Abstract:
A Positron Emission Tomography (PET) scanner may have a PET gantry, a calibration radiation source arranged rotatable in the PET gantry, and a drive mechanism coupled with the calibration radiation source, wherein the drive mechanism is formed by non ferromagnetic materials.

Description:
TECHNICAL FIELD 
       [0001]    The present invention concerns a rotation device for a radiation source. 
       BACKGROUND 
       [0002]    Magnet Resonance Imaging (MRI) is a non-invasive method using very strong magnetic fields to render images of the inside of an object and is primarily used in medical imaging to demonstrate pathological or other physiological alterations of living tissues. In addition Positron Emission Tomography (PET) is another medical imaging method, where a short-lived radioactive tracer isotope, which decays by emitting a positron, is injected usually into the blood circulation of a living subject. After the metabolically active molecule becomes concentrated in tissues of interest, the research subject or patient is placed in the imaging scanner. The molecule most commonly used for this purpose is fluorodeoxyglucose (FDG), a sugar, for which the waiting period is typically an hour. 
         [0003]    As the radioisotope undergoes positron emission decay, it emits a positron, the antimatter counterpart of an electron. After traveling up to a few millimeters the positron encounters and annihilates with an electron, producing a pair of gamma photons moving in almost opposite directions. These are detected in the scanning device by a detector assembly, typically a scintillator material coupled to a photomultiplier, which converts the light burst in the scintillator into an electrical signal. The technique depends on simultaneous or coincident detection of the pair of photons. 
         [0004]    Both scanning methods have their particular advantages, thus, diagnosis often requires both scanning methods. The latest complex scanning devices, thus, combine MRI and PET scanner in a way, that both devices can operate in parallel. Traditionally, normalization of a the PET scanner is performed by using an electric motor that rotates a calibration radiation source within a PET gantry. However, if an MRI and a PET scanner are combined, the strong magnetic fields of an MRI make it impossible to operate a normal electric motor. Thus, using traditional normalization methods, the PET insert camera within an MRI system must be normalized outside the MRI. 
       SUMMARY 
       [0005]    According to an embodiment, a Positron Emission Tomography scanner may comprise a PET gantry, a calibration radiation source arranged rotatable in the PET gantry, and a drive mechanism coupled with the calibration radiation source, wherein the drive mechanism is formed by non ferromagnetic materials. 
         [0006]    According to yet another embodiment, a method for calibrating a Positron Emission Tomography (PET) scanner may comprise the steps of providing a calibration radiation source arranged rotatable in a PET gantry, and rotating the calibration radiation source in the PET gantry by a drive mechanism coupled with the calibration radiation source, wherein the drive mechanism is formed by non-ferromagnetic materials. 
         [0007]    According to yet another embodiment, a Positron Emission Tomography (PET) scanner may comprise a PET gantry, a calibration radiation source arranged rotatable in the PET gantry, and a drive mechanism coupled with the calibration radiation source, wherein the drive mechanism comprises a turbine driven by a compressed gas and a second wheel coupled with the turbine by a belt and wherein the second wheel is coupled with a support structure onto which the calibration radiation source is mounted, wherein the drive mechanism is manufactured from non-ferromagnetic material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    A more complete understanding of the present disclosure thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings wherein: 
           [0009]      FIG. 1  shows a front view of an embodiment. 
           [0010]      FIG. 2  shows a top view of the embodiment shown in  FIG. 1 . 
           [0011]      FIG. 3  shows a perspective view of a first embodiment as shown in  FIG. 1 . 
           [0012]      FIG. 4  shows a perspective view of a second embodiment. 
           [0013]      FIG. 5  shows a perspective view of a third embodiment. 
           [0014]      FIG. 6  shows a perspective view of a fourth embodiment. 
       
