Surgery – Diagnostic testing
Reexamination Certificate
1999-05-03
2002-08-13
Winakur, Eric F. (Department: 3736)
Surgery
Diagnostic testing
C600S309000, C600S500000, C128S899000
Reexamination Certificate
active
06432050
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a biosensing system and method for monitoring internal physiological conditions of a patient. More particularly, the present invention relates to a biosensor system implantable in a patient's body that includes at least one sensor, an active acoustic transducer and a miniature processor. The sensor is used to monitor a physiological condition of the patient and relay information pertaining to the physiological condition through the miniature processor to the active acoustic transducer. The active acoustic transducer transmits this information out of the patient's body as an acoustic signal. Transmission of an acoustic signal from the transducer is triggered by an externally generated acoustic interrogation and energizing signal, which is produced by a second acoustic transducer positioned externally, yet in intimate contact with, the patient's body. The miniature electronic processor is utilized for the various required functions such as conditioning, digitization and amplification of the sensor signals. The biosensor of the present invention can also include a shunt and a monitoring device embedded in the walls of the shunt for permitting identification and non-invasive testing of the operation of the shunt via the acoustic transducer.
Many medical conditions require the monitoring and measurement of internal physiological conditions of a patient. For example, hydrocephalus, which is a brain condition where cerebrospinal fluid accumulates at abnormally high pressures in ventricles or chambers of a patient's brain, may require monitoring of the intra-cranial fluid pressure of the patient.
Implantable devices for monitoring internal physiological conditions of a patient are known in the art. One such prior art device includes an implantable pressure sensor that transmits pressure signals out of the patient by mechanism of a wire or contact passing through the patient's skull (see, for example, U.S. Pat. No. 4,677,985). These types of devices are generally unsatisfactory due to increased risk of infection and patient discomfort caused by the externally extending wire.
Monitoring devices that are completely implantable within a patient are also known in the art. One such prior art devices is described in U.S. Pat. No. 4,471,786 and includes a sensor for sensing a physiological condition of the patient and a transmitter and battery assembly for transmitting the sensor signals out of the patient's body. These types of devices are also unsatisfactory for many types of medical conditions since the batteries are bulky and must be periodically replaced, thus necessitating additional surgery.
Implantable monitoring devices that do not require batteries have also been developed. Such devices (see, for example, U.S. Pat. Nos. 3,943,915 and 4,593,703) employ sensors coupled with frequency tuned Lumped-Constant (L-C) circuits. The sensors mechanically translate changes in sensed physiological condition to the inductor or capacitor of the tuned L-C circuit for changing the reactance of the L-C circuit. This change in reactance alters the resonant frequency of the circuit, which is then detected by an external receiver and converted to a signal representative of the monitored physiological condition.
Although these L-C type implantable monitoring devices are superior to battery operated devices in some respects, they also suffer from several limitations that limit their utility. For example, the L-C circuits are difficult to calibrate once implanted, are inherently single-channel, and are only sensitive in a particular range of measurements. Thus, L-C type monitoring devices are not always accurate after they have been implanted for a long period of time and are not suitable for use with sensors that have a wide sensing range. In addition, no processing power is provided.
Another implantable monitoring device that does not utilizes wire connection or a battery supply makes use of large electromagnetic antennae to provide the energy required for the data processing inside the body. These antennas are big and risky to implant. Also, due to the high absorption of electromagnetic energy by human tissue, only subcutaneous implants are used, and energy into the depth of the body is realized by wiring coupling. Only small amounts of electromagnetic energy can be transmitted from an external antenna directly to a monitoring device deep in the body.
A general limitation of all of the above-described prior art implantable monitoring devices is that they are operable for sensing or monitoring only one physiological condition. Thus, if a doctor wishes to monitor, e.g., both the pressure and the temperature of the fluid in the ventricles of a patient's brain, two such devices must be implanted.
Furthermore, these prior art implantable devices merely monitor a physiological condition of the patient and transmit a signal representative of the condition out of the patient's body, but do not perform any processing or conversion of the signals.
In addition, due to inherent design limitations, these devices cannot be utilized for alleviating the underlying cause of the physiological condition monitored. For example, intra-cranial pressure sensors designed for use with patients suffering from hydrocephalus merely detect when fluid pressure levels within the patient's brain are high, but are not operable for reducing the amount of cerebrospinal fluid accumulated in the patient's brain. Thus, once these prior intra-cranial pressure sensors determine that the pressure in the patient's brain is too high, surgery must be performed to alleviate the condition.
An improved implantable biosensor for monitoring and alleviating internal physiological condition such as intracranial pressure has been described in U.S. Pat. No. 5,704,352 which discloses a biosensor system which includes at least one sensor for monitoring a physiological condition of the patient and a passive radio frequency transducer that receives sensor signals from the sensor or sensors, digitizes the sensor signals, and transmits the digitized signals out of the patient's body when subjected to an externally generated electromagnetically interrogation and energizing signal. The biosensor system described also includes a shunt, and as such it can be used for alleviating intracranial pressure monitored by the sensors of the biosensor.
Although this biosensor system presents a major advance over the above mentioned prior art devices and systems, it suffers from limitations inherent to the radio frequency transducer utilized thereby. Since this transducer requires the use of an antenna to receive and transmit signals, it posses limited reception and transmission capabilities due to the directional nature of such antennas. In addition, due to the high absorption of electromagnetic energy by human tissue, deeply embedded implants cannot be realized by this system and as a result, the intra body positioning of such a biosensor is limited to regions close to the skin which are accessible to electromagnetic signals, thus greatly limiting the effectiveness of such a system.
There is thus a widely recognized need for, and it would be highly advantageous to have, a biosensor system for monitoring and alleviating internal physiological conditions, such as intra-cranial pressure, devoid of the above limitations.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a biosensor which can be used for non-invasive monitoring of body parameters.
It is another object of the present invention to provide such a biosensor which does not require wiring or an integral power source.
It is yet another object of the present invention to provide a biosensor which is less sensitive to extracorporeal positional effect when energized as compared to prior art devices.
It is still another object of the present invention to provide a biosensor which is effectively operable from any depth within the body.
To realize and reduce
Doron Eyal
Penner Avi
Porat Yariv
Cadugan Joseph A.
G. E. Ehrlich Ltd.
Remon Medical Technologies Ltd.
Winakur Eric F.
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