EP1761803A2 - Device for on-line data acquisition in three-demensional positron emission tomography - Google Patents

Device for on-line data acquisition in three-demensional positron emission tomography

Info

Publication number
EP1761803A2
EP1761803A2 EP05752291A EP05752291A EP1761803A2 EP 1761803 A2 EP1761803 A2 EP 1761803A2 EP 05752291 A EP05752291 A EP 05752291A EP 05752291 A EP05752291 A EP 05752291A EP 1761803 A2 EP1761803 A2 EP 1761803A2
Authority
EP
European Patent Office
Prior art keywords
pci
dram
fpga
histogramming
card
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05752291A
Other languages
German (de)
French (fr)
Other versions
EP1761803A4 (en
Inventor
William F. Jones
Johnny Reed
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens Medical Solutions USA Inc
Original Assignee
Siemens Medical Solutions USA Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens Medical Solutions USA Inc filed Critical Siemens Medical Solutions USA Inc
Publication of EP1761803A2 publication Critical patent/EP1761803A2/en
Publication of EP1761803A4 publication Critical patent/EP1761803A4/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • G01T1/2914—Measurement of spatial distribution of radiation
    • G01T1/2985—In depth localisation, e.g. using positron emitters; Tomographic imaging (longitudinal and transverse section imaging; apparatus for radiation diagnosis sequentially in different planes, steroscopic radiation diagnosis)
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B6/00—Apparatus for radiation diagnosis, e.g. combined with radiation therapy equipment
    • A61B6/02—Devices for diagnosis sequentially in different planes; Stereoscopic radiation diagnosis
    • A61B6/03—Computerised tomographs
    • A61B6/037—Emission tomography
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T1/00—General purpose image data processing
    • G06T1/20—Processor architectures; Processor configuration, e.g. pipelining

