Methods and devices to target vascular targets with high intensity focused ultrasound
An ultrasonic applicator unit ( 2 ) is used diagnostically to locate a puncture wound ( 316 ) in an artery and then therapeutically to seal the puncture wound with high intensity focused ultrasound (HIFU). A control unit ( 6 ) coupled to the applicator unit includes a processor ( 74 ) that automates the procedure, controlling various parameters of the diagnostic and therapeutic modes, including the intensity and duration of the ultrasonic energy emitted by the applicator unit. A protective, sterile acoustic shell ( 4 ), which is intended to be used with a single patient and then discarded, is slipped over the applicator unit to protect against direct contact between the applicator unit and the patient and to maintain a sterile field at the site of the puncture. The apparatus and method are particularly applicable to sealing a puncture made when inserting a catheter into an artery or other vessel. Several different procedures are described for locating the puncture wound, including imaging the vessel in which the puncture is disposed and use of a locator rod to determine the disposition of the puncture along the longitudinal axis of the artery.
1. A method for applying heat from a position external to a patient to a region including a blood vessel wall internal to a patient, the method comprising:
a. identifying a flow signal of the blood vessel;
b. determining an initial position and orientation of the blood vessel relative to a therapeutic ultrasound transducer positioned external to the patient;
c. determining the attenuation of an ultrasound beam propagated from the position external to the patient to the blood vessel;
d. determining treatment parameters based on the attenuation of the ultrasound beam;
e. delivering a dose of ultrasound to a nerve surrounding the blood vessel from the position external to the patient;
f. determining a response of the dose delivery to the nerve surrounding the blood vessel based at least in part on a reaction of the patient; and
g. generating converging ultrasound beams which originate at the position external to the patient and propagate to a position adjacent the wall of a blood vessel such that the blood vessel wall is incorporated into the focus of the ultrasound beams.
2. The method of claim 1 wherein step b comprises transmitting at least two signals and determining the relative position of the blood vessel and the ultrasound transducer based upon reflection of the two signals.
3. The method of claim 2 wherein the at least two signals are Doppler signals.
4. The method of claim 1 wherein step g comprises heating the region to a temperature of between about 60 degrees Celsius and about 100 degrees Celsius.
5. The method of claim 4 comprising delivering the converging ultrasound beams in a raster pattern.
6. The method of claim 4 wherein the raster pattern scans a region which is approximately 1.5 cm in length.
7. The method of claim 4 , comprising overscanning the lateral surface of the blood vessel with the ultrasound beams.
8. The method of claim 1 wherein scan geometry of the ultrasound beams is selected based at least in part on consideration of the nerve surrounding the blood vessel.
9. The method of claim 1 wherein the relative position of the blood vessel and the converging ultrasound pulses are displayed to an operator.
10. The method of claim 1 wherein the generating of converging ultrasound beams is controlled automatically without user input.
11. The method of claim 1 further comprising detecting the position of the vessel using a device placed inside or adjacent to the vessel wall.
12. The method of claim 11 wherein the device comprises a sensor.
13. The method of claim 11 wherein the device position is detected using two dimensional or three dimensional ultrasound.
14. The method of claim 11 wherein the device comprises a material that enhances ultrasound reflections.
15. The method of claim 1 further comprising displaying visual indicators of position to an operator.
16. The method of claim 1 comprising determining a spatial location by detection of a sensor.
17. The method of claim 16 wherein the sensor is selected from an acoustic position sensor, an optical position sensor, a magnetic position sensor, and an electromagnetic position sensor.
18. The method of claim 1 wherein step c comprises an A-mode ultrasound pulse to determine the attenuation path of an ultrasound beam.
19. The method of claim 1 wherein the converging ultrasound beams are generated from a phased array of ultrasound transducers.
20. A method for applying heat from a position external to a patient to a region including a blood vessel wall internal to a patient, the method comprising:
a. identifying a flow signal of the blood vessel;
b. determining an initial position and orientation of the blood vessel relative to a therapeutic ultrasound transducer positioned external to the patient;
c. delivering a dose of ultrasound to a nerve surrounding the blood vessel from the position external to the patient;
d. determining a response of the dose delivery to the nerve surrounding the blood vessel based at least in part on a reaction of the patient; and
e. generating converging ultrasound beams which originate at the position external to the patient and propagate to a position adjacent the wall of a blood vessel such that the blood vessel wall is incorporated into the focus of the ultrasound beams, wherein the generating is controlled automatically without user input.