Method and apparatus for imaging the anatomy

What is claimed is:

1. A method for transforming and displaying images of the anatomy comprising:

providing a first set of actual reference markers by implanting at least three fiducial implants in spatial relationship to form a plane on a portion of the anatomy to be imaged;

taking a first set of images of a set of parallel cross-sectional slices of fixed thickness of said portion of the anatomy, said set of slices including points in space corresponding to those occupied by said first set of actual reference markers, said first set of images forming a first set of data;

storing said first set of data corresponding to said images in a storing device;

taking a second set of images of parallel cross-sectional slices of fixed thickness of said portion of the anatomy including points in space corresponding to said first set of actual reference markers, said second set of images forming a second set of data;

storing said second set of data corresponding to said second set of images in a storing device;

transmitting data corresponding to said first set of data and said second set of data to a database library;

displaying at least a first slice of said first set of images;

providing a first set of additional reference markers by assigning a number of computer generated reference points to the first slice;

localizing some of said first set of additional reference markers and said first set of actual reference markers in said first slice;

displaying a second slice of said second set of data;

providing a second set of additional reference markers by assigning a number of computer generated reference points to the second slice;

localizing some of said second set of additional markers and said first set of actual reference markers in said second slice;

labeling three of said first set of additional reference markers and said first set of actual reference markers in said first set of images at least one of which is from said first set of additional reference markers;

labeling three of said second set of additional reference markers and said first set of actual reference markers in said second set of images at least one of which is from said second set of additional reference markers;

calculating spatial transformation data relating said first set of images to said second set of images;

storing said spatial transformation data in said database library;

executing said spatial transformation of said second set of images with respect to said first set of images so that the second set of images is an spatial correspondence with said first set of images;

displaying at least one of said transformed second set of images.

2. The method of claim 1, wherein up to nine computer generated reference points are provided to each slice of said first and second set of images.

3. The method of claim 1, wherein up to nine computer generated reference points are provided with the second slice.

4. The method of claim 1, further comprising:

selecting a first point from either of said data sets;

selecting a second point in the same data set; and

computing the distance between the first and second data points.

5. The method of claim 1, wherein said calculating step includes the step of tracing a continuous line about a portion of a slice so that it may be displayed along with the slice.

6. An apparatus for imaging a portion of the anatomy comprising:

three fiducial implants for use as spatial reference markers, said fiducial implants being adapted for implantation in spatial relationship to form a plane in a portion of the anatomy to be imaged;

means for taking a first series of images at parallel cross-sectional slices of fixed thickness of said portion of the anatomy with some of said slices being taken through said fiducial implants;

means for providing a first set of additional reference markers by assigning at least one computer generated reference point to at least one slice within the first said series of images, said means for providing additional reference markers defining a plane from three of said fiducial implants and said first set of additional reference markers, at least one of which is from said first set of additional reference markers;

means for storing a first set of data corresponding to said images in a storage device with reference to the plane established by said fiducial implants; and

means for displaying at least one of said first series of images corresponding to said data for view by a user from said storage device.

7. The apparatus according to claim 6 further comprising:

means for taking a second series of images at parallel cross-section slices of fixed thickness of said portion of the anatomy with some of said slices being taken through said fiducial implants;

means for providing a second set of additional reference markers by assigning a number of computer generated reference points to at least one slice within the second series of images;

means for storing a second set of data corresponding to said second series of images in said storage device with reference to the plane established by said fiducial implants;

and

wherein said means for displaying is capable of displaying at least one portion of said second set of images corresponding to said data from said storage device and said means for displaying includes means for displaying images corresponding to planes defined by three of said fiducial implants and said first and second set of additional reference markers.

8. The apparatus according to claim 7 wherein said means for displaying includes means for displaying at least one of said first series of images simultaneously with at least one of said second series of images.

