Patent Application
20130064344
1. Field of Invention
This invention relates to imaging patients with computed tomography, specifically to imaging patients in the sitting or standing position, rotating the patient in front of imaging components that themselves do not rotate, with or without a therapy component.
In the early days of tomographic imaging, equipment was very time consuming to use, requiring up to an hour or more to image a patient. Medical diagnostic tomographic apparatuses originated from the concept of a stationary detector disclosed in the original Anger patents, such as U.S. Pat. No. 3,432,660 related to tomographic imaging using radioactive materials and radiation sensitive scintillation crystals. In these early days of gamma camera imaging an approach was used whereby the patient sat in front of a camera and the patient was rotated in order to generate multiple views. Such a device was described by Muehllehner and Wetzel and was also investigated by Budinger, Gullberg and Huesman in late 1960s and early 1970s and taught in U.S. Pat. No. 5,036,530. The approaches and teachings were limited to radioactive sources and were not referenced to be used with x-rays, nor was it applicable to the entire anatomy, being restricted only to the head and brain.
In addition, advanced imaging technology in medicine also was original meant for use on critically ill patients and was rarely used on outpatients. Therefore, the recumbent position was more appropriate in order to keep patients comfortable and for use on those who were comatose or could only be cared for in the recumbent position.
As imaging technology has advanced over the years, it is now at the point where CT images using x-rays can be generated in seconds. CT using x-rays has become more ubiquitous and is considered standard of care for imaging in almost every medical ailment. In the current practice of computed tomographic imaging, a kilovoltage x-ray source is paired with a means of radiation detection to acquire the data used to create images. Typically, an array of discrete detector elements will be used to detect the radiation that passes through the object being imaged. This array can have anywhere from one to 128 or more rows of detectors that can be spaced a variable distance apart. In order to acquire data over an extended length of patient anatomy, the detector array and the x-ray source are moved relative to the patient typically by moving the patient through the gantry containing the x-ray source and detector array. With modern high speed CT scanners capable of generating hundreds of very thin slice at a time, scans covering long distance of patient anatomy can be achieved in a very short time.
This approach is less than ideal because a recumbent patient requires significant floor space and also because it is less comfortable and convenient for a patient to lie down than to sit or stand. The vast majority of patients who receive an x-ray CT are imaged electively, walking in and out of the imaging facility under their power. Immobilization devices exist, such as U.S. Pat. Nos. 4,400,820, 4,481,657, 4,779,858, designed to hold patients still when lying down, and U.S. Pat. No. 5,036,530, that can hold patients still for even prolonged periods of time regardless of their position. Yet these imaging studies are still performed on recumbent patients in a room that is large enough to accommodate a recumbent patient.
Therefore it has become desirable to provide a means of performing a CT using a geometry that is more cognizant of the universality and outpatient applications of tomographic imaging, that takes advantages of the improvements that have been made in image acquisition and data processing, and that can be deployed in a minimum amount of space. This geometry involves the upright or vertical (sitting and standing) positions.
2. Background Description of Prior Art
U.S. Pat No. 4,316,091 teaches a CT scanner in which components are mounted in an apertured housing that can be deployed generally vertically, for the examination of recumbent patients, or generally horizontally, for the examination of patients seated, or standing. U.S. Pat. No. 5,042,487 teaches the use of a vertically-oriented and tiltable chair in which a patient can be imaged using a horizontally deployed CT gantry. U.S. Pat. No. 5,574,763 describes a CT having a patient support which permits a scan to be conducted of a patient with the patient in a substantially upright, but slightly tilted, position, and a control unit to maintain the gantry containing the x-ray source and detector at the same angle relative to said patient support for all positions of the patient support during a scan. U.S. Pat. No. 7,003,070 describes an upright CT scanner where an X-ray source and a two-dimensional digital X-ray detector are mounted on a rotating platform with avertical axis of rotation so as to rotate the imaging source/detector array about a patient. U.S. Pat. No. 7,224,764 describes an upright scanner where the source and detector rotates about a generally upright axis and is used to scan the spine and extremities, and U.S. Pat. No. 7,460,637 describes a similar device teaching the imaging of a patient's head and face with the patient in the sitting position and the x-ray source and detector rotating about the patient on a gantry. U.S. Pat. No. 7,224,764 describes a CT scanner that is particularly useful for scanning the spine and extremities, such as knees, and ankles, especially while the patient is in an upright position. The CT scanner generally includes a source and detector that are rotatable about a generally upright axis. The source and detector are also moved along the upright axis during rotation to perform a helical scan. Kamada et all published in 1999 on the use of a horizontal helical CT system for 3-D treatment planning and for positioning verification of patients in the seated position (Radiotherapy and Oncology 50 (1999) 235-237; A horizontal CT system dedicated to heavy-ion beam treatment Tadashi Kamadaa,*, Hirohiko Tsujiia, Jun-Etsu Mizoea, Yoshisuke Matsuokaa, Hiroshi Tsujia, Yasuhiro Osakaa, Shinichi Minoharab, Nobuyuki Miyaharab, Masahiro Endob, Tatsuaki Kanai). Shah et al. described the use of a horizontally deployed CT gantry to image a patient in the vertical position for the purposes of radiation therapy treatment planning (Upright 3D treatment planning using a vertical CT. Shah A P, Strauss J B, Kirk M C, Chen S S, Kroc T K, Zusag T W. Med Dosim. 2009 Spring;34(1):82-6). All of these approaches, although able to generate fan-beam diagnostic quality images, require a complicated gantry arrangement that can rotate about a patient, making it difficult to deploy this kind of technology in the therapy suite where the imaging device can interfere with the therapy beam.
