Abstract:
Guided biopsy is a commonly used method to remove suspicious tissues from an internal organ for pathological tests so that malignancy can be established. Provided herein are systems and methods (i.e., utilities) that allow for automated application of one or more predefined biopsy target plans to an acquired medical image including without limitation, an ultrasound prostate image. Due to different shapes and sizes of prostates as well as orientation of prostate with respect to an ultrasound probe during image, acquisition a simple prostate model (e.g., ellipse) with a fixed plan may not be sufficient. Accordingly, it has been determined that a deformable shape model with integrated biopsy target locations/sites may be fit to a prostate image to provide improved automated biopsy targeting.

Description:
FIELD OF INVENTION 
       [0001]    The present invention is directed at image guided biopsy procedures. More specifically, the present invention is directed at applying predetermined biopsy locations/plans to medical images to reduce the time required to perform a biopsy procedure and/or improve the accuracy of such a procedure. 
       BACKGROUND OF THE INVENTION 
       [0002]    Prostate cancer is the second leading cause of death among males in the USA. However, it, is often curable if detected at an early stage. Accordingly, early detection and treatment is important. In general, a biopsy is recommended when a patient shows high levels of PSA (Prostate Specific Antigen), which is an indicator of prostate cancer or the patient has an abnormal physical exam (e.g., digital rectal exam). Ultrasound has been the main imaging modality for prostate related applications due its inexpensiveness, ease of use, and ability to scan in real-time during biopsy and treatment. 
         [0003]    Transrectal Ultrasound (TRUS) Guided Prostate Biopsy is a standard procedure for obtaining biopsy samples with ultrasound guidance. In such a procedure an end-fire or side-fire ultrasound probe is used that generates a 2D image plane. For biopsy sampling, most probes require a needle set placed through a guide tube parallel to the axis of the probe and the needle set can be extended beyond the end of the probe to obtain a biopsy sample. During the procedure, the urologist inserts the ultrasound probe into the rectum, and moves the probe until specific area of the prostate to be sampled is identified in the live ultrasound scan. The urologist then moves or bends the probe upward, pointing the biopsy needle channel or biopsy needle set guide at the targeted area of the prostate. A needle set is inserted through the needle channel or guide, pushed through the rectum wall and into the prostate. The needle is then fired using La biopsy gun and tissue samples are collected. Usually, multiple samples are taken from different areas of the prostate, typically between 6 and 18 samples. 
         [0004]    There have been efforts to plan optimal locations for prostate biopsies. However problems arise due to the 2-D nature of ultrasound image. That is, the plan is defined in a 3-D frame, of reference but the manual guidance of needle by the urologist is done based on guidance using a 2-D image. With the advent of techniques for reconstructing a 3-D volume from a sequence of 2-D ultrasound images, a user is now able to plan a biopsy procedure in a 3-D volume corresponding to the prostate shape of the individual patient. In such a scenario, the urologist, acquires a series of 2-D ultrasound images of the prostate, which are reconstructed into a 3-D image-volume by the system. The user then plans the target sites for collection of tissue using the 3-D image and, then proceeds to collect the samples from the planned sites. However, selection of the target sites is still done manually and depends upon the skill of the user in selecting target sites while also adding to the time of the procedure. This adds extra burden on the workflow and affects the sensitivity and specificity of the, procedure. 
         [0005]    An alternative to the manual approach is to arrange 6, 12, 16 or 18 core biopsy sites  100  on a biopsy site model  100  (see  FIG. 1A ) and overlay the biopsy site model onto an object (e.g., prostate  104 ) of a real data set, (e.g., a 3-D image). Such a procedure provides a rudimentary automated biopsy planning system. However, such an automated fitting procedure does not take shape and topology of the real data set (e.g., prostate image) into consideration while loading the target sites in the planning system. 
         [0006]    In medical imaging systems, one major challenge lies in handling the changing shapes of the anatomies due to growth, hydration, diseases or in response to the treatment during therapeutic procedures. Thus the main limitation of the current automated planning systems lies in their inability to handle the changes in shape of the imaged, object. In many instances, simply applying a biopsy site model  102  to the object  104  results in one or more biopsy locations  106  being located outside of the boundary of the, object  104 . See  FIG. 1B . That is, by not accounting for changes in the shape of an object from individual to individual, overlaid biopsy models may fail to correctly locate biopsy positions. Further, many medical imaging systems result in images without sufficient information in one or more occluded planes. This further complicates the image planning and guidance systems, which require *putting the 3D core locations where biopsies need to be drawn from. 