9. The apparatus according to claim 8 further comprising means for calculating a transformation angle between said first series of images at parallel cross-sectional slices and said second series of images at parallel cross-sectional slices.

10. The apparatus according to claim 9 wherein said means for calculating the transformation angle includes means for selecting a first image from said first series of images, means for selecting a second image to be transformed from said second series of images, means for labeling three of said first set of additional reference markers and said fiducial implants in the selected second image, means for calculating the transformation of said second image to said first image, means for storing transformation data in data base library, and means for executing the transformation of said second image to said first image.

11. The apparatus according to claim 10 wherein said means for calculating the transformation includes transforming the entire second series of images and means for replacing the data corresponding to said second series of images with data corresponding to said transformation in said data base library.

12. The apparatus according to claim 11 further comprising means for displaying the transformation data on said means for displaying for comparison with data from said first image.

13. The apparatus according to claim 8 further comprising means for inputting test parameters and means for calculating a transformation angle of one displayed image according to said test parameters.

14. The apparatus according to claim 13 wherein said means for inputting test parameters includes means for inputting three eulerian angles associated with the transformation angle.

15. An apparatus for imaging the anatomy comprising:

three fiducial implants for use as reference markers, said fiducial implants being adapted for implantation in spatial relationship to form a plane on a portion of the anatomy to be imaged;

means for taking a first series of images of a set of parallel cross-sectional slices of fixed thickness of said portion of the anatomy that includes said reference markers, said first series of images constituting a first set of data;

means for providing at least one slice from said first series of images at least one computer generated reference point;

means for storing said first set of data corresponding to said images in a storing device;

means for taking a second set of images at parallel cross-sectional slices of fixed thickness of said portion of the anatomy, said second series of images including points in space corresponding to said fiducial markers and constituting a second set of data;

means for providing to at least one slice from said second set of images at least one computer generated reference point;

means for storing said second set of data corresponding to said second series of images in said storing device;

means for transmitting data corresponding to said first set of data and said second set of data to a database library;

means for displaying at least a first slice of said first set of images;

means for localizing some of said fiducial markers and computer generated reference points in said first slice;

means for displaying a second slice of said second set of data;

means for localizing three some of said fiducial markers and computer generated reference points in said second slice;

means for labeling three fiducial markers and computer generated reference points in said first slice;

means for labeling said three localized fiducial markers and computer generated reference points in said second slice;

means for calculating the spatial transformation data relating said first slice to said second slice based on said labeled fiducial markers and computer generated reference points;

means for storing said transformation data in a database library;

means for executing a spatial transformation of said second image with respect to said first image using said transformation data; and

means for displaying said second transformed image.

16. The apparatus of claim 15, further comprising:

means for selecting a first point from either of said data sets;

means for selecting a second point in the same data set; and

means for computing the distance between the first and second data points.

17. The apparatus of claim 16, further comprising means for tracing a continuous line about a portion of a slice so that it may be displayed along with the slice, said means for tracing coupled to said means for displaying.

18. A method for transforming and displaying images of the anatomy comprising:

implanting at least three fiducial implants in spatial relationship to form a plane in a portion of an anatomy to be imaged;

taking a first set of images of a set of parallel cross-sectional slices of fixed thicknesses of said portion of the anatomy, said set of slices including points in space corresponding to points in space occupied by said fiducial implants, said first set of images forming a first set of data;

storing said first set of data corresponding to said first set of images in a storage device;

selecting at a user input device at least one of said first set of parallel cross-sectional slices for display on an image screen;

retrieving data from said storage device of said slices selected at said user input device;

displaying said slices selected at said user input device on said image screen;

selecting at said user input device three of said fiducial implants appearing in said slices displayed on said image screen;

localizing said fiducial implants selected at said user input device in said slices displayed on said image screen;

inputting transform parameters at said user input device; and

executing a spatial transformation of said first set of data in accordance with said transform parameters sufficiently to form a first set of modified data, said first set of modified data comprising cross-sectional slices of image data.

