Abstract:
In pediatric diagnostic imaging, a patient is seated upright on a patient couch ( 1 0) of a large bore CT scanner. The patient is seated such that coronal or near coronal slices are taken as opposed to axial slices as in typical CT scanners. The patient is stationarily supported in this position during imaging. A back support member ( 14 ) supports the back and side restraint panels ( 18 ) limit lateral movement. Restraint straps ( 30 ) further secure selected parts of the patient. The angle of the support member ( 14 ) is adjusted to conform with a selected imaging region by angle adjustment grooves ( 20 ). A removable telescopic head rest ( 40 ) positions the patient leaning forward. The back support ( 14 ), the side restraint panels ( 18 ), and the headrest ( 40 ) are all constructed of radiolucent materials.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to the diagnostic imaging arts. It finds particular application in non-axial pediatric diagnosis using computed-tomography (CT) and will be described with particular reference thereto. However, it is to be appreciated that it is also applicable to non-pediatric applications and imaging scenarios, and is not limited to the aforementioned applications. 
     In a slice mode, CT scanners procure image data by taking a plurality of contiguous slices of a subject and reconstructing them into a volumetric representation. Typically this is done by taking axial or near axial slices, that is, taking slices that are substantially perpendicular to a longitudinal (head to toe) axis of a subject. 
     In a spiral mode, volume images are collected by moving the x-ray beam through a spiral trajectory around the longitudinal axis. Commonly, the source rotates continuously while the patient support moves longitudinally back and forth. 
     A limitation of present devices is that patients are inserted head-first or feet-first. Often, only a few slices along a major axis of an organ or tissue of interest are necessary. Organs and anatomical structures that have large longitudinal profiles such as the spine or lungs require many axial slices to generate a single longitudinal slice. 
     The generation of numerous axial slices is time consuming, plus penetrating radiation can be harmful to living cells. Not only is the tissue in the longitudinal slice of interest irradiated, all tissue in the axial planes around the longitudinal slice of interest are irradiated from many directions. In particular, cells that divide rapidly are more susceptible to radiation than slower dividing cells. In general, children are more susceptible to radiation damage than adults simply because they are growing and their cells are dividing faster. When using penetrating radiation to image children, it is desired to keep the dosage as low as possible and limit the irradiation, as much as possible, to the specific slices to be displayed. In addition, children tend to be more restless than adults. Thus, motion artifacts become problematic, especially in temporally longer scans. A more efficient method of imaging portions of the body with large axial profiles which lessens exposure and scan time is desirable. 
     Another problem with imaging children is that an attendant frequently remains close at hand to assist in keeping the child still, as well as to comfort the child. Although the attendant does not enter the imaging region, she still receives a nominal amount of scattered radiation. Over many scans of many different children, the received dosages of the attendant becomes problematic. 
     The present invention provides a new and improved method and apparatus that overcomes the above referenced problems and others. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, a computed tomography apparatus is given. Radiation from a source is detected by an array of detectors and reconstructed into an image representation of a patient within the apparatus. A patient support that provides support for the patient in a seated position within the apparatus is located on a patient couch. 
     In accordance with another aspect of the present invention, a method of diagnostic imageing is given. A subject is positioned in a seated position within an imaging region of a CT scanner. A source emits radiation into the region and is detected after it traverses the region. The detected radiation is converted into corresponding electronic data and reconstructed into an image representation. 
     In accordance with another aspect of the present invention, a patient seat for use in conjunction with a third or fourth generation CT scanner is given. A back support that supports an upper torso of a patient in an upright position rests upon a base portion that supports the weight of a patient. The base portion and back support fit inside a bore of the CT scanner. 
     One of the advantages of the present invention resides in shorter scan times. 
     Another advantage resides in less received dose by the patient. 
     Another advantage resides in improved image quality. 
     Yet another advantage resides in the ability to procure non-axial image slices. 
     Still further benefits and advantages of the present invention will become apparent to those skilled in the art upon a reading and understanding of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention. 
     FIG. 1 is a diagrammatic illustration of a CT scanner an patient support in accordance with the present invention; 
     FIG. 2 is a perspective view of the patient support. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to FIG. 1, a mobile patient couch  10  is disposed adjacent an aperture  12  of a computed tomography scanner. In the preferred embodiment, the aperture  12  is approximately 85 cm, larger than those of typical present day CT scanners. Optionally, smaller apertures such as 75 cm, are practical. Preferably, the CT scanner is a third or fourth generation machine. An x-ray source, disposed on a perimeter of the aperture  12  emits a fan or cone of x-rays into an imaging region. In a third generation machine, an array of detectors is disposed opposite to and rotates with the x-ray source to detect the radiation. The array moves in synchronization with the source, such that the center of the array is 180° around the perimeter from the source. In a fourth generation machine, the perimeter is lined with stationary detectors, and the source rotates about the perimeter. 
     In the preferred embodiment, a patient support and positioner  14  is supported on the patient couch  10 . The support  14  fits into the aperture  12  of a CT scanner gantry  16 . A large aperture  12  yields several advantages. One is that the patient feels less cramped, helping the patient relax. Another advantage is that it allows patients to sit upright or other non-prone positions during scans, as opposed to only lying flat. 
     The patient support and positioner  14  provides stability and secure stationary support for a child or small adult in a seated or other selected, non-axial imaging position on the patient couch  10 . Taller patients are supportable in partially reclined positions. With the patient in this position, coronal, and sagittal slices of the patient are collected. 
