Ultrasound imaging system with improved scan conversion

• US 4,058,001 A
• Filed: 08/02/1976
• Issued: 11/15/1977
• Est. Priority Date: 08/02/1976
• Status: Expired due to Term

• Current Assignee: GD Searle LLC (Pfizer Inc.)
• Original Assignee: GD Searle LLC (Pfizer Inc.)
• Inventors: Waxman, Albert S.
• Primary Examiner(s): Queisser, Richard C.
• Assistant Examiner(s): Kreitman, Stephen A.
• Application Number:
  US05/710,942
• Time in Patent Office: 470 Days
• Field of Search: 73/67.8 S, 73/67.8 R, 73/67.7, 73/67.5 R, 73/71.5 US, 128/2 V, 128/2.05 Z, 358/112
• US Class Current: 600/443
• CPC Class Codes: A61B 8/00 Diagnosis using ultrasonic, sonic or infrasonic waves imaging of objects using sonar G01S15/00
• CPC Class Codes: A61B 8/4218 characterised by articulated arms
• 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 29/4454 Signal recognition, e.g. specific values or portions, signal events, signatures
• CPC Class Codes: G01S 15/8906 Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
• CPC Class Codes: G01S 7/52028 using digital techniques

Abstract

In an improved system for medical imaging employing a transducer for transmitting and detecting ultrasonic vibrations, a digital scan converter accepts echo signals detected by the transducer and transducer position signals identifying the point of origin of the signals in a scanning plane transversely oriented relative to the body of the patient under study. The amplitudes of the echoes detected are stored at memory locations associated with the points of origin of the echoes. Peak detection analysis is performed on large echoes emanating from higher impedance tissue interfaces within the scanning plane, while cumulation and normalization analysis is performed on small echoes emanating from low impedance tissue interfaces within the scanning plane. Sensitivity to otherwise unobtainable image details, signal to noise ratio, and freedom from distortions is maximized, yet the improved system may be used

Claims

1. In an ultrasonic instrument for use in medical diagnosis having a transducer for transmitting vibrations at ultrasonic frequencies into the body of a patient and for detecting echoes produced at tissue interfaces within said patient by said vibrations and for generating responsive electrical echo signals, and a display unit for producing a two-dimensional visual representation of said tissue interfaces in a scanning plane, the improvement comprising a digital scan converter for receiving inputs from said transducer and having location determination means for assigning two-dimensional coordinates in said scanning plane, and having addressable memory storage locations in communication with said transducer for storing representations of the amplitudes of said echo signals at corresponding memory storage locations having the addresses of the aforesaid two-dimensional coordinates, circuit means for communicating said stored representations to said display unit, and echo signal accumulation and normalization means accepting incoming echo signals having an amplitude less than a prerequisite amplitude, for comparing to said prerequisite the previously stored contents of said memory storage locations at the address corresponding to each said incoming signal, and, if said stored contents is less than said prerequisite, accumulating said incoming signal with said contents, normalizing the value thereby obtained by the number of occurrences of said accumulation and transmitting to said storage locations in normalized value thereby obtained for registration at said corresponding address.

2. In a system for medical imaging employing a probe for transmitting ultrasonic vibrations to a patient and for receiving responsive echoes indicative of tissue interfaces and for producing corresponding representative echo signals, probe position sensing means and a display unit for producing two-dimensional visual representations of said tissue interfaces in an imaging plane, the improvement comprising a multiplicity of addressable electronic memory storage locations in communication with said display unit, an address generator for receiving inputs from said probe position sensing means and for generating a location address in memory storage for each location in a scanning plane which is defined by the ultrasonic vibration transmission scanning, discriminator means for separating the echo signals from said ultrasonic probe which achieve a prerequisite amplitude from those echo signals which fail to achieve said prerequisite amplitude, comparator means connected to said discriminator means, to said address generator and to said memory storage locations for contemporaneously receiving from said discriminator means the echo signals which achieve said prerequisite amplitude as well as the location address corresponding to the location from which each such echo signal is received, and for transmitting to storage at the same memory storage location the greater of the aforesaid echo signal and the previously stored contents of said memory storage at the same address location, and circuit means connecting said discriminator means to memory storage, and responding to echo amplitude signals which fail to achieve said prerequisite amplitude for enhancing with such signals the existing stored contents of said memory storage locations at addresses corresponding to the respective locations from which such signal emanate, and then only at memory storage locations in which the previously stored contents fail to exceed said prerequisite amplitude.

