FPGA Edge Sensitivity Correction in PET Detector Blocks
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Solution Overview
Problem
PET scanners experience reduced sensitivity at the edges of detector blocks due to Compton scattering, where scattered gamma photons deposit energy in adjacent pixels, leading to lost events and inefficient energy detection.
Innovation Solution
Implementing a Field Programmable Gated Array (FPGA) on an Event Process Module (EPM) board to sum energy from adjacent detector blocks, correcting signals to compensate for lost energy and enhance edge crystal sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If detector blocks are arranged adjacently to form a radiation detector ring, then the detection coverage and field of view are improved, but sensitivity at the edges of detector blocks deteriorates due to Compton scattering
Solution Approach 1:
The patent combines signals from adjacent detector blocks by identifying and summing energy deposits that result from Compton scattering events. When a gamma photon scatters in one detector block and deposits energy in an adjacent block, the system merges these partial energy measurements into a single corrected event, thereby recovering sensitivity at edge regions while preserving the benefits of adjacent detector arrangement.
2Ease of manufacture
If photosensors are arranged in a matrix with fewer sensors than scintillation crystals, then manufacturing cost is reduced, but measurement precision of scintillation event localization deteriorates
Solution Approach 1:
The patent introduces an intermediary signal processing step that uses information from adjacent detector blocks to compensate for the reduced spatial sampling provided by fewer photosensors. By incorporating energy deposition patterns from neighboring blocks, the system reconstructs scintillation event locations with precision that approaches that of fully coupled systems while maintaining the cost benefits of reduced photosensor counts.
3Device complexity
If energy from Compton scattered photons is not corrected, then processing complexity is reduced, but loss of information about total photon energy increases
Solution Approach 1:
The patent applies preliminary action by proactively identifying Compton scattering events and correcting for energy loss before final image reconstruction. The system preemptively sums energy deposits across adjacent detector blocks and applies correction factors to recover the total photon energy, preventing information loss from occurring in the first place rather than attempting to recover it later in the processing chain.
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
Increases edge crystal sensitivity by approximately 10% for singles detection and 21% for coincidence detection between edge pixels, improving overall system sensitivity and energy qualification ratios.
Implementation Method 1
These are detected when they reach one of a plurality of scintillation crystals in the scanning device, creating a burst of light detected by an array of photosensors.
Implementation Method 2
creating a burst of light detected by an array of photosensors
Implementation Method 3
Compton scatter, which can occur when a photon collides with an electron, thereby transferring energy to the electron. The collision can cause the photon to deviate from its original path and cause a loss of energy.
Data Source
AI summary
An apparatus and method to increase the sensitivity at the edge of radiation detector blocks is disclosed herein. Reduced sensitivity can result from photons entering a first detector block, escaping, and scattering into an adjacent detector, thereby depositing energy into two detectors blocks. Energy lost into adjacent detector blocks can be compensated with energy detected in the adjacent detector block. This can be done, for example, by processing channels from multiple detector blocks with one Field Programmable Gated Array (FPGA) on one Event Process Module (EPM) board. This can enable summing energy of one detector block with energy from an adjacent detector block when the initial interaction occurs at the edge of the first detector block. This can result in a better estimate of the amount of energy associated with the initial photon being detected.