Patent Application
20060184070
1. Field of the Invention
The invention relates to ultrasonic therapy, and in particular, to therapy that utilizes an external ultrasonic device configured to deliver therapeutic ultrasonic energy to a patient.
2. Description of the Related Art
Ultrasonic energy may be applied to selected regions within a body to provide a therapeutic effect. In some applications, the ultrasound is generated from an extracorporeal ultrasonic transducer. Examples of such applications include ultrasonic ablation of tissue as shown in U.S. Pat. No. 4,858,613, “Localization and Therapy System for treatment of spatially oriented focal disease”, issued Aug. 22, 1989, to Fry et al.; fracture of kidney stones, as shown in U.S. Pat. No. 4,539,989, “Injury Free Coupling of Therapeutic Shock Waves”, issued Sep. 10, 1985 to Forssmann et al; heat therapy, as shown in, e.g., U.S. Pat. No. 4,586,512, “Device for Localized Heating of Biological Tissue, issued May 6, 1986 to Do-huu; and destruction of thrombi, as shown, e.g., U.S. Pat. No. 5,509,896 “Enhancement of Sonothrombolysis with External Ultrasound, issued Apr. 23, 1996 to Carter et al. The mechanisms of action for these applications require acoustic intensity levels sufficient to cause significant heating or mechanical disruption or destruction of tissue preferably only within a localized region.
The acoustic intensities used for treatment in the localized region of the body range from 0.5 to 100′s of watts per cm2 at the internal treatment site, at frequencies in the 100 kHz-2 MHz range. Prolonged exposure to intense acoustic fields causes tissue destruction through heating or mechanical action. Thus, it may be important that the acoustic field be controlled so that only the target tissue receives prolonged exposure. Ultrasonic energy may have to pass through intervening layers of energy-absorbing tissue, like the skull, in order to reach the area targeted for treatment. This often causes heating of those intervening layers. For example, bone absorbs ultrasound at least thirty times more readily than brain tissue. Thus, to avoid undue skull heating, acoustic intensities at the skull are typically kept relatively low.
In some embodiments, a coupling pad can be used with a transducer element. Ultrasound produced by the transducer element can be propagated through the coupling pad to a patient. In one arrangement, the pad is a pouch containing a pliant substance. The pad may be configured to fit between a patient's skin and a transducer element so that output from the transducer element passes through the pad to a treatment site of the patient. In some variations, the treatment site is tissue in the patient's head.
In some embodiments, a pad is used with a therapeutic ultrasonic treatment device configured to apply ultrasonic energy to a patient's head. The pad comprises a pouch defining a chamber. An ultrasonic coupling media is disposed within the chamber of the pouch. The pad is configured to fit between the patient's skin and a transducer element of the treatment device.
The pad can be somewhat pliant. In some embodiments, the pad is adapted to conform to the topology of the patient's skin. The coupling media disposed within the chamber of the pouch can comprise a gel. The pad is configured to provide a gap between the transducer element and the patient's skin. In some embodiments, the pad is a disposable pad suitable for at least one ultrasound treatment. In other embodiments, the pad is a multi-use pad.
In yet other embodiments, a system for outputting an ultrasound field to a person's head is provided. The system comprises a transducer element configured to apply an ultrasound field to a treatment site in a person's head. A pad includes a covering containing an ultrasonic coupling agent. The pad is sized and configured to separate the transducer element and the skin of the patient's head. In some variations, the coupling agent comprises an ultrasound gel.
The system can further comprise a second transducer element and a second pad. The second pad includes a covering that contains a coupling agent. The second pad is sized and configured to separate the second transducer element and the skin of the patient's head.
In some embodiments, a headset is configured to hold the transducer elements about the person's head such that the pads are compressed between corresponding transducer elements. The pads can be coupled to the headset. In other embodiments, the pads and headset are separatable.
In some embodiments, a method of delivering ultrasound to a patient is provided. The method comprises positioning an ultrasound transducer element relative to a treatment site of a patient. A pliant pad is positioned between the transducer element and the patient. A clot removing agent is delivered to the treatment site. Ultrasound is delivered from the transducer element through the pad and to the treatment site. In some variations, a plurality of ultrasound transducer elements is positioned relative to the treatment site of the patient. Pliant pads are positioned between the transducer elements and the patient. In some variations, pliant pads are compressed between the transducer elements and the patient's skin. In some variations, the pads comprise a bag containing gel.
In one particular embodiment described below, an external device can deliver ultrasound, which enhances the effect of a drug configured to treat an occlusion of a blood vessel within the brain. Such an embodiment is particularly useful for treating victims of ischemic stroke. The external ultrasonic device is preferably configured to produce an acoustic field about the treatment site. For stroke treatment, the acoustic field delivered to the skull can be shaped by geometric focusing, using either physical or electronic lenses to reduce or avoid undue skull heating.