19. The method of claim 18 further comprising:

storing patient identification with said first set of data in said storage device; and

selecting a set of parallel cross-sectional slices of image data based on a desired patient identification.

20. The method of claim 18 further comprising:

displaying some of said cross-sectional slices of image data from said first set of modified data on said display screen.

21. A method for transforming and displaying images of the anatomy comprising:

implanting at least three fiducial implants in spatial relationship to form a plane in a portion of an anatomy to be imaged;

taking a first set of images of a set of parallel cross-sectional slices of fixed thickness of said portion of the anatomy, said first set of slices including points in space corresponding to points in space occupied by said fiducial implants, said first set of images forming a first set of data;

storing said first set of data corresponding to said first set of images in a storage device;

selecting at a user input device at least one of said first set of parallel cross-sectional slices for display on an image screen;

retrieving data from said storage device of said slices from said first set of images selected at said user input device;

displaying said slices from said first set of images selected at said user input device on said image screen;

selecting at said user input device three of said fiducial implants appearing in said slices from said first set of images displayed on said image screen;

localizing said fiducial implants selected at said user input device in said slices from said first set of imaged displayed on said image screen;

taking a second set of images of a set of parallel cross-sectional slices of fixed thickness of said portion of the anatomy, said second set of slices including points in space corresponding to points in space occupied by said fiducial implants, said second set of images forming a second set of data;

storing said second set of data corresponding to said second set of images in said storage device;

selecting at said user input device at least one of said second set of parallel cross-sectional slices for display on said image screen;

retrieving data from said storage device of said slices from said second set of images selected at said user input device;

displaying said slices from said second set of images selected at said user input device on said image screen;

selecting at said user input device three of said fiducial implants appearing in said slices from said second set of data displayed on said image screen;

localizing said fiducial implants selected at said user input device in said slices from said second set of data displayed on said image screen;

calculating spatial transformation data relating said slices from said first set of data to said slices from said second set of data;

storing said spatial transformation data in said storage device; and

executing transformation of said first set of data to said second set of data using said spatial transformation data, such that said second set of data is in spatial correspondence with said first set of data.

22. The method of claim 21, further comprising:

storing patient identification information with said first and second sets of data in said storage device; and

selecting sets of parallel cross-sectional slices of image data based on desired patient identification information.

23. The method of claim 22 further comprising:

displaying some of said cross-sectional slices of image data from said first and second sets of data on said display screen after executing transformation of said first set of data to said second set of data using said spatial transformation data.

Description Submit all comments and votes

BACKGROUND OF THE INVENTION

Diagnostic techniques that allow the practicing clinician to obtain high fidelity views of the anatomical structure of a human body have proved helpful to both the patient and the doctor. Imaging systems providing cross-sectional views such as computed tomographic (CT) x-ray imagers or nuclear magnetic resonance (NMR) machines have provided the ability to improve visualization of the anatomical structure of the human body without surgery or other invasive techniques. The patient can be subjected to scanning techniques of such imaging systems, and the patient's anatomical structure can be reproduced in a form for evaluation by a trained doctor.

The doctor sufficiently experienced in these techniques can evaluate the images of the patient's anatomy and determine if there are any abnormalities present. An abnormality in the form of a tumor appears on the image as a shape that has a discernible contrast with the surrounding area. The difference in contrast is due to the tumor having different imaging properties than the surrounding body tissue. Moreover, the contrasting shape that represents the tumor appears at a location on the image where such a shape would not normally appear with regard to a similar image of a healthy person.

Once a tumor has been identified, several methods of treatment are utilized to remove or destroy the tumor including chemotherapy, radiation therapy and surgery. When chemotherapy is chosen drugs are introduced into the patient's body to destroy the tumor. During the course of treatment, imagers are commonly used to follow the progress of treatment by subjecting the patient to periodic scans and comparing the images taken over the course of the treatment to ascertain any changes in the tumor configurations.

