Radiotherapy Couch Sag Compensation for Precise Isocenter Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In image-guided radiotherapy (IGRT), the radiotherapy couch tends to sag due to the weight of the object and the extended position during CT scans, leading to positional errors that affect the accuracy of treatment delivery.
Innovation Solution
A method and system that utilize a two-modality apparatus with image acquisition and registration modules to determine the couch sag at different positions, using standard data to estimate the sag difference and align the target portion with the isocenter of the modality units, ensuring precise positioning of the object for accurate radiotherapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the couch extends longer from the support position into the bore of the CT gantry, then the radiotherapy treatment coverage is improved, but the couch sags or deflects along the longitudinal direction causing positional errors
Solution Approach 1:
The system performs preliminary measurement of couch sag at multiple positions along the longitudinal direction before radiotherapy treatment. By measuring the sag profile in advance and storing it as reference data, the system can compensate for positional errors during treatment without requiring real-time measurement, thus maintaining accuracy while allowing extended couch length
Solution Approach 2:
The system uses measured couch sag data to generate compensation values that are fed back into the positioning system. During radiotherapy treatment, these compensation values are applied to correct the couch position, ensuring that the target position accuracy is maintained despite the couch extension and resulting sag
2Adaptability or versatility
If the couch extends longer into the bore, then the treatment positioning flexibility is improved, but the deflection from horizontal baseline increases
Solution Approach 1:
The system pre-measures the couch deflection profile at multiple longitudinal positions when the couch is extended to different lengths. This preliminary characterization of the couch behavior under various extension conditions allows the system to predict and compensate for deflection at any given position, maintaining horizontal alignment accuracy across the full range of motion
Solution Approach 2:
The system changes the reference parameters by storing sag and deflection data at multiple longitudinal positions and using this variable reference data to compensate for position-dependent deflection. By adapting the compensation values based on the specific couch extension length and position, the system maintains accurate horizontal alignment across different operational configurations
Data Source
AI summary
A method and system for using in a two-modality apparatus. The two-modality apparatus comprises a couch with a table top, a first modality unit and a second modality unit. A second image of a target portion of an object when the table top is at a second working position of the second modality unit may be acquired. A second sag of the table top at a second measurement point of the table top according to the second image may be determined based on the image. A difference between a first sag of the table top at a first measurement point of the table top and the second sag may be estimated based on the second sag and standard data. The standard data provides a relationship relating to a sag of the table top positioned between the first modality unit and second modality unit.