Automatic signal-optimizing transducer assembly for blood flow measurement

• US 20060241459A1
• Filed: 04/18/2005
• Published: 10/26/2006
• Est. Priority Date: 02/08/2005
• Status: Active Grant

• Current Assignee: Alan Chi-Chung Tai
• Original Assignee: Alan Chi-Chung Tai
• Inventors: Tai, Alan Chi-Chung
• Granted Patent: US 7,857,763 B2
• Time in Patent Office: Days
• US Class Current: 600/454
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0808 for diagnosis of the brain
• CPC Class Codes: A61B 8/4209 by using holders, e.g. positioning frames
• CPC Class Codes: A61B 8/4236 characterised by adhesive patches
• CPC Class Codes: A61B 8/4281 characterised by sound-transmitting media or devices for coupling the transducer to the tissue
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 7/52026 Extracting wanted echo signals Doppler systems G01S15/50; Doppler short range imaging systems G01S15/8979
• CPC Class Codes: G01S 7/52031 Extracting wanted echo signals
• CPC Class Codes: G01S 7/5205 Means for monitoring or calibrating
• CPC Class Codes: G01S 7/52079 Constructional features constructional features of transducers B06B; mounting transducers G10K11/00; constructional features of ultrasonic medical diagnostic devices A61B8/44

Abstract

The invention uses a transducer and ultrasound system to form and direct ultrasound beams through the blood stream that will detect the Doppler shift in frequency between the beams and the return echo off the blood. The transducer can be secured onto the surface of the patient'"'"'s skin with a transducer housing holder. A 1-D transducer, subject to an optimized angle with respect to the blood vessel, will generate and direct ultrasound beams electronically through a blood vessel below the skin and analyze the received echo, searching for the maximum signal amplitude of the Doppler frequency shift from the blood. Furthermore, the device continuously controls the direction of the ultrasound beams to achieve maximum return signal amplitude. Then, the condition and trend of the blood flow is recorded and displayed continuously over the desired diagnostic interval the device is in use.

Claims

1. An auto-signal-optimizing transducer assembly for transmitting ultrasound to, and receiving ultrasound echo signals returned from, a particular blood vessel disposed in a patient'"'"'s body region in which said blood vessel is oriented at an vessel elevation angle relative to the skin surface, said auto-signal-optimizing transducer assembly comprising:

a. a ultrasound transducer component having a front face that transmits ultrasound along a scanning plane directed away from said face and receives ultrasound echo signals returned along said scanning plane;

b. signal connection means for coupling said transducer to an ultrasound generator and processor unit that excites said transducer to transmit said ultrasound and processes said returned ultrasound echo signals received by said transducer component;

c. securing means for detachably and repeatably holding said transducer component on said skin surface and oriented in azimuth adjacent to said body region and to hold said transducer component so said scanning plane is disposed at a fixed transducer elevation angle relative to the skin surface, and is oriented in azimuth on said skin surface to optimize initial returned echo signals from said blood vessel disposed at a vessel elevation angle relative to said skin surface.

2. a medical diagnostic, measurement and monitoring system incorporating the auto- signal-optimizing transducer as set forth in claim 1, wherein said ultrasound generator and processor unit is adapted to excite said transducer to transmit said ultrasound as a beam sweeping over a range of deflection angle along said scanning plane and to process said returned ultrasound echo signals received by said transducer component.

3. The medical diagnostic, measurement and monitoring system as set forth in claim 2, in which said ultrasound echo signal process is adapted to search for, identify and track an optimum signal at an optimum deflection angle, within said deflection range according to a signal optimizing algorithm, whereby said system continuously measures and monitors an optimum ultrasound signal from said blood vessel at an optimum azimuth deflection angle independent of the movement of said blood vessel relative to said adjacent skin surface.

4. The apparatus as set forth in claim 1, in which said fixed transducer elevation angle is fixed at an angle β

relative to said skin surface portion according to the relation β

=90°

θ

+γ

, where γ

is the elevation angle of said blood vessel relative to said skin surface portion and θ

is the angle between the direction of the ultrasound beam and the direction of blood flow, wherein β

can be optimized by a relative Merit method based on the geometry of the transducer assembly, γ and

θ

.

