Apparatus for performing non-invasive thermodilution

Abstract

An apparatus and method are provided for performing non-invasive thermodilution and creating a thermodilution curve using high-intensity focused ultrasound (HIFU) and ultrasonic temperature measurement. The apparatus of the present disclosure includes an ultrasonic transducer system having one or more ultrasonic transducers or transducer arrays, and a processor communicatively coupled to the ultrasonic transducer system. The ultrasonic transducer system is configured to locally increase the temperature of a subject's blood using HIFU and measure the corresponding temperature change of the downstream blood using ultrasonic temperature measurement. The processor is configured to create a thermodilution curve based on receiving a signal regarding a measure of the temperature change from the ultrasonic transducer system.

Description

Technical Field

[0001] The present disclosure generally relates to thermal dilution devices and techniques. More particularly, embodiments herein relate to devices and methods for performing non-invasive thermal dilution and creating thermal dilution curves using high-intensity focused ultrasound (HIFU) and ultrasonic temperature measurement.

Background Art

[0002] Blood flow measurement is important for both physiology and clinical practice. In pathological conditions, peripheral circulation often decreases. Most of the human blood flow is sent from large blood vessels (arteries) to the peripheral region and then back to large blood vessels (veins). From peripheral vessels to large blood vessels, both the flow velocity and the vessel dimensions change by a large factor. Blood flow and cardiac output are important parameters for measuring when a patient is hemodynamically unstable.

[0003] To measure blood flow and cardiac output, the thermal dilution method of injecting a fixed amount of fluid at a fixed temperature into the blood flow is used, and the corresponding downstream temperature change is recorded. Since cold fluid is less harmful to blood and tissue than hot fluid, this cold fluid is often used as an indicator in the thermal dilution method. For example, for measuring cardiac output in human adults, cold saline or isotonic dextrose solution near 0°C is generally used in an amount up to 10 ml. The injected cold indicator is mixed and diluted in the warm blood flow, causing a slight temperature drop in the downstream blood.

[0004] This thermodilution method has several advantages, namely, the indicator is non-toxic so that measurements can be repeated, the dilution curve can be easily recorded by a thermistor placed in the blood vessel, and the recirculation component is small enough so that the integral of the dilution curve can be accurately performed. The basic assumption of the indicator dilution method that the indicator must not leak from the vascular system between the injection site and the detection site is not entirely valid because heat can dissipate across the vessel wall. In large blood vessels, this effect is not a problem because the ratio of surface area to volume per unit length is small. Therefore, the thermodilution method is more suitable for measuring the flow rate of large blood vessels than that of small blood vessels.

[0005] Conventional thermodilution techniques use a specially designed catheter called a Swan-Ganz thermodilution catheter, which is widely used for measuring cardiac output. Conventionally, the catheter is inserted from a peripheral vein through the right ventricle into the pulmonary artery. A bolus of cold saline or dextrose solution (glucose solution) is injected into the right atrium, where mixing occurs in the right atrium and right ventricle, and the resulting temperature decrease is detected by a thermistor placed in the pulmonary artery.

[0006] Techniques different from the thermodilution method using intravascular heating have also been tried. Heat can be transferred to the blood flow using an electric heater. In this study, a heating wire was wound around a standard thermodilution catheter. When a sinusoidal heat signal with an average output of 4 W and a frequency of 0.02 Hz was applied to the right ventricle of a sheep and the temperature change of the blood in the pulmonary artery was detected simultaneously, a cardiac output in the range of 1.8 - 9.5 liters per minute could be measured. A correlation coefficient of 0.977 was obtained between the heating method and the standard rapid injection thermodilution measurement.

[0007] However, the techniques described above are invasive and associated with the development of complications.

[0008] PiCCO (Pulse Indicator Continuous Cardiac Output) is also a thermodilution measurement that requires a complex and invasive placement.

