Pulsed doppler probe

A pulsed Doppler probe 10 for monitoring blood flow within a blood vessel 12 includes a sheath 17 and a plurality of electrically conductive wires 26 extending through the sheath 17. The wires 26 have distal ends 28 to which an ultrasonic transducer 18 is operatively connected. The transducer 18 has an operative surface 20, and the probe 10 also includes a means 22 for fixing the orientation of the operative surface 20 with respect to at least one of a longitudinal axis 38 of the sheath 17, and the orientation fixing means 22, or with respect to the distal ends 28 of the electrically conductive wires 26. The orientation fixing means 22 includes an epoxy material 24 encasing the ultrasonic transducer 18, shaped to include a cylindrically concave surface 30. The probe 10 further includes a mesh band 44 of at least one of an absorbable material and an inert material adapted to encircle the blood vessel 12. The probe 10 also includes a remotely operable means 46 for detachably securing the orientation fixing means 22 to the mesh band 44 so that the ultrasonic transducer 18 is positioned adjacent to the blood vessel 12 with the concave surface 30 of the encasing material 24 facing the blood vessel 12.

TECHNICAL FIELD 
This invention relates generally to medical devices, and more particularly 
to devices for monitoring the flow of blood in a blood vessel during or 
after a surgical procedure. 
BACKGROUND OF THE INVENTION 
A variety of microsurgical procedures have been developed which have saved 
the lives of patients and/or improved the quality of life for patients. 
Such procedures include organ transfer surgery, reconstructive surgery 
following the removal of tumors (particularly in the areas of the head and 
neck), CABG procedures, and reconstructive surgery such as free tissue 
transfer and the like. Free tissue transfer entails the removal of tissue 
and/or muscle from one part of the body, along with an associated artery 
and vein, and the reattachment of the tissue and/or muscle to another part 
of the body. The artery and vein of the transferred tissue and/or muscle 
are then anastomosed (that is, connected) to a native artery and vein in 
order to achieve blood circulation in the transferred tissue and/or 
muscle. 
The success of such transfer lies in obtaining good patency of the 
anastomosis, and hence good patency in the transferred tissue and/or 
muscle (sometimes referred to as the flap). The primary complication in 
microvascular surgery such as free tissue transfer is thrombosis. 
Unrecognized thrombosis reduces patency in the flap and reduces the 
probability of salvaging the flap. The window of opportunity for salvage 
after thrombosis is presently believed to be only about six hours of warm 
ischemia. It is therefore critical that any vascular thrombosis in a 
transferred flap be recognized and any resulting ischemia be remedied as 
soon as possible. While the success rate of the free tissue transfer 
procedure is quite good, believed to be about 90% on average, failure 
rates have been reported ranging from 6% to 21%. Even though these are 
fairly low, any surgical failure can be costly in several ways, and it 
would of course be highly desirable to reduce the failure rate of this and 
similar techniques. 
A variety of operative and post-operative monitoring techniques are 
presently used for clinically assessing thrombosis and identifying the 
resulting ischemia. Electromagnetic flowmetry is a definitive technique to 
monitor blood flow; but so far this technique has proven too difficult to 
use in free tissue transfer. Some of the other techniques that have been 
clinically studied include intravenous fluorescein, transcutaneous oxygen, 
tissue pH, pulse oximetry, muscle contractility, temperature, 
photoplethysmography, electrical impedance plethysography, and the like. 
Unfortunately; these techniques are not useful for monitoring bone flaps 
or other flaps which are located well below the skin, that is, buried. 
Newer techniques include surface temperature measurement, pO.sub.2 
monitoring, and laser Doppler flowmeters, but these also require the 
presence of an exposed portion of the flap, and are of no benefit for 
monitoring bone or buried flaps. Moreover, none of these techniques 
evaluates the flow of blood at the microvascular anastomoses directly. 
Thus, no technique has been universally accepted as an adequate monitor of 
thrombosis. 
