Pulsed X-Ray Imaging With Time-Gated Scatter Rejection
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Solution Overview
Problem
Current X-ray and CT imaging technologies face challenges in achieving high contrast-to-noise ratio (CNR) while minimizing radiation dose, particularly in pediatric and bariatric patients, due to the dominance of Compton scattering at higher X-ray energies, which increases noise and requires higher doses to compensate.
Innovation Solution
Implementing a pulsed X-ray source coupled with a time-sensitive detector to differentiate and reject scattered photons, allowing for the detection of ballistic photons and significantly reducing radiation exposure by optimizing the timing resolution of the imaging system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high energy X-ray photons are used to penetrate thick tissues, then penetration capability is improved, but Compton scattering increases causing higher noise and lower CNR
Solution Approach 1:
The patent employs pulsed X-ray emission instead of continuous emission, creating periodic action where X-rays are emitted in short bursts. This allows the detector to integrate signals only during pulse windows, separating ballistic photons from scattered photons temporally. The periodic pulsing enables time-gated detection that rejects Compton scattering noise while maintaining penetration capability through high energy photons.
Solution Approach 2:
The patent replaces traditional energy-based discrimination methods with time-based discrimination. Instead of using mechanical or electronic filters to block scattered photons, the system uses temporal information - detecting when photons arrive relative to the pulse timing. This substitution of mechanical filtering with temporal gating effectively reduces Compton scattering noise while preserving the benefits of high energy X-ray penetration.
2Measurement precision
If continuous X-ray imaging is used to maintain adequate photon statistics, then image quality is maintained, but radiation dose to patient increases
Solution Approach 1:
By using pulsed X-ray emission rather than continuous emission, the system concentrates the radiation dose into brief intervals. The detector integrates photons during these pulses, achieving adequate photon statistics for image quality while the overall integrated dose over time is significantly reduced. The periodic nature allows for dose reduction while maintaining measurement precision through optimized integration windows.
Solution Approach 2:
The patent maintains continuous useful action by continuously integrating photon signals during the pulsed emission periods. The detector operates continuously to capture ballistic photons during each pulse, ensuring no loss of useful signal while the pulsed nature of emission limits the total radiation exposure. This continuity of detection combined with pulsed emission achieves both image quality and dose reduction.
3Object-generated harmful factors
If time-gated detection is implemented to reject scattered photons, then CNR is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex spatial filtering mechanisms with simpler temporal gating. Instead of using complex mechanical collimators or energy-discriminating detectors, the system uses time-based rejection where the detector simply integrates signals within specific time windows relative to pulse emission. This substitution dramatically reduces system complexity while achieving effective scattered photon rejection and improved CNR.
Solution Approach 2:
The patent changes the detection parameter from spatial or energy discrimination to temporal discrimination. By measuring photon arrival time relative to pulse emission and using this temporal parameter for gating, the system achieves scattered photon rejection without requiring complex spatial filtering or energy discrimination hardware. This parameter change simplifies the overall system architecture while maintaining effective noise rejection.
4Object-affected harmful factors
If pulsed X-ray source with time-sensitive detector is used to reduce radiation dose, then patient safety is improved, but measurement precision may be compromised
Solution Approach 1:
The patent ensures continuous useful action during pulse intervals by maintaining continuous detector integration throughout the pulsed emission periods. This continuous detection during pulses maximizes photon capture efficiency, ensuring adequate photon statistics are achieved even with reduced overall dose. The continuity of detection compensates for the reduced temporal duty cycle, maintaining measurement precision while enabling dose reduction through pulsed operation.
Solution Approach 2:
The periodic pulsed emission concentrates the radiation dose into efficient intervals where detection is actively integrated. By synchronizing the detection integration windows with the pulse periods, the system maximizes the utilization of each photon emitted, achieving adequate photon statistics with fewer total photons required. This periodic synchronization improves measurement precision efficiency while reducing overall radiation dose.
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 approach improves the CNR by at least doubling it for the same radiation dose and reduces the radiation delivered to patients by up to 60% compared to continuous X-ray imaging, effectively addressing the cup artefact issue in bariatric patients and enabling lower dose imaging for various applications.
Implementation Method 1
irradiating on one side a subject with X-rays produced by a source
Implementation Method 2
measuring a time of flight of the X-ray photons from the source to the detector
Implementation Method 3
The energy of the photons is thus chosen for the object to be imaged to make sure that the relative loss of photons through absorption can provide useful imaging data
Implementation Method 4
measuring a time of flight of the X-ray photons from the source to the detector with a time-sensitive detector
Data Source
AI summary
The X-ray imager combines a pulsed X-ray source with a time-sensitive X-ray detector to provide a measure of ballistic photons with a reduction of scattered photons. The imager can provide a comparable contrast-to-noise X-ray image using significantly less radiation exposure than conventional X-ray imagers, notably about half of the radiation.