In radiation therapy, the images of the tumor generated by the imager are used by a radiologist to adjust the irradiating device and to direct radiation solely at the tumor while minimizing or eliminating adverse effects to surrounding healthy tissue. During the course of the radiation treatment, the imaging system is also used to follow the progress of the patient in the same manner described above with respect to chemotherapy.

When surgery is used to remove a tumor, the images of the tumor in the patient can guide the surgeon during the operation. By reviewing the images prior to surgery, the surgeon can decide the best strategy for reaching and excising the tumor. After surgery has been performed, further scanning is utilized to evaluate the success of the surgery and the subsequent progress of the patient.

A problem associated with the scanning techniques mentioned above is the inability to select and compare accurately the cross section of the same anatomical area in images that have been obtained by imagers at different times or by images obtained essentially at the same time using different image modalities, e.g., CT and MRI. The inaccuracy in image comparison can be better appreciated from an explanation of the scanning techniques and how the imaging systems generate the images within a cross-sectional "slice" of the patient's anatomy. A slice depicts elemental volumes within the cross-section of the patient's anatomy that is exposed or excited by a radiation beam or a magnetic field and the information is recorded on a film or other tangible medium. Since the images are created from slices defined by the relative position of the patient with respect to the imager, a change of the orientation of the patient results in different elemental volumes being introduced into the slice. Thus, for comparison purposes two sets of approximately the same anatomical mass taken atdifferent times, do not provide comparable information that can be accurately used to determine the changes that occurred between two images selected from the respective sets share common views.

The adverse effects on the medical practice of such errors is exemplified by diagnostic techniques utilized by the surgeon or others in diagnosing a tumor within a patient. If a patient has a tumor, its size density and location can be determined with the help of images generated by a scanning device. For the clinician to make an assessment of the patient's treatment, two scanning examinations are required. The patient is subjected to an initial scan that generates a number of slices through the portion of the anatomy, for instance the brain, to be diagnosed. During scanning, the patient is held in a substantially fixed position with respect to the imager. Each slice of a particular scan is taken at a predetermined distance from the previous slice and parallel thereto. Using the images of the slices, the doctor can evaluate the tumor. If, however, the doctor wants to assess changes in the configuration of the tumor over a given period of time, a second or "follow-up" scan has to be taken.

The scanning procedure is repeated, but since the patient may be in a position different from that in the original scan, comparison of the scans is hampered. Slices obtained at the follow-up examination may be inadvertently taken at an angle when compared to the original slices. Accordingly the image created may depict a larger volume than that which was actually depicted before. Consequently, the surgeon may get a false impression of the size of the tumor when comparing scans taken at different periods. Because of this, slice-by-slice comparison cannot be performed satisfactorily.

Similarly for certain surgical techniques it is desirable to have accurate and reliable periodic scans of identical segments of the tumor within the cranial cavity. If the scans before and after surgery are inaccurate, the doctor may not get the correct picture of the result of surgery. These same inaccuracies apply to other treatments such as chemotherapy discussed above.

Additionally, with regard to imaging systems and the integral part they play in surgical and other tumor treatment procedures, there is a dearth of methods currently existing that allow a determination of a desired location within the body a given time. For example, U.S. Pat. No. 4,583,538 to Onik, et al. discloses a localization device that is placed on a patient's skin which can be identified in a slice of a CT scan. A reference point is chosen from a position on the device which exactly correlates to a point on the CT scan. Measurements of the localization device on the CT scan is then correlated to the device on the patient.

Exterior devices have been utilized in an attempt to solve some of these problems with accuracy such as that shown in U.S. Pat. No. 4,341,220 to Perry which discloses a frame that fits over the skull of a patient. The frame has three plates, each defining a plurality of slots on three of four sides. The slots are of varying lengths and are sequentially ordered with respect to length. Frame coordinates defined and found on the frame correspond to the varying heights of the slots. When slices of the skull and brain are taken by an imaging device, the plane formed by the slice intersects the three plates. The number of full slots in the slice are counted with respect to each plate to determine the coordinate of a target site with the brain. Accordingly, only one CT scan is needed to pinpoint the coordinates of the target.

