Nanoparticle enhancement in proton and carbon-ion beams
In plain words
Gold adds little extra absorbed dose in proton beams, since protons interact with electrons in almost the same way regardless of the element. Some experiments still report enhanced killing, others report none.
Precise statement
Determine whether high-Z nanoparticles at clinically achievable concentrations (below about 1 mg per g of tissue) increase cell killing in proton beams of 10 to 200 MeV and carbon-ion beams of 50 to 400 MeV per nucleon beyond the computed dose increase, which is of order 0.1 percent. An answer is yes or no with a measured enhancement ratio and its uncertainty under controlled particle uptake, plus the physical or chemical channel responsible if yes.
What would settle it
Blinded multi-laboratory cell-survival measurements with quantified intracellular gold content in identical proton and ion beams, with matched controls.
Status in the literature
Positive and null results coexist in the literature and the effect has not been reproduced under a common protocol.