Patent Publication Number: US-2017354394-A1

Title: Iinterface for positron emission tomography (pet) scanner detector module

Description:
CROSS-REFERENCE OF RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 (e) to U.S. Provisional Patent Application Ser. No. 62/348,048, filed on Jun. 9, 2016, the entire contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a positron emission tomography (PET) detector module, and more particularly to a PET detector module having an integrated interface with power, clock, synchronization, and communication. 
     BACKGROUND OF THE INVENTION 
     Positron emission tomography (PET) is a functional imaging technique widely used in nuclear medicine and pre-clinical research, which produces a three-dimensional image of functional biological processes in live bodies. It can be used in cancer detection, staging and restaging, treatment planning and monitoring, as well as drug development. During a PET scan, a patient is introduced with positron-emitting radionuclide, which produces pairs of photons, the PET system then detects the photons and reconstructs the three-dimensional images showing the biological process inside the patient body. 
     To build a PET system, detector modules are developed to detect the photon pairs, which usually include high-density scintillator with photodetectors or directly gamma ray detectors to detect each individual photon with precise location and time, as well as with high efficiency. All detected events are sent to a centralized coincidence processing unit or distributed processing units, or software to sort out the prompt events. 
     Due to limited scan time, injection dose and the demand of high image quality, various methods are proposed to increase the system sensitivity. High-density detector or multiple detectors can improve the system sensitivity, and to further improve the image quality. 
     The detector module may include power, clock, synchronization, and communication sections to work together but they are separately built. Conventionally, there are four different kinds of connectors and each kind is responsible for only one function. 
     Recently, “Time of Flight” (TOF) is introduced and proven to improve the imaging quality and/or reduce injection dose and/or scan time. To achieve good timing or TOF, a precision clock and synchronization is needed in addition to the power and communication. However, these four components are still separately built, which causes inconveniences to the users. 
     There is a need for an integrated interface for the detector module including all components in a cost effective way. A unified integrated interface can be used to simplify the module design and the coincidence processing unit or uplink. 
     SUMMARY OF THE INVENTION 
     In one aspect, an integrated interface of a detector module of a Positron Emission Tomography (PET) may include a power module, a clock module, a synchronization module, and a communication module. In one embodiment, Gigabit Ethernet, 10G Ethernet, Fast Ethernet (100M), 10M Ethernet or custom speed Ethernet based solution can be used in the communication module. 
     For the power module, a power module may supply power to a detector using a cable, from a coincidence processing unit (CPU) or a separate source. In one embodiment, the power can be transmitted by a standard PoE (Power over Ethernet), which is configured to pass electric power along with data on twisted pair Ethernet cabling, and allows a single cable to provide both data connection and electric power to devices. The power module may further include at least one PC connected to CPU to process the data received from the detector. It is noted that the power is delivered over the cable with a standard procedure to make sure the power delivery is safe. For example, only a small amount of power is configured to be delivered at the beginning. 
     For the clock module, it is proved that the clock can be recovered from Ethernet. In one embodiment, the clock module has a recovery circuit to get the clock from the serial data, and the recovered clock is used to send the data back. A circuitry on the coincidence processing unit or uplink can be used to recover the clock from the detector module, monitor the difference with a Time to Digital Converter (TDC), and note the difference of the round trip. In another embodiment, this could be n*clock+phase, and n can be found through another technique (Synchronization, discuss later). 
     For the synchronization module, the synchronization can be done through a dedicated package and/or IEEE1588. For example, an uplink/master can send the request with current timestamp (counter) to a downlink/slave, the slave responds in a fixed time delay, and the master detects the response and compare to the current timestamp. The difference detected by the master can be the fixed delay plus cable delay. In one embodiment, the package can be a MAC (Media Access Control) package over Ethernet. To further improve the stability, a pre-request package can be sent from uplink/master to downlink/slave to clear all buffered data, and the downlink/slave responses back with acknowledge package after all buffers are cleared. 
     For data processing and storage, in a centralized system or software system, the coincidence processing unit (CPU) can send the information to all singles processing units (SPUs) and record the difference. In a distributed system, one SPU is chosen as the origin, all others can be synchronized to this SPU, and all difference can be either stored at uplink or downlink. It is noted that when the system power is on, this synchronization process can be done automatically without manual intervention. 
     In another aspect, the integrated interface can be implemented in other systems. For example, it can be used in a gamma camera system or gamma probe, especially a dynamic gamma camera or handheld gamma camera. In such a system, the data acquired is synchronized with the orientation information. The integrated interface can also be used in a SPECT system, where the rotation information can be synchronized. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a conventional PET scanning device that includes detectors, power cable, clock cable, sync cable, data cable, coincidence processing unit and PC. 
         FIG. 2  is a schematic view of a structure including an Ethernet cable, coincidence processing unit, PC and detectors in the present invention. 
         FIG. 3 a    is a schematic view of an interface (RJ45), including an Ethernet cable, coincidence processing unit and PC in the present invention. 
         FIG. 3 b    is a schematic view of an Ethernet-based communication method in the present invention. 
         FIG. 3 c    is a schematic view of a power distribution over Ethernet in the present invention. 
         FIG. 3 d    is a schematic view of clock recovery in the present invention. 
         FIG. 4  is a schematic view of clock recovery in the present invention, where slave uses the recovered clock to transmit data and master detects the difference. 
