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SU‐FF‐T‐02: In Vitro Validation of Temporal Optimization Effects On Cell Survival for a Single Fraction of Radiation
Author(s) -
Altman M,
Stinauer M,
Chmura S,
Smith B,
Aydogan B,
Pelizzari C,
Roeske J
Publication year - 2007
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2760647
Subject(s) - clonogenic assay , irradiation , nuclear medicine , fraction (chemistry) , cell survival , in vitro , radiation therapy , dosimetry , andrology , biology , medicine , chemistry , physics , genetics , chromatography , nuclear physics
Purpose: To experimentally validate how temporal modification of the applied dose pattern within a single fraction of radiation therapy affects cell survival. Method and Materials: The linear quadratic (LQ) repair‐time model predicts that, for a single fraction of dose, the degree of cell kill is dependent on the pattern of dose applied over a period of irradiation. Previously, we demonstrated that: (1) maximum cell kill is achieved using a “triangular” temporal dose pattern (delivering the highest doses during the middle of a fraction and the lowest at the beginning and end), and (2) minimum cell kill is achieved with a “V‐shaped” pattern (delivering the lowest doses at the middle of a fraction and the highest at the beginning and end). Furthermore, the model also predicted that cells with low α/β values will have a larger difference in survival based on the applied pattern of dose. Two cells lines with low α/β values (PC‐3, WiDr) and one with a high α/β value (SQ‐20b) were chosen for this study. For each cell line, one group of cells in a six‐well plate received 9 Gy in a triangular dose pattern, and the same dose was delivered to a second plate using a V‐shaped pattern. The delivery time for each dose pattern was 20 min. Cell survival was assessed using a clonogenic assay. Results: For the SQ‐20b cells, irradiation with both dose patterns resulted in only a 4.5% relative difference in cell survival (p>0.25). However, the triangle and V‐shaped patterns resulted in relative cell survival differences of 15.2% and 18.6% for both the PC‐3 (p<0.025) and WiDr (p<0.01) cell lines, respectively. Conclusion: These results verify the assertions of the modeling study in vitro , and imply that the temporal pattern of applied dose is another variable to be considered in treatment planning and delivery.