Background technology
Positron emission tomography (Positron Emission Tomography, PET) is a kind of nuclear medicine technology.It can be on molecular level to the function information of people's in-vivo tissue, as physiology, pathological change etc. carry out in real time, noinvasive, dynamic imaging in vivo, have irreplaceable effect at earlier detection, diagnosis, classification, therapeutic scheme formulation, therapeutic evaluation and the aspects such as tracking, recurrence detection such as cancer.
The ultimate principle of PET imaging is: pass through radiosiotope (such as F to the human injection
18Deng) medicine of labelling, these medicines arrive the Organ and tissue of inside of human body.Radiosiotope is because decay discharges beta-particle.After burying in oblivion, beta-particle produces the γ photon of a pair of opposite direction in human body.This a pair of γ photon passes and is projected in respectively detector array after the tissue and lists.Two detector modules that detector array lists detect this two γ photons simultaneously, are called to meet (coincidence) detection.How much lines between two detectors have reflected the direction that the γ photon passes human body, are called line of response (Line of Response, LOR).After all line of response were carried out data acquisition, by Computer Three-dimensional reproduction technology, space, concentration and the time that can obtain human body inside radiation isotope medicine distributed, and can adopt the form of image to be shown visually and present.Also can find out from above-mentioned image-forming principle, the PET imaging the major function unit comprise detector, electronic system and computerized algorithm and three parts of software.
Traditional PET imaging device is a very complicated system.Electronic system wherein need to be finished the functions such as the reading of detector signal, signal processing, coincidence detection and data acquisition.Traditional way is to adopt the parts of a plurality of separation to realize these functions, and bulky, the connection between the parts is complicated, detects and debug loaded down with trivial details, and not only cost is higher, and the entire system poor reliability.Because the component function of these separation is single fixing, adjustment and the upgradability of systemic-function are poor, difficult renewal and the development of satisfying modern technologies and clinical practice.
These factors have all caused traditional PET imaging device complicated structure, and design and production cost are high, and the production cycle is long.
For simplified system, the inventor proposes a kind of totally digitilized blood processor of positron emission tomography electronic system of total digitalization processing, owing to adopt the mode of total digitalization to realize PET signal detection, processing and data acquisition etc., level of integrated system is high, powerful, the processing real-time is good, and is stable and reliable for performance, and the systemic-function adjustment and escalation is convenient.
The electronic system that core component is made table data information for the γ photo-event position that will capture and time signal in the totally digitilized blood processor of the positron emission tomography electronic system that total digitalization is processed.
Summary of the invention
The object of the invention is exactly the totally digitilized electronic system that research is a kind of and the totally digitilized blood processor of the totally digitilized positron emission tomography electronic system of processing is supporting.
The present invention includes identical some primitive event detection modules, system event sorter and the system event transmitting device of detector number of arranging with annular array type, described each primitive event checkout gear is connected on the corresponding detector by A/D converter respectively; The outfan of described each primitive event checkout gear is connected on the input of system event transmitting device through the system event sorter; Power supply, the clock control device that provides for described primitive event checkout gear, system event sorter and system event transmitting device also is provided described totally digitilized electronic system.
The high-speed a/d device that position and the time simulation signal of the γ photo-event that output captures from each detector on the detector rings, these analog passband signals are crossed a plurality of passages carries out synchronous analog digital conversion and forms digital signal.These digital signals form corresponding list mode data output by the system event transmission link after processing through the total digitalization that primitive event detects, system event is classified two links again.
The present invention can satisfy the needs of the totally digitilized blood processor of the positron emission tomography electronic system that total digitalization processes, can with
A pair of γ photon passes two detectors that are detected after the tissue on the device ring and catches simultaneously and process accordingly and coincidence detection after formed event receives, formation meets event and corresponding line of response information, again all line of response information is sent to image workstation with the form of list mode data, in order to carry out date processing and three-dimensional reconstruction.
Each primitive event detection module of the present invention has the arrival of utilization Time Triggered and energy discrimination judges whether γ photo-event position and time signal that each detector is caught belong to validity event, if belong to validity event, then this γ photo-event position and time signal are latched the device of rear output according to the form of original γ photo-event word.
