Abstract:
The invention comprises a system and method for handling a patient in a tomographic imaging system using a plurality of imaging devices. The imaging devices each have a bore through which a patient is translated during scanning. One or more patient support structures extend from the front of the tomographic imaging system, where the patient is initially placed, through the bores of the system. The patient is translated through the bores of the system and along the patient support structures by an actuator.

Description:
TECHNICAL FIELD 
     The invention relates to multimodality medical imaging systems for viewing anatomical structures and functions of a patient, such as combined x-ray Computed Tomography (CT) and Positron Emission Tomography (PET) scanners and, more particularly, to a patient handling assembly that reduces the overall length of the system. 
     BACKGROUND OF THE INVENTION 
     Tomographic imaging devices or cameras are frequently used to assist in the diagnosis and treatment of a variety of anatomical structures and physiologic functions within the body of a subject patient, while minimizing the need for invasive procedures. Such devices typically utilize scanners that obtain data or information about such structures and functions from the patient at specified, discrete locations along the length of a patient. Using this information, the camera produces a series of images, each depicting a cross-section of the body of the patient, in a plane generally perpendicular to the length of the patient, and at specified points along the length of the patient. Combined, successive images or a substantially continuous spiral image taken along the length of a patient can yield a relatively three-dimensional view of internal organs and tissues, or at least provide a cross-sectional view of bodily structures or functions at various places on the patient. Tomographic cameras are most frequently used to view and treat organs and other tissues within the head, torso and trunk of a patient and, in particular, diagnose and treat such ailments as heart disease, arteriosclerosis, cancer, and the like. 
     Tomographic imaging cameras are often identified by the “mode” or “modality” of radiation used by their scanners to obtain patient data. Well-known scanner modalities include the X-ray Computed Tomography (CT), Magnetic Resonance Imaging (MRI), Ultrasound (ULT), Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) scanners. Camera systems which combine two or more different scanners to obtain a greater variety of imaging information from a patient are referred to as “multimodality imaging systems.” Conversely, tomographic cameras utilizing the same mode to collect imaging information are referred to as having the same modality. 
     A tomographic camera utilizes a scanner having an array of radiation detectors forming a ring or bore that surrounds a patient. The scanner gathers information along a plane defined by the detector ring, which intersects the patient substantially perpendicularly to the length of the patient. Other processors and instruments coupled to the scanner form the tomographic image, based on information received from the scanner. To obtain information at successive points along the head, torso and trunk of a patient, the patient is supported horizontally on a patient table that translates or moves the patient horizontally through the bore of a tomographic camera. 
     It is often desirable to utilize two or more adjacent tomographic scanners of different modalities, in multimodality systems, to obtain a variety of imaging information from a single traverse of a patient through multiple scanner bores. This is highly desirable as a means of increasing efficiency (by completing two or more scans in one operation), increasing the accuracy of indexing, correlating or linking multimodality images to the same location along the length of the patient (by coordinating operation of the scanners to a single, controlled movement of the patient) and reducing the labor costs otherwise associated with separate, multimodality scanning operations. 
     In general, multimodality systems include a series of scanners, each having a different modality, supported by a single housing. Each scanner obtains different information about the patient, which, when registered in combination, provides a better understanding of the patient. More specifically, multimodality cameras typically include a scanner of anatomical structures of the patient (e.g., CT, MRI and Ultrasound cameras) and a scanner of physiologic functions of the patient (e.g., SPECT and PET cameras). The series of scanners forms a relatively long bore, typically longer than the combined head and torso of taller patients and spanning the entire length of shorter patients. 
     A patient table translates the patient through the scanners in a controlled manner, providing information to the system about the position of the patient. The position information it used to register the images formed from the scanner information to the same locations along the length of the patient. Unfortunately, conventional patient tables have a patient support surface that must be long enough to extend the patient from outside the first scanner bore, beyond the outlet of the final scanner bore. As a result, the patient support surface is typically longer than the entire length of the multimodality scanner assembly. Moreover, when the patient is positioned outside the scanner bores, at the front of the scanner assembly, the portion of the patient support surface extends forward from the assembly by a distance greater than the scanner assembly itself. This configuration is required particularly if the support surface is to be used to raise and lower the patient between the level of the scanner bores and the floor. 
