Surgery – Diagnostic testing – Cardiovascular
Reexamination Certificate
1996-12-02
2001-04-24
Nasser, Robert L. (Department: 3736)
Surgery
Diagnostic testing
Cardiovascular
C600S488000, C600S561000
Reexamination Certificate
active
06221023
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sensor mounted on an intra-corporeal medical device. More particularly, the present invention relates to a sensor mounted on the distal end of a catheter for detecting pressure acting thereon.
2. Description of the Related Art
Catheters and endoscopes are medical devices that are inserted into passageways in the human body such as blood vessels to perform medical treatment. These devices typically include a tube, which is inserted into the body, and a manipulator for manipulating the tube from outside the patient's body. The tube is inserted into an intra-corporeal passageway, such as a blood vessel. Then, the doctor uses the manipulator to guide the distal end of the tube to a desirable point, where he or she performs measuring (e.g., measurement of the blood pressure) or medical treatment (e.g. vasodilation).
The intra-corporeal passageways are curved and branched and their diameters vary at different locations. In addition, obstacles such as a thrombus may narrow the passageways. The doctor therefore uses the manipulator to bend the tube in order to guide the tube's distal end through branches.
When operating a prior art catheter, the doctor senses an increase in the insertion resistance of the tube based on the tactile feeling from the catheter and thus senses curved parts, narrow parts and obstacles in the passageway. This allows the doctor to determine the advancing direction of the catheter, The doctor needs to be experienced and must sometime use his or her instincts in manipulating the catheter's distal end. Further, judging the direction of the insertion pressure is often difficult.
To solve the above drawback, it has been proposed that a sensor be mounted on the distal end of a tube for detecting the magnitude and direction of pressure applied to the sensor by contact of the sensor and the passage way's inner wall.
Japanese Unexamined Patent Publication No. 6-190050 discloses a medical device having a sensor mounted on the distal end of the tube. The sensor of this publication, which is shown in
FIG. 17
, includes a flexible tube
101
and a plurality of strain gauges provided on the periphery of the tube's distal end. The tube
101
has a plurality of beams
102
and slits
103
at its distal end. The strain gauges are provided mostly on the beams
102
. Contacting the sensor against the inner wall of an intra-corporeal passageway deforms the beams
102
. This causes the strain gauges to issue signals in accordance with impedance based on the deformation of the beams
102
. The magnitude and the direction of the pressure applied to the tube's distal end are measured based on the signal. The doctor determines the advancing direction of the tube by monitoring the measurement results. Determining the advancing direction of the tube is thus facilitated.
However, since the above described strain gauge type sensor has minuscule beams and slits, the manufacturing of the sensor is complicated. This structure is also disadvantageously large.
Further, having projections and recesses as shown in
FIG. 17
, the sensor's distal end often gets snagged even when advancing in a straight passageway. This may develop a thrombus in the passageway.
SUMMARY OF THE INVENTION
Accordingly, it is an objective of the present invention to provide a highly biocompatible sensor mounted on an intra-corporeal medical device for detecting the magnitude and the direction of pressure applied to the device's distal end.
A sensor according to the present invention is mounted on the distal end of a medical device. The sensor includes a chip that becomes deformed in accordance with pressure applied thereto and a piezoelectric element that issues detection signals in accordance with the chip's deformation. The pressure is detected based on the issued signals. The sensor also includes a pressure transmitting element mounted distal to the chip. The transmitting element is smaller then the chip and transmits pressure to the chip. The sensor has a cover covering the piezoelectric element and the pressure transmitting element. The cover impart a tapered shape to the device's distal end.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principals of the invention.
REFERENCES:
patent: 2959056 (1960-11-01), Traite et al.
patent: 3550583 (1970-12-01), Chiku
patent: 3553625 (1971-01-01), Stedman
patent: 3831588 (1974-08-01), Rindner
patent: 4274423 (1981-06-01), Mizuno et al.
patent: 4554927 (1985-11-01), Fussell
patent: 4846191 (1989-07-01), Brockway et al.
patent: 4886070 (1989-12-01), Demarest
patent: 5353800 (1994-10-01), Pohndorf et al.
patent: 6-190050 (1994-07-01), None
Iwata Hitoshi
Matsuba Tomoyoshi
Kabushiki Kaisha Tokai Rika Denki Seisakusho
Nasser Robert L.
Sheridan & Ross P.C.
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