Dosimetry Device with Dual Ionization Chambers
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Solution Overview
Problem
Conventional ionization chambers face limitations in measuring high-intensity particle beam currents due to significant recombination phenomena, leading to measurement errors and the inability to accurately determine dose rates, especially in advanced radiotherapy techniques where charge collection efficiency is not maximum.
Innovation Solution
A dosimetry device comprising at least two ionization chambers with different charge collection efficiency factors, utilizing an algorithm to calculate the dose rate based on measured output signals and a 'gain' factor that normalizes the ratio of theoretical values, independent of the beam current intensity, allowing for precise measurement of charge collection efficiency and dose rate even under conditions of significant recombination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional ionization chamber is used to measure high-intensity particle beam currents, then the measurement process is simple, but significant recombination phenomena occur leading to measurement errors and inability to accurately determine dose rates
Solution Approach 1:
The system divides the measurement function into multiple ionization chambers (at least two) with different charge collection efficiency factors. Each chamber operates at different saturation levels, allowing the system to segment the measurement range and select or combine results based on beam intensity, thereby maintaining accuracy across wide intensity ranges while avoiding the limitations of a single chamber.
Solution Approach 2:
The invention changes the parameter of charge collection efficiency factor between different ionization chambers. By using chambers with deliberately different efficiency factors (achieved through different gap thicknesses, electrode configurations, or gas compositions), the system can accurately measure across different beam intensity ranges, as each chamber's characteristics are optimized for specific intensity regimes.
2Productivity
If the beam current intensity increases, then the productivity of the dosimetry system improves, but recombination phenomena increase proportionally leading to current loss and measurement error
Solution Approach 1:
The system uses feedback by continuously monitoring the output signals from multiple ionization chambers and using an algorithm to determine which chamber (or combination of chambers) provides accurate measurements under current beam conditions. The algorithm adjusts the interpretation of measurements based on the observed signals, effectively providing feedback control to maintain accuracy across varying beam intensities.
Solution Approach 2:
Different ionization chambers are designed with different charge collection efficiency factors through varying physical parameters such as gap thickness, electrode area, or gas pressure. This parameter differentiation allows each chamber to respond differently to beam intensity changes, enabling the system to maintain measurement accuracy across the full range of beam intensities by selecting the appropriate chamber or combining results.
3Adaptability or versatility
If a single ionization chamber is used, then the device complexity is reduced, but the adaptability to measure across wide beam intensity ranges is limited
Solution Approach 1:
The measurement system is segmented into multiple ionization chambers, each optimized for specific intensity ranges. This segmentation allows the system to adapt to wide beam intensity ranges by selecting the appropriate chamber segment, while the modular nature of adding chambers keeps the increase in device complexity manageable and justified by the significant gain in versatility.
Solution Approach 2:
The system achieves multi-functionality by designing ionization chambers with different charge collection efficiency factors, allowing the same basic chamber type to serve multiple measurement purposes across different beam intensities. This universal approach enables a single dosimetry system to handle various radiotherapy techniques and beam conditions without requiring completely different measurement setups.
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
Enables accurate measurement of dose rates for particle beams across a wide range of intensities, including high-intensity beams, by accounting for variations in intrinsic and extrinsic parameters, thereby improving the precision and reliability of dosimetry in conditions where conventional chambers fail.
Implementation Method 1
When an ionizing beam passes through the ionization chamber, the gas between the electrodes is ionized and ion-electron pairs are created
Implementation Method 2
An electric field is generated by applying a potential difference between the two electrodes of the ionization chamber. The presence of an electric field makes it possible to separate these ion-electron pairs and cause them to drift across the electrodes
Implementation Method 3
In zone Z1, called the unsaturated regime zone, when the electric field between the two plates is non-existent, there is recombination of the ion-electron pairs
Data Source
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AI summary
The present invention relates to a dosimetry device for an energy particle beam from a source and including at least two ionization chambers, each of which includes a collector electrode and a polarization electrode, said electrodes in each ionization chamber being separated by a gap including a fluid, an energy beam from a single source passing through said ionization chambers, the device being characterized in that said ionization chambers have different charge collection efficiency factors. Said calculation algorithm for the dose rate deposited by said beam is based on the measurement of an output signal in each ionization chamber of the device and on a gain factor related to a first ionization chamber, said gain factor being theoretically predetermined on the basis of said intrinsic and/or extrinsic parameters of said ionization chambers.