(a) Tumor explants following 4, 24, or 72 h after intraperitoneal injection of either Av-Cy5.5, Av-Alexa 680, or Av-SiR700 were used to semi-quantitatively compare fluorescence intensity of each NIR imaging probe. ROIs were drawn around each tumor and average fluorescence intensity was calculated. Then, values were calculated and graphed relative to the 4 h time point. The graph demonstrating the decrease in signal for each NIR imaging probe over time is shown (b). Av-Alexa 680 demonstrates rapid decrease in fluorescence intensity with a significantly greater decrease in fluorescence intensity at 72 h than Av-Cy5.5 and Av-SiR700 with p values <0.001 and <0.01, respectively. Av-Cy5.5 demonstrates a relative increase in fluorescent intensity from 4 to 24 h but then shows a rapid decrease in fluorescence intensity. There was no significant difference in decrease in fluorescence intensity over time between Av-Cy5.5 and Av-SiR700.