One assessment technique gaining wider acceptance is the use of an 
implantable ultrasonic Doppler probe positioned directly on the 
anastomosed vein and/or the artery. Such a probe includes an implanted 
piezoelectric transducer carried on a band or sleeve attached directly on 
the blood vessel of interest. The transducer is used to alternately 
generate ultrasonic waves and measure backscattering of those waves. Since 
blood is a very effective backscattering medium, the Doppler shift in the 
frequency of the backscattered ultrasonic waves yields a precise and 
accurate measurement of the blood velocity (and, by implication from the 
cross-sectioned area of the blood vessel, the volume of blood flow) in the 
vessel of interest. Signals relating to the phasic velocity and mean 
velocity of the blood can also be obtained. The Doppler probe is thus 
advantageous over prior techniques in that it permits easy monitoring of 
vascular patency in even buried flaps, and can be used to monitor patency 
continuously over a period of days. Careful monitoring of blood flow 
should provide a sufficiently early warning of thrombosis that the chances 
of salvaging the flap are significantly increased. 
Unfortunately, the use of known ultrasonic Doppler probes and techniques 
has been subject to a number of drawbacks. The two most significant 
drawbacks have been the inability to securely place the probe on the blood 
vessel (perivascularly), and thus ensure proper orientation of the 
operative surface of the piezoelectric transducer, so as to acquire 
reliable signals from the transducer; and the difficulty of removing the 
probe from the vicinity of the blood vessel without the use of 
anaesthesia, or without performing an additional surgical incision or 
reopening an old incision. 
For example, U.S. Pat. No. 5,289,821 (William M. Swartz, Mar. 1, 1994) 
discloses a device in which electrically conductive wires carrying an 
ultrasonic transducer are connected by a silicone adhesive to a 
biologically inert or absorbable strip, the strip being wrapped about the 
blood vessel of interest. After three to seven days, when monitoring is 
complete, an incision is made to detach the wires from the strip, and the 
transducer removed from the patient by pulling on the wires. While the 
patent asserts that this new incision is very small, it is difficult to 
see how a practitioner could withdraw the transducer, wire, and the 
sealant without causing trauma to the surrounding tissue or, even worse, 
the anastomosed vessel. To minimize this removal trauma, the practitioner 
would normally make the incision large enough to permit this withdrawal. 
However, the enlarged incision would cause unnecessary discomfort to the 
patient. Moreover, the device lacks structure to maintain orientation of 
the transducer during introduction to and implantation on the blood 
vessel, or from breaking off the transducer and/or the wires during 
removal. Failure to maintain proper orientation of the transducer can lead 
to false blood flow or velocity readings and as a result cause further 
surgical intervention with associated patient discomfort and prolongation 
of the monitoring process. 
Other known devices and techniques have their own drawbacks. Accordingly, 
it would be highly desirable to achieve a device for monitoring blood flow 
during or after a surgical procedure which can be easily and quickly 
attached to a blood vessel. It would also be highly desirable that such a 
probe be firmly attachable to the blood vessel, such that reliable and 
repetitive monitoring signals be acquired for the period necessary to 
ensure patency of the surgical procedure, for example, for at least three 
weeks. It would also be advantageous for such a probe to be easily 
removable from the patient without entailing the performance of additional 
invasive procedures; ideally, the probe would be removable at the 
patient's bedside, with an ease equal to that of removing a conventional 
drainage catheter. It is also desirable that such a probe be useful with 
arteries as well as veins, and be useful for monitoring vessels having a 
range of diameters, particularly, those above 1 mm diameter. Of course, it 
would be essential to ensure that the orientation of the operative surface 
of the ultrasonic transducer be fixed, and to reduce or eliminate any 
potential for detachment of the transducer from the probe or sheath 
carrying it. 
