Patient Positioning Apparatus Using Multidimensional Optimization
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Solution Overview
Problem
The positioning of patients during radiation therapy is slowed down and less accurate when using X-ray fluoroscopy from oblique directions due to longer source image distances, leading to prolonged processing times and reduced precision, especially when the shape of the evaluation function has a valley structure with extremely small values.
Innovation Solution
A positioning apparatus and method that utilize a radiograph acquiring element, DRR generation element, and positioning element with multidimensional and 1-dimensional optimization elements to optimize parameters for rotation and translation, determining the necessity of 1-dimensional optimization based on evaluation function values, and employing different evaluation functions and tolerances for convergence, enabling efficient optimization and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If X-ray fluoroscopy is performed from oblique directions to the patient, then the source image distance (SID) gets longer, but the processing time increases and positioning accuracy deteriorates
Solution Approach 1:
The optimization process is divided into two distinct segments: multidimensional optimization for rotation and translation parameters, and 1-dimensional optimization for translation along radiography directions. This segmentation allows each optimization stage to focus on specific parameters, reducing overall computation time while maintaining accuracy despite longer SID
Solution Approach 2:
The patent transitions from conventional single-dimension optimization to multidimensional optimization, adding rotational parameters to the traditional translational parameters. This dimensional expansion enables comprehensive optimization of fluoroscopic projection parameters, allowing the system to efficiently handle the increased complexity introduced by longer SID in oblique directions
2Length of stationary object
If X-ray fluoroscopy is performed from oblique directions, then the SID gets longer, but the positioning accuracy is reduced
Solution Approach 1:
The patent implements dynamic optimization where the system adaptively determines whether to perform 1-dimensional optimization based on evaluation function values from multidimensional optimization. This dynamic approach ensures positioning accuracy is maintained by applying additional optimization steps only when the evaluation function indicates potential for improvement, even with longer SID
Solution Approach 2:
The system uses evaluation function values as feedback to determine the necessity of performing 1-dimensional optimization. This feedback mechanism allows the system to automatically adjust the optimization process, ensuring high positioning accuracy by applying refinement steps when needed while avoiding unnecessary computations when accuracy is already sufficient
3Measurement precision
If multidimensional optimization is performed to optimize fluoroscopic projection parameters, then positioning accuracy improves, but calculation time increases
Solution Approach 1:
The optimization is segmented into multidimensional optimization for rotation and translation, followed by conditional 1-dimensional optimization. This segmentation allows the system to achieve high positioning accuracy through comprehensive parameter optimization while controlling calculation time by applying the more computationally intensive 1-dimensional optimization only when evaluation function values indicate potential for improvement
Solution Approach 2:
The system performs partial optimization by determining whether 1-dimensional optimization is necessary based on evaluation function values. Instead of always performing full multidimensional optimization, the system applies optimization steps selectively, achieving sufficient positioning accuracy while reducing unnecessary calculation time
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 allows for efficient optimization operations, reducing calculation time and enhancing the accuracy of patient positioning by optimizing parameters along radiography directions, even when the evaluation function has a valley structure, and ensures higher precision by determining the need for 1-dimensional optimization within the multidimensional optimization process.
Implementation Method 1
a radiograph acquiring element that obtain a 2-dimensional radiograph in two different directions of a subject by a radiography system having a radiation irradiation element and a radiation detector
Implementation Method 2
a radiograph acquiring element that obtain a 2-dimensional radiograph in two different directions of a subject by a radiography system having a radiation irradiation element and a radiation detector
Data Source
AI summary
A positioning apparatus and a positioning method has a control element and function 40 includes a radiograph acquisition element 41 that acquires radiograph data detected by two radiography systems selected from a group consisting of a flat panel detector, a DRR (Digital Reconstructed Radiograph) generation element 42 that generates DRR in two different directions by virtually performing fluoroscopic projection relative to the 3-dimensional CT data obtained through the network 17, a positioning element 43 that positions a CT to the X-ray fluoroscopic radiograph obtained from two radiography systems, and a displacement distance calculation element 44 that calculates a displacement distance of the tabletop 31 based on the gap between radiographs for improved positioning. The positioning element 43 has a multidimensional optimization element 45 and a 1-dimensional optimization element 46 that optimize parameters relative to rotation and translation of the fluoroscopic projection to maximize an evaluation function that evaluates a matching degree between the DRR and the X-ray fluoroscopic radiograph.