Abstract:
The present specification discloses a storage system for enabling the substantially concurrent storage and access of data that has three dimensional images processed to identify a presence of a threat item. The system includes a source of data, a temporary storage memory for receiving and temporarily storing the data, a long term storage, and multiple workstations adapted to display three dimensional images. The temporary storage memory is adapted to support multiple file input/output operations executing substantially concurrently, including the receiving of data, transmitting of data to workstations, and transmitting of data to long term storage.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention relies on U.S. Provisional Patent No. 61/307,294, entitled “Simultaneous Image Distribution and Archiving” and filed on Feb. 23, 2010, for priority and is herein incorporated by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to X-ray screening systems. More particularly, the present invention relates to a high speed temporary data storage system that stores high resolution image data and associated detection results. 
       BACKGROUND OF THE INVENTION 
       [0003]    Increases in terrorist threats has created a need to deploy high speed, high resolution, and more accurate threat screening devices in locations which are most likely targets of such violence, such as ports, airports, train stations, and government buildings. Screening technologies currently employed at most places provide either high speed screening but generate digital radiography images which are not fully three-dimensionally (3D) volumetric, or provide relatively detailed 3D volumetric images using computed tomography (CT) at a slow screening speed. 
         [0004]    Recently developed screening systems such as the real-time tomography (RTT) screening system developed by Rapiscan Systems, Inc. can screen items such as luggage at a very high rate and produce high-resolution 3D volumetric images.  FIG. 1   a  illustrates the RTT screening system. A piece of luggage  102  is passed through the RTT screening system  100  and a 3D volumetric X-ray image of the luggage  102  is displayed on the monitor  104 .  FIG. 1   b  illustrates the 3D volumetric image  105  of the piece of luggage  102  screened by the RTT screening system  100 . 
         [0005]    The RTT screening system  100  comprises a stationary gantry CT design that controls a plurality of X-ray emitters. It captures 3D images at several times the speed of legacy CT systems.  FIG. 2  is a block diagram illustrating high level data flow in the RTT screening system. The RTT screening system  202  comprises a reconstruction engine  204  which receives sinogram data from RTT hardware  202 , and produces a high resolution 3D reconstructed image. A threat detection engine  206  receives the reconstructed image as an input from the reconstruction engine  204  and processes it by applying one or more automatic threat detection algorithms to generate a decision, e.g. all clear or signal an alarm, on the image. The threat detection engine  206  then passes on the data comprising the image and the result of processing of the image to a storage device  208 , where it is stored temporarily. The same data is retrieved by the 2D and 3D operator workstation(s)  210 ,  212  and specifically assigned to alarm resolution stations  214  over a network, such as an Ethernet. Regulatory authorities may require high security regions such as airports to store the image data for a predefined period of time, i.e. up to 48 hours. The data is then written to a disk storage system  216  for long term storage, and passed to various display workstations in real-time. U.S. patent application Ser. Nos. 10/554,656, 10/554,975, 10/554,655, 10/554,570, 12/097,422, 12/142,005, and 12/787,878 disclose various aspects of the RTT system and their specifications are incorporated herein by reference in their entirety. 
         [0006]    The high-speed RTT system can generate a data rate as high as 400 MB/sec. The data is required to be stored for later retrieval, and also accessed by the 2D and 3D workstations  210 ,  212  as quickly as possible. Commercially available standard network attached storage (NAS) devices typically store data on an array of hard disk drives. Typically, standard NAS consists of redundant array of inexpensive disks (RAID) to ensure high levels of data integrity. The purpose of the storage array is to store various bag files (.BAG) scanned by the RTT system  202 . The storage array also stores engineering/intermediate data such as information associated with the bag images, system calibration information, system configuration, event logs, among other information. 
         [0007]    Due to file system overhead and read/write seek time of the hard drive sub-system, among other reasons, standard NAS devices cannot effectively simultaneously store the data at high speed and also provide sustained high-speed read access to multiple screener workstations. Typical hard disk arrays have a seek time of about 15 ms. Therefore, when a standard NAS device tries reading and writing at the same time, the hard drive ends up spending most of the time seeking, thus reducing the effective throughput. 
