1. Field of the Invention
The present invention relates to ultrasound imaging, and more particularly, to robotic 5-dimensional (5D) ultrasound imaging.
2. Discussion of the Related Art
Ultrasound is widely used in the medical community for intervention therapy. Examples include thermal ablation, external beam radiation therapy (EBRT), Brachy therapy, and needle insertion procedures, including biopsy procedures.
As stated, thermal ablation is but one procedure for which ultrasound is commonly used. Primary and metastatic liver cancer represents a significant source of morbidity and mortality in the United States, as well as worldwide. The medical community has focused on such techniques as thermal ablation, and in particular, radiofrequency ablation (RFA), to treat this and other similar diseases. Thermal ablation typically utilizes images to guide the placement of the ablation probe to or within the target area (e.g., a lesion or tumor) of the liver parenchyma. Heat created around the electrode, which is generally located at the tip of the ablation probe, is conducted into the target area tissue, causing coagulative necrosis at a temperature between 50° C. and 100° C.
There are several problems associated with conventional thermal ablation techniques. First and foremost is the ability to effectively utilize the imagery to precisely control the ablation probe during the ablation procedure. To some extent, this problem has been addressed by the development and use of 3D ultrasound imaging systems. While ultrasound is commonly used for target imaging, in general, and ablation monitoring, problems still exist even with these systems, as they do not provide adequate imagery and, as a result, they cannot effectively identify, segment, monitor or track target tissue, nor do they facilitate planning or control prior to and during the ablation process.
One reason conventional robotic 3D ultrasound systems are inadequate is that ultrasound cannot detect all lesions and tumors. Lesions and tumors are may be categorized as either hyperechoic (i.e., appear brighter than the surrounding tissue in an image), hypoechoic (i.e., appear darker than the surrounding tissue in an image), or isoechoic (i.e., have the same intensity as the surrounding tissue in an image). Ultrasound cannot visualize lesions or tumors that are isoechoic. Thus, conventional 3D ultrasound systems cannot effectively identify, segment, monitor or track target tissue, or facilitate planning and control prior to and during an ablation process where the target tissue is isoechoic.
Another reason conventional 3D ultrasound based systems are not always effective is that such systems do not necessarily provide adequate imaging in a noisy environment. As one skilled in the art will appreciate, the operation of an ablation probe generates a significant amount of noise which otherwise interferes with the ultrasound signal, and the ability of the system to generate accurate imagery.
Thermal ablation is, as stated, only one example of a medical procedure for which ultrasound is used to facilitate the procedure. Given the important of ablation therapy, as well as other medical procedures that utilize ultrasound, it is clear there is a tremendous need to enhance the capabilities of imaging systems to overcome the problems described above.
The present invention involves robotic 5D ultrasound imaging to overcome the various problems associated with conventional 3D ultrasound systems. In general, the present invention achieves this by integrating 3D ultrasound imagery with strain (i.e., elasticity) imagery over time, where strain imagery and time represent a fourth and a fifth degree of freedom, respectively, hence, 5D ultrasound imagery. In addition, the present invention utilizes a robotic end-effector to provide different compression profiles and to provide precise synchronization between the ultrasound acquisition and strain estimation. Still further, the present invention integrates this 5D information and projects it into a 4D visualization over time.
Elasticity imaging is generally known, where elasticity imaging provides a remote and non-invasive representation based on the mechanical properties of the target tissue. These elastic or mechanical properties associated with the target tissue cannot be measured directly. Thus, a mechanical disturbance is applied, and the resulting response is evaluated. One may categorize elasticity imaging into static (i.e., strain based) imaging, dynamic (i.e., wave based) imaging, and mechanical (i.e., stress based) imaging. The strain based approach involves imaging the internal motion if the tissue under static deformation. In contrast, the dynamic approach involves imaging shear wave propagation, and the mechanical approach involves measuring surface stress distribution. Each of these approaches further involve 1) capturing data during externally or internally induced tissue motion or deformation, 2) evaluating tissue response (displacement, strain, or stress), and if needed 3) reconstructing the elastic modulus based on the theory of elasticity.
In accordance with a preferred embodiment of the present invention, the strain based imaging approach is employed. However, one of skill in the art will understand that the use of any one of the other elastic imaging approaches is within the scope and spirit of the present invention.
