Intracavitary ultrasound and biopsy probe for transvaginal imaging

An ultrasound probe for positioning in the vaginal cavity includes a phased array of transducer elements at one end thereof oriented at an acute angle with respect to the central axis of the probe whereby the imaging field of view is provided by rotating the probe. A biopsy needle assembly snaps onto slots on the probe with a fork and socket fit. A handle on the probe is offset from the central axis of the probe thereby freeing the space around the entrance to the needle guide and facilitating the manipulation by hand of a needle in the guide.

BACKGROUND OF THE INVENTION 
This invention relates generally to ultrasound imaging systems, and more 
particularly the invention relates to an intracavity probe for 
trans-vaginal imaging and including an integrated biopsy adapter. 
Ultrasound imaging has become an important tool in obstetrics for 
monitoring the fetus during early months of pregnancy and for guiding 
needles for the extraction of ovum from the ovary for in vitro 
fertilization and for chorionic villus sampling. Originally, the procedure 
included abdominal imaging and puncture. However, this procedure can be 
painful and risks puncturing the bowel loop. Further, large distance of 
the ovary, uterus, and the fetus to the probe in trans-abdominal scans 
limits image resolution. More recently, trans-vaginal imaging using an 
intracavitary probe has been developed and offers many advantages over 
trans-abdominal imaging. Importantly, the proximity of the organs to the 
probe during early pregnancy are only one to five centimeters from the 
vagina as compared to five to fifteen centimeters for trans-abdominal 
scans. Since the resolution of an image is approximately proportional to 
distance, the trans-vaginal image will be of superior resolution. 
Additionally, since less intervening tissue is between the probe and 
target the signal-to-noise ratio is greatly improved, especially in obese 
patients. Due to the short propagation distance, high frequency imaging 
and accurate tissue characterization using high frequency (e.g. 7-10 MHz) 
imaging is possible in trans-vaginal scans. Further, in trans-abdominal 
scanning a full bladder is required to serve as a "window" for imaging. 
This causes discomfort to the patient and may sometimes delay or 
compromise a scan due to a non-full bladder. Finally, ultrasonic needle 
guidance may be accomplished trans-vaginally for the extraction of ovum 
from the ovary and precise biopsy operations can be performed more safely 
and less painfully. 
One intracavity probe now commercially available employs a mechanical 
section scanning element mounted inside an elongated housing for rotation 
therein. The scanning head is relatively large and the image quality is 
marginal. The probe does accommodate a biopsy needle. Another known probe 
includes an oscillating transducer in an elongated housing. To alter the 
image scan direction the elongated housing must be axially tilted in the 
vaginal cavity, causing discomfort and pain to the patient. The probe does 
not function as a biopsy needle guide. 
SUMMARY OF THE INVENTION 
The present invention is directed to an improved intracavitary ultrasound 
and biopsy probe that provides improved images and is more easily operated 
and manipulated during use. The overall shape, scanned geometry, and 
needle guide are designed for optimal application. 
Briefly, the intracavity ultrasound probe includes an elongated body having 
a central axis, a transducer assembly fastened to one end of the body with 
the transducer assembly having a generally planar surface oriented at an 
acute angle to the axis, and a handle extending from the opposing end of 
the body. A wide field of view is accommodated with the probe by rotating 
the elongated body in the vaginal cavity without requiring a tilting 
thereof. In a preferred embodiment the transducer assembly comprises a 
phased array of transducer elements which improve the focusing and imaging 
of organs and the guidance of the biopsy needle. 
The biopsy needle assembly is detachably mounted to the probe for obtaining 
tissue and fluid samples. The assembly includes a needle and an elongated 
guide for receiving and guiding the needle, the elongated guide having 
projecting members at one end thereof which engage slots in the transducer 
assembly housing in a fork and socket fit. 
In accordance with one feature of the invention the handle of the probe has 
an offset angle from the shaft which frees the space around the entrance 
of the needle guide. The obstruction-free space facilitates the 
manipulation of the needle by hand and accommodates the attachment of an 
automatic needle injector. The needle tip may be retracted inside the 
needle guide between biopsies to avoid accidentally puncturing a patient. 
The probe is designed to accept disposable sterile sheaths or condoms for 
the protection of the patient from bacterial infection during a biopsy and 
to avoid the transmission of disease between patients. 