         [0008]    Hence, there is need for a NAS device which provides a high speed temporary storage system that stores high resolution image data and associated detection results. There is also a need for a NAS device that can concurrently or simultaneously store data at high speed and also provide sustained high-speed read access from multiple screener workstations. 
       SUMMARY OF THE INVENTION 
       [0009]    The present specification discloses a storage system for enabling the substantially concurrent storage and access of data, comprising: a source of data, wherein said data comprises a three dimensional image wherein said three dimensional image has been processed to identify a presence of a threat item; a temporary storage memory for receiving and temporarily storing said data, wherein said temporary storage memory is adapted to support multiple file input/output operations executing substantially concurrently and wherein said data is received from said source of data via one of said multiple file input/output operations executing substantially concurrently; at least two workstations for accessing said data, wherein each of said workstations is configured to access the temporary storage memory through one of said multiple file input/output operations executing substantially concurrently; and a long term storage system for accessing and storing said data, wherein said long term storage system is configured to access the temporary storage memory through one of said multiple file input/output operations executing substantially concurrently. 
         [0010]    Optionally, the temporary storage memory is configured to receive data from said source of data at a data transfer rate equal to or greater than 1.6 gigabytes per second. The temporary storage memory is a RAM buffer having a size of at least 32 gigabytes. Each of said workstations can access said data at a speed of at least 100 megabytes per second. 
         [0011]    Optionally, the temporary storage memory is adapted to receive data from said source of data via a first file input/output operation, transmit data to a first workstation via a second file input/output operation, transmit data to a second workstation via a third file input/output operation, and transmit data to the long term storage via a fourth file input/output operation, wherein each of said first, second, third, and fourth file input/output operations executes concurrently. Each of said file input/output operations is executed via a FTP server thread. The fourth file input/output operation occurs at a rate of at least 200 megabytes per second. The second and third file input/output operations occur at an average rate of at least 70 megabytes per second. Upon receiving a request from a workstation for data that is not present in said temporary storage memory, said temporary storage memory is adapted to retrieve said requested data from the long term storage and transmit the requested data to the workstation. 
         [0012]    Optionally, if said data is not associated with an alarm or a threat, the temporary storage memory transmits the data to long term storage and does not retain said data for access by the workstations. The temporary storage memory receives said data into a TCP offload engine. The TCP offload engine receives data from an Ethernet switch. The Ethernet switch is at least a 10 Gb Ethernet switch. The temporary storage memory transmits data to the workstations via an Ethernet switch. The Ethernet switch is at least a 10 Gb Ethernet switch. Each of said workstations is configured to display 3-D images. 
         [0013]    In another embodiment, the specification discloses a process for high speed storage and access of data wherein said data comprises a plurality of three dimensional images and wherein said three dimensional images have been processed to identify a presence of a threat item system, comprising: receiving said data into a temporary storage memory through a first file input/output operation; transmitting said data to a first workstation through a second file input/output operation; transmitting said data to a second workstation through a third file input/output operation; and writing said data to a long term storage through a fourth file input/output operation, wherein said first, second, third, and fourth file input/output operations execute substantially concurrently. 
         [0014]    Optionally, the temporary storage memory is configured to receive data from a source of said data at a data transfer rate equal to or greater than 1.6 gigabytes per second. The temporary storage memory is a RAM buffer having a size of at least 32 gigabytes. Each of the workstations can access said data at a speed of at least 100 megabytes per second. Each of said file input/output operations is executed via a FTP server thread. The fourth file input/output operation occurs at a rate of at least 200 megabytes per second. The second and third file input/output operations occur at an average rate of at least 70 megabytes per second. Upon receiving a request from a workstation for data that is not present in said temporary storage memory, said temporary storage memory is adapted to retrieve said requested data from the long term storage and transmit the requested data to the workstation. If said data is not associated with an alarm or a threat, the temporary storage memory transmits the data to long term storage and does not retain said data for access by the workstations. 