[0009] Thermodilution provides important clinical information, but thermodilution is an invasive method associated with many complications. Thermodilution may also induce right bundle branch block and even complete heart block. Additionally, the use of fluid boluses affects the fluid management of the patient. It is necessary to prevent fluid overload in the patient, which affects the amount of fluid bolus administered to the patient. Therefore, the current thermodilution method cannot be used at high measurement frequency settings. The current gold standard requires fluid boluses that cause fluid overload in the patient. Summary of the Invention Problems to be Solved by the Invention

[0010] By using a non-invasive method for measuring a thermodilution curve (which is the gold standard), the acceptability of the technology is improved. However, the ultrasonic technologies currently available for measuring cardiac output still require a skilled operator and are not continuous. In addition, these thermodilution methods are still regarded as the gold standard and are used by clinicians to interpret and process the information obtained from these methods.

[0011] Therefore, there is a need for a system and method that aim to make the thermodilution method non-invasive without requiring a skilled operator and at the same time address the drawbacks of existing thermodilution technologies.

[0012] The limitations and drawbacks of conventional and traditional techniques will become apparent to those skilled in the art by comparing the system described in the remainder of this application with some aspects of the present disclosure with reference to the drawings.

[0013] "Calibration and Evaluation of Ultrasound Thermography Using Infrared Imaging" by HSIAO YI-SING, Ultrasound in Medicine and Biology, vol 42, no.2, 5 November 2015 discloses a method of using infrared thermography for calibration and verification of ultrasound thermography.

[0014] "Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating" by ANAND A, Ultrasound in Medicine and Biology, New York, US, vol 34, no.9, 1 September discloses a non-invasive method of estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data. US Patent Application Publication No. 2013 / 046178 discloses a method for monitoring temperature by using ultrasound, acquiring echo signals of diagnostic ultrasound irradiated towards a treatment site, generating a candidate temperature image from the echo signals using different temperature determination methods, and merging the generated candidate temperature images.

[0015] US Patent Application Publication No. 2006 / 129053 discloses a catheter in reverse direction in the blood flow for determining blood flow by thermodilution measurement.

Means for Solving the Problems

[0016] The claimed solution based on computer technology performs thermodilution, creates a thermodilution curve, overcomes problems particularly occurring in the field of computer technology, and measures the blood flow and cardiac output (CO) of a subject.

[0017] An apparatus and method for performing thermal dilution are substantially provided as shown in and / or described in connection with at least one of the figures, as fully set forth in the claims.

[0018] These and other features and advantages of the present disclosure will be understood from a consideration of the following detailed description of the present disclosure, taken in conjunction with the accompanying drawings, in which like reference numerals refer to like parts throughout the drawings.

[0019] In the claimed solution of the present disclosure, an apparatus for performing non-invasive thermal dilution includes an ultrasonic transducer system. This ultrasonic transducer system includes one or more ultrasonic transducers or transducer arrays. The ultrasonic transducer system is configured to locally increase the temperature of a subject's blood using high-intensity focused ultrasound (HIFU) and to measure the corresponding temperature change of the downstream blood using ultrasonic temperature measurement. A processor communicatively coupled to the ultrasonic transducer system is configured to create a thermal dilution curve based on receiving a signal regarding a measure of the temperature change from the ultrasonic transducer system.

[0020] According to one embodiment, the ultrasonic transducer system is configured to administer a bolus into the subject's blood stream to locally increase the temperature of the blood using HIFU. The bolus in some embodiments can be, but is not necessarily limited to, cold saline or dextrose solution. The temperature of the administered bolus is different from the temperature of the subject's blood stream.

[0021] In some embodiments, the ultrasonic transducer system measures the subject's blood flow rate. The processor is configured to derive the subject's cardiac output from the thermal dilution curve based on the heat dissipation of the bolus by the blood flow in the subject's heart.

[0022] According to one embodiment, the processor is configured to analyze the thermodilution curve using a frequency profile based on signal processing. Techniques used to analyze the thermodilution curve include, but are not limited to, fast Fourier transform (FFT) signal processing and impulse response functions.

[0023] In some embodiments, the amplitude of the thermodilution profile of the thermodilution curve is increased by placing the HIFU focus and the measurement point of the temperature measurement closer to each other.

