Abstract:
A programmable memory is provided in each of a plurality of detector modules arrayed in a positron emission tomography (PET) scanner. Each detector module memory stores data associated with its respective detector module. Each memory may be coupled to a processor via a transmission bus. A display device may be coupled to the processor for displaying information relating to information obtained from the detector module memories.

Description:
RELATED APPLICATIONS 
     Priority is claimed under 35 U.S.C. §119(e) from provisional application Ser. No. 61/100,335, filed Sep. 26, 2008. 
    
    
     BACKGROUND 
     The present disclosure relates to Positron Emission Tomography (PET) data acquisition, more particularly to accessing information associated with detector detectors installed in a PET scanner. 
     Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images which show the function and anatomy of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radiopharmaceuticals produce gamma photon emissions which emanate from the body and are captured by a scintillation crystal, with which the photons interact to produce flashes of light or “events.” Events are detected by an array of photodetectors, such as photomultiplier tubes, and their spatial locations or positions are calculated and stored. In this way, an image of the organ or tissue under study is created from detection of the distribution of the radioisotopes in the body. 
     One particular nuclear medicine imaging technique is known as Positron Emission Tomography, or PET. PET is used to produce images for diagnosing the biochemistry or physiology of a specific organ, tumor or other metabolically active site. Measurement of the tissue concentration of a positron emitting radionuclide is based on coincidence detection of the two gamma photons arising from positron annihilation. When a positron is annihilated by an electron, two 511 keV gamma photons are simultaneously produced and travel in approximately opposite directions. Gamma photons produced by an annihilation event can be detected by a pair of oppositely disposed radiation detectors capable of producing a signal in response to the interaction of the gamma photons with a scintillation crystal. Annihilation events are typically identified by a time coincidence between the detection of the two 511 keV gamma photons in the two oppositely disposed detectors, i.e., the gamma photon emissions are detected virtually simultaneously by each detector. When two oppositely disposed gamma photons each strike an oppositely disposed detector to produce a time coincidence event, they also identify a line of response, or LOR, along which the annihilation event has occurred. 
     Radiation detectors typically are deployed in an array of axially aligned rings, each ring comprising a plurality of individual detectors. For example, scanner detector modules may contain three or four rings of forty eight detectors in each ring. PET scanner manufacturers are mandated by regulatory agencies to maintain a device history record for each scanner, which include, for example, part numbers and serial numbers of all traceable components, including detectors. The specific installation location, ring and angular position, are also to be kept in the record. 
     The device history record normally is maintained by hand inspection or by use of bar code readers. Application of such process for tracking the large number of individual detectors is time consuming and prone to human errors. For example, if the detector manufacturer discovers a problem with a specific batch of detectors at any time, the locations of the problem detectors in a particular scanner, as well as all other scanners at dispersed geographical sites, must be identified. If a detector problem is found during the testing process upon installation in a particular scanner, this abnormality should be recorded. Should a particular system determine that a detector is experiencing performance problems, the particular details of the problem, and conditions under which it was observed, should be included in a history record for review when field service personnel retrieves the affected detector and returns it to the manufacturer for post-failure analysis. 
     Detector identification is also needed for scanners that may need to permit or restrict certain functionality based on the model number and/or serial number of the detectors installed in the scanners. For example, a system containing lower-grade detectors might be restricted to certain lower-grade image processing algorithms or algorithms that were tailored to a specific model of detector. 
     The need thus exists for an easier and more efficient way to track important information associated with individual PET scan detectors and to readily obtain such information at a later date. 
     DISCLOSURE 
     The above needs are met, at least in part, by providing a programmable memory for each of a plurality of detector modules arrayed in a positron emission tomography (PET) scanner. The detector modules may be structured in one or more ring configurations. Each detector module includes a plurality of crystal scintillators and photodetectors. Each detector module memory stores data associated with its respective detector module. Each memory may be coupled to a processor via a transmission bus. A display device may be coupled to the processor for displaying information relating to information obtained from the detector module memories. The processor may be coupled to a network accessible by a remote service computer. The detector module memories thus may be accessed pursuant a local or remote request for stored information. Information retrieved may be used for local or remote display. 
