Secondary-Electron Dose Rate Monitor for FLASH Radiotherapy
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Solution Overview
Problem
Conventional dosage monitoring devices are inaccurate for high radiation intensity therapies like FLASH radiotherapy due to electron/ion recombination, which disrupts the linear correlation between measured current and radiation dose rate.
Innovation Solution
A radiotherapy dose rate monitor system with a novel configuration of electrodes and gas chamber that minimizes electron/ion collection by using lower voltages and electric fields, relying on secondary electron emission for current measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ionization chamber dosage monitoring devices are used to measure radiation dose rate, then the measurement is accurate for conventional radiotherapy dose rates (up to 0.4 Gy/s), but the measurement becomes inaccurate for high dose rates (greater than 40 Gy/s) due to electron/ion recombination
Solution Approach 1:
The patent changes the operating parameters of the ionization chamber by applying a reduced voltage (e.g., 50-100 volts) across the electrodes, which is significantly lower than conventional voltages (e.g., 500 volts). This parameter change reduces the electric field strength, thereby reducing electron/ion recombination losses and improving measurement accuracy for high dose rate FLASH radiotherapy while maintaining adequate signal levels for measurement
2Power
If high voltage is applied to collect electron/ion pairs in an ionization chamber, then the current signal is strong enough for measurement, but electron/ion recombination increases at high dose rates, reducing measurement accuracy
Solution Approach 1:
The patent optimizes the voltage parameter to a specific range (50-100 volts) that balances two competing requirements: it is high enough to collect sufficient electron/ion pairs to generate a measurable current signal, but low enough to minimize electron/ion recombination losses. This optimized parameter setting resolves the contradiction between signal strength and measurement accuracy for high dose rate measurements
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
Accurately measures high radiation dose rates, including FLASH radiotherapy, with an accuracy of better than 98%, and is compatible with existing radiotherapy systems.
Implementation Method 1
emission of secondary electrons from the emitting electrode provides a majority of the current
Implementation Method 2
measure radiation dosage and/or dose rate based on radiation induced ionization in a gas
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A radiotherapy dose rate monitor system includes an emitting electrode 320 configured to be impinged by radiotherapy radiation; a collecting electrode 320a configured to form an electrical circuit with said emitting electrode, a current measurement device configured to measure a current through said emitting and collecting electrodes indicative of a dose of said radiotherapy radiation, and a chamber enclosing a gas 350. Emission of secondary electrons from the emitting electrode provides a majority of the current.