METHODS AND APPARATUSES FOR PERFORMING AND MONITORING THERMAL ABLATION

• US 20100185087A1
• Filed: 10/09/2009
• Published: 07/22/2010
• Est. Priority Date: 08/04/2006
• Status: Active Grant

• Current Assignee: Fischer Acquisition LLC
• Original Assignee: Ablatx Incorporated
• Inventors: Gustafson, David E., Nields, Morgan W.
• Granted Patent: US 8,556,888 B2
• Time in Patent Office: Days
• US Class Current: 600/439
• CPC Class Codes: A61B 18/14 Probes or electrodes therefor
• CPC Class Codes: A61B 18/18 by applying electromagnetic radiation, e.g. microwaves radiation therapy A61N5/00
• CPC Class Codes: A61B 18/1815 using microwaves
• CPC Class Codes: A61B 18/20 using laser
• CPC Class Codes: A61B 2017/00084 Temperature
• CPC Class Codes: A61B 2034/105 Modelling of the patient, e.g. for ligaments or bones
• CPC Class Codes: A61B 2090/363 Use of fiducial points
• CPC Class Codes: A61B 2090/376 using X-rays, e.g. fluoroscopy
• CPC Class Codes: A61B 6/027 characterised by the use of a particular data acquisition trajectory, e.g. helical or spiral
• CPC Class Codes: A61B 6/035 Mechanical aspects of CT
• CPC Class Codes: A61B 6/0407 Supports, e.g. tables or beds, for the body or parts of the body
• CPC Class Codes: A61B 6/0492 using markers or indicia for aiding patient positioning
• CPC Class Codes: A61B 6/12 Arrangements for detecting or locating foreign bodies
• CPC Class Codes: A61B 6/466 adapted to display 3D data
• CPC Class Codes: A61N 7/02 Localised ultrasound hyperthermia hyperthermia in general A61F7/00

Abstract

A thermal ablation system is operable to perform thermal ablation using an x-ray system to measure temperature changes throughout a volume of interest in a patient. Image data sets captured by the x-ray system during a thermal ablation procedure provide temperature change information for the volume being subjected to the thermal ablation. Intermediate image data sets captured during the thermal ablation procedure may be fed into a system controller, which may modify or update a thermal ablation plan to achieve volume coagulation necrosis targets. The thermal ablation may be delivered by a variety of ablation modes including radiofrequency ablation, microwave therapy, high intensity focused ultrasound, laser ablation, and other interstitial heat delivery methods. Methods of performing thermal ablation using x-ray system temperature measurements as a feedback source are also provided. Methods of assessing the post-ablation status of the patient and performance of the system are also provided.

Claims

1. An apparatus for performing thermal ablation within a Volume Of Interest (VOI) in a patient comprising:

at least one thermal ablation applicator operable to create temperature changes within a VOI;

an x-ray system operable to measure temperature changes across said VOI in a patient, wherein said x-ray system is operable to produce x-ray beams at a plurality of different kV levels; and

a controller operable to compare measured temperature changes across said VOI measured by said x-ray system to expected temperature changes in a thermal ablation plan, wherein said plan comprises expected temperature changes at substantially each spatial location within said VOI as a function of time during said thermal ablation.

2. The apparatus of claim 1, wherein said x-ray system is an x-ray CT scanner.

3. The apparatus of claim 2, wherein said x-ray CT scanner is an x-ray C-arm CT scanner operable to produce a conical x-ray beam and said x-ray C-arm CT scanner is operable to detect said conical x-ray beam with a two-dimensional x-ray detector array.

4. The apparatus of claim 1, wherein said controller is further operable to adjust at least one characteristic of said at least one thermal ablation applicator in closed-loop control based on said comparison, wherein said at least one characteristic of said at least one thermal ablation applicator is selected from a group consisting of:

applicator power, applicator position, applicator type, and applicator quantity.

5. The apparatus of claim 1, further comprising an ultrasound imaging device operable to generate images of said VOI in said patient, wherein said ultrasound imaging device is capable of at least one of ARFI imaging and elastography imaging.