The invention and objects and features thereof will be more readily 
apparent from the following detailed description and appended claims when 
taken with the drawing.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
Referring now to the drawings, FIG. 1 is a side elevation view of an 
intracavity ultrasound probe shown generally at 10 with a biopsy needle 
assembly shown generally at 12 mounted thereon in accordance with one 
embodiment of the invention. The probe 10 includes an elongated body or 
shaft 14 with a transducer assembly including a boot or housing 16 and a 
transducer array 17 mounted on one end thereof. At the opposing end of 
shaft 14 is a handle 18. A cord 20 includes electrical wires extending 
through the handle 18, shaft 14 and housing 16 to the transducer array 17 
for communicating electrical signals between the transducer array and the 
ultrasound processing and imaging system. 
The biopsy needle assembly 12 includes a guide 22 for a biopsy needle 24. A 
needle stop 26 is provided on the needle 24 for limiting penetration 
thereof. Distance marks 28 on needle 24 facilitate the setting of 
penetration depth. The biopsy needle 24 is hollow, and provided within the 
needle 24 is an inner needle 30 that can be extracted for allowing tissue 
samples to enter the biopsy needle 24. 
FIG. 2 illustrates operation of the intracavity probe as inserted into the 
vaginal cavity of a patient 44 for imaging the ovary, uterus, and fetus 
during early pregnancy, for example. As noted above, these organs are only 
one to five centimeters from the transducer array 17 when placed in the 
vaginal cavity, as compared to 5 to 15 centimeters in the case of 
trans-abdominal scans, thereby facilitating an image of superior 
resolution. 
FIG. 3 is a side view in elevation with the biopsy needle assembly 12 
removed from the probe assembly 10 and further illustrating features 
thereof. Mounted to the forward end of needle guide 22 is a mount 32 
having projections 34 that engage slots 36 in the housing 16. Accordingly, 
the biopsy guide can be snapped into the slots on the probe with the guide 
locked into place with a fork and socket behind the probe head. A disc 38 
on the guide 22 mates with a slot 40 in the handle 18, and a ring clamp 42 
maintains the biopsy assembly 12 firmly in place on the probe assembly 10. 
It will be noted that the probe has a shaft smaller in diameter than the 
head for a wide angle of manipulation. 
As noted in FIG. 3, the shaft 14 has a central axis 48, and the handle 18 
of the probe has an offset angle from the axis, thereby freeing the space 
around the entrance of the needle guide. The obstacle free space 
facilitates the manipulation of the needle by hand and for the optional 
attachment of an automatic needle injector. The needle stop 26 clamps onto 
the needle and will stop the forward motion of the needle at a preset 
distance of penetration. This feature allows the use of substantial force 
in the act of puncture without fear of over-inserting the needle. 
In accordance with another feature of the invention the generally planar 
surface of the transducer array 17 is at an acute angle (e.g. 15.degree.) 
with the axis 48. Therefore, after the probe is inserted into the vaginal 
cavity the probe can be rotated about the axis 48 to increase the field of 
view of the ultrasound image. This mode of operation is less discomforting 
to the patient than is required with the known prior art probes. 
FIG. 4 is an exploded perspective view of the probe and needle assembly 
further illustrating the components thereof. The hollow shaft 14, 
transducer assembly housing 16, and handle 18 are preferably injection 
molded components with the shaft 14 inserted and bonded in the housing 16 
and handle 18. It will be noted that handle 18 has a slot 50 on its upper 
surface for receiving the biopsy guide 22. The transducer array 17 can be 
a conventional phased array of transducer elements as employed in the 
General Electric Company RT 3000 phased array echocardiography system, for 
example. 
The intra-cavity ultrasound probe and biopsy assembly in accordance with 
the invention provides an improved image with a wide angle of view and can 
be employed with minimum discomfort to the patient. The probe is designed 
to accept disposable sheaths, and the sterile biopsy guide can be readily 
snapped onto the slots of the sheath covered probe. 
While the invention has been described with reference to a specific 
embodiment, the description is illustrative of the invention and is not to 
be construed as limiting the invention. Various modifications and 
applications may occur to those skilled in the art without departing from 
the true spirit and scope of the invention as defined by the appended 
claims.