DaRT Source Spacing and Radon Diffusion for Prostate Tumors
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Solution Overview
Problem
Existing radiotherapy methods using alpha particles struggle to effectively target tumor cells while minimizing damage to healthy tissue due to the short range of alpha radiation and lack of practical methods to deploy alpha-emitting atoms uniformly throughout the tumor volume.
Innovation Solution
The use of diffusing alpha-emitter radiation therapy (DaRT) sources with tailored radon release rates and spacings, such as 1.5 to 3.2 microcurie per centimeter length and 3 to 4 millimeters spacing, to ensure adequate radiation coverage and minimize healthy tissue exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If alpha-emitting atoms are confined to the tumor volume, then surrounding healthy tissue is spared, but the short range of alpha particles limits their use in cancer therapy as there was no practical way to deploy alpha emitting atoms in sufficient concentrations throughout the entire tumor volume
Solution Approach 1:
The source is segmented into a parent component (radium-224 attached to the source) and daughter components (radon-220 and its daughters). The parent remains confined to the source to protect healthy tissue, while the gaseous daughters are released to distribute throughout the tumor volume, achieving both confinement and widespread distribution.
Solution Approach 2:
Radon-220 acts as an intermediary carrier. It is generated from radium-224 decay, escapes the source as a gas, diffuses through the tumor tissue, and delivers alpha radiation to distant tumor cells. This intermediary enables the transfer of radioactive material from the confined source to the broader tumor volume.
2Reliability
If DaRT seeds release a sufficient number of radon atoms to destroy the tumor with a high probability, then tumor destruction is achieved, but some daughter atoms are cleared from the tumor through the blood and could damage distant healthy tissue
Solution Approach 1:
The invention optimizes the radon release rate parameter to a specific range (1.5 to 3.2 microcurie per centimeter length) that balances two competing requirements: releasing enough radon to ensure tumor destruction while limiting the amount that could be cleared to distant organs. This parameter optimization resolves the contradiction between efficacy and safety.
3Area of stationary object
If the range of destruction in the tumor is increased by allowing radon atoms to leave the source, then alpha radiation can reach more tumor cells, but the ability to control where the radiation is delivered is reduced
Solution Approach 1:
Different components have different properties: radium-224 is confined to the source with fixed position, while radon-220 is released to diffuse locally throughout the tumor. This local quality differentiation allows the system to maintain control at the source while achieving widespread local destruction within the tumor boundaries.
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 approach effectively destroys tumor cells while reducing damage to surrounding healthy tissue by optimizing the distribution and dosage of alpha radiation, ensuring complete tumor destruction or reduction without exceeding safe radiation limits.
Implementation Method 1
radium-224 atoms, which generate chains of several radioactive decays with a governing half-life of 3.6 days
Implementation Method 2
These radionuclides, and their own radioactive daughter atoms, spread around the source by diffusion up to a radial distance of a few millimeters before they decay by alpha emission
Implementation Method 3
Alpha particles are a powerful means for radiotherapy since they induce clustered double-strand breaks on the DNA, which cells cannot repair
Data Source
AI summary
A method for treating a tumor, comprising identifying a tumor as a prostate cancer tumor and implanting in the tumor identified as a prostate cancer tumor, as least one diffusing alpha-emitter radiation therapy (DaRT) source (21) with a suitable radon release rate and for a given duration, such that the source (21) provides during the given duration a cumulated activity of released radon between 7 Mega becquerel (MBq) hour and 14.7 MBq hour, per centimeter length. Each DaRT source is separated from an adjacent DaRT source in the array by less than 3.9 millimeters.