A time-resolved clonogenic assay for improved cell survival and RBE measurements

PurposeThe in vitro clonogenic assay (IVCA) is the mainstay of quantitative radiobiology. Here, we investigate benefit a time-resolved IVCA version (trIVCA) to improve quantification survival and relative biological effectiveness (RBE) by analyzing cell colony growth behavior.Materials & MethodsIn IVCA, clonogenicity classification colonies performed based on fixed size threshold after incubation. In contrast, using trIVCA, acquire time-lapse microscopy images during incubation track each neural-net-based image segmentation. Attributes resulting curves are then used as predictors for decision tree classifier determine colony.The method was applied three lines, irradiated with 250 kV X-rays range 0–8 Gy carbon ions high LET (100 keV/μm, dose-averaged) 0–2 Gy. We compared determined trIVCA those from classical across different thresholds times. Further, investigated impact assaying RBE determination.ResultsSize distributions abortive overlap consistently, rendering perfect separation via unfeasible at any readout time. This effect dose-dependent, systematically inflating steepness curvature curves. Consequently, estimates show variability between 3% 105%. uncertainty propagates into calculation 8% 25% 2 Gy.Determining has an accuracy 95% average.ConclusionThe suffers substantial caused delayed colonies. impairs precise RBE. By considering over time, our improves clonogenicity.