Definitions

  • the present invention pertains to the field of Positron Emission
  • Tomography More particularly, this invention is directed to a dedicated memory device for extremely flexible and general purpose support of on-line event- by-event normalization, real-time physiological gating, unity (+/-) histogramming, and weighted histogramming.
  • PET Positron emission tomography
  • PET is one of several popular methods in radiology because of its ability to non-invasively study physiological processes and structures within the body.
  • PET is a nuclear imaging technique used in the medical field to assist in the diagnosis of diseases.
  • PET allows the physician to examine the whole patient at once by producing pictures of many functions of the human body unobtainable by other imaging techniques.
  • PET displays images of how the body works (physiology or function) instead of simply how it looks.
  • PET- is considered the most sensitive, and exhibits the greatest quantification accuracy, of any nuclear medicine imaging instrument available at the present time. Applications requiring this sensitivity and accuracy include those in the fields of oncology, cardiology, and neurology.
  • positron-emitting isotopes In PET, short-lived positron-emitting isotopes, referred to as radiopharmaceuticals, are injected into a patient. When these radioactive drugs are administered to a patient, they distribute within the body according to the physiologic pathways associated with their stable counterparts. As the radiopharmaceutical isotopes decay in the body, they discharge positively charged particles called positrons. Upon discharge, the positrons encounter electrons, and both are annihilated. As a result of each annihilation event, gamma rays are generated in the form of a pair of diametrically opposed photons approximately 180 degrees (angular) apart.
  • PET images (often in conjunction with an assumed physiologic model) are used to evaluate a variety of physiologic parameters such as glucose metabolic rate, cerebral blood flow, tissue viability, oxygen metabolism, and in vivo brain neuron activity.
  • the present invention is a device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan.
  • PET Positron Emission Tomography
  • the device of the present invention permits very fast read-modify- write (RMW, +/- unity and weighted) histogramming memory cycles, and permits very large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS).
  • OS operating system
  • the present invention also is configurable for on-line buffering of the coincidence packet stream, i.e., "gating buffer” which allows "bad beat” rejection and real-time phase-driven segmentation as needed for physiological cycles such as cardiac and respiratory.
  • the present invention also provides an effective on-line mechanism for incorporating individual normalization correction factors into each coincidence event packet.
  • the present invention is a Smart DRAM (SD) peripheral component interconnect (PCI) card, of which more than one can be used in combination within a PC-based architecture for on-line histogramming.
  • SD PCI card is applied in a plurality of ways. Specifically, the SD PCI card is used as either of a Gating Buffer, a histogramming card, or a look up table (LUT) for normalization correction factors.
  • LUT look up table
  • the Correction Factor LUT SD PCI card serves to insert a
  • correction factors 16-bit correction factor into arriving packets prior to packet retransmittal. These correction factors are retrieved from local RAM as each coincidence event packet arrives, using the contents of the arriving packets to form an index (address) into the local RAM. These correction factors serve to correct for PET detector variability in gamma detection efficiency, ie., "normalization.” The retransmitted packets are expanded in size to provide room for the inserted correction factor.
  • the Gating Buffer card alternately stores an arriving PET data packet stream into two dedicated DRAM banks.
  • the two DRAM banks store and retransmit the packet stream in the order of arrival for an entire physiological cycle. This buffering enables on-line rejection of "bad-beat" cycles and serves the more complex needs of real-time cardiac/ respiratory gating.
  • the SD RMW PCI cards provide a very high rate of histogramming.
  • the extendible daisy-chain of SD RMW PCI cards supports large memory banks across potentially hundreds of SD RMW PCI cards. Under control ⁇ f a single PC, a PCI Expansion chassis is employed such that a large number of PCI cards are supported. This off-the-shelf PCI expansion chassis system (StarFabric) is itself extendible allowing hundreds of PCI slots to be accessed from a single PC.
  • the present invention is further applicable to rapid dynamic, dynamic-gated, continuous bed motion, time-of-flight (TOF), gated-TOF, and correction for patient motion, and all in an on-line manner while the patient remains in the tomograph.
  • TOF time-of-flight
  • the present invention further supports both list-mode-only data acquisition as well as for rapid replay in post-acquisition histogramming of previously collected list-mode data.
  • frame-offset tag packets are used.
  • these offset- control tag packets are input to the Gating Buffer card under control of application software.
  • the offset packets are intermixed with bin-address event packets, all from the Gating Buffer FC output port for reception by the down-stream SD RMW PCI cards.
  • the bin-offset values within these tag packets are received and used by each downstream SD-RMW-resident FPGA to instantly direct histogramming into the designated projection frame throughout the array of SD RMW PCI cards. The .
  • the offset-control tag- packet mechanism is an effective means to instantly direct bin-address activity into any part of the RMW daisy chain via minimal PCI interaction.
  • the component architecture internal to each SD RMW PCI card includes a single field programmable gate array (FPGA) in communication with RAM and with the input/ output (I/O) flow, including I/O via at least one Fibre Channel (FC) and a PCI interface.
  • FPGA field programmable gate array
  • Each of a plurality of DRAM modules is independently in communication with the FPGA to permit independent and simultaneous direct memory access (DMA) to each bank, thus optimizing throughput.
  • the FPGA is in communication with each local Fibre Channel port.
  • Each port consists of a transceiver, typically fiber' optic, and a serializer/ deserializer (SERDES) chip.
  • SERDES serializer/ deserializer
  • Also provided in communication with the FPGA is a first in, first out (FIFO) memory chip.
  • the FPGA architecture includes independent DRAM Controllers for actively accessing dedicated DRAM modules for read-modify-write (RMW) transactions.
  • RMW transactions take two forms. For +/- unity RMW, the transactions involve adding unity to or subtracting unity from individual bins in the DRAM memory.
  • These Unity RMW bins are 2's complement integer values stored as either 8-bit or 16-bit.
  • Weighted RMW the transactions involve adding a correction factor to or . subtracting a correction factor from individual bins in the DRAM memory.
  • These Weighted RMW bins are 2's complement "block floating" values and. are typically stored as 32-bit only.
  • the DRAM bin- address space is quad-interleaved with the assistance of an FPGA-resident Interleave Router.
  • This Router supports quad-interleaving by distributing, according to address-value content, bin-address data packets to each of the four FPGA-resident FIFO blocks and their associated DRAM modules.
  • These FPGA-resident FIFO blocks are provided to greatly reduce the chance of packet pile-up and loss.
  • FPGA-resident bin-address offset control is applied to assist in real-time control of multiple-frame dynamic or multiple-phase-segment gated studies.
  • the FPGA After histogramming is completed for a DRAM-resident projection space and as the projection-space data is read, the FPGA automatically reorders the internal quad-interleaved organization during DMA transfer out to PCI bus, eliminating the need for subsequent user reassembly of the final projection data set.
  • the FPGA and DIMMs are applied without interleaving or histogramming.
  • the Gating SD PCI card is provided primarily to buffer packets in the order of arrival into one of two DRAM banks. While one bank . is loading with data packets arriving in real time via FC input port, the other bank is unloading via FC output port. Data packet output is controlled by operating system-resident application code which drives autonomous FPGA-reside ⁇ t DMA controllers.
  • the PET packet stream arriving at the Gating Buffer is interspersed with both LOR (event) packets and other non-event (tag) packets.
  • Tag packet content includes elapsed milliseconds, cardiac R-wave, and respiratory phase data.
  • a PET normalization correction matrix which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair.
  • a PET normalization correction matrix which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair.
  • each respective scalar correction value in block-floating format, is extracted from the local DRAM content.
  • the index into the local DRAM is formed by the FPGA from the detector-pair packet content, namely, the crystal-pair indexes.
  • An extracted correction factor value is loaded, ie., inserted, into a designated field within the detector-pair packet.
  • This modified packet with correction value which is potentially larger than its original size, is then transmitted for further processing via the out-going FC port.
  • each DRAM-resident RMW bin is a 32-bit 2's complement block-floating value.
  • the event packets input via the FC port are intermixed with conventional tag packets. These event (non-tag) packets are called weighted bin-address event packets.
  • These weighted bin-address event packets contain not only the traditional Prompt/ Delayed (P/D) bit but also a bin-address field and the correction-value field. A correction value is added/ subtracted to/from the respective bin in DRAM memory, depending on the P/D bit.
  • the bin-address value is applied as a quad-byte index into local DRAM. Because both the correction value and the bin content are treated as block floating, the FPGA performs only signed-integer arithmetic for the RMW memory cycles.
  • FIG. 1 is a schematic illustration of a PC-based acquisition architecture incorporating four Smart DRAM (SD) peripheral component interconnect (PCI) cards incorporating various features of the present invention, one SD PCI card being shown for on-line gating, i.e., SD Gating Buffer, and three SD PCI cards being shown for on-line unity histogramming, i e., SD Unity RMW;
  • SD Smart DRAM
  • PCI peripheral component interconnect
  • FIG. 2 is a schematic illustration of the component architecture internal to the Smart DRAM PCI card incorporated in the architecture illustrated in FIG. 1;
  • FIG. 3 is a schematic illustration of an FPGA architecture as applied to histogramming
  • FIG. 4 is a schematic illustration of the FPGA architecture as applied to the Gating Buffer function.
  • FIG. 5 is a schematic illustration of a PC-based acquisition architecture . incorporating five Smart DRAM (SD) peripheral component interconnect (PCI) cards incorporating various features of the present invention, one SD PCI card being shown for on-line normalization, ie., SD CF LUT, one SD card being shown for on- line gating, i.e., SD Gating Buffer, and three SD PCI cards shown for on-line weighted Wstogramming, ie., SD Weighted RMW.
  • SD Smart DRAM
  • PCI peripheral component interconnect
  • a device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan is disclosed.
  • the device of the present invention permits very fast read-modify- write (RMW, +/- unity and weighted) histogramming memory cycles, and permits very large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS).
  • OS operating system
  • FIG. 1 is a schematic illustration of a PC-based acquisition architecture incorporating four Smart DRAM (SD) peripheral component interconnect (PCI) cards of the present invention, illustrated generally at 10.
  • SD Smart DRAM
  • PCI peripheral component interconnect
  • the SD PCI card 10 is applied in two ways.
  • One of the four SD PCI cards 10A is used as a Gating Buffer, while the remaining three SD PCI cards 10B are used for unity RMW histograrnming.
  • This embodiment principally supports on-line gated PET data acquisition. Histogramming rates in the range from 14 to 19 M events/ sec are supported. It will be understood, however, that other rates outside this range may be accomplished using architectures within the scope of the present invention.
  • With an extendible daisy-chain very large projection data sets are supportable, for example, 10 12 bins.
  • the Gating Buffer card 10A alternately stores an arriving PET data
  • the extendible daisy- chain of SD RMW PCI cards 10B supports large memory banks, limited to ⁇ 10* 2 bins (1-4 Terabytes) across potentially hundreds of SD RMW PCI cards 10B in the chain, as required. Under a single PC, a multiple PCI Expansion chassis 16 is provided such that a large number of SD RMW PCI cards 10B are supported.
