Multi-Leaf Collimator Calibration with Reference Blocks
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Solution Overview
Problem
Existing multi-leaf collimator (MLC) calibration techniques are time-consuming and often provide inaccurate indications of leaf positions, especially due to the inability to measure the minor offset between imaging markers and leaf tips, leading to increased production costs and computational intensity.
Innovation Solution
A method involving the use of calibration and validation blocks to accurately determine the minor offset between imaging markers and leaf tips, utilizing a camera to image these markers while the leaves are aligned with the blocks, allowing for precise leaf positioning through image processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing calibration techniques are used to determine leaf positions, then the calibration process can be completed, but the measurement precision of leaf positions is insufficient due to inability to measure minor offset
Solution Approach 1:
A calibration block with a reference surface is introduced as an intermediary object between the imaging system and the collimator leaves. The reference surface provides a known geometric reference that enables accurate measurement of the minor offset between the imaging marker and the leaf tip, thereby improving measurement precision without requiring direct modification of the leaves themselves.
Solution Approach 2:
The calibration block creates a geometric copy or reference model of the desired leaf position relationship. By imaging the calibration block alongside the leaves, the system can compare the actual leaf positions against the known reference geometry, enabling precise determination of minor offsets through image processing and geometric calculation.
2Productivity
If existing calibration techniques are used, then calibration can be performed, but the calibration process is time-consuming
Solution Approach 1:
The calibration block is pre-manufactured with a reference surface having precisely known geometric dimensions and relationships. This preliminary preparation of reference geometry allows the actual calibration process to proceed quickly by simply imaging the pre-established reference, rather than requiring time-consuming measurements during the calibration procedure itself.
Solution Approach 2:
The patent replaces complex mechanical measurement systems with an optical imaging-based measurement approach. By using a camera to image the calibration block and leaves, and then calculating positions through image processing and geometric relationships, the system achieves high precision calibration without the time-consuming mechanical measurements of traditional methods.
3Difficulty of detecting and measuring
If imaging markers are used to indicate leaf positions, then leaf positions can be detected, but the minor offset between markers and leaf tips cannot be measured
Solution Approach 1:
The calibration block serves as a mediator that bridges the gap between the imaging marker and the leaf tip. By providing a reference surface with known geometric relationship to both the marker position and the expected leaf tip position, the system can calculate the minor offset through geometric relationships rather than requiring direct measurement of the inaccessible leaf tip.
Solution Approach 2:
The calibration process uses the known geometry of the calibration block as feedback to determine the actual leaf positions. By comparing the imaged positions of markers and the reference surface geometry, the system calculates the minor offset and uses this feedback information to correct and refine the leaf position measurements, achieving accurate determination despite the indirect measurement approach.
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 accurate and efficient calibration of MLC leaves, reducing setup time and costs by providing precise leaf positioning for optimal radiation beam shaping during radiotherapy.
Implementation Method 1
utilizing a camera to image these markers while the leaves are aligned with the blocks
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A computer-implemented method for calibrating a multi-leaf collimator of a radiotherapy device. The multi-leaf collimator comprises a plurality of leaves, each leaf comprising an imaging marker, wherein the radiotherapy device includes an imaging device configured to image the leaves. The method comprises: receiving, from the imaging device, an image of the multi-leaf collimator in a calibration position, wherein in the calibration position the tips of the leaves abut an edge of a rigid calibration block, the edge having a known calibration profile; calculating for each leaf, from the calibration profile and the location of the marker in the image, a minor offset of the marker relative to a reference point; and outputting calibration values based on the calculated minor offsets, wherein at least one leaf of the multi-leaf collimator is controlled based on the calibration values.