         FIG. 5  is a schematic view of synchronization with a dedicated package implemented in the slave and master in the present invention. 
         FIG. 6  is a schematic view of the coincidence processing unit that includes a plurality of RJ45 ports with power injectors, an output to PC and a power supply to all downstreams. 
         FIG. 7  is a schematic view of different CPUs in the present invention. 
         FIG. 8  is a schematic view of the implementation of the present invention in other systems. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The detailed description set forth below is intended as a description of the presently exemplary device provided in accordance with aspects of the present invention and is not intended to represent the only forms in which the present invention may be prepared or utilized. It is to be understood, rather, that the same or equivalent functions and components may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. 
     Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs. Although any methods, devices and materials similar or equivalent to those described can be used in the practice or testing of the invention, the exemplary methods, devices and materials are now described. 
     All publications mentioned are incorporated by reference for the purpose of describing and disclosing, for example, the designs and methodologies that are described in the publications that might be used in connection with the presently described invention. The publications listed or discussed above, below and throughout the text are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the inventors are not entitled to antedate such disclosure by virtue of prior invention. 
       FIG. 1  illustrates a conventional Positron Emission Tomography (PET) that may include a power module, a clock/synchronization module, and a communication module. For example, Gigabit Ethernet, 10G Ethernet, Fast Ethernet (100M), 10M Ethernet or custom speed Ethernet based solution can be used in the communication module. 
     Referring to  FIG. 2 , a Positron Emission Tomography (PET) device  200  may include a detector  210  having a power module  211 , an Ethernet cable  220 , and a coincidence processing unit (CPU)  230 . In one embodiment, the power can be transmitted by a standard PoE (Power over Ethernet), which is configured to pass electric power along with data on twisted pair Ethernet cabling, and allows a single cable to provide both data connection and electric power to devices, for example from CPU  230  to detector  210 . The PET device  200  may further include at least one PC  240  connected to CPU  230  to process the data received from the detector  210 . A block diagram of Power over Ethernet (PoE) is shown in  FIG. 3 c   , which may be used to transmit local power  310  to the detector  210  through the operation of a PoE Chip  320 . In one embodiment, the Ethernet cable can be replaced by an HDMI cable. 
     It is noted that the power is delivered over the cable with a standard procedure to make sure the power delivery is safe. For example, only a small amount of power is configured to be delivered at the beginning. 
       FIG. 3 a    shows a typical RJ 45 interface, which includes a detector  210 , an Ethernet cable  220 , and a coincidence processing unit (CPU)  230 , while  FIG. 3 a    shows a number of ways used for the detector  210  and the CPU  230  to communicate with each other. In one embodiment, the detector  210  and the CPU  230  can communicate through User Datagram Protocol (UDP), with which, computer applications can send data, command, etc. in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network. In another embodiment, the detector  210  and the CPU  230  can communicate through Transmission Control Protocol (TCP). 
     A block diagram of the CPU  230  is shown in  FIG. 6 , which may include a plurality of RJ 45 ports ( 610 ,  611  . . . ) with power injectors. A power supply  620  is provided for all downstream RJ 45 ports, and one output  630  to PC  240 . 
     Referring to  FIGS. 3 d    and  4  for the clock module, it is proved that the clock can be recovered from Ethernet. In one embodiment, the clock module has a recovery circuit (inside the receiver RX  410 ) to get the clock from the serial data, and the recovered clock is used to send the data back. A circuitry  420  on the coincidence processing unit  230  or uplink can be used to recover the clock from the detector module, monitor the difference with a Time to Digital Converter (TDC)  430 , and note the difference of the round trip. In another embodiment, this could be n*clock+phase, and n can be found through another technique (Synchronization, discuss later). 
     In the synchronization module as shown in  FIG. 5 , in one embodiment, the synchronization can be done through a dedicated package and/or IEEE1588. For example, an uplink/master  520  can send the request with current timestamp (counter) to a downlink/slave  510 , the slave responds in a fixed time delay, and the master detects the response and compare to the current timestamp. The difference detected by the master  520  can be the fixed delay plus cable delay. The cable delay can be parameter “n” described above. So, at the present stage, the system is synchronized with both clock phase and clock counting. In one embodiment, the package can be a UDP package over IP/MAC. To further improve the stability, a pre-request package can be sent from uplink/master  520  to downlink/slave  510  to clear all buffered data, and the downlink/slave  510  responses back with acknowledge package after all buffers are cleared. 
     For data processing and storage as shown in  FIG. 7 , in a centralized system or software system, the coincidence processing unit (CPU)  710  can send the information to all singles processing units (SPUs) and record the difference. In another embodiment, the information can be kept at CPU. In a distributed coincidence processing unit (CPU)  720 , one SPU is chosen as the origin, all others can be synchronized to this SPU, and all difference can be either stored at uplink or downlink. It is noted that when the system power is on, this synchronization process can be done automatically without manual intervention. 
     In another aspect as shown in  FIG. 8 , the integrated interface can be implemented in other systems. For example, it can be used in a gamma camera system (or gamma probe)  820 , especially a dynamic gamma camera or handheld gamma camera. In such a system, the data acquired is synchronized with the orientation information. The integrated interface can also be used in a SPECT system  810 , where the rotation information can be synchronized. In another embodiment, the integrated interface can be used in a remotely located monitoring system  830 . 
     Having described the invention by the description and illustrations above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Accordingly, the invention is not to be considered as limited by the foregoing description, but includes any equivalents.