Primitive event detection module of the present invention comprises the position signalling base line restorer, position signalling is piled up restorer, the position signalling digital integrator, the time signal base line restorer, time signal is piled up restorer, the time of advent detector, the event time computer, X position signalling base line restorer, the X position signalling is piled up restorer, X position signalling digital integrator, Y position signalling base line restorer, the Y position signalling is piled up restorer, Y position signalling digital integrator, the event energy calculator, the event location computer, the crystal look-up table, energy discrimination device and primitive event word splicer;
Described position signalling base line restorer, time signal base line restorer, X position signalling base line restorer and Y position signalling base line restorer are connected on the corresponding detector by A/D converter respectively;
Described position signalling base line restorer is piled up restorer by described position signalling and is connected with the position signalling digital integrator;
Described X position signalling base line restorer is piled up restorer by the X position signalling and is connected with X position signalling digital integrator;
Described Y position signalling base line restorer is piled up restorer by the Y position signalling and is connected with Y position signalling digital integrator;
Described time signal base line restorer by time signal pile up restorer with the time of advent detector be connected;
Described time of advent detector signal output part be connected to event can the time computer and position signalling digital integrator, X position signalling digital integrator, Y position signalling digital integrator;
The input of computer is connected on the described primitive event word splicer during described event energy;
The signal output part of described crystal look-up table, position signalling digital integrator, X position signalling digital integrator, Y position signalling digital integrator is connected on the described primitive event word splicer;
The signal output part of described position signalling digital integrator also is connected on described energy discrimination device and the primitive event word splicer by described event energy calculator;
The signal output part of described energy discrimination device is connected on the described primitive event word splicer.
Described system event sorter comprises that a single event engine apparatus, one meet event engine device, a random event engine apparatus and a sequential event engine device;
Described single event engine apparatus has the output of each primitive event detection module of scanning, and to the device that each single event separates and processes, also has in the information output that will separate and process and the event buffer that temporarily leaves correspondence in;
The described event engine device that meets has the output that scans each primitive event detection module, and to any two devices that event is carried out coincidence detection and processing, also has in the information output that will separate and process and the event buffer that temporarily leaves correspondence in;
Described random event engine apparatus has the output of each primitive event detection module of scanning, and to the device that any two events are carried out the random coincidence detection and processed, also have in the information output that will separate and process and the event buffer that temporarily leaves correspondence in;
Described sequential event engine device has the device for generation of time scaling information that can the insertion system data flow, also has the information output that will separate and process and temporarily leaves in the corresponding event buffer.
System event transmitting device of the present invention has the information of each event buffer of scanning, and forms the device of list mode data information output.
The specific embodiment
As shown in Figure 1, the present invention's total digitalization electronic system comprises identical some primitive event detection modules, system event sorter and the system event transmitting device of detector number of arranging with annular array type, and each primitive event checkout gear is connected on the corresponding detector by A/D converter respectively.The outfan of each primitive event checkout gear is connected on the input of system event transmitting device through the system event sorter.
Power supply, the clock control device that provides for described primitive event checkout gear, system event sorter and system event transmitting device also is provided the total digitalization electronic system.
Position and the time simulation signal of the γ photo-event that output captures from each detector on the detector rings (detector 1 shown in Fig. 2, detector 2, to detector N).The high-speed a/d device that these analog passband signals are crossed a plurality of passages carries out synchronous analog digital conversion formation digital signal.These digital signals form corresponding list mode data output by the system event transmission link after processing through the total digitalization that primitive event detects, system event is classified two links again.
The primitive event detection mainly comprises the some primitive event detection modules corresponding with the system detector number.Each primitive event detection module to from corresponding detector, process through event location and time signal behind the digitized, according to certain system's setting, utilize arrival Time Triggered and energy discrimination to judge whether the event that detector is caught belongs to validity event, if belong to validity event, then this event is latched rear output according to the form of primitive event word.
System event classification link mainly comprises a single event engine, one and meets event engine, a random event engine and a sequential event engine.The single event engine scans the output of each primitive event detection module, and the single event in the system is separated and processes.Meet the output that event engine scans each primitive event detection module, any two events are carried out coincidence detection and processing.The random event engine scans the output of each primitive event detection module, any two events is carried out random coincidence detect and process.The sequential event engine is for generation of time scaling information that can the insertion system data flow.The output of these engines is all in accordance with the form of certain system event word, and temporarily leaves in the corresponding event buffer memory.