6. A method of performing a thermal ablation procedure within a Volume Of Interest (VOI) in a patient comprising the steps of:

(a) capturing a baseline digital image with an x-ray system of a VOI in a patient, wherein said baseline digital image is comprised of a first set of detected image signal data corresponding with an array of spatial locations substantially throughout said VOI, wherein said capturing a baseline digital image step comprises producing x-ray beams at first and second kV levels, wherein said first set of detected image signal data comprises data collected at said first and second kV levels;

(b) performing thermal ablation on at least a first sub-volume of said VOI according to at least a portion of a first thermal ablation plan, wherein said plan comprises expected temperature changes at substantially each spatial location within said array as a function of time during said thermal ablation;

(c) capturing a first temperature differential digital image with said x-ray system of said VOI, wherein said first temperature differential digital image is comprised of a second set of detected image signal data substantially corresponding with said array of spatial locations, wherein said capturing a first temperature differential digital image step comprises producing x-ray beams at first and second kV levels, wherein said second set of detected image signal data comprises data collected at said first and second kV levels;

(d) registering said first temperature differential digital image to said baseline digital image;

(e) inferring, based at least in part on said baseline digital image and said first temperature differential digital image, an amount of temperature change at substantially each spatial location within said array of spatial locations; and

(f) comparing said inferred temperature changes at substantially each spatial location within said array to expected temperature changes at substantially each spatial location within said array from said first thermal ablation plan.

7. A method as set forth in claim 6, wherein said capturing of said baseline digital image comprises:

illuminating said VOI with x-rays;

detecting a plurality of portions of said x-rays that passed through said VOI; and

at least partially generating said baseline digital image based on said detected x-rays, wherein said illuminating and said detecting are performed at a plurality of different kV levels.

8. A method as set forth in claim 6, wherein said inferring step is performed at each of said first and second kV levels to produce kV-level-specific inferred temperature changes at substantially each spatial location within said array.

9. A method as set forth in claim 8, wherein said inferring step further comprises combining said kV-level-specific inferred temperature changes at substantially each spatial location within said array to generate said inferred temperature changes at substantially each spatial location within said array.

10. A method as set forth in claim 6, wherein said inferring step is based on said kV-level-specific inferred temperature changes at said first kV level in a first portion of said spatial locations within said array, wherein said inferring step is based on said kV-level-specific inferred temperature changes at said second kV level in a second portion of said spatial locations within said array, wherein said first portion is different than said second portion.

11. A method as set forth in claim 6, further comprising:

accessing a preliminary thermal ablation plan, wherein said preliminary thermal ablation plan comprises expected temperature changes at substantially each spatial location within said array as a function of time during said thermal ablation; and

comparing said baseline digital image to said preliminary thermal ablation plan.

12. A method as set forth in claim 6, further comprising calibrating said first temperature differential digital image, said calibration comprising:

measuring temperature of at least a first spatial location within said VOI; and

correlating said measured temperature at said at least first spatial location within said VOI to said first temperature differential digital image at said at least first spatial location within said VOI.

13. A method as set forth in claim 6, further comprising calculating a predicted coagulation necrosis volume based, at least in part, on said inferred amount of temperature change at substantially each spatial location within said array of spatial locations.

14. A method of performing a thermal ablation procedure within a Volume Of Interest (VOI) in a patient comprising the steps of:

(a) capturing a baseline digital image of a VOI in a patient, wherein said baseline digital image is comprised of a first set of detected image signal data corresponding with an array of spatial locations substantially throughout said VOI;

(b) performing thermal ablation on at least a first sub-volume of said VOI according to at least a portion of a first thermal ablation plan, wherein said first thermal ablation plan comprises expected temperature changes at substantially each spatial location within said array as a function of time during said thermal ablation procedure;

(c) capturing a first temperature differential digital image of said VOI, wherein said first temperature differential digital image is comprised of a second set of detected image signal data substantially corresponding with said array of spatial locations;

(d) registering said first temperature differential digital image to said baseline digital image;

(e) inferring, based at least in part on said baseline digital image and said first temperature differential digital image, an amount of temperature change at substantially each spatial location within said array of spatial locations; and

(f) comparing said inferred temperature changes at substantially each spatial location within said array to expected temperature changes at substantially each spatial location within said array from said first thermal ablation plan,

wherein at least one of said capturing of said baseline digital image and said capturing of said first temperature differential digital image further comprises the steps of;

(g) positioning an x-ray CT scanner so that said VOI is within a field of view of said scanner and x-rays emanating from said scanner intersect said VOI at a first orientation;

(h) illuminating, with an x-ray source of said x-ray CT scanner, said VOI with a first beam of x-rays emanating from said scanner at a first time;

(i) detecting, with an x-ray detector of said x-ray CT scanner, a plurality of portions of said first beam of x-rays that passed through said VOI during said illuminating at said first time, wherein said illuminating and said detecting are performed at a plurality of different kV levels; and

(j) generating a first x-ray image signal from said plurality of portions of x-rays of said detected first beam, said first x-ray image signal comprising x-ray image values corresponding with an array of spatial locations throughout said VOI.