Another embodiment of a external ultrasonic device utilizes the observation that many body structures (e.g., the skull) act as resonators. For example,
The ultrasound transducer 200 emits wave fronts 250 that transit the skull 225. Due to low acoustic loss in the tissue 235 in the cranial vault, the waves travel to the other side of the skull, where they are reflected as wave 255 due to the differing acoustic impedance of the bone and air which forms the skull and its outside boundary. These reflected waves 255 again travel across the cranial vault and again are reflected by the bone and air interfaces, and return across the cranial vault. This process is repeated many times, and builds up to the point where the internal acoustic energy losses in the cranial vault and the reflections at the skull balance the acoustic energy applied by transducer 200. At points 280 where the acoustic waves intersect, pressure nodes and anti-nodes are formed, depending on whether the wave fronts interfere out of phase or in phase, respectively. A common measure of the resonant property of a system is its quality factor, Q, defined as 2π times the ratio of stored energy to the lost energy per cycle. In practice, Q′s from 10 to more than 100 can be obtained with node to anti-node pressure ratios of from 10 to more than 100.
A body part can be treated with acoustic waves below 500 kHz, and preferably below 100 kHz, as a trapped mode resonator. Such a resonator can exhibit a high Q (e.g., a Q of 10 or more) at certain frequencies that cause wave front interference from multiple reflections to add up in phase. Examples of trapped mode resonators within a body include: (a) the cranial vault bounded by air, bone, and neck tissue; (b) arms; (c) legs; and (d) the thorax, all of which are bounded by air and other tissues. In high Q resonators, very high pressures can be achieved in the resonator cavity for a very modest input power U. The differing impedance of skull and air from brain assures that there will be internal reflections, thereby causing the cranial vault to act as a resonator. At frequencies below 500 kHz, little acoustic power need be delivered to the skull to maintain the acoustic field in the brain, because there is little skull or brain heating caused by absorption or other losses. The losses can be reduced or substantially eliminated by using a coupling pad disclosed in detail below.
Acoustic generator 305 is connected to a generator signal source 310. The generator signal source 310 is composed of one or more signal sources 315a . . . x, up to one for each transducer 320a . . . n. Each transducer signal source may have one or more output channels. For example, the signal generator 315a has channel 1 . . . channel x. These channels are connected to transmitter transducer elements or to bi-directional transducer elements or to both, and are also connected to a signal bus, 318a . . . n. Transducer elements k, which are used as hydrophones, are not typically connected to a signal generator, but are connected to a signal bus 318a . . . n. Measurements of impedance and also power for any element may be made by data analysis system 390 which is also connected to these signal busses.
For each output channel of a transducer element's signal source 315a . . . 315n, the drive signal amplitude, modulation characteristics, signal waveform type, and/or frequency may be independently specified. Trigger signal 380, shown as a train of synchronizing pulses, but which may be some other synchronizing signal, is generated within signal source 310 and synchronizes the signal generators 315a . . . n and also the data analysis system 390, via the buss 370. The system also includes an array of hydrophones 302, consisting of k independent hydrophones which are placed in contact with the body part that is to driven as a resonator. These hydrophones are also connected to the data analysis system 390, so that their outputs can be analyzed.
Placement and movement of the nodes and anti-nodes within the resonator are controlled by controlling the amplitude, frequency or phase, or any combination thereof for one or more transducer signal generator output channels. It is specifically noted that amplitude modulation may be used to electronically move one or more active apertures, which also moves the locations of the nodes and anti-nodes within the resonator. For example, referring to
As discussed above, the signal generators 315 provide electrical driving signals for the acoustic transducer drivers 320. These signals may comprise, e.g., sinusoidal waves of defined amplitude, frequency, phase or waveshape, or may comprise pulses of defined amplitude and duration. The signal generators may comprise self-contained units in which the control variables (amplitude, frequency, phase, pulse height, pulse duration, waveshape, etc.) are set by the user by manipulating control knobs that set the control variables. Alternatively, signal generators may be responsive to a control program, stored either internally within the system or externally to it, which defines and controls the desired parameters. Signal generators of both types are known and, indeed, are commonly available as commodity items.
As illustrated in
The arrangement of
As described above, the headset 410 is mounted on the head 400 of a subject and is used to produce one or more acoustic fields inside a human skull, with the cranial vault preferably being the resonant cavity. In the illustrated embodiment, the headset 410 comprises transducer elements 415, 420. A cable 430 leads to the system electronics 435 and is connected to the headset 410. The cable 430 provides communication between the transducers of the headset 410 and the electronics 435.