Other attempts have included the use of catheters for insertion into the anatomy. For example, U.S. Pat. No. 4,572,198 to Codington discloses a catheter with a coil winding in its tip to excite or weaken the magnetic field. The weak magnetic field is detectable by an NMR device thus pinpointing the location of the catheter tip with respect to the NMR device.

SUMMARY OF THE INVENTION

Applicant's invention largely overcomes many of the deficiencies noted above with regard to imagers used heretofore. The invention relates to a method and apparatus for insuring that scans taken at different times produce images substantially identical to those of previous scans even if they are from different image modalities at different times. This insures that a more accurate assessment of any changes in anatomy is obtained. As a result, the doctor can be more certain as to the size, location and density of the tumor, or a section thereof, that is located in the cranial cavity.

This ability will enhance the use of surgical techniques in removing or otherwise eliminating the tumor in particular by those noninvasive techniques such as laser technology. By having the ability to define accurately the tumor location and size, laser beams can be focused directly on the tumor. Intermittently, as part of surgical techniques, scans can be made to determine if the tumor has moved or substantially changed in size as a result of the surgery. The laser or other surgical instrument can be adjusted accordingly. Because of the accuracy of the imaging techniques produced by the invention, the doctor can be confident that the amount of healthy tissue destroyed during surgery is minimized.

A method adopted by the invention disclosed herein utilizes fiducial implants or implants to define a plane which cooperates with the imager, or other computer, and particularly the data processing capabilities of the imager to insure that subsequent scanning results in slices substantially parallel to those taken during the initial scan. The fiducial implants are implanted beneath the skin into the calvania and are spaced sufficiently from one another to define a plane. The patient with these implants implanted is placed in the scanning device in the conventional manner and scanned to provide the images of consecutive parallel slices of a given thickness along a predetermined path through the cranial cavity.

As the scans are taken, one or more slices will be needed to accommodate part or all of each fiducial implant. The computational features of the imager or other computer will take into account the spatial relationship between any selected plane of a slice and that plane defined by the fiducial implants. Because of this capability, images taken in subsequent scans at different points in time, at different angles can be reconstructed to be substantially identical with the slices taken originally.

Fiducial implants for this purpose are specially configured and made of material that enables their implantation into the skull and the ability to be detected by scanning devices. The fiducial implant as disclosed herein is configured to insure that during implantation it does not have adverse effects on the skull such as cracking or extending through to the cranial cavity. Nor is it sufficiently exposed between the skull and the skin to distort any external features of the anatomy. Furthermore, the fiducial implant is positioned at least on a portion of the skull at the interface of the skin and the bone of the skull to facilitate its imaging by the imager. At least a portion of the implant is symmetrical in cross-section such that slices taken of the cranial cavity, for example, can be used to locate the center of mass of the implant. This insures accuracy in using the implant image as a reference point to transform the subsequent slices of the follow-up examination into the proper position and orientation.

The above has been a description of certain deficiencies in the prior art and advantages of the invention. Other advantages may be perceived from the detailed description of the preferred embodiment which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily obtained, as the same becomes better understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

FIGS. 1A, 1B, and 1C provide side and overhead views of fiducial implants, with the embodiment of FIGS. 1b and 1c including threading and hex-key structure not shown in the embodiment of FIG. 1a.

FIGS. 2a, 2b provide side and overhead views of a preferred positioning scheme of fiducial implants in the skull.

FIG. 3 is an offset view of two coordinate systems that have undergone translation with respect to each other.

FIG. 4 is an offset view of two coordinate systems that have undergone rotation with respect to each other.

