Abstract:
An apparatus and method for localizing a nuclear-emitting lesion during an intervention using correlated nuclear and ultrasound imaging. The apparatus provides interventional access and quasi-stereotactic positioning of interventional devices, with real-time ultrasound image visualization for tracking the approach of the device to the lesion. The apparatus is intended to overcome the shortcomings of fully-stereotactic nuclear-emission image localization.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 61/348,730, filed May 26, 2010, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of medical imaging. More specifically, the invention relates to systems and methods for using nuclear-emission imaging to localize lesions for tissue harvesting or marking. 
       BACKGROUND OF THE INVENTION 
       [0003]    In medicine, nuclear-emission imaging is commonly utilized to identify regions (lesions) that may contain abnormal cells, and must be sampled, marked or otherwise treated using interventional devices. Stereotactic methods using nuclear-emission imaging have been developed to position a device in relation to a lesion for performing an intervention; however, guiding interventions using these methods can be problematic due to procedure time constraints, lesion movement, interventional device control, and the three-dimensional resolving power of the nuclear image. 
         [0004]    Methods of guiding interventions using nuclear emission-imaging and nuclear-emission imaging in conjunction with anatomic imaging have been disclosed in literature. In comparison with guiding interventions using correlated nuclear emission and ultrasound imaging as with the present invention, existing methods lack clinically important characteristics including: a) clinical expediency, b) the ability to accommodate the necessary redirection of the interventional device in real time during insertion due to tissue characteristics, lesion movement, or mis-targeting, c) the ability to verify the location and progress of the intervention, d) freedom from the use of additional doses of ionizing radiation for extra nuclear imaging procedures, and e) freedom from reliance on cumbersome radioactive fiducial instruments. Examples of these methods include: 
         [0005]    One example of an existing method is disclosed in U.S. Pat. No. 4,977,505, Means to correlate images from scans taken at different times including means to determine the minimum distances between a patient anatomical contour and a correlating surface, issued to Pelizzari, et al. Pelizzari discloses correlative methods to improve precision of applied clinical techniques (such as surgery) to nuclear emission identified regions of interest. However, Pelizzari fails to disclose an apparatus or method means to utilize precise correlative methods without additional ionizing radiation. 
         [0006]    U.S. Pat. No. 5,961,457, Method and apparatus for radiopharmaceutical-guided biopsy, issued to Raylman, et al. discloses a method of localization using nuclear emission in three dimensions. Raylman also describes a method of utilizing radioactive fiducial marker to confirm localization. However, Raylman fails to teach apparatus or method to perform the procedure within clinically-acceptable time limits, to accommodate necessary redirection of interventional device during insertion due to tissue characteristics or mis-targeting, and to confirm the actual location of the interventional device with respect to the lesion. It only confirms the location of a surrogate fiducial ‘obturator’. 
         [0007]    U.S. Pat. No. 6,055,450, Bifurcated gamma camera system, issued to Ashburn discloses means for guiding an intervention based exclusively on nuclear-emission imaging. However, Ashburn fails to teach an apparatus or method to perform the procedure within clinically-acceptable time limits, to accommodate necessary redirection of interventional device during insertion due to tissue characteristics or mis-targeting, or to precisely define the location of the lesion in three dimensions. Ashburn also requires the use of a radioactive fiducial. 
         [0008]    US patent application 2003/0153830, Open-access emission tomography scanner by Weinberg, et al. discloses means for guiding an intervention based on nuclear-emission imaging. Weinberg discloses means for stabilizing tissue for generally correlative nuclear-emission and x-ray imaging, and means to provide access to tissue held stable with respect to space coordinates of correlated images. However, Weinberg fails to disclose an apparatus or method for accommodating necessary redirection of interventional device during insertion due to tissue characteristics or mis-targeting, and to confirm the actual location of the interventional device with respect to the emission image. 
