Ultrasonic transducer assembly

Abstract

A series of ultrasonic multi-element transducer assemblies is disclosed for patient monitoring use and particularly fetal monitoring prior to and during delivery. Each assembly is comprised of a flexible material shaped, at least in part, in a cloverleaf type configuration wherein the cloverleaf arms are independently flexible relative to the center area and to each other for easy conformity to the body. Each of the arms carries at least one transmitting transducer and the cloverleaf center area is provided with a receiving transducer. Each of the transducers is provided with an appropriate lens arrangement for enabling overlapping direct beam illumination of a substantial portion of the interior of the body. The middle arm of the basic cloverleaf configuration is extended to include additional transmitting and receiving transducers for predetermined greater coverage, for example, a straight extension to the middle arm bearing an additional receiving and transmitting transducer in staggered arrangement or mated together under a single lens yielding greater longitudinal coverage of a fetus as it progresses down the birth canal during labor. Disclosed variations thereof employ a Y-shaped extension to the middle arm, wherein the branches of the Y extension are provided with singular transmitting transducers or combined transmitting and receiving transducers under a single lens, in possible combination with an additional receiving transducer located at the base of the Y extension. Such arrangements provide greater-side-to side coverage as well as extended longitudinal coverage of the lower portions of the abdomen with regard to moving target such as a fetus undergoing the birth process.

Parent Case Text

RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 206,012, filed Dec. 8, 1971 now U.S. Pat. No. 3,847,016.

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to transducer assemblies and more specifically to ultrasonic transducer assemblies for monitoring targets within the body of a patient.

In ultrasonic exploratory systems for biological investigations, several types of search units have been available. Most of these units are of a type which is manually held against the body; they are bulky in construction and do not readily accommodate for body curvature. In the patient monitoring field, parameters are dictated which indicate the desirability for quick and convenient placement of transducer devices that would serve to provide for accurate and reliable data, and simultaneously be of simple design and versatile in application. However, most transducers are critical in placement and are, therefore, less than ideal for monitoring where a large area of illumination is desirable.

One particular area in the field of ultrasonics, for which little exists or has been developed in the form of ultrasonic transducer devices, concerns monitoring the heart activity of the unborn fetus. In this particular field, it has been found difficult to track the fetal heart for extended periods of time without having to relocate the transducer, to accommodate the wide divergence of fetal heart positions and depths encountered in long term fetal heart monitoring, particularly during the birth process. In order to operate without transducer placement criticality, large area coverage is highly desirable.

Ideally, one would want the ultrasonic transducer assembly to provide continuous satisfactory coverage of the moving target, throughout, from the initial placement. The practitioner utilizing a transducer assembly providing only limited volume coverage would be faced, for example, with the undesirable prospect of having to move the transducer assembly several times in the course of a fetus' progress down the birth canal during labor and delivery. Valuable information may be lost with each new placement of the transducer assembly, particularly if supporting equipments need to be readjusted. Also, a new placement itself could all too easily prove to be unsatisfactory, thus necessitating further search for an acceptable location. In the interim, however, no reliable data is taken and the fetus during that time could be undergoing serious yet undetected stress.

SUMMARY OF THE INVENTION

A principal objective of the present invention is to provide an ultrasonic transducer assembly capable of assuring reliable long term patient monitoring, such as fetal heart monitoring over a wide range of fetal positions within the maternal abdomen prior to and during labor, while minimizing the need for repositioning the transducer assembly.

To attain this, the present invention contemplates an ultrasonic multiple element transducer assembly at least a portion of which is of cloverleaf type configuration, having at least one central portion which is provided with a receiving transducer and at least three peripheral transmitting transducers, each of the latter being associated with a separate arm extending out from the center body portion of the assembly where said at least one receiving transducer is located. Each of the arms is designed to be independently flexible relative to the other arms and to the center portion so as to provide easy conformity to the body. The distances between the centers of each of the transmitting transducers and to the center of said at least one receiving transducer, in conjunction with lenses individually provided on the transducers for proper beam spreading, are such as to provide a three-dimensional coverage of a relatively large portion of the interior of the body, such as, for example, a maternal abdomen anywhere from 5 cm below the abdomen surface inward.

According to the broader aspects of the invention there is provided an ultrasonic multiple element transducer assembly for use particularly in patient monitoring, comprising a substantially flattened base of homogeneous, flexible material composition, which includes a cloverleaf type configuration portion having a center area with at least three arms extending outwardly therefrom, the arrangement of each of said arms being such as to be independently flexible relative to each other and to the center area, with each arm having proximate said center area narrower width and thickness dimensions from the outer arm area and said center area, for enabling the assembly to conform to varying body curvatures, each of said arms being provided proximate the end thereof remote from said center portion with at least one active element in the form of a transmitting means, said transmitting means being arranged and including lens means for providing overlapping direct beam illumination of a predetermined volume of the interior of the patient's body intended to be monitored, and said center area being provided with at least one active element in the form of an ultrasonic receiving means, said ultrasonic receiving means including lens means arranged to provide illumination of a substantially greater percentage of the portion of the patient intended to be monitored than that provided by the said transmitting means associated with any of said arms of said cloverleaf portion, for enabling detection by said receiving means of ultrasonic energy from whichever of said transmitting means is illuminating the portion of the patient's body intended to be monitored at any time, wherein the middle arm of said cloverleaf configuration portion is extended to provide for additional active elements in the form of additional transmitting and receiving means for predetermined greater longitudinal and/or transverse coverage, with the base of said transducer assembly being constructed so as to virtually eliminate cross coupling of ultrasonic energy therethrough between active elements. For example, in certain embodiments a straight extension to the middle arm is provided bearing an additional receiving and transmitting transducer in staggered arrangement or mated together under a single lens. This type of transducer assembly is particularly effective, for instance, in yielding greater longitudinal coverage of a fetus as it progresses down the birth canal during labor.