     The combination of a lengthy multimodality scanner bore and longer patient support surface limit the facilities in which multimodality systems can be used, increase the cost of using and storing such systems and thus limit their availability. Accordingly, there is a need for a patient table for use in a multimodality tomographic imaging system that reduces the space required for use and associated costs. 
     SUMMARY OF THE INVENTION 
     The invention comprises a system and method for handling a patient in a tomographic imaging system using a plurality of imaging devices. The imaging devices each have a bore through which a patient is translated during scanning. One or more patient support structures extend from the front of the tomographic imaging system, where the patient is initially placed, through the bores of the system. The patient is translated through the bores of the system and along the patient support structures by an actuator. 
     In one aspect of the invention, a portion of the patient support structure extending from the front bore of the system is vertically adjustable, to position the patient in alignment with the scanner bores. 
     In another aspect of the invention, the patient is drawn through the scanner bores along the patient support structure by one or more belts. 
     In yet another aspect of the invention, the patient is supported on a pallet, which is drawn through the scanner. 
     In still another aspect of the invention, a portion of the patient support structure is positioned outside the bores at the front of the system, to vertically position the patient in alignment with the bores. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic side view of a multimodality medical imaging system incorporating the present invention; 
     FIG. 2 is a front view of the multimodality medical imaging system of FIG. 1; 
     FIG. 3 is side view of the multimodality medical imaging system of FIG. 1, illustrating the imaging devices in a closed position; 
     FIG. 4 is a top view of the multimodality medical imaging system of FIG. 1, illustrating the imaging devices in separate positions; 
     FIG. 5 illustrates a support frame for aligning the imaging devices in a closed position and for supporting a vertical actuator positioned between the imaging devices; 
     FIG. 6 is a perspective view of a front portion of a patient table and drive assembly of the patient handling assembly of the invention; 
     FIG. 7 is a perspective view of the underside of a patient pallet of the patient handling assembly; and 
     FIG. 8 is a perspective view of the front portion of the patient table of the patient handling assembly, looking forward from a position below the scanner of the front imaging device. 
    
    
     DETAILED DESCRIPTION 
     Shown in FIGS. 1 through 4 is a multimodality medical imaging system scanner assembly  100 , having first and second imaging devices  110  and  120 . In the embodiment shown, each of the imaging devices  110  and  120  comprise at least a scanner having a modality of operation, and may also include associated scanner support structure and associated electronics. Further, in the embodiment shown, each of the imaging devices  110  and  120  includes a scanner opening or bore  112  and  122 , respectively, through which an inboard portion  130 B of a patient table  130  extends and translates a subject patient  140  during a scanning operation. It will be apparent that imaging devices  110  and  120  may alternatively utilize scanners or detectors that obtain information about the patient  140  without being configured to form a bore, such as a partial closure, an arrangement of one or more planar detectors and other configurations capable of obtaining patient information. Moreover, it will be apparent that while scanner bores  112  and  122  are preferably circular, other configurations capable of obtaining imaging information may alternatively be utilized. 
     The patient table  130  serves as a patient handling assembly and support structure. The patient table  130  coordinates movement of the patient  140  with respect to operation of the scanners of the imaging devices  110  and  120 , to obtain patient imaging information at one or more desired locations along the length of the patient  140 . An outboard portion  130 A of the patient table  130  includes a vertical actuator  132  for lifting and vertically aligning the longitudinal axis  140 A of the patient  140  with the axes  112 A and  122 A of the bores  112  and  122 . Inboard portion  130 B of the patient table  130  also includes a vertical actuator  134  for aligning vertically with the outboard portion  130 A of the table  130 . In operation, the patient table  130  is capable of extending the patient  140  past the scanners of the imaging devices  110  and  120  in a variety of methods, such as at a continuous rate, at variable rates, in incremental displacements or a combination of such methods, as may be desired or suitable for the scanning operation to be conducted. 