         [0015]    These, and other embodiments, will be described in greater detail in the remainder of this specification. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other features and advantages of the present invention will be appreciated, as they become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0017]      FIG. 1   a  is a side perspective view of one embodiment of a high speed screening system; 
           [0018]      FIG. 1   b  is a 3D volumetric image of a piece of luggage screened by a high speed screening system; 
           [0019]      FIG. 2  is a block diagram illustrating high level data flow in one embodiment of a high speed screening system; 
           [0020]      FIG. 3  is a block diagram illustrating an exemplary data flow architecture in a screening system; 
           [0021]      FIG. 4  is a block diagram of one embodiment of a high-speed screening system employing a hybrid NAS configuration, in accordance with one embodiment of the present invention; and 
           [0022]      FIG. 5  is a block diagram of the hybrid NAS, in accordance with one embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    It is an object of the present invention to provide a high speed temporary storage system that stores high resolution image data and associated detection results. 
         [0024]    The present specification relates to a high speed temporary storage system that stores high resolution image data and associated detection results. The present specification discloses a hybrid NAS which is used in conjunction with high speed X-ray screening systems and makes use of Random Access Memory (RAM) to cache the screening data. The architecture of the hybrid NAS allows the data to be stored in real time as well as be concurrently or simultaneously accessed by monitoring screener workstations, also in real time. 
         [0025]    According to an aspect, the hybrid NAS of the present invention provides random access memory (RAM) to replace the RAID array), thereby eliminating the read/write access time. The hybrid NAS allows random access to the data stored therein, with typical access times of ˜15 μs, which is faster than for hard disk storage devices. 
         [0026]    The present specification discloses multiple embodiments. The following disclosure is provided in order to enable a person having ordinary skill in the art to practice the invention. Language used in this specification should not be interpreted as a general disavowal of any one specific embodiment or used to limit the claims beyond the meaning of the terms used therein. The general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the invention. Also, the terminology and phraseology used is for the purpose of describing exemplary embodiments and should not be considered limiting. Thus, the present specification is to be accorded the widest scope encompassing numerous alternatives, modifications and equivalents consistent with the principles and features disclosed. For purpose of clarity, details relating to technical material that is known in the technical fields related to the invention have not been described in detail so as not to unnecessarily obscure the present invention. The present invention will now be discussed in context of embodiments as illustrated in the accompanying drawings. 
         [0027]    As a threshold matter, it is important to understand the data rates at issue in the present invention. In one embodiment, a screening system needs to be able to store data generated at a rate of at least 125 MB per second, and concurrently or simultaneously provide access to such generated data to at least two separate, networked workstations at a rate of at least 50 MB per second. One of ordinary skill in the art would appreciate that each workstation comprises a computer having at least one processor, memory, and network access. Preferably, the screening system stores data generated at a rate of at least 250 MB per second, and concurrently or simultaneously provide access to such generated data to at least five separate, networked workstations at a rate of at least 65 MB/s. Preferred write data rates can increase to 300 MB/s, 500 MB/s or greater and preferred read data rates can increase to 75 MB/s or greater depending upon the screening system configuration. 
         [0028]    For example, in one embodiment, assuming the image data is produced by a single RTT machine, as described above, and two 3D workstations produce and read the image data simultaneously, three parameters primarily determine the data rate of the RTT system: a) resolution of the reconstruction volume (X, Y and Z), b) belt speed, and c) tunnel size. Shown below are four data rate calculations based upon four different RTT configurations which are as follows:
       RTT80 which assumes a 80 cm tunnel size, 250 mm/s belt speed, and 1 mm reconstruction volume resolution;   RTT80 which assumes a 80 cm tunnel size, 500 mm/s belt speed, and 1 mm reconstruction volume resolution;   RTT110 which assumes a 110 cm tunnel size, 250 mm/s belt speed, and 1 mm reconstruction volume resolution; and   RTT110 which assumes a having 110 cm tunnel size, 500 mm/s belt speed, and 1 mm reconstruction volume resolution.       
 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 RTT-80 @ 250 mm/sec 
               