The system event transmission link mainly comprises a system event transmission mechanism.The system event transmission mechanism scans each event buffer memory according to certain mechanism, and forms final list mode data output.
System power supply, clock and control module provide power supply and synchronous work clock for each functional module in the totally digitilized electronic system, reception is from the co-ordination of the control command of image workstation and corresponding each functional module of control, and collects the status information of each functional module and feed back to image workstation.
As shown in Figure 2, the primitive event detection module comprises the position signalling base line restorer, position signalling is piled up restorer, the position signalling digital integrator, the time signal base line restorer, time signal is piled up restorer, the time of advent detector, the event time computer, X position signalling base line restorer, the X position signalling is piled up restorer, X position signalling digital integrator, Y position signalling base line restorer, the Y position signalling is piled up restorer, Y position signalling digital integrator, the event energy calculator, the event location computer, the crystal look-up table, energy discrimination device and primitive event word splicer.
Position signalling base line restorer, time signal base line restorer, X position signalling base line restorer and Y position signalling base line restorer are connected on the corresponding detector by A/D converter respectively.
The position signalling base line restorer is piled up restorer by described position signalling and is connected with the position signalling digital integrator.
X position signalling base line restorer is piled up restorer by the X position signalling and is connected with X position signalling digital integrator.
Y position signalling base line restorer is piled up restorer by the Y position signalling and is connected with Y position signalling digital integrator.
The time signal base line restorer by time signal pile up restorer with the time of advent detector be connected.
The time of advent detector signal output part be connected to event can the time computer and position signalling digital integrator, X position signalling digital integrator, Y position signalling digital integrator.
The input of computer is connected on the described primitive event word splicer during event energy.
The signal output part of crystal look-up table, position signalling digital integrator, X position signalling digital integrator, Y position signalling digital integrator is connected on the described primitive event word splicer.
The signal output part of position signalling digital integrator also is connected on described energy discrimination device and the primitive event word splicer by described event energy calculator.
The signal output part of energy discrimination device is connected on the described primitive event word splicer.
, move and the impact of pile-up events with the erasure signal baseline at first by base line restorer with pile up restorer from the position of detector module and time signal.As a kind of implementation, some somes signals before base line restorer can arrive event average, and as the reference value of baseline, and input signal are deducted the purpose that corresponding reference value reaches baseline restorer.As a kind of implementation, pile up restorer and can utilize the signal waveform template of calculated in advance storage that input signal is carried out matching treatment, and then the event after will piling up is separated and reduction.
The time of advent, detector extracted the time of advent of event from time signal.As a kind of implementation, the time of advent, detector can adopt the method that rising edge is differentiated, perhaps constant component is differentiated the method for (Constant Fractional Discriminator, CFD).
The event time computer is to giving a time value take system clock as unit the time of advent of event.As a kind of implementation, the event time computer can be that an enumerator adds one and latchs output unit.
Digital integrator carries out Integral Processing to position signalling.The essence of integration is the accumulation of quantities of charge.As a kind of implementation, digital integrator can adopt accumulator that the value of the digital signal in a period of time scope is added up.The starting point of the time of integration can be the aforesaid event time of advent, and terminal point can be determined by integration time constant.
The event energy calculator is extracted the energy information of event from the integrated value of position and signal.As a kind of implementation, the event energy calculator can be a look-up table, and the content of table is integration numerical value and the relation of the demarcation between the actual event energy of position and signal.
The event location computer from position signalling the calculating event in the two-dimensional coordinate value of detector surface.As a kind of implementation, the event location computer can calculate x position and position and ratio as the X position coordinates of event, calculate y position and position and ratio as the Y position coordinates of event.Because detector often adopts the form of crystal array, the surperficial two-dimensional coordinate value that therefore calculates can correspond to corresponding crystal unit by the crystal look-up table, and as final event location output.
The energy discrimination device is by the event the judgement of event energy being determined detector and captured good event whether.As a kind of implementation, the energy discrimination device can be a comparator, and the upper and lower bound of comparator has represented respectively the set energy window of system.