         [0009]    Patent application PCT/US2006/023940, Tissue interventions using nuclear emission guidance by Yarnall, et al. discloses a means for guiding an intervention based exclusively on nuclear-emission imaging and means to provide access to tissue with respect to space coordinates of emission images. However, Yarnall fails to disclose an apparatus or method to perform the procedure within clinically-acceptable time limits, to accommodate necessary redirection of the interventional device during insertion due to tissue characteristics or mis-targeting, or to precisely define the location of the lesion in three dimensions. Yarnall also requires the use of a radioactive fiducial. 
         [0010]    US patent application 2010/0016865, Gamma guided stereotactic localization system by Kieper, et al. discloses a method of using a slant-hole collimator for determining the inter-detector position of a gamma-emitting region of interest. However, Kieper fails to a to disclose an apparatus or method to perform the procedure within clinically-acceptable time limits, to accommodate necessary redirection of interventional device during insertion due to tissue characteristics or mis-targeting, or to precisely define the location of the lesion in three dimensions. Kieper also requires the use of a radioactive fiducial. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention is intended to simplify nuclear-emission guided tissue interventions. Of particular interest is simplifying interventions of breast lesions identified using nuclear-emission imaging by using correlated ultrasound imaging for real-time targeting, for guiding the trajectory of interventional devices and for verifying the success of the intervention. 
         [0012]    In one aspect of the present invention an apparatus and method is provided that can be utilized to quickly and accurately position an interventional device in relation to a lesion of interest by first identifying the location of the lesion in two dimensions using nuclear emission imaging and then by determining the third dimension using ultrasound imaging applied precisely at the two-dimensional location predefined by nuclear emission imaging. In this way, the lesion of interest may be determined by ultrasound even though it may not be otherwise distinguishable from surrounding abnormalities. Once the lesion has been identified, the task of interventional device localization is simplified using the recognized advantages of real-time structure visualization afforded by ultrasound imaging. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  illustrates a cross sectional side view of one embodiment of a nuclear-emission imager with ultrasound correlation for body part imaging for interventions according of the present invention. 
           [0014]      FIG. 2  illustrates a perspective view of the nuclear-emission imager with ultrasound correlation for body part imaging of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Nuclear-emission imaging is sometimes used to identify abnormal cellular function(s) (e.g. glucose metabolism as with FDG-PET, mitochondrial proliferation as with sestamibi-scintigraphy) of a region of tissue (lesion) that may be associated with tumor growth (neoplasia). However, it is difficult to use nuclear-emission imaging alone to guide interventions due to the long image acquisition periods (e.g. five minutes), unacceptable nuclear-emission image spatial resolution and the transparency of most interventional devices to emission imaging. 
         [0016]    Ultrasound imaging may be utilized to identify very subtle abnormalities in tissue density and structure that commonly result from neoplasia. However, abnormalities produced by cancer are difficult to distinguish from abnormalities produced by benign processes using ultrasound, and ultrasound alone is considered to have unacceptable specificity for early breast cancer detection. Notwithstanding, it is commonly understood that most suspect lesions found by imaging methods that are used for early breast cancer detection such as x-ray mammography, MRI or nuclear emission imaging have developed some degree of associated anatomical abnormality that can be found by carefully surveying the region of the suspect lesion with ultrasound imaging, referred to as ‘second pass ultrasound’. The difficulty becomes confining the ultrasound survey to the region of the suspect lesion so as to preclude or reduce the possibility of another lesion being mistaken for the suspect lesion. An example of a confined region may be along a line specified as normal to a plane where the line is defined by two dimensions through the plane. In this regard, the specificity of ultrasound for identifying a suspect lesion can be improved by confining its survey to the region of the suspect lesion. An example of an unconfined region may be a specified breast quadrant. 
         [0017]    Interventional guidance is highly simplified by ultrasound imaging once the suspect lesion in question is identified because the trajectory of the interventional device can be adjusted in real time during insertion and proper tissue harvesting or marking may easily be verified with real-time visualization of both the lesion and the interventional device. The present invention may enable lesions identified on nuclear-emission imaging to be identified with high specificity using ultrasound imaging. An apparatus and method for enabling the nuclear-emission and ultrasound correlated intervention will be further described below. 