[0024] In some other embodiments, to obtain a low cardiac output that changes the frequency profile of the thermodilution curve, the frequency of temperature rise and dissipation (also known as "temperature injection frequency") is selected such that the blood temperature rises immediately after the complete thermal dissipation of the bolus. The processor is configured to detect from the ultrasonic transducer system an increase in the average signal due to a low cardiac output at the same frequency of blood temperature rise and the thermal dissipation of the bolus falling below the baseline. When the processor detects an increase in the average signal, it is configured to shift the frequency of temperature rise and dissipation.

[0025] The main object of the present disclosure is to provide a non-invasive thermodilution method for avoiding risks and serious complications when used in a clinical environment. Since the fluid is not used to create a temperature difference, there is no limit to the number of times the thermodilution technique of the present disclosure operates. When HIFU heating and ultrasonic temperature measurement or thermography are repeatedly used, the resulting thermodilution curve reflects a frequency profile, which can be analyzed using techniques such as, but not limited to, FFT signal processing and impulse response methods. Furthermore, by selecting the temperature injection frequency such that the temperature rise is immediately after the complete thermal dissipation, a low cardiac output (CO) changes the frequency profile.

[0026] Furthermore, by removing the need for a thermistor and replacing the thermistor with ultrasonic thermography, the system is safer, easier to use, and less costly. The thermal dilution profile has a lower amplitude compared to the currently known cold saline bolus method.

[0027] It should be understood that all combinations of the concepts described above and additional concepts discussed in more detail below are part of the subject matter disclosed in the specification, provided that such concepts are not mutually inconsistent. In particular, all combinations of the claimed subject matter at the end of this disclosure are considered part of the subject matter disclosed herein. Any terminology explicitly used herein that also appears in any incorporated disclosure shall be construed to have the meaning that most closely matches the particular concepts disclosed herein.

[0028] These and other aspects of the various embodiments will become apparent from and be elucidated with reference to the embodiments described hereinafter.

Brief Description of the Drawings

[0029] The various advantages of the embodiments will become apparent to those skilled in the art from reading the following specification and appended claims and by referring to the following drawings.

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Best Mode for Carrying Out the Invention

[0030] As will be described in more detail below, in some implementations described herein, the apparatus and method are advantageously used to address some of the challenges in performing non-invasive thermodilution for measuring a subject's blood flow and cardiac output (CO).

[0031] FIG. 1 is a block diagram showing a system implementing the apparatus described herein for performing non-invasive thermodilution, according to an exemplary embodiment of the present disclosure. Referring to FIG. 1, a system 100 is shown that includes a subject 102 and an apparatus 104 that includes an ultrasonic transducer system 106, a processing system 108, a user interface 110, and a thermodilution curve 112 displayed on the user interface 110.

[0032] The ultrasonic transducer system 106 includes one or more ultrasonic transducers or transducer arrays having appropriate logic circuits, circuits, interfaces, and / or code operable to transmit ultrasonic irradiation or vibrations to the subject 102 to locally increase the temperature of the subject's 102 blood using high-intensity focused ultrasound (HIFU). The ultrasonic transducer system 106 is further configured to measure corresponding temperature changes in the downstream blood using ultrasonic temperature measurements.

[0033] The processing system 108 is communicatively coupled to the ultrasonic transducer system 106 and the user interface 110. The user interface 110 may be implemented via one or more form factor devices that can include, but are not limited to, smartphones, tablets, laptops, workstations, and / or the like.

[0034] The ultrasonic processing system 106, the processing system 108, and the user interface 110 can communicate with each other via communication technologies including, but not limited to, Internet-based communication, cloud-based communication, wired communication, wireless communication, the like, and / or combinations thereof.

[0035] The processing system 108 can have appropriate logic circuitry, interfaces, and / or code configured to create a thermal dilution curve 112 to be displayed on the user interface 110 based on receiving a signal regarding the measure of temperature change from the ultrasonic transducer system 106.

[0036] During operation, the ultrasonic transducer system 106 is configured to administer a bolus into the bloodstream of the subject 102 to locally increase the temperature of the blood using HIFU. This bolus can be, but is not limited to, cold saline or a dextrose solution. The temperature of the bolus is different from the temperature of the bloodstream of the subject 102. The ultrasonic transducer system 106 is further configured to measure the corresponding temperature change of the downstream blood using ultrasonic temperature measurement.

