Portable device to initiate and monitor treatment of stroke victims in the field

Abstract

Methods and apparatuses are provided for initiating stroke treatment “in the field” and/or during the transport of the patient to a care facility. The capability is provided to adjust automatically to the individual “therapeutic window” for each single patient, which is crucial because of the significant differences in skull morphology between humans of different age, gender and race. Further, the methods and apparatuses are based on the use of non-invasive application of ultrasound, as well as the non-invasive application of ultrasound in combination with an acoustically active agent, such as microbubbles, where stable cavitation of the microbubbles caused by the ultrasound may be relied upon as an underlying mechanism for both the therapeutic application as well as its control.

What is claimed is: 
     
         1 . A method, comprising:
 intravenously administering an acoustically active agent to the patient, wherein the acoustically active agent comprises microbubbles;   applying first and second single use ultrasound transducers to the cranium of a patient, the first and second single use ultrasound transducers applied at disparate locations about the cranium of the patient, wherein the disparate locations include temporal bone regions forward of the ears of the patient, and wherein each of the first and second single use ultrasound transducers are connected to a portable, battery-operated power and control device;   non-invasively applying ultrasound energy to the cranium of a patient via the first and second single use ultrasound transducers, wherein the ultrasound energy excites the acoustically active agent; and   controlling application of the ultrasound energy such that the first and second ultrasound transducers alternately apply the ultrasound energy in pulses to the cranium of the patient, and wherein the controlling application of the ultrasound energy further comprises controlling a power of the ultrasound energy, and   wherein the intravenous administration, the single use ultrasound transducers, and the portable, battery-operated power and control device allow application of the ultrasound energy to occur in the field and prior to arrival of the patient at a care facility, to counteract effects of at least one of: myocardial infarction, deep vein thrombosis, and a cerebrovascular accident due to ischemia.   
     
     
         2 . The method of  claim 1 , further comprising, exciting the acoustically active agent by the ultrasound energy to cause stable cavitation, and detecting a state of inertial cavitation of the acoustically active agent as an indication that the application of the ultrasound energy has exceeded a level commensurate with a therapeutic window. 
     
     
         3 . The method of  claim 2 , wherein the controlling of the application of the ultrasound energy comprises controlling an output power of the ultrasound energy such that stable cavitation is maintained, the stable cavitation triggering a plurality of biophysical effects in the patient. 
     
     
         4 . The method of  claim 3 , wherein the controlling of the output power of the ultrasound energy is performed either automatically or manually. 
     
     
         5 . The method of  claim 4 , further comprising, performing the automatic control of the output power of the ultrasound energy in accordance with at least one of patient-specific characteristics 
     
     
         6 . The method of  claim 5 , wherein the at least one of the patient-specific characteristics comprises age, gender, race, skull bone characteristics, and morphology. 
     
     
         7 . The method of  claim 2 , further comprising, reducing an output power of the ultrasound energy upon the acoustically active agent reaching the state of inertial cavitation. 
     
     
         8 . The method of  claim 1 , wherein the single-use ultrasound transducers comprise disk-shaped piezo-electric elements. 
     
     
         9 . The method of  claim 1 , wherein the single-use ultrasound transducers operate at either a frequency of 200 kHz or in a band of frequencies centered about 200 kHz, and wherein the single-use ultrasound transducers receive acoustic signals in a minimum bandwidth between 100 to 300 kHz. 
     
     
         10 . An apparatus, comprising:
 a first single use ultrasound transducer element including a disk-shaped piezoelectric element;   a second single use ultrasound transducer element including a disk-shaped piezoelectric element; and   a power and control module, the power and control module being portable and battery-operated, the power and control module configured to generate ultrasound energy to be transmitted in an alternating and pulsed fashion by the first and second single use ultrasound transducer elements, noninvasively, to the skull of a patient,   wherein each of the first and second ultrasound transducer elements are designed for single-use application and packaged so as to maintain sterility until used.   
     
     
         11 . The apparatus of  claim 10 , wherein the power and control module further comprises circuitry for the generation of the ultrasound energy at an acoustic output power level and frequency to cause at least one of stable cavitation and inertial cavitation of an acoustically active agent. 
     
     
         12 . The apparatus of  claim 10 , wherein the first and second ultrasound transducer elements operate at either a frequency of 200 kHz or in a band of frequencies centered about 200 kHz. 
     