         [0018]    The present invention provides an apparatus and method for localizing a lesion that has been identified on a nuclear-emission image using correlated nuclear and ultrasound imaging. The method combines the steps of stabilizing the tissue in relation to the nuclear imager, obtaining a nuclear-emission image, determining the location of the lesion in two dimensions relative to the nuclear imager (e.g. x-y coordinates that are normal to the plane of the detector), providing interventional access, positioning an ultrasound transducer facing the lesion using the nuclear-emission identified lesion coordinates, identifying the likely lesion using ultrasound, and using the ultrasound image to guide and verify the intervention. Some embodiments may further confirm the lesion was altered using nuclear-emission imaging. 
         [0019]    One embodiment of the apparatus according to the present invention may include a device for immobilizing the body part with respect to the space-coordinates of the nuclear-emission imager. Some embodiments may also include a device for shielding the field of view of the nuclear-emission imager from stray radiation during image acquisition that also provides intermittent access for interventions while maintaining immobilization. Some embodiment may also use a rigid localization fixture for positioning an ultrasound transducer normal to a plane at the two-dimensional coordinates determined by nuclear-emission imaging. 
         [0020]    As shown in  FIG. 1 , a body part  110  has been immobilized by compression and readied for an intervention on one embodiment of a nuclear-emission imager with ultrasound correlation apparatus  100 . A lesion  109  has been identified in at least the x and y-axis locations shown as shown in  FIG. 2  using a single gamma-ray detector  108 . As shown in  FIG. 1 , some embodiments may use a second gamma ray detector  112 , which may be needed for coincidence imaging or dual-detector imaging, displaced opposing the single gamma-ray detector  108  to provide access to body part  110 . An ultrasound transducer  103  may be precisely positioned and stabilized to focus on and capture images in the region of lesion  109  at said x and y locations (e.g. location D-E; 8  as shown in  FIG. 2 ) by the adjustable frame  104 . The ultrasound transducer  103  may be repositioned without sliding across the surface of the body part  110  (e.g. skin) to prevent unwanted body part movement that could disturb the location of the lesion. To reposition the ultrasound transducer  103 , the operator may release the ultrasound transducer  103  from a beam  106  of the adjustable frame  104  and relocate the ultrasound transducer  103  to a more desired location. Embodiments that include a shielding panel  101  may be used with a single gamma ray detector  108  and can be moved to a raised position  102  to provide access to the body part  110  for positioning the ultrasound transducer  103  and performing the intervention. 
         [0021]    Once the operator identifies the lesion  109  using images produced by the ultrasound transducer  103 , an intervention can be initiated. Various interventional access methods may be provided by the apparatus of the present invention including between the compression frame  107  and the nuclear emission imager  108  and aside the beams  106  of the compression frame  107 . For example, an interventional device can be placed in the same position on the beam  106  where the ultrasound transducer  103  was placed to locate the lesion  109 . In the same manner in which the ultrasound transducer  103  may be relocated, an intervention device may also be relocated to adjacent slots (e.g.  111 ) to provide full access to all locations within the compression frame  107 . To relocate a single compression beam  106 , spring-loaded tabs  105  may be slid outward as depicted by the arrows on the compression frame  107 . The spring-loaded tabs  105  may release the compression beam  106  so it can be removed up and out of its slot, then installed back down into an adjacent slot, while immobilization of the body part  110  and the lesion  109  is maintained by the neighboring beams of the compression frame  107 . 
         [0022]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims. Accordingly the embodiments of the invention described herein are merely illustrative of the application of the principles of the invention. For example, the use of MRI or optical imaging instead of nuclear-emission imaging, or the use of various types nuclear emission imaging including but not limited to PET, dual-head scintigraphy and Compton imaging may also be used to achieve the same. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.