Abstract:
An ultrasonic Doppler probe is provided for use in connection with non-invasive Doppler imaging of fluid flow within the human body. The Doppler probe can be selectively operated at more than one frequency during the course of a Doppler imaging examination thereby enhancing the resolution of the image obtained while also increasing the effective depth of the image. The probe of the present invention employs piezo-electric materials for the formation of acoustic transmitting and receiving transducers that are positioned within the probe to allow the probe to be selectively operated at a number of different frequencies spanning no more than one octave in frequency range.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is related to and claims priority from earlier filed U.S. Provisional Patent Application No. 60/953,014, filed Jul. 31, 2007. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to an ultrasonic probe for non-invasive measurement of fluid flow within the human body. More specifically, the present invention relates to an ultrasonic Doppler probe for measuring fluid flow within the human body that incorporates a dual frequency acoustical transducer, thereby allowing operation of the probe at both higher and lower frequencies without the need for the operator to change probes. 
         [0003]    As ultrasonic technology has improved, non-invasive ultrasonic diagnostic equipment has become an indispensable tool for clinical use. For many years, real-time B-mode ultrasound imagers have been used in connection with the investigation and imaging of stationary soft tissue structures within the human body. In addition, the more recent development of Doppler ultrasound scanners has facilitated the non-invasive investigation of moving fluids within the human body. In fact, Doppler ultrasound has become the standard in available techniques for non-invasively detecting and measuring the velocity of moving structures within the human body, and particularly to provide a real time estimate of the blood velocity traveling at various points within the body. 
         [0004]    The basic scientific principal underlying Doppler ultrasonography is based on the fact that ultrasonic waves, when directed at a moving object, undergo a frequency shift upon reflection and/or scattering by that object. Generally, the magnitude and the direction of the frequency shift in turn provides information regarding the motion of the object being observed. In other words, the magnitude of the frequency change is dependent upon how fast the object is moving. In this context, there are several different depictions of blood flow that are produced through medical Doppler imaging, including color flow imaging, power Doppler and spectral sonograms. Color flow imaging (CFI), is employed for imaging a whole region of the body and displays a real-time image of mean velocity distribution. CFI provides an estimate of the mean velocity of flow with a vessel by color coding the information and displaying it, super positioned on a dynamic B-mode image or black and white image of anatomic structure. While CFI displays the mean or standard deviation of the velocity of observed objects, such as the blood cells, in the given region, power Doppler (PD) in contrast displays a measurement of the amount of moving objects in the area. A PD image is an energy image wherein the energy of the flow signal is displayed. Thus, PD depicts the amplitude or power of the Doppler signals rather than the frequency shift. This allows detection of a larger range of Doppler shifts and thus better visualization of small vessels. In all of these technologies, however, the images produced show only the direction of flow and do not provide any no velocity information. Finally, spectral Doppler or spectral sonogram utilizes a pulsed wave system to interrogate a single range gate or sampling volume and displays the velocity distribution as a function of time. 
         [0005]    It is also of note that in the prior art, Doppler imaging is done using different acoustical frequencies, where the selection of acoustical frequency is a compromise between resolution and the ability to perceive the internal structure being imaged. This compromise is based generally on the fact that while higher frequency Doppler waves provide higher resolution they do not penetrate into the body as deeply, lower frequencies penetrate more deeply but the penetration depth is achieved at the expense of resolution. A processor is then employed to receive the electrical signals from the Doppler probe and operate upon them to determine the information that is to be provided to the user on the display. In some systems, the processor generates an electrical signal that is converted and translated in the probe as an acoustic signal, while in other systems the probe itself generates the signal to be transmitted. Similarly, in some systems, the probe simply converts the received acoustic signal to an electrical signal that is transferred to the processor while in others, the probe processes the electrical form of received acoustic signal so that it at a different (lower) frequency and then provides the converted data to the processor. 
