DaRT Source Radon Diffusion for Tumor Coverage
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Solution Overview
Problem
Current radiotherapy methods using ionizing radiation face challenges in delivering targeted doses to tumors while minimizing damage to healthy tissues, particularly due to the limited range of alpha particles and the lack of effective deployment methods for alpha-emitting atoms throughout the tumor volume.
Innovation Solution
The development of diffusing alpha-emitter radiation therapy (DaRT) sources with radium-223 or radium-224 atoms, which are implanted in tumors to release radon daughters that diffuse and emit alpha particles, increasing the therapeutic range while minimizing exposure to healthy tissues by controlling the radon release rate and spacing of sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If alpha-emitting atoms are confined to the tumor volume, then healthy tissue is spared from radiation damage, but the short range of alpha particles limits their use in cancer therapy
Solution Approach 1:
The source is segmented into two functional components: radium atoms attached to the source structure that remain confined, and radon daughter atoms that are released to diffuse into the tumor. This segmentation allows the parent atoms to stay localized while the daughter atoms extend the therapeutic range.
Solution Approach 2:
Radon daughter atoms serve as intermediaries that transfer the radiation effect from the confined radium source to the broader tumor volume. The radon atoms diffuse away from the source and deliver alpha radiation to distant tumor cells, acting as a mediator between the source and target.
2Reliability
If DaRT seeds release a sufficient number of radon atoms to destroy the tumor with high probability, then tumor destruction is achieved, but some daughter atoms are cleared from the tumor through blood and could damage distant healthy tissue
Solution Approach 1:
The source activity is precisely controlled within specific ranges (1-10 μCi for radium-223, 10-100 μCi for radium-224) to optimize the balance between tumor destruction and systemic exposure. The radon release rate is adjusted by controlling the radium activity parameter.
Solution Approach 2:
The source releases more radon atoms than minimally required for tumor destruction, accepting that some will be cleared systemically. This partial excess ensures sufficient tumor coverage while the released amount is controlled to minimize systemic damage.
3Stability of the object's composition
If radium atoms are attached to the source with sufficient strength to prevent clearance, then radium remains localized, but a substantial percentage of daughter radionuclides must leave the source to achieve therapeutic effect
Solution Approach 1:
The radon daughter atoms are extracted from the source structure through the recoil effect during alpha decay. This extraction is intentional and controlled, allowing radon to leave the source while radium remains attached, separating the retention function from the release function.
Solution Approach 2:
The source structure dynamics change during operation: radium atoms remain statically attached to the source, while radon atoms are dynamically released through recoil and diffusion. This dynamic behavior enables simultaneous stability and release.
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 allows for accurately tailored radiation delivery to tumors, enhancing the effectiveness of cancer treatment by increasing the tumor's radiation dose while minimizing exposure to healthy tissues, thereby improving treatment outcomes and reducing side effects.
Implementation Method 1
radium-223 or radium-224 atoms, which generate chains of several radioactive decays with a governing half-life of 3.6 days for radium-224 and 11.4 days for radium-223
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 cancerous tumor, by implanting in the cancerous tumor at least one diffusing alpha-emitter radiation therapy (DaRT) source with a suitable radon release rate and for a given duration, such that the source provides during the given duration a cumulated activity of released radon of at least 10 Mega becquerel (MBq) hour, per centimeter length. Optionally, the sources are implanted in an array of sources, each source separated from its neighboring sources in the array by not more than 4.5 millimeters.