  • the SD RMW PCI design effectively solves the problem of limited address space found in current PC systems.
  • a moveable 4 Mbyte PCI DMA window is defined for fast and effective DMA transfers into the PC motherboard of the huge, ie., not conventionally addressable, sets of projection data.
  • flow control signaling (not fully illustrated) may be sent upstream between the full- duplex FC links 18.
  • FIG. 1 While the architecture in FIG. 1 is significant for on-line gated studies, it is also effective for many other, even more demanding on-line acquisition types. These include, but are not limited to, rapid dynamic, dynamic-gated, continuous bed motion, time-of-flight (TOF), gated-TOF, and correction for patient motion.
  • the present invention further supports both list-mode-only data acquisition as well as for rapid replay in post- acquisition histogramming of previously collected list-mode data.
  • frame-offset tag packets are used.
  • these offset- control tag packets are input to the Gating Buffer card 10A under control of PC- OS-based application software.
  • the offset tag packets are intermixed with bin- address event packets. These packets are all output from the Gating Buffer FC port for reception by the down-stream SD RMW PCI cards 10B.
  • the bin-offset values in these tag packets are received and used by the FPGA 12B on each of the down-stream SD RMW PCI cards 10B to instantly direct histogramming into the designated projection frame, ie., some portion of the memory space across all the histogramming SD RMW PCI cards 10.
  • the use of the Fibre Channel daisy chain to distribute the frame-offset value to all SD RMW PCI cards 10 minimizes the application code interaction with PCI-accessed FPGA-resident control registers, ie., one frame-offset register access into the SD Gating Buffer card with FC daisy chain distribution of the value avoids the need for multiple and more time-critical PCI registers accessed across multiple SD RMW PCI cards 10.
  • the FPGA 10B on each of SD RMW PCI cards 10B in the chain is directed from the PC operating system via FPGA-resident PCI-loaded registers to respond to only a designated card-size (for example, 4 Gbyte) portion of the available 40-bit projection-data bin space. This bin space is spread across all the SD RMW PCI cards 10B in the chain and is limited to 40-bit indexing.
  • the offset-control tag-packet mechanism is an effective means to instantly direct bin-address activity into any part of the RMW daisy chain via minimal PCI interaction.
  • FIG. 2 is a schematic illustration of the component architecture internal to each SD RMW PCI card 10 of the present invention.
  • Each box in the diagram represents a chip or component on the card 10.
  • a single field programmable gate array (FPGA) 12A, 12B is in communication with the RAM 14 and with the input/ output (I/O) flow, including I/O via at least one Fibre Channel (FC) 18 and a PCI interface 20.
  • FPGA field programmable gate array
  • FC Fibre Channel
  • This architecture achieves maximum flexibility and permits a single board design to service multiple applications.
  • four DRAM dual in-line memory modules (DIMMs) 14 are each independently in communication with the FPGA 12A, 12B to permit independent and simultaneous direct memory access (DMA) to each bank, thus optimizing throughput.
  • DIMMs dual in-line memory modules
  • the FPGA 12A, 12B is in communication with each Fibre Channel port 18 via a transceiver 22 and a serializer/ deserializer (SERDES) chip 24. Also provided in communication with the FPGA 12A 12B is a first in, first out (FIFO) memory chip 26.
  • SERDES serializer/ deserializer
  • FIG. 3 is a schematic illustration of the FPGA architecture as applied to histogramming. This embodiment assists in accomplishing a primary method for achieving fast histograrnming throughput through the use of quad-interleaving.
  • each independent DRAM Controller 26 is actively accessing its own DRAM DIMM 14 for read-modify-write (RMW, +/- Unity and Weighted) transactions into either 8-bit or 16-bit 2's-complement integer bins or 32-bit 2's- complement block-floating bins.
  • RMW read-modify-write
  • the DRAM address space is "quad-interleaved" with a 4 M byte “granularity.”
  • An Interleave Router 28 distributes the first four data packets A-B-C-D in order between DIMM1, DIMM2, DIMM3 and DIMM4.
  • This interleaving helps ensure that the normal distribution of LOR-to-bin mapping across the projection data space will load all four DRAM controllers 26 with nearly equal RMW rates, largely independent of the distribution of activity in the PET FOV.
  • Typical whole-body PET projection data spaces are much larger than 4 M bytes.
  • the FPGA 12B automatically "re-orders" the internal quad-interleaved 4 M byte organization upon DMA transfer of projection data out onto the PCI bus, thereby eliminating any user re-assembly burden.
  • the set-of-4 "FIFO 8 Deep" blocks 30 in FIG. 3 serve to greatly reduce the chance of packet pile-up and loss.
  • the SD RMW card 10B design also supports control methods, ie., frame-offset tag packet, to quickly offset the arriving bin-address into most any arbitrary portion of the local DRAM space and even across multiple cards in the daisy chain.
  • This bin-address offset control is applied in the "Bin Address Offset" block 32 of FIG. 3 and is critically important for realtime control of multiple-frame dynamic or multiple-phase-segment gated studies.
  • the SD RMW PCI card 10B of the present invention has demonstrated RMW (+/- unity) histogramming of real PET data at sustained rates in excess of 14 M events/sec.
  • RMW (+/- unity histogramming of real PET data at sustained rates in excess of 14 M events/sec.
  • over 14 billion (10 ⁇ ) PET 32- bit bin-address list-mode packets were successfully replayed for histogramming in 17 minutes. In this case histogramming speed was primarily limited by the PC disk system.
  • Early observations show that data transfers of DRAM contents from the SD RMW PCI card via PCI bus to PC-motherboard DRAM . are roughly 117 M bytes/sec for 32/33 PCI slot installations and 146 M bytes/sec for 64/66 PCI slot installation.
  • FIG. 4 is a schematic illustration of the FPGA 12A architecture as applied to the Gating Buffer function.
  • the FPGA 12A and DIMMs 14 are applied without interleaving or histogramming.
  • the Gating SD RMW PCI card 10A is provided primarily to store, or buffer, packets in the order of arrival into one of two DRAM 14 banks. While one bank is loading with data packets arriving in real time via FC input port 18, the other bankis typically unloading via FC output port. Data packet output is controlled by operating system-resident application code which drives autonomous FPGA-resident DMA controllers.
  • the PET packet stream arriving at the Gating Buffer is interspersed with both LOR (event) packets and other non-event (tag) packets.
  • Tag packet content includes elapsed milliseconds, cardiac R-wave, and respiratory phase data. Because the buffered event-and-tag-packet data stream is temporarily stored in local DRAM, more time is available for operating system control of how this data is handled. For example, packets may be directed for down-stream histograrnming into specific frames. In one embodiment, the LOR bin-address packet data is histogrammed into different projection-data frames depending on the cardiac phase. This phase may be determined by the elapsed-time tag packet content found in the Gating Buffer relative to any cardiac R-wave tag packets present. The control of which phase-segment frame is targeted for each designated section of the event stream is provided by the afore-mentioned bin-address offset tag control.
  • FIG 5. is a schematic illustration of a second PC-based acquisition architecture incorporating five SD PCI cards 10 of the present invention.
  • the SD PCI card 10 is applied in three ways.
  • One of the five SD PCI cards 10 is used as. a normalization (correction factor, CF) look-up table (LUT).
  • Another SD PCI card ie., SD Gating Buffer, is used in a manner similar to that in FIG 1., with the exception that the event packets received via the Fibre Channel, processed, and then retransmitted via the Fibre Channel, are each 64-bit weighted bin-address packets.
  • each event packet contains an extra field, the 16-bit CF value as added by the SD CF LUT PCI card.
  • the remaining 3 SD PCI cards are all configured to support weighted histogramming, namely, SD Weighted RMW, with each event packet transmitted down the Fibre Channel daisy chain, being of the type, 64-bit weighted bin-address.
  • the SD CF LUT PCI card 10 of the present invention is useful for on-line event-by-event normalization.
  • On-line normalization processing is useful in supporting, for example, continuous bed motion and correction of inadvertent patient motion.
  • Event-by-event normalization includes at ⁇ least the steps of correction value look-up in look up tables (LUTs) resident in . memory and weighted histogramming.
  • LUTs look up tables
  • the local DRAM is loaded prior to the start of the acquisition with a PET normalization correction matrix, which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair.
  • a PET normalization correction matrix which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair.
  • each respective 16-bit scalar correction value in block-floating format, is extracted from the local DRAM content.
  • the index into the local DRAM is formed by the FPGA from the detector- pair packet content, namely, the crystal-pair indexes.
  • Each extracted value is loaded into a designated field within each detector-pair packet.
  • This modified packet with correction value which is potentially larger than its original size, is then transmitted for further processing via the out-going 'FC port.
  • the FC output is, in one embodiment, connected to a custom PCI card for next-stage on-line processing such as nearest-neighbor rebinning such as in the PETLINKtm DMA Rebinner (PDR) card illustrated in both FIGS. 1 and 5.
  • PDR PETLINKtm DMA Rebinner
  • the SD RMW PCI card 10 performs histogramming in much the same mariner as previously described.
  • the daisy-chain of SD RMW PCI cards are FPGA-configured for weighted histograrnming.
  • each DRAM-resident RMW bin is a 32-bit 2's block-floating complement value.
  • the event packets input via the FC port are intermixed with conventional tag. packets. These event packets are called 64-bit weighted bin-address event packets.
  • the new packets contain not only the traditional Prompt/ Delayed (P/D) bit but also a bin-address field and the correction-value field.
  • the more traditional PET histogramming without the complexity of weighted histogramming, merely employs +/- unity RMW cycles into . 8-bit or 16-bit bins in memory.
  • the . correction value is added/ subtracted to/from the respective bin in DRAM memory, depending on the P/D bit.
  • the bin-address value is applied as a quad-byte index into local DRAM. Because both the correction value and the bin content are treated as block floating, the FPGA performs only signed- integer arithmetic for the RMW memory cycles.
  • the result of on-line weighted istogramming is that all projection-data sets resident in local DRAM are inherently corrected for pre-normalized detector efficiency variations during the entirety of the acquisition.
  • the block-floating format has an implied decimal point between bits 10 & 11. This implied decimal location applies uniformly to both a 16-bit correction value and a 32-bit bin value.
  • This assumption provides for normalization values - for example, an unsigned block-floating 16-bit correction value - to range from zero to values as high as 31.00 (5 bits to left of decimal), with a precision limit of +/- 0.00024 (11 bits to right of decimal).
  • a zero correction value may be used to effectively force a bad LOR to be ignored, i.e., a case where a pre- measured correction value is judged too extreme to be desirable.
  • the signed block-floating 32-bit bin values range as +/- 1048575 (20-bits plus sign bit to left of decimal).
  • the 32-bit bin precision limit is the same (+/- 0.00024) as the prior example.
  • Other correction factors supported by this specific choice for the location of the implied decimal include: zero, 0.04883, 0.04916, 1.0, 1.0005, 30.0, 30.0005, etc.
  • Other trade-offs between range and precision, ie., by selecting an alternate location for the implied decimal point are within the scope of the present invention and may also find application. In this context, the chosen location for the implied decimal point is not determined or limited by the FPGA configuration.
  • the device includes ⁇ a plurality of Smart DRAM peripheral component interconnect (SD RMW PCI) cards adapted to permit very fast read-modify- write (RMW, +/- Unity and Weighted) histogramming memory cycles, and to permit large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS).
  • SD RMW PCI cards are individually adapted to be used either as a Gating Buffer, for normalization look up, or for histogramming.
  • the present invention supports on-line gated PET data acquisition.

