Description:BACKGROUND
The present invention relates a navigation system that organizes the images of the spine by combining orthogonally taken one lateral X-ray image and one anteroposterior X-ray image, in 3D space to represent actual 3D positions or volume or arrangement. Further it relates to integrating said arrangement with an infrared optical tracking system to create a precise spatial map in said 3D virtual image, helping the operator or user of said system to precisely locate a surgical probe or tool in and around the spine of a patient for minimally invasive spine surgeries.
The invention relates to a surgical navigation system and, more particularly, to a navigation system and method for minimal invasive surgeries (MIS) of the spine. MIS is done through small cuts or incisions that are considerably smaller than incisions used in traditional open surgical methods. For example, in an ordinary spinal surgery the incision is about 9 to 20 cm, but an MIS incision length may be in a range of about 2 to 4 cm. As a result of the smaller incision, MISs are generally less invasive than traditional methods, which minimizes trauma, reduces postoperative pain, promotes early mobilization, shortens hospital stays, and speeds rehabilitation.
The major downside of MIS is that the small incision reduces a surgeon's ability to view and access the anatomy of complex organs like the spine. For example, in MIS of the spine, limited visibility and access to the parts of the spine like vertebrae and different tissues around it, may increase the complexity of assessing operation sites for proper implant positioning, reshaping of bones and management of surrounding tissues. As a result, accurate surgeries and placement of implants may be more difficult. To overcome these problems, methods like surgical navigation and use of specially designed, downsized instrumentation and complex surgical techniques are employed. Such techniques, however, typically require a large amount of specialized instrumentation, a lengthy training process, and a high degree of skill. Moreover, current surgical navigation systems are complex and require continuous exposure to the X-ray radiation in order to visualize the navigation space of interest in and around the spine of a patient. Longer exposure to the X-radiation by the patient as well as healthcare professionals is undesirable. Therefore, a need exists for a surgical navigation system that can replace the direct visualization in minimally invasive surgery and/ or the long-term exposure in the X-rays based navigation systems.

DESCRIPTION OF THE DRAWINGS
The drawings herein are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description to explain principles of the invention.

FIGURE 1: Illustration of an embodiment of an X-ray based surgical navigation system according to the present invention. The different components of said system are identified with numbers and a general scheme of operative is depicted.

FIGURE 2: Illustration of an infrared optical tracker [12] with a strip with X-ray opaque fiducial markers [13] used with said system. The optical tracker [12] is used for aligning optical cameras [16] to the position of spine of the patient [11] to be operated. The strip with X-ray opaque fiducial markers helps to exactly align the position of spine of said patient in X-ray images. Since said optical tracker and said strip are attached to each other, the optical cameras [16] can generate the exact position of optically steerable surgical probe [15] vis-à-vis the fiducial markers [13] in the 3D organized X-ray images [18] and the optical tracker fixed on the spine on said patient. And the whole system creates a 3D virtual image or arrangement with exact location of fiducial markers and the location of said surgical probe for the healthcare professional to navigate in and around the spine of said patient [11].