     Each memory may store information that identifies the location of its respective detector module in the array, as well as information that may be defined by a set of attributes common to the plurality of detector modules. For example, the attributes may include module identifier, e.g., serial number, model descriptor, date of manufacture of the detector module, date of testing of the detector module, or other customized criteria. A graphic representation of the array of the plurality of detector modules can be displayed on the local, and/or remote, display device. A detector module of interest to a user may be selected from the graphic representation. In response, the processor can access the associated detector module memory, retrieve information stored therein, and present the retrieved information on the display device. A user may query the detector module memories by selecting a criterion for one attribute of the set of attributes. From information retrieved from the detector module memories, the processor can identify all detectors that meet the selected criterion and control the display device to indicate on the graphic representation those detector modules that have been identified. 
     Additional advantages of the present disclosure will become readily apparent to those skilled in this art from the following detailed description, wherein only preferred embodiments are shown and described, simply by way of illustration of the best mode contemplated. As will be realized, the disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the disclosed concepts. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawing and in which like reference numerals refer to similar elements and in which: 
         FIG. 1  is an simplified block diagram of a PET detection apparatus; 
         FIG. 2  is a block diagram of a system for maintaining and accessing detector module information; 
         FIG. 3  is an exemplary display representation for a graphical user interface in the system of  FIG. 2 ; and 
         FIG. 4  is a diagram of a computing hardware that can be used to implement various embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a simplified block diagram of a detection system utilizing a PET scanner for generating depth-of-interaction information. Detection system  100  includes a detector module array  101  to observe events stemming from a radiation source  103  emitting radiation (e.g., gamma rays) from a subject patient  105 . The detector module array  101  outputs data to a data processor  107 , which includes a data acquisition module  109  and an image processor  111 . The data acquisition module  109  uses spatial coordinate signals to produce input to the image processor  111 . The image processor  111  can then produce, for example, an image of tissues in the patient  105 . The image can then be displayed on a display unit  113 . 
     The detector array may include, for example, detectors used in the Siemens Biograph mCT system. The scanner, for example, may be provided with three rings having 144 detector modules or four rings of 192 detector modules. Event detection data may be output to the data processor  107  in a data stream over a fiber optic line, or equivalent means of transmission. The data acquisition module  109  and image processor  111  may contain local Redundant Array of Independent Disks (RAID) and a direct memory access (DMA) rebinner card such as a Petlink™ DMA rebinner (PDR) made by Siemens. Data processor  107  sums the counted events in data acquisition module  109  and, in conjunction with image processor  111 , the data processor  107  reconstructs and displays a two dimensional image of the relative spatial count density on display monitor  113 . 
     A detector  115  of the detector module array  101  is represented in the block diagram of  FIG. 2 . Scintillator crystals  120  receive gamma photon radiation from the subject patient and produce flashes of light, i.e., events, that are detected by photomultiplier tubes (PMTs)  122  or photo detector devices. The PMTs convert the received light to electrical signals, which are amplified and output under control of module controller  124  to data processor  107 . Module  124  may comprise front-end electronics for tube biasing, gain control and other such functionality. 
     Memory  126 , illustrated merely by example as an EEPROM, is accessible by I 2 C protocol bus or the like by data processor  107 , which can be coupled to a local service computer  130 . Local service computer may be coupled via Ethernet LAN, Internet or other wide area network (WAN) to a remote service computer. Information stored in the memory may include part number, serial number, date of manufacture, date of test, and additional notes as required. Memory  126  is programmed by the detector manufacturer as one of the final steps in the factory test process. When detectors are mounted on the actual system, their serial numbers are already programmed and ready to be queried to generate the Device History Record. This information remains stored in the detector module memory until retrieved by field service personnel. 
     The memory can be assessed by a software query at any time via the serial bus. All detector modules in the scanner apparatus can be queried simultaneously. 
       FIG. 3  is an exemplary display representation for a graphical user interface for accessing information from the detector module memories. Data processor  107  may be accessed by local service computer  130  and/or a remote service computer via a network to display the representation shown by example in  FIG. 3 . The displayed image corresponds to four rings of detector modules. Each ring comprises forty eight detector modules. The displayed image depicts twelve groups  200 , each group consisting of four detector modules of each ring that are in radial proximity. The sixteen detector modules of each group are shown as blocks labeled 0-15. The blocks are correlated to the actual location in the array in which the corresponding detector modules are positioned. The center area  204  of the displayed image can be used for displaying results from queries to the stored detector module memories. 
     A sample table of detector output data for group 0 is shown below. Each group contains a similar output data structure. 
     