One advantage of the present invention is that it provides an adequate visualization of the target area, even where the target tissue is isoechoic.
Another advantage of the present invention is that it provides for the accurate identification and segmentation of the target area, such that the boundaries and/or contours of the lesion or tumor can more accurately be distinguished from the surrounding tissue, thereby providing more accurate information based on which the system can more accurately and more effectively plan, monitor, track and control the treatment procedure.
Yet another advantage of the present invention is it provides for different synchronization scenarios to assist in generating strain images at the same rate it acquires the ultrasound image data.
In accordance with a first aspect of the present invention, the aforementioned and other advantages are achieved by a computer integrated surgical system. The system comprises an ultrasound imaging system and a workstation. The workstation, in turn, is configured for receiving ultrasound signals from the ultrasound imaging system, and it includes an elasticity imaging module configured for deriving elasticity related parameters relating to target tissue, an ultrasound module configured for providing ultrasound image data reflecting the anatomical structure of the target tissue, and a volume rendering module configured for integrating the strain distribution information and the ultrasound image data and generating a visualization of the target tissue based on both the strain distribution data and the ultrasound image data.
In accordance with a second aspect of the present invention, the aforementioned and other advantages are achieved by a workstation for use in a computer integrated surgical system. The workstation comprises a strain imaging module configured for deriving strain distribution information relating to target tissue, an ultrasound module configured for providing ultrasound image data reflecting the anatomical structure of the target tissue, and a volume rendering module configured for integrating the strain distribution information and the ultrasound image data and generating a visualization of the target tissue based on both the strain distribution data and the ultrasound image data.
In accordance with a third aspect of the present invention, the aforementioned and other advantages are achieved by a method for rendering an ultrasonic image. The method involves acquiring ultrasound image data of a target tissue and acquiring strain image data of the target tissue. Then, the ultrasound image data and strain image data are integrated and a visualization of the target tissue based on both the ultrasound image data and the strain image data is generated.
In accordance with a fourth aspect of the present invention, the aforementioned and other advantages are achieved by a method of generating segmentation data using ultrasound image data in a medical procedure. The method involves acquiring ultrasound image data of a target tissue, acquiring strain image data of the target tissue, generating a model from the strain image, utilizing the model as an input to a model based segmentation process, and generating segmentation data associated with the target tissue based on the strain image data.
In accordance with a fourth aspect of the present invention, the aforementioned and other advantages are achieved by a method of registering online ultrasound data to preoperative non-ultrasound. The method involves combining tissue/organ boundaries from 3D ultrasound image data, augmenting elasticity to generate a pseudo, non-ultrasound data that can be used to register with preoperative, non-ultrasound data, utilizing a strain component as a landmark to automate a first initial matching registration, utilizing anatomy data to fine-tune the registration, and incorporating anatomy information and elasticity in a registration metric.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as set forth in the claims.
The accompanying drawings together with the description serve to explain the principles of the present invention. In the drawings:
The focus of the present invention is a robotic 5D ultrasound system and method for use in the field of Image Guided Therapy (IGT) and, more generally, Computer Integrated Surgery (CIS). The robotic 5D ultrasound system and method, in accordance with exemplary embodiments of the present invention enhance “surgical CAD-CAM-TQM” systems by integrating over time 3D ultrasonic image data with strain (i.e., elasticity) image data.
“Surgical CAD” is analogous to computer-aided design (i.e., CAD) in manufacturing systems, wherein the CAD phase involves the design and/or planning of the intended treatment using an IGT system. In general, prior to such medical procedures, medical images, anatomical atlases and other information are combined for the purpose of generating a model of an individual patient. The model is then used for planning the treatment or intervention procedure. The present invention, however, offers new capabilities with respect to the planning based on more accurate information as a result of integrating elasticity and anatomical variation information simultaneously. More specifically, the present invention uses both elasticity (i.e., strain) image data and ultrasound image data to more accurately identifying the targeted lesions and surrounding critical structures and to more effectively plan optimized therapy patterns (CAD).
The following are examples illustrating some of the ways in which the robotic 5D ultrasound system and method of the present invention facilitate surgical CAD process.