[0037] In some embodiments, the ultrasonic transducer system 106 measures the blood flow rate of the subject 102.

[0038] FIG. 2 is a block diagram showing an apparatus for performing non-invasive thermal dilution according to an exemplary embodiment of the present disclosure. Referring to FIG. 2, an apparatus 104 is shown that includes a memory 202, a user interface 204, a processor 206, a communication unit 208, a transducer interface 210, a measurement component 212, a thermal dilution curve creation component 214, and an analysis component 216.

[0039] Memory 202 includes, but is not limited to, one or more memory devices, persistent storage devices, computer-readable storage media, random access memory (RAM), and cache memory. Generally, memory 202 can include any suitable volatile or non-volatile computer-readable storage media. Memory 202 can have appropriate logic circuits and / or interfaces configured to store instructions (e.g., computer-readable program code) for implementing various aspects of the present disclosure.

[0040] Memory 202 is communicatively coupled to user interface 204 and processor 206.

[0041] User interface 204 may be implemented via one or more form factor devices including, but not limited to, smartphones, tablets, laptops, workstations, and / or the like.

[0042] Processor 206 can have appropriate logic circuits, interfaces, and / or code configured to execute instructions stored in memory 202 to implement various functions of device 104 according to various aspects of the present disclosure. Processor 206 may be further configured to communicate with various modules of device 104 via communication unit 208.

[0043] Communication unit 208 can be configured to transmit data between modules, engines, databases, memories, and other components of device 104 for use in performing the functions discussed herein. Communication unit 208 can include one or more communication types and can utilize various communication methods for communication within device 104.

[0044] The transducer interface 210 couples the ultrasonic transducer system 106 to the device 104. The ultrasonic transducer system 106 includes one or more ultrasonic transducers or transducer arrays having appropriate logic circuitry, circuitry, interfaces, and / or code operable to transmit ultrasonic irradiation or vibrations to the subject 102 to locally increase the temperature of the blood of the subject 102 using high-intensity focused ultrasound (HIFU).

[0045] The measurement component 212 can have appropriate logic circuitry, interfaces, and / or code configured to measure corresponding temperature changes in the downstream blood using ultrasonic temperature measurement.

[0046] The thermodilution curve creation component 214 can have appropriate logic circuitry, interfaces, and / or code configured to create a thermodilution curve 112 to be displayed on the user interface 204 based on receiving a signal regarding the scale of the temperature change from the ultrasonic transducer system 106.

[0047] The analysis component 216 can have appropriate logic circuitry, interfaces, and / or code configured to derive the cardiac output (CO) of the subject 102 from the thermodilution curve 112 based on the heat dissipation of the bolus by the blood flow in the heart of the subject 102. The analysis component 216 is configured to analyze the thermodilution curve 112 using a frequency profile based on signal processing, for example, using fast Fourier transform (FFT) signal processing, impulse response functions, and the like.

[0048] In one embodiment, the amplitude of the thermodilution profile of the thermodilution curve 112 increases by placing the HIFU focus and the measurement point of the temperature measurement closer to each other.

[0049] According to various embodiments, to obtain a low cardiac output that varies the frequency profile of the thermal dilution curve, the frequency of temperature rise and dissipation (also known as "temperature injection frequency") is selected such that the temperature of the blood rises immediately after the complete thermal dissipation of the bolus. The processor 206 is configured to detect from the ultrasonic transducer system 106 an increase in the average signal due to a low cardiac output at the same frequency of the blood temperature rise and the thermal dissipation of the bolus falling below the baseline. When detecting an increase in the average signal, the processor 206 is configured to shift the frequency of temperature rise and dissipation.

[0050] According to one embodiment, the ultrasonic transducer system 106 is configured to vary the temperature upstream of the detection modality using focused ultrasound technology by creating "boluses" with different temperatures.

