Large Aperture PET Scanner Stray Radiation Elimination
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Solution Overview
Problem
Current PET scanners lack the necessary large patient aperture and high sensitivity to effectively support radiation therapy planning and monitoring, leading to suboptimal imaging quality and prolonged scan times, with side shielding rings being essential but insufficient to mitigate stray radiation issues.
Innovation Solution
A PET imaging system with a detector ring having a patient aperture of at least 80 cm, omitting side shielding rings and utilizing high-speed radiation detectors with narrow coincidence and energy windows to compensate for increased noise, enabling oncological quality images without the need for side shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If side shielding rings are added to PET scanners to reduce stray radiation, then radiation protection is improved, but patient aperture is reduced
Solution Approach 1:
The patent removes the side shielding rings from the PET scanner design, extracting the harmful element (side shields that blocked patient access) while compensating through alternative means (narrow coincidence windows, energy windows, and high-sensitivity detectors) to maintain radiation protection without sacrificing patient aperture
Solution Approach 2:
The patent changes detection parameters by implementing narrow coincidence time windows and energy windows, which selectively filter stray radiation based on temporal and spectral characteristics rather than physical blocking, thereby maintaining large patient aperture while protecting against harmful radiation
2Measurement precision
If PET scanner aperture is increased to 80 cm for radiation therapy positioning, then positioning accuracy is improved, but stray radiation increases
Solution Approach 1:
The patent replaces mechanical/physical shielding (side shields) with electronic/digital filtering methods (narrow coincidence windows, energy windows) to distinguish and reject stray radiation events, enabling large aperture while maintaining radiation protection through parameter-based discrimination rather than physical barriers
3Measurement precision
If high-speed radiation detectors with narrow coincidence windows are used to reduce stray radiation effects, then image quality is improved, but detection sensitivity is reduced
Solution Approach 1:
The patent optimizes detection parameters by implementing narrow coincidence time windows and energy windows that selectively filter events based on their temporal and spectral characteristics, improving image quality by rejecting stray radiation while maintaining adequate detection sensitivity through parameter tuning rather than excessive filtering
Solution Approach 2:
The patent uses CT imaging as a complementary modality to compensate for potentially reduced PET sensitivity, creating a fused PET/CT imaging system where CT provides structural information that complements PET functional data, thereby maintaining overall diagnostic quality even if PET sensitivity is slightly reduced
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 configuration allows for the generation of high-quality PET images in radiation therapy positions, reducing scan time and improving image fidelity, while maintaining oncological standards without the need for side shielding, thus enhancing the integration with CT imaging for radiation therapy planning.
Implementation Method 1
Each emitted positron interacts with a nearby electron in an electron-positron annihilation event that emits two oppositely directed 511 keV gamma rays
Implementation Method 2
These gamma rays are detected substantially simultaneously by a radiation detector ring, thus defining a line-of-response along which the electron-positron annihilation event must (neglecting scattering) have occurred
Implementation Method 3
Anatomical data for the radiation therapy planning is acquired using computed tomography (CT) imaging which measures transmission of a tomographically rotating x-ray beam to enable reconstruction of a three-dimensional image of the internal patient anatomy
Data Source
AI summary
An imaging system comprises: a ring of positron emission tomography (PET) detectors; a PET housing at least partially surrounding the ring of PET detectors and defining a patient aperture of at least 80 cm; a coincidence detection processor or circuitry configured to identify substantially simultaneous 511 keV radiation detection events corresponding to electron-positron annihilation events; and a PET reconstruction processor configured to reconstruct into a PET image the identified substantially simultaneous 511 keV radiation detection events based on lines of response defined by the substantially simultaneous 511 keV radiation detection events. Radiation planning utilizing such an imaging system comprises: acquiring PET imaging data for a human subject arranged in a radiation therapy position requiring a patient aperture of at least about 80 cm; reconstructing said imaging data into a PET image encompassing an anatomical region to undergo radiation therapy; and generating a radiation therapy plan based on at least the PET image.