Transmission Calorimeter for FLASH Dose Measurement Without Beam Perturbation
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Solution Overview
Problem
Conventional ionisation chambers are unsuitable for measuring high dose rates in FLASH radiotherapy due to ion recombination effects, leading to significant measurement uncertainties, and existing calorimeters either perturb the radiation beam or are expensive and have limited lifespan.
Innovation Solution
A transmission calorimeter with a core that minimally absorbs radiation energy, allowing it to measure dose rates without perturbing the beam, using a thin, low-density material like aluminum and sensors to measure temperature changes, with optional compensation for ambient temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ionisation chambers are used to measure high dose rates in FLASH radiotherapy, then the measurement can be performed, but ion recombination effects cause significant measurement uncertainties
Solution Approach 1:
The patent replaces the ionisation chamber (electrical measurement system) with a calorimeter (thermal measurement system). The calorimeter measures temperature changes caused by radiation energy deposition, avoiding ion recombination issues inherent in electrical measurement systems at high dose rates. This substitution of measurement mechanism resolves the contradiction between being able to measure high dose rates and maintaining measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from electrical charge (ionisation) to temperature change (calorimetry). By measuring temperature rather than ion charge, the system avoids the ion recombination problem that occurs at high dose rates, thereby improving measurement reliability while maintaining the ability to measure high dose rate radiation.
2Measurement precision
If conventional calorimeters are used to measure radiation dose, then accurate dose measurements can be obtained, but the calorimeter perturbs the radiation beam
Solution Approach 1:
The patent applies local quality by making the calorimeter core extremely thin (0.05-0.5 mm) and low-density, so that only a small fraction of the radiation beam is absorbed. This local optimization of material properties allows the calorimeter to measure dose accurately while minimizing beam perturbation, resolving the contradiction between measurement accuracy and beam disturbance.
Solution Approach 2:
The patent uses a thin calorimeter core that absorbs only a small portion of the radiation energy (partial action) rather than allowing complete energy deposition. This partial absorption is sufficient for measurement while avoiding the beam perturbation that would occur with a thicker, more absorptive calorimeter design.
3Productivity
If transmission ionisation chambers with combined electronics are developed to operate at FLASH dose rates, then high dose rate measurement is enabled, but uncertainty in dose quantification increases
Solution Approach 1:
The patent substitutes the electronic measurement system (ionisation chamber with electronics) with a thermal measurement system (calorimeter). This substitution eliminates the source of uncertainty in dose quantification by measuring temperature changes that are directly proportional to energy deposition, providing accurate dose measurement capability at FLASH dose rates without the electronic correction uncertainties.
4Measurement precision
If silicon detectors are used to measure high dose rates, then measurement capability is improved, but the detectors are expensive and have limited lifespan
Solution Approach 1:
The patent uses a calorimeter with a thin core made from inexpensive, radiation-resistant materials (aluminum, copper, titanium, silver, or gold). These materials are cheaper than silicon detectors and do not suffer from radiation-induced damage limiting lifespan. The calorimeter can be easily replaced if needed, providing a cost-effective solution for high dose rate measurement.
Solution Approach 2:
The patent changes the detector material from silicon (which has limited lifespan due to radiation damage) to thin-layer metals and alloys that are more resistant to radiation effects. This material parameter change maintains measurement capability while improving durability and reducing cost.
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 calorimeter provides accurate dose measurements at high dose rates with reduced uncertainty, suitable for FLASH radiotherapy, by integrating fluence measurement directly in the beam path without beam perturbation.
Implementation Method 1
a core for receiving and transmitting said radiation along a radiation path which passes through said core
Implementation Method 2
at least one sensor for measuring the temperature change of the core
Implementation Method 3
The calorimeter may include a body which is not located on said radiation path and which is thermally insulated from the calorimeter core, and at least one sensor for measuring a temperature change of said body
Data Source
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AI summary
A transmission calorimeter for measuring the dose of a beam of radiation includes a core for receiving and transmitting said radiation along a radiation path which passes through said core and at least one sensor for measuring the temperature change of the core, wherein the energy of said radiation absorbed by the calorimeter is less than or equal to the energy that would be absorbed by transmitting said radiation through 2 mm of water.