[0051] For example, HIFU creates a local high temperature within the tumor tissue to create tissue damage. The temperature rise is local and dissipates quickly, approaching the ambient conditions 8 mm away from the focus. Considering that the size ranges of the long and short axes of the right atrium are 3.4 - 5.3 cm and 2.6 - 4.4 cm respectively, the size of the aorta is 2.0 - 3.0 cm, and the diameter of the superior vena cava in adults is 2.1 cm ± 0.7, the HIFU technology can increase the temperature in the blood flow without heating the surrounding tissue. Since the blood itself is mixed and flowing, the heat dissipates and any long-term heating effects are limited. The measurement of heat dissipation is performed using ultrasonic thermography.

[0052] According to another embodiment, the cardiac output is measured by the thermal dissipation of a "bolus" by the blood flow in the heart. By placing the focus of HIFU and the measurement point of thermography closer to each other, the amplitude of the thermal dilution profile increases. In some examples, when combining the heat rise and measurement at one location, thermal dilution or heat dissipation is measured. This provides information on the flow rates in the various chambers of the heart.

[0053] According to yet another embodiment, a bolus of cold saline for thermal dilution is used in combination with the ultrasonic thermography described above.

[0054] According to yet another embodiment, the frequency of thermal dilution is used to increase sensitivity. The thermal dilution profile shows a gradual dissipation of temperature by the blood flow (when CO is given) following a sharp peak. When a bolus of 0°C cold saline is given, the temperature difference between the bloods is large and a sharp profile is seen. When using HIFU, a local area of the blood flow is heated. However, the body is more sensitive to heat rise than to a lower temperature. Using the techniques described in this disclosure, the thermal dilution profile has a smaller amplitude compared to the currently known cold saline bolus method.

[0055] By using the thermal dilution technique of this disclosure, a higher measurement frequency can be achieved. By repeatedly using HIFU heating and ultrasonic thermography, the resulting thermal dilution curve reflects the frequency profile, which can be analyzed using the FFT signal processing method. For example, when CO is high enough and a flow is created to completely dissipate the temperature "injection", a curve and FFT as shown in FIG. 3 are obtained.

[0056] When CO is low at the same "temperature injection" frequency, the heat dissipation does not reach the baseline, which results in a higher average signal, which can be seen in the plot of the FFT at 0 Hz as shown in FIG. 4. The processor 206 detects this increase and shifts the "temperature injection" frequency to keep the system in an equilibrium state.

[0057] FIGS. 3 and 4 show thermal dilution curves according to various embodiments of this disclosure.

[0058] Referring to FIG. 3, a normal thermal dilution curve (left) is shown together with the frequency of "temperature injection" as the first peak (once per minute, 0.01667 times per second), and the corresponding FFT (right) showing the average signal at 0 Hz, i.e., the "bias" of the signal.

[0059] Referring to FIG. 4, the low CO thermal dilution curve (left) is shown together with the corresponding FFT (right) showing the frequency of "temperature injection" (once per minute, 0.01667 times per second) as the first peak, and the average signal at 0 Hz, i.e., the "bias" of the signal. This bias is higher than that shown in FIG. 3 because the heat dissipation between "temperature injections" is incomplete.

[0060] FIG. 5 is a flowchart showing a method for performing non-invasive thermal dilution according to an exemplary embodiment of the present disclosure. Referring to FIG. 5, a flowchart of a method 500 for performing non-invasive thermal dilution using the apparatus 104 according to an exemplary embodiment of the present disclosure is shown.

[0061] At 502, high-intensity focused ultrasound (HIFU) is used to locally increase the temperature of the subject's blood. The ultrasonic transducer system 106 is configured to locally increase the temperature of the blood of the subject 102 using HIFU.

[0062] At 504, ultrasonic temperature measurement is used to measure the corresponding temperature change of the downstream blood. The ultrasonic transducer system 106 is further configured to measure the corresponding temperature change of the downstream blood using ultrasonic temperature measurement.

[0063] At 506, a thermal dilution curve is created based on the scale of the temperature change. The processing system 108 is configured to create a thermal dilution curve 112 on the user interface 110 based on receiving a signal regarding the scale of the temperature change from the ultrasonic transducer system 106.

