Device for performing non-invasive thermal dilution

Abstract

An apparatus and method for performing non-invasive thermal dilution and creating a thermal dilution curve using high intensity focused ultrasound (HIFU) and ultrasound thermometry are provided. An apparatus of the present disclosure includes an ultrasound transducer system including one or more ultrasound transducers or transducer arrays and a processor communicatively coupled to the ultrasound transducer system. The ultrasound transducer system is configured to locally increase the temperature of the blood of the subject using the HIFU and measure corresponding temperature changes in the downstream blood using the ultrasound thermometry. The processor is configured to create a thermal dilution curve based on receiving a signal related to a measure of temperature change from the ultrasound transducer system.

Description

Technical Field

[0001] The present disclosure generally relates to thermal dilution devices and techniques. More specifically, 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 ultrasound thermometry. Background Art

[0002] Blood flow measurement is important both physiologically and clinically. Peripheral circulation is often reduced under pathological conditions. Blood flow in humans mainly distributes from large blood vessels (arteries) to peripheral regions and returns to large blood vessels (veins). Both the flow velocity and the blood vessel size change by large factors from peripheral blood vessels to large blood vessels. Blood flow and cardiac output are important parameters for measuring when a patient is hemodynamically unstable.

[0003] To measure blood flow and cardiac output, a thermal dilution method is employed, which involves injecting a finite amount of fluid at a certain temperature into the blood flow and recording the corresponding downstream temperature change. Cold fluid is often used as the indicator in the thermal dilution method because it is less harmful to blood and tissue compared to hot fluid. For example, a ~10 ml volume of cold saline or isotonic glucose solution close to 0 °C is typically used for cardiac output measurement in adults. The injected cold indicator mixes and dilutes in the warm blood flow and causes a slight temperature decrease in the downstream blood.

[0004] The thermal dilution method has several advantages; namely, the indicator is non-toxic and thus the measurement can be performed repeatedly, the dilution curve can be easily recorded by a thermistor placed in the blood vessel, and the recirculation component is small enough that the integration of the dilution curve can be performed accurately. The basic assumption of the indicator dilution method is that the indicator should not leak from the vascular system between the injection site and the detection site, which is not completely valid because heat can dissipate across the blood vessel wall. Due to the small ratio of surface area to volume per unit length, this effect is not significant in large blood vessels. Therefore, the thermal dilution method is more suitable for flow measurement in large blood vessels than in smaller blood vessels.

[0005] The thermal dilution techniques known to date employ a specially designed catheter, called a Swan-Ganz thermal dilution catheter, which is widely used for cardiac output measurement. Typically, the catheter is introduced from a peripheral vein through the right ventricle into the pulmonary artery. A bolus of cold saline or glucose solution is injected into the right atrium, 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] Different approaches have also been tried for the thermodilution method using intravascular heating. An electric heater can be used to transfer heat into the bloodstream. In this study, a heating wire was wound around a standard thermodilution catheter. When a sinusoidal heat signal of 0.02 Hz with an average power of 4 W was applied to the right ventricle of a sheep and the change in blood temperature in the pulmonary artery was detected simultaneously, the cardiac output could be measured in the range of 1.8 - 9.5 l / min. A correlation coefficient of 0.977 was obtained between the heating method and the standard rapid injection thermodilution measurement.

[0007] However, the above techniques are invasive and may be associated with the onset of complications.

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

[0009] Although thermodilution provides important clinical information, it is an invasive method associated with many complications. Thermodilution can also induce blockades in the right bundle branch and even in an intact heart. Additionally, the use of fluid boluses has implications for the fluid management of the patient. It is necessary to prevent fluid overload in the patient, and this has implications for the amount of fluid bolus that can be administered to the patient. Therefore, current thermodilution methods cannot be used in high measurement frequency settings. The current gold standard requires creating a fluid overload fluid bolus in the patient.