    
    
       [0015]    While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific example embodiments is not intended to limit the disclosure to the particular forms disclosed herein, but on the contrary, this disclosure is to cover all modifications and equivalents as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0016]    According to further enhance a PET scanner as defined above, the drive mechanism may comprises a first wheel driven by a compressed gas. Moreover, the first wheel may be coupled with a turbine driven by the compressed gas. The first wheel may comprise blades. The drive mechanism may comprise a second wheel coupled with the first wheel by a belt and the second wheel may be coupled with a support structure onto which the calibration radiation source can be mounted. The drive mechanism may be manufactured from plastic material. The drive mechanism may be manufactured from at least one plastic material selected from the group consisting of polyethylene, polypropylene, and Acrylonitrile butadiene styrene (ABS). The support structure can be a sprocket gear coupled with the second wheel via a gear mechanism. The first and second wheels may be sprocket gears and the belt may be a toothed belt. The PET scanner may further comprise a control device for controlling a gas flow driving the first wheel. The PET gantry may comprise mounting holes and the drive mechanism can be mounted using plastic mounting strut bolts in the mounting holes. The PET scanner can be arranged within an Magnetic Resonance Imaging (MRI) system. The drive mechanism may comprise a turbine driven by a hydraulic fluid. The drive mechanism may comprise a flexible drive shaft manufactured from non ferromagnetic materials. 
         [0017]    According to another enhancement, the method as defined above may furthermore comprise the step of driving the drive mechanism by a compressed gas. The method may also comprise the step of driving a turbine coupled with a first wheel. The compressed gas can be compressed air. The drive mechanism may be manufactured from plastic material. The drive mechanism can be manufactured from at least one plastic material selected from the group consisting of polyethylene, polypropylene, and Acrylonitrile butadiene styrene (ABS). The method may also further comprise the step of driving the drive mechanism by a hydraulic fluid. The method may also comprise the step of driving the drive mechanism by a flexible drive shaft manufactured from non ferromagnetic materials. 
         [0018]      FIGS. 1 ,  2  and  3  show an embodiment of drive mechanism  100  for a PET scanner that can be integrated with an MRI system in a front and top view. The PET scanner comprises a PET gantry  110  onto which a first drive wheel  120  is mounted, for example, by a support structure  130 . The first drive wheel is coupled with another support structure  125  via a shaft  210 . This support structure  125  can be, for example, a rotating arm  125  which extends from the axis of the shaft in one direction. Alternatively, the support structure may extend in opposite directions from the shaft axis. Support structure  125  carries the radiation source on one end of an arm. Depending on the size and form of the radiation source, other support structures may be used. By turning drive wheel  120 , the radiation source  260  rotates within the PET gantry  110  according to respective calibration procedure. 
         [0019]    The first drive wheel  120  may be coupled to second drive wheel  150  via a coupling belt  140 . According to one embodiment, drive wheels  120  and  150  are each in the form of gears such as sprockets and the drive belt  140  may be a toothed belt. However, if applicable, the drive system also may be embodied by grooved wheels and a rubber belt as used for example in belt driven turntables. 
         [0020]    The second drive wheel may be equipped with a plurality of blades  155  or coupled with a turbine  255 . In front of this turbine  255  or the blades  155 , the outlet of a gas supply rod or hose is placed to deliver a stream of gas to the blades  155  or turbine  255  in such a way that depending on the gas pressure delivered from tube  220 , the second drive wheel rotates more or less in the designated direction. To this end, tube  220  is coupled with a gas/lair source  240  that delivers air/gas in a controlled fashion. Tube  220  may have a nozzle attached to its proximate end to deliver air/gas at a higher flow rate. The gas/air source may be a gas/air supply tank having a controllable outlet valve controlled by a respective control device  250 . Alternatively, air or any other suitable gas may be delivered by a respective plumbing structure and the gas/air source may be a controllable valve controlled by device  250  to deliver the required gas to drive turbine  255  and its coupled drive wheel  150 . 
         [0021]      FIG. 3  is a perspective view of an embodiment according to  FIGS. 1 and 2 . As can be seen, when flow rate regulated compressed air or other suitable gas exits the tube  220 , the out coming air/gas hits the blades of turbine  255  which will rotate accordingly. Through belt  140  drive wheel  120  is rotated and, thus, via shaft  210  and support structure  125 , the radiation source  260  within PET gantry  110  as required for a respective calibration process. 
         [0022]      FIG. 4  shows a different embodiment of the drive system. Again, a primary drive wheel  150  and a secondary drive wheel  120  are used. However, the secondary drive wheel  120  drives a small sprocket  310  via shaft  330 . This small sprocket  310  engages in outer toothed area of a sprocket  320  arranged within the PET gantry  110 . Sprocket  320  is mounted within the PET gantry  110  via a support structure  340  and shaft  350  which can be similar to structure  130  and shaft  210 . The radiation source  260  can be directly mounted on sprocket  320  in this embodiment. This embodiment allows for a more flexible adjustment of the gear ratio of the entire arrangement by adjustment of the respective sizes of the used gears and sprockets. 
         [0023]    All elements of the arrangement shown to drive the radiation source can be manufactured from non ferromagnetic materials. For example, the turbine can be manufactured polyethylene, prolypropylene, Acrylonitrile butadiene styrene (ABS), or other suitable materials. Similarly all wheels, sprocket gears, the belt, etc. can be manufactured from similar materials. 
         [0024]    As shown in  FIGS. 3 and 4 , during calibration of a PET scanner, the radiation source  260  is rotated around the central axis of the PET gantry. This radiation source  260  emits a high energy radiation that is collected by the PET cameras by rotating the radiation source  260  through the shown mechanism according to the different embodiments, a uniform distribution of radiation is collected. The arrangement as shown in the figures will not be affected by the strong magnetic fields because all parts can be manufactured from non-ferromagnetic material. As shown in the Figures, regulated compressed air/gas is forced over the plastic turbine  255  which is connected to the small sprocket gear  150 . As the regulated air/gas flows across the turbine at a known flow rate, the small sprocket gear  150  turns in direct proportion the turbine  155 / 255  as seen by equation 1: 
         [0000]      V sprocket1 =V turbine    (1) 
         [0025]    where V sprocket1 =the angular speed of sprocket  150 , and
       V turbine =the angular speed of the turbine  255  controlled directly by the flow rate of the compressed air/gas.       
 
