Boron neutron capture therapy physics

4 problems

• Accelerator neutron sources meeting epithermal beam requirements

  Partially resolved

  Hospitals need compact accelerators that produce intense beams of medium-speed neutrons without too many fast neutrons or gamma rays. The targets that make the neutrons wear out quickly.

• Cellular-scale boron distribution in tumour and normal tissue

  Open

  The capture fragments travel only about a cell diameter, so the dose depends on whether the boron is inside each cell or outside it. Measurements of this in patients are lacking.

• Real-time imaging of boron concentration during irradiation

  Open

  Each boron capture emits a gamma ray of a specific energy, which could in principle be used to map the boron during treatment. A working scanner that does this accurately in a patient does not exist.

• Biological weighting of the neutron capture mixed field

  Contested

  The patient receives a mixture of $\alpha$ particles, lithium nuclei, protons from nitrogen, fast neutrons and $\gamma$ rays, each with a different biological effect. How to add them into one effective dose is disputed.