         [0007]    A number of systems or devices have been proposed for the purpose of better targeting of biopsies. For instance, one system includes an ultrasonic transrectal probe and an ultrasonic transurethral probe where each probe is in operative communication with an integrated patient support platform and an integrated expert system. The integrated expert system collects data transmitted by sensors in the transrectal and transurethral probes and produces level-of-suspicion mapping of the prostate gland with cancer probability assessments for areas contained within the level-of-suspicion mapping. Generally, previous systems, have required specialized equipment, and do not make use of existing ultrasound systems and technology or have required fusion of multiple modalities (e.g., MRI, CT, ultrasound) and/or the implant of fiducial markers or seeds as landmarks or references. Finally, previous systems have failed to utilize prior information specific to current patient and/or specific to a previously identified group (e.g., demographic group) of patients. 
       SUMMARY OF THE INVENTION 
       [0008]    Guided biopsy is a commonly used method to remove suspicious tissues from an internal organ for pathological tests so that malignancy can be established. Provided herein are systems and methods (i.e., utilities) that allow for automated application of one or more predefined biopsy target plans to an acquired medical image, including, without limitation, an ultrasound prostate image. In this regard, the utilities may be implemented in software and computer processing systems that are integrated into medical imaging devices and/or that are interconnected to the medical imaging devices and operative to receive data therefrom. 
         [0009]    The utilities allow for automatically loading a standard or a customized biopsy plan onto a medical image. Due to different shapes and sizes of prostates as well as orientation of prostate with respect to the ultrasound probe during image acquisition, a simple prostate model (e.g., ellipse) with a fixed plan may not be sufficient. Accordingly, it has been determined that a deformable shape model with integrated biopsy target locations/sites may be fit to a prostate image. Such a shape model may incorporate standard plans (e.g., sextant, plans, etc.) or customized plans based on, for example, demographic information and/or prostate regions known to be susceptible to cancer (e.g., atlas information and/or previous biopsy information). One main advantage of this utility is full automation (e.g., real time application) of standard or other prepared biopsy plans to a prostate image, which improves workflow and reduces time during the biopsy procedure, while being,accurate. The utility is also flexible to allow the users to also add and refer to the saved customized plans. 
         [0010]    According to a first aspect, a method for use in applying biopsy target sites to medical prostate images is provided. The method includes obtaining a deformable shape model that is generated from a plurality of prostate images. Use of such a shape model allows for better fitting the model to an acquired prostate image. That is, the shape model, or mean shape of a sample population, allows for better fitting a biopsy plan to different sizes and shapes of prostates as well as orienting the biopsy sites with respect to a currently acquired prostate image. Once the deformable shape model is obtained, a biopsy plan may be identified for use with the shape model. This biopsy plan may then be loaded into the deformable shape model such that the biopsy target locations associated with the plan are registered to locations within the deformable shape model. 
         [0011]    In a first arrangement, the biopsy plan may be dynamically loaded into a deformable shape model. For instance, during a prostate imaging procedure, the user may select a biopsy plan that may be loaded into the deformable shape model. Accordingly, the shape model and biopsy plan may then be fit to the prostate image. In another arrangement, the biopsy plan may be loaded into the shape model prior to the procedure. In such an arrangement, a plurality of different biopsy plans may be loaded into shape models such that each shape model includes a specific biopsy plan. Accordingly, such a plurality of deformable shape, models and biopsy plans may be stored in a database for selection by a user. 
         [0012]    According to another aspect, a method is provided wherein a plurality of biopsy targeting plans are provided to a user during the prostate imaging procedure. The user may then select one or more of the biopsy targeting plans. Accordingly,, biopsy target locations associated with a selected one or more of the biopsy targeting plans may be applied to the image of the prostate. Furthermore, the method includes outputting a processed image of the prostate, with the biopsy target locations illustrated on the processed image. As will be appreciated, this processed image may allow for guidance of a biopsy device to the  1 locations of interest (e.g., biopsy target sites). 
