Methods for the use of contrast agents in ultrasonic imaging
First Claim
1. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, and a processor for generating the acoustic imaging signal and extracting from the return signal information representing the concentration of contrast agent along the scan line wherein the contrast agent is depleted by an amount related to the power level of the acoustic imaging signal insonicating the contrast agent, a method for controlling the concentration of contrast agent within a range of generally linear response, comprising the steps of:
- determining from the return signal the relative concentration of contrast agent along the scan line, andfrom the relative concentration of the contrast agent, adjusting the characteristics of the acoustic imaging signal to increase depletion of the contrast agent when the concentration of contrast agent is higher than the linear range of response and decreasing the depletion of the contrast agent when the concentration of contrast agent is lower than the linear range of response.
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Abstract
Methods for use of contrast agents with an acoustic echographic imaging system, including controlling the concentration of contrast agent in a region of interest by adjusting the acoustic imaging signal to increase or decrease depletion of the contrast agent to the linear range of response. Adjustment of the signal includes dividing the received signal level by a power reduction ratio to re-normalize the signal level and compensating the signal power level. A spectral processor detects the concentration of the contrast agent in a gate marker window as the averaged ratio of energy around the second harmonic of the return signal versus energy around the fundamental frequency of the return signal, and includes a boundary detector for detecting a point of greatest change in value of the averaged ratios as a boundary between regions of interest. A well defined bolus of contrast agent in a region of interest is created by scanning to destroy contrast agent entering the region of interest during a predetermined initial interval. A desired contrast agent depletion patterns is generated by scanning a selected portion of the region of interest with a depletion acoustic signal having a power level and duration selected to create a desired contrast agent depletion pattern. The depletion acoustic signals may be separate and different from the acoustic image signals in one or more signal characteristics, including the arrangement, sequence, frequency, pulse length, number of pulses, power levels, focus profiles, apodization and apertures.
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Citations
21 Claims
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1. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, and a processor for generating the acoustic imaging signal and extracting from the return signal information representing the concentration of contrast agent along the scan line wherein the contrast agent is depleted by an amount related to the power level of the acoustic imaging signal insonicating the contrast agent, a method for controlling the concentration of contrast agent within a range of generally linear response, comprising the steps of:
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determining from the return signal the relative concentration of contrast agent along the scan line, and from the relative concentration of the contrast agent, adjusting the characteristics of the acoustic imaging signal to increase depletion of the contrast agent when the concentration of contrast agent is higher than the linear range of response and decreasing the depletion of the contrast agent when the concentration of contrast agent is lower than the linear range of response. - View Dependent Claims (2, 3)
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4. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal having a fundamental frequency and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, a spectral content measurement processor for detecting the concentration of the contrast agent along the scan line, comprising:
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a gate marker generator for generating a gate marker window for selecting at least one scan line and a position in the gate marker window along the selected scan line, a signal buffer connected to receive a return signal along the scan line and responsive to the gate marker signal to capture the return signal in the gate marker window, a second harmonic component energy detector for providing a second harmonic energy signal representing the second harmonic energy within the frequency band around the second harmonic of the captured return signal versus axial position along the selected scan line as the gate marker window is moved along the selected scan line, a fundamental frequency component energy detector for providing a fundamental frequency energy signal representing the fundamental frequency energy within the frequency band around the fundamental frequency of the captured return signal versus axial position in the gate marker window and along the selected scan line as the gate marker window is moved along the selected scan line, a ratio determiner for receiving the fundamental frequency energy signal output and the second harmonic energy signal output and generating a ratio output that represents the proportion of second harmonic energy to fundamental frequency energy versus position of the gate marker window along the selected scan line, and a ratio averager for receiving the ratio output and responsive to the gate marker window for selecting in a sub-window of the gate marker window the ratio output along the scan line and generating an averaged ratio output for each selected window of the ratio output wherein an averaged ratio output represents the concentration of contrast agent in the selected window. - View Dependent Claims (5, 6, 7)
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8. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal having a fundamental frequency and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, a boundary detector for detecting the boundary between regions of interest, comprising:
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a gate marker generator for selecting a scan line passing through the boundary between the regions of interest and for incrementally stepping a gate marker window along the scan line, a signal buffer connected to receive a return signal along the scan line and responsive to the gate marker signal to capture the return signal in the gate marker window, a second harmonic component energy detector for providing a second harmonic energy signal representing the second harmonic energy within the frequency band around the second harmonic of the captured return signal versus axial position along the selected scan line as the gate marker window is moved along the selected scan line, a fundamental frequency component energy detector for providing a fundamental frequency energy signal representing the fundamental frequency energy within the frequency band around the fundamental frequency of the captured return signal versus axial position in the gate marker window and along the selected scan line as the gate marker window is moved along the selected scan line, a ratio determiner for receiving the fundamental frequency energy signal output and the second harmonic energy signal output and generating a ratio output that represents the proportion of second harmonic energy to fundamental frequency energy versus position of the gate marker window along the selected scan line, and a ratio averager for receiving the ratio output and responsive to the gate marker window for selecting in a sub-window of the gate marker window the ratio output along the scan line and generating an averaged ratio output for each selected sub-window of the ratio output wherein an averaged ratio output represents the concentration of contrast agent in the selected sub-window, and a comparator for comparing the values of the averaged ratio at each step of the sub-window along the scan line and identifying the point of greatest change in value of the averaged ratios along the scan line, thereby identifying the point of greatest change in value of the averaged ratios along the scan line as the point of the boundary between the regions of interest.
