Tumor Motion Tracking Using COM-Surrogate Correlation
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Solution Overview
Problem
Existing tumor tracking methods during radiotherapy are inadequate for precise localization due to tumor motion, especially with invasive fiducials and unreliable external surrogates, and traditional imaging techniques provide blurred or motion-averaged data, leading to challenges in delivering focused radiation.
Innovation Solution
Methods for determining the center of motion (COM) of a tumor and correlating it with a surrogate position to continuously update the tumor's location using non-invasive surrogates like infrared reflectors or RF-emitting fiducials, combined with imaging data to calculate displacement vectors, enabling real-time tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional high-resolution imaging (MRI, PET) is used to track tumor location, then image quality is improved, but image acquisition time increases and motion blur occurs
Solution Approach 1:
The patent uses a surrogate object (external marker or internal fiducial) that copies the tumor's motion characteristics. Instead of continuously imaging the moving tumor, the system tracks the surrogate which replicates the tumor's positional changes, enabling indirect but accurate tumor location determination without prolonged imaging exposure
Solution Approach 2:
The patent establishes a correlation model between the surrogate position and tumor position before treatment begins. This preliminary characterization of the tumor-surrogate relationship allows real-time tumor tracking during treatment using only surrogate measurements, avoiding the need for continuous high-resolution tumor imaging
2Measurement precision
If fiducials are implanted at the tumor site for continuous tracking, then tumor position data accuracy is improved, but patient invasiveness increases
Solution Approach 1:
The patent employs surrogates that serve dual purposes: external markers can be tracked using non-invasive optical or electromagnetic systems, while internal fiducials provide continuous positional data without requiring repeated invasive procedures. The system adapts to different surrogate types (external or internal) based on patient-specific needs and tumor characteristics
Solution Approach 2:
The patent introduces a surrogate as an intermediary between the tumor and the tracking system. This mediator object translates tumor motion into detectable signals without requiring direct continuous imaging of the tumor itself, reducing both invasiveness and motion blur while maintaining tracking accuracy through the established surrogate-tumor correlation
3Object-affected harmful factors
If external surrogates are used for tumor tracking, then patient invasiveness is reduced, but correlation reliability between surrogate and tumor position deteriorates
Solution Approach 1:
The patent implements dynamic updating of the surrogate-tumor correlation model during treatment sessions. Rather than relying on a static pre-treatment correlation, the system continuously refines the relationship parameters based on real-time measurements and any observed drift, maintaining reliability even when patient positioning or tumor motion patterns change
Solution Approach 2:
The patent incorporates feedback mechanisms where the tracking system monitors surrogate position and compares it against the established correlation model. When deviations or drift in the surrogate-tumor relationship are detected, the system triggers recalibration or adjustment of the correlation parameters, ensuring continuous reliability of the tracking accuracy throughout the treatment course
Data Source
AI summary
Disclosed herein are methods for determining the location of a moving target region (e.g., a tumor) based on the location of the center of its range of motion and the location of a target region surrogate, during a radiotherapy treatment session or a quality assurance (QA) session. These methods comprise characterizing the motion range of the target region, calculating the location of the center of the motion range, and determining a correlation between the position of the target region surrogate and the displacement of the target region from the center of the motion range as the target region moves.