Patent Application
20240423709
The present invention relates to apparatus, systems, and methods for optimizing radiotherapy treatment of cardiac arrhythmias.
Atrial fibrillation is the most common sustained cardiac arrhythmia seen in clinical practice. It causes significant morbidity in both quality of life and risk of thromboembolic disease. Atrial fibrillation increases the risk of stroke four fold. The cornerstone of ablation procedures is pulmonary vein isolation (PVI). In some cases, electrical isolation of the left atrial appendage or posterior wall of the left atrium improve the success of ablation procedures.
Isolating the left atrial appendage (LAA) is associated with a reduction in atrial fibrillation recurrence. However, isolating the left atrial appendage reduces flow velocity, and increases the risk of thromboembolic events even in patients who maintain normal sinus rhythm. Therefore, there is a need to isolate the left atrial appendage without increasing the risk of stroke. Given the reduced blood flow velocity after left atrial appendage electrical isolation, the left atrial appendage is typically closed mechanically. Attempts to electrically isolate the left atrial appendage with catheter ablation have demonstrated a high incidence of electrical reconnection. Therefore, while closure devices are typically recommended after electrical isolation of the left atrial appendage, these closure devices typically prevent attempts to electrically re-isolate the left atrial appendage with catheter ablation.
Atrio-esophageal fistula (AE fistula) is the most feared complication of catheter ablation procedure of atrial fibrillation. Although a rare phenomenon, an AE fistula has a high mortality. The posterior wall of the left atrium is adjacent to the anterior wall of the esophagus. Ablation of the posterior left atrial wall during ablation procedures can also damage the esophageal tissue, which may result in the formation of an AE fistula. During ablation of pulmonary veins or the posterior wall of the left atrium, improved methods to minimize damage to the esophagus is needed.
Radiation can be used to ablate arrhythmia prone cardiac tissue. In order to determine the location of the target, fiducial leads are often placed within the body. However, placement of fiducial leads can be dangerous and uncomfortable to patients. Systems and methods to help identify target structures without placing leads into the heart would be advantageous.
Furthermore, it is difficult to keep the radiation secluded from other healthy tissue that does not need radiation therapy. Improvements are needed to allow radiation only to contact desired areas of tissue that need radiation treatment. Therefore, novel systems and methods are needed to reduce damage to the esophagus during radiation treatment to the left atrium.
In addition, tracking motion of target structures during an ablation procedure may improve ablation success and limit damage to healthy tissue. Furthermore, while x-ray therapy has been most commonly used to performed ablation procedures, charged particles can also be used. Charged particles have the advantage of limiting radiation exposure to surrounding tissue. In addition, charged particles can be influenced by magnetic fields.
Furthermore, certain areas of the heart that need to be ablated for an optimal ablation procedure are in close proximity to the esophagus. However, the esophagus is very sensitive to radiation therapy, limiting radiation to certain areas. Therefore, combining different ablation technologies with radiation therapy can be used to optimize the ablation procedure. For example, radiation therapy can be utilized to perform a large portion of the ablation procedure, particularly when there is no sensitive tissue in the treatment area. However, when there is sensitive tissue near the ablation targets, alternative ablation energies can be delivered to complete the ablation procedure. Some of these ablation energies can be delivered through the esophagus without critical damage to the esophagus.
The present invention is directed to apparatus, systems, and methods to facilitate ablation of myocardial tissue to treat arrhythmias. Specifically, the present application relates to methods and systems to improve radiation therapy to ablate cardiac tissue to treat cardiac arrhythmias. In one embodiment, a trans-esophageal echocardiogram (“TEE”) probe may be placed into an esophagus of a patient to map out targets for radiotherapy. The TEE probe may function as a fiducial marker to track cardiac motion. In addition, real-time monitoring of cardiac structures by ultrasound may be used to focus radiotherapy. By combining prior computed tomography (CT) images with ultrasound images, targets may be tracked. By tracking movement of targets, such as the pulmonary veins, during the cardiac cycle and with effects of respiration, greater radiation may be delivered to targets while minimizing radiation exposure to tissue that is not targeted.
By enabling the elongated device within the esophagus to both image tissue and move the esophagus, improved visualization for improved monitoring is enabled. In addition, moving the esophagus away from the heart will enable radiation therapy to be delivered to critical tissue while minimizing damage to the esophagus. In another embodiment, the TEE probe-like device may be designed to create a magnetic field. The magnetic field may be used to optimize radiotherapy.