SUMMARY OF THE INVENTION 
The foregoing problems are solved and a technical advance is achieved in an 
illustrative pulsed Doppler probe for monitoring and, preferably, 
measuring blood velocity within a blood vessel. The probe of the present 
invention first comprises a longitudinally extending sheath and a 
plurality of electrically conductive wires extending longitudinally 
through the sheath. The probe also comprises an ultrasonic transducer that 
has an operative surface and is operatively connected to the distal ends 
of the conductive wires. The orientation of the operative surface is fixed 
by an orientation fixing means carried by the sheath and is also fixed 
with respect to at least one of the longitudinally extending wires or the 
longitudinal axis of the orientation fixing means or the sheath. In 
operation, the longitudinally extending wires or the axis of the sheath or 
the orientation fixing means is positioned parallel to the axis of the 
blood vessel so that the operative surface of the transducer is positioned 
relative to the axis of the blood vessel. 
The orientation fixing means preferably includes an epoxy material encasing 
the ultrasonic transducer and the distal ends of the wires, the material 
being shaped to include a cylindrically concave surface. As a result, the 
orientation of the transducer is also fixed with respect to the concave 
surface. The probe preferably includes a plural bore ceramic tube 
connecting the sheath and the orientation fixing means, through which the 
wires pass. The probe further includes a mesh band that is at least one of 
an absorbable material and an inert material adapted to encircle the blood 
vessel. 
The probe also comprises a remotely operable means for detachably securing 
the orientation fixing means to the mesh band so that the ultrasonic 
transducer is positioned adjacent to the blood vessel with the concave 
surface of the encasing material facing the blood vessel. The detachable 
securing means preferably includes: (a) a transverse bore through the 
encasing material; (b) a longitudinally extending severable thread 
slidably passing through the transverse bore and the sheath, the thread 
including first and second free ends external to the sheath and remote 
from the encasing material; and (c) a longitudinally split, removable 
collar on the sheath, positioned over the free ends of the thread, 
frictionally retaining the free ends of the thread against the sheath. 
The sheath and the orientation fixing means are preferably isodiametric, 
that is, they are generally circular in cross-section and have 
substantially the same diameter, thereby facilitating removal of the probe 
upon operation of the securing means. Advantageously, the diameter of the 
sheath and the orientation fixing means are about the same as the blood 
vessel which the probe is intended to monitor. For example, if the blood 
vessel of interest has a diameter of about 4 mm downstream of the 
anastomosis, the sheath and orientation fixing means can have a diameter 
in range of about 0.5 to 2 mm and, preferably, 2 mm. 
In a first aspect, then, the present invention is directed to a pulsed 
Doppler probe for monitoring and preferably measuring blood velocity 
within a blood vessel, comprising: a plurality of longitudinally extending 
electrically conductive wires having distal ends; an ultrasonic transducer 
operatively connected to the distal ends of the wires, the transducer 
having an operative surface; means having a longitudinal axis and fixing 
the orientation of the operative surface of the ultrasonic transducer with 
respect to at least one of the longitudinally extending electrically 
conductive wires or the longitudinal axis of the orientation fixing means; 
a band adapted to encircle the blood vessel; and remotely operable means 
for detachably securing the orientation fixing means to the band so that 
the ultrasonic transducer is positioned adjacent to the blood vessel; 
whereby remote operation of the securing means permits withdrawal of the 
ultrasonic transducer, wires and orientation fixing means from the blood 
vessel while leaving the band encircled about the blood vessel. This first 
aspect of the invention is also directed to various additional elements 
identified above. 
In a second aspect, the present invention is directed to a pulsed Doppler 
probe for monitoring and preferably measuring blood velocity within a 
blood vessel, comprising: a longitudinally extending sheath having a 
longitudinal axis; a plurality of electrically conductive wires extending 
longitudinally through the sheath, the wires having distal ends; an 
ultrasonic transducer operatively connected to the distal ends of the 
wires, the transducer having an operative surface; means having a 
longitudinal axis and fixing the orientation of the operative surface of 
the ultrasonic transducer with respect to at least one of the 
longitudinally extending electrically conductive wires and the 
longitudinal axis (38), and of the orientation fixing means (22) and the 
sheath (17) the orientation fixing means comprising an epoxy material 
encasing the ultrasonic transducer and shaped to include a cylindrically 
concave surface; a mesh band of at least one of an absorbable material and 
an inert material, adapted to encircle the blood vessel; and remotely 
operable means for detachably securing the orientation fixing means to the 
mesh band so that the ultrasonic transducer is positioned adjacent to the 
blood vessel and the concave surface of the encasing material facing the 
blood vessel; wherein the securing means comprises: (a) a transverse bore 
through the encasing material; and (b) a longitudinally extending 
severable thread slidably passing through the transverse bore and the 
sheath, the thread including first and second free ends external to the 
sheath and remote from the encasing material; and wherein the sheath and 
the orientation fixing means are generally circular in cross-section and 
have substantially the same diameter, thereby facilitating removal of the 
probe upon operation of the securing means. This second aspect is also 
directed to such a probe in which the securing means further comprises a 
removable collar on the sheath, positioned over the first and second free 
ends of the thread so as to frictionally retain the first and second free 
ends of the thread against the sheath. 
