Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-04-27
2002-08-20
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S459000
Reexamination Certificate
active
06436045
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to method and apparatus which, under user control, modify an ultrasound system's output waveform to efficiently disrupt contrast agent and subsequently returns the waveform to a predefined format.
Current ultrasonic imaging systems make use of contrast agents in circulation to enhance ultrasound returns. Contrast agents are substances which strongly interact with ultrasound waves and return echoes which may be clearly distinguished from those returned by blood and tissue. The most popular contrast agents are microbubbles which, using known algorithms, provide a readily detectable nonlinear behavior in certain acoustic fields. Microbubbles are especially useful for imaging the body's vascular system by injection into veins and arteries, from which they are subsequently filtered by the lungs, kidneys and liver. Microbubbles generally comprise coated gas bubbles. The coating shells serve to protect the gas from diffusion into the blood stream, making the microbubbles stable in the body for a significant period of time.
The shells of the microbubbles can be caused to rupture, thereby producing an easily distinguishable echo, by appropriately adjusting the output waveform of an ultrasonic transducer. Known ultrasound systems and methods only change one parameter, power, in the output waveform to rupture microbubbles. The present inventors have recognized that a variety of parameters can be adjusted to optimize the rupturing of microbubbles. In any event, for purposes of the present invention, the most significant feature of contrast agents is that not only do they produce an easily detectable echo when isonified with low MI ultrasound, but they also produce an easily distinguishable echo when they are burst with high MI ultrasound. This behavior makes contrast agents equally useful in two popular imaging modes: low power imaging and triggered imaging.
Low power imaging modes use a low MI signal to simply watch contrast agent travel with the blood flow in a region of interest (ROI). In situations of rapid replenishment, such as when imaging a heart chamber, an acoustic power level of around 0.5 MI, is used to reduce the destruction of the contrast agent to a point where circulatory replenishment is sufficient to keep the cavity well opacified. In situations where the circulatory replenishment is much slower, such as in myocardial tissues, the power level must be reduced even further, so as to keep a sufficient number of non-disrupted bubbles in view.
The low power imaging mode becomes even more valuable when all of the contrast agents within the ROI are ruptured (or “disrupted”), as with a high MI ultrasound pulse, and the sonographer can watch the re-introduction of contrast agent into the ROI. This allows an analysis of the rate of blood flow and, more particularly, perfusion. However, it is difficult for a sonographer to quickly and accurately set parameters in the ultrasound system to produce a waveform that the bursts the contrast agent and then reset the affected parameters back to the values required by the low power imaging mode. Sonographers typically push slide controls affecting the power output of the transducer to a maximum level and then pull them back into position. Not only is this an inexact procedure, but only adjusts the power of the ultrasound signal, which results in an inefficient use of acoustic power.
The triggered imaging mode generates high MI pulses at a timing dictated by a physiological signal, such as an ECG signal. The resulting image clearly shows the bursting of the contrast agent. While this is useful in and of itself, it becomes more useful when a series of images are produced at different timing. For example, producing one image at a first heart beat, skipping the next heat beat and producing a second image, skipping two heartbeats and producing a third image, skipping three heartbeats and producing a fourth image, etc . . . Such a series of images can be analyzed to plot a rate of blood flow and, more particularly, perfusion.
The triggered imaging mode requires a high degree of competence on the part of the sonographer. In between triggered frames, the image is frozen to the last frame. Thus, the sonographer must wait an increasing amount of time between images to re-establish visual confirmation of the imaging plane. Even with real time visual feedback (as in the low power imaging mode), it takes a great deal of patience and practice to hand hold the transducer against a patient without disrupting the imaging plane. Without visual feedback (as in the triggered mode), it is extremely difficult to control the transducer so that the imaging plane is not disrupted. Many times the sonographer tries to exit the triggered mode and use the low power mode to re-establish real time visual contact, adjust the imaging plane and then re-enter the triggered mode to complete the image series. This activity requires the sonographer to change a variety of settings using a plurality of controls, such as the transmit power, gain, focus, mode, etc . . . This can be so time consuming that the sonographer is forced to give another injection of contrast agent to complete the procedure. More importantly, such readjustment can cause the series of images produce by the trigger mode to be flawed, thereby reducing the accuracy of the subsequent analysis.
Current medical ultrasonic imaging systems provide the sonographer with a control panel for adjusting the ultrasound transmission and reception. Various types of buttons and switches are used to set the imaging mode, parameters of the ultrasound signal, and display options. Such control panels typically provide analog style rotary or slide controls (the signals from such controls are typically digital) to adjust the parameters of the ultrasonic transmission. For example, controls to adjust the acoustic power (MI) of the ultrasound signal typically provide a 30 db range of control. Such analog style rotary and slide controls do not permit quick and accurate changes in acoustic power. Digital controls can be even more cumbersome to adjust quickly. Currently, adjusting parameters of the ultrasound signal alone, or in conjunction with a change of imaging mode, is a complicated, time-consuming operation.
The present inventors have recognized a need for an operator interface that provides automated procedures, activated by a sonographer, for adjusting parameters of the ultrasound signal.
SUMMARY OF THE INVENTION
A user interface for an ultrasound system that provides a user activated automated control for adjusting parameters of an ultrasound signal output from a transducer. The ultrasound system is provided with a transducer that transmits ultrasound signals at a plurality of acoustic power levels and in response to activation of a control device adjusts parameters of the ultrasound waveform to, for example, disrupt contrast agent or provide a low MI viewing mode, and after a predetermined time readjusts the output of the transducer to a predefined form. The control device is preferably a routine that may be activated by a sonographer with a simple button, such as a push button, toggle switch, soft button, voice activation, etc . . . The duration may be fixed or based on another control, such as a dial or slide, set by the operator. Likewise, the parameters of the waveform may be fixed or based on another control, such as a dial or slide, set by the operator. The predefined form to which the transducer returns after the predetermined time may be set to the form of the output at time of activation, a fixed form, or a form based on another control, such as a dial or slide, set by the operator.
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patent: 6210335 (2001-04-01), Miller
patent: 6217516 (2001-0
Brock-Fisher George A
Poland Mckee D
Rafter Patrick G
Jaworski Francis J.
Koninklijke Phillips Electronics N.V.
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