Small-scale dosimetry: challenges and future directions.

The increased specificity of targeting agents has resulted in an interest in the use of radionuclides that emit particulate radiation: alpha particles, beta particles and Auger electrons. The potential advantage of these radionuclides is the ability to deliver therapeutic doses to individual tumor cells while minimizing the dose to the surrounding normal tissues. However, the dosimetry of these radionuclides is challenging because the dose must be characterized on a scale that is comparable to the range of these emissions, ie, millimeters for beta particles, micrometers for alpha particles, and nanometers for Auger electrons to. In this review, each class of particulate emitter is discussed along with the associated dosimetric techniques unique to calculating dose on these scales. The limitations of these approaches and the factors that hinder the clinical use of small-scale dosimetry are also discussed.