Bridging Microdosimetry and Macrodosimetry: A Comparative Review of Computational Approaches

Microdosimetry does not simply refer to dosimetry with small targets, but rather to dosimetry that accounts for the stochastic nature of energy deposition.The International Commission on Radiation Units and Measurements has proposed using the probability densities of microdosimetric quantities such as lineal energy (y) and specific energy (z) to characterize the radiation fields instead of relying solely on linear energy transfer (LET) and absorbed dose.However, the practical application of microdosimetry remains limited due to significant computational costs associated with evaluating these stochastic quantities in macroscopic contexts such as the human body.To bridge the gap between microdosimetry and macrodosimetry, three approaches have been proposed and implemented: direct integration of track-structure and macroscopic radiation transport codes; integration of a database containing dose-mean values of microdosimetric quantities into macroscopic radiation transport codes; and integration of the analytical microdosimetric function for instantaneously calculating the probability densities of microdosimetric quantities within macroscopic radiation transport codes.This paper comprehensively reviews the conceptual and practical differences between LET and microdosimetric quantities, including their respective computational methodologies.The advantages and limitations of the three approaches are then discussed, followed by a summary of previous research efforts and suggestions for future research directions.