Piezoelectric Leaf Module for Multi-Leaf Collimator
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Solution Overview
Problem
Multi-leaf collimators face challenges in achieving precise and stable adjustability of leaf units due to issues like backlash and slackness in drive mechanisms, which affect the accuracy and compactness of the irradiation head during radiation therapy.
Innovation Solution
A leaf module design where the leaf drive unit encloses the leaf unit within a plane oriented substantially perpendicularly to the adjusting direction, providing precise guidance and eliminating slackness, using piezoelectric actuation and a guiding rod to enhance precision and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional electric motors with pinion and gear rod-like drive engagement are used to position each leaf unit, then the leaf units can be displaced, but backlash and slackness in the drive transmissions result in poor adjustment precision and stability
Solution Approach 1:
The patent replaces conventional electric motors with pinion and gear rod-like drive engagement with piezoelectric motors that use ultrasonic vibration for direct drive. This substitution eliminates the mechanical transmission components (pinions, gear rods) that cause backlash and slackness, thereby improving adjustment precision while reducing drive transmission complexity
Solution Approach 2:
The patent introduces a friction element as an intermediary between the piezoelectric motor and the leaf unit. The ultrasonic vibration of the piezoelectric motor generates frictional force through this intermediary element, enabling precise positioning of the leaf unit without requiring complex mechanical transmissions
2Manufacturing precision
If the number of leaves within the leaf units is increased to precisely recreate the shape of the treatment object, then the shape accuracy improves, but the space required for housing electric motors and drive transmissions becomes extremely limited
Solution Approach 1:
The patent replaces bulky conventional electric motors and their associated pinion and gear rod-like drive transmissions with compact piezoelectric motors. This substitution dramatically reduces the volume required for housing drive mechanisms, enabling the accommodation of increased numbers of leaves for precise shape recreation within the limited space of the irradiation head
Solution Approach 2:
The patent changes the driving mechanism from high-torque conventional motors to ultrasonic vibration-based piezoelectric motors. This parameter change in the drive mechanism allows for compact design while maintaining the capability to precisely position multiple thin leaves for accurate treatment object shape recreation
3Ease of operation
If conventional electric motors are used in the irradiation head, then the motors can drive the leaves, but the motors emit disruptive magnetic fields that interfere with MR-imaging and linear acceleration in MR-Linac systems
Solution Approach 1:
The patent replaces conventional electric motors that generate disruptive magnetic fields with piezoelectric motors that operate on ultrasonic vibration principles. This substitution eliminates the harmful magnetic field interference with MR-imaging and linear acceleration, while maintaining full leaf positioning capability through friction-based direct drive
Solution Approach 2:
The patent converts the potential harm of magnetic field interference by replacing the motor type entirely. The piezoelectric motor's ultrasonic vibration mechanism provides a beneficial alternative that not only eliminates magnetic interference but also offers high positioning accuracy and compact design suitable for the irradiation head
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
This design achieves precise and stable adjustability of the leaf unit, reducing the need for fine adjustments and allowing for a more compact and cost-effective multi-leaf collimator with improved accuracy and reduced interference between adjacent leaf drive units.
Implementation Method 1
the leaf drive unit comprises at least one drive mechanism which operates based on piezoelectric actuation
Data Source
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AI summary
The invention relates to a leaf module (1) for a multi-leaf collimator, comprising a leaf unit (2) and a leaf drive unit (3), wherein the leaf unit (2) comprises a leaf (4) for shielding beams from a selected area, the leaf unit (2) is mounted displaceably in an adjusting direction (5) with relation to the leaf drive unit (3), wherein the leaf drive unit (3) is designed to displace the leaf unit (2) linearly in the adjusting direction (5), and the leaf drive unit (3) comprises at least one drive mechanism (9) which operates based on piezoelectric actuation, being designed in such a way that the leaf drive unit (3) thoroughly encloses the leaf unit (2) within a plane being oriented substantially perpendicularly related to the adjusting direction (5). Furthermore, the invention relates to a multi-leaf collimator comprising a plurality of leaf modules (1) according to the invention. The invention facilitates a design of leaf modules (1) with a shape being as compact as possible, and wherein both precise and stable adjustability of the leaf unit (2) is achieved. In this way improvements to multi-leaf collimators are provided likewise.