3. The system of claim 2 wherein said means for enhancing the existing stored memory contents comprises an adder-normalizer circuit which accumulates the value of said echo amplitude signals failing to achieve said prerequisite amplitude, and normalizing said accumulated value by the number of occurrences of such echo amplitude signals thereby accumulated, and wherein the normalized value thereby obtained is stored in the appropriate memory storage location.

4. The system of claim 2 wherein analog to digital signal conversion means are employed to perform signal conversion of said echo signals prior to transmission to said discriminator means, and to perform signal conversion of inputs to said address generator from said probe position sensing means.

5. In an instrument for medical diagnosis having a transducer for transmitting vibrations at ultrasonic frequencies into the body of a patient and for detecting echoes produced by said vibrations at tissue interfaces within said patient and for generating responsive electrical echo signals, a position sensor for providing electrical indications of the position and orientation of said transducer, and a display unit for producing a two-dimensional visual representation of said tissue interfaces in a scanning plane, the improvement comprising a digital scan converter for receiving inputs from said position sensor and transducer and having a location determination means for assigning two-dimensional coordinates to locations in said scanning plane, means for accumulating the echo signals emanating from each two-dimensional coordinate location for which none of the echo signals achieves a predetermined amplitude, normalizing the signals thereby accumulated over the number of occurrences of such signals, and registering the normalized value thereby obtained, and means for registering only the largest echo signal emanating from those coordinate locations where at least one echo signal emanating therefrom achieves the aforesaid predetermined amplitude, with said scan converter transmitting to said display unit the signal values thereby registered to form said visual representation of said tissue interface.

6. An ultrasonic instrument for medical diagnostic imaging comprising an transducer for positioning in communication with a patient for transmitting penetrating ultrasonic vibrations to the patient'"'"'s body and for detecting resultant echoes indicative of the location and nature of tissue interfaces in a scanning plane through the patient'"'"'s body as defined by the position and orientation of said transducer when the associated echo is detected, and for producing characteristic echo signals, a digital scan converter including a multiplicity of addressable memory storage locations in communication with said display unit, transducer position sensing means, an address generator for receiving said echo signals and inputs from said transducer position sensing means to generate a digital location address in memory storage corresponding to the two-dimensional coordinates of a location in said scanning plane, means for producing digital representations of the amplitudes of echo signals received from said transducer, discriminator means for separating those echo signals received by said transducer which achieve a prerequisite amplitude from those echo signals which fail to achieve said prerequisite amplitude, a first comparator means connected to said discriminator means, to said address generator and to said memory storage for contemporaneously receiving an echo signal which achieves said prerequisite amplitude as well as the previously stored contents of the memory storage location corresponding to the coordinate location from which the associated echo emanates, and for transmitting to the same memory storage location the greater of the aforesaid echo signal and said previously stored contents, a second comparator means in communication with said address generator and memory storage for determining whether or not the previously stored contents of memory storage at the address location determined by said address generator achieves the aforesaid prerequisite amplitude and for generating an integration signal when the aforesaid previously stored contents fails to achieve said prerequisite amplitude, adder-normalizer means connected to said discriminator means, said memory storage, and said second comparator means and actuated by said integration signal to add echo signals to the previously stored contents of said memory storage at the associated memory storage address and average the sum thereby obtained over the number of occurrences of said added echo signals, and a display means connected to said memory storage for contemporaneously displaying visual representations of the contents of all of the memory storage locations.

