IMPLEMENTATION OF A MONTE-CARLO DOSIMETRY METHOD FOR PATIENT-SPECIFICINTERNAL EMITTER THERAPY

In internal emitter therapy, an accurate description of the absorbed d ose distribution is necessary to establish an administered dose-respon se relationship, as well as to avoid critical organ toxicity. This wor k describes the implementation of a dosimetry method that accounts for the radionuclide decay spectrum, and patient-specific activity and de nsity distributions. The dosimetry algorithm is based on a Monte Carlo procedure that simulates photon and electron transport and scores ene rgy depositions within the patient. The necessary input information ma y be obtained from a registered set of CT and SPECT or PET images. The algorithm provides the absorbed dose rate for the radioactivity distr ibution provided by the SPECT or PET image. The algorithm was benchmar ked by reproducing dosimetric quantities using the Medical Internal Ra dionuclide Close (MIRD) Committee's Standard Man phantom and was used to calculate absorbed dose distributions for representative case studi es. (C) 1997 American Association of Physicists in Medicine.