Sci‐Thur AM: YIS – 06: A Monte Carlo study of macro‐ and microscopic dose descriptors and the microdosimetric spread using detailed cellular models

Abstract

Purpose:To develop Monte Carlo models of cell clusters to investigate the relationships between macro‐ and microscopic dose descriptors, quantify the microdosimetric spread in energy deposition for subcellular targets, and determine how these results depend on the computational model.Methods:Microscopic tissue structure is modelled as clusters of 13 to 150 cells, with cell (nuclear) radii between 5 and 10 microns (2 and 9 microns). Energy imparted per unit mass (specific energy or dose) is scored in the nucleus (Dnuc) and cytoplasm (Dcyt) for incident photon energies from 20 to 370 keV. Dose‐to‐water (Dw,m) and dose‐to‐medium (Dm,m) are compared to Dnuc and Dcyt. Single cells and single nuclear cavities are also simulated.Results:Dnuc and Dcyt are sensitive to the surrounding environment with deviations of up to 13% for a single nucleus/cell compared with a multicellular cluster. These dose descriptors vary with cell and nucleus size by up to 10%. Dnuc and Dcyt differ from Dw,m and Dm,m by up to 32%. The microdosimetric spread is sensitive to whether cells are arranged randomly or in a hexagonal lattice, and whether subcellular compartment sizes are sampled from a normal distribution or are constant throughout the cluster.Conclusions:Dnuc and Dcyt are sensitive to cell morphology, elemental composition and the presence of surrounding cells. The microdosimetric spread was investigated using realistic elemental compositions for the nucleus and cytoplasm, and depends strongly on subcellular compartment size, source energy and dose.