     
         13 . The apparatus of  claim 12 , wherein each of the disk-shaped piezo-electric elements has a diameter ranging from 2 to 3 cm, a radius ranging from 1 to 1.5 cm, and a thickness of 2 mm. 
     
     
         14 . The apparatus of  claim 12 , wherein two faces of each of the disk-shaped piezo-electric elements are coated with an electricity-conducting material comprising electrodes of each of the first and second ultrasound transducer elements. 
     
     
         15 . The apparatus of  claim 14 , wherein the two faces of each of the disk-shaped piezo-electric elements are coated with at least one of a quarter-wave matching layer on a side facing the patient to aid in energy transmission, a backing layer on a side facing away from the patient, a shielding layer preventing electro-magnetic interference, and an insulating coating preventing inadvertent shock to the patient. 
     
     
         16 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements comprise flat, unfocused disks. 
     
     
         17 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements are driven by the power and control module with a pulse duration between 10 to 1000 μs and a duty cycle between 1 to 50%. 
     
     
         18 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements receive acoustic signals from within the skull of the patient to detect whether a response of the acoustically active agent administered to the patient is stable cavitation or inertial cavitation. 
     
     
         19 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements is operative within a minimum bandwidth in the range of 100 to 300 kHz. 
     
     
         20 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements are configured to capture a subharmonic frequency and a first ultraharmonic frequency. 
     
     
         21 . The apparatus of  claim 20 , wherein the subharmonic frequency is 100 kHz and the ultraharmonic frequency is 300 kHz. 
     
     
         22 . The apparatus of  claim 10 , wherein each of the first and second ultrasound transducer elements are contained in a gel-pad portion, the gel-pad portion being pliant to conform to the shape of the skull of the patient, and aiding in transmission of the ultrasound energy into a target region of the brain of the patient. 
     
     
         23 . The apparatus of  claim 22 , wherein a section of the gel-pad portion contacting the scalp of the patient comprises a peel-away strip configured to expose a layer of adhesive to maintain each of the first and second ultrasound transducer elements in place. 
     
     
         24 . The apparatus of  claim 10 , where each of the first and second ultrasound transducer elements have a minimum half-life of twenty-four hours. 
     
     
         25 . The apparatus of  claim 1 , wherein the power and control module comprises a switching circuit in which a 200 kHz continuous wave signal is switched from one set of conductors to another set of conductors at predefined timepoints to create alternating bursts from the first and second ultrasound transducer elements. 
     
     
         26 . The apparatus of  claim 25 , wherein the predefined timepoints occur at every 100 μs. 
     
     
         27 . The apparatus of  claim 25 , wherein a transmit signal is generated using an oscillation circuit tuned to a nominal 200 kHz continuous sine wave. 
     
     
         28 . The apparatus of  claim 27 , wherein the 200 kHz continuous sine wave is amplified to an appropriate power level, and applied to the switching circuit. 
     
     
         29 . The apparatus of  claim 25 , wherein the switching circuit creates an on time followed by an off time for each of the first and second ultrasound transducer elements, such that when one of the first and second ultrasound transducer elements is in an on state, the other of the first and second ultrasound transducer elements is in an off state. 
     
     
         30 . The apparatus of  claim 29 , wherein the on and off times comprise 100 μs periods. 
     
     
         31 . The apparatus of  claim 29 , wherein the one of the first and second ultrasound transducer elements in the on state transmits the ultrasound energy through the skull of the patient, and the other of the first and second ultrasound transducer elements in the off state receives acoustic signals and is utilized as a passive cavitation detector. 
     
     
         32 . The apparatus of  claim 10  further comprising two cables, each of which operatively connect each of the first and second ultrasound transducer elements to the power and control module. 
     
     
         33 . The apparatus of  claim 10 , wherein the power and control module further comprises a control display for displaying visual information to a user of the apparatus. 
     
     
         34 . The apparatus of  claim 10 , wherein the power and control module is configured to verify that each of the first and second ultrasound transducers are energized. 
     
     
         35 . The apparatus of  claim 10 , wherein the power and control module is configured to allow for automated adjustment of acoustic output power of the ultrasound energy. 
     
     
         36 . The apparatus of  claim 10 , wherein the power and control module is configured to allow for manual adjustment of acoustic output power of the ultrasound energy. 
     
     
         37 . The apparatus of  claim 10 , wherein the power and control module comprises three lights for indicating cavitation control and an upper power limit of the ultrasound energy.