             
          
           
               
                 Parameters/Assumptions 
                 Avg/Min 
                 Units 
               
               
                   
               
             
          
           
               
                 Belt Speed 
                 250.000 
                 mm/sec 
               
               
                 Size of the bag 
                 750.000 
                 Mm 
               
               
                 Max size of the bag 
                 2500.000 
                 Mm 
               
               
                 Time to acquire the data for Avg 
                 3.000 
                 Sec 
               
               
                 Bag 
               
               
                 Time to acquire the data for Max 
                 10.000 
                 Sec 
               
               
                 Bag 
               
               
                 Minimum Gap between bags 
                 100.000 
                 Mm 
               
               
                 Time between bags 
                 0.400 
                 Sec 
               
               
                 Shrink Wrap Performance 
                 0.700 
               
               
                 Compression performance 3D Vol 
                 0.600 
               
               
                 data &amp; mask 
               
               
                 Image resolution tunnel width (X) 
                 768.000 
                 Pixel 
               
               
                 Image resolution tunnel height (Y) 
                 544.000 
                 Pixel 
               
               
                 Size of the 3D projection slice 
                 835584.000 
                 Bytes 
               
               
                 Size of the Mask data 
                 417792.000 
                 Bytes 
               
               
                 .BAG info (Result + Header) 
                 500000.000 
                 Bytes/Bag 
               
               
                 2D Image size 
                 15728640.000 
                 Bytes/Bag 
               
               
                 Slice resolution 
                 1.000 
                 Mm 
               
               
                 Time to produce 1 mm slice 
                 0.004 
                 Sec 
               
               
                 Decompression time on workstation 
                 0.001 
                 s/slice 
               
               
                 Number of slices for average bag 
                 750.000 
                 Slices 
               
               
                 Number of slices for max bag 
                 2500.000 
                 Slices 
               
               
                 Final Data rate 
                 125.826 
                 MB/s 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 RTT-80 @ 500 mm/sec 
               
             
          
           
               
                 Parameters/Assumptions 
                 Avg/Min 
                 Units 
               
               
                   
               
             
          
           
               
                 Belt Speed 
                 500.000 
                 mm/sec 
               
               
                 Size of the bag 
                 750.000 
                 Mm 
               
               
                 Max size of the bag 
                 2500.000 
                 Mm 
               
               
                 Time to acquire the data for Avg 
                 1.500 
                 Sec 
               
               
                 Bag 
               
               
                 Time to acquire the data for Max 
                 5.000 
                 Sec 
               
               
                 Bag 
               
               
                 Minimum Gap between bags 
                 100.000 
                 Mm 
               
               
                 Time between bags 
                 0.200 
                 Sec 
               
               
                 Shrink Wrap Performance 
                 0.700 
               
               
                 Compression performance 3D Vol 
                 0.600 
               
               
                 data &amp; mask 
               
               
                 Image resolution tunnel width (X) 
                 768.000 
                 Pixel 
               
               
                 Image resolution tunnel height (Y) 
                 544.000 
                 Pixel 
               
               
                 Size of the 3D projection slice 
                 835584.000 
                 Bytes 
               
               
                 Size of the Mask data 
                 417792.000 
                 Bytes 
               
               
                 .BAG info (Result + Header) 
                 500000.000 
                 Bytes/Bag 
               
               
                 2D Image size 
                 15728640.000 
                 Bytes/Bag 
               
               
                 Slice resolution 
                 1.000 
                 Mm 
               
               
                 Time to produce 1 mm slice 
                 0.002 
                 Sec 
               
               
                 Decompression time on workstation 
                 0.001 
                 s/slice 
               
               
                 Number of slices for average bag 
                 750.000 
                 Slices 
               
               
                 Number of slices for max bag 
                 2500.000 
                 Slices 
               
               
                 Final Data rate 
                 251.651 
                 MB/s 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 RTT-110 @250 mm/sec 
               
             
          
           
               
                 Parameters/Assumptions 
                 Avg/Min 
                 Units 
               
               
                   
               
             
          
           
               
                 Belt Speed 
                 250.000 
                 mm/sec 
               
               
                 Size of the bag 
                 750.000 
                 Mm 
               
               
                 Max size of the bag 
                 2500.000 
                 Mm 
               
               
                 Time to acquire the data for Avg 
                 3.000 
                 Sec 
               
               
                 Bag 
               
               
                 Time to acquire the data for Max 
                 10.000 
                 Sec 
               
               
                 Bag 
               
               
                 Minimum Gap between bags 
                 100.000 
                 Mm 
               
               
                 Time between bags 
                 0.400 
                 Sec 
               
               
                 Shrink Wrap Performance 
                 0.700 
               
               
                 Compression performance 3D Vol 
                 0.600 
               
               
                 data &amp; mask 
               
               
                 Image resolution tunnel width (X) 
                 1024.000 
                 Pixel 
               
               
                 Image resolution tunnel height (Y) 
                 768.000 
                 Pixel 
               
               
                 Size of the 3D projection slice 
                 1572864.000 
                 Bytes 
               
               
                 Size of the Mask data 
                 786432.000 
                 Bytes 
               
               
                 .BAG info (Result + Header) 
                 500000.000 
                 Bytes/Bag 
               
