Six-DOF Phantom for IGRT Positioning Accuracy
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Solution Overview
Problem
Image-guided radiation therapy (IGRT) systems face challenges in ensuring accurate positioning and mechanical correction of patients during treatment, which can lead to deviations in radiation delivery, potentially endangering nearby radiation-sensitive tissues.
Innovation Solution
A phantom reference object with embedded markers is used to simulate patient positioning, allowing for adjustments through six degrees of freedom, enabling the IGRT apparatus to assess and correct its accuracy by comparing measured and predetermined offsets, thereby ensuring precise radiation delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a phantom reference object with six degrees of freedom adjustment is used to simulate patient positioning, then the measurement precision and accuracy of positioning assessment is improved, but the device complexity increases
Solution Approach 1:
The phantom device is divided into separate functional components: a base plate for positioning, a ball joint mechanism for rotational adjustments, and a body with embedded markers. This segmentation allows each component to be optimized independently while maintaining overall measurement precision.
Solution Approach 2:
The phantom incorporates adjustable parameters including six degrees of freedom (three translational and three rotational) that can be modified to simulate various patient positioning scenarios. This parameter variability enables comprehensive accuracy assessment without requiring multiple different devices.
2Reliability
If the phantom is secured at a predetermined offset and the robotic couch is allowed to compensate, then the reliability of the correction system is improved, but the time required for quality control increases
Solution Approach 1:
The phantom is pre-positioned at known predetermined offsets before the quality control process begins. This preliminary setup allows the system to immediately test correction accuracy without requiring complex real-time adjustments during the measurement process.
Solution Approach 2:
The system uses detected marker positions to provide feedback to the robotic couch control system, which then applies corrections. This closed-loop feedback mechanism ensures reliable correction assessment while streamlining the quality control process through automated rather than manual adjustment procedures.
Data Source
AI summary
This invention provides a device for checking the performance of an image-guided radiation therapy (IGRT) apparatus. The device (referred to here as a phantom) has a central body with detectable markers, rotatably suspended on a ball joint so that the pitch, roll, and yaw may be adjusted. The body is secured against a base plate, which in turn may be positioned laterally, longitudinally, and vertically within the patient treatment area. Thus, the phantom can be adjusted through six degrees of freedom so as to simulate patient positioning. To perform quality control, the phantom is secured at a predetermined offset, and the position is detected by the IGRT apparatus. The robotic couch is then allowed to compensate, a second measurement is made. The measured values are compared with the predetermined offset to assess both the accuracy in detecting the position of the phantom, and the accuracy of the mechanical correction.