For example, the distance between the posterior left atrium and esophagus may be a few millimeters. The magnetic field may be controlled from within the esophagus using the probe to minimize radiotherapy to the esophagus while maximizing radiotherapy to target structures, such as the posterior wall. The esophagus probe may adjust the magnetic field to prevent radiation from reaching the esophagus. By creating the magnetic field from directly within the esophagus, the charged radiation may be controlled to target the pulmonary veins and posterior wall of the left atrium while minimizing radiation damage to the esophagus. This may help prevent atrio-esophageal fistulas from forming.
In other embodiments, the transesophageal device may change the temperature, orientation, or physically move the esophagus relative to the patient's heart to minimize damage to the esophagus. The transesophageal device may move during a radiotherapy treatment to optimize radiotherapy to critical tissue. In another embodiment, negative pressure may be delivered within the esophagus to bring the esophageal tissue to contact the transesophageal device. In some embodiments, the device may include one or more balloons, which may be inflated within the esophagus to maintain a negative pressure around the transesophageal device. By creating a negative pressure within the esophagus, the location, orientation, and/or position of the esophagus may be better monitored and controlled. The esophagus can be moved away from the left atrium in order to deliver external radiation to the left atrium. The esophagus can also be moved towards various aspects of the left atrium in order to deliver electroporation to cardiac tissue.
In another embodiment, the device within the esophagus may be mechanically transformed from an initial delivery shape into an expanded or other shape, such as a wedge or pyramid, to optimize radiation to target tissue while minimizing radiation to non-target tissue. By moving the esophageal device towards the left atrium or increasing the pressure inside of the esophagus higher than the pressure inside the left atrium, the posterior wall of the left atrium may be positioned to maximize radiation exposure to targets while minimizing radiation damage to non-targets. In another embodiment, a compliant or noncompliant balloon may be inflated within the esophagus to prevent the device from moving within the esophagus.
In another embodiment, the transesophageal device may be connected to a motor and/or a robot. The robot or motor may be activated to move the device within the esophagus. Therefore, while delivering radiation therapy to key aspects of the tissue, the device may then be used to move the esophagus to a different location. By moving the esophagus within the thoracic cavity and/or relative to the patient's heart, additional radiation therapy may be delivered to desired regions or aspects of the tissue, e.g., to treat a dysrhythmia, while minimizing the radiation to the esophagus and/or other critical structures. In one embodiment, by having a robot or motor move the device, radiation may be delivered without requiring a person within the treatment room.
In some circumstances, the esophagus cannot be adequately moved to deliver radiation therapy safely. In these and other circumstances, delivering energy through the esophagus may improve an ablation procedure. There are a variety of energy sources that may be delivered through the esophagus to target tissue while minimizing injury to the esophagus. For example, electroporation energy, focused high intensity ultrasound energy, radiation energy, radiofrequency energy, microwave energy, cryothermal energy, and laser energy may be delivered through the esophagus to damage critical tissue to improve the ablation procedure. Electroporation ablation utilizes pulsed, high voltage energy to induce electroporation of cells followed by cell death. This ablation technology is tissue specific and is non-thermal. Prior studies demonstrate that electroporation delivered directly to esophageal tissue results in necrosis of the muscular layers while leaving the endothelial layers unaffected. Thus, this ablation energy may be less likely to cause atrio-esophageal fistulas compared to other ablation energy technologies.
In another embodiment, the transesophageal device may be used to twist the esophagus. For example, the device may include a balloon such that the esophagus may be advanced forward or withdrawn posteriorly or laterally to control positioning of the esophagus. In another embodiment, the device may include spaced-apart balloons, and the balloons may be inflated at distal and proximal locations. Then, negative pressure may be applied to the isolated region of the esophagus between the balloons to cause the esophagus to collapse around the elongated device within the esophagus. In another embodiment, an endotracheal tube including multiple lumens may be introduced into the patient's lung such that one or both of the lungs may be deflated. By collapsing a lung, the esophagus may be moved to a better location. Furthermore, collapsing a lung may enable better imaging by a transducer carried on the device and positioned within the esophagus.