         [0013]    In a further arrangement, the plurality of biopsy targeting plans may include previous biopsy information. For instance, such information may include a previous biopsy procedure performed on the patient. This previous biopsy procedure and the locations of previous biopsies may be stored for subsequent use. Accordingly, at a subsequent procedure, the previous biopsy locations associated with the previous procedure may be selected and applied to the processed image. A physician/user may then identify previous locations where biopsies were performed and select new locations and/or apply a new biopsy plan to the processed image. 
         [0014]    Such biopsy plans may include, without limitation, conventional plans that provide a predetermined number of locations (e.g., sextant, 8, 12, etc.) as well as customized plans that are based on, for example, statistical information. In this latter regard, it will be appreciated that biopsy plans may be developed based on statistical information associated with known regions in the prostate having increased likelihood of cancer. Applying the biopsy target locations to the image of the prostate may include use of a shape model that allows for adjusting the desired biopsy locations to the individualized characteristics of the prostate of a current patient. In this regard, it may be desirable to utilize a shape model that is generated based on actual prostate images. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1A  illustrates a, prostate biopsy location plan. 
           [0016]      FIG. 1B  illustrates application of the plan of  1 A to a prostate 
           [0017]      FIG. 2  illustrates an overall system for acquiring ultrasound images and applying predetermined biopsy plans to that image. 
           [0018]      FIG. 3 , illustrates an imaging device for use in obtaining an ultrasound image and applying a predetermined biopsy plan to the image. 
           [0019]      FIG. 4A  illustrates a plurality of two-dimensional images. 
           [0020]      FIG. 4B  illustrates a three-dimensional image generated from the two-dimensional images of  FIG. 4A . 
           [0021]      FIG. 5  illustrates a process flow diagram for the deformation of a stored biopsy plan onto a current image. 
           [0022]      FIG. 6  illustrates a process for generating a mean shape/model. 
           [0023]      FIGS. 7A-C  illustrate a predetermined biopsy plan as applied to a shape model, a prostate volume and the shape model applied to the prostate volume, respectively. 
           [0024]      FIG. 8  illustrates various zones on a prostate. 
           [0025]      FIG. 9  illustrates the implementation of a biopsy plan into a shape model. 
           [0026]      FIG. 10  illustrates a process for deforming a shape model to match a current image. 
           [0027]      FIG. 11  illustrates a process for mapping reference plan onto current image using thin-plate splines. 
           [0028]      FIG. 12  illustrates a screenshot that may be utilized with the presented system. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Reference will now be, made to the accompanying drawings, which assist in illustrating the various pertinent features of the present disclosure. Although the present disclosure is described primarily in conjunction with transrectal ultrasound imaging for prostate imaging it should be expressly understood that aspects of the present invention may be applicable to other,medical imaging applications. In this regard, the following description is presented for purposes of illustration and description. 
         [0030]    Presented herein are systems and processes (utilities) to aid urologists (or other medical personnel) in planning target sites for biopsy. Generally, the utilities use biopsy site model that may be fit (e.g., warped) to an image of a prostate. Such fitting accounts for differently shaped prostates. These, biopsy shape models may incorporate statistical information regarding various zones within a prostate where the cancer resides and/or probability maps of cancer locations obtained from an expert (histologist) based ground truth selection. 
         [0031]    The current invention is aimed at automatic targeted biopsy procedure.  FIG. 2  describes an overall process  200  for an ultrasound guided biopsy procedure where an automated biopsy planning system is utilized to locate biopsy locations on/in an ultrasound image. Initially, the patient  202  is positioned by a physician  204  (e.g., on an examination table), and a 3-D image of the prostate is acquired  206  using, for example, a transrectal ultrasound (TRUS) transducer. The resulting 3-D image  208  may either be directly obtained by the TRUS probe or reconstructed on the fly from a sequence of 2-D images obtained through either rotation or translation of TRUS probe, or a, combination of both methods. 
         [0032]    After acquiring the image  208 , the 3-D volume is observed and target locations are located by a biopsy planning system  210 . The planning system  210  utilizes a deformable prostate model  212  and one or more reference plans  214  to automatically locate biopsy locations on the ultrasound image. That is, a number of predetermined standard and/or customized sampling plans  214  are defined and stored in frame of reference of a prostate model  212 . During the procedure, the model  212  is deformed into the 3-D volume/image  208  acquired from the patient  202  and the plan  214  is automatically deformed into the new frame of reference. This results in generating an image having planned biopsy sites  216  located thereon and/or therein. The physician  204  may then perform biopsy sample collection  218  at the planned sites to obtain tissue for pathological evaluation.  220 . Various portions of the process  200  are discussed herein. 
