Pencil Beam Spot Shaping for Sharp-Edge Radiotherapy Planning
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Solution Overview
Problem
Existing ion-based radiation therapy methods face challenges in achieving optimal dose distribution near the edges of the target volume, particularly in minimizing the penumbra and ensuring steep dose fall-off while using costly and impractical apertures or collimators that increase neutron background dose.
Innovation Solution
A computer-based method for generating a radiotherapy treatment plan that optimizes spot shape and orientation during pencil beam scanning, allowing variation in spot characteristics to improve target coverage and penumbra characteristics, using electromagnetic focusing systems or aperture devices to shape spots dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If spots are made small to achieve sharp dose fall-off near target edges, then penumbra is reduced and target coverage is improved, but the number of spots increases which extends delivery time
Solution Approach 1:
The patent changes the shape parameter of spots from uniform circular to variable elliptical shapes. By adjusting the elliptical shape parameters (aspect ratio, orientation, position) according to the local geometry of the target boundary, the system achieves sharp dose fall-off with fewer spots, thereby reducing delivery time while maintaining dosimetric precision.
Solution Approach 2:
The patent applies different spot shapes and orientations at different locations within the treatment field. Specifically, spots near the target boundary are shaped to match the local boundary geometry, while spots in the center maintain standard shapes. This local adaptation optimizes dose distribution precision without unnecessarily increasing the total number of spots.
2Manufacturing precision
If static apertures are used to improve dose distribution near target edges, then penumbra is reduced, but manufacturing cost increases and neutron background dose is produced
Solution Approach 1:
The patent replaces the mechanical aperture system with an electromagnetic beam shaping system. By using electromagnetic fields to dynamically shape and position the particle beams, the system achieves precise dose distribution without physical apertures, thereby eliminating neutron production from aperture interactions while maintaining dosimetric precision.
3Manufacturing precision
If MLC is used to dynamically adjust spot shape, then dose distribution precision is improved, but device cost increases
Solution Approach 1:
The patent replaces the MLC mechanical collimating system with an electromagnetic beam shaping system. The electromagnetic system uses magnetic or electric fields to dynamically control spot shape and position without physical moving parts, achieving the same dosimetric precision while avoiding the high cost and complexity of MLC mechanisms.
Solution Approach 2:
The patent implements dynamic spot shaping through electromagnetic field modulation. The spot shape, size, and position are adjusted in real-time by changing electromagnetic field parameters, providing the same flexibility as MLC but without the mechanical complexity and cost of moving collimator leaves.
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
Enhances target coverage and reduces penumbra by dynamically varying spot shapes and orientations, minimizing neutron dose and optimizing delivery efficiency, particularly beneficial for pediatric applications.
Implementation Method 1
using electromagnetic focusing systems or aperture devices to shape spots dynamically
Data Source
Figure 1~4
AI summary
A method of optimizing a radiotherapy treatment plan for delivering charged particles to a patient by pencil beam scanning, involves optimizing the treatment plan using an optimization problem that is designed to allow spots to differ in at least one of shape and orientation, and optionally also in size. This enables the optimization spots so as to cover the target in the best possible way and with a sharp penumbra along the outer edges of the target. The invention also relates to a computer program product and a computer system for use in such planning and a treatment delivery system for delivering such a plan.