In another embodiment, a magnetic field may be created by the elongated device within the esophagus. By combining a magnetic field from within the esophagus with positioning of the posterior wall of the esophagus, treatments may be designed to minimizing damage to the esophagus. For example, in one embodiment charged radiation may be delivered at an angle to the posterior left atrium that has been positioned and combined with the magnetic field to maximize exposure to one or more target tissue regions while minimizing damage to non-target structures. In some embodiments, radiation may be allowed to be delivered to the blood pool where the risks of radiation are less likely to build over time. Charged radiation includes proton therapy and/or carbon ion therapy.
The device may also cool the esophageal temperature to minimize the effects of radiation on the tissue. The esophageal device may also function as a fiducial marker to help guide radiation therapy.
In another embodiment, the transesophageal device may create a fluctuating magnetic field. For example, the magnetic field may be designed to “bend,” stop, or maximize radiotherapy to certain targets. In other embodiments, the magnetic field is designed to force radiotherapy to stop prior to contacting esophageal tissue. Therefore, while radiation may be directed to the target region(s) from a plurality of angles, adjusting the magnetic field around the body or within the esophagus may further optimize radiation to target region(s) while minimizing radiation to critical structures. Critical structures may include the esophagus, coronary arteries, nerve tissue, and valvular tissue.
In some situations, the transesophageal device may be placed within the esophagus and ultrasound images may be obtained. Next, a CT scan may be performed with the esophageal device in place. Contrast may or may not be used during the CT scan. Then, images from the CT scan may be combined with the images from the ultrasound to better identify tissue within the subject. By combining fiducial markers that can be tracked by both ultrasound monitoring and radiation (including x-rays), treatment may be optimized.
In one embodiment, the radiation ablation procedure may be performed after a device has been placed in the left atrial appendage. The device placed in the left atrial appendage may be or similar to a Watchman device or the Amulet. Therefore, in one embodiment, radiation therapy may be delivered to the heart, and the device in the left atrial appendage may be used as a fiducial marker to guide radiotherapy. This may be used in place of or in addition to the elongated device placed within the esophagus.
In accordance with an exemplary embodiment, an ablation system is provided to treat cardiac dysrhythmias of a heart within a patient's body that includes an elongate member having a proximal end and a distal end sized to be placed within an esophagus within the patient's body, the elongate member comprising an energy-delivering portion on the distal end, wherein the energy-delivering portion delivers energy through the esophagus to ablate tissue in order to treat cardiac dysrhythmias.
In accordance with another embodiment, a method is provided for treating cardiac dysrhythmias in a heart within a patient's body that includes introducing a distal end of an elongated member into an esophagus within the patient's body; and delivering energy from one or more elements on the distal end through the esophagus to ablate tissue in order to treat cardiac dysrhythmias.
In accordance with yet another embodiment, an ablation system is provided to treat cardiac dysrhythmias of a heart within a patient's body that includes a machine configured to deliver radiation energy into the patient's body; a device designed to deliver electroporation energy from within the esophagus; and a controller coupled to the machine and the device such that the two energies are delivered during the same procedure to treat cardiac dysrhythmias.
In accordance with still another embodiment, a method is provided for treating cardiac dysrhythmias in a heart within a patient's body that includes providing a radiation delivery machine adjacent the patient's body; introducing a distal end of an elongated member into an esophagus within the patient's body; and selectively delivering electroporation energy from one or more elements on the distal end from within the esophagus and activating the machine to deliver radiation energy into the patient's body such that both electroporation energy and radiation energy are delivered during the same procedure to treat cardiac dysrhythmias.
Since electroporation is tissue selective, the electroporation pulses can be designed to ablate cardiac tissue while minimizing damage to other tissue. For example, electroporation can be delivered through the esophagus to ablate cardiac tissue and pulmonary vein tissue. However, certain cells, e.g., the phrenic nerve can be damaged during ablation procedures which impair the ability of the patient to breath normally. Electroporation can be delivered to ablate cardiac tissue while minimizing damaging the nerve cells. Therefore, the ablation via electroporation can be performed to ablate cardiac cells (e.g., pulmonary vein isolation) to reduce the risk of atrial fibrillation while avoiding the risk of phrenic palsy. Thus, the systems and methods herein may deliver electroporation through the esophagus to ablate cardiac cells to reduce the risk of atrial fibrillation while minimizing damage nerve cells. In an exemplary method, an ablation procedure may be performed without entering the blood stream to reduce the risk of atrial fibrillation with minimal risk of developing phrenic nerve palsy or damage to other key structures.