[0010] By using a non-invasive method to measure the thermodilution curve (which is the gold standard), the acceptability of the technique can be improved. However, current ultrasound techniques available for measuring cardiac output still require a skilled operator and are not continuous. Additionally, these thermodilution methods are still regarded as the gold standard, and clinicians use them to interpret and process the information obtained from these methods.

[0011] Therefore, there is a need for a system and method that aims to make the thermodilution method non-invasive, without the need for a skilled operator, while addressing the drawbacks of existing thermodilution techniques.

[0012] By comparing the described system with some aspects of the present disclosure, the limitations and drawbacks of conventional and traditional methods will become apparent to those of ordinary skill in the art, as set forth in the remainder of this application and with reference to the accompanying drawings.

[0013] HSIAOY I-SING ET AL: "Calibration and Evaluation of Ultrasound Thermography Using Infrared Imaging" (Ultrasound in Medicine and Biology, vol 42, no. 2, 5 Nov. 2015) discloses a method for calibrating and validating ultrasound thermography using infrared thermography.

[0014] ANANDA ET AL: "Noninvasive Measurement of Local Thermal Diffusivity Using Backscattered Ultrasound and Focused Ultrasound Heating" (Ultrasound in Medicine and Biology, New York, US, vol 34, no. 9, 1 September) discloses a non-invasive method for estimating local thermal diffusivity in situ during focused ultrasound heating using beamformed acoustic backscatter data. US2013 / 046178A1 discloses a method for monitoring temperature using ultrasound, and echo signals of diagnostic ultrasound irradiated to a treatment site are acquired, candidate temperature images are generated based on the echo signals using different temperature determination methods, and the generated candidate temperature images are fused.

[0015] US2006 / 129053A1 discloses a catheter for retrograde orientation in blood flow to determine blood flow rate by thermodilution measurement. Summary of the Invention

[0016] The claimed solution rooted in computer technology overcomes problems that particularly arise in the field of computer technology when performing thermodilution and creating thermodilution curves to measure the blood flow and cardiac output (CO) of an object.

[0017] A device and method for performing thermodilution are provided, which are substantially as shown in at least one of the accompanying drawings and / or in combination therewith, as more fully set forth in the claims.

[0018] These and other features and advantages of the present disclosure will be realized by viewing the following detailed description of the disclosure and the accompanying drawings, in which like reference numerals always refer to like parts.

[0019] In the claimed solution of the present disclosure, the device for performing non-invasive thermodilution includes an ultrasound transducer system. The ultrasound transducer system includes one or more ultrasound transducers or transducer arrays. The ultrasound transducer system is configured to: locally increase the temperature of the blood of an object using high-intensity focused ultrasound (HIFU), and measure the corresponding change in the temperature of the downstream blood using ultrasound thermometry. A processor communicatively coupled to the ultrasound transducer system is configured to create a thermodilution curve based on signals received from the ultrasound transducer system related to a measure of the change in temperature.

[0020] According to an embodiment, the ultrasound transducer system is configured to administer a bolus into the bloodstream of an object to locally increase the temperature of the blood using HIFU. In some embodiments, the bolus can be, but need not be limited to, a cold saline solution or a glucose solution. The temperature of the administered bolus is different from the temperature of the bloodstream of the object.

[0021] In some embodiments, the ultrasound transducer system measures the blood flow rate of the object. The processor is configured to derive the cardiac output of the object from the thermodilution curve based on the thermal dissipation of the bolus due to the blood flow in the heart of the object.

[0022] According to an embodiment, the processor is configured to analyze the thermodilution curve using frequency distribution based on signal processing. Techniques for analyzing the thermodilution curve can 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 distribution of the thermodilution curve is increased by placing the HIFU focus and the thermometry measurement point closer to each other.

[0024] In some other embodiments, the frequency of temperature increase and dissipation (also referred to as the temperature injection frequency) is selected such that the temperature of the blood is increased immediately after the complete thermal dissipation of the bolus to obtain a lower cardiac output that changes the frequency distribution of the thermodilution curve. The processor is configured to detect an increase in the average signal from the ultrasound transducer system, which is caused by a decrease in cardiac output when the frequency of blood temperature increase is the same and the thermal dissipation of the bolus is below the baseline. When an increase in the average signal is detected, the processor is configured to shift the frequency of dissipation and temperature increase.