DESCRIPTION OF THE INVENTION
Herein, an X-ray based surgical navigation system is disclosed that requires only two X-ray images of the spine of a patient to create a 3D organized virtual image or volume or arrangement, which in a synchronous action with an infrared optical tracking system provides high quality, economical and safe operating environment for the MIS of spine and can also be used in other surgical procedures wherein X-ray image-based information can be used. Some preferred embodiments of the invention are illustrated in the drawings and they do not restrict the general utility of the invention in any way.
In the art, a general operation of a surgical navigating system is well known and is not further described here. Those systems are based on 3D virtual images or volume or arrangement created from a large set of X-ray images taken from a C-arm machine and then computationally processed to create the 3D images or volume or arrangement. Those systems required many X-ray images at different angles in different views to create the final 3D images or volume or arrangement. The downside of this image generation method is that the patient as well as the operators are exposed to large amounts of X-radiation. Further, in resource poor settings these methods are not feasible being expensive and time consuming.
In an embodiment of the disclosed invention of an X-ray based surgical navigation system a patient [11] to be operated for a spinal cord surgery is placed on an operating table [10] as shown in FIGURE 1 in face down prone position. His spinal cord is highlighted with a marker if required. An infrared optical tracker [12], with a strip having three or more X-ray opaque fiducial markers at one end [13] is placed or fixed on the patient’s spinal cord so that said fiducial markers are configured to one or more vertebrae of spine of said patient [11] above the skin.
In another embodiment of the disclosed invention, an optical tracking system [16] is configured to receive positional data from said optical tracker [12] and help navigate an optically steerable surgical probe [15] in and around the spine of said patient [11].
In further embodiment of the disclosed invention, an X-ray imaging system [14] is used for taking a lateral X-ray image of the spine of said patient [11] with said fiducial markers [13], and recording the positional spots are made by said fiducial markers [13] in said lateral X-ray image.
In another embodiment of the disclosed invention, said X-ray imaging system [14] is used for taking an anteroposterior X-ray image of the spine of said patient [11] with said fiducial markers [13], and recording the positional spots are made by said fiducial markers [13] in said anteroposterior X-ray image.
In yet further embodiment of the disclosed invention, a computer [17] is loaded or provided with lateral and anteroposterior X-ray images of the spine of said patient with unique positional spots created by said fiducial markers [13], to enable a computer software [17] to generate a virtual 3D image arrangement [18] from said lateral and anteroposterior X-ray images. Herein, said computer software aligns said lateral and anteroposterior X-ray images to each other relative to said positional spots [13], such that a virtual 3D image [18] is computed from the said 2D X-ray images of the spine taken orthogonally [14] to each other.
In yet another embodiment of the disclosed invention, using said surgical probe [15] to navigate the space in and around the spine of said patient for operative purpose based on the relative position of said surgical probe [15] against said optical tracker [12] and said tracker having aligned to the positional spots [13] in said virtual 3D image of the spine [18]; and achieving desired any minimally invasive surgical correction of the spine using said surgical probe [15] by monitoring its movement in and around the spine by visualizing it in said 3D virtual image [18].
In another embodiment of the disclosed invention, said optical tracker [12] fixed to said strip with fiducial markers or positional spots [13] is a novel part of the invention disclosed as illustrated in FIGURE 2. The spatial relations of said optical tracker to said fiducial markers or positional spots and then with the location of said optically steerable surgical probe [15] in said virtual 3D image of the spine is unique that creates said X-ray base surgical navigation system.
In additional embodiments of the disclosed invention, said X-ray based surgical navigation system wherein said fiducial markers are made up of X-ray opaque materials like aluminium, copper, or ceramic chips. The said system wherein said strip attached to said tracker is made up of rigid X-ray lucent material like acrylic, carbon fibre, or glass fibre. The said system wherein said tracker provides exact location of said fiducial markers on the body of said patient above the spine. The said system wherein said tracker has three or more infrared sensitive tips. The said system wherein said surgical probe has one or more infrared sensitive tips. The said system wherein said X-ray images are stored in digital format. The said system wherein said surgical probe is any surgical tool or device or implant used in spinal surgeries. The said system wherein said surgical probe, said infrared optical tracker and said positional spots help create a virtual space in and around the spine of said patient helping the operator to precisely identify the location of said surgical probe in and around the spine for operative purposes. The said system wherein said X-ray images are taken with an X-ray or C-arm X-ray machine. The said system wherein said infrared optical tracker and said surgical probe are tracked by infrared cameras creating a tracking image that is aligned with said virtual 3D image with a computer with help of said positional spots available in said virtual 3D image. The said system provides precise 3D special information or arrangement to the operator to navigate said surgical probe in and around the spine for surgical procedures. The said system wherein a special resolution from 2 mm to 5 mm is achieved in and around the spine.
In another embodiment of the disclosed invention, said lateral and anteroposterior X-ray images of the spine of said patient are registered or converted to single coordinate system to create a 3D image or volume of the spine from 2 or more images taken at different axes. This registration is done automatically by the computer software with the help of said strip of fiducial markers. which creates unique spot patterns in said X-ray images and said computer software from their locations adjusts the size of said X-ray images to each other, creating a 3D image or volume or arrangement. This 3D volume or arrangement is then further aligned to the said optical surgical probe with the help of said optical tracker fixed to said strip of fiducial markers.
, Claims:WE CLAIM:
A navigation system for assisting spinal surgery comprising:
an infrared optical tracker with a strip having three or more X-ray opaque fiducial markers at one end;
attaching said tracker to a patient so that said fiducial markers are configured to one or more vertebrae of spine of said patient;
an optical tracking system configured to receive positional data from said tracker and help navigate an optically steerable surgical probe in and around the spine of said patient;
taking a lateral X-ray image of the spine of said patient with said fiducial markers, and recording the positional spots made by said fiducial markers in said lateral x-ray image;
taking an anteroposterior X-ray image of the spine of said patient with said fiducial markers, and recording the positional spots made by said fiducial markers in anteroposterior X-ray image;
loading of said lateral and anteroposterior X-ray images of the spine of said patient with unique positional spots created by said fiducial markers, to a computer software able to generate a 3D virtual volume or arrangement from said lateral and anteroposterior x-ray images;
aligning said lateral and anteroposterior X-ray images to each other relative to said positional spots, such that said 3D virtual volume or arrangement is computed from the said 2D x-ray images of the spine taken orthogonally to each other;
using said surgical probe to navigate the space in and around the spine of said patient for operative purposes based on the relative position of said surgical probe against said tracker and said tracker having aligned to the positional spots in said 3D virtual volume or arrangement of the spine; and
achieving a desired minimum invasive surgical correction of the spine using said surgical probe by monitoring its movement in and around the spine by visualizing it in said 3D virtual volume or arrangement..
The system as claimed in claim 1, wherein said fiducial markers are made up of X-ray opaque materials like aluminium, copper, or ceramic chips.
The system as claimed in claim 1, wherein said strip attached to said tracker is made up of rigid x-ray lucent material like acrylic, carbon fibre, or glass fibre.
The system as claimed in claim 1, wherein said tracker provides exact location of said fiducial markers on the body of said patient above the spine.
The system as claimed in claim 1, wherein said tracker has three or more infrared sensitive tips.
The system as claimed in claim 1, wherein said surgical probe has one or more infrared sensitive tips.
The system as claimed in claim 1, wherein said X-ray images are stored in digital format.
The system as claimed in claim 1, wherein said surgical probe is any surgical tool or device or implant used in spinal surgeries.
The system as claimed in claim 1, wherein said surgical probe, said infrared optical tracker and said positional spots help create a virtual space in and around the spine of said patient helping the operator to precisely identify the location of said surgical probe in and around the spine for operative purposes.
The system as claimed in claim 1, wherein said x-rays are taken with an X-ray or C-arm X-ray machine.
The system as claimed in claim 1, wherein said infrared optical tracker and said surgical probe are tracked by an infrared camera creating a tracking image that is aligned with said virtual 3D volume or arrangement with a computer with help of said positional spots available in said virtual 3D volume or arrangement.
The system as claimed in claim 1, provides precise 3D special information to the operator to navigate said surgical probe in and around the spine for surgical procedures.
The system as claimed in claim 1, wherein a special resolution from 2 mm to 4 mm is achieved in and around the spine.