In a final aspect, the present invention is directed to a pulsed Doppler 
probe for monitoring and preferably measuring blood velocity within a 
blood vessel, comprising: a longitudinally extending sheath having a 
longitudinal axis; a plurality of electrically conductive wires extending 
longitudinally through the sheath, the wires having distal ends; an 
ultrasonic transducer operatively connected to the distal ends of the 
wires, the transducer having an operative surface; means having a 
longitudinal axis and fixing the orientation of the operative surface of 
the ultrasonic transducer with respect to at least one of the 
longitudinally extending wires and the axis of the means and the sheath, 
the orientation fixing means comprising an epoxy material encasing the 
ultrasonic transducer and shaped to include a cylindrically concave 
surface; a ceramic tube connecting the sheath and the orientation fixing 
means, the wires passing through the ceramic tube; a mesh band of at least 
one of an absorbable material and an inert material adapted to encircle 
the blood vessel; and remotely operable means for detachably securing the 
orientation fixing means to the mesh band so that the ultrasonic 
transducer is positioned adjacent to the blood vessel and the concave 
surface of the encasing material faces the blood vessel; wherein the 
securing means comprises: (a) a transverse bore through the encasing 
material; (b) a longitudinally extending severable thread slidably passing 
through the transverse bore and the sheath, the thread including first and 
second free ends external to the sheath and remote from the encasing 
material; and (c) a removable collar on the sheath, positioned over the 
first and second free ends of the thread so as to frictionally retain the 
first and second free ends of the thread against the sheath; and wherein 
the sheath and the orientation fixing means are generally circular in 
cross-section and have substantially the same diameter, thereby 
facilitating removal of the probe upon operation of the securing means.

DETAILED DESCRIPTION 
FIGS. 1 and 9 depict the preferred embodiment of the present invention as a 
pulsed Doppler probe 10 positionable against a blood vessel 12. It is an 
advantage of the present invention that the probe 10 can be positioned on 
a blood vessel 12 which is either arterial or venous. 
With additional attention to FIGS. 2 and 3, the probe 10 first comprises a 
sheath 17 carrying at its distal end 16 a transducer head 14. The sheath 
17 can be composed of any medical grade, biocompatible material, for 
example, PVC. For use with blood vessels of about 1-16 mm diameter, the 
sheath diameter can conveniently be about 6 French (2 mm). A plurality of 
and preferably two insulated, electrically conductive wires 26 are 
positioned in and extend longitudinally through the sheath 17. The 
transducer head 14 comprises an ultrasonic piezoelectric transducer 18 
that is operatively connected to the distal ends 28 of the wires 26. The 
wires 26 are preferably 0.005 inch diameter insulated copper wires, 
although other materials are of course also suitable. Connection of the 
transducer 18 to the wires 26 can be made in any conventional manner, for 
example, by soldering or adhesive. The transducer 18 has an operative 
surface 20 facing the blood vessel 12 at angle 21 of about 30 to 60 
degrees, preferably at an angle of about 45 degrees with respect to the 
longitudinally extending wires 26 or longitudinal axis 38 of the sheath 17 
or head 14. Conveniently, as shown in FIGS. 7 and 8, the insulated wires 
26 are contained within sheath 17, and the unoccupied space within the 
sheath 17 about its distal end is filled with silicone 80. 