“Surgical CAM” is analogous to computer-aided manufacturing. In the “surgical CAM” phase, data from the preoperative planning phase (i.e., the images, models, plan geometry, etc.) is made available to the attending technician or physician, for example, in the operating room. Real time image and other sensor data are used to update the information during the course of the procedure. The actual surgical procedure is performed by the surgeon with the assistance of the CIS system. In this surgical CAM phase, the 5D ultrasound system and method, in accordance with the present invention, enhance surgical CAD-CAM-TQM” systems in the following ways.
“Surgical TQM” refers to “total quality management,” and it reflects the important role that the a CIS system can play in reducing surgical errors and promoting better, more consistent outcomes. It is always a crucial goal to ensure that the planned therapeutic intervention has in fact been completely and successfully performed before the patient leaves the operating room. In this phase, the assessment process must be integrated with planning and therapy delivery systems to permit interactive re-planning based on this feedback (TQM). The present invention facilitates the TQM phase in a number of ways for a wide variety of clinical/surgical applications.
First, the 5D ultrasound workstation 120 includes a video capture board 125. The video capture board 125 receives and processes the B-mode 2D ultrasound video data generated by the ultrasound sensor 105. The video capture board 125 is a standard piece of equipment that may be purchased “of-the-shelf.” An example of a suitable video capture board is the MeteorII video processing board made by Matrox Inc. Alternatively, the video capture board 125 could be replaced by a digital video processing board if the ultrasound sensor 105 supported digital link (e.g., DV firewire, optical link etc. . . . ). In another alternative, the B-mode video data can be derived from the raw RF data.
Second, the workstation 120 includes an RF capture board 130. The RF capture board 130 receives and digitizes the raw RF data that corresponds to the 2D ultrasound data generated by the ultrasound sensor 105. The RF capture board 130, like the video capture board 125, is standard, and it can be implemented using almost any high frequency digitizer card, where it would be preferable that the digitizer card is capable of operating at a frequency 10× that of the ultrasound probe operating frequency.
In addition, the workstation 120 includes a CIS tracker module 135. The CIS tracker module 135 receives and processes signals from the optical tracker 110, from which, the position of the ultrasound probe and the robot end-deflector may be determined. A suitable device for the CIS tracker module 135 would be the tracker module developed by ERC CISST Lab.
The workstation 120 further includes a robot client module 140. The robot client module 140 communicates with the robot 115 and, more specifically, provides control commands to the robot 115. The robot client 140 may be the Medical Robot Control (MRC) device developed by the ERC CISST Lab.
The next components in workstation 120 are the strain imaging module 145 and the incremental 3D ultrasound module 150. The strain imaging module 145 generates the strain characteristics of the captured 2D ultrasound data, which can be estimated as quickly as the B-mode acquisition. The strain estimation algorithm may be correlation-based, as shown, for example, in
The workstation 120 also includes a 5D visualization and volume rendering module 155. This module provides a volume rendering pipeline that merges both 3D ultrasound anatomy information with elasticity data. The pipeline provides a projection of the 4D data (i.e., 3D anatomy and 1D elasticity) into 3D scenes over time. The projections can be implemented in many ways. In general, however, and in accordance with exemplary embodiments of the present invention, the elasticity data is blended with the anatomy data.
Finally, the workstation 120 includes the deformable model segmentation module 160. As stated, the present invention provides a useful tool for IGT and CIS applications. One main challenge in this field is to have a reliable real-time tracking mechanism. This is easily with the present invention for a wide variety of surgical interventions due to the integration of elasticity information, as well as the use of feedback data and control which is generally provided by the segmentation module 160, as shown in
Referring now to
With regard to the Phase 2 in
As stated above, the strain estimation may be correlation based, as set forth, for example, in the first stage of the process illustrated in
Estimating the local strain is an essential step, which requires a high level of accuracy, since the amplitude of tissue deformation is relatively small. In accordance with exemplary embodiments of the present invention, two techniques are primarily considered. The first technique utilizes the maximization of normalized cross-correlation between the pre- and post-compression RF signal after applying ID companding. This is illustrated in
As stated above, and as illustrated in
It will be apparent to those skilled in the art that various modifications and variation can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
This application claims the benefit of U.S. Provisional Patent Application No. 60/488,941, filed on Jul. 21, 2003, which is hereby incorporated by reference for all purposes as if fully set forth herein.
The research and development effort associated with the subject matter of this patent application was supported by the National Science Foundation under grant no. EEC9731478.
Number | Date | Country | |
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60488941 | Jul 2003 | US |