         [0033]    Ultrasound Image Acquisition 
         [0034]    Initially, a 3-D ultrasound image of a prostate of a patient is acquired using, for example a transrectal ultrasound (TRUS) system. See  FIG. 3 . The acquired images may then be converted to 3-D orthogonal voxel data (e.g., ultrasound volumes) having equal resolution in all three dimensions. The images may be acquired in an appropriate manner.  FIG. 3  illustrates a transrectal ultrasound probe  10  being utilized to obtain a plurality of two-dimensional ultrasound images of a prostate  12 . As shown, the probe  10  may be operative to automatically scan an area of interest. In such an arrangement, a user may rotate the acquisition end  14  of the ultrasound probe  10  over an area of interest. Accordingly, the probe  10  may acquire plurality of individual images while being, rotated over the, area of interest. See,  FIG. 4A . Each of these individual images represents a two-dimensional image. Initially, the stack of such images may be in a polar or curvilinear or any other non-Cartesian coordinate system. In such an instance, it may be beneficial for processing to translate these images into a rectangular coordinate system. In any case, the two-dimensional images may be combined to generate a 3-D image see  FIG. 4B . That is, the processing platform  30  of the ultrasound imaging device may receive the 2-D images and generate a 3-D image, which may be output to the physician urologist on a monitor  40 . The processing platform  30  also includes a database  50  of biopsy plans. A selected one (or more) of the biopsy plans and/or prior biopsy information  60  (e.g., patient specific information) may be fit to an acquired image to provide biopsy target site locations on the 3-D image output to the monitor  40 . One advantage of this process is full automation of stored biopsy plans, which improves work flow and reduces time during the biopsy procedure, while being accurate. The method is flexible to allow the users to also, add and refer to the saved customized plans. 
         [0035]    Planning System 
         [0036]    In a conventional planning system, the ultrasound image is utilized by a physician to identify target biopsy locations. These target locations are identified based solely on the judgment of the physician. However, this can require a significant amount of time thereby increasing the overall time required for a biopsy procedure. An alternative to the conventional planning approach is using predefined biopsy plans (e.g., 6, 12, 16 or 18 cores sites) with a deformable shape model and fitting the shape model to a prostate image. As discussed herein, the use of a deformable shape model takes into account differences in shape, scale and topology while integrating the target sites into the image. 
         [0037]    The automatic loading of a predetermined biopsy plan to a current frame of reference can be done in a number of ways. In a general scenario, as illustrated in  FIG. 5 , an ultrasound image  502  of a patient is acquired and provided to a segmentation processor  504 . The segmentation processor generates segmented image.  506 . The segmented prostate image  506  and a prostate model  508  are provided to an alignment system  510  which aligns the model and image to a common reference frame to produce an aligned volume  5 . 12 . A reference plan  514  is loaded with the prostate model in an interpolation process  516 . That is, a model of the shape of the organ is constructed and the target sites are defined (i.e., loaded) on this model shape. At the time of automatically loading the plan, the model shape can be deformed into the 3-D volume of the target volume to provide planned biopsy sites on the prostate image/volume  518 . At such time, a physician may take biopsy samples from the planned sites. See  FIG. 2 . 
         [0038]    For the shape of a prostate, a number of plans may be defined on a simple-shape such as an ellipsoid. The ellipsoid can then be deformed into the shape of the actual organ imaged at the time of image acquisition. The deformation can then be interpolated to deform the target locations into the frame of reference of the 3-D target volume. The deformation may be performed via intensity registration, segmentation of organ followed by surface registration, anatomical, landmark registration or a combination of these methods. Rather than using a simple shape as a prostate model, a mean shape model generated from actual prostate images can provide a number of advantages. 
         [0039]    That is, a mean shape of a population defines a shape that has least differences from the population in statistical sense. In addition to using the mean shape, the population shape statistics can be used to deform the shape in ways more meaningful than registration based on just the differences between two images. The next section describes the construction of a mean shape of population and the methods used to compute the statistics over a set of shapes. Once a mean shape has been computed or a model chosen, it is equally important to place the standard or customized plans on this shape. 