               
                 2D Image size 
                 15728640.000 
                 Bytes/Bag 
               
               
                 Slice resolution 
                 1.000 
                 Mm 
               
               
                 Time to produce 1 mm slice 
                 0.004 
                 Sec 
               
               
                 Decompression time on workstation 
                 0.001 
                 s/slice 
               
               
                 Number of slices for average bag 
                 750.000 
                 Slices 
               
               
                 Number of slices for max bag 
                 2500.000 
                 Slices 
               
               
                 Final Data rate 
                 236.568 
                 MB/s 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 RTT-110 @500 mm/sec 
               
             
          
           
               
                 Parameters/Assumptions 
                 Avg/Min 
                 Units 
               
               
                   
               
             
          
           
               
                 Belt Speed 
                 500.000 
                 mm/sec 
               
               
                 Size of the bag 
                 750.000 
                 Mm 
               
               
                 Max size of the bag 
                 2500.000 
                 Mm 
               
               
                 Time to acquire the data for Avg 
                 1.500 
                 Sec 
               
               
                 Bag 
               
               
                 Time to acquire the data for Max 
                 5.000 
                 Sec 
               
               
                 Bag 
               
               
                 Minimum Gap between bags 
                 100.000 
                 Mm 
               
               
                 Time between bags 
                 0.200 
                 Sec 
               
               
                 Shrink Wrap Performance 
                 0.700 
               
               
                 Compression performance 3D Vol 
                 0.600 
               
               
                 data &amp; mask 
               
               
                 Image resolution tunnel width (X) 
                 1024.000 
                 Pixel 
               
               
                 Image resolution tunnel height (Y) 
                 768.000 
                 Pixel 
               
               
                 Size of the 3D projection slice 
                 1572864.000 
                 Bytes 
               
               
                 Size of the Mask data 
                 786432.000 
                 Bytes 
               
               
                 .BAG info (Result + Header) 
                 500000.000 
                 Bytes/Bag 
               
               
                 2D Image size 
                 15728640.000 
                 Bytes/Bag 
               
               
                 Slice resolution 
                 1.000 
                 Mm 
               
               
                 Time to produce 1 mm slice 
                 0.002 
                 Sec 
               
               
                 Decompression time on workstation 
                 0.001 
                 s/slice 
               
               
                 Number of slices for average bag 
                 750.000 
                 Slices 
               
               
                 Number of slices for max bag 
                 2500.000 
                 Slices 
               
               
                 Final Data rate 
                 473.136 
                 MB/s 
               
               
                   
               
             
          
         
       
     
