Figure 4. Cross-sectioned tumor surface (A) and fraction of vital tumor cells (B). (A) Cross-sectioned tumor surface was not significantly different both 5 and 12 days after radiation. (B) Although tumor cell density tended to decrease, there was no significant difference in the vital tumor cell fraction 5 days after radiation. However, radiation led to a significant decrease in the fraction of vital tumor cells 12 days after radiation. *Significant differences compared to nonradiated tumors; ▪, no radiation; □, radiation 15 Gy.