         [0027]    The speed of the larger sprocket  120  is directly related to the speed of sprocket  150  by the following relationship: 
         [0000]        V   sprocket1   *D   sprocket1   =V   sprocket2   *D   sprocket2    (2) 
         [0028]    where D sprocket1 =the diameter of sprocket  150 , and
           D sprocket2 =the diameter of sprocket  120 .           
 
         [0030]    A plastic mounting strut  130  is used in the shown embodiments that bolts into the PET gantry  110  using existing holes. A ceramic rod can be used as shaft  210  that is rigidly attached to sprocket  120  and may lead through the mounting bracket  130  using a Teflon bearing. This ceramic rod  210  is rigidly attached to the plastic arm  125  that holds the radiation source. In this way, precise control of the angular velocity of the radiation source  260  can be achieved by simply regulating the compressed air/gas and modifying the diameters of the two sprockets  120  and  150 . 
         [0031]      FIG. 5  shows yet another embodiment. In this embodiment a hydraulic fluid is used to drive a turbine instead of gas as disclosed in the above embodiments. According to this embodiment, a turbine is arranged within a housing  520 . An input connection  510  may be connected to a fluid source such as a hydraulic tank (not shown). An output connection  530  is also provided to which a respective hydraulic control loop may be connected. The turbine  520  may comprise an drive sprocket coupled with the inner hydraulic turbine to drive belt  140 . Thus, a known hydraulic control circuit may be connected to this drive arrangement. 
         [0032]      FIG. 6  shows yet another embodiment in which a long flexible drive shaft  610  is coupled to an AC or DC motor  620  that is located at a considerable distance from the magnetic field allowing the motor to function properly. The broken lines indicate that the flexible coupling may be arranged at a considerable distance. 
         [0033]    While embodiments of this disclosure have been depicted, described, and are defined by reference to example embodiments of the disclosure, such references do not imply a limitation on the disclosure, and no such limitation is to be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and are not exhaustive of the scope of the disclosure.