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Tumor dosimetry in radioimmunotherapy: Methods of calculation for beta particles
Author(s) -
Leichner Peter K.,
Kwok Cheuk S.
Publication year - 1993
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.597048
Subject(s) - dosimetry , absorbed dose , radioimmunotherapy , monte carlo method , nuclear medicine , radionuclide therapy , medical physics , physics , computational physics , medicine , mathematics , statistics , antibody , immunology , monoclonal antibody
Calculational methods of beta‐particle dosimetry in radioimmunotherapy (RIT) are reviewed for clinical and experimental studies and computer modeling of tumors. In clinical studies, absorbed‐dose estimates are usually based on the in ‐ vivo quantitation of the activity in tumors from gamma camera images. Because of the limited spatial resolution of gamma cameras, clinical dosimetry is necessarily limited to the macroscopic level (macrodosimetry) and the MIRD formalism for absorbed‐dose calculations is appropriate. In experimental RIT, tumor dimensions are often comparable to or smaller than the beta‐particle range of commonly used radionuclides (for example, 131 I, 67 Cu, 186 Re, 188 Re, 90 Y) and deviations from the equilibrium dose must be taken into account in absorbed‐dose calculations. Additionally, if small tumors are growing rapidly at the time of RIT, the effects of tumor growth will need to be included in absorbed‐dose estimates. In computer modeling of absorbed‐dose distributions, analytical, numerical, and Monte Carlo methods have been used to investigate the consequences of uniform and nonuniform activity distributions and the effects of inhomogeneous media. Measurements and calculations of the local absorbed dose at the multicellular level have shown that variations in this dose are large. Knowledge of the absorbed dose is essential for any form of radiotherapy. Therefore, it is important that clinical, experimental, and theoretical investigations continue to provide information on tumor dosimetry that is necessary for a better understanding of the radiobiological effects of RIT.