U.S. Pat. No. 7,796,730 discloses an approach designed to solve this problem, teaching the use of a CT scanner with respect to a sitting patient for radiation therapy whereby the scanner can be removeably positioned to image the patient. When in place for imaging it obscures the treatment beam, when removed it allows the patient to be imaged. Although the patient can rotate in front of the imaging beam to generate an image, the imaging device completely surrounds the patient and must be removed, or must provide a window through it, for the patient to be treated.
So called rotating patient CT scanners are disclosed in U.S. Pat. Nos. 4,473,822; 4,961,208; 5,036,530. Patient is positioned in an upright position between x-ray source and bank of detectors. For a given vertical position of the x-ray source and the detectors, the patient is rotated 360 degrees to acquire multiple images from different angular positions of the patient. This provides the data to generate anywhere from one to many images slices through the patient depending on the number of rows of detectors employed. Once a complete rotation of the patient is finished, the x-ray source and detectors are moved together, relative to the patient, along a vertical translation axis to generate a new set of horizontal scan planes by rotating the patient again. This process is repeated until the complete area of interest is covered. This approach generates high diagnostic quality images due to the use of fan-beam technology but requires that the patient be rotated multiple times in order to achieve that quality, something that can cause undue discomfort to the patient and increase the time it takes to generate a study.
U.S. Pat. No. 6,470,068 teaches the use of the vertical position with a patient mounted on a turntable, the patient held in place using an airbag system, and a conventional CT source/detector array configuration. The system teaches the use of a cone beam technology in order to generate images quickly and cheaply with the need to rotate the patient only once. However, cone beam technology does not generate images equal in diagnostic quality to those generated by fan beam technology.
In the industrial world CT is particularly useful for nondestructively revealing the internal structure of industrial products. X-ray inspection systems for large component objects, such as those systems disclosed in U.S. Pat. Nos. 3,766,387; 4,422,177; 4,600,998; 5,119,408; and 7,760,852 use a system where an x-ray source and a beam detector system straddle a turntable on which is placed an industrial object for imaging that is rotated in front of the x-ray source and beam detector for the purposes of generating a CT dataset. For instance, U.S. Pat. No. 5,023,895 teaches an industrial CT system is provided for three-dimensional imaging that includes a three dimensional cone beam of hard radiation fixed with respect to a two dimensional scintillation detector array. The object is positioned on a turntable interposed between the radiation source and detector array. Data from two-dimensional views are stored as the object is rotated on the turntable about a fixed axis. The data is sufficient upon completion of one revolution to construct a transparent three-dimensional image of the object. A positioning encoding arrangement adjusts for variations in the object's mass density to optimize scan-compute times while enhancing image resolution. However, none of these teach the use of such a geometry for the purposes of medical imaging nor do they discuss how to generate fan beam images.
U.S. Pat. Nos. 6,649,914; 5,859,893; 5,835,561; 5,751,785; 5,729,584; 5,651,047; 5,644,612; 5,610,967 all relate to the generation of x-ray images using an inverse geometry. This geometry is characterized by a large-area scanning x-ray source and a small-area detector. The scanning x-ray source projects a rapid sequence of narrow x-ray beams through the patient and onto a small-area, high efficiency detector. The system acquires a series of overlapping small-field-of-view images that are combined electronically to generate the full image. Although this technology has been described as being used to generate CT images, it does so by rotating the x-ray source and the detector about the patient. None of the patents teach the approach of rotating the patient in front an x-ray source and the detector array instead of rotating the x-ray source and the detector array.
Therefore, although there is teaching related to the standing or sitting position for the purposes of CT fan beam imaging where the imaging components rotate about the patient, and although there is teaching related to fan-beam imaging with a rotating patient where multiple rotations of the patient are required to complete a scan, and although there is teaching related to the requirement for only a single rotation of a patient in a cone-beam imaging system, and although there is teaching related to the use of system whereby an industrial object rotates between the components of an imaging system, there is no prior art teaching the use of a nonrotating detector/array assembly imaging with a rotating patient in either the horizontal or vertical positions where only a single rotation of a patient is required to acquire fan beam images.
Thus there is a need for and novel design in a CT scanning system that provides the ability to image a patient in the standing or upright position using nonrotating imaging components whereby high quality fan beam images are acquired with a single rotation of a patient, thereby allowing a CT system to be deployed in a minimum amount of space and with a minimum amount of cost and a minimum of inconvenience to the patient. This is especially the case for the purposes of imaging a patient who is undergoing therapeutic radiation therapy.
