Dual-Mode Radiotherapy Source for Beams-Eye-View Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current radiotherapy apparatuses face challenges in achieving high contrast and low patient dose imaging due to the limitations of using high-energy therapeutic beams for diagnostic purposes, with existing solutions either being costly, complex, or not capable of easily switching between therapeutic and diagnostic modes.
Innovation Solution
A radiation source is developed using a thin electron/vacuum window as an X-ray transmission target combined with an electron beam absorber of lower atomic number, allowing for the production of bremsstrahlung radiation suitable for imaging, and incorporating a diagnostic filter to reduce skin dose, enabling a practical and safe 'beams-eye-view' imaging capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate kV x-ray source is added for investigative purposes, then image contrast and detection efficiency are improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the therapeutic MV x-ray source perform both therapeutic and investigative functions by enabling it to operate in two modes: producing high-energy MV beams for treatment and low-energy kV beams for imaging. This eliminates the need for a separate kV source while maintaining high image contrast through photoelectric effect dominance at lower energies.
Solution Approach 2:
The patent changes the energy parameter of the x-ray beam by adjusting electron beam energy and target material properties. By operating the electron accelerator at lower energies (kV range) instead of therapeutic energies (MV range), the system produces beams with attenuation coefficients that provide high bone-tissue contrast while reducing patient dose.
2Measurement precision
If a separate kV x-ray source is added for investigative purposes, then detection efficiency is improved, but cost increases
Solution Approach 1:
The existing MV x-ray source is made multi-functional by implementing a dual-mode operation capability. The same electron accelerator and target assembly can produce both therapeutic MV beams and investigative kV beams, eliminating the need for additional expensive equipment while maintaining high detection efficiency through optimized low-energy beam production.
3Adaptability or versatility
If the therapeutic source is rotated around the patient, then treatment coverage is improved, but alignment maintenance between therapeutic and diagnostic axes becomes difficult
Solution Approach 1:
By making the single x-ray source dual-functional, the patent eliminates the need for separate therapeutic and diagnostic beam axes. The same source rotates around the patient to provide both treatment and imaging from identical geometric positions, automatically maintaining alignment without requiring separate axis coordination or additional alignment mechanisms.
4Power
If high-energy MV beam is used for imaging, then therapeutic treatment is effective, but image contrast is poor and patient dose is high
Solution Approach 1:
The patent changes the beam energy parameter from MV range to kV range for imaging applications. This parameter change fundamentally alters the interaction mechanisms: at kV energies, photoelectric effect dominates providing strong Z-dependence and high bone-tissue contrast, while at MV energies, Compton scattering dominates providing poor contrast but effective therapeutic penetration.
Solution Approach 2:
The system dynamically adjusts its operating mode based on the required function. The electron accelerator can switch between producing high-energy MV beams for therapy and low-energy kV beams for imaging, with the beam characteristics being dynamically controlled by adjusting electron energy and target interaction conditions to optimize for either therapeutic effectiveness or imaging contrast.
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 solution provides high contrast images with significantly lower patient dose, improving imaging accuracy and reducing treatment time while maintaining the therapeutic beam's effectiveness, offering a cost-effective and simpler modification to existing linac systems.
Implementation Method 1
the electron beam will interact with the electron window to produce bremsstrahlung radiation which he was able to use for imaging
Implementation Method 2
The lower atomic number electron beam absorber serves to remove the residual electrons transmitted through the vacuum window
Implementation Method 3
a diagnostic filter can be included to reduce the skin dose by removing X-rays of energy approximately < 30 keV
Implementation Method 4
The electron window transmits a large proportion of the electron beam but is of a sufficient thickness that on average a relatively small proportion of the electrons energy is deposited and converted to useful bremsstrahlung radiation suitable for imaging applications
Data Source
AI summary
It is desirable to achieve a co-incident investigative kV source for a therapeutic MV source - a so-called "beams-eye-view" source. It has been suggested that bremsstrahlung radiation from an electron window be employed; we propose a practical structure for achieving this which can switch easily between a therapeutic beam and a beam-eye-view diagnostic beam capable of offering good image resolution. Such a radiation source comprises an electron gun, a pair of targets locateable in the path of a beam produced by the electron gun, one target of the pair being of a material with a lower atomic number than the other, and an electron absorber insertable into and withdrawable from the path of the beam. In a preferred form, the electron gun is within a vacuum chamber, and the pair of targets are located at a boundary of the vacuum chamber. The lower atomic number target can be Nickel and the higher atomic number target Copper and/or Tungsten. The electron absorber can be Carbon, and can be located within the primary collimator, or within one of a plurality of primary collimators interchangeably locateable in the path of the beam. Such a radiation source can be included within a radiotherapy apparatus, to which the present invention further relates. A flat panel imaging device for this source can be optimised for low energy x-rays rather than high energy; Caesium Iodide-based panels are therefore suitable.