[0025] The main objective of the present disclosure is to provide a non-invasive thermodilution method to avoid risks and serious complications when used in a clinical setting. Since fluids are not used to create temperature differences, there is no limit to the number of operations of the thermodilution technique of the present disclosure. By using HIFU heating and ultrasound thermometry or thermography in a repetitive manner, the resulting thermodilution curve reflects a frequency distribution, which can be analyzed using techniques such as but not limited to FFT signal processing and impulse response methods. Additionally, by selecting the temperature injection frequency such that the temperature increase occurs directly after complete heat dissipation, lower cardiac output (CO) alters the frequency distribution.

[0026] Furthermore, by removing the need for thermistors and replacing them with ultrasound thermography, the system is safer, easier to use, and less costly. The thermodilution distribution also has a lower amplitude compared to currently known cold saline bolus methods.

[0027] It should be understood that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (assuming these concepts are not mutually inconsistent) are expected to be part of the subject matter disclosed herein. In particular, all combinations of the claimed subject matter appearing at the end of the present disclosure are expected to be part of the subject matter disclosed herein. It should also be understood that terms explicitly employed herein that may also appear in any incorporated-by-reference disclosure should be accorded a meaning most consistent with the particular concepts disclosed herein.

[0028] These and other aspects of the various embodiments will be apparent from and 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 the appended claims, and by reference to the following drawings, in which:

[0030] Figure 1 is a block diagram of a system illustrating an apparatus for performing non-invasive thermodilution as described herein according to an exemplary embodiment of the present disclosure.

[0031] Figure 2 is a block diagram of an apparatus for performing non-invasive thermodilution according to an exemplary embodiment of the present disclosure.

[0032] Figure 3 and Figure 4 illustrate thermodilution curves according to various embodiments of the present disclosure.

[0033] Figure 5 is a flowchart of a method for performing non-invasive thermodilution according to an exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0034] As will be described in more detail below, in some embodiments discussed herein, the apparatus and method can advantageously be used to address a portion of the challenges in performing non-invasive thermodilution for measuring blood flow and cardiac output (CO) of a subject.

[0035] Figure 1 is a block diagram of a system illustrating an apparatus for performing non-invasive thermodilution as described herein according to an exemplary embodiment of the present disclosure. Referring Figure 1 to, system 100 is shown, which includes a subject 102, an apparatus 104 that includes an ultrasound transducer system 106, a processing system 108, a user interface 110, and a thermodilution curve 112 displayed on the user interface 110.

[0036] The ultrasound transducer system 106 includes one or more ultrasound transducers or transducer arrays, which may include suitable logic, circuitry, interfaces, and / or code that are operable to emit ultrasonic radiation or vibrations into the subject 102 to locally increase the temperature of the blood of the subject 102 using high-intensity focused ultrasound (HIFU). The ultrasound transducer system 106 is also configured to measure the corresponding temperature change of the downstream blood using ultrasonic thermometry.

[0037] The processing system 108 is communicatively coupled to the ultrasound transducer system 106 and the user interface 110. The user interface 110 may be implemented via one or more form factor devices, which may include but are not limited to smart phones, tablets, laptop computers, workstations, etc.

[0038] The ultrasound processing system 106, the processing system 108, and the user interface 110 may communicate with each other via communication technologies, which may include but are not limited to Internet-based communication, cloud-based communication, wired communication, wireless communication, etc. and / or combinations thereof.

[0039] The processing system 108 may include suitable logic, interfaces, and / or code that may be configured to create the thermodilution curve 112 displayed on the user interface 110 based on signals received from the ultrasound transducer system 106 related to a measure of the change in temperature.

