TOF-PET Continuous Bed Motion Rebinning via DMA
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Solution Overview
Problem
Current Positron Emission Tomography (PET) data acquisition methods, particularly in time-of-flight (TOF) tomography, face challenges with continuous bed motion (CBM) data collection, as they require discontinuous 'step and shoot' scanning modes, which disrupt data acquisition and limit the ability to perform uninterrupted whole-body studies exceeding the physical field of view of the detector array.
Innovation Solution
A system incorporating a TOF-PET detector array with a stationary field of view and a patient bed drive mechanism, controlled by a processor, enables continuous bed motion, utilizing a direct memory access (DMA) rebinner card with a router Field Programmable Gate Array (FPGA) and memory chips configured with look-up tables to map coincidence event data into projection space data in real-time, supporting on-line time-of-flight mashing and multiple-slice rebinning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If step and shoot scanning mode is used, then data acquisition can be performed at stationary positions with adequate resolution, but the scanning process is discontinuous and time-consuming with rapid slewing movements between positions
Solution Approach 1:
The patent transitions from static step-and-shoot scanning to dynamic continuous bed motion scanning. The bed moves continuously through the detector array at a controlled speed while data acquisition occurs uninterrupted, eliminating the need for repeated stopping and rapid slewing movements between stationary positions. This dynamic approach maintains measurement precision through real-time position tracking and compensation while significantly reducing total scanning time.
Solution Approach 2:
The patent implements continuous data acquisition during uninterrupted bed motion. Unlike the discontinuous step-and-shoot mode where acquisition is paused during rapid bed movements, this system maintains continuous coincidence detection and data collection throughout the entire scanning process, with the bed moving smoothly through the field of view without stopping or rapid reversals.
2Productivity
If continuous bed motion is implemented, then scanning time is reduced and data acquisition is uninterrupted, but real-time mapping of line of response locations into projection space becomes computationally complex
Solution Approach 1:
The patent pre-calculates and stores lookup tables containing rebinning factors and mapping parameters before the scanning process begins. These pre-computed values account for the continuous bed motion trajectory and detector geometry, enabling real-time data processing during scanning without requiring complex on-the-fly calculations. The preliminary preparation of these reference tables simplifies the real-time mapping operation significantly.
Solution Approach 2:
The patent introduces a dedicated rebinner computer as an intermediary processing unit between the coincidence detection system and the final image reconstruction. This specialized component handles the complex real-time mapping of line of response locations into projection space using pre-computed rebinning factors, isolating the computational complexity from the main scanning control system and enabling efficient parallel processing of the continuous data stream.
3Device complexity
If traditional step and shoot mode is used, then data processing is simpler, but memory requirements increase due to separate reconstruction of multiple static acquisitions
Solution Approach 1:
The patent merges multiple partial acquisitions obtained during continuous bed motion into a single unified three-dimensional image through real-time rebinning and projection space mapping. Instead of separately reconstructing multiple static images and then combining them through voxel-summation, the system processes all coincidence events continuously and maps them directly into a unified projection dataset that reconstructs the entire elongated region in one operation, reducing the computational overhead and memory requirements for separate image storage and combination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution allows for uninterrupted data acquisition during continuous bed motion, enhancing image resolution and reducing memory requirements by enabling precise on-line mapping of line of response locations, resulting in improved three-dimensional image generation and efficient data processing.
Implementation Method 1
Time-of-flight positron emission tomography (TOF-PET) is based on the measurement of the difference between the detection times of the two gamma photons arising from the positron annihilation event. This measurement allows the annihilation event to be localized along the LOR with a adequate resolution.
Implementation Method 2
Measurement of the tissue concentration of a positron emitting radionuclide is based on coincidence detection of the two gamma photons arising from positron annihilation.
Implementation Method 3
Gamma photons produced by an annihilation event can be detected by a pair of oppositely disposed radiation detectors capable of producing a signal in response to the interaction of the gamma photons with a scintillation crystal.
Data Source
AI summary
A patient bed drive mechanism, under control of a processor, is capable of continuously moving a patient bed through the a TOF-PET detector array having a stationary field of view (FOV) for a distance in excess of the physical extent of an axis of the array FOV. A direct memory access (DMA) rebinner card is coupled to the detector array to receive therefrom a stream of TOF-PET coincidence event data during the extent of movement of the bed. Image projection data are generated in real time from the acquired stream of TOF-PET coincidence event data via the DMA card.