Volume 16, Issue 1 p. 66-74

Macroscopic dosimetry for radioimmunotherapy: Nonuniform activity distributions in solid tumors

Roger W. Howell

Roger W. Howell

Department of Radiology, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103

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Dandamudi V. Rao

Dandamudi V. Rao

Department of Radiology, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103

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Kandula S. R. Sastry

Kandula S. R. Sastry

Department of Physics and Astronomy, University of Massachusetts, Amherst, Massachusetts 01003

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First published: January 1989
Citations: 99

Abstract

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 nonuniformity. 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≳1 cm), whereas for small tumors (d∼1 mm), medium energy beta emitters such as 67Cu are better suited. Very small tumors (d<1 mm), and micrometastases are best handled with low-energy electron emitters such as 193mPt.