Method and apparatus for guidance and application of high intensity focused ultrasound for control of bleeding due to severed limbs
An ultrasonic diagnostic and therapy system is described for stopping the bleeding of severely damaged blood vessels or vessels severed in a limb amputation. A cuff is attached to the stump of the severed limb which contains a diagnostic transducer array and a HIFU transducer. The diagnostic transducer surveys the tissue of the severed limb, searching for a Doppler flow signal. When a Doppler flow signal is detected, the range to and coordinates of the sample volume where the flow was detected are determined, as well as the flow velocity. This information is supplied to a HIFU therapy transducer controller, which controls the HIFU transducer to transmit focused ultrasound to the sample volume of the flow locus, the center of the lumen of a blood vessel. The focused ultrasound heats and coagulates blood in the severed vessel to stem the bleeding. Heat dissipation due to the blood flow is reduced by tracking and continuously heating the same bolus of blood as it flows, or by heating a significant length of the blood vessel instead of a fixed spot in the vessel.
1. A method for ultrasonically reducing the blood of a damaged or severed peripheral blood vessel by heating comprising:
affixing a transducer array to a limb;
identifying a first locus of a blood bolus to be heated, with a transducer array operated at diagnostic power levels;
heating the identified blood bolus with a transducer array operated at therapeutic power levels;
tracking the blood bolus to a second locus; and
heating the identified blood bolus again at the second locus.
2. The method of claim 1 , further comprising continuously heating the identified blood bolus as it flows from the first locus to the second locus.
3. The method of claim 1 , further comprising repetitively heating the identified blood bolus as it flows from the first locus to the second locus.
4. The method of claim 3 , further comprising identifying another locus of the blood bolus between the repetitions of heating.
5. The method of claim 1 , wherein the steps of identifying and heating are performed with the same transducer array.
6. The method of claim 1 , wherein the step of identifying is performed with a diagnostic ultrasound transducer array and the steps of heating are performed with a therapy ultrasound transducer array.
7. The method of claim 1 , wherein the step of affixing comprises attaching a cuff including the transducer array to the limb.
8. The method of claim 7 , wherein the step of affixing comprises inflating the cuff including the transducer array about the limb.
9. The method of claim 1 , further comprising, prior to a heating step, electronically steering the focal point of a HIFU array to the identified blood bolus.