Ultrasonic imaging method and apparatus

• US 4,016,750 A
• Filed: 11/06/1975
• Issued: 04/12/1977
• Est. Priority Date: 11/06/1975
• Status: Expired due to Term

• Current Assignee: Stanford Research Institute (SRI International, Inc.)
• Original Assignee: Stanford Research Institute (SRI International, Inc.)
• Inventors: Green, Philip S.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Kreitman, Stephen A.
• Application Number:
  US05/629,594
• Time in Patent Office: 523 Days
• Field of Search: 73/67, 73/67.2, 73/67.7, 73/67.8 R, 73/67.5 R, 73/67.9, 73/71.5 US, 128/2 V, 128/2.05 Z
• US Class Current: 73/629
• CPC Class Codes: A61B 8/08 Detecting organic movements or changes, e.g. tumours, cysts, swellings A61B8/02 - A61B8/06 take precedence
• CPC Class Codes: G01N 29/0609 Display arrangements, e.g. colour displays indicating or recording in connection with measuring in general G01D
• CPC Class Codes: G01N 29/0645 Display representation or displayed parameters, e.g. A-, B- or C-Scan
• CPC Class Codes: G01N 29/343 pulse waves, e.g. particular sequence of pulses, bursts
• CPC Class Codes: G01N 29/4454 Signal recognition, e.g. specific values or portions, signal events, signatures
• CPC Class Codes: G01N 29/4463 Signal correction, e.g. distance amplitude correction [DAC], distance gain size [DGS], noise filtering
• CPC Class Codes: G01S 15/8954 using a broad-band spectrum
• CPC Class Codes: G01S 7/52046 Techniques for image enhancement involving transmitter or receiver image enhancement by image data processing G06T5/00
• CPC Class Codes: G01S 7/52047 for elimination of side lobes or of grating lobes; for increasing resolving power

Abstract

The ultrasonic imaging method and apparatus comprises an ultrasonic wave transducer supplied with recurrent multifrequency energy pulses for pulse insonification of an object under investigation with ultrasonic waves. Resultant echo waves from the object are directed onto the transducer for converting the same to electrical signals which are supplied to a signal processor which includes a variable bandpass filter. One or more of the filter characteristics are varied as a function of depth from which the echo signals are returned for enhanced resolution and signal-to-noise ratio of the received signal. Preferably, the filter is matched to the noise and signal spectra of the system. For A scan and B scan operations wherein reverberated acoustic pulses are derived from a range of depths a time variable filter is employed for time varying operation thereof.

Claims

1. In an ultrasonic system for the examination of the interior of objects, such as body parts, the combination comprising,

means for insonification of an object under examination with a broadband ultrasonic wave signal,

means for receiving echo signals from discontinuities over a range of depths within the insonified object and for converting the same to electrical signals,

means for filtering said electrical signals by bandpass filter means having a filter transmission factor as a function of frequency which is variable, and

means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter means in accordance with the depth of the discontinuity from which the echo signal

2. In an ultrasonic system as defined in claim 1 wherein,

said means for insonification of an object under examination comprises means for recurrent pulse insonification of the object, and

said means for compensating for depth dependent changes in the spectral distribution of the echo signals is recurrently operated for recurrently time varying the filter transmission factor versus frequency characteristic of the bandpass filter means in accordance with the time

3. In an ultrasonic system as defined in claim 1 wherein the passband of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo signals.

4. In an ultrasonic system as defined in claim 1 wherein the center frequency of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo

5. In an ultrasonic system as defined in claim 4 wherein the passband of the bandpass filter means is simultaneously time varied with the center

6. In an ultrasonic system as defined in claim 1 wherein the high frequency cutoff frequency of the bandpass filter means is time varied by said means for compensating for depth dependent changes in the spectral distribution of the echo signals by time varying the filter transmission factor versus frequency characteristic of the bandpass filter while receiving the echo

7. In an ultrasonic system as defined in claim 1 including envelope detecting means for envelope detection of the filtered electrical signals,

