differential perfusion by increasing or decreasing the delivered energy depending on whether the target tissues are in a part of the lung at which the target tissues are expected to experience more rapid temperature rise as a result of differential perfusion (e.g. energy may be decreased where the target tissue is at a higher elevation and so the target tissue is depleted of blood) or the target tissues are expected to experience slower temperature rise as a result of differential perfusion (e.g.
• Some embodiments of the apparatus provide a user interface that includes a control that a user may use to indicate a posture of the patient during a treatment. Compensation for differential perfusion may be based at least in part on the indicated posture.
• Electric field 24 uniformity can be affected by various factors including:
• tissues near high voltage will tend to be heated to higher temperatures heat more quickly because the rate of heating relates to density of field lines).
• Some embodiments manipulate one or more of these factors to achieve a desired electric field distribution in the patient. For example:
• electrodes may be constructed by choice of material and/or coating to have a spatially-varying resistivity.
• shields and/or waveguides may be interposed between the electrodes and the body of the patient.
• the electrodes and/or shields and/or waveguides if present may be moved as treatments are delivered.
• an arrangement of electrodes 22 is designed or customized using knowledge of a patient's anatomy and the geometry of the target tissues. For example, MRI and/or computed tomography CT images may be processed to identify regions of different consistency in the patient (e.g. fat tissue / muscle / bone). Working from known average electrical properties of these materials one can design a treatment plan that specifies one or more of:
• the treatment plan may help to target the correct target tissue(s), achieve sufficiently uniform heating, and avoid excessive heating of critical tissue (heart, for example).
• an electrode pattern that comprises arrays of electrodes dimensioned to overlie a patient's lungs on two sides (e.g. chest and back) of a patient's body is generated by analysis of the patient's anatomy and a set of electrodes customized for the patient is fabricated by printing, cutting or other computer-controlled fabrication process using the electrode pattern.
• Figure 2 shows an example arrangement of electrodes 22 on one side of a patient P (e.g. the patient's back) a similar arrangement of electrodes may be provided on an opposing side of the patient (e.g. the patient's chest).
• a separate set of electrodes is provided overlying each of the patient's lungs.
• electrodes 22AA through 22AC are provided over the patient's left lung and electrodes 22BA through 23BC are provided over the patient's right lung.
• electromagnetic energy may be delivered to target lung tissues of the patient P by connecting the output of an RF generator 30 between a pair of electrodes 22 which includes one electrode on the patient's chest and another electrode on the patient's back.
• the pair of electrodes 22 may be directly opposed to one another in some cases and offset from one another in others.
• the electrode arrangement of Figure 2 may be varied in different ways including, for example:
• each of the illustrated electrodes 22 may be replaced by a row of two or three electrodes.
• An exemplary embodiment is shown in Figures 3A to 3D where each of the electrodes 22A, 22B, 22C, and 22D has been replaced by two electrodes.
• An electrode selection circuit 34 as shown for example in Figure 1 may apply heating energy (e.g. an output from an RF signal generator) to different ones of the electrode pairs at different times (electrode switching).
• heating energy e.g. an output from an RF signal generator
• Figure 4 illustrates an example of electrode switching.
• Figure 4 is a side view of patient P in which electrodes 22AA through 22CC are shown. Electrodes 22CA through 22CC are on an opposite side of patient P from electrodes 22AA to 22AC.
• Figure 4 shows that electrodes 22AA to 22CC provide 9 pairs of electrodes 22 wherein the electrodes of each pair include one electrode on one side of patient P and another electrode on an opposing side of patient P such that patient P is sandwiched between the electrodes of the pair.
• the direction of an electric field 24 produced in patient P depends on which pair of electrodes 22 is being used to deliver heating energy. For example consider the three pairs of electrodes involving electrode 22CC.
• the electromagnetic field can be directed as shown by field lines 24, 25 and 26 by respectively pairing electrode 22CC with electrodes 22AA, 22AB and 22AC.
• FIG 4 shows an example situation in which electrode selection circuit 34 comprises electronically controlled switches or commutators 46 and 48.
• the impedance matching network may be constructed to provide a balanced output (balanced relative to ground potential) where a balanced configuration is desired. In the illustrated embodiment this is achieved by providing transformer 50.
• Switches 46 and 48 may comprise, for example, electro-mechanical relays, electromechanical commutators, solid state switches such as RF FET transistors or RF relays or the like.