[0040] In operation, the ultrasound transducer system 106 is configured to administer a bolus into the blood flow of the subject 102 to locally increase the temperature of the blood using HIFU. The bolus may be but is not limited to a cold saline solution or a glucose solution. The temperature of the bolus is different from the temperature of the blood flow of the subject 102. The ultrasound transducer system 106 is also configured to measure the corresponding temperature change of the downstream blood using ultrasonic thermometry.

[0041] In some embodiments, the ultrasound transducer system 106 measures the blood flow rate of the subject 102.

[0042] Figure 2 is a block diagram illustrating a device for performing non-invasive thermodilution according to an exemplary embodiment of the present disclosure. Referring Figure 2 to, a device 104 is shown, which includes a memory 202, a user interface 204, a processor 206, a communication unit 208, a transducer interface 210, a measurement component 212, a thermodilution curve creation component 214, and an analysis component 216.

[0043] The memory 202 may include, 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, the memory 202 may include any suitable volatile or non-volatile computer-readable storage media. The memory 202 may include suitable logic and / or interfaces that may be configured to store instructions (e.g., computer-readable program code) that may implement various aspects of the present disclosure.

[0044] The memory 202 is communicatively coupled to the user interface 204 and the processor 206.

[0045] The user interface 204 may be implemented via one or more form factor devices, which may include, but are not limited to, smartphones, tablets, laptops, workstations, etc.

[0046] The processor 206 may include suitable logic, interfaces, and / or code that may be configured to execute instructions stored in the memory 202 to implement various functions of the device 104 according to various aspects of the present disclosure. The processor 206 may also be configured to communicate with various modules of the device 104 via the communication unit 208.

[0047] The communication unit 208 may be configured to transfer data between the modules, engines, databases, memories, and other components of the device 104 for performing the functions discussed herein. The communication unit 208 may include one or more types of communication and utilize various communication methods to communicate within the device 104.

[0048] The transducer interface 210 couples the ultrasound transducer system 106 to the device 104. The ultrasound transducer system 106 includes one or more ultrasound transducers or transducer arrays, which may include suitable logic, circuitry, interfaces, and / or code that are operable to emit ultrasonic radiation or vibrations into the subject 102 to locally increase the temperature of the blood of the subject 102 using high-intensity focused ultrasound (HIFU).

[0049] The measurement component 212 may include suitable logic, interfaces, and / or code that may be configured to measure corresponding temperature changes in the downstream blood using ultrasonic thermometry.

[0050] The thermodilution curve creation component 214 may include suitable logic, interfaces, and / or code that may be configured to create the thermodilution curve 112 displayed on the user interface 204 based on signals received from the ultrasonic transducer system 106 related to a measure of the change in temperature.

[0051] The analysis component 216 may include suitable logic, interfaces, and / or code that may be configured to derive the cardiac output (CO) of the object 102 based on the thermal dissipation of the bolus due to blood flow in the heart of the object 102 according to the thermodilution curve 112. The analysis component 216 is configured to analyze the thermodilution curve 112 using frequency distribution based on signal processing, such as using fast Fourier transform (FFT) signal processing, impulse response functions, etc.

[0052] In an embodiment, the thermodilution curve amplitude of the thermodilution curve 112 is increased by placing the HIFU focus and the thermometry measurement point closer to each other.

[0053] According to various embodiments, the frequency of temperature increase and dissipation (also referred to as the temperature injection frequency) is selected such that the temperature of the blood is increased immediately after the complete thermal dissipation of the bolus to obtain a lower cardiac output that changes the frequency distribution of the thermodilution curve. The processor 206 is configured to detect an increase in the average signal from the ultrasonic transducer system 106, which is caused by a decrease in cardiac output when the frequency of blood temperature increase is the same and the thermal dissipation of the bolus is below the baseline. When an increase in the average signal is detected, the processor 206 is configured to shift the frequency of temperature increase and dissipation.

[0054] According to an embodiment, the ultrasonic transducer system 106 is configured to use focused ultrasound technology to change the temperature upstream of the sensing modality by creating "boluses" with different temperatures.

