Bronchial denervation using integrated A-mode signal for optimization of ultrasound treatment
Apparatus and methods for deactivating bronchial nerves extending along a bronchial branch of a mammalian subject to treat asthma and related conditions. An ultrasonic transducer ( 11 ) is inserted into the bronchus as, for example, by advancing the distal end of a catheter ( 10 ) bearing the transducer into the bronchial section to be treated. The ultrasonic transducer emits focused ultrasound so as to heat tissues throughout circular impact volume ( 13 ) as, for example, at least about 1 cm 3 encompassing the bronchus to a temperature sufficient to inactivate nerve conduction but insufficient to cause rapid ablation or necrosis of the tissues. The treatment can be performed without locating or focusing on individual bronchial nerves.
1 . System for conducting pulmonary treatment in a mammalian subject, comprising:
an elongated member having a balloon, cooling fluid within the balloon, and an energy transducer, the transducer adapted for insertion into a bronchial branch of a bronchial tree of the mammalian subject and configured for transmitting energy into surrounding tissue, and
a control electrically connected to the transducer, the control adapted to control the transducer to emit ultrasound energy into an impact volume encompassing the bronchial branch so that the energy is applied at a therapeutic level sufficient to inactivate conduction of bronchial nerves throughout the impact volume;
a pressure sensor configured to monitor fluid flow to determine a diameter of the bronchial branch based on detection of pressure increase of the balloon in relation to fluid volume increase.
2 . The system of claim 1 , wherein the elongated member holds an axis of the transducer generally parallel to an axis of the bronchial branch.
3 . The system of claim 1 , wherein the pressure sensor detection corresponds with the balloon reaching full inflation inside the bronchial branch.
4 . The system of claim 1 , wherein the transducer is positioned within the balloon.
5 . The system of claim 1 , wherein the control is configured to analyze a volume integrated A-mode signal to indicate cartilage ring positioning and further configured to deliver the ultrasound energy at the therapeutic level between cartilage rings.
6 . The system of claim 5 , wherein the control is configured provide the ultrasound treatment volume in a plane between cartilage rings.
7 . The system of claim 4 , wherein the cooling fluid cools the ultrasound transducer, the ultrasound transducer being disposed in alignment with and centered on an axis of the bronchial branch.
8 . The system of claim 1 , wherein the ultrasound transducer is adapted to transmit the ultrasound energy in a 360° cylindrical pattern surrounding an axis of the ultrasound transducer.
9 . The system of claim 1 , wherein power used to transmit the ultrasound energy is configured to be varied depending on a determined diameter of the bronchial branch within which the transducer is positioned.
10 . The system of claim 1 , wherein the transducer is configured to transmit ultrasound energy without determining actual locations of bronchial nerves of the subject.
11 . The system of claim 1 , wherein a diameter of a focal ring of energy is varied by changing a shape of the balloon with pressure.
12 . The system of claim 1 , wherein the control adjusts ultrasound energy levels based on the bronchial diameter calculated by balloon pressure.
13 . The system of claim 1 , wherein the control is adapted to control the transducer to emit ultrasound energy at a level below the therapeutic level to detect air pockets.
14 . The system of claim 13 , wherein trapped air is detected by analysis of an amplitude of a signal transmitted by the transducer at an interface of the balloon and bronchial branch.
15 . The system of claim 13 , wherein trapped air is detected by analysis of time delay between transmitting and receiving echo from a signal transmitted by the transducer.
16 . The system of claim 13 , wherein the control is configured to analyze volume integrated A-mode signals to detect air filled spaces in the impact volume.
17 . The system of claim 13 , wherein the elongated member includes a balloon, wherein the control is configured to transmit ultrasound energy at the level below the therapeutic level to determine if the balloon is coupled to a wall of the bronchial branch.
18 . The system of claim 13 , wherein the control is configured to transmit a low-power ultrasound pulse and analyze ultrasound echoes to measure the diameter of the bronchial branch.
19 . The system of claim 13 , wherein a volume integrated echo represents coupling of the balloon with the bronchial wall.