• different pairs of electrodes 22 may have electrode-to- electrode spacings that are significantly different.
• Some embodiments include mechanisms to compensate for different energy densities in body tissues that may result when heating energy is switched among different electrode pairs. Such compensation may, for example, take one or more of the following forms:
• a controller may automatically set power output of RF generator 30 to different values depending on which pair of electrodes is being driven.
• Some electrodes may be split into plural sections. Different ones of the sections or different combinations of the sections may be used depending on which other electrode the electrode is paired with.
• Pulse width modulation or other time domain compensation may be applied
• a larger number of electrodes 22 may be provided such that more different pairs of electrodes 22 that produce similar energy densities when driven are available for selection.
• An impedance matching network may be tuned or switched to match the
• Electrodes 22 for use in applying heating energy to a patient may have any of a wide variety of forms including stick-on electrodes, electrodes mounted on a belt or the like, electrodes 22 supported by clothing such as a vest or the like.
• An exemplary vest 58 is shown in Figure 5.
• Vest 58 may be inflatable.
• Figure 5A shows vest 58 prior to inflation.
• Figure 5B shows vest 58 that is inflated.
• some or all electrodes 22 comprise bladders containing an electrically-conductive liquid.
• Such electrodes can be advantageous where apparatus as described herein incorporates or is used in conjunction with a MRI system.
• the bladders may be filled with the electrically-conductive fluid.
• the electrically-conductive fluid may be withdrawn from the bladders.
• the electrodes are provided in a way that simplifies applying the electrodes to the bodies of patients such that the electrodes are in close contact with the patients' bodies.
• Electrodes 22 have one or more of the following features:
• the electrodes are stretchable in length and/or width (for example, the electrodes may be made from an electrically-conductive stretchable fabric or a woven or non- woven conductive mesh or a sheet of a stretchable conductive plastic);
• the electrodes are attached to or are attachable to a vest, belt or other clothing
• the electrodes are designed to be made smaller, for example by cutting or tearing off to a size suitable for a particular patient;
• the electrodes are made up of plural smaller electrodes, optionally connections between the smaller electrodes can be made or broken to adjust the sizes of the electrodes to suit individual patients.
• Electrodes 22 may be held in place on a patient P, for example, by one or more of:
• an adhesive which may comprise a self-adhesive and/or a separately-applied
• a formed member such as a bendable support or inflatable chamber (which may be part of an inflatable article of clothing such as a vest) or the like may be provided to hold the electrode against the concave part of the patient's anatomy.
• the support may include passages in which a cool fluid is contained and/or circulating.
• the cool fluid may help to keep the patient cool.
• the support is inflatable the passages containing the cool fluid may be the same as or different from chambers that can be pressurized to inflate the support.
• valves are provided such that circulation of the cool fluid may be inhibited in parts of the support that are in close proximity to a target tissue.
• some embodiments provide coils instead of or in addition to electrodes.
• the coils may be supported against a patient in the same or similar ways as described above for electrodes. This is best illustrated in Figure 6.
• electromagnetic energy can be coupled into a body to heat tissues by:
• Closed-loop temperature control as described herein and/or switching the direction of electromagnetic field lines to reduce heating of non-targeted tissues may be provided in embodiments which apply any of these heating methods.
• the electrodes or coils that apply the RF energy to the body should be placed on opposing sides of the body. Placing electrodes or coils just on one side of the body will create uneven heating, with most heat generated near the electrodes or coils.
• electrodes can be replaced by RF coils, as shown in Figure 6.
• the polarity of coils 52 and 54 is selected to create magnetic field lines 56 going through the lungs 12, 14.
• Multiple coils can be used in a coil switching arrangement similar to the electrode switching arrangements disclosed elsewhere herein.
• the magnetic field can be further directed by using ferrite blocks.
• Electrodes or coils may be provided that are movable relative to a patient P.
• One or more pairs of electrodes may be carried on an actuator operative to move the pairs of electrodes relative to a patient.
• the pairs of electrodes may each include first and second electrodes that are respectively movable over first and second faces of the patient (e.g. chest and back of the patient).
• one pair of electrodes 22 may be actuated to move in a helical path around a patient's thorax as electromagnetic energy is delivered by way of the electrodes 22, as shown in Figures 7 A and 7B.
