AbstractID: 7493 Title: Dosimetry for a Monochromatic X-Ray Source, the CXS
Monochromatic x-rays with sufficient intensity for clinical use, today available only
at a handful of synchrotrons , have shown considerable promise for improved
radiotherapy both from better imaging and from the radiation dose enhancement
(RDE) from photoelectric absorption by x-ray contrast media (CM) in the tumor.
The development of the Compton X-Ray Source (CXS), that produces continuously
tunable monochromatic x-rays from 15 to 120 KeV by scattering sub-picosecond
photon pulses from 25 to 60 MeV electrons, may provide affordable monochromatic
x-rays for radiotherapy clinics.. A major problem for dosimetry is to estimate the
RDE from CT scans, since these cannot distinguish between concentrations of CM
confined to the extracellular fluid from those
in the tumor cells – an important
distinction because the photo electrons and Auger electrons have short ranges. To
provide the needed dosimetry we have estimated the RDE from the biological
response of cells suspended in CM and exposed to monochromatic and conventional
x-rays; we have calculated the RDE for a variety of CM as a function of photon
energy; we have measured the incorporation of various CM into cancer cells in
vitro, and we have measured the distribution of CM injected directly into mouse
tumors. The results indicate that the use of the CXS to treat various tumors following
their incorporation of CM will improve significantly the therapeutic ratio
obtainable with megavoltage therapy.