EVALUATION OF ASTEROIDAL TRANSDUCERS

被引：3

作者：

BALCERKUBICZEK, EK

HARRISON, GH

机构：

[1] Univ of Maryland, Baltimore, MD, USA

来源：

IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL | 1988年 / 35卷 / 05期

关键词：

We have previously described an approach to producing shaped ultrasonic fields [ l]-[5] using transducers with star-shaped (asteroidal) electrodes driven at a single continuous-wave (cw) frequency. There are many applications for such fields; but results shown to date concern broad; unfocussed intensity distributions; since bioeffects experimentation has been emphasized. In all these previous papers except [5; intensity distributions were calculated by assuming that the asteroidal source geometry could be replaced with a circularly symmetric source with a corresponding radial distribution function V(r). This approximation seemed reasonable for originally investigated asteroidal patterns shaded only on the periphery of the transducer. However; other highly shaded asteroidal sources require more exact modelling since they produce marked asymmetries in radiated transverse intensity profiles. Examples of highly-shaded transducers are the Gaussian source of von Hasel-berg and Krautkramer [6] and transducers emulating several oscillations of inverse source solutions for various desired field profiles ~~41. Our previous papers have already discussed some featureso f the relationship between V( r ) and corresponding asteroidal patterns; but only in [5] has the exact calculation of the azimuthally varying radiation from an asteroidal transducer been shown in passing. Briefly; for such calculations an asteroidal transducer is represented by the two-dimensional source V( r; p) of transducer radius r and azimuthal angle p; such that V(r; p) = 1 on the electroded portion of the transducer and V(r; p) = 0 outside the electrode boundary (Fig. l(a)). The source function V(r; p)is then used to calculate the ultrasonic pressure at an observation point (x; y; 1) due to a uniformly excited asteroidal source and the time-average intensity due to the pressure amplitude 11; (l); 3; (l)]. The re- lationship between the cylindrical coordinate system of the transducer and the Cartesian coordinate system for intensity plots is shown in Fig. l(b). Our previous method for numerical evaluation of the field pressure in the form of the superposition integral [l; (2); 13; (2)] was suitably modified to accommodate the dependence on the azimuthal angle in the source term as wealls to permit Manuscript recelvcd November 11; 1986. This work supported by the National Science Foundation under grant ECS-8121366. The authors are with the Unjvcrsity of Maryland School of Medicine; Department of Radiation Oncology. 655 W. Baltimore St; 6-015 Bressler Rescarch Building; Baltimore; MD 21201. IEEE Log Number 8719382;

D O I：

10.1109/58.8043

中图分类号：

O42 [声学];

学科分类号：

070206 ; 082403 ;

摘要：

引用

页码：641 / 643

页数：3

共 9 条

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[2] ULTRASONIC TRANSDUCER WITH A TWO-DIMENSIONAL GAUSSIAN FIELD PROFILE
CLAUS, RO
ZERWEKH, PS
[J]. IEEE TRANSACTIONS ON SONICS AND ULTRASONICS, 1983, 30 (01): : 36 - 39
[3] SINGLE-TRANSDUCER ELECTRODE DESIGN FOR BEAM SHAPING IN BIOMEDICAL ULTRASOUND
HARRISON, GH
BALCERKUBICZEK, EK
[J]. IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, 1986, 33 (03) : 265 - 272
[4] HARRISON GH, 1984, ACOUSTICAL IMAGING, V13, P329
[5] HARRISON GH, 1985, P IEEE ULTRASON S, P630
[6] HARRISON GH, 1987, P IEEE SU ULTRASON S, P655
[7] HARRISON GH, 1986, P ULTRASON INT 85, P164
[8] ODONNELL M, 1982, IEEE T SONICS ULTRAS, V29, P321
[9] VONHASELBERG K, 1959, ACUSTICA, V9, P359

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