X-ray or gamma ray systems or devices – Specific application – Computerized tomography
Reexamination Certificate
2000-03-16
2002-08-27
Porta, David P. (Department: 2882)
X-ray or gamma ray systems or devices
Specific application
Computerized tomography
C378S205000, C600S429000
Reexamination Certificate
active
06442230
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a computed tomography device which includes a gantry provided with an examination opening, a position measuring system for measuring the position of the gantry.
2. Description of Related Art
A computed tomography device of this kind is described in European patent application No. 98202074.5.
The patient to be examined is accommodated on an examination table. During the examination the patient on the examination table is moved partly into the examination opening of the computed tomography device. The computed tomography device includes an X-ray source for irradiating the patient to be examined by means of X-rays from different directions. The computed tomography device also includes an X-ray detector for the detection of X-rays, having traversed the patient, from different directions. The X-ray source then irradiates the patient from different directions and the X-ray detector picks up density profiles of the patient for the various directions. A reconstruction unit extracts slice images of the patient from the density profiles.
During the examination the physician introduces a surgical or interventional instrument, such as biopsy needle, into the body of the patient. The surgical instrument is provided with transmission elements such as diodes emitting light or infrared radiation (LEDs or IREDs). The cited European patent application describes a computed tomography device which includes a position measuring system with a camera unit mounted on a mast. The position measuring system comprises the camera unit and a computer. The computer is connected to the camera unit so that the camera unit can supply the computer with image signals. The camera unit picks up images of the transmission elements on the surgical instrument from different directions and a computer computes the position of the surgical instrument relative to the camera unit from said images. Furthermore, transmission elements, for example LEDs or IREDs again, are also provided on the gantry of the computed tomography device. The camera unit also picks up images of the transmission elements on the gantry and the computer computes the position of the gantry relative to the camera unit from these images. The position of the gantry is related directly to the position of the cross-section of the patient of which a slice image is formed in the relevant position of the gantry. It has been found that the relationship between the gantry positions measured by the camera unit and the position of the cross-section of the patient which is imaged in the slice image can be accurately calibrated. The transformation of positions in said cross-section to corresponding positions in the slice image can be derived from the calibrated relationship between the position of the gantry and the position of the cross-section of the patient imaged in this position of the gantry. On the basis of the positions, measured by the camera unit, of on the one hand the surgical instrument and on the other hand the position of the gantry, also measured by the camera unit, and the position, derived therefrom, of the cross-section of the patient which is reproduced in the slice image, it is possible to reproduce, using the transformation, also the corresponding position of the surgical instrument in the rendition of the slice image. The physician, for example a surgeon or radiological interventionist, can thus track the surgical instrument within the body of the patient in the image without having a direct view of the instrument.
The computed tomography device described in the cited European patent application is provided with a position measuring system with a camera unit which is mounted on a mast. The mast is connected to the examination table. It is a drawback of the described computed tomography device that the mast could interfere with the accessibility of the patient during the examination. Moreover, it may occur that the physician stands between the camera unit and the gantry during the examination, so that the light or infrared radiation emitted by the transmission elements on the gantry is intercepted by the physician. The determination of the position of the gantry by the camera unit could thus unintentionally be interrupted.
Citation of a reference herein, or throughout this specification, is not to construed as an admission that such reference is prior art to the Applicant's invention of the invention subsequently claimed.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a computed tomography device which is provided with a position measuring system and in which the camera unit of the position measuring system practically does not interfere with the execution of the examination.
This object is achieved by means of a computed tomography device according to the invention in which the camera unit is suspended from a suspension point situated above the examination opening.
The camera unit is suspended from a suspension point which is situated above the examination opening, i.e. the suspension point is situated at a level above the floor of the space in which the computed tomography device is accommodated which is higher than the level of the examination opening above the floor. This is achieved, for example by situating the suspension point above the gantry, i.e. at a greater height above the floor. The camera unit itself can be arranged in various positions; for example, the camera unit is situated at a level which is higher than that of the gantry, or at a level which is higher than that of the examination opening, or at a level which is higher than the center or higher than the lower side of the examination opening. Because the camera unit is suspended from a suspension point above the examination opening of the computed tomography device, for example from the ceiling of the examination room in which the computed tomography device is installed, the mast can be dispensed with. Because of the absence of a mast, the accessibility of the patient during the examination is enhanced. As the camera unit is suspended above the computed tomography device, moreover, (unintentional) blocking of the line of sight between the camera unit and the gantry, notably the transmission elements on the gantry, by the physician during the treatment is avoided.
Most commercially available camera units which are suitable for use in conjunction with a computed tomography device in order to measure the positions of the surgical instrument and of the gantry have a sensitivity range which is comparatively small; the sensitivity range of inexpensive camera units amounts to approximately one cubic meter. The sensitivity range of the camera unit is to be understood to mean that part of the space in which the camera unit picks up images of the emitter elements which are sufficiently accurate so as to enable the extraction of reliable results concerning the positions of these emitter elements. Generally speaking, the examination opening of the computed tomography device is shaped more or less as a cylindrical tunnel. For example, the tunnel has a width of between 40 cm and 90 cm and also a length of from approximately 40 cm to 90 cm. It has been found that when the camera unit is suspended above the examination opening and in front of one of the tunnel entrances, practically the entire interior of the tunnel will remain within the sensitivity range of the camera unit. This enables the use of a comparatively inexpensive camera unit, accurate results concerning the position of the surgical instrument being obtained nevertheless.
It also has been found that the angle of aperture of the camera unit can be readily adjusted to the operating zone in which the surgical instrument is moved. The angle of aperture of the camera unit is the range of directions wherefrom the camera unit can accurately pick up images of the transmission elements on the gantry and on the surgical instrument.
When the transmission elements on the gantry are arranged near the entrance of the tunnel, the trans
Proksa Roland
Verbruggen John A. M.
Wilting Jantje E.
Barber Therese
Koninklijke Philips Electronics , N.V.
Porta David P.
Vodopia John
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