     It will be apparent that the patient table  130  may be utilized in combination with the patient access area  160  and drainage surface  180 , as shown in FIGS. 1 and 3, and with features allowing the separation of imaging devices  110  and  120  shown in FIG.  4 . All such features are disclosed in co-pending U.S. application Ser. No. 10/027,843, entitled “Multimodality Medical Imaging System and Method With Intervening Patient Access Area” and naming as inventors Mark DeSilets, Jacco Eerden and Horace H. Hines and in co-pending U.S. application Ser. No. 10/051,490, entitled “Multimodality Medical Imaging System and Method With Separable Detector Devices” and naming as inventors Mark DeSilets, Horace H. Hines and Donald Wellnitz, both of which applications were filed on Oct. 19, 2001. The contents of both such applications are incorporated herein by reference for all purposes. 
     The imaging devices  110  and  120  acquire, through their scanners, information from the patient  140  sufficient to form tomographic images of the patient. Each of the imaging devices  110  and  120  is coupled to one or more conventional tomographic imaging processor(s), utilizing conventional imaging software to form images from information received from the imaging devices  110  and  120 . 
     Preferably, the imaging devices  110  and  120  cooperate to obtain patient information through different modalities, to provide anatomical structure images and physiologic function images of the patient  140 . More specifically, imaging device  110  is preferably a CT scanner that utilizes X-rays as the mode of obtaining data from which images depicting the internal structure of the patient  140  are formed. On the other hand, imaging device  120  is preferably a PET scanner that utilizes positron emissions originating from a radio-pharmaceutical introduced to the patient as the mode of acquiring data from which images depicting primarily metabolic physiological functions within the patient  140  are formed. During operation, the head and torso of the patient  140  are passed through the bores  112  and  122  of the respective imaging devices  110  and  120 , and their respective scanners, so that a collection of one or more images are obtained from each scanner. When scanning is complete, the patient is retracted in the opposite horizontal direction by the patient table  130 , typically at a faster rate than during the scanning operation, to withdraw the patient  140  from the scanner assembly  100 , to the starting position at the beginning of the scanning procedure. 
     The scanner bores  112  and  122  of the imaging devices  110  and  120  are substantially circular, thus surrounding the patient during imaging scanning operations. The axes  112 A and  122 A of the respective circular openings of each of the bores  112  and  122  are aligned with each other and are preferably aligned with or at least substantially parallel to the path of travel of the patient  140  on the patient table  130 . This allows the patient table  130  to translate the patient  140  through the imaging devices  110  and  120  in one substantially continuous pass. Preferably, the center line of the patient  140  is substantially aligned with or at least substantially parallel to the axes  112 A and  122 A of the detector bores  112  and  122  by adjusting the heights of the inboard and outboard patient table portions  130 A and  130 B adjusting vertical actuators  132  and  134 , respectively. 
     The outboard portion  130 A of the patient table  130  includes a forward section cantilevered forward from the actuator  132 . The table portion  130 A terminates at the other end adjacent the inboard table portion  130 B and adjacent the opening to bore  112  of the front imaging device  110 . The inboard table portion  130 B includes a section cantilevered forward into the scanning area of the front imaging device  110 . A middle section of the table portion  130 B extends between the imaging devices  110  and  120  and spans the patient access area  160 . Extending rearwardly from the middle section is a rearward section of inboard table portion  130 B, which extends through the bore  122  of the rear imaging device  120  and a distance beyond the bore  122  sufficient to allow scanning of the entire length of a patient. The vertical actuator  134  of the inboard table portion  130 B is secured to the housing portion  150 A of the front imaging device  110  and between the scanner bores  110  and  120 . This is preferably accomplished by mounting the actuator  134  to the upper extension of a support frame  410 , such as is shown in FIG.  5 . 
