Neutron Penetration During Neutron Capture Therapy

Neutron transport theory has been applied to the problem of penetration of a broad beam of neutrons into finite and semi-infinite volumes of aqueous media. The expressions derived are in excellent agreement with data obtained using a human head phantom of tissue equivalent gel. Epithermal neutrons proved to be much more penetrating than thermal neutrons and thus more advantageous for neutron capture therapy. The presence of 0·02% boron in the gel further increased the advantage of epithermal neutrons while diminishing their flux only slightly.