Surgery – Instruments – Electrical application
Reexamination Certificate
2000-06-30
2003-01-28
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S032000, C606S034000, C600S549000
Reexamination Certificate
active
06511478
ABSTRACT:
FIELD OF THE INVENTION
The present inventions relate to medical probes, and more particularly, catheters and surgical probes that possess temperature sensing functionality.
BACKGROUND
Currently, medical probes, such as catheters and surgical probes, are used to treat heart abnormalities, such as atrial fibrillation and other cardiac arrythmias. In a typical procedure, a medical probe employs one or more ablation elements and one or more corresponding temperature sensors in order to therapeutically ablate tissue within the heart in a controlled manner. Temperature sensors currently used in medical probes, such as thermistors or thermocouples, all require separate analog signal conditioning circuitry for each sensor, although analog to digital (A/D) conversion circuitry may be multiplexed.
Thermistors respond to changes in temperature with a well-defined change in resistance. Analog conditioning circuitry, which is used to interface the thermistors with the A/D converter, measures the resistance of the thermistors, and thus, the temperature of the adjacent tissue, by separately measuring the voltage across each thermistor in response to a constant current. By comparison, thermocouples contain a junction of dissimilar metals that generate a small voltage proportional to temperature, due to the Peltier effect. Analog conditioning circuitry is connected to each thermocouple to amplify the voltage output thereby and to reduce any noise associated with such voltage.
Further, to support such multiple sensor probes, current technology requires a large number of wires to be contained within the small and limited space of the probe body, thereby rendering manufacture of such medical probes increasingly difficult. This constraint is even more pronounced in catheters, the diameters of which must be minimized to allow the catheters to be introduced into the heart through the vasculature of a patient. The increased number of wires in connectors and cabling also makes the manufacture of accessory cables used to support multiple sensor medical probes more difficult and expensive. Moreover, connector reliability is reduced due to the large number of connections required to implement discrete wires for each temperature sensor.
Regardless of the type of sensor utilized, the analog conditioning circuitry must be duplicated with the currently available designs for each sensor. For example,
FIG. 29
illustrates a prior art system, which includes a power generator
66
that is coupled to a medical probe
50
via a cable
55
. A standard generator interface
62
is used to interface the proximal end of the cable
55
to the circuitry within the generator
66
, and a standard probe interface
62
is used to interface the distal end of the cable
55
to the circuitry within the medical probe
50
. The power generator
66
includes a power source
51
(in this case an RF oscillator), which provides RF power to ablation energy electrodes
53
located at the distal end of the medical probe
50
. The power generator
66
further includes a temperature controller
54
(in this case, a microprocessor), which communicates with analog temperature sensors
52
located at the distal end of the medical probe
50
via parallel sets of analog to digital converters
56
and signal conditioners
60
. As illustrated, a separate analog to digital converter
56
and signal conditioners
60
is required for each temperature sensor
52
.
FIG. 30
illustrates another prior art system, which includes a power generator
68
that is coupled to the medical probe
50
via the cable
55
. The power generator
68
differs from the power generator
66
shown in
FIG. 29
in that the power generator
66
uses a single analog to digital converter with multiplexing capability
58
to process signals from each sensor
52
.
The additional circuitry required for each sensor
52
generally involves expensive, low noise integrated circuits. Time consuming calibration of each input during manufacturing is also typically required. As a result, the amount of circuit duplication increases by the number of sensors that must be read, thereby making systems with more than a few temperature sensors expensive and impractical. Also, the ablation power generators that support these medical probes are necessarily designed in a non-optimal manner. For a multiple sensor medical probe, the ablation power generators must be designed to accommodate the number of expected sensors by providing separate analog inputs for each sensor, as illustrated in
FIGS. 29 and 30
. Therefore, when designing such power generators, a tradeoff must be made between the excessive costs of providing extra sensor inputs to accommodate future requirements and the risk of premature obsolescence of a power generator that provides too few sensor inputs.
Moreover, the sensors are typically located from between ten to fifty feet away from the ablation power generators, being connected through fine-gauge wire in the medical probe itself, and through one or more cables with intermediate connections. The analog voltages which represent the temperature are typically quite small, particularly with thermocouples, where the dynamic range in the area of interest is usually only in the hundreds of microvolts. These analog voltages are susceptible to electrical noise induced by ablation power and sources of electromagnetic interference in the environment, some of which may be of a high enough amplitude or low enough frequency range that filtering may not be practical.
Consequently, there is a need to provide a medical probe system that contains a reduced number of electrical paths, or temperature sensor wires, as well as a medical probe system that outputs temperature sensor signals that exhibit little or no noise.
SUMMARY OF THE INVENTION
The present inventions are directed to medical probe systems, medical probes, ablation power generators, and temperature sensor subassemblies that are configured to reduce the number of wires used to conduct data output from a multitude of temperature sensors. The present inventions are also directed to medical probes that utilize one or more digital temperature sensors, resulting in a temperature sensing circuit that is less susceptible to ambient noise.
In accordance with a first aspect of the present inventions, a medical probe comprises an elongate member having a proximal end and a distal end. The medical probe can be any probe (e.g., a catheter or surgical probe) that can be placed within the body of a patient. The medical probe further includes a plurality of temperature sensors that are carried by the distal end of the elongate member. Each of the temperature sensors can be digital, in which case, it may conveniently be embodied in an integrated circuit that is configured for outputting digital data representative of a measured temperature. Alternatively, each of the temperature sensors can be analog, in which case, it may be embodied in a thermistor, thermocouple, resistance temperature detector (RTD), or other analog device, that is configured for outputting analog data representative of a measured temperature.
The medical probe further includes a common electrical bus carried by the elongate member. The common electrical bus defines two or more electrical paths, each of which is coupled to the plurality of temperature sensors. By way of nonlimiting example, the two or more electrical paths can comprise three electrical paths represented by respective data, ground, and power lines. Alternatively, power can be parasitically obtained from the data line, in which case, only two electrical paths are needed. The common electrical bus can be embodied in any suitable circuit, e.g., bifilar wire, trifilar wire, flex circuit, or flex circuit/wire hybrid. Each electrical path can be formed of a single wire or trace to which the temperature sensors are connected, or alternatively, can be formed of several wires or traces connected between the temperature sensors in a daisy chaining fashion. In the preferred embodiment, the medical probe includes a handle mo
Burnside Robert R.
Dueiri David
O'Brien Dennis M.
Thompson Russell B.
Bingham & McCutchen LLP
Peffley Michael
Scimed Life Systems Inc.
Vrettakos Pete
LandOfFree
Medical probe with reduced number of temperature sensor wires does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Medical probe with reduced number of temperature sensor wires, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Medical probe with reduced number of temperature sensor wires will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3022465