     In particular applications, organs and other bodily structures are imaged that are longitudinally elongated but have relatively small transverse profiles. Some examples are the lungs, spinal column, and kidneys. While it would take many slices to image the entire spinal column with axial slices, it takes but a few slices with a coronal orientation. By positioning the patient seated with the spine vertical, the coronal plane through the spine can be aligned with the plane of rotation of the x-ray beam. Coronal imaging captures the spine with only a few slices. Therefore, less of the body receives useless radiation. Moreover, the eyes and other radiation sensitive organs are positioned outside of the x-ray beam during data acquisition. 
     With reference to FIG.  2  and continuing reference to FIG. 1, the back support member  14  of the preferred embodiment is flanked by two side restraint panels  18 . The restraint panels have matching angle adjustment grooves  20  for an attendant or operator to select an angle of the back support member  14  with respect to a vertical axis. Thus, varying entry orientations can be achieved by manipulating the angle of the support member. To do this, the operator loosens two securing knobs  22  one on each side of the support member  14 . The operator grasps the support member  14  by a handle  24  or by the knobs  22  and lifts it from the angle adjustment grooves  20 . Pivot pins  26  received in elongated slots allow the support member  14  to be lifted sufficiently for the knobs  22  to clear the grooves  20 . The back support is tilted within the range of the adjustment grooves  20 . The operator lifts the back support  14 , selects one of the grooves  20  corresponding to a selected tilt, and lowers the support member  14  until the knobs are received in the selected groove. The knobs are tightened to help prevent the support member from shifting during an imaging process. In addition, the angle of the irradiated slice is varied by tilting the gantry  16 , as ghosted in FIG.  1 . 
     The side restraint panels  18  also serve as rigid restraints against lateral movement during imaging. As children tend to become restless when uncomfortable or nervous, the restraint panels  18  remind and arrest the child to remain still. Additional restraints, such as straps  30  with Velcro™ hook an loop connectors, a harness, or the like extend from the support member. The support member  14  is equipped with multiple strap holes  32  for securing the restraint straps  30 . A wide range of patient heights are accommodated. The operator chooses among the plurality of strap holes  32  to select ones that best fit the patient height or desired position in the apparatus. Additional supports and restraints such as foam wedges or cushions are contemplated. 
     In addition to improving image quality by reducing motion artifacts, the restraints also allow for less attendant interaction. While an attendant may remain in the room, the attendant will not remain as close to the CT scanner to attend to the child when the machine is in operation. The attendant may also wear more mobility constricting radiation shielding garments. 
     The base board  28  defines a seat where the patient sits during imaging. The base board  28  is temporarily attachable to the patient couch. The base board  28  has a convex shape that matches the concave shape of the patient couch  10 . The base board  28  is attached to the patient couch with radiolucent clamps  34 , straps, or other configurations that are designed to engage the couch 
     When the base board  28  is positioned and secured to the couch  10  for coronal imaging, the assembly is oriented such that the legs of the patient extend along the patient couch. During a slice imaging sequence, the back support and gantry are angled and the couch is moved longitudinally to align a slice of interest with the plane of the radiation beam. For spiral, volume imaging, the couch  10  translates into and out of the aperture  12  while the x-ray source is rotating. 
     Alternately, the base board  28  can be shaped such that it fits 90° rotated from the orientation previously described. This orientation facilitates sagittal imaging of the subject. 
     In the preferred embodiment, the back support member  14 , the side restraint panels  18 , the base board  22 , and the restraint straps  30  are all made of carbon fiber reinforced polymers, low density wood, or other radiolucent material which does not contribute negatively to the imaging process. 
     In the preferred embodiment, a removable telescopic head rest  40  is used for certain imaging procedures. The head rest is adjustable to varying heights. A height adjustment pin  42  is used to select the height of the headrest  40  depending on the size of the patient, desired position, etc. Varying heights are selected by removing the adjustment pin  42  sliding the upper section up or down on the lower section and reinserting the pin in a different hole. The headrest  40  is also removable entirely if it is not required. The upper section is shaped to receive the patient&#39;s forehead when it is desired to keep the head of the patient out of the scan region. The eyes, for example, are especially sensitive to the x-rays. Sometimes procedures are performed in which uncomfortable or contorted positions are held for the duration of the scan. The head rest  40  helps make such positions more bearable by providing a soft support for the head of the patient. 
     With further reference to FIG. 1, prior to the patient being inserted into the machine, the operator submits selected parameters  50  into the machine. Parameters such as slice thickness, number of slices, gantry tilt angle, scanning mode, and the like are selected. After the patient is disposed on the patient couch  10  in the selected position, the operator initiates the selected procedure. The source rotates around the gantry  16  emitting x-rays which are detected by the detectors opposite the source. The views of the x-ray detectors are stored in a pre-reconstruction data memory or buffer  52 . The view data is reconstructed in a reconstruction processor  54 . In an exemplary reconstruction, the views are convolved  54   a  and backprojected  54   b  to form a slice image. For a volume image, a plurality of slices are then reconstructed and stacked in a volumetric image memory  56 . Spiral and other reconstruction techniques are also contemplated. The operator then selects desired portions of the volume for viewing. An image processor  58  formats slice images, 3D renderings, and the like for display on a human readable display  60  such as a video monitor, liquid crystal display, active matrix monitor, or the like. 
     In an alternate embodiment, a cine mode is available. This mode is applicable to dynamic temporal scanning techniques. The x-ray source rotates about one slice or a small number of slices. Images are continuously reconstructed and viewed as new ones become available. In this manner, real time, or semi-real time images of the subject are acquired. Some possible applications are bolus tracking, digestive/respiratory tract studies, joint movement, etc. 
     The invention has been described with reference to the preferred embodiment. Modifications and alterations will occur to others upon a reading and understanding of the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.