         [0033]    One of ordinary skill in the art would appreciate how to calculate the final data rate from the parameters shown above. The results provided in Tables 1 through 4 demonstrate that a NAS system being used in conjunction with the RTT system requires data storage, or write speed, in excess of 100 MB/s, preferably in excess of 230 MB/s, and more preferably in excess of 475 MB/s, while the same data is concurrently or simultaneously being accessed by the 2D/3D workstations. 
         [0034]    The hybrid NAS of the present invention provides random access memory (RAM) to replace the RAID array, thereby eliminating the read/write access time. The hybrid NAS allows random access to the data stored therein, with typical access times of ˜15 μs, which is faster than for hard disk storage devices. The high-speed image data stored in the hybrid NAS can then be streamed from the corresponding RAM to a standard NAS system for long-term storage, while the same data can be accessed by the 2D and 3D workstations with minimal delay. Another advantage of the hybrid NAS is that the data can be accessed by multiple clients at the same time. Reading and writing at the same time does not affect the performance of random access memory of the hybrid NAS. The size of the RAM file system of the hybrid NAS can be chosen such that it can store data for a predetermined amount of time at full data rate. In an exemplary embodiment, a hybrid NAS can be configured to store up to 30 minutes of data, at full speed. 
         [0035]    In one embodiment, the high speed temporary storage system provided by the present invention is a hybrid NAS device, which is used in conjunction with a RTT screening system developed by Rapiscan Systems, Inc. as illustrated in  FIGS. 1 and 2 . It should be appreciated that the hybrid NAS system can be implemented using standard hardware computing devices and operating system software, such as a 64-bit Linux Operating System. 
         [0036]      FIG. 3  illustrates an exemplary architecture  300  of data flows in an exemplary high speed screening system. It should be appreciated that the devices types, to the extent specific devices are noted, are exemplary and do not limit the nature or scope of the present invention. The system architecture  300  utilizes three dual cell blade systems (DCBS) as the hardware for the threat detection engine  302 . Data generated by the threat detection engine  302  is written to a hybrid NAS  304  via at least a 10 Gb Ethernet switch  306 , or higher, and is simultaneously retrieved by 2D and 3D workstations  308 ,  310  over 10 Gb Ethernet switch  312 , or higher. In an embodiment, the system  300  may also comprise an Ethernet controller, separate from or integrated within the servers comprising the NAS  304 . It should be appreciated that the embodiments described above are intended to provide hardware examples and not intended to be limiting. In particular, the system architecture  300  may include any hardware or software that performs the equivalent functionality as the three DCBS systems  302  and Ethernet switches  306 ,  312 . 
         [0037]      FIG. 4  illustrates a block diagram of the screening system illustrated in  FIG. 3  employing a hybrid NAS configuration. Screening system  402  comprises a reconstruction engine which receives sinogram data, or X-ray sensor data, from its RTT scanning unit, and produces a high resolution 3D reconstructed image. A threat detection engine  404  receives the reconstructed image as an input and processes it by applying one or more detection algorithms to produce a decision as to whether to clear the bag (e.g. provide an okay indication or not activate any alarm) or indicate that the bag should be manually checked or checked again using the same or different screening device (e.g. an alarm). The data generated by the threat detection engine  404 , which comprises three dimensional image data that has been processed to identify a threat item, is transferred to hybrid NAS  406  via one or more switches  408 , such as a 10 GbE Ethernet switch, and a high speed network connection  410 , such as a TCP/IP connection. In one embodiment, data from the threat detection engine  404  may be temporarily stored in a short term memory  412 , such as DDR2, DDR3, SDRAM, or any type of random access memory (RAM), and more preferably, in short term memory that provides transfer data rates greater than 1.6 GB/s, such as, but not limited to, 3.2 GB/s, 6.4 GB/s, or 12.8 GB/s. Short term memory can be a temporary buffer that stores up to the last “n” minutes of data from the system, where “n” may be defined by a user of the system to be 24 hours or down to a few minutes, or any increment therein. 
         [0038]    The hybrid NAS  406  comprises a high speed image processing unit  414  comprising a TCP offload engine (TOE)  416  to rapidly move substantial amounts of data to multiple places, one or more processors  418 , and a RAM drive  420 . The TOE  416  is a technology used in network interface cards to offload processing of the entire TCP/IP stack to the network controller and is known to persons of ordinary skill in the art. It is primarily used with high speed interfaces like 10 GbE, where processing overhead (CPU time) of the network stack becomes significant. The one or more processors  418  process the data from the threat detection engine being stored in the RAM drive  420 . In one embodiment the high speed image processing unit comprises 64 GB to 128 GB of RAM. 
         [0039]    The hybrid NAS  406  further comprises an input/output (I/O) processor  422 , a TOE  424 , and a RAID controller  426  which controls read/write into RAID disk array  428 . In one embodiment, the I/O processor  422  operates at 2.4 GHz or higher and processes the data being written to and being read out of the RAID disk array  428 . The RAID controller  426  controls the read/write operations into the RAID disk array  428 . The data stored using the hybrid NAS  406  is made available to a plurality of external workstations  430 , at a high speed of at least 100 MB/sec and more preferably 125 MB/s, 250 MB/s, 350 MB/s, 400 MB/s, 500 MB/s or greater than 500 MB/s In one embodiment the number of external workstations accessing the data stored in the hybrid NAS  406  ranges from 3 to 15. 
