Patient Surface Model Offset Detection for Radiotherapy Alignment
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Solution Overview
Problem
Existing patient monitoring systems for radiotherapy struggle to set appropriate thresholds for warning or halting treatment due to patient movement, leading to potential misdirection of radiation beams and irradiation of healthy tissue.
Innovation Solution
A monitoring system that generates a model of the patient's surface, compares it with a target model, and calculates an offset value relative to the radiation path to determine if patient movement is detrimental, using a stereoscopic camera system and light patterns to track markers on the treatment apparatus for accurate positioning and orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low threshold is set for generating a warning or halting treatment, then patient safety is improved by preventing misdirection of radiation beams, but treatment may be halted unnecessarily reducing productivity
Solution Approach 1:
The system dynamically changes the monitoring parameter from simple 3D point position to 5D surface model parameters including depth information and surface curvature. This allows for more nuanced assessment of patient movement, enabling safer thresholds to be set without excessive false alarms by considering the geometric context of surface changes rather than just positional offsets.
Solution Approach 2:
The patent replaces traditional mechanical positioning sensors with optical imaging systems (stereoscopic cameras) that capture surface geometry. This substitution enables non-contact, high-precision monitoring of patient surface changes, providing more reliable detection of actual clinically significant movements versus minor positioning variations.
2Productivity
If a high threshold is set for generating a warning or halting treatment, then treatment productivity is improved by reducing unnecessary halts, but radiation beams may be misdirected causing harmful effects
Solution Approach 1:
The system adds depth information (5th dimension) to the traditional 3D surface modeling by incorporating surface curvature and slope data. This dimensional enrichment allows the monitoring system to distinguish between movements that are clinically significant and those that are not, enabling higher safety thresholds without increasing risk of misdirected radiation by filtering out geometrically insignificant variations.
Solution Approach 2:
The patent introduces a sophisticated image processing and analysis system as an intermediary between the camera sensors and the treatment control system. This intermediary layer processes raw surface data through Procrustes analysis and geometric modeling to generate clinically meaningful metrics, allowing for more accurate threshold setting that balances safety and productivity.
3Device complexity
If traditional 3D point-based monitoring is used, then device complexity is kept low, but measurement precision is insufficient to reliably detect clinically significant movement
Solution Approach 1:
The patent segments the patient surface into multiple tracked points and combines their data into a comprehensive surface model. By dividing the monitoring task into discrete point tracking and then synthesizing the results into a unified 5D surface representation, the system achieves high measurement precision while maintaining manageable system complexity through modular processing.
Data Source
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AI summary
A monitoring system for monitoring the positioning of a patient (20) relative to a treatment apparatus (16) operable to deliver radiation along a radiation path is provided. A model generation module (58) is arranged to generate a model of a surface of a patient (20) being monitored. A comparison module (64) determines a transformation required to match the generated model to the stored model target surface. An offset determination module (68) then utilizes the transformation and data indicative of a current position of a treatment apparatus (16) to determine an offset value indicative of the offset of the surface of a patient (20) relative to an axis corresponding to a determined current radiation path for radiation generated by the treatment apparatus (16) applied to a patient (20). If the offset value exceeds a threshold, a warning may be generated or treatment may be halted.