3D HDR Source Tracking via Flat Panel Detector and Markers
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Solution Overview
Problem
In brachytherapy, accurately comparing the actual position of a high dose rate (HDR) radiation source with the intended treatment plan is challenging due to the lack of real-time feedback, which can lead to deviations from the planned treatment, and existing methods expose patients to additional radiation or violate safety regulations by using multiple radiation sources simultaneously.
Innovation Solution
A method using a flat panel detector and markers at known positions to reconstruct the 3D position of the HDR source, allowing for real-time comparison with the intended treatment plan by calculating lines defined by marker positions and their projections, and inferring the source position, thereby establishing a correspondence between detection and treatment plan coordinate systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fluoroscope image is used to track the HDR source position in real-time, then the source position can be visualized, but the patient is exposed to additional radiation dose
Solution Approach 1:
The patent introduces markers as intermediary objects that are imaged by the detector to indirectly determine the HDR source position. Instead of directly imaging the HDR source (which would require additional radiation), the system images markers whose positions relative to the source are known, thereby inferring source position without direct imaging of the source itself.
Solution Approach 2:
The system creates a virtual model or copy of the treatment geometry by imaging markers and computationally reconstructing the source position. This virtual representation allows for real-time verification of source position without requiring physical repositioning or additional radiation exposure to the patient.
2Productivity
If multiple radiation sources are used simultaneously for imaging and treatment, then real-time feedback is available, but safety regulations are violated
Solution Approach 1:
The patent makes the single HDR source perform multiple functions: it serves both as the treatment radiation source and as the imaging source for tracking its own position. The same HDR source that delivers treatment radiation is used to illuminate the markers for detection, eliminating the need for separate imaging and treatment sources.
Solution Approach 2:
The HDR source essentially images itself by illuminating the markers during treatment delivery. The system uses the treatment source's own radiation to create the imaging signal, allowing the treatment process to self-verify its accuracy without external intervention or additional sources.
3Ease of operation
If no real-time feedback is provided during HDR treatment, then the treatment can be delivered according to plan, but deviations from the planned treatment cannot be detected
Solution Approach 1:
The patent implements a feedback loop where the detected marker positions are continuously compared with the planned treatment geometry. The system calculates the actual HDR source position from marker images and provides real-time feedback by comparing this with the intended source position, allowing for immediate detection and correction of any deviations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables real-time, accurate comparison of the delivered treatment with the planned treatment, reducing human error and potential radiation exposure, while ensuring compliance with safety regulations by using a single radiation source for imaging and treatment.
Implementation Method 1
a flat panel detector (FPD) ... to enable a comparison between an intended treatment plan and an actually delivered treatment, by reconstructing the radiation source position based on projections of markers at known locations on an image acquired using a two-dimensional radiation detector
Data Source
AI summary
A method and apparatus are used to compare an intended treatment plan using a radiation source with a delivered plan. This done by arranging markers at known three-dimensional (3D) positions in a detection reference system between a two dimensional radiation detector configured to acquire images generated by radiation emitted by the radiation source and an area where the radiation source is positioned during a treatment. The positions of projections of the markers on an image detected are determined when the radiation source is at a treatment position in an intended treatment plan reference system. A plurality of lines in the detection reference system are calculated, each line being defined by a 3D position of a marker and a 3D position of a corresponding projection of the marker on the detector according to the image. A 3D position of the radiation source in the detection reference system is inferred based on the calculated lines. If no correspondence between the detection reference system and the intended treatment plan reference system is available, the inferred 3D position is matched with the treatment position to extract the correspondence between the detection reference system and the an intended treatment plan reference system. If the correspondence between the detection reference system and the an intended treatment plan reference system is available, the inferred 3D position is compared with the treatment position.