With reference again to FIGS. 1-3, the transducer head 14 of the probe 10 
also comprises a means 22 for fixing the orientation of the operative 
surface 20 with respect to at least one of the longitudinally extending 
wires 26, sheath 17, or head 14. However, in use, the orientation of 
operative surface 20 should be positioned and fixed with respect to the 
longitudinal axis of the blood vessel. Most conveniently, the orientation 
fixing means 22 comprises a material 24 encasing the ultrasonic transducer 
18 and the distal ends 28 of the wires 26. The encasing material can be 
any medical grade, biocompatible material, which transmits ultrasound 
waves sufficiently well to achieve good signal strength during use of the 
probe 10. Conveniently, the encasing material 24 is an epoxy, but a 
variety of other materials are useful as well. 
The sheath 17 thus carries at its distal end 16 both the ultrasonic 
transducer 18 and the orientation fixing means 22. A conventional plug 40 
is carried on the proximal, remote end 42 of the sheath 17, opposite 
distal end 16, for connection of the electrically conductive wires 26 to 
an appropriate ultrasound frequency generator, back-scattering sensor and 
suitable computer control equipment (not shown). The nature of these 
devices is not believed to be critical to the present invention, and their 
selection and use should be well within the ability of those of even 
rudimentary skilled in the art. By way of example, however, it has been 
found convenient to use a 20 MHz piezoelectric transducer 18 energized by 
a 20 MHz pulsed ultrasound energy generated by a PD-20 Doppler Velocimeter 
(Crystal Biotech Inc.), with a pulse repetition (burst) frequency of 62.5 
KHz and 8 cycles per burst. The range gate for such equipment can vary 
from 1 mm to 10 mm, employed with a sample volume of about 1 mm.sup.3. 
This yields about 1 mm as the smallest vessel diameter with which this 
equipment is useful. 
With additional reference to FIG. 3, it has been found convenient during 
construction of the probe 10 of the present invention to include a ceramic 
tube 32 at the distal end 16 of the sheath 17 for connecting the 
transducer head 14 to the sheath 17, and in particular, for connecting the 
orientation fixing means 22 to the sheath 17. The ceramic tube 32 includes 
at least one and preferably two longitudinal throughbores 33 in which the 
wires 26 are disposed. Preferably, a proximal remote end 36 of the ceramic 
tube 32 is received in the bore of the sheath 17 at the distal end 16, and 
a distal end 34 of the tube 32 is encased in the orientation fixing means 
22. 
With respect to the particular configuration of the sheath 17 and the 
orientation fixing means 22, it is highly preferred that the sheath 17 and 
the orientation fixing means 22 are generally circular in cross-section 
and be isodiametric, that is, that they have substantially the same 
diameter, so as to facilitate smooth removal of the probe 10 from the 
vicinity of the blood vessel 12 without surgical intervention, incision, 
anaesthesia or significant discomfort to the patient. As a result, the 
longitudinal axis of the sheath and head should coincide. By way of 
example, if the blood vessel 12 is about 4 mm in diameter, the diameter of 
the sheath 17 and the orientation fixing means 22 should be in range of 
about 0.5 to 2 mm and, preferably, 2 mm for a 4 mm or larger vessel. 
However, as shown in FIG. 4, it is also convenient that the orientation 
fixing means 22 be shaped to include a slightly cylindrically concave 
surface 30 facing the blood vessel 12. This serves to both orient the 
transducer head 14 and improve the transmission of ultrasound waves 
between the transducer 18 and the interior of the blood vessel 12. This 
also prevents the transducer head from rotating on the blood vessel. 
With continued reference to FIGS. 1, 2, and 9, the probe 10 of the present 
invention also comprises a band 44 carried on the sheath 17 adjacent to 
the transducer head 14. The band 44 is adapted to encircle the blood 
vessel 12 and hold the transducer head 14 against the blood vessel 12. The 
band 44 can be composed of any medical grade, biocompatible absorbable 
and/or inert material and is preferably configured as a mesh. The band 44 
is most preferably composed of Vicryl.TM. mesh (Ethicon, Inc.) and is 
secured closely about the blood vessel 12 in any convenient fashion, for 
example, by a plurality of medical grade, biocompatible sutures 82. 
