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SU‐FF‐T‐500: A Digital Monte Carlo Tumor Phantom to Study the Collective Cell Responses to Radiation Therapy
Author(s) -
Sheng K
Publication year - 2009
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 - 10.1118/1.3181998
Subject(s) - imaging phantom , monte carlo method , radiation therapy , tumor cells , nuclear medicine , physics , medicine , mathematics , statistics , cancer research , radiology
Purpose: To evaluate the response of a solid tumor to fractionated radiation therapy, a digital Monte Carlo tumor phantom is created to model the collective behavior of tumor cells based on their individual radiobiological characteristics. Methods and materials: Tumors with total number of 2×10 6 cells each were created as ones in two dimensional matrices. Varying tumor shapes were described by a geometrical factor defined as the ratio between the circumference and the area. Hypoxic tumor cells were defined as cells with a minimum cellular distance of 400 cells to the tumor surface. The digital tumors underwent regression with the fractionated radiation therapy. The viability of an individual tumor cells was determined by Monte Carlo simulation and its microenvironment. Hypoxic tumor cells were more radioresistive but did not proliferate. The treatment continued for different tumors until all cells were eliminated. Ten histories were run for each differently shaped tumor. Results: For a given shaped tumor, the logarithm survival followed the same slope for the first 15–17 fractions, where the survival started to separate, resulted in a relatively large statistical spread in the total number of fractions to sterilize the tumor among the 10 histories. For a round tumor, the number of fractions required to eliminate all cells ranged from 24 to 32, with an average of 26.3 and standard deviation of 2.71. The numbers needed to sterilize the tumor are nonlinearly decreased as the geometrical factor increased. Conclusions: A Monte Carlo tumor phantom was used to simulate collective biological responses to radiation therapy. Results indicate large statistic fluctuation in the total dose required to completely sterilize a solid tumor. It was also indicated that on average, tumors with higher surface to volume ratio require less radiation dose to kill.