Transducers 415 and 420 are mounted in the headset 410 such that they press on opposite sides of the head 400 above the ears. The illustrated transducers 415 and 420 are generally diametrically spaced about the patient's head 400. However, the transducers 415 and 420 can be spaced at any suitable location about the patient based on the desired treatment. The headset 410 can have any number of transducers for producing the desired ultrasound field. For example, the headset 410 may comprise three transducers that are spaced evenly or unevenly about the patient's head. In alternative embodiments, a single transducer is mounted to a headset. Thus, any number of transducers can be employed depending on the treatment.
As shown in
With continued reference to
The pad 412 can be permanently or temporarily coupled to the headset 410. For example, the outer face 419 of the pad 412 can be permanently or temporarily coupled to the transducer 415 by fasteners, adhesives, clips, snaps, hook-and-loop fasteners (e.g., Velcro), combinations thereof, or the like. In other embodiments, the pad 412 may be held between the transducer 415 and the patient only by compressive forces created by the headset 410.
The pad 412 can be coupled to the headset 410 for one or more treatment cycles and/or for treating one or more patients. In some embodiments, the pad 412 is configured for a single use by a single patient. In such embodiments, the disposable, one-time use pad 412 may be provided in a sterile free package. The pad 412 can be removed from the sterile package and attached to the transducer, or otherwise secured between the patient and transducer. The transducer can apply ultrasonic energy to the patient via the pad 412. After use, the pad 412 may be detached from the transducer 415 and then discarded. In alternative embodiments, the pad 412 is a multiuse pad that can be used any number of times as desired.
As mentioned above, the pad 412 is preferably plaint so that the pad 412 conforms to the topology of the patient's skin to provide a more efficient acoustical coupling between the transducer and the treatment area. The topology of the patient's skin, in general, will be different from the topology of the ultrasound transducer, such as the transducer surface 427. However, the pad 412 can be compressed between the transducer 415 and the head 400, thereby conforming the pad 412 to the topology of the patient skin and facilitating efficient transmission of ultrasound waves from the transducer 415 through the pad 412 and to the target treatment tissue.
As illustrated in
In the embodiment of
The pad 412 can have any suitable shape.
Optionally, the pad 412 may have indicia for the physician. The indicia can be located on the surface of pad 412 and can indicate desired positioning of the headset 410 relative to the pad 412. The indicia can indicate any information that a physician may deem useful. The indicia can be printed, adhered, and/or embossed on the pad 412.
With reference to
Although not shown, it is contemplated that the outer surface of the pad may also engage a layer of acoustic coupling media (e.g., a coupling agent or gel) to ensure good acoustic coupling between a transducer and the treatment site. Additionally, water, saline, water-based solutions, ultrasound gels or any other suitable coupling media can be used in combination with the pads disclosed herein. For example, a coupling media can be spread on the inner surface 417 of the pad 412 of
The pad 412 can be similar or different than the second pad 414. Thus, the relationship between the second pad 414 and the second transducer 420 may be similar or different than the relationship between the first pad 412 and the first transducer 415.
The headset 410 can be used to aid in the delivery of drugs that are typically used to treat complications due to stroke, Parkinson's disease, or other brain disorders or diseases. For example, the headset 410 can be used to promote drug and/or gene preparations to pass through blood brain barriers. The headset 410 also can be used to treat brain tumors (e.g., primary and/or matastatic tumors). In particular, the ultrasound energy can be used as part of a clot dissolution treatment. In one embodiment, the patient is treated with a clot removing drug. The drug can be administered intravenously or through a drug delivery catheter positioned near or within the brain. The ultrasonic energy is the applied to the brain using an ultrasonic device such as the ultrasonic devices described herein. The ultrasonic energy enhances the therapeutic effect of the clot removing drug. In other embodiments, the ultrasonic energy may be used without the clot removing drug. Examples of clot removing drugs include but are not limited to thrombolytic agents (such as, for example, Heparin, Uronkinase, Streptokinase, Tissue Plaminogen Activator (TPA) and BB-10153, which is manufactured by British Biotech), anti-thrombis drugs, and/or other drugs and enzymes.
All of the patents mentioned herein are incorporated by reference in their entire and made a part of this specification. Although the invention has been disclosed in the context of certain embodiments and examples, it will be understood by those skilled in the art that the invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses and obvious modifications and equivalents thereof. Accordingly, the invention is not intended to be limited by the specific disclosures of preferred embodiments herein.
The method which is described and illustrated herein is not limited to the exact sequence of acts described, nor is it necessarily limited to the practice of all of the acts set forth. Other sequences of events or acts, or less than all of the events, or simultaneous occurrence of the events, may be utilized in practicing the embodiments disclosed herein.
This application claims the priority benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application No. 60/627,469, filed Nov. 12, 2004, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60627469 | Nov 2004 | US |