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9. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal having a fundamental frequency and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, a spectral content measurement method for detecting the concentration of the contrast agent along the scan, comprising the steps of:
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generating a gate marker for selecting at least one scan line and a position along the selected scan line, capturing the return signal as a captured return signal in a region around the gate marker, generating a second harmonic energy signal representing the second harmonic energy within the frequency band around the second harmonic of the captured return signal versus axial position along the selected scan line as the gate marker is moved along the selected scan line, generating a fundamental frequency energy signal representing the fundamental frequency energy within the frequency band around the fundamental frequency of the captured return signal versus axial position along the selected scan line as the gate marker is moved along the selected scan line, generating a ratio output representing the proportion of second harmonic energy to fundamental frequency energy versus position along the selected scan line, and selecting a window of the ratio output along the scan line and generating an averaged ratio output for each selected window of the ratio output wherein an averaged ratio output represents the concentration of contrast agent in the selected window. - View Dependent Claims (10, 11, 12)
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13. In an acoustic echographic imaging system including a transducer for transmitting an acoustic imaging signal having a fundamental frequency and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent, a method for detecting a boundary between regions of interest, comprising the steps of:
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selecting a scan line passing through the boundary between the regions of interest and incrementally stepping a gate marker window along the scan line, capturing the return signal in the gate marker window, generating a second harmonic energy signal representing the second harmonic energy within the frequency band around the second harmonic of the captured return signal versus axial position along the selected scan line as the gate marker window is moved along the selected scan line, generating a fundamental frequency energy signal representing the fundamental frequency energy within the frequency band around the fundamental frequency of the captured return signal versus axial position in the gate marker window and along the selected scan line as the gate marker window is moved along the selected scan line, generating a ratio output representing the proportion of second harmonic energy to fundamental frequency energy versus position of the gate marker window along the selected scan line, selecting in a sub-window of the gate marker window the ratio output along the scan line and generating an averaged ratio output for each selected sub-window of the ratio output wherein an averaged ratio output represents the concentration of contrast agent in the selected sub-window, and comparing the values of the averaged ratio at each step of the sub-window along the scan line and identifying the point of greatest change in value of the averaged ratios along the scan line, thereby identifying the point of greatest change in value of the averaged ratios along the scan line as the point of the boundary between the regions of interest.
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14. In an acoustic echographic imaging system including a transducer for transmitting an acoustic signal and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent when a contrast agent is present along the scan line, a signal generator for generating the acoustic imaging signal at controllable power levels, a method for creating a well defined bolus of contrast agent in a region of interest being scanned with the acoustic imaging signal, comprising the steps of:
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introducing a flow of contrast agent into the region of interest, scanning the region of interest with an acoustic signal having a power level selected to destroy the contrast agent entering the region of interest at a rate to keep the concentration of contrast agent in the region of interest to a predetermined low, steady state level, and after a predetermined time has passed since the flow of contrast agent has begun, the end of that time being designated by a user of the system as the beginning of perfusion of the region of interest by a flow of contrast agent of a desired concentration, beginning image scanning of the region of interest at an acoustic imaging signal power level less than that selected to destroy the contrast agent. - View Dependent Claims (15)
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16. In an acoustic echographic imaging system including a transducer for transmitting an acoustic signal and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent when a contrast agent is present along the scan line, a signal generator for selectively generating the acoustic signal at selectable power levels, durations and intervals, a method for generating desired contrast agent depletion patterns in a region of interest, comprising the steps of:
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scanning the region of interest with an acoustic imaging signal and processing the return signal thereof to produce an image of the region of interest, and scanning at least a selected portion of the region of interest with an acoustic depletion signal having a power level and duration selected to create a desired contrast agent depletion pattern wherein the acoustic depletion signal is not used to produce an image. - View Dependent Claims (17, 18)
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19. In an acoustic echographic imaging system including a transducer for transmitting a plurality of acoustic scan lines to form an acoustic scan and receiving a return signal representing an image along a scan line, the return signal including contributions from a contrast agent when a contrast agent is present along the scan line, a signal generator for selectively generating the acoustic scan lines at selectable power levels, durations and intervals, a method for compensating for unwanted contrast agent depletion patterns in a region of interest and resulting from destruction of the contrast agent by the acoustic signal, comprising the steps of:
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producing acoustic imaging scan lines and processing return signals thereof to produce an image of the region of interest; and producing acoustic depletion scan lines in at least a selected portion of the region of interest, the acoustic depletion scan lines having a power level and duration selected to create a desired contrast agent depletion pattern, wherein the acoustic depletion scan lines are not used to produce an image. - View Dependent Claims (20, 21)
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Specification