Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1999-07-27
2001-01-23
Lateef, Marvin M. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
Reexamination Certificate
active
06176830
ABSTRACT:
TECHNICAL FIELD
The invention relates generally to a method and a system for selecting settings for process parameters in an ultrasonic examination and relates more particularly to selecting settings for process parameters upon switching an ultrasonic system from a two-dimensional mode of operation to a spectral Doppler mode of operation.
DESCRIPTION OF THE RELATED ART
Ultrasonic imaging techniques may be used to produce images of internal features of an object, such as tissues of a human body. A diagnostic ultrasonic imaging system for medical use forms images of internal tissues of the human body by electrically exciting an acoustic transducer element or an array of acoustic transducer elements to generate ultrasonic beams that propagate into the patient's body. Energy of the ultrasonic beams reflects off human tissues that present discontinuities or impedance changes to the propagating ultrasonic beams. The echoes from the tissues are sensed by the transducer and are converted into electrical signals that are amplified and decoded to provide interrogation information. Ultrasonic imaging provides physicians with the real-time images of the internal features of the human anatomy without resorting to more invasive exploratory techniques, such as surgery.
An ultrasonic system has a number of modes of operation. One set of modes can be referred to collectively as “two-dimensional modes.” Typically, frames of information are generated when the system is in one of the two-dimensional modes. Electrical signals are collected from the array of transducer elements to form each frame. The frame is a multi-pixel array in which each pixel corresponds to a location in a two-dimensional slice of the imaged tissue. Optionally, two-dimensional slices can be accumulated to form a three-dimensional ultrasonic image.
As an alternative to the two-dimensional modes of operation, an ultrasonic system can be operated in a spectral Doppler mode. In this mode, the interrogation takes place for a single target, such as a particular blood vessel. When the system is in the spectral Doppler mode, information may be processed to identify the velocity spectrum of the target over time. The results of the spectral Doppler mode of operation are conventionally presented by means of an audio signal that is responsive to a frequency spectrum, but visual displays are also used (e.g., the plotting of the velocity spectrum against time).
Returning to the set of two-dimensional modes of operation of the ultrasonic system, one such mode provides B-mode imaging. Echoes from a selected cross section are processed to form an image that is based on echo signal intensity. Conventionally, a grey-scale image provides a two-dimensional display of the cross section. Data returned from each transmission of a beam into the body of interest is used to determine a pixel value for the grey-scale image.
A second two-dimensional mode is referred to as colorflow imaging or BC imaging. In this mode, a color-coded velocity map is generated. At each pixel in the display, color is a function of the velocity of a corresponding physical region within a sample volume. Doppler shifts caused by blood flow are detected and used to determine the color of pixels. The color coding of pixels is often incorporated into grey-scale image information. Motion toward the acoustic transducer array may be represented by the color red, while motion away from the transducer array may be represented by the color blue. Unlike B mode operation, each pixel value of motion data is acquired by identifying differences in tissue positions over an “ensemble” of transmit-receive cycles. Thus, a time series of pixel values is compared to detect the changes in tissue location during the time series.
A third type of two-dimensional imaging is referred to as power mode imaging or BP mode imaging. This mode is similar to BC mode operation with respect to utilizing an ensemble of data frames to determine motion data, but the BP imaging is speed based, rather than velocity based. That is, the BP mode is direction independent. When an ultrasonic system is in the BP mode of operation, the displayed color for each pixel is a function of the speed of movement in the corresponding physical region of a sample volume. Red may be the selected color, with the intensity at each pixel being based upon the speed of motion within the physical region corresponding to the pixel.
Often, the spectral Doppler mode of operation follows two-dimensional imaging in order to provide information that is not available from the two-dimensional imaging. One of the limitations of colorflow imaging is described in U.S. Pat. No. 5,443,071 to Banjanin et al., which is assigned to the assignee of the present invention. Colorflow imaging measures blood flow velocity in a blood vessel by using a Doppler frequency shift which is obtained by analyzing the echoes received from the region of interest. However, the measure of blood flow velocity is a function of the angle of blood flow with respect to the direction of the interrogation beam. Thus, without information regarding the blood flow angle, the measured blood flow velocity is only an indication of the velocity in the direction of the interrogation beam. In order to overcome this deficiency, the operator (e.g., clinician) manually adjusts a Doppler “angle correct” setting. If a transducer array is not perpendicular to the vascular volume flow, an angle correct compensation may be used to provide a more accurate velocity measurement. The clinician may manually move the transducer array, may steer the interrogation beam from a stationary transducer array, or may provide angle correct compensation in computer processing (using the angle correct setting). As noted in the Banjanin et al. patent, the manual angle correction of blood flow velocity is often cumbersome and hard to repeat.
In addition to the error correct setting, there are settings of other operation parameters that are specific to the spectral Doppler mode of operation. For example, a Doppler pulse repetition frequency (PRF) must be set. The PRF setting determines the number of pulses that are transmitted per unit of time. The Doppler PRF is set to minimize the likelihood of interference when the beam is minimized. Another setting of concern is Doppler gain. The Doppler gain is the amplification of signals received from the transducer array. The gain is set higher if the signal strength is low. As another concern, the sample volume placement for the spectral Doppler mode is typically different than that of the two-dimensional mode. The spectral Doppler sample volume has a particular target which is much narrower than the sample volume of the preceding two-dimensional mode of operation.
Since there are a number of operation parameters that must be set when the spectral Doppler mode is initiated, the examination process is often time consuming. The clinician is required to determine the settings. It is not uncommon for the target of interest to move while the clinician is setting up the Doppler parameters (e.g., as a result of breathing). This causes the clinician to have to cycle through several mode-to-mode iterations. The process can be expedited by establishing default settings for the Doppler operation parameters. For example, the gain setting may be automatically set to unity. The default settings may be estimations based upon an “average” examination. The clinician can then fine tune the settings for the specific examination. While this basis for establishing initial settings reduces the time required for an examination, there are a large number of variables that play a role in determining the settings, so that very few examinations match the typical examination.
What is needed is a method and an ultrasonic system for reducing the complexity of the procedure of switching from one of the two-dimensional modes of operation to a spectral Doppler mode of operation, thereby reducing the time and potentially improving the results of Doppler examinations.
SUMMARY OF THE INVENTION
A method of
Lateef Marvin M.
Patel Maulin
Siemens Medical Systems Inc.
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