• one or more pairs of electrodes may be fixed in at least one dimension and the patient may be moved in the dimension relative to the fixed electrodes.
• Apparatus includes or is used in conjunction with a Faraday cage or shielded room to reduce electromagnetic interference with other equipment.
• shielding is provided by a wire mesh cage made up of wires spaced apart by a few centimeters or less.
• the cage may be integrated into walls or other structures of a room.
• thermocouples work well as direct temperature sensors while the thermocouples tested did not perform well. It is believed that the electric field interfered with the low level (under one mV), signals from thermocouples but not with the higher level (volts) signal from the thermistors.
• a suitable thermistor is model H1744 made by the US Sensor company (http://www.ussensor.com/). This thermistor has an outside diameter of 0.43mm.
• Heating time was about 100 seconds.
• the healthy lung reached about 41 degrees C, while the areas with emphysema reached about 55 degrees C. All rats survived the treatment.
• Subsequent autopsy verified scar tissue in the areas of induced emphysema.
• Electrodes e.g. which may be used to apply electric fields for dielectric heating
• coils e.g. which may be used to apply magnetic fields for eddy current heating
• antennas e.g. which may be used to apply microwaves to heat tissues.
• controllers or control systems may be implemented using specifically designed hardware, configurable hardware, programmable data processors configured by the provision of software (which may optionally comprise "firmware") capable of executing on the data processors, special purpose computers or data processors that are specifically programmed, configured, or constructed to perform one or more steps in a method as explained in detail herein and/or combinations of two or more of these.
• specifically designed hardware are: logic circuits, application-specific integrated circuits ("ASICs"), large scale integrated circuits (“LSIs”), very large scale integrated circuits (“VLSIs”), and the like.
• ASICs application-specific integrated circuits
• LSIs large scale integrated circuits
• VLSIs very large scale integrated circuits
• configurable hardware are: one or more
• programmable logic devices such as programmable array logic (“PALs”), programmable logic arrays (“PLAs”), and field programmable gate arrays (“FPGAs”)).
• PALs programmable array logic
• PLAs programmable logic arrays
• FPGAs field programmable gate arrays
• programmable data processors are: microprocessors, digital signal processors ("DSPs"), embedded processors, graphics processors, math co-processors, general purpose computers, server computers, cloud computers, mainframe computers, computer workstations, and the like.
• DSPs digital signal processors
• embedded processors embedded processors
• graphics processors graphics processors
• math co-processors general purpose computers
• server computers cloud computers
• mainframe computers mainframe computers
• computer workstations and the like.
• one or more data processors in a control circuit for a device may implement methods as described herein by executing software instructions in a program memory accessible to the processors.
• processes or blocks are presented in a given order, alternative examples may perform routines having steps, or employ systems having blocks, in a different order, and some processes or blocks may be deleted, moved, added, subdivided, combined, and/or modified to provide alternative or subcombinations.
• Each of these processes or blocks may be implemented in a variety of different ways.
• processes or blocks are at times shown as being performed in series, these processes or blocks may instead be performed in parallel, or may be performed at different times.
• Software and other modules may reside on servers, workstations, personal computers, tablet computers, embedded controllers, process controllers and other devices suitable for the purposes described herein.
• the invention may also be provided in the form of a program product.
• the program product may comprise any non-transitory medium which carries a set of computer-readable instructions which, when executed by a data processor, cause the data processor to execute a method of the invention.
• Program products according to the invention may be in any of a wide variety of forms.
• the program product may comprise, for example, non-transitory media such as magnetic data storage media including floppy diskettes, hard disk drives, optical data storage media including CD ROMs, DVDs, electronic data storage media including ROMs, flash RAM, EPROMs, hardwired or preprogrammed chips (e.g., EEPROM semiconductor chips), nanotechnology memory, or the like.
• the computer-readable signals on the program product may optionally be compressed or encrypted.
• the invention may be implemented in software.
• "software” includes any instructions executed on a processor, and may include (but is not limited to) firmware, resident software, microcode, and the like. Both processing hardware and software may be centralized or distributed (or a combination thereof), in whole or in part, as known to those skilled in the art. For example, software and other modules may be accessible via local memory, via a network, via a browser or other application in a distributed computing context, or via other means suitable for the purposes described above.
• a component e.g. an electrode, oscillator, switch, controller, temperature sensor, software module, processor, assembly, device, circuit, etc.
• reference to that component should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.

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