Layered X-Ray Target for UHDR Radiotherapy Heat Management

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Solution Overview

Problem

Conventional X-ray targets are not suitable for the high beam currents and instantaneous dose rates characteristic of ultra-high dose rate (UHDR) radiotherapy, leading to deterioration and potential destruction.

Innovation Solution

A radiotherapy system with an X-ray target comprising a plurality of target layers, each configured to convert a portion of the electron beam into an X-ray beam, where the diameter of each layer corresponds to the beam spot size, and includes refractory metals like tungsten or tantalum, with heat transfer materials and cooling apparatuses to manage heat and maintain stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If conventional X-ray targets are used to convert electron beam into X-ray beam at ultra-high dose rates, then X-ray production efficiency is improved, but target durability and stability deteriorate due to high beam currents and instantaneous dose rates

Engineering Contradiction:
ImproveX-ray production efficiencyVSAvoidtarget durability
Core Design Contradiction:
ProductivityVSReliability

Solution Approach 1:

The target is divided into multiple thin target layers (e.g., 5-10 layers) stacked in series, where each layer converts a portion of the electron beam into X-rays. This segmentation distributes the high beam current load across multiple layers, preventing any single layer from overheating or deteriorating under ultra-high dose rate conditions while maintaining overall X-ray production efficiency.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The invention transitions from a conventional single-layer or thick-target approach to a multi-layer stacked configuration along the electron beam propagation direction. This dimensional arrangement allows the electron beam to progressively interact with multiple layers, distributing energy deposition in the longitudinal dimension and improving target stability under high current conditions.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

2Manufacturing precision

If the diameter of target layers is reduced to match beam spot size, then X-ray beam quality and precision are improved, but heat dissipation capability deteriorates

Engineering Contradiction:
Improvebeam spot size matchingVSAvoidheat dissipation
Core Design Contradiction:
Manufacturing precisionVSTemperature

Solution Approach 1:

By segmenting the target into multiple thin layers with diameters matched to the beam spot size, the heat load is distributed across multiple layers rather than concentrated in a single large target. Each layer handles a fraction of the total heat generation, and the stacked configuration allows heat to be managed in both radial and longitudinal directions, improving overall heat dissipation while maintaining precise beam spot matching.

Inventive Principle:
Principle #1Segmentation

3Reliability

If multiple target layers are stacked in series to handle high currents, then target stability is improved, but device complexity increases

Engineering Contradiction:
Improvetarget stabilityVSAvoidnumber of target layers
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The target system is segmented into multiple identical or similar thin layers stacked in series, which can be manufactured using the same process and assembled in a modular fashion. This standardization of the segmented units reduces the complexity of manufacturing and assembly compared to designing a single complex thick target, while still achieving the stability benefits of multiple layers.

Inventive Principle:
Principle #1Segmentation

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

The system effectively absorbs >99% of incident electrons, operates at UHDR rates of at least 1 Gray per second, and maintains target stability by managing heat through layered design and cooling, ensuring reliable X-ray production.

Implementation Method 1

an X-ray target configured to convert an electron beam into an X-ray beam, the X-ray target including, a plurality of target layers, each of the plurality of target layers configured to convert a portion of the electron beam into a portion of the X-ray beam

Methodology Applied
Scientific EffectBremsstrahlung radiation:

Implementation Method 2

the radiotherapy system further comprises a heat transfer material between at least two target layers of the X-ray target. Preferably, the heat transfer material has a high thermal conductivity

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentEP4548967B1High dose rate radiotherapy systems and targets
Publication Date: 2026.04.01 VARIAN MEDICAL SYSTEMS INC
  • EP4548967B1 patent drawingFigure 1
  • EP4548967B1 patent drawingFigure 2
  • EP4548967B1 patent drawingFigure 3A

AI summary

A radiation system includes an X-ray target configured to convert an electron beam into an X-ray beam. The X-ray target includes a plurality of target layers and each of the plurality of target layers are configured to convert a portion of the electron beam into a portion of the X-ray beam.