Abstract

A device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan. The device is a Smart DRAM (SD) PCI card, of which more than one can be used in combination within a PC-based architecture for on-line histogramming. The SD RMW PCI card is applied as either of a Gating Buffer, a histogramming card, and a normalization buffer. The Gating Buffer card alternately stores an arriving PET data packet stream into two dedicated DRAM banks. The two DRAM banks store and retransmit the packet stream in the order of arrival for an entire physiological cycle. The histogramming SD RMW PCI cards provide a very high rate of histogramming. The extendible daisy-chain of SD RMW PCI cards supports large memory banks across potentially hundreds of SD RMW PCI cards. Under a single PC, a multiple PCI Expansion chassis is employed such that a large number of PCI cards are supported.

Description

TITLE OF INVENTION DEVICE FOR ON-LINE DATA ACQUISITION IN THREE-DIMENSIONAL POSITRON EMISSION TOMOGRAPHY CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Provisional Application No.
60/571,275, Filed May 14, 2004.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION 1. Field of Invention
[0003] The present invention pertains to the field of Positron Emission
Tomography (PET). More particularly, this invention is directed to a dedicated memory device for extremely flexible and general purpose support of on-line event- by-event normalization, real-time physiological gating, unity (+/-) histogramming, and weighted histogramming.
2. Description of the Related Art
[0004] Various techniques are used for medical imaging. Positron emission tomography (PET) is one of several popular methods in radiology because of its ability to non-invasively study physiological processes and structures within the body. PET is a nuclear imaging technique used in the medical field to assist in the diagnosis of diseases. PET allows the physician to examine the whole patient at once by producing pictures of many functions of the human body unobtainable by other imaging techniques. In this regard, PET displays images of how the body works (physiology or function) instead of simply how it looks. PET- is considered the most sensitive, and exhibits the greatest quantification accuracy, of any nuclear medicine imaging instrument available at the present time. Applications requiring this sensitivity and accuracy include those in the fields of oncology, cardiology, and neurology. [0005] In PET, short-lived positron-emitting isotopes, referred to as radiopharmaceuticals, are injected into a patient. When these radioactive drugs are administered to a patient, they distribute within the body according to the physiologic pathways associated with their stable counterparts. As the radiopharmaceutical isotopes decay in the body, they discharge positively charged particles called positrons. Upon discharge, the positrons encounter electrons, and both are annihilated. As a result of each annihilation event, gamma rays are generated in the form of a pair of diametrically opposed photons approximately 180 degrees (angular) apart. After the PET scanner detects these annihilation "event pairs" over a period of time, the isotope distribution in a cross section, of the body is reconstructed. These events are mapped within the patient's body, thus allowing for the quantitative measurement of metabolic, biochemical, and functional activity in living tissue. More specifically, PET images (often in conjunction with an assumed physiologic model) are used to evaluate a variety of physiologic parameters such as glucose metabolic rate, cerebral blood flow, tissue viability, oxygen metabolism, and in vivo brain neuron activity.
[0006] For the current state-of-the-art in PET, critical technical challenges to data acquisition are frequently encountered. Clinical PET places a. demanding burden on the electronic data acquisition architecture, especially when using larger, higher sensitivity detector arrays coupled with demands for high patient ■throughput. Pure list-mode data acquisition, in which gamma-pair-coincidence event packets are simply stored to disk in the order detected, can have limited ' acceptance due to either too-slow event-packet collection speeds and/or too-slow post-acquisition processing. The typical resolution for this problem, which is well documented in the literature, has been to perform histogramming (+/- unity to memory) in an on-line manner. For example, projection space "sinograms" are generated during the acquisition while the patient is still in the tomograph. Still, this solution alone shows several limitations when upcoming requirements for modern large-array PET detectors are considered - ie., requirements such as .- dynamic studies, continuous bed motion, physiological gating, time-of-flight, and correction for patient motion. In the clinical setting, demands for high-patient throughput combined with these more complex data acquisition modalities result in a critical need for very capable and flexible electronic architectures to support on-line processing of the PET data stream. [0007] One example of a long-axis, high-count-rate PET is described by
Wienhard, et al, "The ECAT HRRT: Performance and First Clinical Application of the New High Resolution Research Tomograph," IEEE Trans. Nucl. Sci., vol. 49, pp. 104-110 (2002). Another example of long-axis, high-count-rate PET is described by Jones, et al, "First Time Measurement of Transaxial Resolution for a New High- Sensitivity PET Prototype Using 5 LSO Panel Detectors," IEEE NSS/ MIC Conf. Rec, 2002. For an example of work in support of list-mode continuous bed motion in PET, see Townsend, et al, "Continuous bed motion acquisition for an LSO PET/CT scanner" IEEE NSS/ MIC Poster, 2004 Rome. As an example of recent work in support of time-of-flight, refer to the work by Conti, et al, "Implentation of Time-of- Flight on CPS HiRez PET Scanner," IEEE NSS/ MIC Oral Presentation,.2004 Rome. For work in the field of list-mode correction of patient motion, see the article by Fulton, et al, "Event-by-event motion compensation in 3D PET", IEEE MIC Conf. Rec, October 2003.
[0008] So as broad progress in PET continues, important challenges must be met in digital electronic architectures to bring these multiple, complex data- acquisition modalities into the clinical world of high-patient throughput. As a basis for progress, note Section VIII from this 1996 article which proposes the use of quad-interleaved DRAM for fast on-line PET histogramming: Jones, et al, "Next generation PET data acquisition architectures," IEEE MIC Conf. Rec, (1996).
BRIEF SUMMARY OF THE INVENTION
[0009] The present invention is a device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan. The device of the present invention permits very fast read-modify- write (RMW, +/- unity and weighted) histogramming memory cycles, and permits very large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS). In support of this fast histogramming into very large, memory banks, the present invention also is configurable for on-line buffering of the coincidence packet stream, i.e., "gating buffer" which allows "bad beat" rejection and real-time phase-driven segmentation as needed for physiological cycles such as cardiac and respiratory. In addition, the present invention also provides an effective on-line mechanism for incorporating individual normalization correction factors into each coincidence event packet. [0010] The present invention is a Smart DRAM (SD) peripheral component interconnect (PCI) card, of which more than one can be used in combination within a PC-based architecture for on-line histogramming. The SD PCI card is applied in a plurality of ways. Specifically, the SD PCI card is used as either of a Gating Buffer, a histogramming card, or a look up table (LUT) for normalization correction factors.
[0011] The Correction Factor LUT SD PCI card (SD CF LUT) serves to insert a
16-bit correction factor into arriving packets prior to packet retransmittal. These correction factors are retrieved from local RAM as each coincidence event packet arrives, using the contents of the arriving packets to form an index (address) into the local RAM. These correction factors serve to correct for PET detector variability in gamma detection efficiency, ie., "normalization." The retransmitted packets are expanded in size to provide room for the inserted correction factor.
[0012] The Gating Buffer card alternately stores an arriving PET data packet stream into two dedicated DRAM banks. The two DRAM banks store and retransmit the packet stream in the order of arrival for an entire physiological cycle. This buffering enables on-line rejection of "bad-beat" cycles and serves the more complex needs of real-time cardiac/ respiratory gating.
[0013] The SD RMW PCI cards provide a very high rate of histogramming.
The extendible daisy-chain of SD RMW PCI cards supports large memory banks across potentially hundreds of SD RMW PCI cards. Under control όf a single PC, a PCI Expansion chassis is employed such that a large number of PCI cards are supported. This off-the-shelf PCI expansion chassis system (StarFabric) is itself extendible allowing hundreds of PCI slots to be accessed from a single PC.
[0014] The present invention is further applicable to rapid dynamic, dynamic-gated, continuous bed motion, time-of-flight (TOF), gated-TOF, and correction for patient motion, and all in an on-line manner while the patient remains in the tomograph. In addition to on-line capability, the present invention further supports both list-mode-only data acquisition as well as for rapid replay in post-acquisition histogramming of previously collected list-mode data.
[0015] For effective index/ offset control into the potential Terabytes of DRAM space, frame-offset tag packets are used. As a means to direct which frame or phase-segment portion of the bin-space is accessed for RMW activity, these offset- control tag packets are input to the Gating Buffer card under control of application software. The offset packets are intermixed with bin-address event packets, all from the Gating Buffer FC output port for reception by the down-stream SD RMW PCI cards. The bin-offset values within these tag packets are received and used by each downstream SD-RMW-resident FPGA to instantly direct histogramming into the designated projection frame throughout the array of SD RMW PCI cards. The. FPGA on each SD RMW PCI card in the chain is directed from the PC operating system via FPGA-resident PCI-loaded registers to respond to only a designated card-size portion of the available projection-data bin space. This bin space is spread across all the SD RMW PCI cards in the chain. Thus, the offset-control tag- packet mechanism is an effective means to instantly direct bin-address activity into any part of the RMW daisy chain via minimal PCI interaction.
[0016] The component architecture internal to each SD RMW PCI card includes a single field programmable gate array (FPGA) in communication with RAM and with the input/ output (I/O) flow, including I/O via at least one Fibre Channel (FC) and a PCI interface. Each of a plurality of DRAM modules is independently in communication with the FPGA to permit independent and simultaneous direct memory access (DMA) to each bank, thus optimizing throughput. The FPGA is in communication with each local Fibre Channel port. Each port consists of a transceiver, typically fiber' optic, and a serializer/ deserializer (SERDES) chip. Also provided in communication with the FPGA is a first in, first out (FIFO) memory chip.