     The position of the patient table outboard and inboard portions  130 A and  130 B are coordinated by a controller  136 . The controller  136  obtains feedback signals from the vertical actuators  132  and  134  identifying the vertical positions of the table portions  130 A and  130 B. As outboard table portion  130 A is raised to a vertical position substantially level with the neck of the bore  112 , the controller  136  adjusts the actuator  134  to maintain vertical alignment between the inboard and outboard table portions  130 A and  130 B. The controller  136  preferably utilizes one or more conventional digital processors and associated memory to implement available software to coordinate and control the height of the table portions  130 A and  130 B. This coordination provides a substantially continuous support surface for the translation of the patient  140  from the outboard table portion  130 A to the inboard table portion  130 B. 
     The vertical actuators  132  and  134  are vertically extended by a variety of mechanisms, such as a scissor actuator, stacked lead screw, four bar linkage lifting mechanism, and the like. 
     The forward and rearward sections of the inboard table portion  130 B are formed from a material that is translucent to radiation or other medium used by the imaging devices  110  and  120 . This allows the forward and rearward sections of the table portion  130 B to extend within the scanner bores  112  and  122  to support the patient  140  during translation, without blocking the imaging process. The construction of forward and rearward sections of the inboard table portion  130 B is preferably a foam core, tightly wrapped by carbon fiber for additional strength and durability. It will be apparent that other materials could be used to wrap and strengthen the foam core of the forward and rearward sections of the table portion  130 B. The middle section of the table portion  130 B is constructed of any durable material and need not be translucent to scanner radiation. 
     The patient  140  is supported on the table  130  by a patient pallet  142 . Because the weight of the patient  140  is supported by the substantially continuous surface of the patient table  130 , the patient pallet  142  is constructed of very thin material, offering little attenuation to the radiation or other medium used by the imaging devices  110  and  120 . Such materials are preferably similar to those available for use as a cover for the inboard table portion  130 B. The pallet  142  is driven between the ends of the patient table  130  to translate the patient  140  as desired. The table  130  includes a drive assembly for driving the patient pallet  142  and the patient  140  between the ends of the patient table  130  during scanning operations. 
     The drive assembly comprises a pair of drive mechanisms  510  and  520 , mounted at the forward and rearward ends, respectively, of the patient table  130 . In addition, the drive assembly includes a forward drive belt  512  and a rearward drive belt  522 , extending from the drive mechanisms  510  and  520 , respectively. Each drive mechanism  510  and  520  comprises a servomotor and belt take-up reel mechanically coupled to an associated drive mechanism. A conventional controller (not shown) actuates the drive mechanisms  510  and  520  to apply substantially continuous tension to the drive belts  512  and  522 . This allows more precise control of the position of the patient pallet  142  and avoids jerking the pallet  142  in the direction of actuation a distance greater than desired when moving the pallet  142  in incremental distances along the table  130 . Tension in the drive belts  512  and  522  is maintained by actuating the servomotor drive mechanisms  510  and  520  in opposite directions, while applying greater tension in the direction movement is desired. 
     Referring now to FIGS. 6,  7  and  8 , the construction and operation of the drive assembly, and various components of the patient table  130 , are illustrated in more detail. The patient pallet  142  and the underlying support surface  133  of the patient table  130  are concave with respect to their longitudinal axes. This configuration cradles the patient  140  against rolling off the sides of the table  130 . The drive belts  512  and  522  are preferably timing belts, which engage teeth in idler rollers  514  and  524 , mounted at the forward and rearward ends, respectively, of the patient table  130 . The drive belts  512  and  522  are secured to the respective front and rear ends of the patient pallet  142  by a clamp  144  that engages one or more of the teeth of the associated drive belts  512  or  522 . To reduce friction between the patient pallet  142  and the underlying support surface  133  of the patient table  130 , Teflon® strips  146  are bonded along the length of the underside of the patient pallet  142 . The support surface  133  is preferably also covered with Teflon® material. 
     Utilizing a drive mechanism that does not require lateral movement of the sections of the inboard table portion  130 B through the scanner bores  112  and  122  enhances the quality of the images obtained by the imaging devices  110  and  120 . Because these sections remain still during scanning, the likelihood of new artifacts being introduced to an image or any the artifacts within the table  130  moving during scanning is avoided. Any artifacts within such sections of the table portion  130 B that are within scanning areas may thus be identified and the image adjusted or interpreted accordingly. 
