1. Technical Field
The present disclosure relates to systems, devices and methods for performing a medical procedure. More particularly, the present disclosure relates to heat-distribution indicators and thermal zone indicators suitable for use during thermal ablation, electrosurgical systems including the same, and methods of directing energy to tissue using the same.
2. Discussion of Related Art
Electrosurgery is the application of electricity and/or electromagnetic energy to cut, dissect, ablate, coagulate, cauterize, seal or otherwise treat biological tissue during a surgical procedure. When electrical energy and/or electromagnetic energy is introduced to tissue, the energy-tissue interaction produces excitation of molecules, creating molecular motion that results in the generation of heat. Electrosurgery is typically performed using a handpiece including a surgical instrument (e.g., end effector, ablation probe, or electrode) adapted to transmit energy to a tissue site during electrosurgical procedures, an electrosurgical generator operable to output energy, and a cable assembly operatively connecting the surgical instrument to the generator.
Treatment of certain diseases requires the destruction of malignant tissue growths, e.g., tumors. Electromagnetic radiation can be used to heat and destroy tumor cells. Treatment may involve inserting ablation probes into tissues where cancerous tumors have been identified. Once the probes are positioned, electromagnetic energy is passed through the probes into surrounding tissue. The application of ultrasound imaging is one of the cost-effective methods often used for tumor localization and ablation device placement.
There are a number of different types of apparatus that can be used to perform ablation procedures. Typically, apparatus for use in ablation procedures include a power generating source, e.g., a microwave or radio frequency (RF) electrosurgical generator, that functions as an energy source, and a surgical instrument (e.g., microwave ablation probe having an antenna assembly) for directing the energy to the target tissue. The generator and surgical instrument are typically operatively coupled by a cable assembly having a plurality of conductors for transmitting energy from the generator to the instrument, and for communicating control, feedback and identification signals between the instrument and the generator.
Using electrosurgical instruments to ablate, seal, cauterize, coagulate, and/or desiccate tissue may result in some degree of thermal injury to surrounding tissue. For example, electrosurgical desiccation may result in undesirable tissue damage due to thermal effects, wherein otherwise healthy tissue surrounding the tissue to which the electrosurgical energy is being applied is thermally damaged by an effect known in the art as “thermal spread”. During the occurrence of thermal spread, excess heat from the operative site can be directly conducted to the adjacent tissue and/or the release of steam from the tissue being treated at the operative site can result in damage to the surrounding tissue. The duration of the activation of the generator is directly related to the heat produced in the tissue. The greater the heat produced, the more the potential for thermal spread to adjacent tissues.
Currently available systems and methods for controlling an electrosurgical generator during electrosurgery may include a clinician monitoring and adjusting, as necessary, the amount of energy delivered to a tissue site through current, voltage, impedance, and/or power measurements such that an appropriate tissue effect can be achieved at the tissue site with minimal collateral damage resulting to adjacent tissue. These systems and/or methods typically require a clinician to translate the desired tissue effect to a power setting on an electrosurgical generator and, if necessary, adjust the power setting to compensate for tissue transformations (e.g., desiccation of tissue) associated with the electrosurgical procedure such that a desired tissue effect may be achieved.
As can be appreciated, limiting the possibility of thermal spread or the like during an electrosurgical procedure reduces the likelihood of unintentional and/or undesirable collateral damage to surrounding tissue structures which may be adjacent to an intended treatment site. Controlling and/or monitoring the depth of thermal spread during an electrosurgical procedure may aid a clinician in assessing tissue modification and/or transformation during the electrosurgical procedure.
Medical imaging has become a significant component in the clinical setting and in basic physiology and biology research, e.g., due to enhanced spatial resolution, accuracy and contrast mechanisms that have been made widely available. Medical imaging now incorporates a wide variety of modalities that noninvasively capture the structure and function of the human body. Such images are acquired and used in many different ways including medical images for diagnosis, staging and therapeutic management of malignant disease.
Because of their anatomic detail, computed tomography (CT) and magnetic resonance imaging (MRI) are suitable for, among other things, evaluating the proximity of tumors to local structures. CT and MRI scans produce two-dimensional (2-D) axial images, or slices, of the body that may be viewed sequentially by radiologists who visualize or extrapolate from these views actual three-dimensional (3-D) anatomy.
Measurements and quantitative analysis for parameters such as area, perimeter, volume and length may be obtained when object boundaries are defined. A boundary in an image is a contour that represents the change from one object or surface to another. Image segmentation involves finding salient regions and their boundaries. A number of image segmentation methods have been developed using fully automatic or semi-automatic approaches for medical imaging and other applications. Medical image segmentation refers to the delineation of anatomical structures and other regions of interest in medical images for assisting clinicians in evaluating medical imagery or in recognizing abnormal findings in a medical image. Structures of interest may include organs or parts thereof, such as cardiac ventricles or kidneys, abnormalities such as tumors and cysts, as well as other structures such as bones and vessels.
Medical image processing, analysis and visualization play an increasingly significant role in disease diagnosis and monitoring as well as, among other things, surgical planning and monitoring of therapeutic procedures. Unfortunately, tissue heating and thermal damage does not create adequate contrast in ultrasound images to allow determination of the size of an ablated zone and assessment of the margins of ablated tissue.