Apparatus and method for delivery and monitoring of ablation therapy
Methods are provided for monitoring and controlling tissue ablation using RF energy delivered by an imaging ablation catheter under direct visualization, using the control and modulation of a set of ablation parameters based on direct optical imaging of the tissue surface via the imaging ablation catheter, where a set of optical image-derived parameters modulates the setting of a subset of Radio Frequency dosing parameters. The ablation dosing algorithms based on image-derived information can be implemented manually or in semi-automated or automated forms.
1 . A method of reducing outgassing during ablation of tissue, the method comprising:
determining a contact angle between a distal tip of an ablation catheter and the tissue while the ablation catheter is in contact with the tissue; and
reducing ablation power based on at least the contact angle exceeding a threshold value.
2 . The method of claim 1 , wherein determining the contact angle comprises:
receiving optical image data from a camera of the ablation catheter;
analyzing the optical image data to determine an extent of fluid ingress of a first fluid around a periphery of a field of view of the camera; and
referencing a plurality of predetermined relationships between known contact angles and measured fluid ingress to estimate the contact angle.
3 . The method of claim 2 , further comprising:
displacing the first fluid from the field of view with a second fluid; and
determining a flow rate of the second fluid into the field of view; wherein referencing the plurality of predetermined relationships between the known contact angles and measured fluid ingress includes selecting a predetermined relationship corresponding to the determined flow rate.
4 . The method of claim 1 , further comprising:
calculating a magnitude of energy delivered to the tissue based at least in part on the determined contact angle.
5 . The method of claim 4 , wherein the calculating the magnitude is further based on at least one of an irrigation fluid flow rate, a time of ablation, or a measured power from a radio frequency generator.
6 . The method of claim 5 , further comprising:
displaying the magnitude of energy delivered via a user interface.
7 . The method of claim 5 , further comprising:
displaying an indication that the magnitude of energy delivered has attained a pre-defined threshold energy value via a user interface.
8 . The method of claim 1 , wherein reducing the ablation power comprises:
displaying an indication of the determined contact angle on a user interface; and
receiving an instruction from a user to reduce the ablation power.
9 . The method of claim 1 , further comprising:
providing a warning to a user based on the determined contact angle exceeding the threshold value, wherein the warning comprises at least one of a visual warning on a user interface or an audible warning.
10 . The method of claim 1 , wherein reducing the ablation power is performed automatically by a control system associated with the ablation catheter in response to the control system detecting an unsuitable contact angle based on the determined contact angle and the threshold value.
11 . The method of claim 1 , wherein the contact angle is measured with respect to a surface normal of the tissue.
12 . The method of claim 1 , wherein reducing ablation power is further based on a blanching parameter.
13 . The method of claim 12 , wherein the blanching parameter is an ablation time to attain a predetermined extent of change in tissue color within a portion of a field of view.
14 . A method of reducing outgassing during ablation of tissue, the method comprising:
identifying a plurality of optical markers in a field of view of a camera;
fitting a shape to intersect the plurality of optical markers;
determining an eccentricity of the shape;
determining a contact angle between a distal tip of an ablation catheter and the tissue while the ablation catheter is in contact with the tissue by referencing predetermined eccentricity values associated with known contact angles; and
reducing ablation power based on at least the contact angle.
15 . The method of claim 14 , wherein reducing the ablation power is performed automatically by a control system associated with the ablation catheter in response to the control system detecting an unsuitable contact angle based on the determined contact angle and a threshold value.
16 . The method of claim 14 , further comprising:
calculating a magnitude of energy delivered to the tissue based at least in part on the determined contact angle.
17 . A method of reducing outgassing during ablation of tissue, the method comprising:
measuring an impedance associated with each of a plurality of electrodes of an ablation catheter;
determining a variation between the measured impedance of at least two of the electrodes;
determining a contact angle between a distal tip of an ablation catheter and the tissue while the ablation catheter is in contact with the tissue by referencing a plurality of predetermined relationships between known contact angles and measured impedance variations; and
reducing ablation power based on at least the contact angle.
18 . The method of claim 17 , wherein reducing the ablation power is performed automatically by a control system associated with the ablation catheter in response to the control system detecting an unsuitable contact angle based on the determined contact angle and a threshold value.
19 . The method of claim 17 , further comprising:
calculating a magnitude of energy delivered to the tissue based at least in part on the determined contact angle.
20 . The method of claim 17 , wherein reducing ablation power is further based on a blanching parameter.