The probe 10 of the present invention further comprises a remotely operable 
means 46 for detachably securing the transducer head 14 and, in 
particular, orientation fixing means 22 to the band 44, so that the 
ultrasonic transducer 18 is positioned adjacent to the blood vessel 12, 
and that the operative surface 20 of the transducer 18 is held in position 
facing the blood vessel 12. Remote operation of the securing means 46 
permits withdrawal of the transducer head 14 (the ultrasonic transducer 18 
and the orientation fixing means 22) and the electrically conductive wires 
26 from the blood vessel 12, while leaving the band 44 encircled about the 
blood vessel 12. More particularly, a 0.013 inch transverse bore 50 is 
provided in the transducer head 14, specifically, through the encasing 
material 24. The securing means 46 comprises a longitudinally extending 
filamentous thread 48 slidably passing through the sheath 17 and slidably 
passing through the transverse bore 50. The thread 48 can conveniently be 
composed of nylon monofilament or another medical grade, biocompatible 
material. 
As more clearly shown in FIGS. 2, 3, 5, 6, and 8, the thread 48 is 
preferably disposed in a pair of tubing segments 56 and 58 positioned in 
the sheath 17, entering the sheath 17 through a pair of 180 degree 
opposing holes 52 at the distal end 16 of the sheath 17, and exiting the 
sheath 17 through a proximal pair of holes 54 located between the distal 
end 16 and proximal end 42 of the sheath 17. The tubing segments 56 and 58 
are conveniently composed of a medical grade, biocompatible material, 
preferably polyimide tubing. These segments are held in position in sheath 
17 by silicone 80 that is injected into the bore of the sheath at its 
distal end. The proximal, remote holes 54 are preferably (although not 
necessarily) located outside the body of the patient when the band 44 
holds the transducer head 14 on the blood vessel 12. 
The thread 48 passes through the band 44, through the bore 50 and back 
through the band 44, to secure the transducer head 14, and, in particular, 
to secure the orientation fixing means 22 to the band 44. Severing of the 
thread 48 at any location along its length will allow it to be withdrawn 
from the vicinity of the band 44 and the bore 50, thereby detaching the 
transducer head 14 (more specifically, the orientation fixing means 22) 
from the band 44 and allowing the sheath 17, the transducer head 14 
(including the transducer 18 and the orientation fixing means 22) and the 
wires 26 to be easily withdrawn from the patient without anaesthesia, 
discomfort, incision or other surgical intervention. Such severing of the 
thread 48 is most conveniently carried out by severing the thread 48 at a 
location 84 remote from the distal end 16 of the sheath 17. 
The thread 48 can be configured as a simple closed loop. However, as more 
particularly shown in FIGS. 5 and 6, the thread 48 preferably includes 
first and second free ends 60 and 64 external to the sheath 17, exiting 
the sheath 17 through the holes 54. The first free end 60 of the thread 48 
bears on it a graspable button 62, while the second free end 64 of the 
thread 48 exits the tubing segment 58 and is folded over it, then fixed to 
the outside of the tubing segment 58 by an overlying polyethylene shrink 
wrap tube 66. A plug or bead 68 composed of PTFE polymer (such as TEFLON) 
seals the open end 70 of the shrink wrap tube 66. 
The free ends 60 and 64 of the thread 48, as well as their associated 
coverings, are frictionally retained against the sheath 17 by a removable 
silicone collar 72, which is also part of the securing means 46 (FIGS. 1 
and 5). The collar 72 is longitudinally split and lies over the free ends 
60 and 64 of the thread 48. The collar 72 is closed and held in position 
on the sheath 17 by a wrapping 74, e.g., a suture received in a 
circumferential groove 76 formed on the outer surface 78 of the collar 72. 
The collar 72 can be slid along the sheath 17 to ensure that a suitable 
tension is maintained on the thread 48 during introduction of the probe 10 
and that the location 84 of severing of the thread 48 is readily available 
when removal of the probe 10 is desired. 