[0017] In the histogramming SD PCI card, ie., SD RMW, the FPGA architecture includes independent DRAM Controllers for actively accessing dedicated DRAM modules for read-modify-write (RMW) transactions. These RMW transactions take two forms. For +/- unity RMW, the transactions involve adding unity to or subtracting unity from individual bins in the DRAM memory. These Unity RMW bins are 2's complement integer values stored as either 8-bit or 16-bit. For Weighted RMW, the transactions involve adding a correction factor to or . subtracting a correction factor from individual bins in the DRAM memory. These Weighted RMW bins are 2's complement "block floating" values and. are typically stored as 32-bit only. [0018] Also for the SD RMW application, the DRAM bin- address space is quad-interleaved with the assistance of an FPGA-resident Interleave Router. This Router supports quad-interleaving by distributing, according to address-value content, bin-address data packets to each of the four FPGA-resident FIFO blocks and their associated DRAM modules. These FPGA-resident FIFO blocks are provided to greatly reduce the chance of packet pile-up and loss. FPGA-resident bin-address offset control is applied to assist in real-time control of multiple-frame dynamic or multiple-phase-segment gated studies. After histogramming is completed for a DRAM-resident projection space and as the projection-space data is read, the FPGA automatically reorders the internal quad-interleaved organization during DMA transfer out to PCI bus, eliminating the need for subsequent user reassembly of the final projection data set.
[0019] In the Gating Buffer card, the FPGA and DIMMs are applied without interleaving or histogramming. The Gating SD PCI card is provided primarily to buffer packets in the order of arrival into one of two DRAM banks. While one bank . is loading with data packets arriving in real time via FC input port, the other bank is unloading via FC output port. Data packet output is controlled by operating system-resident application code which drives autonomous FPGA-resideήt DMA controllers. The PET packet stream arriving at the Gating Buffer is interspersed with both LOR (event) packets and other non-event (tag) packets. Tag packet content includes elapsed milliseconds, cardiac R-wave, and respiratory phase data.
[0020] For the correction factor look-up function (ie., SD CF LUT), the local
DRAM is loaded prior to the start of the acquisition with a PET normalization correction matrix, which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair. As each detector-pair packet arrives via an FC port from the PET Gantry, each respective scalar correction value, in block-floating format, is extracted from the local DRAM content. The index into the local DRAM is formed by the FPGA from the detector-pair packet content, namely, the crystal-pair indexes. An extracted correction factor value is loaded, ie., inserted, into a designated field within the detector-pair packet. This modified packet with correction value, which is potentially larger than its original size, is then transmitted for further processing via the out-going FC port. [0021] For the weighted histograrnming function, ie., SD Weighted RMW, each DRAM-resident RMW bin is a 32-bit 2's complement block-floating value. The event packets input via the FC port are intermixed with conventional tag packets. These event (non-tag) packets are called weighted bin-address event packets. These weighted bin-address event packets contain not only the traditional Prompt/ Delayed (P/D) bit but also a bin-address field and the correction-value field. A correction value is added/ subtracted to/from the respective bin in DRAM memory, depending on the P/D bit. In this mode of operation with 32-bit bins, the bin-address value is applied as a quad-byte index into local DRAM. Because both the correction value and the bin content are treated as block floating, the FPGA performs only signed-integer arithmetic for the RMW memory cycles.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0022] The above-mentioned, features of the invention will become more clearly understood from the following detailed description of the invention read together with the drawings in which:
FIG. 1 is a schematic illustration of a PC-based acquisition architecture incorporating four Smart DRAM (SD) peripheral component interconnect (PCI) cards incorporating various features of the present invention, one SD PCI card being shown for on-line gating, i.e., SD Gating Buffer, and three SD PCI cards being shown for on-line unity histogramming, i e., SD Unity RMW;
FIG. 2 is a schematic illustration of the component architecture internal to the Smart DRAM PCI card incorporated in the architecture illustrated in FIG. 1;
FIG. 3 is a schematic illustration of an FPGA architecture as applied to histogramming;
FIG. 4 is a schematic illustration of the FPGA architecture as applied to the Gating Buffer function; and
FIG. 5 is a schematic illustration of a PC-based acquisition architecture . incorporating five Smart DRAM (SD) peripheral component interconnect (PCI) cards incorporating various features of the present invention, one SD PCI card being shown for on-line normalization, ie., SD CF LUT, one SD card being shown for on- line gating, i.e., SD Gating Buffer, and three SD PCI cards shown for on-line weighted Wstogramming, ie., SD Weighted RMW.
DETAILED DESCRIPTION OF THE INVENTION [0023] A device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan is disclosed. The device of the present invention permits very fast read-modify- write (RMW, +/- unity and weighted) histogramming memory cycles, and permits very large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS).
[0024] FIG. 1 is a schematic illustration of a PC-based acquisition architecture incorporating four Smart DRAM (SD) peripheral component interconnect (PCI) cards of the present invention, illustrated generally at 10. In the illustrated system, the SD PCI card 10 is applied in two ways. One of the four SD PCI cards 10A is used as a Gating Buffer, while the remaining three SD PCI cards 10B are used for unity RMW histograrnming. This embodiment principally supports on-line gated PET data acquisition. Histogramming rates in the range from 14 to 19 M events/ sec are supported. It will be understood, however, that other rates outside this range may be accomplished using architectures within the scope of the present invention. With an extendible daisy-chain, very large projection data sets are supportable, for example, 1012 bins.
[0025] The Gating Buffer card 10A alternately stores an arriving PET data
, packet stream into one of two dedicated DRAM 14 banks. (FIG. 2) The two DRAM banks store and retransmit the packet stream in the order of arrival for an entire physiological cycle. This buffering enables on-line rejection of "bad-beat" cycles, e.g., too long or too short in duration, and serves the more complex needs of real- , time cardiac/respiratory gating. The Histograrnming function provided on the remaining three SD RMW PCI cards 10B of the present invention is such that the heavy on-line RMW burden is eliminated from loading down both the PC-CPU and PC-resident DRAM. A daisy chain of histogramming SD RMW PCI .cards 10B is i illustrated in FIG. 1 and provides a very high rate of histogramming. For example, histogramming at a rate of 14 to 19 M events/ sec is possible. The extendible daisy- chain of SD RMW PCI cards 10B supports large memory banks, limited to ~10*2 bins (1-4 Terabytes) across potentially hundreds of SD RMW PCI cards 10B in the chain, as required. Under a single PC, a multiple PCI Expansion chassis 16 is provided such that a large number of SD RMW PCI cards 10B are supported. The SD RMW PCI design effectively solves the problem of limited address space found in current PC systems. Specifically, a moveable 4 Mbyte PCI DMA window is defined for fast and effective DMA transfers into the PC motherboard of the huge, ie., not conventionally addressable, sets of projection data. Further, flow control signaling (not fully illustrated) may be sent upstream between the full- duplex FC links 18.
[0026] While the architecture in FIG. 1 is significant for on-line gated studies, it is also effective for many other, even more demanding on-line acquisition types. These include, but are not limited to, rapid dynamic, dynamic-gated, continuous bed motion, time-of-flight (TOF), gated-TOF, and correction for patient motion. The present invention further supports both list-mode-only data acquisition as well as for rapid replay in post- acquisition histogramming of previously collected list-mode data.
[0027] For effective index/ offset control into the potential Terabytes of DRAM space, frame-offset tag packets are used. As a means to direct which frame or phase-segment portion of the bin-space is accessed for RMW activity, these offset- control tag packets are input to the Gating Buffer card 10A under control of PC- OS-based application software. The offset tag packets are intermixed with bin- address event packets. These packets are all output from the Gating Buffer FC port for reception by the down-stream SD RMW PCI cards 10B. The bin-offset values in these tag packets are received and used by the FPGA 12B on each of the down-stream SD RMW PCI cards 10B to instantly direct histogramming into the designated projection frame, ie., some portion of the memory space across all the histogramming SD RMW PCI cards 10. The use of the Fibre Channel daisy chain to distribute the frame-offset value to all SD RMW PCI cards 10 minimizes the application code interaction with PCI-accessed FPGA-resident control registers, ie., one frame-offset register access into the SD Gating Buffer card with FC daisy chain distribution of the value avoids the need for multiple and more time-critical PCI registers accessed across multiple SD RMW PCI cards 10. The FPGA 10B on each of SD RMW PCI cards 10B in the chain is directed from the PC operating system via FPGA-resident PCI-loaded registers to respond to only a designated card-size (for example, 4 Gbyte) portion of the available 40-bit projection-data bin space. This bin space is spread across all the SD RMW PCI cards 10B in the chain and is limited to 40-bit indexing. Thus, the offset-control tag-packet mechanism is an effective means to instantly direct bin-address activity into any part of the RMW daisy chain via minimal PCI interaction.
[0028] FIG. 2 is a schematic illustration of the component architecture internal to each SD RMW PCI card 10 of the present invention. Each box in the diagram represents a chip or component on the card 10. A single field programmable gate array (FPGA) 12A, 12B is in communication with the RAM 14 and with the input/ output (I/O) flow, including I/O via at least one Fibre Channel (FC) 18 and a PCI interface 20. This architecture achieves maximum flexibility and permits a single board design to service multiple applications. In the illustrated embodiment, four DRAM dual in-line memory modules (DIMMs) 14 are each independently in communication with the FPGA 12A, 12B to permit independent and simultaneous direct memory access (DMA) to each bank, thus optimizing throughput. While DRAM banks 14 are illustrated and described, it will be understood that other RAM configurations may be used within the scope of the present invention. The FPGA 12A, 12B is in communication with each Fibre Channel port 18 via a transceiver 22 and a serializer/ deserializer (SERDES) chip 24. Also provided in communication with the FPGA 12A 12B is a first in, first out (FIFO) memory chip 26.