         [0006]    The difficulty that is encountered in the prior art is that the currently available ultrasound probes operate at only a single frequency. As a result the operator must change probes to employ a different acoustical frequency for a portion of the examination. Accordingly, there is a need for a single ultrasonic probe that can be selectively operated at more than one frequency, thereby eliminating the need for the operator to switch probes during the investigation process. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    In this regard, the present invention provides for a Doppler probe that can be selectively operated at more than one frequency during the course of a Doppler imaging examination. The probe of the present invention employs piezo-electric materials for the formation of acoustic transmitting and receiving transducers that are positioned within the probe to allow the probe to be operated at a number of different frequencies spanning no more than one octave in frequency range. 
         [0008]    In one embodiment the probe of the present invention includes an acoustic transducer, a receiver and an operator control switch to selectively to select the frequency of operation from either of two predetermined frequencies and to show which frequency of operation is being used. 
         [0009]    In an alternate embodiment the switching function is transferred from the probe and implemented via a processor based control selector. 
         [0010]    In another alternate embodiment the transmitting and receiving components are provided in the processor so that the probe itself essentially contains only the acoustic transducer and the probe accepts a high frequency electrical signal from the processor for acoustic transmission and the probe provides the processor with the high frequency signal received by the receiving section of the acoustic transducer. 
         [0011]    In yet another alternate embodiment, the signals obtained by the receiving section of the acoustic transducer are converted to digital form by an analog-to-digital converter (A/D) and the resulting digital information is transferred to the processor for further processing such as complex demodulation and Doppler frequency extraction. 
         [0012]    In still a further alternate embodiment, a self-contained probe is provided that includes a wireless interface and a battery in order to provide its own power. The probe converts the received signals to a digital signal that is transmitted via the wireless interface to the processor. 
         [0013]    It is therefore an object of the present invention to provide a probe assembly for use in connection with ultrasonic Doppler imaging, which includes acoustical transducers therein that allow selective operation across at least two different frequencies. It is a further object of the present invention to provide a probe for use in ultrasonic Doppler imaging that includes acoustical transmitter and receiver components capable of selectively operating across at least two distinct frequencies while transmitting the information collected by the receiver to a processing device. It is still a further object of the present invention to provide a self contained probe for use in ultrasonic Doppler imaging that can be selectively operated across at least two distinct frequencies while wirelessly transmitting the information collected by the receiver to a processing device. 
         [0014]    These together with other objects of the invention, along with various features of novelty that characterize the invention, are pointed out with particularity in the claims annexed hereto and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated a preferred embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    In the drawings which illustrate the best mode presently contemplated for carrying out the present invention: 
           [0016]      FIG. 1  is a schematic depiction of an ultrasonic probe in accordance with the teachings of the present invention; 
           [0017]      FIG. 2  is a schematic depiction of the ultrasonic probe of  FIG. 1  with additional operational components depicted; 
           [0018]      FIG. 3  is a schematic depiction of a first alternate embodiment ultrasonic probe in accordance with the teachings of the present invention; 
           [0019]      FIG. 4  is a schematic depiction of a second alternate embodiment ultrasonic probe in accordance with the teachings of the present invention; 
           [0020]      FIG. 5  is a schematic depiction of a third alternate embodiment ultrasonic probe in accordance with the teachings of the present invention; and 
           [0021]      FIG. 6  is a schematic depiction of a fourth alternate embodiment ultrasonic probe in accordance with the teachings of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0022]    Now referring to the drawings, a schematic depiction of the ultrasonic probe of the present invention is shown and generally illustrated at  10  in  FIG. 1 . As was stated above, the present invention is directed at providing an ultrasonic probe  10  that is selectively operable over at least two different frequencies, thereby allowing an operator to conduct an ultrasonic examination across differing ultrasonic frequencies without having to change probes. In this regard, in a preferred embodiment the probe  10  of the present invention generally includes an acoustic transducer  12  having a transmit section  14  that creates and transmits an acoustic signal from a high frequency electrical signal and a receive section  16  that receives a reflection of the transmitted acoustic signal and converts the received reflection into an electrical signal. Further, the probe  10  includes a selection switch  18  that allows the user to selectively determine a frequency at which the acoustic signal is transmitted. 
