Neutron Source Beam Shaping for BNCT
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Solution Overview
Problem
Current neutron generators for Boron Neutron Cancer Therapy (BNCT) face challenges in producing a focused beam of thermal neutrons for effective tumor treatment, as they often result in isotropic emission, contamination with gamma and higher energy neutrons, and reduced thermal neutron flux, making it difficult to achieve directional, high-density neutron delivery to tumor sites.
Innovation Solution
A modular, compact Low-Voltage Fusion neutron generator (LVFG) integrated with a beam-shaping apparatus (BSA) that includes a conically shaped element and materials like bismuth and sapphire to collimate and focus thermal neutrons, ensuring a small source size and high neutron brightness, thereby enhancing neutron delivery to specific tumor sites.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional neutron generators are used for BNCT, then neutron production is achieved, but the emission is isotropic and not directional, making it difficult to focus the beam on tumor sites
Solution Approach 1:
The beam shaping apparatus is divided into multiple functional segments: a collimator section with parallel walls to define beam direction, a moderating section with hydrogen-rich materials to thermalize neutrons, and a filtering section to remove unwanted radiation components. Each segment performs a specific function to progressively shape the neutron beam for directional delivery to tumor sites.
Solution Approach 2:
The patent introduces intermediary components between the neutron source and the patient, including a collimator as an intermediary to define beam geometry, moderating materials as intermediaries to convert fast neutrons to thermal neutrons, and filtering materials as intermediaries to remove gamma and fast neutron contamination. These intermediaries transform the isotropic emission into a focused thermal neutron beam.
2Quantity of substance
If moderators are used to thermalize neutrons, then thermal neutron flux is produced, but gamma and higher energy neutrons contaminate the beam
Solution Approach 1:
The patent extracts harmful radiation components from the neutron beam through dedicated filtering sections. Lead or deuterated polyethylene filters are positioned after the moderating section to selectively absorb gamma rays and fast neutrons while allowing thermal neutrons to pass through, thereby separating the desired thermal neutron flux from unwanted contamination.
Solution Approach 2:
The patent utilizes parameter changes in material properties at different beam positions. The collimator uses high-Z materials to define geometry, the moderator uses hydrogen-rich materials to thermalize neutrons, and the filter uses lead or deuterated polyethylene to absorb specific energy ranges. Each section is optimized for its specific function by selecting materials with appropriate nuclear and physical parameters.
3Quantity of substance
If the neutron beam is focused to increase flux density, then tumor treatment effectiveness is improved, but the source size increases
Solution Approach 1:
The patent achieves flux concentration by transitioning from a three-dimensional isotropic emission to a one-dimensional directional beam through the collimator. The parallel-walled collimator geometry transforms the spatial distribution of neutrons, confining them to a narrow angular range and effectively concentrating the flux density along the beam axis without significantly increasing the physical source dimensions.
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 solution enables precise and effective delivery of thermal neutrons to tumor sites, reducing damage to healthy tissues and improving treatment outcomes by increasing neutron flux and resolution, while minimizing unwanted radiation components.
Implementation Method 1
the neutrons are slowed by collisions and become low energy thermal neutrons
Implementation Method 2
an elongated beam-shaping apparatus (BSA) having a length and a circular cross section of a diameter less than the length, the BSA joined at one end to and projecting orthogonally from the surface of the moderator block
Implementation Method 3
the BSA having a conically shaped element at an end away from the moderator block, the conically shaped element declining in diameter in a direction away from the moderator block
Implementation Method 4
A modular, compact Low-Voltage Fusion neutron generator (LVFG)
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A cancer treatment apparatus has a neutron source generating neutrons exiting through a surface of a moderator block and an elongated beam-shaping apparatus (BSA) having a length and a circular cross section of a diameter less than the length, the BSA joined at one end to and projecting orthogonally from the surface of the moderator block of the neutron source, the BSA having a conically shaped element at an end away from the moderator block, the conically shaped element declining in diameter in a direction away from the moderator block. Neutrons produced by the neutron source enter the BSA at the surface of the moderator block, travel the length of the BSA, and exit the BSA through an aperture at the end of the BSA away from the moderator block.