Tissue contact detection prior to and during an ablation procedure

Abstract

The present invention provides systems and methods for radiometrically measuring temperature and detecting tissue contact during ablation. An interface module includes a first input/output (I/O) port for receiving radiometer and thermocouple signals from an integrated catheter tip (ICT) that includes a radiometer; a second I/O port for receiving ablative energy from an electrosurgical generator; a temperature display; a patient relay; a computer-readable medium storing radiometer and thermocouple parameters and instructions for causing the processor to: calculate a temperature adjacent to the ICT based on the radiometer and thermocouple signals and the parameters; causing the temperature display to display the calculated temperature; closing the patient relay to pass ablative energy from the second to the first I/O port; determining whether the ICT is in contact with tissue based on the radiometer signal. An output device indicates whether the ICT is determined to be in contact with the tissue.

1 . A method of using an interface module with an ablation energy generator and an integrated catheter tip (ICT), the ICT including a radiometer, an ablative tip, and a thermocouple, the method of using the interface module comprising the steps of:
 (a) receiving at a first I/O port of the interface module a radiometer signal and a thermocouple signal from the ICT;   (b) receiving at a second I/O port of the interface module ablative energy from the ablation energy generator;   (c) calculating at the interface module a temperature adjacent to the ICT based on the radiometer signal, the thermocouple signal, and the operation parameters;   (d) determining at the interface module whether the ICT is in contact with tissue based on the radiometer signal;   (e) outputting with an output device an indication of the interface module's determination of whether the ICT is in contact with the tissue;   (f) displaying on a temperature display of the interface module the calculated temperature; and   (g) after step (e), passing ablative energy received on the second I/O port to the first I/O port by closing a patient relay of the ablation module.   
     
     
         2 . The method of  claim 1 , wherein step (d) comprises:
 (i) identifying a change in the radiometer signal;   (ii) comparing the change in the radiometer signal to a threshold value;   (iii) if the change is greater than the threshold value, transmitting a signal to the output device.   
     
     
         3 . The method of  claim 2 , wherein the output device comprises a visual display device configured to visually represent tissue contact responsive to the signal. 
     
     
         4 . The method of  claim 2 , wherein the output device comprises an audio device configured to audibly represent tissue contact responsive to the signal. 
     
     
         5 . The method of  claim 1 , further comprising the steps of:
 (h) storing at the interface module a safety cutoff temperature;   (i) at the interface module, comparing the calculated temperature to the safety cutoff temperature while the patient relay is closes; and   (j) if the calculated temperature exceeds the safety cutoff temperature, opening the patient relay and closing a load relay of the ablation module such that the load relay passes ablative energy received on the second I/O port to a dummy load of the ablation module.   
     
     
         6 . The method of  claim 1 , wherein the patient relay is maintained in a normally closed state and opened upon detection of an unsafe condition. 
     
     
         7 . The method of  claim 1 , further comprising the steps of:
 (h) initially calculating at the interface module a temperature adjacent to the ICT based on the thermocouple signal and the operation parameters but not the radiometer signal;   (i) displaying on the temperature display the initially calculated temperature; and   (j) if the temperature calculated in step (h) is in the range of 35° C. to 39° C., and if the second I/O port is receiving ablative energy from the ablation energy generator, then performing steps (c)-(g).   
     
     
         8 . The method of  claim 1 , further comprising the steps of:
 (h) receiving at a third I/O port of the ablation energy generator a signal from an indifferent electrode; and   (i) providing at a fourth I/O port the signal from the indifferent electrode to the ablation energy generator.   
     
     
         9 . The method of  claim 1 , wherein the ablative energy is selected from the group consisting of RF energy, microwave energy, cryoablation energy, and high frequency ultrasound energy. 
     
     
         10 . The method of  claim 1 , wherein the ablative energy is RF energy. 
     
     
         11 . A system for facilitating detection of contact with a target region of a subject, comprising:
 a processor,   wherein the processor is configured to receive a signal from a radiometer carried by a medical instrument and to provide an output indicative of contact between a portion of the medical instrument and a target region of a subject based upon, at least in part, properties determined from the signal received from the radiometer.   
     
     
         12 . The system of  claim 11 , wherein the processor is configured to regulate operation of an energy delivery member of the medical instrument based on the output indicative of the contact between the portion of the medical instrument and the target region of the subject. 
     
     
         13 . The system of  claim 11 , wherein the system is configured to provide to a user of the system confirmation of contact between the portion of the medical instrument and the target region of the subject. 
     
     
         14 . The system of  claim 11 , wherein the medical instrument comprises a catheter comprising an irrigation pump in fluid communication with a fluid passage of the catheter, wherein the irrigation pump is configured to selectively deliver irrigation fluid through the fluid passage of the catheter and at least one irrigation fluid port of the catheter in fluid communication with the fluid passage of the catheter during use. 
     
     
         15 . The system of  claim 11 , further comprising the medical instrument, wherein the medical instrument comprises an ablation catheter configured to deliver energy sufficient to ablate the target region upon being activated by an ablation energy source after the output indicative of contact is provided by the processor. 
     
     
         16 . The system of  claim 11 , further comprising the medical instrument, wherein the medical instrument comprises an energy delivery catheter configured to deliver energy to the target region upon being activated by an energy source after the output indicative of contact is provided by the processor.