Semiconductor Photon Counting Detectors for CBCT Imaging
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Solution Overview
Problem
Conventional CBCT systems face challenges with lateral patient truncation, leading to artifacts and quantitative bias in dose calculation and treatment planning, due to insufficient dynamic range and poor quantum efficiency of flat-panel detectors, which limits their ability to image medically relevant features with low contrast and requires alternative imaging technologies.
Innovation Solution
A treatment apparatus utilizing a rotatable gantry system with a radiation detector that includes a semiconductor material, such as cadmium zinc telluride (CdZnTe), silicon drift detector (SDD), or cadmium telluride (CdTe), which emits pulsed x-ray radiation and modifies the bias voltage between emissions to dissipate transient effects like polarization and charge trapping, allowing for energy-resolved photon counting and improved image resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If flat-panel detectors are used in CBCT systems, then the system can perform basic imaging, but the dynamic range is insufficient and quantum efficiency is poor, leading to artifacts and quantitative bias
Solution Approach 1:
The patent changes the fundamental detection parameter from scintillation-based detection to direct semiconductor detection. This parameter change enables the detector to achieve sufficient dynamic range and quantum efficiency, directly resolving the issue of insufficient measurement precision and harmful artifacts in CBCT imaging
Solution Approach 2:
The patent substitutes the scintillation mechanism with a direct semiconductor detection mechanism. By replacing the scintillator material with semiconductor materials like CdZnTe, the system achieves direct x-ray to electrical signal conversion, eliminating the intermediate conversion step that limited dynamic range and quantum efficiency in flat-panel detectors
2Productivity
If continuous x-ray radiation is applied, then imaging can be performed, but transient effects like polarization and charge trapping accumulate, degrading detector performance
Solution Approach 1:
The patent implements periodic pulsed x-ray radiation instead of continuous radiation. By delivering x-rays in periodic pulses with appropriate duty cycles, the system maintains high imaging speed while allowing the semiconductor detector to recover from transient effects between pulses, thus preserving detector performance stability
Solution Approach 2:
The patent applies preliminary resetting actions to the detector between x-ray pulses. By resetting the detector state during the inter-pulse interval, the system prevents accumulation of transient effects before the next radiation pulse arrives, ensuring consistent detector response throughout the imaging sequence
3Measurement precision
If pulsed x-ray radiation is used, then transient effects can dissipate, but the imaging time per fraction increases
Solution Approach 1:
The patent dynamically adjusts the pulsed x-ray radiation parameters including pulse width, pulse frequency, and duty cycle. By optimizing these dynamic parameters, the system achieves the minimum necessary pulse duration for accurate energy-resolved photon counting while minimizing total imaging time, thus balancing measurement precision with time efficiency
4Reliability
If higher energy x-rays are used for therapy, then treatment effectiveness improves, but the ability to image medically relevant features with low contrast decreases
Solution Approach 1:
The patent segments the x-ray spectrum into multiple energy bins using energy-resolved photon counting. By detecting photons in different energy ranges separately, the system can analyze both high-energy photons (for treatment planning) and low-energy photons (for contrast imaging), thus achieving both treatment effectiveness and contrast resolution simultaneously
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
The solution enables high-quality, energy-resolved tomographic data collection at rapid frame rates, reducing artifacts and bias, and improving the accuracy of dose calculation and treatment planning by mitigating transient effects in semiconductor-based detectors.
Implementation Method 1
A radiation detector subject to a transient effect caused by at least one of polarization and charge trapping... The radiation detector includes a semiconductor material... energy-resolved photon counting
Implementation Method 2
The radiation detector is subject to a transient effect caused by at least one of polarization and charge trapping... modifies the bias voltage between emissions to dissipate transient effects like polarization
Implementation Method 3
The radiation detector is subject to a transient effect caused by at least one of polarization and charge trapping... modifies the bias voltage between emissions to dissipate transient effects like polarization and charge trapping
Data Source
Figure 1A
Figure 1B~1C
Figure 1D
AI summary
Disclosed herein is a treatment apparatus. The treatment apparatus includes a rotatable gantry system positioned at least partially around a patient support and a first source of radiation coupled to the rotatable gantry system. The first source of radiation is configured to emit imaging x-ray radiation after pausing for a time interval between periodic emissions. The apparatus further includes a radiation detector configured to receive x-ray radiation from the first radiation source and generate tomographic data from the received radiation. The radiation detector is subject to a transient effect caused by at least one of polarization and charge trapping. The time interval is sufficiently long for the transient effect to substantially dissipate.