Other disclosed arrangements incorporating the basic cloverleaf design employ a Y-shaped extension to the middle arm, wherein the branches of the Y extension are provided with singular transmitting transducers and associated lenses or combined transmitting and receiving transducers under a single lens. The base of the Y extension may also be provided with an additional receiving transducer. Such arrangements are particularly effective in providing greater transverse, i.e. greater side-to-side, coverage as well as extended longitudinal coverage of the lower portions of the abdomen with regard to a moving target such as a fetus undergoing the birth process.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other objects and features of this invention will become more apparent by reference to the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1A is a plan view of the basic cloverleaf transducer assembly illustrating the geometrical setting of the multiple transducer elements;

FIG. 1B is a diagrammatical representation of the basic configuration of FIG. 1A, illustrating in particular the arrangement of the conductive wires running from the stem of the assembly to the individual transducers;

FIGS. 2A-2C are sectional views of FIG. 1B taken respectively along the lines of A--A, B--B and C--C;

FIG. 3 is a schematic cross-sectional view of the basic cloverleaf type transducer assembly in operative application to a human subject;

FIGS. 4A and 5A are respective plan views of additional preferred embodiments of ultrasonic transducer assembly design according to the invention, in which the central arm of the basic cloverleaf assembly is extended to include additional transducers for extended longitudinal coverage;

FIGS. 4B and 5B illustrate typical patterns of the respective arrangements depicted in FIGS. 4A and 5A in relation to the actual size of the assemblies;

FIGS. 6A and 7A are respective plan views of two further preferred ultrasonic transducer assembly embodiments according to the invention, in which the central arm of the basic assembly design is modified to include a substantially Y-shaped extension provided with additional transducers for increasing longitudinal and transverse coverage; and

FIGS. 6B and 7B illustrate typical coverage patterns of the respective arrangements depicted in FIGS. 6A and 7A relative to the actual size thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the figures, there is shown in FIG. 1A a preferred basic design coupling a four-element transducer assembly shaped like a cloverleaf, having a body 11, a receiving transducer or crystal 12 and receiving lens 13, and transmitting transducers or crystals 14, 15 and 16 with transmitting lenses 17, 18 and 19 respectively. A cable 21 preferably coaxial, supplies power to the respective transmitting crystals and is used for routing the returned signals received by receiving crystal 12 to suitable electrical monitoring instrumentation. The conductor leads are particularly shown in FIGS. 1B, 2B and 2C. The transmitting crystals 14-16 are electrically intercoupled as illustrated by conducting wire 21a which extends about the periphery of the assembly. Conducting wire 21b, on the other hand, leads to the central receiving crystal 12. The illustrated pattern and fine gage (e.g. 50 Mils) of the conducting wires are such as to enable a high degree of flexibility being achieved in the transducer assembly.

The general or basic configuration, as mentioned, is of cloverleaf design, having the body 11 fabricated of flexible material such as, for example, a polyurethane or other suitable composition which also has high damping characteristics to minimize ultrasonic energy cross-coupling characteristics between crystals. The three arms extending from the center portion are provided with the transmitting crystals 14, 15 and 16 at their extremities. Each of the arms is wider at its outer or free end where the crystal is mounted, as opposed to the neck portion 22 thereof intermediate the center of the assembly and the outer end. In the present embodiment the preferred difference in these width dimensions is approximately 20 percent, allowing greater flexibility of each of the arm units. The ability to independently flex the respective arms containing the transmitting crystals is further enhanced by thinning out (i.e. reducing the thickness of) the neck portions 22 of the arms. This is particularly illustrated in FIG. 2A. In this embodiment the preferred ratio of the neck 22 thickness to the extremity thickness at 23 is approximately a ratio of one to two. This overall construction results in optimum flexibility of each of the arm units. It allows each arm to more readily conform to the body curvature and at the same time introduces almost no compression upon body 11. This in turn avoids interfering stress on the other transmitting crystals and the receiver crystal. The total configuration of each arm of the flexible assembly is such that the flexibility is increased by roughly the cube of the thickness.

Proximate the free end of each arm a cavity 20 (FIG. 2A) is provided for housing the transmitting assembly, for example, crystal 16 and its lens 19, and simultaneously allowing ample room around the lens element for an ultrasonic coupling gel to stay in place, once deposited therein, and thus enhancing the capability for long term monitoring. It should be noted that the depth of the cavities and the thickness of the gel are not critical. Almost any fluid or gel would be operative, for example, water, cream, oil, whether it be high or low viscosity, conductive or nonconductive. A similar recess or cavity is provided with regard to receiving crystal 12 and its lens 13.

It should be noted that the various dimensions between the transmitting and receiving elements are likely to be critical to each of the other dimensions. These dimensions have been developed based on the consideration of utilizing the present transducer assembly for fetal monitoring where an average curvature of the body is about 20 cm. The distance between the centers of adjacent transmitter crystals is approximately 8 cm and the distance center-to-center from each transmitter crystal to the receiver crystal is about 41/2 cm.

With regard to the crystal characteristics and make-up, the crystals are preferably composed of lead-zirconate-titanate, which material is especially efficient for converting electrical signals to mechanical motion. For the receiving crystal the material used could be quartz, lead-metaniobate or equivalent which has a high efficiency in converting mechanical motion to electrical signals.

