Anthropomorphic cardiac ultrasound phantom

United States Patent m

Smith et al.

[li] Patent Number: 4,974,461 [45] Date of Patent: Dec. 4,1990

[54] ANTHROPOMORPHIC CARDIAC ULTRASOUND PHANTOM

[75] Inventors: Stephen W. Smith, Rockville; Jean E.

Rinaldi, Silver Spring, both of Md.

[73] Assignee: The United States of America as

represented by Department of Health
and Human Services, Washington,
D.C.

[21] Appl. No.: 432,433
[22] Filed: Nov. 6, 1989

Related U.S. Application Data

[62] Division of Ser. No. 257,174, Oct. 13, 1988, Pat. No. 4,894,013.

[51] Int. CI.' G01M 19/00; G09B 23/28

[52] U.S. CI 73/865.6; 73/1 DV;

434/268

[58] Field of Search 73/866.4, 865.6, 865.9,

73/1 R, 1 DV, 3; 434/262, 267, 268, 272; 364/510; 600/16, 17; 128/653 R, 660.01, 661.08, 661.09, 661.1, 662.01

[56] References Cited

U.S. PATENT DOCUMENTS

3,208,448 9/1965 Woodward 600/17

3,597,766 10/1971 Buck 600/16 X

4,277,367 7/1981 Madsen et al 73/60 U X

FOREIGN PATENT DOCUMENTS

685294 9/1979 U.S.S.R 73/866.4

OTHER PUBLICATIONS

H. Reul, "Cardiovascular Simulation Models", Life
Support System 2, 77-98 (1984).
Hoeks et al, "Methods to Evaluate the Sample Volume
of Pulsed Doppler Systems Ultrasound in Medicine and
Biology", (1984), pp. 427^34; vol. 10, No. 4.
Van Citters et al, "Artificial Heart and Assist Devices:
Directions, Needs, C Societal and Ethical Issues, Arti-
ficial Organs", 9(4), 375-415 (1985).

Altieri et al, "Implanatable Ventricular Assist Systems", Artificial Organs, 237-246 (1987). Boote et al, "Performance Tests of Doppler Ultrasound Equipment with a Tissue and Blood Mimicking Phantom", Journal of Ultrasound Medicine, 7,137-147 (1988). Madsen et al, "Ultrasonically Tissue-Mimicking Liver Including the Frequency Dependence of Backscatter", Med Phys. 9(5), 703-710 (1982) (part of p. 704 missing). McKicken, "A Versatile Test-Object for the Calibration of Ultrasonic Doppler Flow Instruments", Ultrasound in Medicine and Biology, 12:245 (1986). Walker et al, "Evaulating Doppler Devices Using a String Target", Journal of Clinical Ultrasound 10:25 (1982).

Newhouse et al, "A Proposed Standard Target for Ultrasound Doppler Gain Calibration", Ultrasound in Medicine and Biology, 8:313-316 (1982).

Primary Examiner—Tom Noland

Attorney, Agent, or Firm—Lowe, Price, LeBlanc,

Becker & Shur

[57] ABSTRACT

Apparatus and method are disclosed for producing ultrasound readings of simulated blood flow through a model left ventricle or larger portion of the human heart, held inside a fluid filled chamber with membranecovered windows, and through mitral and aortic valves cooperating therewith to provide a simulated human circulation flow free of reverberation artifacts and the like. Adjustable flow of a selected hydraulic fluid into and out of the chamber that also contains a plurality of ultrasound absorbing elements disposed oppositely to the ultrasound viewing windows is utilized to produce ultrasound signals picked up by an ultrasound transducer for processing in any known manner. A range of flow rate and systolic characteristics of a heart are readily simulated, to provide outputs substantially free of reverberations and ultrasound reflections from the inside walls of the chamber as well as the ultrasound absorbing elements.

6 Claims, 2 Drawing Sheets

ANTHROPOMORPHIC CARDIAC ULTRASOUND
PHANTOM

This application is a division of application Ser. No. 5 07/257,174 filed Oct. 13, 1988 and now U.S. Pat. No. 4,894,013.

FIELD OF THE INVENTION

The present invention relates generally to ultrasound 10 imaging and Doppler ultrasound devices, including continuous wave Doppler, pulsed Doppler, duplex Doppler/imaging systems and color-flow Doppler and methods for using them in cardiology, radiology, vascular surgery, obstetrics, neurology and other such appli- 15 cations. More particularly, this invention relates to test objects or phantoms for assessing the performance of ultrasound imaging and Doppler instruments in routine quality assurance measurements, acceptance testing of new devices and in training programs for clinical users 20 of the equipment.

BACKGROUND OF THE PRIOR ART

Several Doppler phantoms have been described in the prior art. These fall into two main categories. 25

In the first group are phantoms which include a moving target such as a ball bearing or suspended string. The moving target is used to map the location and size of the sensitive Doppler sample volume of the ultrasound device. In this category, for example, Walker et 30 al, "Evaluating Doppler Devices Using a String Target", Journal of Clinical Ultrasound, 10:25, 1982, describe a method in which a pair of moving strings at two different depths is used in a test target to measure Doppler sample volume size, sample location, and amplitude 35 sensitivity to Doppler shift. An alternative method, described by Hoeks et al, "Methods to Evaluate the Sample Volume of Pulsed Doppler Systems", Ultrasound in Medicine and Biology, 10:427, 1984, is to couple a small target such as a sphere to a vibrating loud- 40 speaker and then map the Doppler sample volume using this moving target.