Other aspects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.
The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. It will be appreciated that the exemplary apparatus shown in the drawings are not necessarily drawn to scale, with emphasis instead being placed on illustrating the various aspects and features of the illustrated embodiments.
Turning to the drawings,
In accordance with an exemplary embodiment, the system includes a transesophageal device 40, which is shown being positioned within the esophagus 21, and a radiation delivery device (not shown). As described elsewhere herein, the radiation delivery device may be a machine external to the patient that is positioned and oriented towards the patient's body, e.g., operated using a robot or other controller to deliver radiation energy into the patient's body from one or more locations, and/or may be introduced internally, e.g., into the patient's heart 90 as part of the device 40 or as a separate device. Generally, the transesophageal device 40 includes a proximal end (not shown), e.g., including a handle and/or one or more actuators (also not shown), and a distal end sized for introduction into the esophagus 21 that carries one or more sensors, markers, and/or actuatable components, as described elsewhere herein.
For example, the device 40 may include one or more sensors and/or imaging elements having imaging capabilities (e.g., ultrasound to visualize key structures). The distal end of the device 40 may also include one or more markers, e.g., to function as a fiducial for x-rays or other imaging modalities, e.g., to be linked to a three-dimensional mapping/imaging system, such as ultrasound or impedance-based mapping systems. The device 40 may also have a magnet or one or more electromagnetic elements configured to help facilitate mapping, imaging, or guidance of radiation.
In another embodiment, the distal end of the device 40 (within the esophagus 21) may be actuated to change shape, e.g., to move the esophagus 21 away from the left atrium 11, position the left atrium 11 and pulmonary veins 15, and/or otherwise manipulate the esophagus 21, e.g., such that delivery of radiation is tangential to the esophagus 21. Optionally, the distal end of the device 40 may include one or more elements to generate magnetic forces to further optimize delivery of radiation.
In another embodiment, the distal end of the transesophageal device 40 may include a positively or negatively charged electrode, or other elements to create an electric field, which may be used to help guide, control, or direct radiation from the radiation delivery device. In another embodiment, one or more charged electrodes may be provided on the distal end to function as a sink to attract radiation or expel radiation away from the device 40 to protect the esophagus 21.
In another embodiment, the system may include one or more patches that may be placed on the exterior chest of the patient (not shown). The patches and the esophageal device 40 may function as a fiducial for x-ray therapy. In addition or alternatively, the patches and esophageal device 40 may help to create a map using external ultrasound and/or impedance mapping. By combining the fiducials from x-rays with the created map, targets for radiation may be monitored in real-time. Therefore, during the cardiac cycle, patient movement, or patient breathing, real-time monitoring of structures within the patient may facilitate delivery of radiation by the radiation delivery device.
Turning to
In addition, the control processor may be connected to an ultrasound transducer, e.g., carried on the distal end of the transesophageal device, which may be positioned within the esophagus. The controller may receive signals from the transducer to track cardiac tissue during the cardiac cycle, as well as based on patient movement (including breathing), e.g., while the distal end and transducer are moved within the esophagus, e.g., by manipulating the transesophageal device from outside the patient's body.
In addition or alternatively, sometimes it may be desirably to manipulate the distal end of the transesophageal device to move and/or distort the patient's anatomy. For example, the distal end may include one or more expandable members, e.g., balloons, mechanically expandable structures, and the like (not shown), e.g., to increase an outer profile and/or shape of the distal end. In one embodiment, the external aspects of the device may be fixed, while internal components may be actuatable, e.g., using one or more actuators on the proximal end, to move without effecting the patient's anatomy in order to optimize delivery of ablation energy without requiring repeat scans to identify the anatomy.
In addition, as shown in
The control processor may also be coupled to one or more electroporation electrodes, e.g., carried on an external radiation delivery device that may be positioned externally on or around the patient's body. In other embodiments, these electrodes may be configured to delivery other forms of ablation energy used to ablate cardiac tissue, such as focused high intensity ultrasound energy, radiation energy, radiofrequency energy, microwave energy, cryothermal energy, laser energy, and the like.
In addition or alternatively, the control processor may be coupled to a radiation emitter included in an external radiation delivery device. This may be a linear accelerator or other source of radiation. The radiation emitter may be controlled by a robot (not shown) communicating with or contained within the controller to direct radiotherapy to the target structures within the patient's body as determined by the proceduralist(s).