Each of the transmitter crystals in a preferred arrangement is cut in the shape illustrated in the dashed lines in FIG. 1A, so that the ultrasonic energy is radiated in selected directions only. For example, with reference to FIG. 3, at the cut-off edge 24 of transmitter lens 18, the ultrasound beam spread radiated from associated crystal 15 is hardly diverted as the cutoff edge is near the center of the lens. Of course, the operative surface of each of the transmitting crystals with its associated lens could also be circular in shape, as shown via the dashed lines in FIG. 1A and also shown in FIGS. 1B and 2A.

In the illustrated general embodiment of FIGS. 1-3, the angle .alpha. (FIG. 1A) formed by the center arm and one of the side arms is preferably 120.degree.. Moreover, the angle .beta. formed on the one hand by a line drawn between the centers of the receive crystal 12 and a transmit crystal, e.g. 14, and on the other hand by a line drawn through the center of that transmit crystal and the center of an adjacent transmit crystal, e.g. 16, is preferably 30.degree..

Moreover, the transmitter crystals are preferably approximately 1.9 cm in diameter whereby the cutoff section would amount to a radial distance of 0.635 cm from the outer edge. This provides for an approximate area for each transmitting crystal of 2 cm.sup.2. The receiving crystal arm is preferably approximately 3.87 cm.sup.2, or roughly twice that of each of the transmitting crystals. The total area of the transmitting crystals, on the other hand, exceeds the area of the receiving crystal by a ratio of at least 11/2 to 1. The receiving crystal is made considerably larger than the transmitting crystals as it must detect the ultrasonic energy from a considerably larger area then any one of the transmitting crystals illuminated areas.

The lenses 17, 18, 19 for the transmitter crystals and lens 13 for the receiver crystal have approximately the same radius of curvature. However, it may be particularly seen in FIG. 3 that the beam spread provided by the receiving crystal assembly is greater due to the different size of crystal used. In the present embodiment, the transmitter means have approximately an 8.degree. beam spread while the receiver means has approximately 11.degree. of beam spread, or a total beam spread of 16.degree. and 22.degree. respectively.

In FIG. 3, the three transmitter units are shown to be mounted in the transducer assembly in such a manner that the radiating beams overlap each other to uniformly illuminate a large area. The radiated patterns emitted by crystals 15 and 16 actually overlap to a greater extent than that shown as a result of the side lobes of ultrasonic energy off the crystal edges as well as the scattering effect within the body tissue. In the preferred embodiment of FIGS. 1-3, it was found that the transmitter crystals would illuminate roughly 8 cm.sup.2 at a depth of a 5 cm from the lens whereas the receiving crystal would illuminate roughly 16 cm.sup.2.

From FIG. 3 it may be seen that utilization of the multiple element transmitter assembly assures the shortest path of ultrasonic energy between the transmitter, target and receiver. For example, assuming that target 27 is at the point indicated, the transmitter-target-receiver path 26, 27 and 28 is shown to be approximately 13.25 cm whereas the transmitter-target-receiver path 29, 27 and 28 is shown to be 15.25 cm. Assuming use of the conventional single transmitter and receiver assembly where crystals 16 and 12 are positioned, then the path to be travelled would take an additional 2 cm. which would reduce the amplitude of the signal illuminating the target by approximately 4db, resulting in a lower amplitude signal at the receiver.

It should be understood, of course, that various combinations and permutations of crystal spacing and crystal sizes with lens curvatures might be employed without loss of useful signal. In the instant basic embodiment, for example, spacing between the adjacent transmitter crystal centers might be anywhere from 7 to 9 cm and the spacing between each transmitter crystal and receiver crystal might be anywhere between 4 to 5 cm. Should, however, the spacing between transmitters and receiver be increased considerably, then, due to the 20 cm average body curvature, the transmitters might not illuminate beyond the 11 cm depth, which might thus result in a shallow area illumination. Thus a high percentage of fetal targets which are often at the 14 cm and 16 cm depths, would be missed altogether. On the other hand, with very close spacing between the transmitters and receiver, the ultrasonic beam radiated would not overlap at 5 cm below the surface of the body and, therefore, a fetal target at this location would provide no monitoring signal.

It is to be also noted that due to the symmetry of the basic cloverleaf configuration and the lensing structures, the assembly may be used effectively in a reverse mode, i.e. the transmit crystals may be used in a receive mode and the receive crystal used as a transmitter.

While in the above there has been described the basic cloverleaf design as one preferred embodiment of the invention for an ultrasonic transducer assembly, other preferred embodiments are contemplated which, like the basic cloverleaf design, have achieved a high level of success in experimental and/or clinical testing. These embodiments essentially provide additional crystals in predetermined array to extend the overall illumination in specified manner such as for more specific applications, for example, with regard to a moving target over an extended period of use.

It should be noted that with any of the embodiments of ultrasonic transducer assembly described herein, the patient is electrically isolated, i.e. there is no electrical contact, and the patient is entirely safe.

The first of the preferred alternative embodiments will be described in reference to FIGS. 4A and 4B wherein a six-element transducer assembly is depicted. In the description of this and the remaining embodiments disclosed herein, similar reference designators to those used in describing the basic cloverleaf design (FIGS. 1-3) are employed for purposes of clarity.

As in the basic design, the assembly according to FIG. 4A has a body of flexible material 111, a receiving crystal and appropriate lens structure 112-113, and transmitting crystals 114-116 also with appropriate lens structures 117-119. A double coaxial type cable 121 supplies power to the respective transmitter crystals and couples the received signals to the instrumentation. In this embodiment, however, the middle or central arm 123 of the basic design portion described hereinbefore has been extended outward (extension 123a), as particularly illustrated in FIG. 4A by dashed line 123b, to provide an additional receive crystal 124 and a transmit crystal 125. These crystals are provided with appropriate lens structures 126 and 127 respectively.