[0064] The present disclosure may be implemented in hardware, or in a combination of hardware and software. The present disclosure may be implemented in a centralized manner in at least one computer system, or may be implemented in a distributed manner in which different elements are distributed over several interconnected computer systems. A computer system or other device / apparatus adapted to execute the methods described herein may be suitable. The combination of hardware and software may be a general-purpose computer system loaded with and executing a computer program that can control the computer system to execute the methods described herein when loaded and executed on the computer system. The present disclosure may be implemented in hardware having a part of an integrated circuit that also performs other functions. The present disclosure may be implemented as firmware that forms part of a media rendering device.

[0065] The present disclosure may be incorporated into a computer program product that includes all features enabling the implementation of the methods described herein and is configured to execute these methods when loaded and / or executed on a computer system. In this context, a computer program means a set of instructions expressed in any language, code, or notation, which is intended to cause a system having information processing capabilities to directly execute a specific function, or to execute a specific function after either or both of a) conversion into another language, code, or notation, and b) reproduction in a different material form.

[0066] The present disclosure is described with reference to specific embodiments, but it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted without departing from the scope of the present disclosure. In addition, many modifications may be made in order to adapt a particular situation or material to the teachings of the present disclosure without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the specific embodiments disclosed, but is intended to include all embodiments that fall within the scope of the appended claims.

[0067] All definitions defined and used in this specification are to be understood as taking precedence over dictionary definitions, definitions in incorporated references, and / or the ordinary meaning of the defined terms.

[0068] The subject matter described herein may also show that different components are included within other different components or are connected to other different components. Such an expressed architecture is merely illustrative, and it should be understood that in practice many other architectures that achieve the same function may be implemented. In a conceptual sense, any arrangement of components for achieving the same function is effectively "associated" so that the desired function is achieved. Thus, any two components combined herein for achieving a particular function can be regarded as "associated" with each other so that the desired function is achieved, regardless of the architecture or intermediate components. In this specification, the term "coupled" is used to refer to any kind of direct or indirect relationship between the components in question and is applicable to electrical, mechanical, fluid, optical, electromagnetic, electromechanical, or other connections. Similarly, any two components so associated can also be regarded as "operatively connected" or "operatively coupled" to each other for achieving the desired function, and any two components that can be so associated can also be regarded as "operatively couplable" to each other for achieving the desired function. Specific examples of being operatively couplable include, but are not limited to, components that are physically connectable and / or physically interact.

[0069] In the claims and the above specification, terms such as "first", "second", etc. are used in this specification only for ease of discussion and have no particular temporal or chronological meaning unless otherwise indicated.

[0070] In the claims and in the foregoing specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "holding," "consisting of," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" are closed or semi-closed transitional phrases, respectively.

[0071] As used in the specification and claims, the indefinite articles "a" and "an" are to be understood to mean "at least one" unless the contrary is clearly indicated.

[0072] As used herein, the terms "or" or "and / or" are inclusive and not exclusive, unless otherwise explicitly indicated or the context otherwise requires. Thus, as used herein, "A or B" means "A, B, or both" unless otherwise explicitly indicated or the context otherwise requires. Further, "and" is both conjunctive and disjunctive, unless otherwise explicitly indicated or the context otherwise requires. Thus, as used herein, "A and B" means "A and B jointly or severally" unless otherwise explicitly indicated or the context otherwise requires.

[0073] As used in the specification and claims, with respect to a list of one or more elements, the phrase "at least one" is to be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of every element specifically recited in the list of elements, and not excluding any combinations of elements in the list of elements. This definition allows for the optional presence, in addition to elements explicitly identified in the list of elements to which the phrase "at least one" refers, of elements other than those so identified, whether or not related to those elements specifically identified.

[0074] As used in this application and the claims, the term "one or more" in connection with a list of items can mean any combination of the items in the list. For example, the term "one or more of A, B, or C" means A, B, C, A and B, A and C, B and C, or A, B, and C.

[0075] As described in more detail above, one or more processors, other units, the like, and / or combinations thereof can perform the functions of some of the items recited in the claims.

[0076] As described in more detail above, a computer program is stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may be distributed in other forms, such as via the Internet or other wired or wireless electrical communication systems.

