Patent Application
20130329217
This invention relates to a system and method for aligning a transport mechanism for moving a bed, table, or imaging device in an imaging system having an imaging plane, and more particularly, to a laser system having a target element and a reflective element for detecting the position of a laser beam wherein a position of the bed is adjusted based on detected laser beam positions.
It is important that a bed used to accommodate or hold an object to be scanned by an imaging system be correctly aligned with an imaging plane of the system so that accurate long-axial field of view (FOV) scans are obtained. In a computed tomography (CT) imaging system 100, for example, a gantry 10 (see
The bed 14 in the imaging system 100 is aligned relative to X, Y, and Z translation directions and pitch 15, yaw 17 and roll 19 rotation angles about three perpendicular axes. In many imaging systems, a manual multi-step procedure is used wherein a bed alignment tool, protractor, machinist square and other tools or devices are used to align the bed 14. In this procedure, specific parameters for bed alignment are manually checked, and if the bed 14 is not aligned, adjustments are made to align the bed 14 whereupon bed alignment is then rechecked. The process of checking bed alignment, making adjustments to the alignment and rechecking the alignment is then repeated until a desired alignment is achieved. However, this results in an iterative process which is time consuming and takes experienced personnel approximately six hours to complete.
A system for aligning a bed of an imaging system with an imaging plane is disclosed. The system includes a laser device which generates a laser beam and a target element having a target detecting surface and a collimator hole, wherein the laser beam is transmitted through the collimator hole. The system also includes a reflective element which receives the laser beam. The reflective element includes a reflective detecting surface for detecting a first position of the laser beam wherein at least one first parameter of the bed is adjusted until the laser beam is positioned on a first center portion of the reflective detecting surface. In addition, the laser beam is reflected to the target detecting surface to detect a second position of the laser beam wherein at least one second parameter of the bed is adjusted until the laser beam is positioned on a second center portion of the target detecting surface to orient the bed substantially perpendicular to the imaging plane.
Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. In the description below, like reference numerals and labels are used to describe the same, similar or corresponding parts in the several views of
Referring to
In accordance with the invention, a laser beam 50 generated by the laser device 32 is first aligned with the Z-axis. The laser beam is then transmitted through the collimation hole 48 to form a collimated laser beam 52. The collimated laser beam 52 then impinges on the reflective center portion 40 and forms a first beam spot 54 on the first surface 44. If the first beam spot 54 is not located on the reflective center portion 40, an offset is indicated in either or both the X and Y directions, depending on the location of the first beam spot 54. The offset is measured by using the first cross hair pattern 38. Using the measured offset, the bed 14 is then correspondingly adjusted in either the X direction or the Y direction, or both the X and Y directions, as needed, so that the first beam spot 54 impinges on the reflective center portion 40 as shown in
The laser beam 52 is then reflected by the reflective center portion 40 back to the target element 34 thus forming a second beam spot 56 on the second surface 47. If the second beam spot 56 is not located on the center portion 49 of the second cross hair pattern 46, as offset is indicated. The bed 14 is then correspondingly adjusted so that the second beam spot 56 impinges on the center portion 49. This ensures that the bed axis (i.e. the Z axis) and the first surface 44 are substantially perpendicular to each other thus adjusting pitch and yaw rotation angles to zero. The second beam spot 56 then coincides with the collimation hole 48. In one embodiment, the laser device 32 utilizes a non-amplified, light emitting diode (LED) based laser source such that the laser beam 50 is not affected by the back reflection into the collimator hole 48. Further, adjustment of the second beam spot 56 may be performed dynamically by tracking the position of the second beam spot 56 on the second surface 47 as the bed 14 moves.
Referring to
Use of the invention results in a bed alignment process that is faster, more accurate and more reliable. In particular, the system 30 has resulted in a reduction of the time needed to align the bed 14 from approximately six hours to approximately five minutes. Further, tests have shown that the system 30 reduces measurement error by approximately one half. In addition, accuracy is improved to approximately ±0.031 degrees from approximately ±0.15 degrees.
Therefore, the system 30 provides a collimated, double targeted, reflective (CTDR) laser system for enabling alignment of a bed used in a medical imaging system. The CDTR system is relatively low cost and easy to assemble. In addition, the system 30 provides instant feedback during use since the location of second beam spot 56 on the second surface 47 of the target element 34 is readily observable as the bed 14 is moving. Further, the CDTR system enables the calibration of five degrees of freedom (i.e. translation X and Y directions and pitch, yaw and roll rotations if double sources are used) using a single apparatus.
Referring to
While the invention has been described in conjunction with specific embodiments, it is evident that many alternatives, modifications, permutations and variations will become apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended that the present invention embrace all such alternatives, modifications and variations.