         [0040]      FIG. 5  illustrates a software block diagram of the hybrid NAS  500 , in accordance with one embodiment of the present invention. The figure illustrates a DCBS module  502  (running on a processor) accessing random access memory (RAM) buffer  504  by means of file transfer protocol (FTP) via a FTP server thread  506  using a file input-output (I/O) operation. The RAM buffer  504  is also accessed by 2D and 3D workstations  508 ,  510  by means of FTP via FTP server threads  512  and  514  respectively, using file I/O operations. An archiving process  516  accesses the RAM buffer  504  periodically, using file I/O operation and writes data stored on the RAM buffer  504  on a permanent storage device such as a RAID disk array  518 . The archiving process is any programmed process for reading data from memory and writing the data to storage. In one embodiment, the archiving process has continuous access to RAM and the access rate is controlled using an operating system task priority setting. 
         [0041]    In the embodiment illustrated in  FIG. 5 , the RAM buffer  504  is accessed by four different threads, i.e. an interface to DCBS  502  for storing real time RTT data comprising image data in the form of files with .BAG extensions, two 2D/3D workstations  508 ,  510  for viewing the .BAG images, and a local archiving process  516  running on a local server to perform sequential writes to the local RAID disks  518 , hard disks, or any other form of long term storage. Long term storage may be configurable per a user&#39;s requirements. In a typical airport installation, a user may require to store all processed images up to 48 hours. The data are usually stored in RAID, NAS, or SANs. In the embodiment illustrated in  FIG. 5 , FTP servers, which are used purely for illustrative purposes, enable multiple workstations to establish concurrent sessions, or instances. In other embodiments, various suitable data transfer protocols which enable the establishment of concurrent instances of data among multiple workstations may be used. It should be appreciated that each workstation comprises a client device, such as a desktop, laptop, mobile device, tablet computer, or other computer with a network connection and interface, a processor, a display, and programmatic applications collectively configured to receive and display three dimensional data. 
         [0042]    If a 3D workstation  508  tries to access a file that is not cached in the RAM buffer  504 , the archiving process  516  reads the required data from the RAID disk array  518  and transmits the data. In an embodiment, under this condition, the performance of the write task slows down, but the hybrid configuration continues cache to the RAM buffer  504 . The frequency of this condition depends on the size of the RAM buffer  504 , which in various embodiments, ranges from 32 GB to 64 GB and caches approximately 50 to 100 .BAG image files. 
         [0043]    In one embodiment, the hybrid NAS  500  illustrated in  FIG. 5  is designed to perform intelligent caching. For example, the hybrid NAS  500  can be configured to store only the images associated with an alarm, thereby reducing the amount of memory required. The images which are not associated with an alarm (i.e. cleared) are stored on the RAID disks  518  and removed from the RAM buffer  504  as soon as possible or based on a predefined period of time, such as after “n” minutes have elapsed, or based on a predefined of RAM buffer usage, such as after “X” megabytes of data are stored or after “X %” of the RAM buffer is occupied. One of ordinary skill in the art would appreciate that the “alarm” is generated by the security scanning system, using systems and methods known to persons of ordinary skill in the art. A processor with the security scanning system records to memory an alarm with a specific file, thereby activating the long term storage process, as described above, along with the RAM-based delivery of the file information to workstations. Other screening characteristics could also be used, including bag size, bag contents, passenger destination (using, for example, the system disclosed in U.S. Pat. No. 7,418,077, which is incorporated herein by reference). 
         [0044]    Tables 5A and 5B illustrate the performances of a standard NAS and a hybrid NAS respectively, when operated in conjunction with the RTT screening system under identical conditions. 
         [0000]                                          TABLE 5A                   Average Write Speed   Average Read       Configuration   (MB/s)   Speed (MB/s)                                1 RTT (Write only)   202.2           1 RTT/1 3D Workstation   100.1   68       1 RTT/2 3D Workstation   13   63.7                    
The results depicted in Table 5A show that the standard NAS was able to sustain approximately 202 MB/s during the write only (1 RTT) cycle. However, the performance of the standard NAS dropped once there is a simultaneous read cycle.
 
         [0000]                                          TABLE 5B                   Average Write Speed   Average Read Speed       Configuration   (MB/s)   (MB/s)                                1 RTT (Write only)   236.7           1 RTT/1 3D Workstation   222.3   107.93       1 RTT/2 3D Workstation   226   76.5                    
The results depicted in Table 5B show the performance of the hybrid NAS. The system as configured was able to sustain approximately 226 MB/sec while allowing two 3D workstations to access the data at the rate of 75 MB/sec. As is apparent by the results illustrated in Tables 5A and Table 5B, the hybrid NAS configuration can achieve relatively high read/write rate required by a high data rate security system.
 
         [0045]    The hybrid NAS can be applied to various X-ray screening systems existing in the art including all of the Rapiscan Systems, Inc. security products. The use of the hybrid NAS with the RTT system is only for illustrative purposes and should not be construed as limiting. While the exemplary embodiments of the present invention are described and illustrated herein, it will be appreciated that they are merely illustrative. It will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from or offending the spirit and scope of the appended claims.