         [0023]    As will be appreciated by one skilled in the art, the transmit section  14  in the acoustical transducer  12  is formed from a piezo-electric material that vibrates in response to electrical signals, thereby generating sound waves corresponding to the electrical signal. In this regard, a driver in the form of an oscillator  20  is used to generate a high frequency electrical signal having a wavelength that corresponds to the frequency at which the transmitter  14  in the transducer  12  is to be operated. In other words, the oscillator  20  generates a high frequency electrical signal that causes the piezo-electric material in the transmitter  14  to vibrate thereby emitting ultrasonic waves. In contrast to the prior art, the present invention employs a controllable oscillator  20  that generates a selectively variable frequency electrical signal in response to the frequency selection switch  18 . As a result, with the frequency selection switch  18  in a first position, the controllable oscillator  20  generates a first electrical signal that in turn drives the transmit section  14  of the acoustic transducer  12  at a first frequency. When the selection switch  18  is moved to a second position, the controllable oscillator  20  generates a second electrical signal that in turn drives the transmit section  14  of the acoustic transducer  12  at a second frequency. Further, the selector switch  18  also provides a signal to a processor  22  with which the ultrasonic probe  10  is interfaced thereby alerting the processor  22  to the frequency at which the acoustical transducer  12  is operating. This information is necessary so that the processor  22  can properly interpret the signal being transmitted by the transmit section  14  and returned by the receiver section  16 , so that it can display the frequency in use to the operator and so that it can include the information regarding the frequency being used in the data record of the test. 
         [0024]    In this regard, the probe  10  of the present invention includes an acoustical transducer  12  that can be selectively operated at a variety of different frequencies thereby allowing a comprehensive Doppler examination to be performed without the need for switching between multiple probes. Preferably, the range of multiple frequencies is limited to a range that falls into a single octave range. For example, the probe  10  can be selectively operated at the pair of frequencies of 5 MHz and 8 MHz or the pair of frequencies of 2.1 MHz and 3.9 MHz. 
         [0025]    Turning now to  FIG. 2 , in addition to including the above described elements, the probe  10  of the present invention preferably includes a frequency controller  24  that interprets the input from the frequency selection switch  18  to select and change the signal that is being generated by the controllable oscillator  20  In this regard, the frequency controller  24  serves to control the controllable oscillator  20  by providing a drive signal to the controllable oscillator  20  that in turn generates and transmits a high frequency electrical signal to the transmitter  14  in the acoustical transducer  12 . The controllable oscillator  20  also provides a signal to the signal demodulator  26  on the receiver side  16  of the probe  10  in order to allow the demodulator  26  to correctly interpret the signals received from the receiver  16 . The selector switch  18  may also send a signal to a frequency indicator  28  such as a lamp, an LED or an LCD display that visually shows the operator which operational frequency has been selected. The probe  10  of the present invention may also include a transmit amplifier  30  to amplify the electrical signal generated by the controllable oscillator  20  before passing it along to the transmitting section  14  of the acoustic transducer  12  and a receiving amplifier  32  to accept the signal from the receiving section  16  of the acoustic transducer  12  and amplify it for further processing. Further, the probe  10  may include an I-Q demodulator  26  and filters  34  to translate the received signal to a complex baseband form in order to perform Doppler processing within the processor  22 . 
         [0026]    In addition to the embodiment detailed above, there are a number of possible alternative embodiments of the present invention. In a first alternative embodiment, as depicted in  FIG. 3 , the functions of the frequency selector switch  18  and the frequency indicator  28  are removed from the probe  110  and implemented in the processor  122 . The frequency selection may in this embodiment be effectuated by a physical selector switch  18  or may be software implemented. The signal instructing the controllable oscillator  20  which one of the two predetermined frequencies to use is then is provided by the processor  122  by to the probe  110 . 
