Radiotherapy Couch Drop Compensation via Spline Interpolation
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Solution Overview
Problem
Current radiation therapy couches face challenges in accurately correcting for bed surface drop due to patient weight and position changes, particularly the angle deviation, which affects irradiation precision and requires methods that do not interfere with X-ray imaging or increase patient dose.
Innovation Solution
A compensation method using cubic spline interpolation to estimate the drop amount of the couch top by decomposing patient weight and couch position into manageable parts, measuring drop amounts under controlled conditions, and applying cubic spline curves to calculate precise adjustments, ensuring accurate levelness correction without interfering with X-ray imaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an angle sensor is installed at the isocenter position to measure couch angle shift, then measurement precision is improved, but the sensor will be irradiated by X-rays affecting its operation and creating shadows in X-ray images
Solution Approach 1:
The patent extracts the measurement function from the isocenter position and relocates it to the couch control system. Instead of placing a sensor at the isocenter, the system calculates couch top position changes by integrating couch movement data from the control system, thereby avoiding X-ray irradiation while maintaining measurement capability
Solution Approach 2:
The patent introduces an intermediary calculation approach using couch movement data as a mediator. Rather than directly measuring angle at the isocenter, the system uses control system data to compute position changes, avoiding direct exposure to X-rays while obtaining the required measurement information
2Measurement precision
If image-guided radiotherapy technology is used to monitor placement deviation and calculate drop amount, then measurement precision is improved, but patient dose increases due to additional X-ray images
Solution Approach 1:
The patent extracts the measurement function from image-guided radiotherapy systems and relocates it to the couch control system. By using existing couch movement data to calculate drop amounts, the system eliminates the need for additional X-ray imaging, thereby maintaining measurement precision while avoiding increased patient radiation exposure
Solution Approach 2:
The patent enables the couch control system to self-measure and self-correct drop amounts using its own movement data. The system integrates couch movement information to calculate position changes and automatically compensates for drop, eliminating dependence on external image-guided systems and reducing patient dose
3Manufacturing precision
If the couch top position is moved to move the tumor to the isocenter, then treatment positioning is improved, but the couch top drops down due to gravity causing angle deviation
Solution Approach 1:
The patent applies preliminary compensation by calculating the expected drop amount based on couch movement distance and patient weight before treatment begins. The system pre-adjusts the couch position to account for the anticipated drop, ensuring the couch top remains level and the tumor stays accurately positioned at the isocenter throughout treatment
Solution Approach 2:
The patent implements a feedback mechanism where the system continuously monitors couch movement data and calculates real-time position changes. Based on this feedback, the system dynamically adjusts couch position to compensate for gravity-induced drop, maintaining accurate tumor positioning and couch levelness throughout the treatment process
Data Source
AI summary
A compensation method for bed surface drop before and after accelerator radiotherapy bed includes the following contents: the weight G is decomposed into N weights on average, the length L is decomposed into M positions on average, and then an experiment is carried out. The drop matrix HN×M of the couch top is measured by the experiment, by performing cubic spline interpolation on the rows of the matrix HN×M, and then performing cubic spline interpolation on the columns, the resulting cubic spline interpolation matrix SN×N1, M×M1 of HN×M has N*N1 rows and M*M1 columns, and then applies it to practice. The drop amount H obtained by the compensation method for bed surface drop before and after accelerator radiotherapy bed of the present invention is the optimal estimated value with the Least Sum of Square Error.