METHOD AND APPARATUS FOR MINIMIZING THERMAL TRAUMA TO AN ORGAN DURING TISSUE ABLATION OF A DIFFERENT ORGAN
A method of minimizing thermal trauma during tissue ablation includes the steps of placing an ablation catheter at an ablation site on a first organ in a patient's body, providing energy to the ablation catheter to heat first organ tissue at the ablation site, providing microwave radiometry apparatus including a probe containing a microwave antenna and a radiometer responsive to the antenna output for producing a temperature signal corresponding to the thermal radiation picked up by the antenna and positioning the probe in a body passage of a second organ in the patient's body having a wall portion adjacent to the ablation site so that the microwave antenna is located at a measurement site opposite the ablation site. Using the radiometry apparatus, the temperature at depth in the second organ tissue at the measurement site is measured to provide a corresponding temperature signal, and the ablation catheter is controlled in response to the temperature signal to maintain the temperature of the second organ tissue below a predetermined value that does not result in thermal trauma to the second organ tissue. Apparatus for carrying out the method is also disclosed.
1 . A method of minimizing thermal trauma during tissue ablation including the steps of
placing an ablation catheter at an ablation site on a first organ in a patient's body;
providing energy to the ablation catheter to heat first organ tissue at the ablation site;
providing microwave radiometry apparatus including a probe containing a microwave antenna and a radiometer responsive to the antenna output for producing a temperature signal corresponding to the thermal radiation picked up by the antenna;
positioning the probe in a body passage of a second organ in the patient's body having a wall portion adjacent to the ablation site so that the microwave antenna is located at a measurement site opposite the ablation site;
using the radiometry apparatus, measuring the temperature at depth in the second organ tissue at the measurement site to provide a corresponding temperature signal, and
controlling the ablation catheter in response to the temperature signal to maintain the temperature of the second organ tissue below a predetermined value that does not result in thermal trauma to the second organ tissue.
2 . The method defined in claim 1 wherein the first organ is the heart and the second organ is the esophagus.
3 . The method defined in claim 1 wherein the first organ is the urethra and the second organ is the rectum.
4 . The method defined in claim 1 wherein the ablation catheter is controlled by varying the distance between the ablation catheter and the ablation site.
5 . The method defined in claim 1 wherein the ablation catheter includes a heating element and is controlled by regulating the current applied to the heating element.
6 . The method defined in claim 1 wherein the ablation catheter includes an RF antenna and is controlled by regulating the energy supplied to the RF antenna.
7 . The method defined in claim 1 and further including the step of cooling the probe so as to cool the second organ tissue while ablating the first organ tissue.
8 . The method defined in claim 7 wherein the cooling step is accomplished by flowing a fluid through the probe and adjusting the flow rate and/or temperature of the fluid in response to said temperature signal.
9 . Apparatus for minimizing thermal trauma during tissue ablation comprising
an ablation catheter for positioning at an ablation site on a first organ in a patient's body;
a device for providing energy to the ablation catheter to heat first organ tissue at the ablation site;
microwave radiometry apparatus including a probe containing a microwave antenna and a radiometer responsive to the antenna output for producing a temperature signal corresponding to the thermal radiation picked up by the antenna, said probe being positioned in a body passage of a second organ in the patient's body having a wall portion adjacent to the ablation site so that the microwave antenna is located at a measurement site opposite the ablation site, said radiometry apparatus being adapted to measure the temperature at depth in the second organ tissue at the measurement site to provide a corresponding temperature signal, and
a controller controlling the ablation catheter in response to the temperature signal to maintain said temperature of the second organ tissue below a predetermined value that does not result in thermal trauma to the second organ tissue.
10 . The apparatus defined in claim 9 wherein the first organ is the heart and the second organ is the esophagus.
11 . The apparatus defined in claim 9 wherein the first organ is the urethra and the second organ is the rectum.
12 . The apparatus defined in claim 9 wherein the ablation catheter includes a heating element and the controller includes a device for regulating the current applied to the heating element.
13 . The apparatus defined in claim 9 wherein the ablation catheter includes an RF antenna and the controller includes a device for regulating the energy supplied to the RF antenna.
14 . The apparatus defined in claim 9 and further including
apparatus for flowing a cooling fluid through the probe, and
a control device for controlling the flow rate and/or temperature of the cooling fluid so as to cool the second organ tissue while ablating the first organ tissue.
15 . The apparatus defined in claim 9 wherein the radiometry apparatus also includes a temperature indicator responsive to the temperature signal for indicating the temperature of the second organ tissue.