       
         
               
               
               
               
               
             
           
               
                   
               
               
                 Electronics 
                 Model 
                 Manufacture 
                   
                   
               
               
                 Group 0 
                 Number 
                 Date 
                 Serial Number 
                 Test Date 
               
               
                   
               
             
             
               
                 Detector 0 
                 12345678 
                 Jun. 1, 2009 
                 001 
                 Jun. 3, 2009 
               
               
                 Detector 1 
                 12345678 
                 Jun. 1, 2009 
                 002 
                 Jun. 3, 2009 
               
               
                 Detector 2 
                 12345678 
                 Jun. 1, 2009 
                 003 
                 Jun. 3, 2009 
               
               
                 Detector 3 
                 12345678 
                 Jun. 1, 2009 
                 004 
                 Jun. 3, 2009 
               
               
                 Detector 4 
                 12345678 
                 Jun. 1, 2009 
                 005 
                 Jun. 3, 2009 
               
               
                 Detector 5 
                 12345678 
                 Jun. 1, 2009 
                 006 
                 Jun. 3, 2009 
               
               
                 Detector 6 
                 12345678 
                 Jun. 1, 2009 
                 007 
                 Jun. 3, 2009 
               
               
                 Detector 7 
                 12345678 
                 Jun. 1, 2009 
                 008 
                 Jun. 3, 2009 
               
               
                 Detector 8 
                 12345678 
                 Jun. 1, 2009 
                 009 
                 Jun. 3, 2009 
               
               
                 Detector 9 
                 12345678 
                 Jun. 1, 2009 
                 010 
                 Jun. 3, 2009 
               
               
                 Detector 10 
                 12345678 
                 Jun. 1, 2009 
                 011 
                 Jun. 3, 2009 
               
               
                 Detector 11 
                 12345678 
                 Jun. 1, 2009 
                 012 
                 Jun. 3, 2009 
               
               
                 Detector 12 
                 12345678 
                 Jun. 1, 2009 
                 013 
                 Jun. 3, 2009 
               
               
                 Detector 13 
                 12345678 
                 Jun. 1, 2009 
                 014 
                 Jun. 3, 2009 
               
               
                 Detector 14 
                 12345678 
                 Jun. 1, 2009 
                 015 
                 Jun. 3, 2009 
               
               
                 Detector 15 
                 12345678 
                 Jun. 1, 2009 
                 016 
                 Jun. 3, 2009 
               
               
                   
               
             
          
         
       
     