     Referring now in particular to FIGS. 6 and 8, there is shown a configuration of the patient pallet  142  and the outboard portion  130 A of the patient table  130  forming a trapping mechanism that secures the pallet  142  against vertical movement in response to tension from the rearward drive belt  522 . As is best shown in FIG. 8, the outboard actuator  132  is capable of lowering the outboard portion  130 A of the patient table  130  to a height of approximately 19 to 20 inches above the floor, which is approximately the same height as a standard wheelchair. This facilitates transferring a patient  140  from a wheelchair to the patient table  130 . In this position, the drive belt  522  extending from the rearward end of the patient table  130  extends downwardly from the forward section of the inboard section  130 B of the patient table  130 . This vertical separation of the forward and rearward table portions  130 A and  130 B is necessitated by the bore  112  of the imaging device  110 , which blocks further downward movement of the inboard portion  130 B of the patient table  130 . Once the outboard portion  130 A of the patient table  130  is raised upwardly into vertical alignment with the inboard section  130 B, tension from the drive belt  522  becomes horizontal. 
     The pallet  142  includes downwardly curved trap segments  146  formed along the longitudinal edges. The trap segments  146  extend into curved trap slots  134  formed along the lateral edges of the outboard portion  130 A of the patient table  130 . The trap slots  134  curve upwardly over portions of the trap segments  146  of the pallet  142 , forming trap shoulders  136 . When a vertical force is applied to the pallet  142 , the upper surfaces of the trap segments  146  of the pallet  142  abut the trap shoulders  136  of the table portion  130 A to secure the pallet  142  against upward movement. Moreover, the upward force exerted against the middle section of the patient pallet  142  tends to laterally extend the trap segments  146  into the trap slots  134  as the concave pallet  142  tends to flatten. This response further secures the pallet  142  against vertical movement. Once the upward table portion  130 A is vertically aligned with the inboard portion  130 B, horizontal tension on the pallet  142  by the rearward drive belt  522  slides the pallet  142  horizontally towards the rearward end of the patient table  130 . As the pallet  142  slides rearwardly, the trap segments  146  slide longitudinally out of engagement with the trap slots  134  and trap shoulders  136  of the outboard table portion  130 A. 
     During operation, a patient  140  is placed on the patient pallet  142 , with the outboard table portion  130 A in a lowered position. The actuator  132  then lifts the support surface  133 , pallet  142  and the patient  140  vertically into alignment with the inboard table portion  130 B. Inboard table portion  130 B tracks any further upward movement of the outboard table portion  130 A in response to commands received from the actuator controller  136 . Both the outboard table portion  130 A and the inboard table portion  130 B are vertically adjusted to align the longitudinal patient axis  140 A with the aligned scanner bore axes  112 A and  122 A. Tension is increased in the rear drive belt  522  to pull the patient pallet  142  and the patient  140  at a desired rate through either or both of the imaging devices  112  and  122 . Each of the drive mechanisms  110  and  520  include encoders that provide information concerning the position of the patient pallet  142  to an imaging processor (not shown), which registers the images formed from one or both of the imaging devices  110  and  120  to specific locations along the length of the patient  140 . 
     It will be appreciated that use of the patient handling assembly disclosed avoids the need to translate the outboard and inboard portions  130 A and  130 B axially relative to the imaging devices  110  and  120 . Instead, the table portions  130 A and  130 B are adjusted in a vertical direction. This reduces the amount of space required for the imaging system and its associated costs while also providing a front loading table portion  130 A which is capable of independently lifting a patient  140  from the height of a wheelchair. 
     Having thus described the present invention by reference to certain of its preferred embodiments, it is noted that the embodiments disclosed are illustrative rather than limiting in nature and that a wide range of variations, modifications, changes, and substitutions are contemplated in the foregoing disclosure and, in some instances, some features of the present invention may be employed without a corresponding use of the other features. Many such variations and modifications may be considered obvious and desirable by those skilled in the art based upon a review of the foregoing description of preferred embodiments. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.