The transmitting crystal 125 is cut in substantially the same shape as transmitting crystals 114 and 116 to effect radiation of ultrasonic energy therefrom, as hereinbefore described, in only the selected direction(s). Though not particularly shown, the thickness of the extended portion 123a of middle or central arm 123 as well as the width thereof is reduced in similar manner to that described for the arms of the basic design portion for providing greater flexibility and conformity to the body curvature. These dimensional reductions, as before, occur between the locations of the active elements, i.e. the transmit and receive crystals, including that portion of the assembly of FIG. 4A lying proximate dashed line 123b.

The basic design center-to-center spacing between the transmitting crystals 114-116 and the receiving crystal 113 has been preserved in the extended portion of middle arm 123, wherein new receive crystals 124 is spaced apart from transmit crystal 115 and new transmit crystal 125 is spaced apart from receive crystal 124, each by the dimension c. A preferred value for dimension c would be 41/2 cm. The cenger-to-center spacing d between transmitter crystals 114-116 in the basic design portion of the FIG. 4A embodiment also remains the same. A preferred value for this dimension is 8 cm.

The full routing of the very fine (typically 45 mil) wires intercoupling the various active elements shown in FIG. 4A retains the design goal of the basic cloverleaf structure to maximize flexibility of the assembly for conformity to the body curvature. This is true of all remaining embodiments described herein. In this particular instance the wire routing of the standard cloverleaf portion is amended first of all by the inclusion of a conductor running as shown between receive crystals 112 and 124, which crosses over the already provided conductor wire running betwen transmitting crystals 114 and 115. The conductors at this cross-over point are, of course, well isolated. Additionally, there is provided a new conductor running as shown between transmitting elements 115 and 125. Thus it is, that all transmitting transducers are electrically coupled together and all receiving transducers are coupled likewise.

FIG. 4B illustrates a typical area coverage of the transducer assembly of FIG. 4A. There is shown in FIG. 4B the area of most active coverage 160 provided by the assembly, as well as an area of additional but less active coverage 161. These areas are, relative to the size of the assembly illustrated in FIG. 5B, essentially to scale. Both the most active and lesser active areas of coverage appropriately exhibit the abruptness of cutoff of activity resulting from the cut shape of transmitting crystals 114, 116 and 125.

The configuration of transducer assembly depicted in FIGS. 4A and 4B was conceived principally for the purpose of increasing the length of illumination of an expectant mother's abdomen. Of major concern in leading to the development of this configuration is the consideration that the fetus should be monitored continuously as it moves down the birth canal, without requiring a repositioning of the transducer assembly as a result of said fetal movement. Thus, the transducer assembly would normally be placed such that the extended arm portion points in the general direction of the fetal movement during the birth process. It should be noted that as the fetus moves closer to the cervix, it is more limited as to side-to-side movement, due to the narrowing of the birth canal. Therefore, with the transducer assembly configuration of FIGS. 4A and 4B the desired continuous monitoring throughout the birth process is achievable without the need for relocating the assembly.

In this embodiment, as in all embodiments described herein, the beam spread of the lenses is predetermined such that a fetal target as close as 5 cm to the surface will be satisfactorily detected. The pattern illustrated in FIG. 4B, for example, is that which would exist for the configuration of FIG. 4A at a depth of about 11 cm. The transmitting crystals 114, 116 and 125 are cut in the preferred shape illustrated such that when mounted in the associated lens structures, they will illuminate the area specifically selected for maximum fetal activity and best system sensitivity. It is to be noted that the transmitting crystal 115 is a round disc, the circular active surface being provided in this case for illumination in all directions. This is in particular relation to the fact that this active element is situate between the two receive crystals 115 and 125, Both receiving crystals 113 and 124 are disc-shaped to provide circular active surfaces for full 360.degree. coverage. They are larger than the transmitting crystals for ensuring the capability of receiving energy from all directions as generated by the transmitting crystals, and particularly to ensure reception regardless which of the transmitting crystals is most directly illuminating the target. Thus, even as the fetal target moves and the return signal might then be coming from another direction, there is every likelihood that it would be satisfactorily received without having to move the assembly.

Preferred area dimensions for the operational faces of the various active elements are as follows. The area of the individual transmitting crystals 114, 116 and 125 is 2.0 cm.sup.2 and the remaining transmitting crystal 115 is 2.84 cm.sup.2. Thus, the total transmitting crystal area in this configuration is 8.84 cm.sup.2, an increase of some 32 percent over the basic cloverleaf design. The area of the receiving crystals 112 and 124 is in each case 3.87 cm.sup.2, for a total receiving crystal area of 7.74 cm.sup.2, which doubles the area for receiving elements over the basic cloverleaf design.

The lenses for the transmitting and receiving crystals have approximately the same radius of curvature, i.e. preferably 2.5 cm, but it should be noted that the receiver lenses provide greater coverage due to the larger dimensioned active areas of the receiving crystals. While a preferred spacing provided between adjacent active elements is given as c=41/2 cm in the above, and while this also represents the standard preferred dimension of the basic design, it should be noted that if the lens curvatures were to be changed, then different spacing could obtain for the same area coverage.

Referring to FIGS. 5A and 5B, there is illustrated therein a six-element transducer assembly which in essence represents an intermediate between the basic cloverleaf design and the particular embodiment illustrated in FIGS. 4A and 4B. The construction of the FIG. 5A embodiment differs from that depicted in FIG. 4A only in the specific arrangement of the extension of the middle arm 223. As before, similar reference designators are used where appropriate. In this instance, the middle arm 223 is extended, as defined by dashed line 223b, by a portion 223a which houses only a single additional transducer/lens location. However, in this embodiment there is found under lens 223 a receiving crystal 230 and a transmitting crystal 231. Each is slightly less than one-half the area of the full size crystals employed elsewhere, such as crystals 212 and 215 respectively, and these additional crystals resemble half circles in shape. The two crystals 230 and 231 face each other via their cut-off sides, so as to entirely fit beneath the single lens 233. This lens is preferably of a larger radius, such as around 5 cm. The remaining lenses and crystals do not differ substantially from those described with regard to the FIG. 4A embodiment as to location or function, etc.

