Radiobiological Considerations for Pions in Radiotherapy

Abstract

A new radiation beam, the π – meson beam, is being considered for radiotherapy of human neoplasms. It is clear that this beam has special attributes which make it useful in certain types of neoplasms. However, human experience is heavily based upon low LET beams, alterations of dose rate and treatment, planning to confine dose to required therapeutic volumes. The use of this new beam must be considered upon existing knowledge regarding the natural history of the neoplasms, and the expected biological properties of the pion beam. It is likely that revision of present fractionation schedules will be required but most likely the pions will be useful to treat the residual tumor core of a tumor reduced in size by prior external beam, low LET therapy.

Californium Cf-252 for Pelvic Radiotherapy

“…43, 62] or particle beams. [23], hypoxic radiosensitisers and radioprotectors be investigated, it is also important that the real advantages, dosimetric and radio biological of Cf-252, also be capitalised upon for possible improvement of pelvic tumor therapy. For Curietherapy using Cf-252, the hazards involved in hand ling, and the protection necessary, require that the radioactive material be handled as rapidly as possible, with as few persons exposed to radiation as possible [80].…”

“…62, 69]. Most of them are available in only a few locations in the world and require advanced and sophisticated technology [23]. Of these, the most promising for study, with the potential of wide clinical applicability in man, are fast neutrons, since these are easily produced at clinically useful dose rates and can cover wide port sizes [12,43,62], However, still other forms of clinically useful fast neutron therapy are available, especially those emitted from the fast neutron emitting radionuclide Cf-252.…”

“…Because of our experience with implant time restrictions, it may be easier to combine external beam with sequential, mixed Cf-252/Cs-137 loadings to deliver dose equivalent to the above, instead of attempting to deliver the entire radiation dose by Cf-252 alone. We believe that the concept of "boost" dose advocated earlier [23] to approach idealised and individualised treatment for each patient [54] is an important one. The system can be accurately studied by radiography [78], monitors are available [27,53] and dosi metry is accurate [42].…”