Latch output after the format permutation of relevant information according to the primitive event word of agreement of primitive event word splicer with the event by energy discrimination.
Single event engine of the present invention separates the single event in the system and processes.Because each primitive event detector detects the single event that the primitive event of output all belongs to system, therefore the single event engine can scan each primitive event detection module, when it has primitive event word when output, read the primitive event word, and the form that is rearranged for the system event word gets final product.
Meeting event engine detects and processes the event that meets in the system.The basic skills of coincidence detection is to judge whether be positioned at two times of advent in the primitive event word to meet time window, if so, then is judged as one and meets event.Fig. 3 has provided the realization example of a coincidence detection.
In real system, because the impact of scattering may cause vacation to meet event.The method for removing that vacation is met event can adopt the form of exclusive comparison, if namely in the window the two or more events that meets occuring at the same time, think that then vacation meets event, otherwise then think the true coincidence event.Meeting event engine exports after to the format combination relevant information of true coincidence event according to the system event word that detects.
Random event engine of the present invention detects and processes the random event in the system.With the basic skills of machine testing be a primitive event is postponed after and another primitive event carry out coincidence detection, if so, then be judged as a random event.Fig. 4 has provided the realization example that a random event detects, and the random event engine is exported after to the format combination relevant information of random event according to the system event word that detects.
Sequential event engine of the present invention produce can the insertion system data flow time scaling information.In the data acquisition of dynamic imaging pattern, time scaling information can be demarcated the moment of the data that collect, thus for the date processing of follow-up time-based sheet and three-dimensional reconstruction provide may.As a kind of implementation, the sequential event engine can be the output of latching of one-level or some grades of enumerators.The sequential event engine is to the time scaling data that the produce formatted output according to the system event word.
The system event transmission mechanism scans each system event buffer memory according to certain mechanism, and forms final list mode data output.Fig. 5 has provided the realization example of a system event transmission mechanism.It mainly selects logic to form by a variable connector and a scanning.Scanning selects logic that each system event buffer memory is carried out poll scanning, if having system event in the event buffer memory, variable connector then reads a system event and output.The mode of poll scanning can be disposed by a system event scan templates.By this template, can select to scan or ignore certain type system event.
Totally digitilized electronic system proposed by the invention can be adjusted duty and running parameter online under the control of image workstation.System's control and control command and the parameter of query interface reception from image workstation.Control command can include but not limited to: system works pattern, image data stream mode, collection beginning, collection suspend, gather end etc.Parameter can include but not limited to: acquisition time, energy discrimination window, meet time window etc.The total digitalization electronic system also can be to image workstation transmitting system status information, in addition, in gatherer process, also can send in real time the real-time status information of collection, include but not limited to: the single event counting rate, meet event count rate, random event counting rate, validity event number, gather the persistent period etc.
The system works pattern of totally digitilized electronic system proposed by the invention can include but not limited to general source figure (flood image) pattern and meet pattern.The realization of system works pattern can realize by the system event scan templates described in 8.Under general source figure (flood image) pattern, the system event scan templates will be configured to only scanning system single event buffer memory, and ignore every other system event buffer memory.Meeting under the pattern, the system event scan templates will be configured to ignore system's single event buffer memory.Meet the image data stream mode that system can also be set under the pattern, including but not limited to static data drainage pattern and Dynamic Data Acquiring pattern.Under the static data drainage pattern, the system event scan templates be configured to ignore system's single event buffer memory and system sequence event buffer memory.Under the Dynamic Data Acquiring pattern, being configured to of system event scan templates ignored system's single event buffer memory, but comprises system sequence event buffer memory.
Totally digitilized electronic system proposed by the invention all adopts digital circuit except A/D converter spare.Its specific implementation platform is including but not limited to one or more pieces special ICs (Application Specific Integrated Circuit, ASIC), one or more pieces field programmable logic array (Field Programmable Gate Array, FPGA), common treatment devices such as one or more pieces digital signal processors (Digital Signal Processor, DSP) and one or more pieces single-chip microcomputers, microprocessor etc.Its specific implementation can be the interconnection between one or more circuit board and the circuit board.