5. The apparatus as set forth in claim 1, in which said securing means comprises:

a. a housing body fixedly encapsulating, protecting and holding said transducer component, said housing body comprising;

i. a top with spaced apart, parallel front and back edges extending between two spaced apart, parallel side walls

ii. longitudinal ribs extending along opposite parallel sides;

iii. a perpendicular bottom face between the two opposite sides presenting an opening for the ultrasound and received ultrasound signals to pass between said transducer face and said skin surface when said housing body is secured to said body portion;

b. a housing body holder comprising;

i. a lateral base member;

ii. a rigid open rectangular channel with a back wall between two parallel side walls extending upright from said lateral base member, the holder side walls spaced apart to receive said housing body with said parallel side walls fitted closely within, the inside of the two holder side walls having opposing grooves formed to slidingly receive and retain said longitudinal ribs of said housing when said housing is fitted against said back wall of said channel;

iii. the lateral base member forming an opening co-extensive with said fitted housing opening;

iv. opposing, thin lateral wings having respective upper and lower surfaces, said wings extending away from said holder opening to distal free ends, said wings shaped to fit closely proximal on said skin surface portion when attached adjacent to said body region, and having sufficient strength to reliably maintain said holder and said housing body in a fixed position and orientation when attached to said skin surface portion.

c. Housing holder attachment means for attaching said lower surface of said lateral wings to said skin surface portion, comprising;

i. a layer of adhesive material on said lower surface suitable for removably attaching said wings to said skin surface portion;

ii. a strong, thin, flexible and magnetically active retainer tape comprising;

1. an upper and lower surface, in which said upper surface is formed to proximally contact and magnetically hold said holder wings when said holder wings are made of complementary magnetically active material,

2. wherein said lower surface comprises an adhesive layer suitable for removably attaching said tape to said skin surface portion;

3. a retainer window formed in said retainer tape to be coextensive with said housing body opening when said transducer component is secured to said skin surface portion by said housing body, said housing body holder and said retainer tape.

6. An auto-signal-optimizing transducer assembly as set forth in claim 1, in which the transducer comprises:

a. an acoustic means for focusing said transmitted and received ultrasound energy.

7. An auto-signal-optimizing transducer assembly as set forth in claim 6, in which the focusing effect is achieved by curving the piezo-electric material into desired region of interest.

8. An auto-signal-optimizing transducer assembly as set forth in claim 6, in which said acoustic lens is made of RTV.

9. An auto-signal-optimizing transducer assembly as set forth in claim 1, comprising:

a. a volume of acoustic gel filling between the front face of the transducer body and the skin covering said adjacent body region when said assembly in attached to said skin surface portion.

10. An auto-signal-optimizing transducer assembly as set forth in claim 8 having conductivity electrodes mounted inside said housing and electrically contacting said acoustic gel and electrically connected to remote conductivity measuring equipment for the purpose of monitoring acoustic gel conductivity so that ultrasound scanning can be terminated if the gel conductivity is lower than a predetermined value.

12. The apparatus set forth in claim 10 wherein:

a. said array is adapted to cooperate with said generating and processing unit such that;

i. said array generates an ultrasound beam that cyclically sweeps at a scanning rate over a maximum deflection angle range in a scanning plane oriented at a fixed elevation angle relative to said skin surface portion.

14. The apparatus as set forth in claim 12, wherein said generating and processing unit computes a blood flow parameter using one or more of said maximum ultrasound Doppler signal amplitudes.

15. The apparatus as set forth in claim 12, wherein said generating and processing unit computes a average value for a blood flow parameter using a plurality of said maximum ultrasound Doppler signal amplitudes.

16. The apparatus as set forth in claim 12, wherein said generating and processing unit computes a trend line for a blood flow parameter using a plurality of said maximum ultrasound Doppler signal amplitudes.