Construction of the probe 10 according to the present invention is 
straightforward and should be readily understood from the foregoing 
details. However, encasement of the ultrasonic transducer 18 in the epoxy 
or other material 24 should be performed with due care. One convenient way 
to do this is to first attach the wires 26 to the transducer 18, then feed 
the wires 26 through the throughbores 33 in the ceramic tube 32. The 
desired angle of the operative surface 20 of the transducer 18 is 
established by manipulation, and a small drop of epoxy applied to the 
transducer 18 and ceramic tube 32 to prevent the angle from being altered 
during further assembly of the probe 10. Once the epoxy drop is cured, the 
ceramic tube 32 and the transducer 18 can be introduced into a silicone 
rubber mold, and epoxy injected into the mold to form the shape of the 
transducer head 14. Once the epoxy has cured, any flash or sharp contours 
can be ground off, and the transverse bore 50 drilled into the material 
24. 
Use of the probe 10 according to the present invention is straightforward 
as well. During or after a surgical procedure, and before wound closure, 
the band 44 is secured about the blood vessel 12 of interest by the 
sutures 82 in such a way as to abut the concave surface 30 of the encasing 
material 24 against the blood vessel 12. This affirmatively orients the 
operative surface 20 of the ultrasound transducer 18 with respect to the 
blood vessel 12. The plug 40 on the proximal, remote end 42 of the sheath 
17 is connected to conventional ultrasound generating and sensing 
equipment, and the probe 10 is checked to ensure that it is properly 
monitoring the flow of blood within the vessel 12. The surgical incision 
is then closed, preferably (although not necessarily) leaving the collar 
72 and the free ends 60 and 64 of the thread 48 outside the body of the 
patient. The velocity of blood in the blood vessel 12 is monitored for an 
appropriate time, for example, three to twenty-one days, to ensure the 
patency of the anastomosis and the patency of the transferred flap. 
Once monitoring is no longer required, the probe 10 is easily removed from 
the patient by severing the thread 48 and releasing the transducer head 
14, specifically, the orientation fixing means 22, from the band 44. More 
particularly, the collar 72 is surgically exposed and, if necessary, a 
razor employed to cut the wrapping 74. The collar 72 is then removed from 
the sheath 17, exposing the second free end 64 of the thread 48. The 
thread 48 is cut by scissors at the location 84, in particular, by cutting 
through the tubing segment 58 outside the sheath 17. The button 62 is then 
grasped and the first free end 60 of the thread 48 pulled to draw the 
thread 48 completely through the bore 50 and the band 44, and out one of 
the remote holes 54. Once the thread 48 is withdrawn, there is no other 
securement of the transducer head 14 or the orientation fixing means 22 to 
the band 44, and the sheath 17 and other elements of the probe 10 can be 
easily withdrawn from the body of the patient. The band 44, of course, 
remains in the patient, and may or may not become absorbed within the 
patient thereafter, depending upon its composition. 
The present invention thus provides a pulsed Doppler ultrasound probe which 
is convenient to use, one which prevents detachment of the ultrasound 
transducer from the sheath carrying it, and which is easily removed after 
monitoring is complete, without entailing a surgical incision, excision or 
other technique, or anaesthesia or patient discomfort. The details of its 
construction or the composition of its various elements which are not 
otherwise disclosed are not believed to be critical to the achievement of 
its advantages, so long as the elements possess the strength or 
flexibility needed for them to perform as disclosed. The selection of 
these and other details of construction are believed to be well within the 
ability of one of even rudimentary skills in this area, in view of the 
present disclosure. 
Industrial Applicability 
The present invention is useful in the performance and monitoring of 
surgical procedures, and therefore finds applicability in human and 
veterinary medicine. 
It is to be understood, however, that the above-described device is merely 
an illustrative embodiment of the principles of this invention, and that 
other devices and methods for using them may be devised by those skilled 
in the art, without departing from the spirit and scope of the invention. 
It is also to be understood that the invention is directed to embodiments 
both comprising and consisting of the disclosed parts.