Comparison of spatially-selective and global ultrasonic blood flow measurements

ABSTRACTS, ULTRASONIC IMAGING AND TISSUE CHARACTERIZATION SYMPOSIUK

SESSIClN

3:

FLOOD

FLOW,

MOTIONAL

EFFECTS

AND

VELOCITY

IMAGING SYSTEM FOR DISPLAY OF CARDIAC Kl epper , Richard Ferraro, Donald L. Nasca , Institute of Applied Physiology and Medicine, Avenue, Seattle, WA 98122. A computer-based pulsed Doppler imaging system designed for the noninvasive assessment of coronary and cardiac dynamics has been constructed. A multigate pulsed Doppler of the moving target indicator type is implemented using CCD delay lines providing 295 range gates in depth. Doppler siector 5can images of flow, gated on the ECG, allow online direct imaging of flow in blood vessels within the body. Our display is gated on the electrocardiogram so that the heart cycle is divided into 16 time segments and displayed on a 128 i: 128 matrix. Information is recorded and displayed in real time along the direction of current interrogation along with previ ousl y-recorded i nf ormat i on along sector lines other during the same portion of the heart cycle. Flow towards the transducer is encoded in eight shades of red and flow away from the transducer is encoded in eight shades of blue. In addition, a real-time Doppler M-mode display at 210 lines per second provides a displaying method for Dopp 1 er flow information with better time resolution. A simultaneous echo image of surrounding tissues is also possible. Experimental trials on flow-through phantoms and human volunteers indicates the ability to directly image flow in vessels a5 small as 3 mm diameter I Operation at a 4 MHz carrier frequency and a PRF of flow to 10 cm. 6.8 kHz provides images of depths of It is anticipated device wi 11 be used to image flow in that the coronary bypass followed by time spectrum grafts, real analysis of a conventional single gate pulsed Doppler in order to quantify the velocity of flow in such vessels. AN ECG-GATED HEMODYNAMICS, Davis, and

COMPARISON FLOW

Institute Zurich,

DOPPLER

John Rosar i o 7@1 - 16th

R.

OF SPATIALLY-SELECTIVE MEASUREMENTS, U. Fiomedical of

AND Moser, Engineering,

A.

GLOBAL

Vieli ETH

ULTRASONIC BLOOD and M. Anliker, and University,

Switzerland.

spatially-selective and global of blood flow has been in..- _,.__.._ vitro .-..aid of a multigate ultrasonic device. array transducer was utilized to Doppler narrow as 1 mm and form dynamical 1 y-focused beams as rectangularly-profiled ones as wide as 30 mm. It verified that the width of the Dopp 1 er has been spectra obtained from small sample volumes primarily reflects the transit time effect whereas the spectra recorded in global sample vol umes are essential 1y determined by the velocity measurements distribution across the vessel. The ql obal produced wider spectra in the experiments carried consistently with an out for this study and were therefore assoc i at ed uncertainty of frequency estimate. In i net-eased the mean addition, they exhibit a signal-to-noise to 30 dB ratio up below that of the spatially-selective evaluation. On the transvascular velocity other hand, the irrelevance of the distribution point in favor of the global method. is a major Moreover, the applicability of spat i al 1y-se1 ect i ve procedures is restricted by the size of the samp 1e in small vessels vol ume I contrast, integral methods are limited by the Blj which a uniform beam intensity can be max i mum width over achieved with the annular array transducer utilized. The

procedures assessed

performance for

the

of quantification with the An annular

ABSTRACTS,

ULTRASONIC

IMAGING AND TISSUE

CHARACTERIZATION

SYMPOSIUM

per-f ormance, deep-lying large vessels for optimum spatially-selective methods appropriately assessed by rather be evaluated whereas small superficial vessels should with irregular velocity distributions, globally. To cope will have to sample however, spati al 1 y-selective procedures the entire vascular cross section. supported in the Swiss Nat ional This work was part by Thus,

are

Science

Foundation

under

grants

3.804-O.

82

and

4.890-085.18.

ULTRASONIC DLOOD SOUND Engineering,

PLETHYSMOGRAFHY : CHARACTERIZING DYNAMICS OF THE MICROCIRCULATORY SYSTEM BY REAL-TIME HIGH-PRECISION VELOCITY MEASUREMENTS, 0. Gavish, Biomedical The Hebrew University , Hadassah Medical School,

Jerusalem,

Israel. sophisticated system of small blood vessels having diameters ranging from 4 to 200 microns - the microcirculatory system mediates the blood/ t i ssue exchange of gases, metabolites, heat and fluids. Its dynamic state can be characterized the time the dependence of a! VlY!?, . by f luctuati on5 in the volume fraction of the tissue fluids. Its fastest components are the modulation of diameter that local determines the resistance to blood flow. These fluctuations in the tissue composition can be shown to be accompanied by linearly-related fluctuations in the sound velocity in tissue of magnitude lo-100 ppm. However, real time sound velocity measurements at sensitivity of 1 ppm are beyond the power of commercially-available diagnostic any device. The problem was overcome by using a miniature of an ultrasonic resonator ccl 1 Cl1 mounted on a skin fold of a patient . In the observed interference pattern, the f 1 uctuat i on5 of the reeonance frequencies are proportional to fluid volume the fluctuations at the tested tissue. Sampling rates of 50/s are "real time” for the actual cases. These f luctuati 00s were monitored by a novel device called the Ultrasonic Plethysmograph, which has been constructed and tested in a wide range of clinical situations. These appIications include monitoring effects of drugs and emotional stress in peripheral vascular disease and effects of drugs, anesthetics and controlled respiration during routine work in operating theaters and emergency rooms, in parallel with other invasive and noninvasive methods. The results were proved to be of great clinical significance. Cl1 F. Eggers and Th. Funck, 969 !?~,~.L%lL...2~~~~~ --* 44 A

(1973).

ANALYSIS OF SOFT TISSUE MOVEMENT IN CLINICAL OF MALIGNANT TUMORS, M. Tristam, D.C. Barbosa, J.C. Hill, D. 0. Cosgrove and C.R. Physics Department, Research, Royal Marsden Hospital, Sutton, Institute of Cancer Surrey, UK. Ul t rasound provides a means of noninvasive investigation of t i ssue dynamics, in particular, motion induced by cardiovascular activity. Analysis of tissue movement is aimed at quantitative assessment of low frequency elastic properties of t i ssues and changes in these properties occurring during progress and treatment of malignant disease. Data were obtained from scanning liver metastases in 12 cancer patients and normal liver parenchyma in 6 healthy volunteers, using a Sonoline-SL (Siemens) scanner. In each subject, M-mode displays were recorded, together with a corresponding portion of the ECG trace. ULTRASONIC ASSESSMENT Ramber ,

45