         [0040]    Shape Model 
         [0041]    The first step is the construction of a prostate shape model. While simplistic solutions exist such as assuming a synthetics shape of an ellipsoid or any other surface of revolution, specifically for a prostate shape, computing a mean shape over a number of actual prostate images provides a more meaningful solution. That is use of actual prostate images results in a mean shape that better describes a population (e.g., specific demographic group) compared to picking a synthetic-shape. Plans defined on a mean shape computed from a set of training images are thus more anatomically relevant. Further, the deformation of a synthetic shape does not mimic the actual, anatomical deformation compared to a mean being deformed using population shape statistics where the main modes of variation correspond to the typical deformations characterizing the shape descriptions within the subspace of a shape model generated from actual images. Further, the mean shape is invariant to rotation, scaling and translation and requires the shortest description to fit to the current shape which is assumed to lie within the span of the set of training shapes (e.g., actual prostate images). Thus using a mean shape will generally provides a better solution than an arbitrary image or synthetic model. Such a mean shape, may be generated in a manner similar to the method described in U.S. patent application Ser. No. 11/740,807, entitled, “Improved System and Method for 3-D Biopsy,” the entire contents of which is incorporated by reference. 
         [0042]      FIG. 6  illustrates a process.  600  for generating a mean shape. The first step is to obtain a number of samples from a population. This is done by scanning the organ (prostate) over a number of subjects and collecting the 3-D (e.g., grayscale) prostate images. That is, a training set  602  is acquired. Next, the prostates in the training set are segmented  604  from the 3-D images/volumes using either expert manual segmentation, a semi-automatic segmentation process such as disclosed in U.S. patent application Ser. No. 11/615,596, entitled, “Object recognition System for Medical Imaging,” the entire contents of which are incorporated by reference or in a fully automatic segmentation approach as described in U.S. patent application Ser. No. 11/833,404, entitled, “Improved Object Recognition System for Medical imaging,” the entire contents of which are incorporated by reference. This generates a set of segmented prostate surfaces  606 . 
         [0043]    One segmented prostate surface is selected  608  as the tentative template surface  610  or tentative mean shape. Each remaining segmented prostate surface (i.e., target surface) may selected  612  and aligned (e.g., Procrustes aligned) with the template surface  614  to result in a set of aligned shapes with rotation, scaling and translation differences removed. This set of aligned shapes is averaged  616  resulting in a new mean shape  618 . The process is repeated until successive iterations of the computed mean shape are nearly identical (i.e, until convergence). This results in a final mean shape  620  for the training data set. 
         [0044]    In addition, the shape statistics of the training set may be encapsulated into modes of variation computed via active shape model analysis. In this regard, such shape statistics may be used to drive the registration or even to compute the object boundaries. 
         [0045]    Construction of Plans 
         [0046]    The next step after construction of a standard shape model (or mean shape) is to define conventional plans (of standard plans) on the shape model. Literature exists on the conventional plans (e.g., sextant biopsy) followed by urologists as, well as on computation of optimal positions for detection of cancer via use of a probabilistic atlas similar to that discussed disclosed in U.S. patent application Ser. No. 11/740,807, entitled, “Improved System and Method for 3-D Biopsy,” as incorporated above. The presented utility is easily extensible to include any new or customized plans. 
         [0047]    For construction of a conventional plan, there are a number of options manual placement of the plan over the model by an expert, semi-automatic placement of plan through landmark identification by the expert and placement of plan relative to these landmarks, fully automatic placement of plan through automatic landmark detection and automatic placement of points and automatic even distribution of sites in the target plan based on the mean shape. The proposal is general enough to include any of these ideas in construction of the database of standard plans. In addition, optimal plans computed from a probabilistic atlas, may also be used.  FIG. 7A  illustrates the placement of a sextant biopsy plan including, six biopsy locations  702  into a deformable model  704 . Methods,for placing biopsy locations within a model are discussed herein. 
         [0048]    As will be appreciated, different zones of prostate correspond to different prostate anatomy. As shown in  FIG. 8 , various zones are distributed around the whole prostate, except the central part where the urethra intersects the prostate. Accordingly, it may be desirable to place biopsy sites in different zones of the prostate. For the sextant biopsy plan, there are  3  zones on each side of the prostate. On each side, one zone is set close to the base, one is close to the apex, and the third one is on the middle gland. If more biopsy sites are planned, each of these zones can be further divided into smaller zones, so that more samples will be taken for the biopsy. See, for example,  FIG. 7A . 