The conductive intercoupling wiring employed in the arrangement of FIG. 5A retains that provided for the basic cloverleaf design, amended only to add wiring to couple new elemets 230 and 231 thereto. In this instance a first new line runs as shown from receiving crystal 212 to receiving element 230 and a second new line runs in the manner shown between transmitting crystal 218 and transmitting half-crystal 231.

Just as in the case with the FIG. 4A embodiment, it is seen that the basic cloverleaf design has been extended in the one direction, i.e. longitudinally, via the middle arm to illuminate the fetus as it moves towards the cervix. However, this transducer assembly is somewhat shorter in its overall longitudinal dimension than the one depicted in FIG. 4A. In fact, the center-to-center separation e between lens location 218 and lens location 233 preferably is 4 cm. A major advantage of this embodiment would be for use on smaller women as to whom this arrangement would likely prove superior over the FIG. 4A assembly.

FIG. 5B illustrates the coverage provided by this smaller embodiment, broken away, as before, into the most active 260 and lesser active 261 areas. It is to be particularly noted that the coverage of this assembly ranges significantly beyond the physical tip of the extended middle arm, thus enabling greater coverage, particularly for smaller women, throughout the birth process.

Referring now to FIG. 6A, there is illustrated therein an 8-crystal transducer assembly designed to widen as well as lengthen the field of illumination of the standard or basic cloverleaf design. In place of the half-crystal pair arrangement on the straight extended portion of the middle arm as depicted in FIG. 5A, this assembly provides for a relatively wide Y-shaped or hammerhead type extension of the middle arm, with both the left and right side portions of the extension housing a half-crystal pair arrangement under a single lens structure.

More particularly, middle arm 323 of the basic design has been extended by a wide Y or hammerhead-shaped portion 323a, as defined by dashed line 323b. Associated with the left side portion 323c of extended portion 323a is a transmitting crystal 340, a receiving crystal 341 and a lens 342 housing both the aforesaid crystals. This is possible, again, because of the half-circle shapes of active elements 340 and 341 facing each other via their cut-off sides. Transmitting crystal 340 is, for example, of slightly less than half the surface area of transmitting crystal 315. Receiving crystal 341, moreover, has slightly less than half the surface area of, for example, receiving crystal 312. Transmitting and receiving crystals 340 and 341 are situate under a lens having essentially the same dimensions, and in particular the same radius of curvature, as lens 233 illustrated in FIG. 5A. In the FIG. 6A embodiment the center-to-center separation between lens location 342 and lens location 318 is the dimension c, i.e. preferably 41/2 cm. Thus, the preferable separation here is the same as found in the basic cloverleaf design between the central receiving transducer and the outlying transmitting transducers.

As to the right side portion 323d of extension 323a the location, shape, size and arrangement of the additional active elements and lens provided, i.e. transmitting element 343, receiving element 344, and lens 345 are identical with that described with reference to the left side portion 323c. It is noted that the parallel cutoff edges of the crystals 340-343l and of the crystals 343-344 respectively form acute angles with a line drawn between the location centers of their respective lenses, which angles preferably would be in the vicinity of 45.degree.. The center-to-center separation f between the lens locations 342 and 345 is in this assembly preferably 51/2 cm.

The routing of the fine gage wires intercoupling the various active elements in this arrangement is somewhat more complicated as regards the extended portion of the middle arm. In this case a new line is run from receive crystal 312, much like that depicted in FIG. 4A, crossing over the line intercoupling transmit crystals 314 and 315, and passing around the right side of the crystal 315 location to a junction point. There this line devides to run more or less directly to receive half crystals 341 and 344. In a similar manner, an extension lead is brought out from the left side of transmit crystal 315 to be run up the left side of the extension of arm 323 to a second junction point, whereat it divides in leading to the two transmit half crystals 340 and 343. However, between this second junction point and transmit crystal 343, this line crosses over the extended receive conductor just below its junction point. Again, adequate isolation is provided at these crossover points.

Instead of the junction point arrangement described, it may be advantageous from a commercial standpoint as well as flexibility to provide a wire connection running from element 315 along the periphery of the left side of the assembly to contact element 340 at about "9 o-clock." Another wire may be run from element 340 at "12 o-clock" along the periphery of the top portion of the assembly over to element 343 where it would make contact with the latter at the 2 o-clock position. Similarly, a wire conductor could run from receive element 312 along the periphery of the right side of the assembly up to element 344 to make contact therewith at the 7 o-clock position. Then another conductor would be run between element 344 and 341 making contact therewith respectively at the eleven o-clock and one o-clock positions. This conductor would also be arranged along the top periphery of the assembly but inside the transmitting conductor running between elements 340 and 343.

A major advantage of this assembly is that it widens the field of illumination in the lower abdominal area including the area around the cervix, which is perhaps the most critical area for fetal coverage during labor. This assembly is designed to anticipate the situation where the target moves sideways during contractions, and as a result, there would, barring extreme cases, obtain continuous recognizable signals representative of the fetal heartbeat, by reason of the additional wire coverage in the direction of extension of the middle arm.