[0055] For example, HIFU generates local high temperatures in tumor tissue to cause tissue damage. The increase in temperature is localized and dissipates rapidly, and the environmental conditions are close to within 8 mm from the focus. Considering that the dimensions of the right atrium in the long axis and short axis range from 3.4 - 5.3 cm and 2.6 - 4.4 cm respectively, the dimension of the aorta is 2.0 to 3.0 cm, and the diameter of the adult superior vena cava 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 mixing and flowing, the heat will dissipate and any long-term heating effect will be limited. Ultrasonic thermography is used to measure the heat dissipation.

[0056] According to another embodiment, cardiac output is measured by the thermal dissipation of a "bolus" caused by blood flow in the heart. By placing the HIFU focus and the thermographic measurement point closer to each other, the amplitude of the thermodilution profile increases. In some cases, when heat addition and measurement are combined at one location, thermodilution or thermal dissipation is measured. This provides information on the flow rates of the individual chambers of the heart.

[0057] According to yet another embodiment, a cold saline bolus for thermodilution is used in combination with the ultrasonic thermography described above.

[0058] According to yet another embodiment, the thermodilution frequency is used to increase sensitivity. The thermodilution profile shows a sharp peak followed by a slow dissipation of temperature due to blood flow (given CO). When a 0°C cold saline bolus is administered, the temperature difference between the blood is large and a sharp profile can be seen. When using HIFU, a local area of the blood flow is heated. However, the body is more sensitive to heat addition compared to lower temperatures. Using the techniques described in the present disclosure, the thermodilution profile has a lower amplitude compared to currently known cold saline bolus methods.

[0059] By using the thermodilution technique of the present disclosure, a higher measurement frequency can be achieved. By using HIFU heating and ultrasonic thermography in a repetitive manner, the resulting thermodilution curve will reflect the frequency distribution, which can be analyzed using FFT signal processing methods. For example, when the CO is high enough to produce a flow that completely dissipates the temperature "injection", a curve and FFT as shown in Figure 3 can be obtained.

[0060] When the CO is decreased with the "temperature injection" frequency being the same, the thermal dissipation does not reach the baseline, which results in a higher average signal, which can be seen in the FFT plot at 0 Hz as shown in Figure 4 The processor 206 detects this increase and shifts the "temperature injection" frequency to maintain system balance.

[0061] Figure 3 and Figure 4 illustrate thermodilution curves according to various embodiments of the present disclosure.

[0062] Referring to Figure 3 , an illustration of a normal thermodilution curve (left) is shown, where the corresponding FFT (right) shows the frequency of the temperature injection (1 injection per minute, 0.01667 injections per second) as the first peak and the average signal, or the "bias" of the signal at 0 Hz.

[0063] Referring to Figure 4, showing an illustration of a low CO thermodilution curve (left), where the corresponding FFT (right) shows the frequency of the temperature injection as the first peak (1 injection per minute, 0.01667 injections per second) and the average signal, or the "bias" of the signal at 0 Hz. Due to incomplete heat dissipation between "temperature injections", this bias is higher as Figure 3 depicted.

[0064] Figure 5 is a flowchart illustrating a method for performing non-invasive thermodilution according to an exemplary embodiment of the present disclosure. Referring to Figure 5 , showing a flowchart of a method 500 for performing non-invasive thermodilution using the device 104 according to an exemplary embodiment of the present disclosure.

[0065] At 502, the temperature of the blood of the subject is locally increased using high-intensity focused ultrasound (HIFU). The ultrasound transducer system 106 is configured to locally increase the temperature of the blood of the subject 102 using HIFU.

[0066] At 504, the corresponding temperature change of the downstream blood is measured using ultrasound thermometry. The ultrasound transducer system 106 is also configured to measure the corresponding temperature change of the downstream blood using ultrasound thermometry.

[0067] At 506, a thermodilution curve is created based on a measure of the temperature change. The processing system 108 is configured to create a thermodilution curve 112 on the user interface 110 based on signals received from the ultrasound transducer system 106 related to the measure of the temperature change.