In addition, the control processor is also coupled to one or more physiologie sensors, e.g., placed externally to the patient's body. These sensors may include surface electrodes to monitor the cardiac cycle, respiratory sensors to monitor the breathing cycle, movement sensors, and other physiologic sensors. The control processor may combine physiologie sensor data from these sensor(s) with imaging data to track and model how various structures within the patient's body move during the procedure. By modeling how the structures in the patient's body move during the procedure, energy may be delivered to the target locations while minimizing error.
As shown in
For example, with additional reference to
Furthermore, with reference again to
The control processor may also be coupled to a ventilator. This may be useful because respirations not only move markers or targets that may be provided on the patient's skin or introduced within the heart or elsewhere in the chest cavity, but lung volumes/pressures influence imaging windows and the orientation of structures within the chest. Therefore, the optimal time to deliver radiation therapy may be with the lungs collapsed or fully expanded. In some embodiments, the ventilator is designed to control single lung respiration. In one embodiment, this enables one lung to be collapsed while the other lung is ventilated. By controlling the ventilation, ultrasound imaging, target modeling, and radiation delivery may be optimized by the controller. In some circumstances, the patient is sedated and paralyzed so that the ventilator has complete control over respirations.
Turning to
Image processing at step 54 may include various filtering modalities, various mapping techniques, gamma correction, image enhancement, spectral processing, and/or the like. The image data from the various modalities are combined with the data from the physiologic sensors and undergo image processing 54. Once the image processing 54 has been combined with physiologic sensors data 53, these data undergo image registration 58. Image registration 58 generally involves spatially transforming the various images to align with the target image. In some cases, the target and surrounding tissue are determined a priori utilizing an imaging modality. This imaging is used to create a treatment plan 59.
The treatment plan 59 may include identifying the target volume or location, and the desired dose to the target is prescribed. Sensitive tissue structures (or critical structures) in the vicinity of the target are also delineated and may be assigned a maximum dose that can be deposited to these structures. A computer program, e.g., within the controller of the system or an external device communicating with the controller, then receives the various targets and critical structures, the prescribed doses, the geometric configuration of the radiation delivery system, and the ventilation control 70 in order to compute the position and orientation of beams from the radiation delivery device paired with the ventilation in order to determine and optimize the treatment plan 59. The computer program also determines the radiation dose received by all tissue. This data can be reviewed by the proceduralist(s) to verify the radiation to the target and critical structures. The treatment plan 59, image registration 58, and ventilation control 70 are all then combined to validate motion and treatment 71.
Once the treatment plan has been validated, ablation therapy may be delivered to treat the patient at step 72. In an exemplary embodiment, treating the patient may include delivering radiation therapy and/or other ablation technologies from within the esophagus, e.g., using one or more treatment elements carried by the distal end of the transesophageal device. The treatment may also include using one or more robots, e.g., to control patient ventilation as well as the ablation technologies, e.g., one or both external to the patient and from within the esophagus. The proceduralist(s) must also verify the plan for ventilation control 70 is appropriate for the patient receiving therapy. This may include collapsing a lung, prolonged breath holds, hyperventilation, and the like in order to optimize the ablation procedure. However, certain maneuvers or duration may not be safe for all patients. Therefore, the proceduralist(s) must verify all aspects of the plan before proceeding with the treatment.
Turning to
As shown in the detail of
In addition, the elongated member 65 may also carry one or more electrodes 42 on the distal end 65a. These electrodes 42 may be used to deliver electroporation ablation to the target structures. These electrodes 42 may be configured in various shapes and sizes, including elongated electrodes used in various other electroporation ablation procedures. Furthermore, these or other electrodes may be provided on the distal end 65a to monitor physiological signals to guide the ablation procedure. In some embodiments, the system also includes ventilation control 70 (not shown), similar to other embodiments described herein. In addition, the patient 91 will be closely monitored during the ablation procedure, including pulse oximetry, heart rate, and blood pressure (not shown.
Turning to
Optionally, the elongated member 65 may also include a motorized control portion 66, e.g., on the distal end, capable of moving the esophagus 21 in space and/or rotating the esophagus 21 when actuated. Alternatively, the motorized control portion 66 may move components inside of the elongated member 65 without affecting the esophagus 21.
