Multi-Leaf Collimator Leaf Tracking With Radioluminescent Markers

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Solution Overview

Problem

Existing multi-leaf collimator systems in radiotherapy require complex vision systems and external light sources for accurate leaf positional readout, which add complexity and risk of component failure, and can obstruct the radiation beam.

Innovation Solution

Utilization of radioluminescent markers, such as tritium gas tubes, which emit a continuous low-level light source due to beta decay, eliminating the need for external illumination and allowing direct imaging of leaf positions without obstructing the radiation path.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If complex vision systems and external light sources are used for accurate leaf positional readout, then measurement precision is improved, but device complexity increases and reliability decreases

Engineering Contradiction:

Improveleaf positional readout accuracyVSAvoidvision system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The MLC leaves are equipped with radioluminescent markers that self-illuminate without requiring external light sources. The markers contain radioactive material that emits light continuously, allowing the vision system to track leaf positions without complex illumination infrastructure, thereby reducing device complexity while maintaining measurement precision.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The radioluminescent markers are pre-installed on the MLC leaves during manufacturing. This preliminary placement ensures that the markers are always in position to be imaged by the vision system, eliminating the need for complex real-time illumination control and reducing device complexity while maintaining accurate positional readout.

Inventive Principle:

Principle #10Preliminary action

2Measurement precision

If external light sources are used for illumination, then measurement precision is improved, but reliability decreases due to component failure risk

Engineering Contradiction:

Improveleaf positional readout accuracyVSAvoidsystem reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The radioluminescent markers generate their own light through radioactive decay, eliminating the need for external light sources that can fail. This self-illuminating property significantly improves system reliability while maintaining the ability to achieve accurate leaf positional readout through the vision system.

Inventive Principle:

Principle #25Self-service

3Measurement precision

If complex vision systems with external light sources are used, then measurement precision is improved, but the radiation beam is obstructed

Engineering Contradiction:

Improveleaf positional readout accuracyVSAvoidradiation beam obstruction

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The external light sources and their associated illumination optics are extracted from the radiation beam path. Instead, radioluminescent markers are placed directly on the MLC leaves, allowing the vision system to acquire images without components obstructing the radiation beam, thereby eliminating beam obstruction while maintaining measurement precision.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS12551722B2Multi-leaf collimator vision system

Publication Date: 2026.02.17 ELEKTA AB

AI summary

A multi-leaf collimator can comprise two banks of leaves facing each other across the radiation field, and an actuation member or actuation means configured to control the location of each leaf, for example, to control the degree to which each leaf is extended into the radiation field. The leaves of the multi-leaf collimator can comprise at least one radioluminescent marker that can emit illumination light, which can be used to accurately determine the position of the leaves.