8. In an ultrasonic system as defined in claim 7 wherein said display means includes a cathode ray tube for B-scan display of the detected signals, said means for insonification of an object under examination includes means for recurrent pulse insonification of the object, and wherein

the filter transmission factor versus frequency characteristic of the bandpass filter is time varied and the cathode ray tube beam is deflected in one direction in accordance with the time elapsed from the preceding pulse operation of the insonification means, and including

means for relatively sweeping ultrasonic waves produced by the insonification means and the insonified object in a scanning motion, and

means for deflecting the cathode ray tube beam in an orthogonal direction in synchronization with said scanning motion of the ultrasonic waves

9. In a method for the non-invasive examination of objects such as body parts, the steps of

insonifying at least a portion of the body part with a beam of broadband acoustic energy to produce echo signals from within the body,

receiving echo signals from within the body and converting the same to electrical signals,

passing the electrical signals through bandpass filter means having a variable filter transmission factor versus frequency characteristic, and

time varying the filter transmission factor versus frequency characteristic of the bandpass filter in relationship with the depth from which the echo signals are received while receiving echo signals from over a range of depths within the body for compensating for depth dependent changes in the

10. In a method for the non-invasive examination of objects as defined in claim 9 wherein the filter transmission factor versus frequency characteristic of the bandpass filter which is time varied comprises the filter passband which is reduced as the depth from which the echo signals

11. In a method for the non-invasive examination of objects as defined in claim 9 wherein the filter transmission factor versus frequency characteristic of the bandpass filter which is time varied comprises the filter center frequency which is reduced as the depth from which the echo

12. In a method for the non-invasive examination of objects as defined in claim 11 wherein the passband of the bandpass filter simultaneously is

13. In a method for the non-invasive examination of objects as defined in claim 9 wherein the insonifying step includes recurrently insonifying with broadband acoustic energy pulses, and the receiving step recurrently is

14. In a method for the non-invasive examination of objects as defined in claim 9 wherein the step of time varying the filter transmission factor versus frequency characteristic of the bandpass filter means comprises reducing the high frequency cutoff frequency of the filter means as the

15. In an ultrasonic system for the examination of the interior body parts, or the like, the combination comprising,

means for recurrent pulse insonification of a body part under examination,

means for receiving echo signals from discontinuities within said body part over a time period following pulse insonification, which signals have a spectral distribution dependent upon the depth within the body part from which the signal is received, and for converting received echo signals to electrical signals,

bandpass filter means having variable operating characteristics through which said electrical signals are passed, and

means for time varying operating characteristics of the bandpass filter means while passing said electrical signals therethrough for relating filter operating characteristics with the time varying spectral

16. In a method for the non-invasive examination of the interior of objects such as living organisms, or the like, the steps of,

pulse insonifying at least a portion of an object to be examined with an acoustic energy beam to produce echo signals from discontinuities within the object,

receiving over a time period following said pulse insonifying step echo signals from within the body, which echo signals have a spectral distribution dependent upon the depth from which the signal is received,

converting the received echo signals to electrical signals,

passing the electrical signals through bandpass filter means having a variable filter transmission factor versus frequency characteristic, and

time varying the filter transmission factor versus frequency characteristic of said bandpass filter means while the electrical signals are passed therethrough to match the variable filter transmission factor versus frequency characteristic of said bandpass filter means with the time varying spectral distribution of the electrical signal for improving the

17. In a pulse operated ultrasonic imaging apparatus of the type which includes ultrasonic wave transducer means for transmitting ultrasonic wave pulses into an object to be examined and for converting reflected ultrasonic waves received over a range of depths therewithin into an electrical signal, the spectral distribution of said reflected ultrasonic waves being dependent upon the depth from which they are received,

a receiver for processing said electrical signal, said receiver including time variable filter means, and

means for time varying said time variable filter means while processing said electrical signal produced by ultrasonic waves received from over a range of depths to compensate for changes in the spectral distribution of

18. In an ultrasonic imaging apparatus of the type defined in claim 17 wherein said transducer means produces ultrasonic wave beams with said pulse operation thereof,

means for scanning said ultrasonic wave beam within said object,

visual display means responsive to the output from the receiver for displaying a B-scan image of a section of the object, and

means for generating timing pulses representative of the scanning position of the beam for timing operation of the transmitter, the time variable filter means, and the visual display means.