Targeting system and method of targeting

A targeting system, which provides an adjustable optical assembly, for use with imaging systems having a penetrating beam source, a penetrating beam receiver. The optical assembly has a targeting marker in the path of a penetrating beam emitted by the source. The targeting marker is at least partially opaque to the penetrating beam emitted by the source, and the targeting marker indicates a targeting point on a target axis. The optical assembly further includes a sensible targeting beam device that is capable of providing a sensible targeting beam coaxial and collinear with the target axis. In addition, there is provide a method of aligning the targeting system, such as the system described above, and a method of targeting an area of interest. One advantage of the system and method is that it requires only a two point alignment.

BACKGROUND OF THE INVENTION

The present invention relates generally to systems and methods of targeting. For example, the present invention may be used to target areas residing behind a surface.

In the prior art, U.S. Pat. No. 5,320,111 and U.S. Pat. No. 5,316,014 disclose a method and apparatus for locating and guiding a biopsy needle with respect to an X-rayed specimen having a tumor to be engaged by the needle. Intersecting laser beams are utilized to mark the location of the tumor and to guide the biopsy needle in a vertical path. The laser beam source is movable in orthogonal paths while compensating means redirect the beams to maintain them within a target area or eliminate any parallax. That is, the angular position of the laser light beam is adjusted to different angles at different coordinate positions to have the needle follow along a portion of a straight line path from the X-ray point source through the lesion and to the X-ray film. Thus, the needle tip should not be displaced to one side of a small lesion.

Such prior art systems and methods have disadvantages. For instance, they are difficult to accurately and quickly calibrate. An improved targeting system and method of targeting is disclosed in pending U.S. patent application Ser. No. 09/792,191 filed Feb. 22, 2001 entitled “Targeting System And Method Of Targeting” and assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference.

SUMMARY OF THE INVENTION

The present invention includes a targeting system, which provides an adjustable optical assembly, for use with imaging systems having a penetrating beam source, a penetrating beam receiver. The optical assembly has a targeting marker in the path of a penetrating beam emitted by the source. The targeting marker is at least partially opaque to the penetrating beam emitted by the source, and the targeting marker indicates a targeting point on a target axis. The optical assembly further includes a sensible targeting beam device that is capable of providing a sensible targeting beam coaxial and collinear with the target axis.

In addition, the present invention includes a method of aligning the targeting system, such as the system described above, and a method of targeting an area of interest.

One advantage of the system and method of the present invention is that it requires only a two point alignment.

DETAILED DESCRIPTION OF THE INVENTION

The targeting system is used in conjunction with a real-time imaging system. The imaging system may be a fluoroscopic X-ray imaging system, a film (or equivalent recording media) X-ray imaging system, a NMR (nuclear magnetic resonance also known as MRI) imaging system, a CAT (computer assisted tomography also known as CT) imaging system. All of the aforementioned imaging systems have a source of penetrating electromagnetic radiation beam and a device which receives and interprets the resulting penetrating radiation image. The targeting system may also be used with systems using other forms of penetrating radiation such as ultrasound radiation. The targeting system may be in an embodiment that is attachable to an existing image system or in an embodiment which can be included into the imaging system.

By way of background, reference may be made toFIG. 4of the above-referenced application Ser. No. 09/792,191 which is a schematic perspective view of part of a targeting assembly which is included in a targeting system. That targeting assembly is a three point alignment system for use with the C-arm shown in that application for mapping the shape of the conical X-ray beam. That targeting assembly features pivotal movement about axis25C shown inFIG. 4of application Ser. No. 09/792,191, reciprocating movement along axis25A and along axis25C and pivotal movement about axis25A.

The embodiment of the targeting system of the present invention includes an optical assembly, the associated motion actuators, the associated electronic elements and other associated operational control devices such as, but not limited to, an infrared based remote controller. The optical assembly is adjustable. The optical assembly has a targeting marker in a path of a penetrating beam provided by the radiation source. The targeting marker is at least partially opaque to the penetrating beam emitted by the radiation source, and the targeting marker indicates a targeting point on a target axis. The optical assembly further includes a sensible targeting beam device capable of providing a sensible targeting beam coaxial and coincident with the target axis. In addition, the present invention includes a method of aligning the targeting system with the particular imaging system, and a method of targeting an area of interest. One advantage of the optical assembly of the present invention is that it requires only a two point alignment.