FIG. 5 and FIG. 5a, 5b and 5c are offset views of two coordinate systems that have undergone translation and rotation with respect to each other.

FIG. 6 is a flow chart with respect to determining the same point P at two different times in an internal coordinate system to the body.

FIG. 7 is a side view of a preferred embodiment of the present invention.

FIG. 8 is a flow chart with respect to determining the location of a point P in an internal coordinate system with respect to an external coordinate system.

FIG. 9 illustrates a flow chart of a data accessing operation according to an embodiment of the present invention.

FIG. 10a and 10b illustrates a viewing and transformation process according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1a, 1b, and 1c there is shown a fiducial implant 10 for the human body that is detectable by an imaging system. The fiducial implant comprises a first portion 12 and a second portion 14. The first portion 12 is configured to be detected by an imaging system (when place beneath the skin.) The second portion 14 is configured for fixed attachment to the bone beneath the skin without fracturing the bone. The first portion 12 is sufficiently large and comprised of a material for detection by an imaging system and sufficiently small to provide minimal distortion of the skin when placed at an interface between the skin and the bone. First portion 12 also has at least a portion which is spherical and defines a surface (such as indentational) for cooperating with a tool for securing the second portion 14 to the bone. Additionally, the placement of three fiducial implants 10 into a portion of anatomy of the human body allows of the recreation of a particular image slice of the portion of the anatomy taken by an imaging system in order to duplicate images taken at the first time period, that is, at the initial examination. This provides a doctor with the ability to accurately follow the progress of treatment on selected slices representing the anatomy of interest.

Moreover, the existence of three fiducial implants 10 allows a target (a tumor for instance) to be identified relative to an external coordinate system. The portion of anatomy with the target may then be operated on, for instance, robotically, or precisely irradiated.

To allow for the accurate comparison of image slices from at least two distinct periods of time, the three fiducial implants 10 are first implanted into a body of a patient at a desired region of interest. The patient is then placed in an imaging system and images of a series of cross-sectional slices are obtained that include, for example, the volume of the tumor which is the primary target of interest. From the imaging data obtained, the three fiducial implants are located and an internal coordinate system is defined with respect to them. If it is so desired, the image data may be further reformatted to show image slices whose direction is different from that obtained originally during the imaging period. Depending on the diagnostic information that these image slices reveal, appropriate decisions with regard to surgery, chemotherapy or radiation therapy on a patient may be made. The imaging data can also be used from several different types of images, such as CT, PET or NMR to obtain the same view of the anatomy but with different qualities stressed.

If it is decided to obtain further imaging data at a later time, then the patient is returned to the imaging system and the procedure for obtaining image data is repeated. The fiducial implants 10 are located with respect to the second imaging session and the same internal coordinate system is defined relative to the implants 10. Once the same internal coordinate system is defined with respect to the second imaging session, the translation and rotation of the internal coordinate system and the images with it is determined with respect to the coordinate system established at the first imaging session. See FIGS. 3, 4 and 5 for example. An image slice identified from the first imaging session that is to be used for diagnosis, is recovered from the second imaging session. The two image slices, one from the first image session and one from the second image session, are then compared to determine what changes, if any, have occurred in the anatomy of the patient.

More specifically, a 3-dimensional noncollinear coordinate system requires three distinct noncollinear points to be fully defined. If there are more than three identifiable points, the system is over-determined and three points have to be chosen to define the coordinate system. If there are less than three identifiable distinct points, the system is undetermined and a position relative to the one or two identifiable points will not be defined.

The known location of three distinct points identifies a plane upon which an orthogonal coordinate system can be established. If the three points are fixed in place relative to each other over time in the body, a coordinate system can be established that is also fixed in time. The ability to define a fixed internal coordinate system to the human body over time has important ramifications. A fully defined internal coordinate system that is fixed in place over time with respect to some location in the body permits comparison of subseq