[0068] The present disclosure can be implemented in hardware or a combination of hardware and software. The present disclosure can be implemented in a centralized manner, in at least one computer system, or in a distributed manner, where different elements can be distributed over several interconnected computer systems. A computer system or other device / suitable equipment for performing the methods described herein may be appropriate. A combination of hardware and software may be a general computer system with a computer program that, when loaded and executed on the computer system, can control the computer system such that it performs the methods described herein. The present disclosure can be implemented in hardware that includes a portion of an integrated circuit that also performs other functions. The present disclosure can also be implemented as firmware that forms part of a media presentation device.

[0069] The present disclosure may also be embedded in a computer program product, which includes all the features enabling the implementation of the methods described herein, and when loaded and / or executed on a computer system, the computer program product may be configured to execute these methods. In this context, a computer program refers to any expression of a set of instructions in any language, code, or notation, which is intended to cause a system with information processing capabilities to directly execute a specific function, or to execute a specific function after any one or both of the following:

[0070] a) being converted into another language, code, or notation; b) being reproduced in a different material form.

[0071] Although the present disclosure has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted without departing from the scope of the present disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the present disclosure without departing from its scope. Therefore, the present disclosure is not intended to be limited to the specific embodiments disclosed, but the present disclosure will include all embodiments falling within the scope of the appended claims.

[0072] All definitions defined and used herein should be understood to control dictionary definitions, definitions in documents incorporated by reference, and / or the ordinary meaning of defined terms.

[0073] The subject matter described herein is sometimes illustrated with different components included within or connected to different other components. It should be understood that such depicted architectures are merely exemplary, and in fact, many other architectures that implement the same functions can be implemented. In a conceptual sense, any arrangement of components that implements the same function is effectively "associated" such that the desired function is achieved. Therefore, any two components combined herein to achieve a specific function can be considered "associated" with each other such that the desired function is achieved, regardless of the architecture or intermediate components. The term "coupled" can be used herein to refer to any type of direct or indirect relationship between the components discussed, and can apply to electrical, mechanical, fluid, optical, electromagnetic, electromechanical, or other connections. Similarly, any two components so associated can also be considered "operably connected" or "operably coupled" to each other to achieve the desired function, and any two components capable of being so associated can also be considered "operably coupled" to each other to achieve the desired function. Specific examples of operably coupled include, but are not limited to, physically mating and / or physically interacting components.

[0074] In the claims as well as in the above specification, the terms "first", "second", etc. may be used herein only to facilitate discussion and do not have a specific temporal or chronological meaning unless otherwise stated.

[0075] In the claims, as well as in the above description, all transitional phrases such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", "consisting of", etc. shall be understood to be open-ended, i.e., meaning including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

[0076] Unless otherwise expressly stated, the words "a" and "an" as used in this specification and the claims shall be understood to mean "at least one".

[0077] As used herein, unless otherwise expressly stated or the context otherwise indicates, the term "or" or "and / or" is inclusive rather than exclusive. Thus, herein, "A or B" means "A, B, or both", unless otherwise expressly indicated or indicated by the context. Additionally, "and" is both conjunctive and plural, unless otherwise expressly stated or the context otherwise indicates. Thus, herein, "A and B" means "A and B, jointly or severally", unless otherwise expressly stated or the context otherwise indicates.

[0078] As used in this specification and the claims, the phrase "at least one" with respect to a list of one or more elements shall 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 each element specifically listed within the list of elements, and not excluding any combination of the elements in the list of elements. This definition also allows that elements may optionally exist in addition to those specifically identified within the list of elements referred to by the phrase "at least one", whether related or unrelated to those specifically identified elements.

[0079] As used in this application and the claims, a list of items joined by the phrase "one or more of" may represent any combination of the listed terms. For example, the phrase "one or more of A, B, or C" may represent A; B; C; A and B; A and C; B and C; or A, B, and C.

