Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
1998-09-24
2001-05-01
Lateef, Marvin M. (Department: 3739)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S437000, C600S443000, C600S448000, C600S463000, C600S466000, C607S115000, C607S116000, C606S130000, C128S899000
Reexamination Certificate
active
06226546
ABSTRACT:
The present invention relates to catheter localization systems which serve to provide data appertaining to a position of a tip of a catheter with reference to a part of the human or animal body.
Catheters provide a means for accessing a remotely located part of the human or animal body via a vein or artery so as to provide a means to perform medical diagnostics or treatment of that part of the body. For example, a catheter may be provided with a sensor disposed on a tip of the catheter which may further comprise an elongated flexible member arranged to move axially within an outer sheath. The tip including the electric sensor is arranged to pass through a vein or artery of the body using the outer sheath and arranged to be positioned at or near the heart so as to provide signals representative of the electrical activity of the heart. In such operations it is an important requirement to be able to determine a position of the catheter head so as to provide correct interpretation of the diagnostic information and correct positioning of the catheter during treatment. A process of determining a position of the catheter head with reference to a three-dimensional image of a part of the body is known as localization.
Electrocardiography is a process for recording electrical signals created by a heart using electrodes applied externally and more particularly electrodes positioned on tips of catheters inserted within the heart. In known endocardial catheter technology, great use is made of in-theatre fluoroscopy to locate and guide catheters to positions within the heart where measurements are required. The use of fluoroscopy has a disadvantage in that inevitably theatre staff and patients are exposed to X-ray radiation.
A further disadvantage with known techniques for catheter localization, is a requirement for correction to be made for the effect of patient movement including movement of the heart caused by its pumping action and movement caused by breathing. In these known systems this movement associated with pumping of the heart and breathing are overcome by relating the measurements taken by the catheter to a particular phase of the heartbeat, and measuring the position of the primary catheter relative to a point or points on a reference catheter. It is this reference catheter that is inserted into the body under the guidance of X-ray fluoroscopy and positioned throughout the procedure in a convenient and anatomically well defined position such as the coronary sinus. The reference catheter serves to provide, to a certain level, some compensation for the movement caused by the patient's breathing and the beat of the heart. This is effected since the movement of both reference and primary catheters will be substantially the same for both catheters. However, use of a reference catheter has a disadvantage in that this requires surgical introduction in addition to the primary catheter which, as an invasive procedure, carries some inconvenience and risk. Furthermore, repositioning of the reference catheter relative to the heart is subject to variability in that it will be difficult to reproduce the same position of the reference catheter in a subsequent introduction of the reference and the primary catheters.
The aforementioned disadvantages represent a technical problem which is addressed by the catheter localization system according to the present invention.
According to the present invention there is catheter localization system for determining a position of a head of a catheter with reference to a part of the human or animal body from mapping information appertaining to a three-dimensional map of said body, said catheter localization system comprising a plurality of acoustic transducers disposed about said catheter head in spaced apart relationship, which catheter head in use is positioned at a predetermined location in said body part, and a signal processing unit which operates to determine said three dimensional map of said body part consequent upon a first set of measurement data appertaining to measured times of flight of acoustic signals generated by at least one of said plurality of acoustic transducers acting as an acoustic signal source and received by said plurality of acoustic transducers acting as acoustic receivers, said times of flight of said acoustic signals being representative of a distance travelled between said source acoustic transducer and said receiver acoustic transducers reflected from said body part.
By arranging for the catheter head to be populated with acoustic transducers, measurements made of distances travelled by acoustic signals from an acoustic transducer acting as a source of the acoustic signals to acoustic transducers acting as acoustic receivers provide information appertaining to a three dimensional representation of the part of the human or animal body in which the catheter is disposed.
Advantageously the catheter head may be moved to at least one other predetermined location, and at least one other set of measurement data generated. The other set of measurement data is representative of a plurality of distance measurements generated from measured times of flight of acoustic signals between at least one of said plurality of acoustic sensors acting as an acoustic signal source, reflected via said part of the body. The signal processing unit may thereafter operate to determine the three dimensional map of said part of the body by matching said first and said other sets of measurement data.
The operation of matching the first and other sets of measurement data may be effected by an image processing algorithm such as an elastic networks algorithm
The measurement data detected by the acoustic transducers acting as receivers may be used by a signal processing unit to determine the location of the acoustic transducers on the catheter head with reference to a reference acoustic transducer.
The signal processing unit may operate to determine the mapping data representative of a three dimensional image of the part of the human body and secondly determine the location of the catheter head with reference to the measurement data in combination with the map of the part of the body.
The catheter tracking system may further include a display means which serves to display said mapping data representative of a three dimensional image of the body part and wherein said catheter head is also displayed.
According to a first aspect of the present invention there is provided a method of determining a position of a catheter head within a part of the human or animal body comprising the steps of
generating acoustic signals from at least one of a plurality of acoustic transducers acting as an acoustic signal source, disposed on said catheter head,
receiving said acoustic signals with said plurality of acoustic transducers acting as acoustic receivers after said acoustic signals have been reflected from a wall of the body part,
determining a first set of measurement data appertaining to distances travelled by said acoustic signals from said at least one acoustic transducer acting as an acoustic signal source to said plurality of acoustic transducers acting as acoustic receivers and determining mapping data representative of a three dimensional map of the part of the human or animal body.
REFERENCES:
patent: 5797396 (1998-08-01), Geiser et al.
patent: 5797849 (1998-08-01), Vesely et al.
patent: 5817022 (1998-10-01), Vesely
patent: 5924990 (1999-07-01), Nachtomy et al.
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Lateef Marvin M.
Lin Jeoyuh
Roke Manor Research Limited
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