[0029] FIG. 3 is a schematic illustration of the FPGA architecture as applied to histogramming. This embodiment assists in accomplishing a primary method for achieving fast histograrnming throughput through the use of quad-interleaving. As shown in FIG. 3, each independent DRAM Controller 26 is actively accessing its own DRAM DIMM 14 for read-modify-write (RMW, +/- Unity and Weighted) transactions into either 8-bit or 16-bit 2's-complement integer bins or 32-bit 2's- complement block-floating bins.
[0030] In this configuration, the DRAM address space is "quad-interleaved" with a 4 M byte "granularity." This means that normal memory space content ordering of "ABCDEFGH..." where each letter represents 4 M bytes of the projection data space is here intentionally reordered to be "AE..." for DIMM1, ."BF..." for DIMM2, "CG..." for DIMM3 and "DH..." for DIMM4. An Interleave Router 28 distributes the first four data packets A-B-C-D in order between DIMM1, DIMM2, DIMM3 and DIMM4. This interleaving helps ensure that the normal distribution of LOR-to-bin mapping across the projection data space will load all four DRAM controllers 26 with nearly equal RMW rates, largely independent of the distribution of activity in the PET FOV. Typical whole-body PET projection data spaces are much larger than 4 M bytes. The FPGA 12B automatically "re-orders" the internal quad-interleaved 4 M byte organization upon DMA transfer of projection data out onto the PCI bus, thereby eliminating any user re-assembly burden. In addition, the set-of-4 "FIFO 8 Deep" blocks 30 in FIG. 3 serve to greatly reduce the chance of packet pile-up and loss. As mentioned, the SD RMW card 10B design also supports control methods, ie., frame-offset tag packet, to quickly offset the arriving bin-address into most any arbitrary portion of the local DRAM space and even across multiple cards in the daisy chain. This bin-address offset control is applied in the "Bin Address Offset" block 32 of FIG. 3 and is critically important for realtime control of multiple-frame dynamic or multiple-phase-segment gated studies.
[0031] In testing, the SD RMW PCI card 10B of the present invention has demonstrated RMW (+/- unity) histogramming of real PET data at sustained rates in excess of 14 M events/sec. For one of these tests, over 14 billion (10ή) PET 32- bit bin-address list-mode packets were successfully replayed for histogramming in 17 minutes. In this case histogramming speed was primarily limited by the PC disk system. From the resulting 640 M byte projection data set generated by the SD RMW PCI card 10B, a viable 3-D PET image was produced off-card using conventional image reconstruction. Early observations show that data transfers of DRAM contents from the SD RMW PCI card via PCI bus to PC-motherboard DRAM . are roughly 117 M bytes/sec for 32/33 PCI slot installations and 146 M bytes/sec for 64/66 PCI slot installation.
[0032] FIG. 4 is a schematic illustration of the FPGA 12A architecture as applied to the Gating Buffer function. In this embodiment, the FPGA 12A and DIMMs 14 are applied without interleaving or histogramming. The Gating SD RMW PCI card 10A is provided primarily to store, or buffer, packets in the order of arrival into one of two DRAM 14 banks. While one bank is loading with data packets arriving in real time via FC input port 18, the other bankis typically unloading via FC output port. Data packet output is controlled by operating system-resident application code which drives autonomous FPGA-resident DMA controllers. The PET packet stream arriving at the Gating Buffer is interspersed with both LOR (event) packets and other non-event (tag) packets. Tag packet content includes elapsed milliseconds, cardiac R-wave, and respiratory phase data. Because the buffered event-and-tag-packet data stream is temporarily stored in local DRAM, more time is available for operating system control of how this data is handled. For example, packets may be directed for down-stream histograrnming into specific frames. In one embodiment, the LOR bin-address packet data is histogrammed into different projection-data frames depending on the cardiac phase. This phase may be determined by the elapsed-time tag packet content found in the Gating Buffer relative to any cardiac R-wave tag packets present. The control of which phase-segment frame is targeted for each designated section of the event stream is provided by the afore-mentioned bin-address offset tag control.
[0033] FIG 5. is a schematic illustration of a second PC-based acquisition architecture incorporating five SD PCI cards 10 of the present invention. In the illustrated system, the SD PCI card 10 is applied in three ways. One of the five SD PCI cards 10 is used as. a normalization (correction factor, CF) look-up table (LUT). Another SD PCI card, ie., SD Gating Buffer, is used in a manner similar to that in FIG 1., with the exception that the event packets received via the Fibre Channel, processed, and then retransmitted via the Fibre Channel, are each 64-bit weighted bin-address packets. Specifically, each event packet contains an extra field, the 16-bit CF value as added by the SD CF LUT PCI card. The remaining 3 SD PCI cards are all configured to support weighted histogramming, namely, SD Weighted RMW, with each event packet transmitted down the Fibre Channel daisy chain, being of the type, 64-bit weighted bin-address.
[0034] As shown in FIG. 5, the SD CF LUT PCI card 10 of the present invention is useful for on-line event-by-event normalization. On-line normalization processing is useful in supporting, for example, continuous bed motion and correction of inadvertent patient motion. Event-by-event normalization includes at ■least the steps of correction value look-up in look up tables (LUTs) resident in . memory and weighted histogramming.
[0035] For the correction value look-up function, the local DRAM is loaded prior to the start of the acquisition with a PET normalization correction matrix, which is an array of scalar values which reflect the reciprocal of the varied gamma detection efficiencies as pre-determined for each detector pair. As each detector- pair packet arrives via an FC port from the PET Gantry, each respective 16-bit scalar correction value, in block-floating format, is extracted from the local DRAM content. The index into the local DRAM is formed by the FPGA from the detector- pair packet content, namely, the crystal-pair indexes. Each extracted value is loaded into a designated field within each detector-pair packet. This modified packet with correction value, which is potentially larger than its original size, is then transmitted for further processing via the out-going 'FC port. The FC output is, in one embodiment, connected to a custom PCI card for next-stage on-line processing such as nearest-neighbor rebinning such as in the PETLINKtm DMA Rebinner (PDR) card illustrated in both FIGS. 1 and 5.
[0036] For the weighted histogramming function, the SD RMW PCI card 10 performs histogramming in much the same mariner as previously described. However, for on-line normalization, the daisy-chain of SD RMW PCI cards are FPGA-configured for weighted histograrnming. For this case, each DRAM-resident RMW bin is a 32-bit 2's block-floating complement value. The event packets input via the FC port are intermixed with conventional tag. packets. These event packets are called 64-bit weighted bin-address event packets. The new packets contain not only the traditional Prompt/ Delayed (P/D) bit but also a bin-address field and the correction-value field. The more traditional PET histogramming, without the complexity of weighted histogramming, merely employs +/- unity RMW cycles into . 8-bit or 16-bit bins in memory. By contrast, for weighted histograrnming, the . correction value is added/ subtracted to/from the respective bin in DRAM memory, depending on the P/D bit. In this mode of operation, the bin-address value is applied as a quad-byte index into local DRAM. Because both the correction value and the bin content are treated as block floating, the FPGA performs only signed- integer arithmetic for the RMW memory cycles. The result of on-line weighted istogramming is that all projection-data sets resident in local DRAM are inherently corrected for pre-normalized detector efficiency variations during the entirety of the acquisition.
[0037] Typically, the block-floating format has an implied decimal point between bits 10 & 11. This implied decimal location applies uniformly to both a 16-bit correction value and a 32-bit bin value. This assumption provides for normalization values - for example, an unsigned block-floating 16-bit correction value - to range from zero to values as high as 31.00 (5 bits to left of decimal), with a precision limit of +/- 0.00024 (11 bits to right of decimal). A zero correction value may be used to effectively force a bad LOR to be ignored, i.e., a case where a pre- measured correction value is judged too extreme to be desirable. Similarly, the signed block-floating 32-bit bin values range as +/- 1048575 (20-bits plus sign bit to left of decimal). The 32-bit bin precision limit is the same (+/- 0.00024) as the prior example. Other correction factors supported by this specific choice for the location of the implied decimal include: zero, 0.04883, 0.04916, 1.0, 1.0005, 30.0, 30.0005, etc. Other trade-offs between range and precision, ie., by selecting an alternate location for the implied decimal point are within the scope of the present invention and may also find application. In this context, the chosen location for the implied decimal point is not determined or limited by the FPGA configuration.
[0038] There is a small accumulation of error in on-line normalization that occurs with this limited-precision block-floating approach. Consider a specific 32- bit bin in the projection space that has been indexed by, for example, 100 LOR, ie., this bin has seen 100 weighted-RMW cycles. If the 100 RMW cycles involve correction factors that are all near unity, ranging from 0.845 to 1.155, for example, there is an accumulating error on the final 32-bit bin value that might in a rare case approach 100 * 0.00024 = 0.024. This error is roughly 0.024% of the final bin value of approximately 100. Compared to the percent standard deviation for a statistical count of 100, ie., 10%, this example for a rather extreme case with this very small magnitude of error (0.024%) validates the use of the SD Weighted RMW PCI card for limited-precision on-line normalization method.
[0039] From the foregoing description, it will be recognized by those skilled in the art that a device for improved on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan has been provided. The device includes ■ a plurality of Smart DRAM peripheral component interconnect (SD RMW PCI) cards adapted to permit very fast read-modify- write (RMW, +/- Unity and Weighted) histogramming memory cycles, and to permit large amounts of RMW memory to be effectively controlled from a single PC motherboard running a single operating system (OS). The SD RMW PCI cards are individually adapted to be used either as a Gating Buffer, for normalization look up, or for histogramming. The present invention supports on-line gated PET data acquisition.
[0040] While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant's general inventive concept.