[0077] In any method discussed in this specification that includes two or more steps or acts, it should be understood that, unless the contrary is clearly indicated, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited. Further, such a method can include additional or alternative steps or acts. The mere fact that certain means are recited in different dependent claims does not indicate that combinations of these means cannot be used advantageously, as used in the claims.

[0078] From the foregoing description, those skilled in the art will appreciate that the broad techniques of the embodiments of the present disclosure can be implemented in a variety of forms. Accordingly, although the embodiments of the present disclosure have been described in connection with specific examples thereof, other modifications will become apparent to those skilled in the art upon consideration of the drawings, specification, and following claims, and the true scope of the embodiments of the present disclosure should not be so limited.

Claims

1. An apparatus for performing non-invasive thermodilution, An ultrasonic transducer system having one or more ultrasonic transducers or transducer arrays, Using high-intensity focused ultrasound (HIFU), the temperature of the subject's blood is locally increased, and Ultrasonic thermometry is used to measure the corresponding temperature change in the blood downstream. The ultrasonic transducer system is configured as follows: A processor communicatively coupled to the ultrasonic transducer system, configured to create a thermal dilution curve based on receiving a signal relating to the measure of the temperature change from the ultrasonic transducer system, and An apparatus for performing non-invasive thermal dilution, having [a specific feature / feature].

2. The apparatus according to claim 1, wherein the ultrasonic transducer system is configured to deliver a bolus into the bloodstream of the subject in order to locally increase the temperature of the blood using high-intensity focused ultrasound.

3. The apparatus according to claim 2, wherein the bolus is a cold saline solution.

4. The apparatus according to claim 2, wherein the temperature of the bolus is different from the temperature of the subject's blood flow.

5. The apparatus according to claim 1, wherein the ultrasonic transducer system measures the blood flow rate of the subject.

6. The apparatus according to claim 1, wherein the processor is configured to derive the cardiac output of the subject from the thermal dilution curve based on the heat dissipation of the bolus by blood flow in the subject's heart.

7. The apparatus according to claim 1, wherein the processor is configured to analyze the thermal dilution curve using a frequency profile based on signal processing.

8. The apparatus according to claim 7, wherein the processor is configured to analyze the thermal dilution curve using one of the fast Fourier transform (FFT) signal processing and impulse response functions.

9. The apparatus according to claim 1, wherein the amplitude of the thermal dilution profile of the thermal dilution curve is increased by placing the focal point of the high-density focused ultrasound and the measurement point of the temperature measurement closer to each other.

10. The apparatus according to claim 2, wherein the frequency of temperature rise and dissipation is selected such that the blood temperature rises immediately after the complete heat dissipation of the bolus in order to obtain a low cardiac output that alters the frequency profile of the thermal dilution curve.

11. The apparatus according to claim 10, wherein the processor is configured to detect from the ultrasonic transducer system an increase in the average signal due to a lower cardiac output and lower bolus heat dissipation than the baseline, even with the same frequency of blood temperature rise, and the processor is configured to shift the frequency of temperature rise and dissipation when it detects the increase in the average signal.

12. When an appropriate computer or processor executes instructions for the apparatus for performing non-invasive thermal dilution according to Claim 1, Using high-intensity focused ultrasound (HIFU), the temperature of the subject's blood is locally increased, Using ultrasonic thermometry, the corresponding temperature change of the blood downstream is measured, Creating a thermal dilution curve based on the scale of temperature change and A computer program product having a computer-readable medium containing computer-readable code configured to cause the computer or processor to execute a method for performing non-invasive thermal dilution having [a certain characteristic].

13. The computer program product according to claim 12, wherein locally increasing the temperature of the blood using high-intensity focused ultrasound is performed to administer a bolus into the bloodstream of the subject.

14. The computer program product according to claim 13, comprising selecting the frequency of temperature rise and dissipation such that the blood temperature rises immediately after the complete heat dissipation of the bolus in order to obtain a low cardiac output that changes the frequency profile of the thermal dilution curve.

15. A computer program product according to claim 14, which has the ability to detect an increase in the average signal due to a lower cardiac output and lower bolus heat dissipation than the baseline, even with the same frequency of blood temperature rise, and when an increase in the average signal is detected, shifts the frequency of temperature rise and dissipation.

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