As is the case with the FIG. 4A and FIG. 5A assemblies, transmit crystals 314 and 316 and receive crystal 312 of the FIG. 6A assembly are identical in size, shape, position, lensing and function to corresponding crystals described with reference to the basic design. Transmit crystal 315 is, of course, circular in shape to illuminate in all directions. Transmitting crystals 340 and 343, while being cut to less than half the area of, for example, transmit crystal 315, are intentionally mounted on the outside at lens location 342 so as to illuminate beyond the assembly proper (see FIG. 6B). Whereas receive crystal 312 is of standard size, receiving crystals 341 and 344 are of a somewhat smaller radius.

The typical field pattern for the FIG. 6A assembly is illustrated in FIG. 6B. This pattern, as is the case in the other embodiments, is dependent in large part on the lenses employed with the active elements of the assembly. In the preferred case the lenses 313, 317, 318 and 319 respectively are the same radius of curvature as that provided for the active elements in corresponding locations of the basic design. The lenses 342 and 345 have equal radii of curvature, considerably less than that of the other lenses. As a result, it is assured that the return beam from a target, rather than exceeding the critical operational angle, will be detected by the adjacent receiving crystal.

As before, typical pattern depicted in FIG. 6B of the areas of most sensitive illumination is broken into the most active 360 and lesser active 361 areas of illumination. To be noted from this coverage pattern, again is the usual lower half coverage characteristic of the basic cloverleaf design, coupled in this instance with the extended upper area of coverage featuring wider illumination due to the presence of the active elements associated with the hammerhead extension 323a of the middle arm.

The spacing between the transmit and receive half-crystals housed by a single lens is filled with, for example, tungsten powder in combination with an epoxy mixture. This reduces to acceptable levels any ultrasonic cross-coupling between these elements, which is a very important consideration for the type of transmission-reception here depicted. This same provision is made for the noted half-crystals employed in the assembly of FIG. 5A.

FIG. 7A illustrates yet another alternative embodiment of preferred transducer assembly, which bears similarity in shape to the assembly depicted in FIG. 6A. The seven-element assembly of FIG. 7A, like the FIG. 6A assembly, is provided with an extension 423a (as defined by dashed line 423b) to the middle arm 423 of the basic design, which extension is shaped like a wide Y. Proximate the base of this extension as defined at 423b there is located in a substantially straight line with standard crystals 412 and 415, an additional receiving crystal 424 and appropriate lensing structure 426. Receive crystal 424 preferably may be spaced apart from transmit crystal 415 in symmetry with the receive crystal 412 position (i.e. by a separation c).

Associated with the left (423c) and right 423d) side portions of the Y-shaped extension 423a, proximate the free ends thereof, is an additional transmit crystal 450, 451 respectively, together with appropriate lensing structures 452 and 453. The center-to-center spacing between these transmit crystal locations respectively and the receive crystal 424 location may preferably be the same as that existing in the basic design, i.e. the spaced separation between receive crystal 424 and any adjacent transmit crystal (415, 450, 451), is c. Also, FIG. 7A shows the center-to-center separation between transmit crystals 450 and 451 and transmit crystal 415 to be the same as the basic design spacing between transmit crystals 414/416 and transmit crystal 415, i.e. the dimension d. That is, the design of this assembly in the preferred configuration is not unlike a mirror image type arrangement of two basic cloverleaf configuration assembled together. However, it is to be noted that whereas a double cloverleaf arrangement coupled together via the respective middle arms would provide for two consecutive transmit crystals adjacent to the junction point of the two center arms, the arrangement of FIG. 7A intentionally provides instead a single transmit crystal, i.e. 415, symmetrically placed at this junction area.

The concept of a double cloverleaf design, though entirely operable in concept and within the scope of the present invention, is not as practical from a power standpoint as, for example, the FIG. 7A assembly. A double cloverleaf arrangement would have a total of eight crystals, i.e. two receive and six transmit. The FIG. 7A arrangement, on the other hand, provides with very reliable operation the same of superior coverage with only seven crystals. This enables more ultrasonic power output relative to crystal surface area. Since in most instances it is preferable, if not essential, to have associated with such transducer assemblies as described herein a fixed electrical power output from the associated electronic equipment, and since ultrasonic output is related to the area of the crystals, then the larger the total crystal area, the lower the ultrasonic power output.

As to the conductive wires intercoupling the various active elements, there is illustrated in FIG. 7A along with the Y-shaped extended portion of middle arm 423 a conductive coupling line provided which runs between receive elements 412 and 424, not unlike that described with reference to the embodiment depicted in FIG. 4A. Additional transmit conductive wires are provided which run as shown respectively between transmit elements 415 and 450 on the one hand and elements 450 and 451 on the other hand.

The principal purposes and advantages of this FIG. 7A assembly are essentially the same as that of FIG. 6A arrangement, namely, for example, to effectively extend the area of illumination both transversely, i.e. side-to-side, and longitudinally. This may be seen in FIG. 7B, wherein a typical coverage pattern is illustrated for the most active (460) and lesser active (461) areas of assembly sensitivity. The illumination and power distribution of this embodiment can be made to appear almost exactly like that of the FIG. 6 assembly, particularly if transmitting crystals 450 and 451 (and also transmitting crystals 414 and 416), instead of being shaped and positioned as illustrated in FIG. 7A, have circular surface area or are oriented essentially the same as to the transmitting crystals 340 and 343 (and also 314 and 316) associated with the FIG. 6A assembly. By this assembly, as is the case with the FIG. 6A assembly, one can illuminate both sides of a normal expectant mother, and more easily and quickly determine what position the baby is in as well as on which side it is situate. This type of wider coverage assembly, then, provides easier target location for subsequent operation without having to relocate the assembly as a result of substantial movements of the fetal target. The assembly is particularly applicable for illuminating a highly active fetus as it moves toward the cervix.

While the principles of this invention have been described above in connection with specific apparatus, it is to be understood that this description is made by way of example and not as a limitation on the scope of the invention as set forth in the objects and features thereof or in the accompanying claims.