Claims

CLAIMS Having thus described the aforementioned invention, we claim:
1. A device for on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan, said device comprising: at least one interface unit configured to function as one of a gating buffer, a histogramming device, and a normalization buffer, said at least one interface unit including: a field programmable gate array (FPGA); at least one memory device in communication with said FPGA; at least one input/ output (I/O) device in communication with said FPGA; and a first in, first out (FIFO) memory chip in communication with the FPGA.
2. The device of Claim 1 wherein said at least one interface unit is a peripheral component interconnect (PCI) card.
3. The device of Claim 2 wherein said at least one memory device includes a plurality of DRAM devices, wherein each of said plurality of DRAM devices is independently in communication with said FPGA, whereby independent and simultaneous direct memory access (DMA) to each of said plurality of DRAM devices is permitted and throughput is optimized.
4. The device of Claim 2 wherein said at least on I/O device includes: . at least one Fibre Channel (FC), said device further comprising at least one transceiver and a data serializer/ deserializer (SERDES) device in ' communication between said FPGA and said at least one FC; and a PCI interface.
5. The device of Claim 3 wherein said PCI card is configured to - function as a gating buffer, wherein said plurality of DRAM devices defines a first dedicated DRAM bank and a second dedicated DRAM bank, wherein an arriving PET data packet stream is alternately written into one said first dedicated DRAM bank and said second dedicated DRAM bank, while data previously written into the other of said first dedicated DRAM bank and said second dedicated DRAM bank is being read.
6. The device of Claim 5 wherein frame offset-control tag packets are input to said PCI card to identify a portion of bin-space to be accessed for read- modify-write (RMW) activity, said frame offset-control tag packets being intermixed with bin-address event packets within said PCI card and output, from said PCI card to instantly direct histogramming performed downstream of said PCI card.
7. The device of Claim 5 wherein correction factors are inserted into bin-address event packets within said PCI card.
8. The device of Claim 7 wherein said correction factors are utilized during on-line PET data acquisition in block-floating format.
9. The device of Claim. 8 wherein said PCI card is configured to function as a normalization buffer for on-line event-by-event normalization ' including at least the steps of looking up correction values in look up tables (LUTs) and weighted histogramming.
10. The device of Claim 3 further comprising: a plurality of said PCI cards, said device further comprising a PCI expansion chassis for interfacing each of said plurality of PCI cards, each of said plurality of PCI cards being configured to perform a histogramming function, each of said plurality of PCI cards being in serial communication in a daisy chain method; ' said FPGA including: a plurality of DRAM controllers, one each of said plurality of DRAM controllers being provided for individually controlling one of said plurality of DRAM devices; and an interleave router for distributing RMW activity by means of either of dual and quad interleaving between said plurality of DRAM devices via said respective plurality of DRAM controllers,- said FPGA reordering said data packets upon DMA transfer of projection data.
11. The device of Claim 3 wherein said PCI card is configured to function as a normalization buffer for on-line event-by-event normalization including at least the steps of looking up correction values in look up tables (LUTs) and weighted histogramming.
12. The device of Claim 3 wherein said PCI card is adapted to perform at least one function selected from at least rapid dynamic, dynamic-gated, continuous bed motion correction, time-of-flight (TOF), gated-TOF, and correction of patient motion.
13. The device of Claim 3 wherein said PCI card is adapted for list- mode-only data acquisition as well as for rapid replay in post-acquisition histogramming of previously collected list-mode data.
14. A device for on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan, .said device comprising: . a first peripheral component interconnect (PCI) card configured to function as a gating buffer; a plurality of second PCI cards configured to perform a histograrnming function, each of said plurality Of second PCI cards being in serial communication in a daisy chain method; each of said first PCI card and said plurality of second PCI cards including: a field programmable gate array (FPGA); at least one memory device in communication with said FPGA; at least one input/ output (I/O) device in communication with said FPGA; and a first in, first out (FIFO) memory chip in communication with the FPGA.
15. The device of Claim 14 wherein said at least one memory device includes a plurality of DRAM devices, wherein each of said plurality of DRAM devices is independently in communication with said FPGA, whereby independent and simultaneous direct memory access (DMA) to each of said plurality of DRAM devices is permitted and throughput is optimized.
16. The device of Claim 14 wherein said at least one I/O device includes: at least one Fibre Channel (FC), said device further comprising at least one transceiver and a data serializer/ deserializer (SERDES) device in communication between said FPGA and said at least one FC; and a PCI interface.
17. The device of Claim 15 wherein said plurality of DRAM devices defines a first dedicated DRAM bank and a second dedicated DRAM bank, wherein an arriving PET data packet stream is alternately written into one said first dedicated DRAM bank and said second dedicated DRAM bank, while data previously written into the other of said first dedicated DRAM bank and said second dedicated DRAM bank is being read.
18. The device of Claim 17 wherein frame offset-control tag packets are input to said PCI card to identify a portion of bin-space to be accessed for read-modify-write (RMW) activity, said frame offset-control tag packets being intermixed with bin-address event packets within said PCI card and output from said PCI card to instantly direct histogramming performed downstream of said PCI card.
19. The device of Claim 14 wherein said FPGA includes: a plurality of DRAM controllers, one each of said plurality of DRAM controllers being provided for individually controlling one of said plurality of DRAM devices; and an interleave router for distributing RMW activity by means of- either of dual and quad interleaving between said plurality of DRAM devices via said respective plurality of DRAM controllers, said FPGA reordering said data packets upon DMA transfer of projection data.
20. A device for on-line histogramming of data acquired in a Positron Emission Tomography (PET) scan, said device comprising: a first peripheral component interconnect (PCI) card configured to , function as a gating buffer; a plurality of second PCI cards configured to perform a histograrnrning function, each of said plurality of second PCI cards being in serial communication in a daisy chain method; each of said first PCI card and said plurality of second PCI cards including: a field programmable gate array (FPGA); a plurality of DRAM devices, wherein each of said plurality of DRAM devices is independently in communication with said FPGA, whereby independent and simultaneous direct memory access (DMA) to each of said plurality of DRAM devices is permitted and throughput is optimized; at least one input/ output (I/O) device in communication with said FPGA, said at least on I/O device includes: at least one Fibre Channel (FC), said device further comprising at least one transceiver and a data serializer/ deserializer (SERDES) device in communication between . said FPGA and said at least one FC; and a PCI interface; and a first in, first out (FIFO) memory chip in communication with the FPGA; wherein said plurality of DRAM devices associated with said first PCI card defines a first dedicated DRAM bank and a second dedicated DRAM bank, wherein an arriving PET data packet stream is alternately, written into one said first dedicated DRAM bank and said second dedicated DRAM bank, while data previously written into the other of said first dedicated DRAM bank and said second dedicated DRAM bank is being read, and wherein frame offset-control tag packets are input to said first PCI card to identify a portion of bin- space to be accessed for read-modify-write (RMW) activity, said frame offset-control tag packets being intermixed with bin-address event packets within said first PCI card and output from said first PCI card to instantly direct histogramming performed by said plurality of said second PCI cards; and wherein said FPGA associated with each of said plurality of second PCI cards includes: a plurality of DRAM controllers, one each of said plurality of DRAM controllers being provided for individually controlling one of said plurality of DRAM devices; and an interleave router for distributing RMW activity by means of either of dual and quad interleaving between said plurality of DRAM devices via said respective plurality of DRAM controllers, said FPGA reordering said data packets upon DMA transfer of. projection data.
EP05752291A 2004-05-14 2005-05-16 Device for on-line data acquisition in three-demensional positron emission tomography Withdrawn EP1761803A4 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US57139904P 2004-05-14 2004-05-14
PCT/US2005/017172 WO2005114255A2 (en) 2004-05-14 2005-05-16 Device for on-line data acquisition in three-demensional positron emission tomography

