ULTRASONIC TRANSDUCER ASSEMBLY
WITH EXTENDED FLEXIBLE CIRCUITS
BACKGROUND OF THE INVENTION
This invention relates to ultrasonic transducer assemblies 5 which are placed within a body cavity to provide ultrasonic images. This invention is particularly directed to an improved extended flexible circuit suitable for use with such transducer assemblies.
Ultrasonic transducer assemblies take many forms, as appropriate for various applications. For example, the ultrasonic transducer assemblies used for assessing intravascular lesions such as stenosis and for monitoring the results of interventional therapy on such lesions are shaped as elon- 15 gated catheters. See for example Yock U.S. Pat. No. 4.794. 931 and Eberle U.S. Pat. No. 5,368.037. Such ultrasonic transducers are often single use, disposable devices, and they can provide any suitable image format, such as a radial format using phased array or rotating crystals. 2o
Conner U.S. Pat. No. 5398.689 discloses an ultrasonic transducer using a flexible circuit inside a sheath in a flexible shaft portion of the transducer assembly. Flexible circuits as described in the Conner patent suffer from the disadvantage that a typical substrate for a flexible circuit has a maximum 25 length of about 19 inches in commercially available forms. Flexible circuits longer than this size can be made in a conveyor-type process, but in many cases the base insulating substrate layer is thicker than that desired for an ultrasonic transducer assembly, because of the stress imposed on the 30 substrate layer in the conveyor system.
McAusland U.S. Pat. No. 4.435,614 discloses one folding geometry for forming elongated flexible circuit traces in an ultrasonic transducer assembly. The geometry illustrated in the McAusland patent suffers from the disadvantage that the 35 folded regions of the flexible circuit provide increased thickness, and the illustrated geometry places these folded regions in positions where they will stack one on top of the other, thereby further increasing the maximum thickness of the flexible circuit. 40
A need presently exists for an improved ultrasonic transducer assembly having extended flexible circuits which have adequate length, and which can readily be configured to minimize the overall thickness of the flexible circuit in its final configuration. 45
SUMMARY OF THE INVENTION
This invention relates to ultrasonic transducer assemblies of the type having an elongated conduit, a plurality of x ultrasonic transducer elements carried by the conduit, and a flexible circuit carried in the lumen of the conduit.
According to a first aspect of the invention, the flexible circuit comprises first, second and third portions. The first and second portions meet at a first fold; the second and third 55 portions meet at a second fold; and at least one of the folds is oriented obliquely to the axis of the lumen.
According to a second aspect of this invention, an ultrasonic transducer assembly as described initially above includes an end portion for the flexible circuit. This end 60 portion comprises an array of substantially parallel grooves, each groove aligned with and exposing a respective one of the conductors of the flexible circuit. A plurality of additional conductors are provided, each extending into a respective one of the grooves and electrically connected to the 65 respective first-mentioned conductor. These additional conductors can be included in an additional flexible circuit or a
ribbon cable, or they can be individually insulated. The grooves of the first-mentioned flexible circuit automatically align the additional conductors during assembly.
According to a third aspect of this invention, the signalcarrying conductors on flexible circuits in a cathetermounted ultrasonic transducer assembly are disposed between and shielded by first and second shielding layers formed as respective flexible circuits.
The preferred embodiments of the invention will now be described with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of an ultrasonic imaging system which includes an ultrasonic transducer assembly that incorporates a presently preferred embodiment of this invention.
FIG. 2 is a cross-sectional view taken along line 2—2 of FIG. 1.
FIG. 3 is a plan view showing the original layout of the flexible circuit included in the embodiment of FIG. 1. prior to final folding and assembly.
FIGS. 4 through 10 are consecutive views showing the manner in which an individual flexible circuit is folded prior to installation into the lumen of FIG. 2.
FIGS. 11-12 are two consecutive views showing the folding of the flexible circuits of the embodiment of FIG. 1.
FIG. 13 is an enlarged view of a portion of FIG. 12, showing the manner in which the folded regions are axially offset from one another.
FIG. 14 is a plan view of an alternative flexible circuit suitable for use in the embodiment of FIG. 1.
FIG. 15 is an enlarged perspective view of an end portion of one of the flexible circuits of FIG. 14.
FIG. 16 is a perspective view of a portion of a mating additional circuit suitable for use with the circuit of FIG. 15.
FIG. 17 is a perspective view showing the circuits of FIGS. 15 and 16 in a mated configuration.
FIG. 18 is a cross-sectional view taken along line 18—18 of FIG. 17.
FIG. 19 is a perspective view showing the flexible circuit of FIG. 15 mated with conductors of a ribbon cable and individually insulated conductors.
DETAILED DESCRIPTION OF THE
PRESENTLY PREFERRED EMBODIMENTS
Turning now to the drawings. FIG. 1 shows a front view of an ultrasound medical diagnostic imaging system 10 which incorporates the presently preferred embodiment of this invention. The imaging system 10 is coupled by a connector 16 and a cable 14 to a handle or control mechanism 12. All of the elements 10-16 are well known to those skilled in the art and can take any suitable form.
As shown in FIG. 1, the control mechanism 12 is connected to a transducer assembly 20, which includes a conduit 22 having a distal end 24 and a proximal end 28. The distal end 24 carries transducer elements 26. and the proximal end 28 may be releasably connected to the control mechanism 12. The connection system at the proximal end 28 may take the form described in U.S. patent application Ser. No. 08/792.291. assigned to the assignee of this invention. The transducer elements 26 can. for example, form a phased array having either a linear or a curvilinear shape. Preferably, the transducer elements 26 and the distal end of the catheter take the form described in U.S. patent application Ser. No. 08/791.598. also assigned to the assignee of