MIRD Pamphlet No. 25: MIRDcell V2.0 Software Tool for Dosimetric Analysis of Biologic Response of Multicellular Populations

Screenshot of “Cell Source/Target” tab. Source region (red) in cell that contains radiopharmaceutical can be selected as cell, cell surface, nucleus, or cytoplasm (top left). Selectable target regions (blue) include cell, nucleus, or cytoplasm (top left). Cell and cell nucleus are represented by concentric shells of unit density water with cell radius (R_C) and cell nucleus radius (R_N), which can be set as desired (bottom left).

Screenshot of “Multicellular Geometry < 1-D Cell Pair.” This subtab enables rapid calculation of self-dose to labeled cell and cross-dose to neighboring cell that lies at some distance (i.e., 16 μm between centers in this example). Self- and cross-doses per unit cumulated activity in source cell (Gy Bq⁻¹ s⁻¹), also known as S value (2,35), are reported for selected source radiation (i.e., ⁹⁰Y in this example) in box labeled “Result.” Calculation can be repeated for different cell separation distances (top left).

Screenshots of “Multicellular Geometry < 2-D Colony < 2-D Colony.” (A) Here, user can select multicellular geometry wherein cell population lies on plane. In “Cell Geometry” box, cell population can be constrained to different selectable shapes including circle (shown), ellipse, and rectangle (top left). Dimensions of each shape are provided by user (i.e., circle with 66-μm radius in this example). In “Cell Labeling” box, activity can be distributed among cell population according to selectable labeling methods: uniform (shown), normal, and lognormal. Mean activity per cell, residence time, and percentage of cells that are labeled can be specified. On selecting parameters and clicking “Compute,” resulting multicellular geometry is plotted on right in a manner that indicates whether cell is labeled (red) or unlabeled (green), and transparency represents whether cell is dead (transparent) or alive (opaque). (B) Histogram of activity per cell. This example shows uniform distribution of activity among labeled cells (each labeled cell has same activity). (C) Plot of surviving fraction of cells.

Screenshot of “Multicellular Geometry < 3-D Cluster < 3-D Cluster.” (A) User can select multicellular geometry wherein cell population is contained within 3-D geometry. In “Cell Geometry” box, cell population can be constrained to different selectable shapes including sphere (shown), ellipsoid, and cone. Dimensions of each shape are provided by user (i.e., sphere with 65-μm radius in this example). In “Cell Labeling” box, activity can be distributed among cell population according to selectable labeling distributions: uniform, normal, and lognormal (shown). Mean activity per cell, residence time, and percentage of cells that are labeled can be specified. When parameters are selected and “Compute” is clicked, the resulting multicellular geometry is plotted on right in a manner that indicates whether cell is labeled (red) or unlabeled (green), and transparency represents whether cell is dead (transparent) or alive (opaque). (B) Histogram of activity per cell. Small number of labeled cells (in this case it is 172) magnifies stochastic aspects of distribution in such a small population. Repeated clicking of “Compute” tab shows variations in distribution when Monte Carlo calculations are repeated. (C) Plot of surviving fraction of cells.

Examples of additional geometries available in “Multicellular Geometry < 3-D Cluster < 3-D Cluster.” These are 3-D cluster shapes with 50% of cells labeled. Cluster shapes are sphere, rod, cone, and ellipsoid. Cells are labeled (red) or unlabeled (green), and transparency represents whether cell is dead (transparent) or alive (opaque).