[0080] As described in more detail above, one or more processors, other units, etc. and / or combinations thereof may implement the functions of several items recited in the claims.

[0081] As described in more detail above, a computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium provided together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

[0082] It should also be understood that, unless explicitly indicated to the contrary, in any method discussed herein that includes more than one step or action, the order of the steps or actions of the method is not necessarily limited to the order in which the steps or actions of the method are recited. Additionally, such a method may include additional or alternative steps or actions. As used in the claims, although certain measures are recited in mutually different dependent claims, this does not indicate that the combination of these measures cannot be used advantageously.

[0083] Those skilled in the art will understand from the foregoing description that the broad techniques of the embodiments of the present disclosure can be implemented in various forms. Thus, while the embodiments of the present disclosure have been described in connection with specific examples of the present disclosure, the true scope of the embodiments of the present disclosure should not be so limited, as other modifications will become apparent to those skilled in the art after studying the drawings, the specification, and the appended claims.

Claims

1. An apparatus for performing non-invasive thermodilution, comprising: an ultrasound transducer system including one or more ultrasound transducers or transducer arrays, the ultrasound transducer system being configured to: locally increase the temperature of the blood of an object using high-intensity focused ultrasound (HIFU); and measure a corresponding temperature change of the downstream blood using ultrasound thermometry; and a processor communicatively coupled to the ultrasound transducer system, wherein the processor is configured to create a thermodilution curve based on signals received from the ultrasound transducer system related to a measure of the temperature change.

2. The apparatus according to claim 1, wherein, the ultrasound transducer system is configured to administer a bolus into the bloodstream of the object to locally increase the temperature of the blood using HIFU.

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 bloodstream of the object.

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

6. The apparatus according to claim 1, wherein, the processor is configured to derive a cardiac output of the object from the thermodilution curve based on heat dissipation of the bolus caused by blood flow in the heart of the object.

7. The apparatus according to claim 1, wherein, the processor is configured to analyze the thermodilution curve using frequency distribution based on signal processing.

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

9. The apparatus according to claim 1, wherein, the thermodilution distribution amplitude of the thermodilution curve is increased by placing the HIFU focus and the temperature measurement point closer to each other.

10. The apparatus according to claim 2, wherein, the frequency of temperature increase and dissipation is selected such that the temperature of the blood increases immediately after complete heat dissipation of the bolus to obtain a lower cardiac output, and the lower cardiac output changes the frequency distribution of the thermodilution curve.

11. The apparatus according to claim 10, wherein, the processor is configured to detect an increase in the average signal from the ultrasound transducer system, the increase being caused by a decrease in the cardiac output and heat dissipation of the bolus below baseline when the frequency of blood temperature increase is the same, and wherein once the increase in the average signal is detected, the processor is configured to shift the frequency of temperature increase and dissipation.

12. A computer program product including a computer-readable medium having computer-readable code embodied therein, the computer-readable code being configured to cause a computer or processor to perform a method for performing non-invasive thermodilution when run by a suitable computer or processor, the method comprising: Locally increase the temperature of the blood of an object using high intensity focused ultrasound (HIFU); Measure the corresponding temperature change of the downstream blood using ultrasonic thermometry; and Create a thermodilution curve based on the measure of the temperature change.

13. The computer program product according to claim 12, wherein, locally increasing the temperature of the blood using HIFU includes administering a bolus into the bloodstream of the object.

14. The computer program product according to claim 13, comprising: selecting a frequency of temperature increase and dissipation such that the temperature of the blood increases immediately after complete thermal dissipation of the bolus to obtain a lower cardiac output, the lower cardiac output altering the frequency distribution of the thermodilution curve.

15. The computer program product according to claim 14, comprising: detecting an increase in the average signal due to a decrease in the cardiac output and a thermal dissipation of the bolus below baseline at the same frequency of temperature increase of the blood, and wherein once the increase in the average signal is detected, the frequency of temperature increase and dissipation is shifted.

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