Referring now toFIG. 1, the targeting system of the present invention is illustrated with a fluro-scopic X-ray imaging system10including a c-arm12, a penetrating beam or X-ray source14and a penetrating beam receiver or image intensifier16. The targeting assembly of the invention is designated20inFIG. 1.

FIG. 2is a plan view of the targeting assembly20looking from the source14toward assembly20.FIG. 6is a plan view of the targeting assembly20looking from the receiver16toward the assembly20. The targeting assembly20comprises an optical assembly30carried on a frame structure32and various drives for moving components of the assembly in various directions as will be described. Frame32includes a first component34mounted at a fixed location in system10and a second component36carried by component34and which, in turn, carries optical assembly30.

Optical assembly30includes a targeting beam steering mirror40mounted on a shaft42or the like rotatably mounted in a rim component44which, in turn, is rotatably mounted on frame component36. A disc46of material allowing transmission therethrough of the penetrating beam, i.e. X-ray, is located within rim44. A targeting beam50, in this illustration a laser beam, is provided by a targeting beam source52and is directed by a cornering mirror54through an opening in rim44to the steering mirror40. A targeting marker or reticle60is provided in optical assembly30and may be two perpendicular or orthogonal wires of X-ray opaque material extending across rim44in a plane parallel to the plane of disc46.

The optical assembly30is moved along a first linear path in what is designated the X-axis translation inFIG. 1and indicated by arrow70inFIGS. 2,5,6and7. This movement is provided by a linear actuator or the like designated72inFIGS. 2 and 6. The optical assembly30is moved along a second linear path in what is designed the Y-axis translation inFIG. 1and indicated by arrow76inFIGS. 2,3,5,6,7and9. This movement is provided by a linear actuator or the like designated78inFIGS. 2,3,56,7and9. The optical assembly30is rotated about an axis and what is designated the beta rotation inFIG. 1and indicated by arrow82inFIGS. 2,5,6and7. This movement is provided by the drive arrangement designated84inFIGS. 2 and 5which can comprise, for example, a stepper motor and gear arrangement. The component42on which steering mirror40is mounted is rotated about an axis and what is designated the alpha rotation inFIG. 1and indicated by arrow86inFIGS. 6 and 7. This movement is provided by the drive designated88inFIGS. 6 and 7.

The present invention is illustrated by the following description of the operational geometry and calibration. For purposes of the following description, the distance h is defined inFIG. 1, the laser-mirror incident point is on steering mirror40, the reticle is the targeting marker60, and the mirror-cross-laser set is the mirror40, reticle60and laser set.

Geometry for the Saber Source with Known h′ (2 Point Calibration):

FIG. 10depicts the geometry of the optical path of a system with three mirror-cross-laser set positions.

FIG. 11depicts the geometry of a single mirror-cross-laser position, where:

MN stands for the normal line of the mirror. The rotation of MN is expressed as α and β.

MI stands for the reflection ray. The rotation of MI is expressed as α′ and β′.

R stands for the reticle.

Note: Because PIN is parallel with the laser incident ray and because MN intersect the angle between the incident ray and reflection ray, so NI=MI.

h′=H+dH⁢h,and,ONE translation-rotation sets of the x-y translational steps (nx, ny) for the reticle and the rotational steps (nα, nβ) for the mirror.
Assume: No offset at initial rotation position, i.e., α0=0, β0=45°.
Find: The system offset (x0, y0).
Conclusion:

Derivation: The geometry of an ideal case is shown inFIG. 12,

Because h is known, and

In addition, apply law of cosines to triangle INO′,

Now looking for β0where x=x0+Δx=0, such that

When we consider the distance between laser-mirror incident point and the reticle, we will have a different h (see, e.g.,FIG. 13).

FIG. 13shows that the origin (x0, y0) is still the same as the ideal case. However, the system height h is a little shorter than the h in the ideal case.

Let denote the new h as h′. In addition, let distance between any two calibration points on reticle plane be presented as lij, and the distance between two corresponding cross on image intensifier be presented as Lij, then