Dual-Energy CT X-Ray Source with Dual Cathode Gridding
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Solution Overview
Problem
Conventional CT imaging systems face challenges in acquiring imaging data at multiple energy ranges efficiently, particularly due to mis-registration issues from patient motion and insufficient photon-counting rates, which hinder detailed imaging and material characterization.
Innovation Solution
A dual-energy CT system with a rotatable gantry and x-ray source configuration that includes two cathodes and gridding electrodes, allowing for rapid switching between energy levels by applying different voltage potentials and gridding voltages to block electron emission, enabling simultaneous acquisition of dual energy imaging data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two scans are acquired back-to-back sequentially at different kVp operating levels, then energy sensitive measurements are obtained, but mis-registration between datasets occurs due to patient motion
Solution Approach 1:
The system performs periodic switching between first and second kVp operating levels during a single gantry rotation, acquiring projection data at alternating views. This periodic alternation allows both energy spectra to be captured within the same rotational cycle, eliminating mis-registration issues caused by patient motion between separate scans.
Solution Approach 2:
The x-ray tube operates dynamically by rapidly switching between different kVp levels (e.g., 80 kVp and 140 kVp) during continuous rotation. High frequency generators enable this dynamic kVp switching on alternating views, allowing the system to adapt the energy spectrum in real-time while maintaining consistent geometric alignment.
2Adaptability or versatility
If conventional CT systems acquire data at multiple energy ranges using sequential scans, then material decomposition is enabled, but the photon-counting rate is insufficient for detailed imaging
Solution Approach 1:
The system maintains continuous x-ray emission during the entire gantry rotation without interruption, switching between energy levels on alternating views rather than pausing for separate scans. This continuous operation maximizes the photon-counting rate while still acquiring data at multiple energy ranges for material decomposition.
3Use of energy by moving object
If separate scans are performed several seconds apart, then different energy spectra are acquired, but image artifacts increase due to patient motion
Solution Approach 1:
The system implements periodic alternation between first and second kVp operating levels during continuous gantry rotation, acquiring projection data at alternating views. This ensures both energy spectra are captured within the same rotational cycle, eliminating mis-registration artifacts caused by patient motion between separate scans.
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 enhances anatomical detail and tissue characterization, reduces image artifacts, and improves contrast for medical and baggage scanning applications by enabling fast and accurate energy-sensitive data acquisition.
Implementation Method 1
an x-ray source emits a fan-shaped or cone-shaped beam toward a subject or object
Implementation Method 2
a scintillator for converting x-rays to light energy adjacent the collimator
Implementation Method 3
photodiodes for receiving the light energy from the adjacent scintillator and producing electrical signals therefrom
Implementation Method 4
apply a gridding voltage to the first gridding electrode to block emission of the first beam of electrons toward the target
Data Source
AI summary
A CT system includes a rotatable gantry having an opening for receiving an object to be scanned and an x-ray source coupled to the gantry and configured to project x-rays through the opening. The x-ray source includes a target, a first cathode configured to emit a first beam of electrons toward the target, a first gridding electrode coupled to the first cathode, a second cathode configured to emit a second beam of electrons toward the target, and a second gridding electrode coupled to the second cathode. The system includes a generator configured to energize the first cathode to a first kVp and to energize the second cathode to a second kVp, and a detector attached to the gantry and positioned to receive x-rays that pass through the opening. The system also includes a controller configured to apply a gridding voltage to the first gridding electrode to block emission of the first beam of electrons toward the target, apply the gridding voltage to the second gridding electrode to block emission of the second beam of electrons toward the target, and acquire dual energy imaging data from the detector.