Publications (2)

Publication Number Publication Date
EP1761803A2 true EP1761803A2 (en) 2007-03-14
EP1761803A4 EP1761803A4 (en) 2011-01-12

Family

ID=35429011

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05752291A Withdrawn EP1761803A4 (en) 2004-05-14 2005-05-16 Device for on-line data acquisition in three-demensional positron emission tomography

Country Status (3)

Country Link
EP (1) EP1761803A4 (en)
JP (1) JP4503072B2 (en)
WO (1) WO2005114255A2 (en)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5397001B2 (en) * 2009-05-08 2014-01-22 株式会社島津製作所 Nuclear medicine data collection method and nuclear medicine diagnostic apparatus
JP5339562B2 (en) * 2010-03-30 2013-11-13 独立行政法人放射線医学総合研究所 Imaging method and system of nuclear medicine imaging apparatus, nuclear medicine imaging system and radiotherapy control system
JP5806484B2 (en) 2011-03-09 2015-11-10 株式会社東芝 Positron emission computed tomography system
EP3291096B1 (en) * 2016-05-27 2020-01-15 Huawei Technologies Co., Ltd. Storage system and device scanning method

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030020964A1 (en) * 2001-01-31 2003-01-30 General Electric Company Detector framing node architecture to communicate image data

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6975752B2 (en) * 2001-01-31 2005-12-13 General Electric Company Imaging system including detector framing node

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20030020964A1 (en) * 2001-01-31 2003-01-30 General Electric Company Detector framing node architecture to communicate image data

Non-Patent Citations (8)

* Cited by examiner, † Cited by third party
Title
FRESSE V ET AL: "ARIAL: rapid prototyping for mixed and parallel platforms", PARALLEL COMPUTING, ELSEVIER PUBLISHERS, AMSTERDAM, NL, vol. 28, no. 7-8, 1 August 2002 (2002-08-01), pages 1179-1202, XP004375039, ISSN: 0167-8191, DOI: DOI:10.1016/S0167-8191(02)00111-4 *
FROSS B K ET AL: "WILDFIRE(TM) heterogeneous adaptive parallel processing systems", PARALLEL PROCESSING SYMPOSIUM, 1998. IPPS/SPDP 1998. PROCEEDINGS OF TH E FIRST MERGED INTERNATIONAL ... AND SYMPOSIUM ON PARALLEL AND DISTRIB UTED PROCESSING 1998 ORLANDO, FL, USA 30 MARCH-3 APRIL 1998, LOS ALAMITOS, CA, USA,IEEE COMPUT. SOC, US, 30 March 1998 (1998-03-30), pages 611-615, XP010276751, DOI: DOI:10.1109/IPPS.1998.669989 ISBN: 978-0-8186-8404-3 *
JONES F ET AL: "Next Generation PET Data Acquisition Architectures", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 44, no. 3, 1 June 1997 (1997-06-01), pages 1202-1207, XP011087668, ISSN: 0018-9499, DOI: DOI:10.1109/23.596988 *
MCBADER S ET AL: "A programmable image signal processing architecture for embedded vision systems", DIGITAL SIGNAL PROCESSING, 2002. DSP 2002. 2002 14TH INTERNATIONAL CON FERENCE ON SANTORINI, GREECE 1-3 JULY 2002, PISCATAWAY, NJ, USA,IEEE, US, vol. 2, 1 July 2002 (2002-07-01), pages 1269-1272, XP010600085, ISBN: 978-0-7803-7503-1 *
RAUPP G ET AL: "A ''Universal Time'' system for ASDEX upgrade", FUSION ENGINEERING AND DESIGN, ELSEVIER SCIENCE PUBLISHERS, AMSTERDAM, NL, vol. 66-68, 1 September 2003 (2003-09-01), pages 947-951, XP004456598, ISSN: 0920-3796, DOI: DOI:10.1016/S0920-3796(03)00381-8 *
SALCIC Z ET AL: "IMECO: a reconfigurable FPGA-based image enhancement co-processor framework", TENCON '97. IEEE REGION 10 ANNUAL CONFERENCE. SPEECH AND IMAGE TECHNOL OGIES FOR COMPUTING AND TELECOMMUNICATIONS., PROCEEDINGS OF IEEE BRISBANE, QLD., AUSTRALIA 2-4 DEC. 1997, NEW YORK, NY, USA,IEEE, US, 1 January 1997 (1997-01-01), pages 231-234VOL.1, XP031172444, DOI: DOI:10.1109/TENCON.1997.647300 ISBN: 978-0-7803-4365-8 *
See also references of WO2005114255A2 *
TOLEDO J ET AL: "A fast and compact histogramming solution for gas-filled detectors with delay line", 19 October 2003 (2003-10-19), 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD. / 2003 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE. PORTLAND, OR, OCT. 19 - 25, 2003; [IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD], NEW YORK, NY : IEEE, US, PAGE(S) 1685 -, XP010735936, ISBN: 978-0-7803-8257-2 * the whole document * *

Also Published As

Publication number Publication date
JP4503072B2 (en) 2010-07-14
WO2005114255A3 (en) 2007-06-07
EP1761803A4 (en) 2011-01-12
WO2005114255A2 (en) 2005-12-01
JP2007537458A (en) 2007-12-20

Similar Documents

Publication Publication Date Title
US7676070B2 (en) Device for on-line data acquisition in three-dimensional positron emission tomography
WO2005114044A2 (en) Nearest-neighbor rebinning in clinical pet using on-line three-dimensional lor-to-bin mapping
US7705314B2 (en) Method and apparatus for PET time of flight generation of compression sinogram and image reconstruction
JP4159288B2 (en) Imaging system including a detector framing node
Haber et al. Application of mathematical removal of positron range blurring in positron emission tomography
US7409077B2 (en) Nearest-neighbor rebinning in clinical PET using on-line three dimensional LOR-to-bin mapping
CN106725573A (en) A kind of counting loss bearing calibration for continuously entering a PET system and device
WO2005114255A2 (en) Device for on-line data acquisition in three-demensional positron emission tomography
US20100186017A1 (en) System and method for medical image processing
US20150260857A1 (en) Virtual frames for distributed list-mode time-of-flight reconstruction with continuous bed movement
EP0294089B1 (en) Data acquisition circuit
US10534096B1 (en) Photon scatter imaging
Martinez et al. High-speed data acquisition and digital signal Processing system for PET imaging techniques applied to mammography
Jones et al. Next generation PET data acquisition architectures
US10598801B2 (en) Modular gamma imaging device
CN106388845A (en) Positron emission cerenkov-gamma bi-radiation imaging method and device
JP2001033556A (en) Radiation image device
US20040222379A1 (en) Event counter for an imaging device
Ericksen et al. MAHEM: A multiprocessor engine for fast contrast-limited adaptive histogram equalization
JP2000206251A (en) Random correction using artificial trigger pulse in gamma camera system
Jones et al. Advanced hardware architecture for on-line data acquisition in clinical 3-D PET: smart DRAM PCI Card for 14 M event/sec histogramming across terabytes of DRAM
Hua Compton imaging system development and performance assessment
Watabe et al. Performance of list mode data acquisition with ECAT EXACT HR and ECAT EXACT HR+ positron emission scanners
Conti et al. A transputer-based list mode parallel system for digital radiography with 2D silicon detectors
Langner et al. Optimized list-mode acquisition and data processing procedures for ACS2 based PET systems

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20061211

AK Designated contracting states

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU MC NL PL PT RO SE SI SK TR

AX Request for extension of the european patent

Extension state: AL BA HR LV MK YU

RBV Designated contracting states (corrected)

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU MC NL PL PT RO SE SI SK TR

PUAK Availability of information related to the publication of the international search report

Free format text: ORIGINAL CODE: 0009015

DAX Request for extension of the european patent (deleted)
A4 Supplementary search report drawn up and despatched

Effective date: 20101215

RIC1 Information provided on ipc code assigned before grant

Ipc: G06T 1/20 20060101ALI20101209BHEP

Ipc: G01T 1/164 20060101AFI20051207BHEP

17Q First examination report despatched

Effective date: 20120711

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20131203