In some embodiments, the elongated member 65 may include one or more chambers 44 carried on or within the distal end, e.g., defined by balloons or other enclosed structures, e.g., formed from compliant, non-compliant, or substantially non-compliant material. Gas, water, or other fluid may be introduced into and/or removed from the chambers 44 to selectively expand and contract the structures. For example, by inflating one or more of the chambers 44, the distal end of the elongated member 65 may have better contact with the esophagus 21 or have better control in moving the esophagus 21.
Furthermore, in some embodiments, the elongated member 65 may include one or more lumens 45 extending between the proximal and distal ends of the elongated member 65. These lumens 45 may have access to the gastric fluid or provide the ability to inflate or deflate one or more of the chambers 44. In some embodiments, inflation of one chamber 44 will move the esophagus 21 in one direction while inflation of another chamber 44 will move the esophagus in the opposite direction. This movement may be performed with or without the support of the motorized control portion 66. In addition, the esophagus 21 may be selectively manipulated using the various described mechanisms in combination with the ventilation control 70, since respiration and intrathoracic pressure affects the ability to move the esophagus in relation to the heart 90. In addition, in some embodiments, the lumens 45 may contain electromagnetic material, which may create a magnetic field capable of directing charged radiation away from critical tissue and towards target structures.
Optionally, the elongated member 65 may carry one or more electroporation electrodes 42 on the distal end. In addition or alternatively, the elongated member 65 may have a variety of energy-delivering portions, including focused high intensity ultrasound energy, radiation energy, radiofrequency energy, microwave energy, cryothermal energy, and laser energy. Electroporation ablation is tissue specific and can safely ablate nearby tissue without critical damage to the esophagus 21. In some cases, a plurality of electrodes 42 are positioned spaced apart along the distal end of the elongated member 65. However, in other embodiments, at least one electrode 42 may be provided to deliver the electroporation ablation. These electrodes 42 may then be coupled to an electrical pulse generator, e.g., via the controller, to deliver ablation energy. By combining some form of ablation from the esophagus 21 with an external radiotherapy device 61, a complete ablation procedure may be performed without substantial risk of injury to critical tissues, including the esophagus 21.
In some embodiments, the ablation procedure may be performed with the patient intubated, sedated, and/or on a ventilator and be used to treat a variety of cardiac dysrhythmias, including atrial fibrillation. The ablation energy from the elongated member 65 may be used to ablate cardiac tissue, pulmonary vein tissue, and/or ganglionic plexi, as prescribed by the proceduralist(s). Controlling ventilation is paramount for the ablation procedure. Lung volumes influence the relationship between the left atrium 11 and the esophagus 21. The volumes influence the angles of radiation ablation as well as the ability of ultrasound transducer 41 to map and tract tissue. Therefore, in some embodiments, a processor (not shown) controls the ventilator (not shown) in order to optimize the ablation procedure. Furthermore, in some situations the esophagus 21 may need to be moved. Therefore, in some embodiments, a motorized control portion and/or robot 66 may be coupled to the distal end of the elongated member 65, which may manipulate the distal end to position or control the elongated member 65. The robot 66 may be used to move the esophagus 21 relative to the heart 90.
The external radiation source 61 (shown in
Similar to other embodiments herein, the elongated member 65 may also include an ultrasound transducer 41 carried on the distal end. The images from the ultrasound transducer 41 may be used for image registration with other imaging modalities such as MRI or CT images by a controller (not shown), also similar to other embodiments herein. The images from the ultrasound transducer 41 may be used to map and track tissue for ablation, both from within the esophagus 21 or externally.
It will be appreciated that elements or components shown with any embodiment herein are exemplary for the specific embodiment and may be used on or in combination with other embodiments disclosed herein.
While the invention is susceptible to various modifications, and alternative forms, specific examples thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the invention is not to be limited to the particular forms or methods disclosed, but to the contrary, the invention is to cover all modifications, equivalents and alternatives falling within the scope of the appended claims.
The present application is a continuation-in-part of co-pending application Ser. No. 16/362,673, filed Mar. 24, 2019, which claims benefit of co-pending U.S. provisional application Ser. No. 62/647,677, filed Mar. 24, 2018, the entire disclosures of which are expressly incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62647677 | Mar 2018 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16362673 | Mar 2019 | US |
| Child | 18828736 | US |