Claims

What is claimed is:

1. An ultrasonic multiple-element transducer assembly for use particularly in patient monitoring, comprising a substantially flattened base of homogeneous, flexible material composition, which includes a cloverleaf-like configured portion having a center area with at least three arms extending outwardly therefrom, the arrangement of said arms being such as to be independently flexible relative to each other and to the center area, with each arm having proximate said center area narrower width and thickness dimensions than the other arm area and said center area, for enabling the assembly to conform to varying body curvatures, each of said arms being provided proximate the end thereof remote from said center portion with at least one active element in the form of a transmitting means, said transmitting means being arranged and including lens means for providing overlapping direct beam illumination of a predetermined volume of the interior of the patient's body intended to be monitored, and said center area being provided with at least one active element in the form of an ultrasonic receiving means, said ultrasonic receiving means including lens means arranged to provide illumination of a substantially greater percentage of the portion of the patient intended to be monitored than that provided by the said transmitting means associated with any of said arms of said cloverleaf portion, for enabling detection by said receiver means of ultrasonic energy from whichever of said transmitting means is illuminating the portion of the patient's body intended to be monitored at any time, wherein the middle arm of said cloverleaf configured portion is extended to provide for at least one additional active element for predetermined greater longitudinal and/or transverse coverage.

2. An assembly according to claim 1 wherein a pair of additional active elements is provided on said extension portion of said middle arm in the form of a transmitting means and a receiving means.

3. An assembly according to claim 2 wherein both the cloverleaf and extended portions of said base are constructed so as to virtually eliminate cross-coupling of the ultrasonic energy therethrough between active elements.

4. An assembly according to claim 2 wherein said cloverleaf portion includes a stem appendage by way of which a pair of external conductive coupling elements are introduced into said base to extend therewithin to make electrical contact respectively with said each receiver means and each transmitting means.

5. An assembly according to claim 4, wherein said conductive coupling elements are of fine gauge and are predeterminably disposed in general proximate the periphery of said base and extending from active element to active element, the fine gauge and routing of said coupling elements using such as to optimize the flexibility of the assembly for conformity to the body.

6. An assembly according to claim 2 wherein the thickness and width dimensions of the middle arm are uniformly narrowed between each of the locations of active elements associated therewith in predetermined amount.

7. An assembly according to claim 6 wherein the narrowed width dimension constitutes approximately a 20 percent width reduction and the narrowed thickness dimension constitutes approximately a 50 percent thickness reduction.

8. An assembly according to claim 2 wherein each of the transmitting means associated with the left and right side arms of said cloverleaf portion is predeterminably shaped relative to the lens means associated therewith for limiting radiation of ultrasonic energy to preselected directions, and wherein the receiving means associated with said cloverleaf portion is provided with an operational surface area approximately twice the operative surface area of any one of said predeterminably shaped transmitting means.

9. An assembly according to claim 8 wherein the total operating surface area provided for said transmitting means associated with said cloverleaf portion exceeds the total operative surface area provided for said receiving means associated with said cloverleaf portion approximately by the ratio of 11/2 to 1.

10. An assembly according to claim 8 wherein the lens means associated with the individual transmitting and receiving means of said cloverleaf portion have approximately the same radium of curvature.

11. An assembly according to claim 10 wherein the beam spread associated with said receiving means of said cloverleaf portion is greater than the beam spread of any one of the transmitting means associated with said cloverleaf portion.

12. An assembly according to claim 1 wherein the side arms of said assembly are symmetrically disposed on either side of said middle arm and wherein each said side arms forms a predetermined angle .alpha. with the middle arm.

13. An assembly according to claim 1 wherein said extension to said middle arm is a substantially straight extension having at least one location at which there is provided said at least one additional active element.

14. An assembly according to claim 13 wherein said transducer assembly has a longitudinal axis of symmetry and the straight extension to said middle arm is directed along said axis and said at least one active element location is on said axis.

15. An assembly according to claim 14 wherein said extended portion has a plurality of active element locations, each of which having associated therewith at least one active element.

16. An assembly according to claim 15 wherein said transducer assembly has a longitudinal axis of symmetry along which said straight extension is situate and each of said plurality of active element locations is centered on said axis, and wherein said plurality of locations constitutes a pair of locations each having a single active element and corresponding lens means associated therewith.

17. An assembly according to claim 16 wherein the active element location of said extended portion closest to said cloverleaf portion is provided with a receiving means having a circular operating surface, and the remaining active element location of said extended portion is provided with a transmitting means having an operative surface shaped relative to the lens means associated therewith for limiting radiation of ultrasonic energy to predetermined directions.

18. An assembly according to claim 17 wherein said cloverleaf portion includes a stem appendage by way of which a pair of external conductive coupling elements are introduced into said base to extend therewithin to make electrical contact respectively with each said receiving means and each transmitting means, the conductive coupling element associated with the transmitting means being extended along the periphery of said base to electrically couple to said transmitting means associated with said extended portion and the conductive element associated with the receiving means being extended along the periphery of said base to electrically couple to said receiving means associated with the said extended portion, the extensions of said conductive coupling elements into said extended portion being such as to preserve the flexibility of said transducer assembly throughout.

19. An assembly according to claim 16 wherein the spaced separation between adjacent ones of the active element locations associated with the cloverleaf and extended portions positioned along said axis is constant.

20. An assembly according to claim 16 wherein the active element location of said cloverleaf portion which is closest to said extended portion is provided with a transmitting means having a circular operating surface and associated lens means.

21. An assembly according to claim 15 wherein the center-to-center spaced separation between adjacent ones of said plurality of active element locations is the same as the center-to-center separation between adjacent active element locations associated with said cloverleaf portion.