         [0049]      FIG. 9  presents a conventional plan construction system. As illustrated, the segmented prostate images  902  of the training set (See, e.g.,  FIG. 6 ) are combined with zonal data  904  taken from removed prostate glands (e.g., prostatectomies). That is, the zonal data is projected  906  into the segmented images such that prostate zones  908 i are, defined in the mean shape/model. Biopsy sites are then selected in different zones to define a conventional biopsy plan  912 . This plan (e.g., sextant biopsy plan) may then be stored to a database such that a physician may at the time of the biopsy procedure, select the plan for implementation with a current prostate image. 
         [0050]    In addition to construction of standard plans (e.g., 8, 12, 16, 20 biopsy locations), additional biopsy plans from previous visit(s) may also be stored by the system. Such previous biopsy plans may be archived together with previous ultrasound scans and corresponding segmented prostate surfaces. Previous biopsy plans can be important, as a urologists may want to revisit previous biopsy sites, or avoid doing biopsy at the same sites. Previous biopsy plans are also an option for use with reference plans. 
         [0051]    Loading a Plan in Current Prostate Volume 
         [0052]    Loading a plan from the frame of reference of the model into the frame of reference of the target image (the 3-D image volume acquired during the current procedure) requires finding correspondences between the two frames of reference. This can be done using a variety of registration techniques depending upon the available information. Different techniques are discussed below. 
         [0053]    As shown in  FIGS. 7A-7C , if the object boundaries from the current prostate volume  706  are available, then the surface of the model  704  (or mean shape) can be registered with the surface of the subject prostate  706 . This allows for registering the biopsy locations  702  of the model  7041  with the current prostate volume/image  706 . This may be done using a surface registration, technique such as an adaptive focus deformable model. Such an algorithm is illustrated in  FIG. 10 . Initially, the shape model and subject prostate are segmented  1002 A,  1002 B. Then for each vertex in the model its neighborhood information is searched  1004 A and saved as attribute vector for it  1006 A. Also, for each vertex in the subject, its neighborhood information is searched  1004 B and saved as attribute vector for it  1006 B. A multi-resolution alignment strategy  112  is carried out by sub-sampling a set of snaxels  1008  along the snake contour using initial search length in the neighborhood, and deforming their corresponding snake segments  1010 . Such alignment  1012  may be performed using the deforming forces defined between vertices in the model and its closest vertex in the subject, and vice versa. An affine-transformation, matrix  1016  is obtained after the alignment of snake segment. Then the search length, is decreased, therefore increasing the number of snake segments  1014 . This alignment procedure is repeat. That is the alignment procedure may be iteratively repeated until maximal number of iterations is reached. A local curve-fitting procedure  1018  is performed to refine the deformation and final deformed old surface  1020  is obtained at the end of alignment procedure. The boundary correspondences obtained as a result of the surface registration can be used to interpolate and deform the plan locations from the boundaries into the target shape and displayed on the 3-D image volume See, e.g.,  FIG. 5 . 
         [0054]    The interpolation may be done using an elastically deformable model such as, for example, using a thin-plate spline based interpolation or any boundary elements based or finite elements based method.  FIG. 11  illustrates the interpolation procedure using thin-plate splines. The inputs are the model surface  1102  and the deformed model surface  1104  from the alignment process. Since the model surface  1102  and its deformed version  1104  has one-to-one correspondence for each of its vertex, a global transformation based on thin-plate splines can be constructed  1106 . The parameters for both affine and nonlinear parts in the thin-plate splines transformation  1108  are obtained after the construction. Through those parameters, the biopsy sites identified in the reference plan  1110  can be mapped onto current image using thin-plate spline interpolation  1112 , therefore planned biopsy sites  1114  can be identified. 
         [0055]    Alternatively, the two surfaces may be registered together using the shape statistics obtained after computing the mean shape from a set of samples. The coefficients for the modes of variations are computed hierarchically such that they deform the model shape into the target shape using a boundary matching cost criterion. The deformation at boundaries can be, used to compute deformation at the plan such that the plan is deformed from the coordinate system of the mean shape into the coordinate system of the 3-D volume. If the boundaries of the object from the current 3-D scanned volume are available, the shape model can be used to compute the segmentation. This is done by deforming the mean shape into the frame of reference of the target image. A linear combination of the basis vectors spanning the lower dimensional shape space added to the mean shape provides us with a typical shape. The basis vectors in this shape space account for most of the variance in the entire training set. The coefficients of the basis vectors can be optimized such that the shape obtained is maximally similar to the shape in the target image. 
