SYSTEMS AND METHODS TO TARGET BLOOD VESSEL ADVENTITIA WITH TRANSCUTANEOUS FOCUSED ULTRASOUND
Systems and methods for maintaining the alignment of a therapeutic ultrasound applicator to a target site are described. Overlapping ultrasound signals are sent to a target tissue site and the echo detected. An algorithm is described for detecting tissue movement relative to the applicator based on comparison of the echo with a previously stored echo.
1 . A method of applying therapeutic energy to a target region comprising a blood vessel, the method comprising:
emitting first ultrasonic pulses from at least three ultrasound transducers to tissue at a target point within the target region, wherein the target point comprises the adventitia of a blood vessel;
detecting first ultrasonic echoes from the blood vessel with the ultrasound transducers;
emitting second ultrasonic pulses from the ultrasound transducers;
detecting second ultrasonic echoes from the blood vessel with the ultrasound transducers;
comparing the first and second ultrasonic echoes to determine time shifts or phase differences between the first and second ultrasonic echoes;
determining the amount of relative tissue movement using the time shifts or phase differences and pre-determined unit vectors of each ultrasound transducer;
adjusting a focus of a therapeutic ultrasound applicator based at least in part on the determined amount of relative tissue movement to keep the target point within the focus of the therapeutic applicator; and
emitting a dose of therapeutic ultrasonic energy from the therapeutic ultrasound applicator such that the target point is exposed to the dose.
2 . The method of claim 1 , wherein determining the amount of relative tissue movement comprises executing a recursive algorithm.
3 . The method of claim 1 , wherein the predetermined unit vectors are determined experimentally.
4 . The method of claim 1 , wherein the therapeutic applicator comprises at least one of the ultrasound transducers.
5 . A method of applying focused ultrasound therapeutic energy, the method comprising:
emitting a first ultrasonic pulse from a first ultrasound transducer through skin tissue to a target point within a target region, wherein the target point comprises the adventitia of a blood vessel, the first ultrasound transducer comprising an array of at least one therapeutic piezoelectric element;
detecting a first ultrasonic echo from the blood vessel at one of the therapeutic piezoelectric elements of the first ultrasound transducer;
emitting a second ultrasonic pulse from the first ultrasound transducer;
detecting a second ultrasonic echo from the blood vessel at one of the therapeutic piezoelectric elements of the first ultrasound transducer;
comparing the first and second echoes to determine time shifts or phase differences between the detected echoes;
determining the position of the target point relative to the focus of the therapy using the time shifts or phase differences;
adjusting a focus of a therapeutic ultrasound applicator based at least in part on the determined position to keep the target point within the focus of the therapeutic applicator; and
emitting a dose of therapeutic ultrasonic energy from the therapeutic ultrasound applicator such that the target point is exposed to the dose.
6 . The method of claim 5 , further comprising detecting the ultrasonic echoes with at least one additional ultrasound transducer.
7 . The method of claim 6 wherein the additional ultrasound transducer does not contribute to therapy.
8 . The method of claim 6 wherein the additional ultrasound transducer is placed on the perimeter of the annular array.
9 . The method of claim 5 , further comprising detecting the amount of relative tissue motion between the first and second echoes.
10 . A method of applying therapeutic energy to a target region comprising a blood vessel, the method comprising:
emitting an ultrasonic pulse from a first ultrasound transducer to tissue at a target point within the target region, wherein the target point comprises the adventitia of a blood vessel;
detecting a first ultrasonic echo from the target point;
comparing the first echo to a previously recorded echo to determine time shifts or phase differences between the detected echoes and the previously recorded echoes;
determining the amount of relative tissue movement using the time shifts or phase differences and pre-determined unit vectors of each ultrasound transducer;
adjusting a focus of a therapeutic ultrasound applicator based at least in part on the determined amount of relative tissue movement to keep the target point within the focus of the therapeutic applicator; and
emitting a dose of therapeutic ultrasonic energy from the therapeutic ultrasound applicator such that the target point is exposed to the dose.
11 . The method of claim 10 , further comprising detecting the ultrasonic echo with at least one additional ultrasound transducer.
12 . The method of claim 10 , wherein determining the amount of relative tissue movement comprises executing a recursive algorithm.
13 . The method of claim 10 , wherein the predetermined unit vectors are determined experimentally.
14 . The method of claim 10 , wherein the therapeutic applicator comprises the first ultrasound transducer.
15 . The method of claim 10 , wherein the first ultrasound transducer comprises a piezoelectric element adapted exclusively to transmit imaging ultrasonic pulses.