X-ray or gamma ray systems or devices – Accessory – Testing or calibration
Reexamination Certificate
2002-04-29
2004-08-17
Bruce, David V. (Department: 2882)
X-ray or gamma ray systems or devices
Accessory
Testing or calibration
C378S162000, C378S164000
Reexamination Certificate
active
06776526
ABSTRACT:
The invention relates to a method for navigation-calibrating x-ray image data and to a height-reduced calibration instrument. In particular, the present invention relates to the field of computer-assisted surgery and image-assisted surgery, wherein a medical navigation system comprising a screen output is available to the surgeon carrying out the treatment, to guide and/or assist him during surgery to be performed.
Within the framework of such medical navigation, it is additionally possible to fall back on information determined from x-ray images produced in situ, wherein on the one hand additional and important anatomical information from the x-ray image can then be introduced into navigation image support, and on the other hand the option also exists of updating registration of the patient in the navigation system, with the aid of the x-ray images.
Such a system is known for example from EP 1 153 572 A1.
Further documents dealing with the technical background of the above-cited “x-ray navigation” are U.S. Pat. Nos. 5,799,055, 3,577,160, 6,118,845, 5,784,431, 5,967,982 and 5,772,594.
Navigation of this kind, assisted by x-ray images, can be used in various medical surgery, for example spinal cord operations and within the framework of accident surgery. This requires both suitable software in the navigation system and a calibration instrument to enable navigation on registered/calibrated image data using an x-ray device, for example a C-arc.
An example of a conventionally used calibration instrument can be seen in the perspective representation in
FIG. 2
; a schematic vertical section of this instrument is shown in FIG.
3
. This conventional calibration instrument C′ consists of a fixing means
12
, with the aid of which the instrument can for example be attached to the image recorder of a C-arc x-ray device. This image recorder (detector) is only shown in outline in
FIG. 3
(reference numeral
11
). A first support
13
and a second support
14
are attached to the fixing device
12
, spaced successively, and circumscribe plates on which localization information has been placed, i.e. for example, structures in the two plates such as tungsten spheres, line structures, etc., which are used both to rectify the image and to orientate the image. Such a localization structure, i.e. a tungsten sphere, is shown from each of the plates shown in
FIG. 2
, by the reference numeral
18
(support
13
) or
19
(support
14
). These structures have a defined arrangement, and the supports and/or plates are also arranged at a defined distance from each other, to enable a virtual radiation source to be calculated which in
FIG. 2
is provided with the reference numeral S. The larger the distance between the planes or supports
13
,
14
, the more accurately the radiation source can be calculated and the more accurate the navigation on the registered image data.
FIG. 2
shows what such an image, i.e. the generated x-ray image
10
, could look like. The x-rays travel from the virtual radiation source S through the part of the body to be imaged, a part of a spine
17
being shown in FIG.
2
. The x-rays then penetrate the first and second plate on the supports
14
,
13
of the calibration instrument C′, so as to ultimately provide the image of the spine, together with images
18
′,
19
′ of the localization structures, on the x-ray image
10
. Since the multitude of localization structures for a particular irradiating angle always accurately provides an assignable image arrangement, the location of the virtual radiation source S can be exactly deduced from the images of these structures. This provides exact knowledge of the orientation of the x-ray image produced.
Sensors and/or markings
15
are additionally situated on the calibration instrument C′, which can be LEDs, reflective markers or magnetic sensors, and which enable a medical navigation system to determine the spatial position of the calibration instrument C′ with the aid of software. The spatial position of the x-ray image itself can then be determined from the information on the spatial position of the calibration instrument and on the orientation of the x-ray image, and integrated into navigation.
FIG. 3
additionally shows, with the reference numeral
16
, the connection between the first support
13
and the second support
14
, this being a rigid and fixed connection; the two supports
13
,
14
are connected to each other as one piece.
When using such calibration instruments within the framework of x-ray navigation, there currently exists the problem that the height of the calibration instrument due to the two supports comprising calibration information, attached at a fixed distance from each other, considerably restricts the “clear width” of the x-ray device. When a C-arc is used, the calibration instrument is sat for example on the image detector and considerably shortens the distance between it and the x-ray generator. This is particularly critical in spinal operations in the lumbar area, but also in hip operations, such that x-ray navigation often has to be foregone in such cases.
It is the object of the present invention to provide a method for navigation-calibrating x-ray image data and a calibration instrument which overcome the above problem; in particular, the option should be provided of forming the clear width of an x-ray device comprising a calibration instrument sufficiently large, to allow x-ray navigation to also be used in hitherto excluded cases.
This object is solved by a method in accordance with the enclosed claim
1
and by a calibration instrument in accordance with claim
8
. The invention further relates to a program in accordance with claim
15
and to a computer program storage medium in accordance with claim
16
. The sub-claims define preferred embodiments of the invention.
A method in accordance with the invention for navigation-calibrating x-ray image data comprises the following steps:
an x-ray image is produced without the patient by means of an x-ray device into the radiation path of which a calibration instrument is introduced which can be positionally detected and tracked in a medical navigation system;
the x-ray image without the patient is registered in the navigation system with the aid of localization structures arranged on at least two spaced supports of the calibration instrument, and images of the same on the first x-ray image;
a support, together with its localization structures, is removed from the calibration instrument;
a patient x-ray image is produced;
the calibration information from the images of the localization structures of the remaining support on the instrument are compared for the two x-ray images, and calibration is corrected if there is an insufficient correspondence between the images.
The particular advantage of the method in accordance with the invention lies in removing at least one support, together with its localization structures, from the calibration instrument and then compensating for the lack of information thus arising. These measures enable x-ray images to be navigation-calibrated even in cases where a very large clear width or a very large distance between the x-ray generator and the x-ray detector is required, i.e. for example in spinal operations in the lumbar area or also in hip operations. For the first time, the invention shows a way in which, by suitably designing the calibration instrument and suitably using it within the framework of the method in accordance with the invention, x-ray navigation can also be used in operations for which such assistance has hitherto not been possible.
In an embodiment of the present invention, the x-ray image without the patient is produced first, to base-calibrate the x-ray image. Using such a so-called “blank shot” with the two supports of the calibration instrument, the image orientation and/or location of the virtual radiation source for the x-ray device used, which is preferably a C-arc x-ray device, can be determined even before the image with the part of the patient'
BrainLAB AG
Bruce David V.
Renner , Otto, Boisselle & Sklar, LLP
Thomas Courtney
LandOfFree
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