15. A method as set forth in claim 14, wherein said at least one of said capturing of said baseline digital image and said capturing of said first temperature differential digital image further comprises the steps of:

(k) repositioning said scanner so that said VOI remains within said field of view of said scanner and x-rays emanating from said scanner will intersect said VOI at a second orientation;

(l) illuminating said VOI with a second beam of x-rays emanating from said scanner at a second time;

(m) detecting, with said x-ray detector, a plurality of portions of said second beam of x-rays that passed through said VOI during said illuminating at said second time, wherein said illuminating step (l) and said detecting step (m) are performed at a plurality of different kV levels;

(n) generating a second x-ray image signal from said plurality of portions of x-rays of said detected second beam, said second x-ray image signal comprising x-ray image values corresponding with said array of spatial locations throughout said VOI;

(o) repeating steps (k) through (n) to generate additional x-ray image signals from additional detected x-rays that passed through said VOI at unique orientations until a sufficient number of x-ray image signals have been generated to enable a three-dimensional image data set of a predetermined resolution to be created; and

(p) generating said three-dimensional image data set from said generated image signals.

16. A method as set forth in claim 15, further comprising the steps of:

generating a three-dimensional resultant image data set comprising thermal information in relation to each of said spatial locations throughout said VOI based upon a comparison of two of said generated three-dimensional image data sets, wherein said thermal information is indicative of relative magnitudes of temperature changes between said two three-dimensional image data sets for each of said spatial locations throughout said VOI; and

spatially displaying said thermal information for said array of spatial locations throughout said VOI, wherein said relative magnitudes of temperature changes throughout said VOI are visually discernable.

17. A method of inferring thermal changes within a Volume Of Interest (VOI) in a patient occurring during a thermal ablation procedure comprising the steps of:

capturing a baseline digital image with an x-ray system of a VOI in a patient, wherein said baseline digital image is comprised of detected image signal data corresponding with a baseline array of spatial locations substantially throughout said VOI, wherein each spatial location of said baseline array is a voxel representing a volume of at most 1 cm3;

performing thermal ablation on at least a first sub-volume of said VOI;

capturing a first temperature differential digital image with said x-ray system of said VOI, wherein said first temperature differential digital image is comprised of detected image signal data corresponding with a first temperature differential array of spatial locations substantially throughout said VOI, wherein each spatial location of said first temperature differential array is a voxel representing a volume of at most 1 cm3;

registering said first temperature differential digital image to said baseline digital image;

calculating image signal data changes for substantially each spatial location within said first temperature differential array; and

inferring, based at least in part on said calculated image signal data changes, temperature changes at substantially each spatial location within said first temperature differential array from said image signal data changes;

positioning a patient on a bed prior to said capturing said baseline digital image; and

maintaining said position of said patient relative to said bed during and between said capturing of said baseline digital image, said performing, said capturing of said first temperature differential digital image, said registering, said calculating, and said inferring steps,

wherein said patient and bed are not moved substantially more than a maximum lineal dimension of said VOI during and between said capturing of said baseline digital image, said performing, said capturing of said first temperature differential digital image, said registering, said calculating, and said inferring steps, wherein said capturing a baseline digital image step comprises producing x-ray beams at a plurality of different kV levels, wherein said capturing a first temperature differential digital image step comprises producing x-ray beams at said plurality of different kV levels, wherein said inferring step is performed at each of said plurality of different kV levels to produce kV-level-specific inferred temperature changes, wherein said inferring step further comprises combining each of said kV-level-specific inferred temperature changes.

18. A method as set forth in claim 17, wherein said capturing said baseline digital image and said capturing said first temperature differential digital image are performed at least in part by an x-ray CT scanner.

19. A method as set forth in claim 18, wherein said capturing said baseline digital image and said capturing said first temperature differential digital image are performed at least in part by an x-ray C-arm CBCT scanner.

20. A method as set forth in claim 17, further comprising displaying an image of at least a portion of said VOI in which said inferred temperature changes are visually discernable.