         [0027]    In a second alternative embodiment, depicted at  FIG. 4 , the probe  210  only contains the acoustic transducer  12  while the remaining transmit and receiving components, or major portions thereof, are relocated to the processor  222 . In this embodiment, the probe  210  itself essentially contains only the acoustic transducer  12  with the receiving section  16  and the transmit section  14 . The probe  210  accepts a high frequency electrical signal from the controllable oscillator  20 , which in this embodiment is located within the processor  222 , via the amplifier  30 . In response to the signal from the controllable oscillator  20 , the transmitter  14  generates an acoustic transmission that is in turn received in the receiver  16  and is provided to the processor  222  as a high frequency signal. In this alternative implementation, while the selector switch  18  and frequency indicator  28  are depicted as being provided within the probe  210 , clearly the selector switch  18  and frequency indicator  28  may be provided in the processor  222  as well as described above with regard to the earlier embodiment in  FIG. 3 . 
         [0028]      FIG. 5  depicts a third alternative embodiment wherein communication between the probe  310  and the processor  322  is effectuated via digital communication signals. The signals received at the receiving section  16  of the acoustic transducer  12  are converted into a digital signal using an analog-to-digital converter (A/D)  324  and the resulting digital information is transferred to the processor  322  for further processing such as complex demodulation and Doppler frequency extraction. Alternatively, the probe  310  may contain a digital signal processor  327  that performs some of the latter processing steps, thereby lowering the data rate of the information to be transferred to the processor  322 . In such cases, the digital signal processor  327  receives information on the frequency in use from the frequency controller  24 . On the transmit side, the frequency controller  24 , controllable oscillator  20 , selector switch  18 , frequency indicator  28  and transmit amplifier  30  may be contained in the probe  310  as shown. Further, any portion of these components may also be contained within the processor  322  as described above at  FIG. 4 . In any case, in this embodiment, a digital signal is generated by the frequency controller  24  that is then transmitted to a digital-to-analog converter (D/A)  326  where the digital signal is processed into an analog signal for use by the controllable oscillator  20  in generating the transmit signal. In all other respects the present embodiment operates as described above in the wholly analog embodiments. 
         [0029]    Finally, in a fourth alternative embodiment depicted at  FIG. 6 , a wireless self-contained probe  410  in accordance with the teachings of the present invention is provided. In this embodiment, in addition to the features described in the third alternate embodiment at  FIG. 5  above, the probe  410  also includes a power source  428  therein such as a battery. Further, the probe  410  includes a wireless digital interface transmit/receive module  430  that communicates with a corresponding wireless transmit/receive module  432  in the processor  422  thereby eliminating the need for cabling between the probe  410  and the processor  422 . This allows wireless digital communication between the prove  410  and the processor  422 . In this embodiment, it is preferred that all of the analog components be positioned on the probe  410  thereby requiring that only digital signals be transmitted wirelessly. 
         [0030]    It should be appreciated that in the scope of the present invention the important point of novelty is that the probe assembly allows operation over at least two different signal frequencies without requiring that the user switch probes. In this regard, it can therefore be seen that the present invention provides a novel and useful ultrasonic probe assembly that enhances the operator&#39;s ability to perform non-invasive ultrasonic examinations while enhancing the overall image obtained and reducing the time required to obtain a high quality image. By allowing the operator to selectively operate at multiple frequencies, Doppler images can be obtained that have both improved resolution with an increased depth of penetration within the human body. For these reasons, the instant invention is believed to represent a significant advancement in the art, which has substantial commercial merit. 
         [0031]    While there is shown and described herein certain specific structure embodying the invention, it will be manifest to those skilled in the art that various modifications and rearrangements of the parts may be made without departing from the spirit and scope of the underlying inventive concept and that the same is not limited to the particular forms herein shown and described except insofar as indicated by the scope of the appended claims.