In the second category of Doppler phantoms, the objective is to simulate blood flow, using a bloodmimicking liquid, through a simulated blood vessel in a 45 tissue-mimicking material. Phantoms of this kind typically consist more or less of a solid block of tissuemimicking material, such as gelatin or polymer, which contain tubes of varying diameters and bifurcations. Such phantoms seek to simulate blood flow through 50 abdominal and peripheral vessels. Examples of such devices, of varying degrees of sophistication, are taught by Newhouse et al, "A Proposed Standard Target for Ultrasound Doppler Gain Calibration", Ultrasound in Medicine and Biology, 8, 313—1982; McDicken, "A 55 Versatile Test-Object for the Calibration of Ultrasonic Doppler Flow Instruments", Ultrasound in Medicine and Biology, 12:245, 1986; and Boote et al, "Performance Tests of Doppler Ultrasound Equipment with a Tissue and Blood Mimicking Phantom", Journal of 60 Ultrasound Medicine, 7, 137-147, 1988. phantoms allow independent measurement of "blood" flow and enable calibration of the fluid velocity estimations of Doppler ultrasound. Commercial versions of these test objects, "Tissue Mimicking Ultrasound Phantom " Model 409, 65 Radiation Measurements, Inc., Middleton, Wis. 53362 (U.S. Pat. No. 4,277,367); "Ultrasound Doppler Phantom", ATS Laboratories, Inc., Bridgeport, Conn.

06608; and "Ultrasound Doppler Phantom", Interspec, Inc., Lewiston, Pa. 17044, are also available.

The most extensive application of medical Doppler ultrasound, however, is in cardiac diagnosis. Doppler ultrasound is used to measure blood flow through cardiac valves and thus to estimate pressure drops across individual heart valves for detection of valve dysfunctions. In addition, cardiac Doppler ultrasound is used to detect anatomical anomalies such as ventricular septal defects. The field of cardiac ultrasound imaging and Doppler ultrasound has a known and long-standing need for an anthropomorphic cardiac Doppler phantom to assess the performance of Doppler ultrasound under more realistic clinical conditions. Limited attempts to develop a Doppler phantom for cardiac applications include a modified cardiac pulse duplicator, "Cardiac Pulse Duplicator", Model MP1, Dynatek Laboratories, Annandale, N.J. 08801 as described by Cary et al in a private communication. However, this device is fabricated from rigid plastic, which generates strong acoustic reverberations unsuitable for diagnostic ultrasound examinations. In addition, such a modified pulse duplicator shows no similarity to the contracting muscular heart of human anatomy. Other examples include a modified cardiac pulse duplicator, "Valve Visualization Pulse Duplicator", Model MV/T1 Dynatek Laboratories, Annandale, N.J. 08801, as described by Gels et al, "In Vitro Ultrasound Flow Imaging Through Prosthetic Heart Valves", Medical Instrumentation, 21(2), 66-74, 1987, that includes a soft rubber vessel to simulate the aorta downstream of the aortic valve. This system, using microbubbles in tap water as an ultrasound contrast agent, enables flow visualization with diagnostic ultrasound imaging equipment to evaluate, qualitatively, the performance of prosthetic heart valves in vitro but does not permit simulation of the contracting heart of human anatomy.

In addition, Reul, "Cardiovascular Simulation Models", Life Support Systems, 2, 77-98, 1984, has developed hydraulically driven cardiovascular simulation models for the evaluation of prosthetic heart valves, using pressure transducers, flow transducers, and optical video filming of suspended particles in an aqueous-glycerol solution, but the cardiac models themselves are housed in rigid polymethylmethacrylate boxes. There are no viewing ports in the containers for ultrasound imaging or ultrasound Doppler studies. The polymethylmethacrylate containers produce high attenuation and reverberations that are unsuitable for ultrasound imaging or ultrasound Doppler studies. The hydraulic drive unit is mounted below the left ventricle in this device and precludes an apical ultrasound view, one of the most common views in clinical cardiac diagnosis. The hydraulic medium surrounding the left ventricle also is not specified. However, the attenuation scattering and velocity values of this medium are critical to the development of an ultrasound phantom as will be described below. Ordinary or distilled water, for example, is not suitable.

The field of cardiac assist devices, furthermore, includes left ventricular assist devices (LVAD) that typically have pneumatic pumps composed of a rigid plastic shell surrounding the flexible polymer left ventricle, Van Citters et al, "Artificial Heart and Assist Devices: Directions, Needs, Costs, Societal and Ethical Issues," Artificial Organs, 9(4), 375-415, 1985. The presence of air around the blood sac and the hard plastic shell make this technology unsuitable for a cardiac ultrasound