Radiotherapy Cryostat Attenuation Characterization With Gantry Imaging
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Solution Overview
Problem
Current methods for characterizing radiation attenuation through cryostat in radiotherapy devices, such as Farmer chamber measurements, are time-consuming and prone to errors due to air gaps and require costly equipment, and fail to account for beam divergence in multi-shell cryostats.
Innovation Solution
A method using on-gantry imaging devices to acquire multiple images over a 360-degree gantry range, enabling a fully automated imaging device-driven numerical model to determine radiation attenuation through the cryostat, which can be integrated into a treatment planning system to adjust beam intensity and compensate for cryostat inhomogeneities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Farmer chamber measurements are used to characterize cryostat attenuation, then attenuation magnitude can be obtained, but the process becomes time-consuming and prone to errors
Solution Approach 1:
The patent replaces the mechanical Farmer chamber measurement system with an optical/imaging-based system. The imaging device captures images of the radiation field through the cryostat, and a numerical model processes these images to determine attenuation characteristics. This substitution eliminates the need for physical chamber placement and manual measurements, dramatically reducing measurement time while maintaining or improving accuracy.
Solution Approach 2:
The patent creates a numerical model that replicates the physical measurement process. Instead of directly measuring attenuation with physical equipment, the system captures images and uses computational algorithms to calculate attenuation properties. This copying approach allows for faster, automated analysis without the time-consuming steps of physical chamber measurements.
2Measurement precision
If Farmer chamber measurements are used, then attenuation can be determined, but costly equipment and air gaps introduce errors
Solution Approach 1:
The patent replaces the Farmer chamber measurement system with an imaging-based system that eliminates air gaps. The imaging device captures images through the radiation field without requiring physical chambers that create air interfaces. This substitution removes the source of air gap errors entirely while also eliminating the need for costly specialized measurement equipment.
Solution Approach 2:
The patent introduces a numerical model as an intermediary between the imaging device and the attenuation measurement. Instead of directly measuring with physical equipment that introduces errors, the system uses computational algorithms to derive attenuation properties from images. This intermediary processing step eliminates harmful air gaps and reduces equipment-related errors.
3Loss of information
If Farmer chamber measurements are used for a single cryostat shell, then attenuation along an angular axis can be determined, but beam divergence in multi-shell cryostats is neglected
Solution Approach 1:
The patent transitions from one-dimensional angular axis measurements to two-dimensional image-based measurements. The imaging device captures the radiation field across multiple dimensions, allowing the numerical model to account for beam divergence and multi-shell interactions. This dimensional expansion provides complete attenuation information without requiring complex multi-angle measurements for each shell.
Solution Approach 2:
The patent creates a universal imaging-based measurement system that handles multi-shell cryostats of varying complexity. Instead of requiring separate measurement procedures for different shell configurations, the numerical model processes images to extract attenuation properties for any multi-shell arrangement. This universal approach accounts for beam divergence and shell interactions automatically, regardless of the specific cryostat design.
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 method provides a faster and more accurate characterization of cryostat attenuation, reducing errors and allowing for precise dose delivery by accounting for variations in beam attenuation, thereby improving treatment planning accuracy.
Implementation Method 1
One such example is the attenuation of radiation caused by passing it through a cryostat
Data Source
AI summary
Disclosed herein is a method of characterising physical properties of an attenuating element in a radiotherapy device having a radiotherapy radiation source and a radiotherapy radiation detector on respective sides of the attenuating element. The method comprises obtaining an average detected radiotherapy radiation intensity at two or more locations around the attenuating element, comparing the detected intensity at one location with the average intensity, and characterising a corresponding physical property based on the comparison.