The Biodistribution (II): Human

Abstract

The measurement of the distribution and excretion of the radionuclide following the administration of a radiopharmaceutical is necessary in order to evaluate the consequential internal radiation dosimetry. This chapter reviews various in vivo and in vitro means of acquiring these data. The conjugate-view method used commonly in planar scintigraphy is derived and the various compensatory techniques to account for attenuation and photon scatter are derived and examined. Quantitative single-photon emission computed tomography (SPECT) which, due to current limitations in technology, is limited to absorbed dose evaluations of small anatomical volumes is reviewed as are the corrections required for scatter and attenuation. Positron emission tomography (PET) is inherently quantitative and its greater sensitivity compared to SPECT permits whole-body biodistributions of positron-emitting radionuclides to be measured. The principles of PET data acquisition are reviewed in the context of the nuclear medicine physicist designing a protocol for a whole-body biodistribution measurement. Finally, quantitative bremsstrahlung imaging of beta-emitting therapeutic radionuclides is a most challenging endeavor, and one which is not frequently performed. A review of the methodologies is provided.