In the context of radioimmunotherapy of cancer, there is a need for continued improvement of dosimetry of radionuclides localized in tumors. Current methods assume uniform distribution of radionuclides in the tumor despite experimental evidence indicating nonuniormity. We have developed a model in which nonuniform distribution of radioactivity in the tumor is taken into account. Spherically symmetric radionuclide distributions, depending linearly and exponentially on the radial position, are considered. Dose rate profiles in the tumor are calculated for potentially useful beta-emitting radionuclides, including 32P, 67Cu, 90Y, 111Ag, 131I, and 188Re, and for 193mPt, an emitter of conversion electrons and low-energy Auger electrons. For the radionuclide distributions investigated, high-energy beta emitters, such as 90Y, are most effective in treating large tumors (diameter, d greater than approximately 1 cm), whereas for small tumors (d approximately 1 mm), medium energy beta emitters such as 67Cu are better suited. Very small tumors (d less than 1 mm), and micrometastases are best handled with low-energy electron emitters such as 193mPt.

Antibodies, Monoclonal↗

PubMedDate not supplied

Radiation spectra for Auger-electron emitting radionuclides: report No. 2 of AAPM Nuclear Medicine Task Group No. 6.

Radiation spectra for radionuclides currently provided by the MIRD Committee and ICRP do not include the very low-energy N- and O-shell Auger electrons. These electrons, emitted in large numbers by radionuclides decaying by electron capture and/or internal conversion, are important for determining the absorbed dose in microscopic volumes. Accordingly, the present AAPM Report employs Monte Carlo computational methods to obtain a self-consistent set of complete radiation spectra for a variety of radionuclides including 55Fe, 67Ga, 99mTc, 111In, 113mIn, 115mIn, 123I, 125I, 193mPt, 195mPt, 201Tl, and 203Pb. Although the conventional spectra provided by MIRD and ICRP are adequate for most dosimetry calculations, the Auger electron spectra provided in this report are recommended for calculating the dose to target volumes < 1 microns in diameter.

Electrons↗