A CT scanning system for patients is provided comprising a nonrotating x-ray source and detector array bracketing a turntable on which stands or sits the patient that is being imaged. As the patient rotates between the x-ray source and the detector array that move along the vertical axis in tandem for each angular position of the patient, imaging data is collected of the patient from multiple angles at multiple levels that are reconstructed to form computed tomographic images that cover the entire region of interest.
In a preferred embodiment the system consists of a turntable interposed between two imaging components that can support a patient sitting or standing. The imaging components consists of a detector array characterized by an array of discrete detector elements typical to modern day CT scanners, and an x-ray source, the two components able to be moved in tandem vertically up and down for each angular position of the rotating patient so as to generate overlapping small-fields-of-view whose data can be combined electronically to generate a complete data set from each angular data collection position.
In further embodiment the imaging components consist of an inverse geometry imaging system characterized by a large-area scanning x-ray source and a small-area detector, the scanning x-ray source projecting a rapid sequence of narrow x-ray beams through the patient at each angular position of the rotating patient onto a small-area, high efficiency detector so as to generate overlapping small-fields-of-view whose data can be combined electronically to generate a complete data set from each angular data collection position.
In one aspect, a method is provided for generating a CT image of a patient. The method comprises the steps of locating a patient upright or sitting on a turntable that is positioned between an x-ray source and an x-ray detector of an imaging system, rotating the patient such that the imaging beam generated by the x-ray source passes through different angular positions of the patient before reaching the detector, translating the detector array and x-ray source along a vertical axis to generate multiple images of the patient displaced in a vertical direction for each angular position of the patient, the data from all positions of the patient and all vertical positions of the x-ray source and detector array being combined to generate the CT images in a single rotation of the patient.
A further method comprising the steps of locating a patient upright or sitting on a turntable that is positioned between the two imaging components of an inverse geometry imaging system and rotating the patient while collecting data at each angular position of the patient that are combined to generate the CT images, thereby generating the equivalent of fan-beam imaging with only a single rotation of the patient.
a through
Various embodiments of the present invention are described hereinafter with reference to the figures. It should be noted that the figures are not drawn to scale and elements of similar structures or functions are represented by like reference numerals throughout the figures. It should also be noted that the figures are not intended to facilitate the description of specific embodiments of the invention. They are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. In addition an aspect described in conjunction with a particular embodiment of the present invention is not necessarily limited to that embodiment and can be practiced in any other embodiments of the present invention. It will be appreciated that while various embodiments of the invention are described in connection with computed tomographic imaging in medicine, the claimed invention has application in other industries and to imaging technologies other than computed tomography.
In a preferred embodiment of the present invention as depicted in
If the imaging system is to be used in conjunction with a therapy system (12) such as ionizing radiation as in
In a variant of the preferred embodiment as depicted in
In an additional embodiment, as depicted in
In operation using the preferred embodiment as shown in
With the imaging beam turned on, the 3-D data acquisition process begins by moving the imaging tandem along the vertical axis in fixed increments until the complete length of the region of interest is covered (
The data acquired during the imaging procedure is then parsed according to the turntable's angular position and the imaging tandem's vertical position. All of the images generated for a given vertical position of the imaging tandem when combined will provide the data required to generate, using techniques and algorithms known to those skilled in the art, a set of imaging slices through the patient corresponding to that vertical position of the imaging tandem. If a detector array with multiple rows of detectors is provided, then multiple image slices will be generated for each vertical position of the imaging tandem.
In an alternate version of the preferred embodiment, the operation is the same except that instead of translating the x-ray source in tandem with the detector array, the x-ray source is angled along the vertical axis so as to track the position of the detector array as it translates along the vertical axis.
In another embodiment employing inverse geometry imaging, indexing of the imaging tandem for each angular position of the turntable occurs only if the field of view of the imaging system is not sufficient to cover the region of interest to be imaged. If such a case exists, the imaging tandem can be indexed for each angular position of the turntable so as to cover the entire region of interest with the imaging beam for ach angular position of the turntable. This indexing can occur along the vertical, the horizontal, or both the vertical and horizontal axis as required to achieve complete coverage.
In any of the embodiments, rather the using a fixed increment for both the turntable rotation and the vertical translation of the imaging tandem, a continuous rotation of the turntable and a continuous translation of the imaging tandem can be employed. Although the algorithms for image reconstruction are different than in the fixed increment approach, such algorithms are well know to those skilled in the art.
It will be appreciated that while various embodiments are described for this invention, they are not intended as an exhaustive description of the invention or as a limitation on the scope of the invention. For instance, multiple x-ray sources or multiple detector arrays can be used to limit the amount of indexing of the imaging tandem required to achieve full coverage of the region of interest.
This application is entitled to the benefit of Provisional Patent Application 61/526,101 filed Aug. 22, 2011.
| Number | Date | Country | |
|---|---|---|---|
| 61526101 | Aug 2011 | US |