     Icon buttons  210 - 218  may be selected by the user to specify a query that accesses all detector modules in the scanner. Selection of button icon  210  will request identification of any detector module having a specified serial number. Selection of button icon  212  will request identification of all detector modules having a specified model number. Selection of button icon  214  will request identification of all detector modules tested on a specified date. Selection of button icon will request identification of all detector modules having a specified date of manufacture. The requests of button icons  210 - 216  described herein are illustrative. The memories may be programmed to include additional information related to the respective detector modules which may of interest or required by service personnel. Button icon  218  represents the option to identify detectors by custom criteria. 
     The detector modules that are identified in response to the selection of button icons  210 - 218  are shown by highlighting their respective blocks in the display. For example, the user may select icon button  212 , requesting the locations of all detector modules having a specified model number.  FIG. 3  shows highlights of the detector blocks that meet the request. Detector 9 is highlighted in a group that corresponds for illustrative purposes to be group 0. Assuming that the groups are numbered sequentially in the clockwise direction, the other detectors that meet the requested criterion are detector 1 of group 2, detector 15 of group 3, detector 7 of group 5, detector 8 of group 8, detector 12 of group 9, and detector 15 of group 10. The highlighted blocks correspond to the detector module locations in the array. 
     The displayed graphical representation of  FIG. 3  may also be used to obtain information about a detector module that corresponds to a selected block. For example the user may select block 4 of group 11, as indicated by the shading in the figure. The memory of the detector module that corresponds to block 4 is accessed and the data stored therein is read out for display, as shown in the center area  204 . 
       FIG. 4  illustrates a computing hardware  400  upon which the service computer system can be implemented. The computer system  400  includes a bus  401  or other communication mechanism for communicating information and a processor  403  coupled to the bus  401  for processing information. The computer system  400  also includes main memory  405 , such as a random access memory (RAM) or other dynamic storage device, coupled to the bus  401  for storing information and instructions to be executed by the processor  403 . Main memory  405  can also be used for storing temporary variables or other intermediate information during execution of instructions by the processor  403 . The computer system  400  may further include a read only memory (ROM)  407  or other static storage device coupled to the bus  401  for storing static information and instructions for the processor  403 . A storage device  409 , such as a magnetic disk or optical disk, is coupled to the bus  401  for persistently storing information and instructions. 
     The computer system  400  may be coupled via the bus  401  to a display  411 , such as a cathode ray tube (CRT), liquid crystal display, active matrix display, or plasma display, for displaying information to a computer user. An input device  413 , such as a keyboard including alphanumeric and other keys, is coupled to the bus  401  for communicating information and command selections to the processor  403 . Another type of user input device is a cursor control  415 , such as a mouse, a trackball, or cursor direction keys, for communicating direction information and command selections to the processor  403  and for controlling cursor movement on the display  411 . 
     Processes are performed by the computer system  400 , in response to the processor  403  executing an arrangement of instructions contained in main memory  405 . Such instructions can be read into main memory  405  from another computer-readable medium, such as the storage device  409 . One or more processors in a multi-processing arrangement may also be employed to execute the instructions contained in main memory  405 . In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the certain embodiments. Thus, the exemplary embodiments are not limited to any specific combination of hardware circuitry and software. 
     The computer system  400  also includes a communication interface  417  coupled to bus  401 . The communication interface  417  provides a two-way data communication coupling to a network link  419  connected to a local network  421 . For example, the communication interface  417  may be a digital subscriber line (DSL) card or modem, an integrated services digital network (ISDN) card, a cable modem, a telephone modem, or any other communication interface to provide a data communication connection to a corresponding type of communication line. Communication interface  417  may be a local area network (LAN) card (e.g. for Ethernet™ or an Asynchronous Transfer Model (ATM) network) to provide a data communication connection to a compatible LAN. Wireless links can also be implemented. In any such implementation, communication interface  417  sends and receives electrical, electromagnetic, or optical signals that carry digital data streams representing various types of information. The communication interface  417  can include peripheral interface devices, such as a Universal Serial Bus (USB) interface, a PCMCIA (Personal Computer Memory Card International Association) interface, etc. Although a single communication interface  417  is depicted in  FIG. 4 , multiple communication interfaces can also be employed. 
     The network link  419  typically provides data communication through one or more networks to other data devices. For example, the network link  419  may provide a connection through local network  421  to a host computer  423 , which has connectivity to a network  425  (e.g. a wide area network (WAN) or the global packet data communication network now commonly referred to as the “Internet”) or to data equipment operated by a service provider. The local network  421  and the network  425  both use electrical, electromagnetic, or optical signals to convey information and instructions. The signals through the various networks and the signals on the network link  419  and through the communication interface  417 , which communicate digital data with the computer system  400 , are exemplary forms of carrier waves bearing the information and instructions. 
     In this disclosure there are shown and described only preferred embodiments of the invention and but a few examples of its versatility. The system allows a push-button creation of as-installed map of detectors on each scanner, with all part numbers, serial numbers, etc. The information stays in the detector module memories. Technicians can immediately and accurately determine exactly which detectors are installed in a given system, and even where they are installed within the system, by issuing a simple console command, either locally or remotely. Electronic traceability of each detector ensures accurate correlation of detector performance versus intrinsic characteristics and manufacturing processes. If certain batches of detectors must be recalled or serviced, the electronic traceability allows real-time reporting of an affected scanner and detector locations. 
     It is to be understood that the invention is capable of use in various other combinations and environments and is capable of changes or modifications within the scope of the inventive concept as expressed herein. For example, certain scanner features can be enabled or disabled based on the model or serial number of detectors installed. The locations of the installed detectors associated with the model or serial number of interest can readily be determined.