7. In an instrument for medical diagnosis having a transducer for transmitting ultrasonic impulses into the body of the patient and for detecting echo information from tissue interfaces resulting from said impulses and generating in response thereto echo information signals, display means for producing a visual representation of said tissue interfaces in the plane of scanning movement of the transducer, the improvement which comprises a digital scan converter receiving the echo information signals and rendering the echo information signals compatible with the display means, said scan converter including both peak echo signal detection means and echo signal accumulation normalization means, with large echo signals having amplitudes above a prerequisite amplitude being processed by said peak detection means, and small echo signals below said prerequisite amplitude being processed by said accumulation-normalization means, whereby peak analysis is performed on larger signals while preserving image information carried upon small pulses and to improve the sensitivity of said instrument in distinguishing image information from noise.

8. An instrument as in claim 7, in which said scan converter further includes memory storage means having memory storage locations for storing echo signals at storage locations corresponding to coordinates in said scanning plane;

and in which said peak detection means cooperate with said memory means to compare with the previously stored contents at a location any new large echo signal for that location, and registering within said memory means the greater of the two;

and in which said accumulation-normalization means cooperates with said memory means to compare to the prerequisite amplitude the previously stored contents at the location of a new small echo signal, and if said stored contents are less than said prerequisite amplitude, registering in said memory means the value of the sum of the new small signal with the previously stored contents, normalized by the number of small signals which have been detected for said location.

9. An instrument as in claim 7, in which said transducer is scanned through an angle at a rate providing echo information in real time, with said angle defining said scanning plane and in which said digital scan converter includes means for calculating the location of said echo information by utilizing the angular orientation of said transducer.

10. A method of detecting the location of tissue interfaces in the body of a living subject using an ultrasonic imaging system employing a probe, probe position sensing means, and a display unit wherein image signals are registered at a multiplicity of spaced locations comprising:

directing vibrations at ultrasonic frequencies from said probe into the body of the subject, detecting the occurrence and timing of the resulting echoes, associating specific two-dimensional coordinate positions in a plane transverse to the body of the subject with specific ones of said spaced locations in said display unit as determined by the positions of said probe ascertained from said probe position sensing means and as determined by the distances of the origin of the echoes from said probe as ascertained from said echo timing, registering as echo signals at each of the associated spaced locations on said display unit only the largest single echo at each one of the aforesaid multiplicity of spaced locations associated with a specific two-dimensional coordinate position at which any echo achieving a pre-selected prerequisite amplitude is detected, averaging the amplitudes of the echoes emanating from each two-dimensional coordinate position at which no echo achieves said prerequisite amplitude to obtain a normalized amplitude value, and registering said normalized amplitude value of echoes emanating from each two-dimensional coordinate position at which no echo achieves said prerequisite amplitude.

11. A method as in claim 10 which comprises the further step of adjusting said prerequisite amplitude to vary the distribution of echo signals above and below said prerequisite amplitude to obtain the optimum image on said display unit.

12. A method of detecting the location of tissue interfaces in the body of a living subject using an ultrasonic imaging system employing a probe, probe position sensing means, and a display unit wherein image signals are registered at a multiplicity of spaced locations comprising:

directing vibrations at ultrasonic frequencies from said probe into the body of the subject, detecting the occurrence and timing of the resulting echoes, associating specific two-dimensional coordinate positions in a plane transverse to the body of the subject with specific ones of said spaced locations in said display unit as determined by the positions of said probe ascertained from said probe position sensing means and as determined by the distances of the origin of the echoes from said probe as ascertained from said echo timing, registering as echo signals at each of the associated spaced locations on said display unit only the largest single echo at each one of the aforesaid multiplicity of spaced locations associated with a specific two-dimensional coordinate position at which any echo achieving a pre-selected prerequisite amplitude is detected, accumulating the sum of the amplitudes of the echoes emanating from each two-dimensional coordinate position at which no echo achieves said prerequisite amplitude, averaging by the number of occurrences of such echoes at said position, and registering the normalized value of the amplitudes of echoes emanating from each two-dimensional coordinate position at which no echo achieves said prerequisite amplitude.