SiPM Sensor Chip for PET Parallax Error Reduction
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Solution Overview
Problem
Current positron emission tomography (PET) detectors face challenges with parallax errors due to limited crystal thickness and sensitivity, especially in small animal and MRI-compatible scanners, where the DOI problem and sensitivity loss occur due to pixilated scintillation crystal arrays and SiPM-based technologies.
Innovation Solution
A sensor chip design that attaches SiPM microcells to one side of scintillation crystals, utilizing a grid of pixels with current dividers and coding resistors to enhance light distribution analysis, allowing for longer crystal dimensions and reduced parallax errors, while maintaining high spatial resolution and MRI compatibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixelated scintillation crystal arrays are used to improve spatial resolution, then measurement precision is improved, but sensitivity is reduced due to increased adhesive and reflective film thickness relative to crystal size
Solution Approach 1:
The sensor chip is segmented into multiple independently readable regions (first region and second region), allowing separate readout of light signals from different crystal pixel columns. This segmentation enables position-sensitive detection without requiring proportional increases in readout channel complexity, maintaining sensitivity while achieving high spatial resolution through selective region reading.
Solution Approach 2:
The sensor chip serves multiple functions: it detects light intensity for energy measurement, determines position through region-specific readout, and enables DOI determination through light distribution analysis. This multi-functionality is achieved by integrating position-sensitive photodiode arrays with readout circuitry that can selectively address different spatial regions, eliminating the need for separate positioning systems.
2Volume of moving object
If SiPM microcells are concentrated on a small area to maintain detector compactness, then device volume is reduced, but saturation effects increase reducing measurement precision
Solution Approach 1:
The sensor chip extends in the z-direction (depth) with multiple layers of photodiodes at different positions. This dimensional extension allows light to be detected at multiple depths within the crystal, increasing the effective detection volume without increasing the lateral footprint. The multi-depth readout capability reduces saturation effects by distributing light detection across multiple spatial zones.
Solution Approach 2:
Multiple sensor regions are nested within a compact chip structure, with first and second regions containing photodiodes at different positions and orientations. This nested arrangement maximizes the detection volume within a small footprint, allowing comprehensive light distribution analysis while maintaining detector compactness for integration in MRI-compatible PET scanners.
3Measurement precision
If current dividers and coding resistors are added to each pixel to enable position-sensitive readout, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The readout circuitry for multiple sensor regions is merged into a unified evaluation system that processes signals from both first and second regions through common signal processing pathways. This merging reduces the overall complexity by sharing amplification, filtering, and digitization resources across all sensor regions, rather than implementing completely independent readout chains for each region.
Solution Approach 2:
The sensor chip structure itself provides position encoding through the spatial arrangement of photodiodes and their connection to specific readout channels. The physical geometry of the chip and the light distribution patterns across regions enable self-determination of interaction position without requiring external positioning systems or complex additional circuitry beyond the basic photodiode-array structure.
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 design significantly reduces parallax errors, increases sensitivity and resolution, and allows for more precise DOI determination, enhancing the granularity of light distribution analysis, thereby improving PET scanner accuracy and reducing costs.
Implementation Method 1
A sensor chip design that attaches SiPM microcells to one side of scintillation crystals
Implementation Method 2
positron emission tomography (PET) detectors are used to detect β+
Implementation Method 3
utilizing a grid of pixels with current dividers and coding resistors to enhance light distribution analysis
Data Source
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AI summary
The invention relates to an SiPM sensor chip in which pixels consisting of microcells with at least one photodiode, at least one quench resistor, and a current divider are arranged in a raster. The positions of the pixels are determined using a linear code, and a summing network is integrated which taps voltages from the outputs of the current divider for the directions x and y, said voltages being supplied to an operation amplifier with an output channel via a common line NS,v,m or NS,h,n. By using the sensor chip according to the invention, the interaction depth problem can be minimized or completely solved, in particular for PET.