17. The apparatus as set forth in claim 1 in which there is a 2^nd particular blood vessel disposed in a 2^nd body region having a 2^nd blood vessel oriented at a 2^nd vessel elevation angle relative to a 2^nd skin surface adjacent to said 2^nd body region, further comprising;

a second transducer assembly for transmitting additional ultrasound to, and receiving additional ultrasound echo signals returned from, said 2^nd particular 2^nd blood vessel comprising;

a. a 2^nd ultrasound transducer component having a 2^nd front face that transmits said additional ultrasound along a 2^nd scanning plane and receives said additional ultrasound echo signals returned along said 2^nd scanning plane;

b. 2^nd signal connection means for coupling said 2^nd transducer to said ultrasound generator and processor unit that excites said 2^nd transducer to transmit said additional ultrasound and processes said additional returned ultrasound echo signals received by said 2^nd transducer component;

c. 2^nd securing means for detachably and repeatably holding said 2^nd transducer component adjacent to said 2^nd body region and oriented with said 2^nd scanning plane disposed at a 2^nd transducer elevation angle relative to said 2^nd skin surface, in which said 2^nd transducer elevation angle is fixed to optimize said additional returned echo signals from said 2^nd blood vessel.

18. The apparatus as set forth in claim 16, wherein:

said ultrasound generator and processor unit computes at least one difference signal between said processed returned ultrasound echo signals and said processed additional returned ultrasound echo signals and provides a notice to be apprehended when said at least one difference signal exceeds at least one predetermined limit value.

19. The apparatus as set forth in claim 17, wherein said transducer is configured to be mounted on one side of a patient'"'"'s neck adjacent to a first carotid artery, and said 2^nd transducer is configured to be mounted on the other side of said patient'"'"'s neck adjacent to the other carotid artery.

20. the apparatus as set forth in claim 18, in which said notice comprises:

an aural alarm to be heard by attending personnel;

a visual alarm to be seen by attending personnel;

a signal for transmission to equipment for notifying monitoring personnel at a remote location;

a signal coupled to automatic intervention equipment configured to provide automatic interventional treatment to reduce said difference signal below said predetermined limit value.

21. The apparatus as set forth in claim 1, in which said array is divided into a CW transmitting portion and a CW receiving portion, wherein said ultrasound generator and processor unit continuously excites said CW transmitting portion transducer to continuously transmit CW ultrasound and processes returned CW ultrasound echo signals received by said CW receiving portion.

22. The apparatus as set forth in claim 20, in which said CW transmitting portion is one half of said array and said CW receiving portion is the other half of said array.

23. An auto-signal-optimizing medical ultrasound measurement and monitoring system comprising:

a. said auto-signal-optimizing transducer assembly as set forth in claim 3,

b. wherein said ultrasound generator and processor unit is a diagnostic medical ultrasound apparatus previously restricted to ultrasound communication with a manually and/or mechanically manipulated ultrasound transducer connected to said apparatus,

c. wherein said combination enables said diagnostic medical ultrasound apparatus to receive an initial optimum ultrasound Doppler return signal from a blood vessel in said body region and provide an initial optimum blood vessel related metric value or an initial optimum displayed image by locating, orienting in azimuth and securing said auto-signal-optimizing transducer by said securing means on a skin surface portion adjacent to said blood vessel in said body region.

24. The auto-signal-optimizing medical ultrasound measurement and monitoring system as set forth in claim 22, wherein said diagnostic medical ultrasound instrument is further adapted to process said returned ultrasound echo signals to search for, identify and track an optimum Doppler signal at an optimum deflection angle, within said deflection range according to a signal optimizing algorithm,

whereby said system provides the capability for said diagnostic medical ultrasound instrument to provide continuous, unattended monitoring of said blood vessel related metric or display of said image by said mounting, locating and orienting.

25. The auto-signal-optimizing medical ultrasound measurement and monitoring system as set forth in claim 23, wherein said signal optimizing algorithm selects said optimum deflection angle for a maximum

11. An ultrasound transducer assembly comprising:

a. an ultrasound transducer unit;

i. said unit presenting an outward facing ultrasound scanning array on one side;

b. a body portion attachment means comprising;

i. means for detachably securing said attachment means proximal to a skin surface portion of a body region;

ii. attachment means for detachably and repeatedly securing said transducer unit at a fixed location and fixed orientation with said scanning array disposed adjacent to and facing said skin surface portion;

c. signal connection means for connecting said array to a distal signal generating and signal processing unit for communicating ultrasound excitation signals from said processing unit to said array for transmitting ultrasound into said body region through said skin surface portion and for communicating resulting ultrasound echo signals received by said array from said body portion back to said processing unit.

13. The apparatus set forth in claim 11, wherein:

a. said generating and processing unit is adapted to process said echo signals during one or more cycles of said sweep to determine a maximum ultrasound Doppler signal amplitude for each one of said one or more cycles.