22. An assembly according to claim 13 wherein there is associated with said straight extension a single active element location at which single location there is provided a pair of active elements in the form of a transmitting means and a receiving means.

23. An assembly according to claim 22 wherein said transmitting means and said receiving means at said single active element location are operatively arranged to be associated with a single lens means.

24. An assembly according to claim 23 wherein the operative surfaces of said receiving means and said transmitting means associated with said single lens means are each shaped substantially in a half circle, with the flat edges thereof facing each other.

25. An assembly according to claim 24 wherein means are provided between said half circle-shaped active elements for preventing cross-coupling of ultrasonic energy therebetween.

26. An assembly according to claim 22 wherein said single active element location is situate at a predetermined spaced separation, center-to-center, from the active element location on said cloverleaf portion closest thereto.

27. An assembly according to claim 26 wherein said predetermined spaced separation is different from the center-to-center separation of any two adjacent ones of the active element locations of said cloverleaf portion.

28. An assembly according to claim 22 wherein said single active element locations is situate closest to a transmitting means location on said cloverleaf portion, said closest transmitting means having a circular operative surface and associated lens means.

29. An assembly according to claim 22 wherein said cloverleaf portion includes a stem appendage by way of which a pair of external conductive coupling elements are introduced into said base to extend therewithin to make electrical contact respectively with each said receiver means and each transmitting means, the conductive coupling element associated with the transmitting means being extended along the periphery of said base to electrically couple to said transmitting means associated with said extended portion and the conductive coupling element associated with the receiving means being extended along the periphery of said base to electrically couple to said receiving means associated with said extended portion the extensions of said conductive coupling elements into said extended portion being such as to preserve the flexibility of said transducer assembly throughout.

30. An assembly according to claim 1 wherein said extension to said middle arm is a substantially Y-shaped extension having an active element location associated with each branch arm of said extension and the base portion thereof communicating with said middle arm.

31. An assembly according to claim 30 wherein said active element location associated with each branch of said Y extension is situate proximate the free end of the respective branch and wherein each said active element location is provided with a pair of active elements in the form of a transmitting means and a receiving means.

32. An assembly according to claim 31 wherein said transmitting means and said receiving means at each said single active element location are operatively arranged to be associated with a single lens means.

33. An assembly according to claim 31 wherein each said active element location is situate a predetermined spaced separation, center-to-center, from the active element location of said cloverleaf portion closest thereto.

34. An assembly according to claim 33 wherein said spaced separation of each branch active element location from the closest cloverleaf portion active element location is the same as the center-to-center separation of any two closest adjacent ones of active element locations of said cloverleaf portion.

35. An assembly according to claim 31 wherein said Y extension is arranged closest to a transmitting means location on said cloverleaf portion, said closest transmitting means having a circular operating surface and associated lens means.

36. An assembly according to claim 31 wherein the operative surfaces of said receiving means and said transmitting means associated with said single lens means are each shaped substantially in a half circle, with the flat edges thereof facing each other.

37. An assembly according to claim 36, wherein means are provided between said half circle-shaped active element for preventing cross-coupling of ultrasonic energy therebetween.

38. An assembly according to claim 31 wherein said cloverleaf portion includes a stem appendage by way of which a pair of external conductive coupling elements is introduced into said base to extend therewithin to make electrical contact respectively with each of said receiver means and each transmitting means, the conductive coupling element associated with the transmitting means being extended within said base to electrically couple to each said transmitting means associated with said extended portion and the conductive coupling element associated with the receiving means being extended within said base to electrically couple to each said receiving means associated with said extended portion, the extensions of said conductive coupling elements into said extended portion being such as to preserve the flexibility of said transducer assembly throughout.

39. An assembly according to claim 31 wherein the center-to-center separation of said active element locations associated with said extended portion is different from the center-to-center separation between any two active element locations associated with said cloverleaf portion.

40. An assembly according to claim 30 wherein there is provided a further active element location proximate the junction point of said branches of said Y extension and wherein said active element location associated with each branch of said Y extension is situate proximate the free end of the respective branch.

41. An assembly according to claim 40 wherein a single active element and associated lens means is provided at each active element location associated with said extended portion.

42. An assembly according to claim 41 wherein the active element location situate proximate the junction of said branches is provided with a receiving means having a circular operative surface and the active element location associated with each of said branches of said Y extension is provided with a transmitting means.

43. An assembly according to claim 42 wherein the operative surface of each said transmitting means associated with said extended portion is predeterminably shaped relative to the lens means associated therewith for limiting radiation of ultrasonic energy to preselected directions.

44. An assembly according to claim 40 wherein said transducer assembly has complete longitudinal and transverse symmetry with regard to the active element locations and with regard to the overall shape of the transducer assembly relative to a center position defined by the active element location on the cloverleaf portion closest to said extended portion.

45. An assembly according to claim 40 wherein the center-to-center spacing of adjacent active element locations is the same throughout the transducer assembly.

46. An assembly according to claim 40 wherein the center-to-center spacing between adjacent transmitting means locations is the same throughout the transducer assembly.

47. An assembly according to claim 40 wherein said cloverleaf portion includes a stem appendage by way of which a pair of external conductive coupling elements is introduced into said base to extend therewithin to make electrical contact respectively with each said receiver means and each transmitting means, the conductive coupling element associated with the transmitting means being extended along the periphery of said base to electrically couple to said transmitting means associated with said extended portion, and the conductive coupling element associated with the receiving means being extended along the periphery of said base to electrically couple to said receiving means associated with said extended portion, the extensions of said conductive coupling elements into said extended portion being such as to preserve the flexibility of said transducer assembly throughout.