Smith’s “Internal Dose Calculation for ^99mTc”: An Excellent Paper with Approximate Methods (perspective on “Internal Dose Calculation for ^99mTc” J Nucl Med. 1965;6:231–251)

Abstract

The internal dosimetry of -and -emitters has been established by several authors. Smith (1) cites the work of Loevinger et al.(2) and Ellett et al. (3), pioneers in the fi eld. Somehow, internal dosimetry manages to intimidate many, when, as shown by Smith, it is just energy per unit mass, as is external dosimetry. The diffi culty arises from the calculation of the absorbed fraction of energy from a source region to itself or to a different target. For particulate radiation, the energy per emission and its abundance are suffi cient, as we assume that all energy emitted in a source is absorbed there (a generally good assumption), but for photons, more work is needed. Smith, like Marinelli, Quimby, and others (4,5), used reasonable approximations. In 1965, we did not have the elaborate Monte Carlo methods that were developed later by Cristy and Eckerman (6), among others. These approximations were wonderful at the time and were shown by more exact computer methods to be quite reasonable. All of the unit conversions were, of course, absolute. The ''remainder of the body'' method developed by Cloutier et al. ( 7) was not available, but notice the agreement between Smith's fi nal answers and those of the latest methods, using highly sophisticated anthropomorphic phantoms and the best kinetic data (Table 1).