         [0056]    Intensity based registration also may be performed such that the registration directly provides solution over the entire image volume and the deformation computed at the planned locations are deformed into the 3-D grayscale image volume. Further, shape statistics may be directly used to find the deformation by allowing the shape to deform through the modes of variations computed earlier such that the mean shape deforms into the object shape. This is essentially same as performing the segmentation, but the deformation obtained at the boundaries can directly be used to compute the deformation at the planned locations. The interpolation may follow any of the methods discussed above. 
         [0057]    Adding a New Plan 
         [0058]    Previous sections describe methods used in deforming the shape model and biopsy sites defined in model into the frame of reference of a 3-D prostate volume. The same method can be used to add a customized plan for adding, an optimized plan from a probabilistic atlas. This can be done identifying biopsy locations of a customized plan on the 3-D volume of the shape model. In case of atlas, this represents the frame of reference of the atlas. The volume (or the atlas space) is deformed into the shape of model using a method identical to method described in relation to  FIG. 10 . This is essentially the same method with the correspondence now being defined in the opposite direction instead. As a result,, the customized plan is, now deformed into the frame of reference of the mean shape. This plan can then be saved in the database of plans available. 
         [0059]    The new plan now resides along with other standard plans in the same frame of reference, e.g., the frame of reference of the mean shape. For future reference, the user may now select this plan, from the list and the proposed method then treats it like any of the standard plans already loaded. 
         [0060]      FIG. 12  illustrates a graphical user interface that may be utilized in conjunction with the imaging device of  FIG. 3 . In this regard, the graphical user interface may be displayed on the monitor  40 , illustrated in  FIG. 3 . As shown, the graphical user interface  80  includes a number of display areas  82 ,,  84 ,  86  that allow for displaying the current image and/or displaying the current image in different views and/or displaying prior images and/or prior biopsy information onto the current image. Display area  82  is typically utilized for live ultrasound image acquisition. Moreover, the graphical user interface  80  includes user selectable biopsy plans  90 . In this regard, a user may select a biopsy plan from a menu of biopsy plans and have that biopsy plan applied to a current image. As will be appreciated, such selection and application to the image may be done in substantially real time. That is, the previously stored plans that are integrated with a shape model may be fit to the current image and thereby provide biopsy sites at desired locations therein. In addition, a plurality of previous biopsy plans and biopsy results may be accessible for viewing. As shown in  FIG. 3 , such prior biopsy information may be stored in prior biopsy information database,  60 . 
         [0061]    The overall planning system, which allows for applying predetermined biopsy plans to current medical image, allows for increasing the accuracy and speed in which a biopsy procedure may be performed. Further, while simplistic solutions exist for applying simplistic (e.g., sextant biopsy plans) to a prostate image, computing a mean shape over a number of actual prostate images provides a more meaningful solution. That is, the mean shape describes a population better than a simplistic/synthetic shape, and any plans defined on the mean shape of actual images provides improved anatomical information in comparison to synthetic shapes. Further, the deformation of a synthetic shape often does not mimic the actual anatomical deformation in comparison to a mean shape being deformed using population shape statistics. That is, the mean shape is the closest to the population in a statistical sense and, therefore, typically requires, on average,, smaller deformation to fit to the current shape. Such smaller deformations are typically associated with smaller registration errors and thereby provide Ea better fit solution. 
         [0062]    Another advantage of the present system is that using information from previous visits in a repeat biopsy may help a physician better interpret a current scan. In this regard, the physician may select to revisit or avoid previous biopsy plans presented on a current volume. 
         [0063]    Importantly, the system allows a user to select available biopsy plans from a reference plan list. This allows a physician to rapidly implement a plan they feel best suited for a current patient. In any case, a selected reference plan may be projected onto a current volume after accurate alignment with/integration into the prostate model. Further, use of the deformable shape model takes into consideration changes in prostate shape from patient to patient. Finally, it will be appreciated that the system allows a user/physician to add new plans or edit standard plans, allowing for full customization of biopsy procedure. 
         [0064]    The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings, and skill and knowledge of the relevant art, are. within the scope of the present invention. The embodiments described hereinabove are further intended to explain best modes known of practicing the invention and to enable others skilled in, the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.