LINAC Isocenter Analysis via 3D Beam Axis Construction
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Solution Overview
Problem
Current methods for analyzing the isocenter of a medical linear accelerator (LINAC) using two-dimensional x-ray transmission images are limited, as they fail to accurately reflect the complex three-dimensional processes, making it difficult to intuitively understand and address issues related to LINAC isocenter precision.
Innovation Solution
The method involves transforming two-dimensional radiation transmission images into a three-dimensional coordinate system to determine the radiation isocenter by constructing three-dimensional radiation beam axes and calculating the maximum beam axis miss distance, allowing for a more accurate and intuitive analysis of isocenter size and marker placement errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-dimensional x-ray transmission images are used to analyze LINAC isocenter, then the analysis process is simple, but the measurement precision and ability to reflect complex three-dimensional processes is insufficient
Solution Approach 1:
The patent transforms two-dimensional EPID images into three-dimensional space by constructing 3D radiation beam axes from multiple 2D images taken at different gantry angles. This dimensional transformation allows accurate representation of the complex 3D isocenter geometry while maintaining the simplicity of 2D image acquisition, thereby resolving the contradiction between analysis simplicity and measurement precision.
2Measurement precision
If three-dimensional coordinate system transformation is implemented, then the measurement precision and analysis accuracy improve, but the device complexity and computational requirements increase
Solution Approach 1:
The patent segments the complex 3D isocenter analysis into manageable steps: (1) acquiring 2D EPID images at different gantry angles, (2) identifying beam axis positions in each 2D image, (3) constructing 3D beam axes by combining 2D data, and (4) calculating isocenter properties from 3D axes. This segmentation reduces computational complexity while maintaining measurement precision.
Solution Approach 2:
The patent performs preliminary actions by acquiring multiple 2D EPID images at predetermined gantry angles before performing the 3D coordinate transformation. This preliminary data collection simplifies the subsequent 3D reconstruction process and reduces computational complexity during the actual isocenter analysis.
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 approach provides a more accurate and flexible analysis of the LINAC isocenter, enabling better precision in radiation therapy by minimizing beam axis miss distances and accounting for marker placement errors and couch walkout, thereby improving treatment accuracy.
Implementation Method 1
measuring the x-ray intensity transmitted through a patient from a radiation port during a treatment session
Implementation Method 2
acquire a first two-dimensional (2D) radiation transmission image indicative of a radiation field of the first radiation beam after passing by a radiation opaque marker
Data Source
AI summary
Systems and methods for determining a radiation isocenter of a linear accelerator (LINAC). Determining the radiation isocenter may include determining a set of three-dimensional (3D) radiation beam axes of the LINAC from two-dimensional (2D) radiation transmission images. The radiation isocenter may be determined based on at least the set of 3D radiation beam axes. Determining the set of 3D radiation beam axes may including constructing a 3D radiation beam axis based on a determined location of a beam axis of a radiation beam generated with a gantry of the LINAC at an angle relative to a reference gantry angle, a determined center of a shadow of a radiation opaque marker in the radiation field of the radiation beam, and the gantry angle.