Iris Diaphragm Collimator for Radiation Beam Shaping
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Solution Overview
Problem
Current irradiation devices with collimators for high-energy therapeutic beams face challenges in accurately shaping the radiation field to minimize exposure to surrounding healthy tissue, leading to significant side effects and increased treatment time due to penumbrae and leakage radiation, especially when treating irregularly shaped tumors.
Innovation Solution
The use of multiple coaxially aligned iris diaphragms with staggered and rotationally arranged leaves to create a polygonal beam cross-section that approximates a circular shape, allowing for precise adjustment and overlapping of irradiation areas to achieve a three-dimensional dosing profile with minimal penumbrae and leakage, using a simple linear actuation mechanism for efficient beam collimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If traditional collimators with shielding plates are used to restrict the irradiation field, then the beam size can be limited, but the shape cannot be precisely controlled and penumbrae occur at the borders
Solution Approach 1:
The collimator is divided into multiple independent diaphragm leaves (typically 6 or more) arranged radially around the beam axis. Each leaf can be independently adjusted to form a polygonal cross-section that approximates a circle, eliminating the penumbra problem by providing precise control over the beam boundary shape while maintaining structural feasibility.
2Manufacturing precision
If the shielding material thickness is increased to reduce penumbrae, then the border precision improves, but the device weight and size increase significantly
Solution Approach 1:
Instead of using a single thick shielding plate, the collimator employs multiple thin diaphragm leaves arranged radially. This segmentation allows the use of thinner material (6-10 cm total equivalent shielding) while achieving the same penumbra reduction effect, significantly reducing the weight and size of the collimator assembly.
3Device complexity
If traditional square or rectangular collimation is used, then the device complexity is low, but the surrounding tissue receives excessive radiation
Solution Approach 1:
The collimator uses multiple diaphragm leaves (typically 6) arranged radially to create a polygonal cross-section that approximates a circular shape. This curved geometry matches the typical shape of tumors and minimizes the irradiation of surrounding healthy tissue, reducing harmful effects while maintaining manageable device complexity.
4Manufacturing precision
If exchangeable fixed collimators are used to match tumor shapes, then the radiation application precision improves, but the treatment time and device complexity increase
Solution Approach 1:
The collimator employs adjustable diaphragm leaves that can be dynamically repositioned during treatment to adapt to different tumor shapes and sizes. This dynamic adjustment capability eliminates the need for exchanging fixed collimators, reducing treatment time while maintaining high radiation application precision for various tumor geometries.
Data Source
AI summary
An irradiation device for radiation treatment and a collimator (1) are used to define a beam of high-energy rays (2) with beam limitation by means of an iris diaphragm (5) having adjusting elements (7), and a mechanism that is used to direct the beams (2′) limited by the collimator (1) to the object to be treated (4) from all sides, wherein the parameters for direction, surface area, intensity and time of irradiation can be specified with the help of a control mechanism. An exact three-dimensional irradiation profile is produced, while keeping the costs and efforts regarding mechanical engineering, computation and irradiation time low. This is achieved by using at least one further iris diaphragm (6) located in coaxial alignment in the optical path, whereby the leaves (9, 9′, 9″, 9′″, 9″″, 9′″″) of the iris diaphragms (5, 6) are arranged in a staggered manner and in a rotational sense around their axis (11), so that the beam limited by the collimator (1) has the cross-section of a polygon (12), the number of corners of which complies with the number of the leaves of all iris diaphragms (5, 6), so that the leaves (9, 9′, 9″, 9′″, 9″″, 9′″″) allow for linear adjustment movements (13), the control mechanism being suitable to enable the irradiation of an irregular space through the overlaying and adjoining of many irradiated spaces (28).